A different view on battery charging?

I know this has been done to death and I've read with interest the differing views on differring systems for charging aux batteries in 4x4's and campers.
Over the years I've had the Redarc solonoid version and Rotronics in different vehicles, both worked well although I replaced less batteries with the rotronics.
We are currently setting up a GU for some extended outback touring. The car has a Redarc and 2 dissimilar "deep cycle" batteries, one under the bonnet and one in the trailer.
I intend to install 2 AGM 90-100AH batteries parralled togther, as aux, one under bonnet and the other in the back of the wagon to run a fridge and the various bits we (she) can't do without.

MY QUESTION...

As we have a 600 watt inverter in the GU, would it make sense to run a 240volt, 30amp, 3 stage smart charger off the inverter to charge the 2 aux batteries while travelling?
I know there would be some loss of efficiency, but figure the alternator could handle those losses.
My idea was to also have some heavy cables joining joining the main(cranker) to the aux under the bonnet with a manual on/off swith inline in case the inverter or charger failed?
My thoughts are that the batteries would be charged completely(3 stage charger) and quickly (AGM) with enough reserve capacity for a few nights here and there.
I also already have most of the components so cost would be minimal.

Thanks for your patience!

What do you think???

Cheers Nifty.
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Reply By: Robin Miller - Monday, Feb 25, 2008 at 10:52

Monday, Feb 25, 2008 at 10:52
Hi Nifty

That will work.

Bit messy though , not keen on stepping up to 240v just so one can step down.

Sometimes you get a bit of radio interference also.

If cost was no object I'd use one of the commercial 12v step up chargers, which would be more likely to survive and be less trouble.
Robin Miller

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AnswerID: 289273

Reply By: Notso - Monday, Feb 25, 2008 at 12:01

Monday, Feb 25, 2008 at 12:01
Something like this is worth looking at

http://www.12volt.com.au/redirect.html?a=/General%20Htmls/webcat2003/batterysystems.html
AnswerID: 289283

Follow Up By: downtools - Monday, Feb 25, 2008 at 12:14

Monday, Feb 25, 2008 at 12:14
Thanks Notso,
I called these guys today and they were less than helpfull.
When I mentioned AGM batteries they said it was a bad idea, an Arrid Twin charge wouldn't work with my setup and they couldn't help.
Thanks anyway, will keep investigating.
Cheers Nifty.

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FollowupID: 554583

Follow Up By: Member - Roachie (SA) - Tuesday, Feb 26, 2008 at 14:45

Tuesday, Feb 26, 2008 at 14:45
Funny that!!!

I have an Arrid Twin charger that pumps juice into my Fullriver HGL 120-12 AGM battery VERY successfully.

I also have a digital voltmeter in the cab (good for 2 decimal points) which I can switch between the main 2 batteries or the AGM. Invariably, the AGM shows about 0.2v higher than the other 2 batteries combined, which are being charged by the alternator! (eg: main batteries will be showing 13.97v and when I switch the meter over to the AGM it's shows around 14.15v).

Cheers

Roachie
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FollowupID: 554775

Follow Up By: Mainey (wa) - Tuesday, Feb 26, 2008 at 15:40

Tuesday, Feb 26, 2008 at 15:40
Possibly can be explained because the AGM has a much LOWER internal resistance than wetcel batteries, hence they charge so much faster and more fully also.

I would have thought the Arrid Twin charger may have put out a bit more than your stated ~0.2v difference (13.97v - 14.15v)

Mainey . . .
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FollowupID: 554785

Reply By: feral - Monday, Feb 25, 2008 at 12:30

Monday, Feb 25, 2008 at 12:30
Just do it Nifty.

This concept has taken the caravan industry and everyone who knows what they are doing, are doing it!!
Why? Because it ensures that you will have a fully 100% charged battery by the end of the day.

The only concern is that the 30amps maybe too high a charge rate for your batteries.

I'll go and put the popcorn on.
AnswerID: 289287

Reply By: Mainey (wa) - Monday, Feb 25, 2008 at 15:14

Monday, Feb 25, 2008 at 15:14
"""As we have a 600 watt inverter, would it make sense to run a 240volt, 30amp, 3 stage smart charger off the inverter to charge the 2 aux batteries WHILE TRAVELLING. I know there would be some loss of efficiency.... ?"""

In a one word reply... no

WHILE TRAVELLING your alternator will (fully) recharge the AGM's !!

Mainey . . .
AnswerID: 289303

Follow Up By: GaryInOz (Vic) - Monday, Feb 25, 2008 at 16:16

Monday, Feb 25, 2008 at 16:16
....also VERY serious safety concerns in the event of an accident (240 volts at road level and earthed to the vehicle chassis)

GOD HELP THE RESCUE CREWS TRYING TO SAVE YOU.

DON'T DO IT!!!!!
DON'T DO IT!!!!!
DON'T DO IT!!!!!

Contact the DOT in your state to see how ILLEGAL this idea is!

Are you getting the drift????
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FollowupID: 554597

Follow Up By: downtools - Monday, Feb 25, 2008 at 17:17

Monday, Feb 25, 2008 at 17:17
G inOz,
Good point, not really sure of the safety aspects.
Have decided to keep all charging and battery things 12 volt.
I like to keep things simple, like me!
Will go with AGM's for the faster recharge.
Cheers Nifty.
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FollowupID: 554601

Follow Up By: Mike Harding - Monday, Feb 25, 2008 at 17:37

Monday, Feb 25, 2008 at 17:37
If it's an isolated inverter there is no significant safety issue.

Mike Harding
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FollowupID: 554606

Follow Up By: feral - Monday, Feb 25, 2008 at 18:03

Monday, Feb 25, 2008 at 18:03
If an alternator does not put out 13.8 volts plus it will NEVER charge an AGM battery.

Just remember some alternators will back off on its voltage due to the fact that it heats up and consideres the main battery charged at about 70%

When you work this mute point at 'whats fully charged?' let me know. I want my AGM battery fully charged i.e. 100% = 12.9 volts at rest.

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FollowupID: 554612

Follow Up By: Mike Harding - Monday, Feb 25, 2008 at 18:31

Monday, Feb 25, 2008 at 18:31
>If an alternator does not put out 13.8 volts plus it will NEVER charge an AGM battery.

I don't think that is correct. Do you have any supporting evidence for the statement?

>When you work this mute point at 'whats fully charged?'

AS4029 defines "fully charged" as (paraphrasing from memory) "when the charging current has not significantly decreased over a period of X hours" - I'll check the exact wording if you like?

This link looks interesting but I don't have time to read and absorb it right now:
Batteries and stuff

Mike Harding
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FollowupID: 554616

Follow Up By: Mainey (wa) - Monday, Feb 25, 2008 at 18:34

Monday, Feb 25, 2008 at 18:34
Garry:
instead of just stating "how ILLEGAL this idea is" it would help if you just post any link you are aware of showing it to be "ILLEGAL" and as Mike has stated most, if not all inverters, are "isolated" from the chasis.


Feral:
If an Alternator ONLY put out 13.8 Volts I would have it checked out.

Fully charged is when the 12v wetcel battery is 12.66 Volts and the AGM is 12.8 Volts, 3 hours (at rest) after taken off the charging 'apparatus'

With-out getting technical, remember it's not Volts that charge the 12v battery - but Amps!
The more Amps put into the 12v battery (@ 12+ Volts) the faster it charges, the less Amps the slower it charges, at the same Voltage.

Mainey . . .
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FollowupID: 554617

Follow Up By: Dunaruna - Monday, Feb 25, 2008 at 18:43

Monday, Feb 25, 2008 at 18:43
It's not that simple Mainey, voltage is the driving force behind amps to begin their journey. The more voltage, the more amps will flow.

The key to getting those amps to the caravan is to minimise voltage drop.
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FollowupID: 554618

Follow Up By: Mainey (wa) - Monday, Feb 25, 2008 at 18:56

Monday, Feb 25, 2008 at 18:56
Dunaruna, yes,
but as I said -> ""With-out getting technical"" .....

""The more Amps put into the 12v battery (@ 12+ Volts) the faster it charges, the less Amps the slower it charges, at the *SAME* Voltage""

If the Voltage changes yes everything will change, hence my *SAME* voltage statement, but then you have to get technical and I, and I'm sure other people, don't want to read over the top technical posts.

The key to getting whatever Amps/Volts to the caravan is having a decently sized battery cable, just as simple as that, the lower the cable resistance the higher the delivered power at the caravan battery.

Mainey . . .


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FollowupID: 554621

Follow Up By: feral - Monday, Feb 25, 2008 at 19:12

Monday, Feb 25, 2008 at 19:12
...and thats the key.

With charging using your alternator you have to have a dirty big cable running the length of the vehicle and van and hope that you have minimal voltage loss over that length.

With using a inverter/charger it doesn't matter as much. Your inverter will still run at 12 volts and therefore charge your AGM battery to 100%

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FollowupID: 554624

Follow Up By: Mainey (wa) - Monday, Feb 25, 2008 at 19:19

Monday, Feb 25, 2008 at 19:19
I'm not going to argue with you... it only needs a 'battery cable'

However, I will just ask you, where do you derive the 12v power from for the Inverter ??

Remembering the AGM battery being charged is in the Caravan !!

Are we running 240v from the vehicle to the Caravan ??

Are we actually charging the same AGM battery that is supplying the power to the Inverter ??

Mainey . . .
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FollowupID: 554626

Follow Up By: feral - Monday, Feb 25, 2008 at 19:23

Monday, Feb 25, 2008 at 19:23
In relation to the safety aspect you can easily set it up with a relay.

The way to set it is that the power to the inverter comes on via the relay only on accessory position or you can even find the power source for the fuel pump or even the oil pressure guage.

Any of these once it's off or stopped the inverter is off.

And only run an electronically isolated inverter.
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FollowupID: 554627

Follow Up By: Mike Harding - Monday, Feb 25, 2008 at 19:33

Monday, Feb 25, 2008 at 19:33
>With charging using your alternator you have to have a dirty big
>cable running the length of the vehicle and van and hope that
>you have minimal voltage loss over that length.

Well... not really... the initial inrush into a partially discharged battery will be high (30A+ for an AGM if the source impedance is low enough) but that will soon drift off to a lower sum and, as I keep telling this forum, AGM batteries are NOT capable of sinking whatever amount of current you care to throw at them! Trying to stuff huge amounts of currents into them _will_ damage them.

So the reality:

put in the biggest sensible cables you can, 2.5mm CROSS SECTIONAL BLOODY AREA - NOT STUPID "AUTOMOTIVE CABLES" (I feel better already :) and above. 6mm CSA preferably, will provide a quite adequate charging path for batteries in a vehicle or caravan

That's it really....

Mike Harding
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FollowupID: 554631

Follow Up By: feral - Monday, Feb 25, 2008 at 19:51

Monday, Feb 25, 2008 at 19:51
Oh no Mainey...no argument here either. I'm just trying to sort the chaff from the wheat!!!

Most vanners already have a decent cable hooked up to the van to power the fridge so they take their power from that.

This whole thought process assumes to many things for it to happen effectually.

What do you do if your alternator does not put out 13.8 plus volts all day. Some modern alternators do drop off to as low as 13.2 volts. Seriously, just ask....don't dismiss it.

Voltage drop..from main battery in front of vehicle to rear of van. How many metres do think it would be...10, 12, 15? Imagine to size of cable you need to stop voltage drop, remember every 0.1 volt counts whereas with an inverter it doesn't matter.



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FollowupID: 554638

Follow Up By: Mainey (wa) - Monday, Feb 25, 2008 at 19:57

Monday, Feb 25, 2008 at 19:57
Feral, I ask again, where do you derive the 12v power from for the Inverter ??

As the AGM battery being charged is in the Caravan !!
Are we running 240v from the vehicle to the Caravan ??
Are we actually charging the same AGM battery that is supplying the power to the Inverter ??

6 AWG cable will give 0.066 Volt loss in 10 Mtrs...

Mainey . . .
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FollowupID: 554639

Follow Up By: feral - Monday, Feb 25, 2008 at 20:15

Monday, Feb 25, 2008 at 20:15
>where do you derive the 12v power from for the Inverter ??

From the car, usually using an direct cable from the main battery.

>As the AGM battery being charged is in the Caravan !!
Correct

>Are we running 240v from the vehicle to the Caravan ??
No.

>Are we actually charging the same AGM battery that is supplying the power to the Inverter ??
No
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FollowupID: 554647

Follow Up By: Mainey (wa) - Monday, Feb 25, 2008 at 20:43

Monday, Feb 25, 2008 at 20:43
>Are we running 240v from the vehicle to the Caravan ??
No. Are we actually charging the same AGM battery that is supplying the power to the Inverter ??
No….. <- so we are getting the power from the car !!

remember that 6 AWG cable will give 0.066 Volt loss in 10 Mtrs... so basically NILL Voltage loss



So the Alternator will fully charge the Aux battery after all information is investigated !!

Mainey . . .
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FollowupID: 554656

Follow Up By: Member - Mike DID - Monday, Feb 25, 2008 at 23:09

Monday, Feb 25, 2008 at 23:09
"remember that 6 AWG cable will give 0.066 Volt loss in 10 Mtrs"

??? at what current.
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FollowupID: 554689

Follow Up By: Derek from Affordable Batteries & Radiators - Monday, Feb 25, 2008 at 23:14

Monday, Feb 25, 2008 at 23:14
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Follow Up By: Mainey (wa) - Monday, Feb 25, 2008 at 23:15

Monday, Feb 25, 2008 at 23:15
@ 5 Amps
or
just over 0.01 @20 Amps which is the MAXIMUM to recharge the 200 ah battery system.

Mainey . . .
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FollowupID: 554691

Follow Up By: Member - Mike DID - Monday, Feb 25, 2008 at 23:22

Monday, Feb 25, 2008 at 23:22
Every AGM Data sheet I've seen shows that maximum charge current between 0.25 and 0.3 C.

For a 200ah battery that 50 to 60 amps.
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FollowupID: 554695

Follow Up By: Mainey (wa) - Monday, Feb 25, 2008 at 23:29

Monday, Feb 25, 2008 at 23:29
Flooded batteries should be charged at no more than the "C/8" rate for any sustained period

"C/8" is the battery capacity at the 20-hour rate divided by 8

For a 220 AH battery, this equals 26 Amps

Gelled cells should be charged at no more than 5% of their amp-hour capacity

Mainey . . .
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FollowupID: 554697

Follow Up By: Member - Mike DID - Monday, Feb 25, 2008 at 23:45

Monday, Feb 25, 2008 at 23:45
"downtools posted:
Will go with AGM's for the faster recharge."

AGMs are neither Flooded nor Gel.
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FollowupID: 554699

Follow Up By: GaryInOz (Vic) - Monday, Feb 25, 2008 at 23:57

Monday, Feb 25, 2008 at 23:57
Mainey wrote: "remember that 6 AWG cable will give 0.066 Volt loss in 10 Mtrs... so basically NIL Voltage loss"

Absolutely false. It is NOT a fixed amount of voltage drop. The voltage drop per meter is solely dependent on the current through the wire, multiplied by the resistance (per metre) of the wire, per Ohms law (V=IxR). The more current that is passed (in the case of a 300 watt inverter ~36-40 amp) and the distance to the van (~8 metres or so, and earth return = 16m) taking into account the resistance per metre of 6 AWG (your spec, at 1.5 milliOhm/metre, is going to cause considerable voltage drop.

40 x 16 x.0015 = 0.96 volts

And that is before you take into account resistive losses in the anderson connectors and so on, ie, a purely "scientific" value. Realistically about 1.1-1.2 volts would be reasonable as a voltage loss between the alternator and inverter in the van, or for a deeply charged battery in the van attempting to charge at 40 amps. This really cannot be avoided, but can to a large degree be dealt with

http://www.bnoack.com/index.html?http&&&www.bnoack.com/data/wire-resistance.html

One option is a 12 volt to 15 volt inverter (DC-DC) which will take the 10-13 volts you may have and up it to 15 volts, from which you can run a solar battery charger controller to charge the battery in the van at an appropriate 14.4-14.8 battery charging voltage.

DC-DC inverter:http://www.snaptec.com.au/dcdc/pdf/za-zx.pdf

The added bonus is you can also hook up some solar cells to charge your battery through the solar controller when on site.

This approach should be reasonably efficient and safe when compared to any 240 volt type solution you could propose, it is able to handle bad connections in the alt-van line without affecting the charging of the van battery, and gives the flexibility of being able to go solar at some later stage.

Pretty close to the best solution all around, but may not be the cheapest initially. The savings in not having mistreated batteries to dispose of every year or two would soon recoup the costs involved.
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FollowupID: 554704

Follow Up By: GaryInOz (Vic) - Tuesday, Feb 26, 2008 at 00:02

Tuesday, Feb 26, 2008 at 00:02
Clarification:

Run the "dirty" alt voltage down to the van and install the DC-DC inverter in the van
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FollowupID: 554705

Follow Up By: Derek from Affordable Batteries & Radiators - Tuesday, Feb 26, 2008 at 00:08

Tuesday, Feb 26, 2008 at 00:08
Hi Gary

Which solar regulator would you use to short out the (+) and (-) of this expensive but impressive piece of equipment.
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FollowupID: 554707

Follow Up By: Nomadic Navara - Tuesday, Feb 26, 2008 at 00:26

Tuesday, Feb 26, 2008 at 00:26
Firstly

It is not illegal to to run an inverter in a vehicle when you are traveling. It probably is not a good idea to have the 240V leads running from your tug to your van, unless an electrician has installed it (and possibly none will.) If you have the inverter closely coupled to your battery charger in the van it is perfectly safe.

Secondly

An motor vehicle alternator is not a good device to charge a deep cycle battery. It may charge a starting battery sufficiently to prevent a starting battery from sulphating but it will not charge a deep cycle battery to 100% of its rated capacity.

To achieve full charge you need a sustained voltage of more than 14V for a considerable time. A vehicle alternator may put out 14.4 to 14.6V when you first start your engine in the morning. The alternator may continue to put out that voltage when you are standing still testing the voltage with the bonnet up. However when you go for a run and you are 40 minutes or more down the road towing your van the temperature compensation in the regulator will reduce the alternator output to less than 14V. If this does not happen your battery will get cooked.

I am yet to see a vehicle that does not have temperature compensation in its alternator regulator. I still keep asking in these forums for people to measure the alternator voltage over the first hour of a trip and report the voltages they observe. Some have reported voltages dropping as I expect with temperature compensation but none have come back and reported that the voltage has remained the same from a cold start up to the end of their journey.

PeterD

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FollowupID: 554715

Follow Up By: GaryInOz (Vic) - Tuesday, Feb 26, 2008 at 01:23

Tuesday, Feb 26, 2008 at 01:23
Derek, re-reading the spec of the inverter, it has an adjustable output of 13.5 to18.0V output from the 15 v nominal output, so you could set it straight to the battery at a voltage you would consider appropriate for a long deep charge (~14.4 volts). You wouldn't need the solar charger.

Years ago we had a similar problem with a piece of equipment that was designed to work in a chopper under power(28.8V that we needed to run in a stationary vehicle. The converter that came with the equipment (14.4-28.8v) worked OK in a broad sense with the vehicle engine running but was unsatisfactory with the vehicle stopped (13.2 v) causing too much ripple/noise in the supply line (important when you are dealing with a broadcast quality microwave link transmitter), and the alternator noise made running the vehicle not an option. We ended up modifying the DC-DC converter by taking a few coils off the primary windings of the internal transformer to make it step the voltage up a fraction in its secondary (or at least give better "headroom" for the internal regulation circuitry). Known as "bucking" the voltage a bit.

Similar principle being used here, except going from a bit under to what you need to charge a battery
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FollowupID: 554720

Follow Up By: feral - Tuesday, Feb 26, 2008 at 07:25

Tuesday, Feb 26, 2008 at 07:25
Nomadic Navara is right on the money.

After your voltage loss from your heated alternator and main battery combined with the voltage loss of your cable running the length of your rig you would most likely be down to 12 and a bit volts. 13 volts at best.

It also depends on what type of charge the AGM battery will get. With the right battery charger they have a pulse charge which will charge the AGM battery better than the bulk charge from an alternator.

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FollowupID: 554721

Follow Up By: Mainey (wa) - Tuesday, Feb 26, 2008 at 09:15

Tuesday, Feb 26, 2008 at 09:15
Whatever happened to the Alternator REGULATOR ??

When *travelling* the Cranking battery and Auxiliary battery are paralleled by the battery isolator and is seen by the Regulator as only one large battery, this takes into account any and ALL voltage drop created in the Aux battery cable !!

Mainey . . .
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FollowupID: 554734

Follow Up By: Nomadic Navara - Tuesday, Feb 26, 2008 at 13:24

Tuesday, Feb 26, 2008 at 13:24
Mainey

"Whatever happened to the Alternator REGULATOR ??" - precisely nothing.

In FollowUp 29 you seem to be making the mistake that most people make. Your post seems to infer that the regulator monitors the battery. The regulator is connected to a wire in the alternator that is connected to the output of that alternator. All it monitors is the alternator. If it monitored the battery (or batteries) it would be connected directly to the battery by a wire (often called the sense wire) so that if any significant resistance occurred in the charging cable then the regulator would sense the voltage at the battery terminal. This is often done in marine installations, in that case it would take into account any and All voltage drop created in the cable (to paraphrase your remarks.)

The second thing the alternator seances is temperature. In our simple regulators there is a heat sensitive element that senses the temperature of that regulator. If the regulator is mounted in the alternator then all it measures is the internal temperature of that alternator. Not the temperature of the battery.

There are alternators used in the marine industry that do have sense wires connected to the battery terminal and remote temperature sensors that are stuck on the side of the battery. These regulators do monitor the battery conditions. Our regulators DO NOT monitor or sense the battery.

There are a few things taken into account when the regulator is designed. They include the battery type, the expected working temperatures under the bonnet over the whole operating range and the charge voltages required for the battery under the different temperatures in that operating range. A further complication these days is the battery is often mounted so that it has its own air supply and operates at a lower temperature than the alternator.

The temperature compensation circuitry in the regulator is designed to attempt to supply the correct voltage to charge the battery at all operating temperatures over which the battery will be subjected to. It has to do this without risk of overcharging the battery in any part of the world where the vehicle is likely to be operated. Because the regulator must be set to not exceed too higher voltage under all conditions, the output is set a little lower than the maximum charge voltages. This is why an alternator will not charge a battery to 100% of its rated capacity. This is OK in automotive applications as a battery will not sulphate if it is kept above 55- 60% of its theoretical maximum capacity. It is also fair enough to refer to a starting battery to be fully charged under these conditions, but please do not refer to a deep cycle battery as being fully charged when charged like this. It is not.

In marine applications a second alternator is often added to the motor to charge the auxiliary batteries. These have battery voltage and temperature sense circuitry connected to the battery. These do achieve a charge of nearly 100% of the batteries rated capacity. Our alternators do not have this sophistication and so fall short when asked to maintain a deep cycle battery. Yes I know that some people successfully operate a fridge from an auxiliary battery in their vehicle. When doing that they are operating the battery somewhere down in the operating range and not at the top of the operating range. This will reduce the life of the battery. This may be acceptable as most of us will not require the full number of discharge cycles over the acceptable life of a battery. This also does not alter the fact that an alternator will not fully charge a deep cycle battery.

PeterD
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FollowupID: 554766

Follow Up By: Mainey (wa) - Tuesday, Feb 26, 2008 at 13:35

Tuesday, Feb 26, 2008 at 13:35
""When *travelling* the Cranking battery and Auxiliary battery are paralleled by the battery isolator and is seen by the Regulator as only one large battery, this takes into account any and ALL voltage drop created in the Aux battery cable !!""

Now we all know what happened to the Alternator :-))

Mainey . . .
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FollowupID: 554768

Follow Up By: GaryInOz (Vic) - Tuesday, Feb 26, 2008 at 18:15

Tuesday, Feb 26, 2008 at 18:15
Original post stated that he was going to use AGM (optima, or odyssey) both of which can take FAR more current to recharge (inrush current) to do the "bulk" charge of the battery and will happily take a considerably higher current to do the topping up than a "sloppy" or a SLA. The pedantics of what rate you can charge are an AGM are irrelevant, they will take as much as you can give them.

I know for a fact that Odyssey batteries can be repeatedly discharged to 20% charge level and accept a full tilt charge in 90 mins of whatever current you can supply. There is no charge limitations imposed on them due to their very low internal resistance and consequent lack of heat generation under charge. Far safer in a van environment as there is NO gas production either.

SLA's and "sloppys" are very old hat these days when compared against true AGM's. The best you can really get out of an SLA is about 40% depth of discharge at a low rate, and sloppys are about 50% depth of discharge. AGM can be taken down to 20% of depth of discharge and bounce back continually (in excess of 500 times IIRC) with NO ill effects.

"When *travelling* the Cranking battery and Auxiliary battery are paralleled by the battery isolator and is seen by the Regulator as only one large battery, this takes into account any and ALL voltage drop created in the Aux battery cable !!"

....and incorrect again. The alternator will see the vehicle battery, with the van battery connected to the alternator via a resistor (the long wire to it). This tends to "insulate" the the van battery from being able to take the full voltage due to the trickle charge current x the wires resistance. As most here would know dropping 0.25-0.3 volt on a battery is about equivalent to a battery that has been discharged about 20% or so.
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FollowupID: 554802

Follow Up By: Mainey (wa) - Tuesday, Feb 26, 2008 at 18:46

Tuesday, Feb 26, 2008 at 18:46
Garry, are you saying, when the Cranking battery is connected to the Aux battery they *DON'T* 'equalise' via the "resistor (the long wire to it)" or as we commonly call it a battery cable.

Mainey . . .
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FollowupID: 554807

Follow Up By: Member - Mike DID - Tuesday, Feb 26, 2008 at 19:37

Tuesday, Feb 26, 2008 at 19:37
NO ! Two batteries connected to together will NOT equalise in charge. I have actually tested it, other than some minimal charge transfer, it does NOT happen.

A fully charged battery puts out 12.6 volts - you need MORE THAN 13.0 volts to charge a battery.

The "two buckets connected by a hose" analogy is useless. If batteries put out 6 volts when they were 50% discharged, then the "two buckets " analogy would apply.
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FollowupID: 554820

Follow Up By: GaryInOz (Vic) - Tuesday, Feb 26, 2008 at 20:44

Tuesday, Feb 26, 2008 at 20:44
Mainey wrote:

"Garry, are you saying, when the Cranking battery is connected to the Aux battery they *DON'T* 'equalise' via the "resistor (the long wire to it)" or as we commonly call it a battery cable."

The vehicle battery will always get "preferential" charging and come up to fully charged first, with the van battery some way behind it due to the voltage and current limiting of the "wire" between the alternator and the van, and even then will never get to the fully charged state for the reasons I described above (residual voltage drop due to resistance and trickle charge current).

Remember that if the two batteries were left in parallel with the ignition off then the vehicle battery and the van battery would equalize, but you would be going from (say) veh 100% and van 80%, to veh 90% and van 90%. Now you are not 100% in either battery, nor are you "fully" charged.

The reality is the batteries are disconnected at ign off and the last voltage the alt saw was more than likely the fully charged veh battery.

We can argue about this all day, but it is a reasonably established fact that this process does indeed occur, simply by empirical observations by many people over many years. "The battery in my van never gets fully charged while I'm traveling" (note "FULLY" charged).
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FollowupID: 554850

Follow Up By: Mainey (wa) - Wednesday, Feb 27, 2008 at 00:36

Wednesday, Feb 27, 2008 at 00:36
Garry, we won't argue about this all day :-)

just a question:

How do you 'fully charge' a battery in a van - while travelling ?

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FollowupID: 554897

Follow Up By: Nomadic Navara - Wednesday, Feb 27, 2008 at 02:21

Wednesday, Feb 27, 2008 at 02:21
"How do you 'fully charge' a battery in a van - while travelling ?"

Simple - there a couple of ways:

Install an inverter and a multi stage battery charger in your van. DO NOT wire it up in any fancy arrangement - that is for a licensed electrician to do. Just plug the battery charger into the inverter output socket. That way if there is no lethal voltages floating around if the van is involved in an accident.

The other way is to use a battery recharger. There are two that are readily available. First there is the Arrid Twin Charge battery charger. It suffers from the problem that it has a fixed output voltage. the second is the RanOx Battery Booster - this one incorporates a multi stage battery charger and is my preferred one.

PeterD
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Follow Up By: Mainey (wa) - Wednesday, Feb 27, 2008 at 09:37

Wednesday, Feb 27, 2008 at 09:37
So the makers of those really "smart" battery Isolators don't even get a look in, maybe it's because they won't keep the Aux battery 'fully charged' (according to some, simply by their exclusion) as they are not mentioned anywhere in this entire thread.

Maybe there should be a warning on their adverts and packaging that they will NOT allow full battery charging to the Aux battery L0L

I just checked my AGM system, 7.35am, it's 12.9v and the Solar system has been removed for over a week, maybe the Rotronics isolator or size of cabling or ????? as the Alternator is only 55 Amps !!

Mainey . . .
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Follow Up By: Nomadic Navara - Wednesday, Feb 27, 2008 at 13:46

Wednesday, Feb 27, 2008 at 13:46
Mainey

I consider all battery isolators (that do not boost the charging voltage) to be in the snake oil category. The so called smart ones just delay the connection of the auxiliary battery a little longer (possibly.) If they delay the connection too long then the auxiliary battery will miss out on the few minutes of the higher alternator voltage before the motor commences to warm up and the temperature compensation kicks in.

So you have only had your solar system disconnected for less than a fortnight. The Rotronics system will still be supplying a maintenance trickle charge. Wait until you start working your battery. that is when the lack of solar system will allow you to run down the average state of charge of your battery - (have another look at the last paragraph on FollowUp 30.)

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Reply By: Dunaruna - Monday, Feb 25, 2008 at 17:44

Monday, Feb 25, 2008 at 17:44
As someone has already mentioned, the inverter/charger setup is becoming popular in some circles. I'm not sure why though, it's such an inefficient use of limited resources, and it's dangerous.

You already are in possession of the absolute best charger on the market - your vehicles alternator. Set the aux circuit up correctly and your van batteries will be charged.
AnswerID: 289327

Follow Up By: Mike Harding - Monday, Feb 25, 2008 at 19:19

Monday, Feb 25, 2008 at 19:19
>and it's dangerous.

Why is it dangerous?

Mike Harding
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Follow Up By: Dunaruna - Monday, Feb 25, 2008 at 19:34

Monday, Feb 25, 2008 at 19:34
I work on caravan wiring for a living. I guarantee you that you would be dumbfounded at the disgusting lack of quality and workmanship hidden behind the walls of a van (both 12v & 240v) - ANY van.

To add an unstable 240v circuit into this just doesn't make any sense to me, especially as this circuit would be active while in motion. I've seen too many melted wires to even consider this.

That being said, I CAN see the upside of having an inverter/charger circuit, but the downside wins - IMHO.

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Follow Up By: Mike Harding - Monday, Feb 25, 2008 at 19:38

Monday, Feb 25, 2008 at 19:38
I repeat: why is it dangerous?

Mike Harding
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Follow Up By: Dunaruna - Monday, Feb 25, 2008 at 19:58

Monday, Feb 25, 2008 at 19:58
Your a hard man to please. (insert smiley face here)

See previous followUp. I can't add anything more - for now.
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Follow Up By: feral - Monday, Feb 25, 2008 at 20:04

Monday, Feb 25, 2008 at 20:04
Because it is not!! It is no more danderous than pluging in a powerboard at home.

These inverter are used in vehicles every day of the week and yet there is much constination about using 240 volt. They all have their own inbuilt safety devices. The charger has it's own inbuilt safety devices. You install our own safety devices through fuses, circuit breakers and switches.

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Follow Up By: Dunaruna - Monday, Feb 25, 2008 at 20:07

Monday, Feb 25, 2008 at 20:07
Are power boards dangerous at home?
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Follow Up By: Dunaruna - Monday, Feb 25, 2008 at 20:08

Monday, Feb 25, 2008 at 20:08
For that matter, are popcorn machines dangerous at home?
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Follow Up By: feral - Monday, Feb 25, 2008 at 20:17

Monday, Feb 25, 2008 at 20:17
Popcorns ready!!!!

LOL.
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Follow Up By: Dunaruna - Monday, Feb 25, 2008 at 20:19

Monday, Feb 25, 2008 at 20:19
I'll take mine with real butter thanks.................
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Follow Up By: Mainey (wa) - Monday, Feb 25, 2008 at 20:48

Monday, Feb 25, 2008 at 20:48
I think it can now be confirmed the 240v inverter is safe :-))

Mainey . . .
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Follow Up By: Dunaruna - Monday, Feb 25, 2008 at 21:30

Monday, Feb 25, 2008 at 21:30
Confirmed? How?
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Follow Up By: Mainey (wa) - Monday, Feb 25, 2008 at 21:42

Monday, Feb 25, 2008 at 21:42
as feral has posted:
"""Because it is not!!
It is NO more danderous than pluging in a powerboard at home.
They all have their own INBUILT SAFETY DEVICES.
The charger has it's own inbuilt SAFETY DEVICE.
You install our own SAFETY DEVICES through FUSES, CIRCUIT BREAKERS and SWITCHES"""

They are built to stringent electrical standards, no I don't have a clue what they are, but they are like ALL sertified electrical devices, built to a standard.
Mainey . . .
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Follow Up By: Member - Mike DID - Monday, Feb 25, 2008 at 23:16

Monday, Feb 25, 2008 at 23:16
What's the likelihood of a powerboard at home being involved in a collision at 100km/hr that causes the crunching of metal ?

If one of the 240v wires out of the isolated Inverter gets crushed and shorted to the chassis, then a survivor or a rescuer who touches the other inverter output will receive a fatal 240volt shock.

Rescuers have enough problems with all the airbags and explosive pre-tensioners, they really don't need the additional hazard of live 240volts in the wreckage.
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Follow Up By: Mainey (wa) - Monday, Feb 25, 2008 at 23:20

Monday, Feb 25, 2008 at 23:20
Mike are you saying the Fuse's and inbuilt safety cut-out devices will NOT work as designed ?

Mainey . . .
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Follow Up By: Member - Mike DID - Monday, Feb 25, 2008 at 23:25

Monday, Feb 25, 2008 at 23:25
Are you assuming that if one output lead of an Isolated output inverter is connected to the case it will shut down ?
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Follow Up By: Mainey (wa) - Tuesday, Feb 26, 2008 at 09:33

Tuesday, Feb 26, 2008 at 09:33
Mike, what I'm 'assuming' is in the case of an accident, where the Inverter cable is damaged and earthed to the vehicle body, it will instantly blow a "fuse" or "circuit breaker" or similar "safety device"

This will then instantly stop the flow of electricity in the cable
Mainey . . .
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Follow Up By: Member - Mike DID - Tuesday, Feb 26, 2008 at 14:09

Tuesday, Feb 26, 2008 at 14:09
In an Isolated-Output regulator, the 240 volt output is floating, so earthing either of the 240 volt wires will have no effect. It will just raise the other wire to 240 volts AC above earth, making contact with that one wire hazardous.

On the other, if you mean that in an accident you ASSUME there will ALWAYS be damage to the wiring (+12 volts in, BOTH 240 volt output wires) so that the fuse will ALWAYS blow, then I'm glad it's not you designing safety systems that I depend on.

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Follow Up By: Mainey (wa) - Tuesday, Feb 26, 2008 at 15:20

Tuesday, Feb 26, 2008 at 15:20
What I'm saying is: when the "fuse" blows, it will NOT carry electricity in that cable past the "blown" fuse, either 12v or 240v.

Mainey . . .
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Follow Up By: GaryInOz (Vic) - Tuesday, Feb 26, 2008 at 18:35

Tuesday, Feb 26, 2008 at 18:35
Mike are you saying the Fuse's and inbuilt safety cut-out devices will NOT work as designed ?

Mainey . . .

You can be electrocuted in less time than it takes a fuse to blow, or a thermal cutout to trip, these are designed to save the wiring or the electronics.
There is no true "earth" on inverters, so there can be no true earth leakage detector (like fitted to your house). The issue arises where you have two different metallic surfaces in contact with the active and neutral of the inverter, all is fine until YOU happen to touch both simultaneously. You are not a true "short circuit" and require only 10-15 milliamps at 240 volts therefor only using 2-3 watts of your 300 watt available in order to be FATALLY electrocuted, in other words not even an overload situation.

If you want to give a practical demonstration of how "safe" inverters are in hostile high vibration, damp, occasionally salty environments, by playing russian roulette with the 240 volts in the vehicle after the mother of all accidents, we welcome you acceptance of the challenge. (pre-booking "Darwin Award" nomination as we speak...)

Why you feel it is reasonable to expect that rescue workers should be subjected to the same is absolutely unfathomable.
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Follow Up By: Mike Harding - Tuesday, Feb 26, 2008 at 18:55

Tuesday, Feb 26, 2008 at 18:55
OK... I know this is hard - indeed... I feel your pain but... it's time to "let go" people!

Fear not: we'll have many other conflicts over electricity, batteries, goats, charging systems, solar panels, fridges and the true meaning of life... but this forum does not lend itself to posts with more than about 20 replies. (Frankly a few of the regular contributors would have trouble sustaining an attention span of than length :)

May I, humbly, suggest we start a new thread entitled "12V systems - "Is this the full argument or just a five minute one"? :)

Mike Harding
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Follow Up By: Mainey (wa) - Tuesday, Feb 26, 2008 at 19:01

Tuesday, Feb 26, 2008 at 19:01
Garry, lets assume there is an accident !!
the cable is either 12v or 240v and is 'exposed' and now live, it touches the vehicle body, because something must have 'exposed' it, the "fuse" will then blow.

At that point the cable is now just a 'dead' cable and can not carry current because the fuse blew when the cable was 'earthed' to the body.

How will that wire electrocute rescuers who attend the accident ?

Mainey . . .
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Follow Up By: Axel [ the real one ] - Tuesday, Feb 26, 2008 at 19:34

Tuesday, Feb 26, 2008 at 19:34
Sitting here almost pi--ing myself laughing at some of these replies ,, I have a question , a DEAD serious question for all you experts on 12v and recharging ,and those who say having 240v is safe in a vehicle why have 12 volt at all ???
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Follow Up By: Mainey (wa) - Tuesday, Feb 26, 2008 at 19:38

Tuesday, Feb 26, 2008 at 19:38
Bugga, I thought the 12v battery was required because the starter motors were 12v

Mainey . . .
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Follow Up By: Mike Harding - Tuesday, Feb 26, 2008 at 19:38

Tuesday, Feb 26, 2008 at 19:38
Let go Axel - it's too complicated for you... you already have 30,000 volts in your vehicle... what makes you think that is safe?
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Follow Up By: Member - Mike DID - Tuesday, Feb 26, 2008 at 19:41

Tuesday, Feb 26, 2008 at 19:41
"GaryInOz (Vic) posted:
Mike are you saying the Fuse's and inbuilt safety cut-out devices will NOT work as designed ?"

If the 240volt output is totally isolated and one output is connected to earth, why would a fuse blow ? There is no return current path - until you connect the other output to earth - via a body ?
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Follow Up By: GaryInOz (Vic) - Tuesday, Feb 26, 2008 at 20:55

Tuesday, Feb 26, 2008 at 20:55
Mike DID wrote:

"GaryInOz (Vic) posted:
Mike are you saying the Fuse's and inbuilt safety cut-out devices will NOT work as designed ?"

If the 240volt output is totally isolated and one output is connected to earth, why would a fuse blow ? There is no return current path - until you connect the other output to earth - via a body ?"

GaryInOz wrote:

"The issue arises where you have two different metallic surfaces in contact with the active and neutral of the inverter, all is fine until YOU happen to touch both simultaneously."

I agree, all it takes is some non-earthed bit of metal (shrapnal?, SS mug, cutlery, collapsable chair, gas bottle, etc) to be in contact with the active side, and the neutral to be in contact with the vehicle. God help you if you lean into the vehicle to clear away that ("hot) piece of metal

-------------------------------------------

This bit, "Mike are you saying the Fuse's and inbuilt safety cut-out devices will NOT work as designed ?" was actually attributed to Mainey, sorry I forgot to use quotation marks and a by-line on it. My bad...
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Reply By: Mike Harding - Monday, Feb 25, 2008 at 19:54

Monday, Feb 25, 2008 at 19:54
I believe someone earlier said it...

but I think I'm going to start calling these "Popcorn posts".

Mike Harding
AnswerID: 289356

Follow Up By: Richard Kovac - Tuesday, Feb 26, 2008 at 00:19

Tuesday, Feb 26, 2008 at 00:19
is this like sex to you blokes... LOL
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Follow Up By: Mainey (wa) - Tuesday, Feb 26, 2008 at 09:20

Tuesday, Feb 26, 2008 at 09:20
Richard,
I think not !!
because sex only lasts for a few hours lol

Mainey . . .
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Follow Up By: GaryInOz (Vic) - Tuesday, Feb 26, 2008 at 18:43

Tuesday, Feb 26, 2008 at 18:43
Pass the popcorn..............
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Follow Up By: Mike Harding - Tuesday, Feb 26, 2008 at 18:56

Tuesday, Feb 26, 2008 at 18:56
Sorry Richard, I didn't realise you were old enough to have sex :)
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Follow Up By: Member - bushfix - Tuesday, Feb 26, 2008 at 19:48

Tuesday, Feb 26, 2008 at 19:48
Mike,

i just got here....but I APPLAUD your Python reference atop from here.

credit where it is due.

kind regards.

don't mind me....

lemon curry?
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Follow Up By: Mike Harding - Tuesday, Feb 26, 2008 at 19:52

Tuesday, Feb 26, 2008 at 19:52
bushfix: there comes a point where you just have to laugh :)

Singapore noodles for me tonight - a delightful recipe (albeit a little hot) - I'll post it here at the weekend :)

Mike Harding
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Follow Up By: GaryInOz (Vic) - Tuesday, Feb 26, 2008 at 20:56

Tuesday, Feb 26, 2008 at 20:56
Twist of lemming as well???
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Reply By: downtools - Wednesday, Feb 27, 2008 at 14:56

Wednesday, Feb 27, 2008 at 14:56
Thanks for all your replies and info!!
There are and always will be conflicting data and opinions.
After wading through your replies. speaking to auto electricians and using past experience I have decided to go this way....

1. Fit the largest AGM battery(that can handle under bonnet temps) that will fit in the space under the bonnet.

2. Remove the "Redarc" isolator and replace it with a very heavy duty manual on off switch.

3. Charge the AGM with either a "twin charge" or "Ranox" 3 stage battery booster with solar back up.(100watt panel).

This way I figure the AGM will charge quickly and give good deep cycle performance.
If the charger fails at any time, I can lock the 2 batteries together, with the manual switch, to get me out of strife.
Also if the cranker somehow goes flat then I should be able to "jump start" the car off the AGM by closing the manual switch.
I was originally going to use 2 AGMs but now will save weight, money and keep it simple with one aux.
I know some of you won't agree but thats the nature of the beast.
Thanks again for your time and info
Cheers Nifty

AnswerID: 289644

Follow Up By: Mainey (wa) - Wednesday, Feb 27, 2008 at 15:06

Wednesday, Feb 27, 2008 at 15:06
So another 12 Volt thread closes....
with the instigator aware of what he's doing!

Mainey . . .
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Reply By: Mogul - Wednesday, Feb 27, 2008 at 15:23

Wednesday, Feb 27, 2008 at 15:23
What's the difference cable wise between running an inverter and running a 12V charging cicuit.

AnswerID: 289646

Follow Up By: GaryInOz (Vic) - Wednesday, Feb 27, 2008 at 18:25

Wednesday, Feb 27, 2008 at 18:25
The inverter would probably tolerate the 11-12 volt at the 30 or so amps it would need for a 300 watt inverter, stepping it up to the "regulated" 240 volts with a possible slight loss of efficiency over and above what there would be if it was supplied with 13.2 volt. In the van the regulated three stage charger would simply see the 240 volts as any other 240 volt source.

May be some issues if you try to use a basic square wave or modified square wave inverter with a switchmode power supply in the charger. Not usually good bed mates....
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Reply By: ajr - Wednesday, Mar 12, 2008 at 09:11

Wednesday, Mar 12, 2008 at 09:11
as mentioned earlier in this thread there are some alternatives to messing about with inverters and 3 stage battery chargers to charge a remote camper battery. there is a purpose built product that can be found at www.ranox.com.au that has 3 stage charging and fully adjustable output voltages and currents (up to 25A) and all is done at the safe 12 volt level.

I have used one of these chargers for a couple of years and always arrive at the camp site with a (100%) fully charged battery

take a look

AJR
AnswerID: 292269

Follow Up By: downtools - Wednesday, Mar 12, 2008 at 10:11

Wednesday, Mar 12, 2008 at 10:11
AJR,
Thanks for that. I spoke to this company and they were very helpful, sent me lots of info and wiring diagrams etc.
The idea of a "smart" charger that runs off 12volts is ideal!
Especially when the current and voltages are adjustable.
The only draw back I can see with the Ranox is that the fridge (or any load) cannot be connected directly to the battery while it's being charged. The Ranox guy said this could cause overcharging.
This can be overcome with suitable relays, fuses etc but I like to keep things simple.
I have also spoken to others, eg. Derek from ABR, and they have said the chance of overcharging exits but is very small.
It shouldn't be so complicated!! Maybe I'm just making it harder than it should be.
Thanks for your help
Cheers Nifty.
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Follow Up By: Mainey (wa) - Wednesday, Mar 12, 2008 at 10:25

Wednesday, Mar 12, 2008 at 10:25
downtools,
You say:-> ""The only draw back I CAN see with the Ranox is that the fridge (or any load) cannot be connected directly to the battery while it's being charged. The Ranox guy said this could cause overcharging.""

Maybe this will cause some warranty problems also and not only for the Ranox ??

When the manufacturer states it "could cause overcharging" I would believe him, I guarantee they know the correct answer !!

Mainey . . .


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Follow Up By: ajr - Wednesday, Mar 12, 2008 at 13:31

Wednesday, Mar 12, 2008 at 13:31
downtools:

i beleive there is an updated version of the ranox now that has connections that may overcome this. is also a lot easier to install than the original that I have.

good luck

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