Battery Isolator

Submitted: Saturday, Apr 30, 2005 at 21:01
ThreadID: 22527 Views:3569 Replies:14 FollowUps:27
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Hi Group
Im thinking of fitting a Rotronics 3 stage charge Isolator 3ST12CFV on my Landcruiser to charge my aux,and the 2 house batteries in my off road van have spoken to rotronics and it sounds like what I need to keep the batteries up to there peak,has any body got any experience with the rotronics system good or bad.

Thanks
Darrell
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Reply By: nick riviera - Sunday, May 01, 2005 at 09:39

Sunday, May 01, 2005 at 09:39
Hi Darrell have you done a search in the forums (archive&active) for past experiences or problems?

Rotronics have great gear and a good website have you looked at it rotronics great place to get all the specs for comparisons with other manufacturers systems.

We have a simple MH10 unit in a HZJ105 2001 model that was installed by the previous owner the Qld government, I will be taking it with me if i ever sell the 100.

I highly recommend the rotronics product and knowhow. If they tell you that what you need then ....that is what you require to do the job.
AnswerID: 109043

Reply By: Darrell Lewis - Sunday, May 01, 2005 at 10:12

Sunday, May 01, 2005 at 10:12
Hi Nick
Yeah thanks for that I should of done a search before I posted there are heaps of postive replys in the forums have also been to Rotronics web site will be doing the install myself this week.
I have used a solinoid for years with just the truck aux battery and its been fine but since hooking up the van with its 2 80amp batteries via a anderson plug im finding the batteries dont get charged past around 70-80% and dont last long when you start powering things up in the van I also have solar panels on the van roof for charging during the day..

Thanks
Darrell
AnswerID: 109046

Follow Up By: Mainey (WA) - Friday, May 06, 2005 at 22:41

Friday, May 06, 2005 at 22:41
Darrell,
as you say a solenoid, either a simple one or a really smart one, won't fully charge auxilliary batteries in your situation....

When you wire the Rotronics system use at least 2B&S size wire to your Aux batteries, as it will eliminate almost all voltage loss caused by any thinner wire, I replaced the original brand new Rotronics wire when I installed my own system and saw a difference in the voltage level at the far battery.
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FollowupID: 366681

Follow Up By: drivesafe - Saturday, May 07, 2005 at 06:55

Saturday, May 07, 2005 at 06:55
OK Mainey, can you give a reason why a solenoid won’t fully charge a battery better than a pure electronic controller.

There is virtually zero voltage drop across the contact of a relay or solenoid while every electronic device has some voltage drop even be it very small in some cases but that still means that unless the pure electronic system has a step up circuit then the relay system is MORE likely to charge the batteries to a high voltage.

The trick to getting an auxiliary battery to as high a charge as a vehicle is capable of charging it, is to install heavy cable. Once that is done, it won't mattery what type of controller you use.
You far better off spending big money on the cable and making the cost of the device secondary.
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FollowupID: 366699

Follow Up By: Mainey (WA) - Saturday, May 07, 2005 at 10:36

Saturday, May 07, 2005 at 10:36
Ds,
I’ve posted
(Quote)…won't fully charge auxiliary batteries in your situation.... (end quote)

Darrell has posted above;
(Quote)…I have used a solenoid for years …. since hooking up the van with its 2 x 80amp batteries …. I’m finding the batteries don’t get charged past around 70-80%...(end quote)

I believe the reason is simply because Darrell is using 'different' batteries, and Redarc themselves do specify to “use identical batteries to their customers”, as per the email to me from redarc, clarifying the situation of mixing different batteries in the same dual battery system, as I have posted below.
As you know dissimilar batteries will accept charge at different rates, ie, charge and also discharge at different rates.
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FollowupID: 366720

Follow Up By: drivesafe - Saturday, May 07, 2005 at 14:46

Saturday, May 07, 2005 at 14:46
Mainey, in your post, you were saying that you agree with him and thats why I asked you the question.

And again, If Darrell was having problems before he up grades his charge control system, he will still have problems once he up grades.

Mainey, you yourself recommend the use of thicker wire.

Without doing anything else, just increasing the size of the cable will resolve most if not all his charging problems.

If Darrell fits a new charge control system first, the first trip he does will tell him he then has to up grade the cable.

If you can’t get the current to the rear batteries in the first place you are won’t be able to charge them properly without allowing for an unrealistic amount of charging time and if the cable is to small, you will never charge the batteries.

Cheers
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FollowupID: 366737

Follow Up By: Mainey (WA) - Saturday, May 07, 2005 at 17:59

Saturday, May 07, 2005 at 17:59
Ds,
Yes I believe the majority of problems relating to lack of fully charged aux batteries are caused by the lack of quality in the wiring systems, that is the sole reason why I stated in my first post to Darrell;

(Quote)When you wire the Rotronics system use at least 2B&S size wire to your Aux batteries, as it will eliminate almost all voltage loss caused by any thinner wire. (end quote)

And yes I fully agree with you in your post above, but, I don’t believe his present solenoid will get anywhere near fully charging the system he proposes even with thicker wiring.
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FollowupID: 366755

Follow Up By: Darrell Lewis - Saturday, May 07, 2005 at 18:29

Saturday, May 07, 2005 at 18:29
Mainey
No I am using all the same batteries Exide Extreams ie start ,aux and 2 in the van.the only bat fully charged is the start the rest are at around 70-80%
Darrell
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FollowupID: 366758

Follow Up By: Mainey (WA) - Sunday, May 08, 2005 at 10:48

Sunday, May 08, 2005 at 10:48
Darrell,
I have thought when you posted (Quote)...to charge my aux, and the 2 "house batteries" in my off road van... the van with its 2 x 80 amp batteries… (end quote) I have believed you had different types/styles of batteries as you had given them all different names eg; start, auxiliary and house batteries, yes, my own mistake, however below is the relevant information for your Exide “Extreme” starter batteries, compared with Exide “Endurance” Deep Cycle batteries, as they are both from the same manufacturer you can see the difference without scepticism.

The major difference is in the weight and the acid capacity of each battery and the fact that Exide specify their starter battery as, ‘Cold Cranking Amps’ and their Deep Cycle batteries as ‘Amp Hours’.

N70EX, Exide Extreme.. rated; Heavy Commercial battery
620 Cold Cranking Amps
25 Kilogram
5 litre acid capacity

ED6, Exide Endurance.. rated; Deep Cycle battery
85 Amp Hour
28.5 Kilogram
6 litre acid capacity

The DC battery has less number of plates however they are much larger, hence the large weight difference and the extra one litre of acid, both batteries are similar in appearance.
As can easily be seen on the Exide website the ‘Extreme’ is a good starter battery however it is built differently to a DC battery, because it is built to do a different job.
However I could not find on the Exide website where the Extreme is rated as 80 amp?

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FollowupID: 366812

Follow Up By: Darrell Lewis - Sunday, May 08, 2005 at 18:54

Sunday, May 08, 2005 at 18:54
Mainey
The Exide Extreme is also classed as deep cycle 80AH and will take continues deep discharge and recharge as well as a start battery check with exide IO have had the 2 in the truck for around 12 months with one 5 week trip into the WA desert region with a 40 L engel in the truck and they preformed fantasticly its only since in hooked up the new trakmaster van that I have had problems charging the aux and the van batteries

cheers
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FollowupID: 366867

Follow Up By: Mainey (WA) - Monday, May 09, 2005 at 19:36

Monday, May 09, 2005 at 19:36
Darrell,
I am not suggesting you are incorrect, all I’m doing is posting the relevant information direct from the manufacturer’s website!
This further information can also be read there, it is also self explanatory!

Where can I use a deep cycle battery?

Deep cycle batteries can be used wherever the battery is continually discharged for an extended period of time, and then recharged:
1. In boats for powering trolling motors, fish finders, depth finders, lighting and other accessories.
2. In motor homes, travel trailers, and tent campers to run accessories, radios, TVs, fans, REFRIDGERATORS, etc.
3. In outboards and sailboats to power lights and accessories.

What are "Deep Cycle" Batteries?

These batteries are designed to provide "deep cycle" power - making them very different from ordinary car batteries. Starting a car requires a high amount of energy for a short period of time (about 5 seconds). Only a small amount of the battery's capacity is used. Once the engine starts running, the battery is recharged quickly by the alternator, which carries the basic electrical load.
On the other hand, DEEP CYCLE batteries supply a relatively low amount of current for a long period of time. DEEP CYCLE batteries are specially designed to power electric trolling motors and other electrical accessories in boats and RVs. Unlike ordinary car starting batteries, they can be run down and recharged (deep cycled) repeatedly with minimum loss of capacity.

When a car starting battery is deep cycled, it loses capacity very rapidly and in some cases has lost its useful capacity in 50 cycles (discharges and recharges) or less. These limitations make car batteries a poor investment when used for marine and RV deep cycle applications.
A single DEEP CYCLE marine/RV battery will outlast 2-4 car batteries.

Are "Deep Cycle" batteries constructed differently?

Yes!
DEEP CYCLE BATTERIES, are specially designed with denser active material and thicker plates to withstand deep discharge-recharge service. They are also reinforced by envelope and glass mat separators to reduce shedding of the active material and damage from the jolting vibration of a boat on choppy water.

CAR BATTERIES, on the other hand, use porous active material and thin plates so that high-amp energy can be quickly delivered for maximum starting power. Repeated cycling weakens the positive plates and makes the active material shed from the grids. Thus, in repeated deep discharge-recharge applications, the capacity of the car battery drops below desired levels in about 50 cycles.
Car batteries are not built to withstand the heavy buffeting experienced by marine batteries. They are simply designed to do a different job.
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FollowupID: 367007

Follow Up By: Darrell Lewis - Monday, May 09, 2005 at 21:07

Monday, May 09, 2005 at 21:07
Mairney
This is what Rod Street from Rotronics thinks about Exide Extreme batteries..
WHICH DUAL BATTERY FOR YOUR 4WD?

Recent articles in two popular 4WD magazines were confusing and provided 4WD owners with misleading and ambiguous information.
It is important to choose not only the correct charge isolator system, but also the correct battery type for applications where the second battery is used for winching, plus the normal fridge 12 volt power supply.

Two popular batteries ideal for use with 4WDs fitted with electric winches are the Century MP600 and the Exide Extreme. Both are composite paste batteries, designed for heavy duty use in 4WD or marine applications.
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FollowupID: 367022

Follow Up By: Mainey (WA) - Monday, May 09, 2005 at 21:52

Monday, May 09, 2005 at 21:52
Darrell, we just gotta stop meeting like this L0L
Tis good to be able to communicate with the actual thread instigator without getting argumentative L0l...

(Quote) It is important to choose not only the correct charge isolator system, but also the correct battery type for applications where the second battery is used for WINCHING, plus the normal fridge 12 volt power supply.
Two popular batteries ideal for use with 4WDs fitted with ELECTRIC WINCHES are the Century MP600 and the Exide Extreme. Both are composite paste batteries, designed for heavy duty use in 4WD or marine applications. (end quote)

Darrell, as I read the quote you have posted, and yes, I agree with it 100%.... the correct battery to use with a winch is definitely a starter battery and NOT a DC battery, as indicated the quote is referring to a battery which is used primarily with an ELECTRIC WINCH. Deep Cycle batteries make bad WINCH batteries, but good fridge batteries, as is stated on the Exide website!

Eg; “….where the second battery is used for WINCHING…”
And also in the next sentence
“Two popular batteries ideal for use with 4WDs fitted with ELECTRIC WINCHES are the Century MP600 and the Exide Extreme”

Exide Extreme batteries have six refillable caps as used in conventional “wet cell” batteries, and not a cap free surface as used in sealed paste batteries… so I would not be predisposed to believe the quote, maybe Rod was “misquoted”
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FollowupID: 367033

Reply By: nick riviera - Sunday, May 01, 2005 at 10:57

Sunday, May 01, 2005 at 10:57
Go the solar panels :)

we just bought two KC80W for our camping needs, going to mount them on rhino racks on the cruiser. But i seem to be spending every day off playing withem in the back yard like a 10 year old, i still cant get over their usefulness.

cheers
AnswerID: 109049

Reply By: normc - Sunday, May 01, 2005 at 13:00

Sunday, May 01, 2005 at 13:00
Darrell, I've been going through a similar exercise as I'm about to put a multi battery isolator in my Hilux to charge 1 aux in the veh and 2 in the camper trailer. Added complication is that I plan on using AGMs on the trailer.

I've had long talks with Rotronics, Piranha and Redarc. Rotrocics recommend the same unit as you are looking at and from my discussion with Rod Street at Rotronics it sounds like it is the one. Costs $950 plus $290 for wiring harness (if you get it from Rotronics). Piranha say to use 2 of their 180 models. Redarc say to use 2 of their solenoids and a high power switch and set it up as two circuits; manually switching to chose which circuit is connected to alternator.

From that, I conclude that Rotronics is the only supplier with a system specifically designed to meet your (and my) needs, but it is also the most expensive.
AnswerID: 109058

Follow Up By: Mainey (WA) - Friday, May 06, 2005 at 23:09

Friday, May 06, 2005 at 23:09
normc,
Rotronics have a written warranty with their product, stating it will do the job you are asking of it, Piranha also have a written warranty stating their product will also work with your battery system. However unless redarc have changed their smart solenoid technology recently they actually specify ALL the batteries must be identical and that is the information they pass on to their customers.
Below is an extract of an email I received from redarc, you decide how to spend your own dollars, but first obtain qualified and relevant information to make that decision!

(Quote)
Mainey,
In our discussions with a large battery manufacturer it was commented that it is ideal to use two identical batteries in a dual battery system and therefore we pass that information on to our customers……..
We are updating our website and we will remove the confusion.
Thanks for letting me know.
Please let me know if you require further assistance.
Kind regards
Anthony Kittel
Managing Director
REDARC Electronics(end quote)
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FollowupID: 366687

Reply By: Darrell Lewis - Sunday, May 01, 2005 at 13:21

Sunday, May 01, 2005 at 13:21
hi Norm
I am under the impression that it dosnt matter what type of batteries you use I indicated to them that I will proberly change my van batteries at a later stage to AGM's I beleive that the AGM likes a fast charge better than deep cycle

My price was around the same as yours.
AnswerID: 109060

Reply By: normc - Sunday, May 01, 2005 at 13:49

Sunday, May 01, 2005 at 13:49
That's right. My understanding is that it sees 3 batteries and isolates them all from each other. Cranker, aux 1 (in vehicle) and aux 2 (2 batteries in camper connected in parallel to act as 1 battery). If this is your set up, the only ones that need to be the same are the ones in the camper as they are hard wired in parallel. From what I can find, the Rotronics is the only system that works like this.
AnswerID: 109063

Reply By: brett - Sunday, May 01, 2005 at 14:12

Sunday, May 01, 2005 at 14:12
Does this unit have some sort of inverter circuitry where you can adjust charge and float voltages indepedently for the different battery's? Had a look at the website and it didn't really say. If it's only switching the alternator between the 3 battery's it's awfully expensive at $950. For that money I'd want a 12V powered 3 stage intelligent charger with adjustable charge voltages for different types of battery's and even then it would be expensive at $950
AnswerID: 109065

Follow Up By: Wok - Monday, May 02, 2005 at 08:20

Monday, May 02, 2005 at 08:20
Brett,

I queried Rod about this point. The Rotronics system do not utilise DC-DC converters. He is of the opinion that the Alt Reg is sufficient as it controls 1 outout at a time. AFAICS it is important to select adequate cable size for the load & distance in each application to reduce cable losses.

I take any claims for [100% recharge] with a grain of salt where typical charge times and aH are not indicated. It will be interesting to see how this system copes with the reported alt trend of 2 stage regulation.
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FollowupID: 365869

Follow Up By: drivesafe - Saturday, May 07, 2005 at 07:23

Saturday, May 07, 2005 at 07:23
Hi Wok, provided you can get 13.8 volts or higher at a suitable current rate, to be supplied to a vehicle battery, AGM, deep cycle, cranking type or what ever, then there is no reason why you can not fully charge the battery to 100%.

If you read battery manufactures data, you may see things like for optimum charge, supply a charge voltage of 15 volts.

For the batteries that can take this higher charging voltage, the advantage is that the battery will charge quicker but if you read all the specs relating to the charging of these batteries, you will find that the minimum voltage required to still be able to charge the battery to 100% is 13.8 and as most vehicles supply between 13.8 and 14.2, at 14.2 volts you can get any battery charged to 102%.

The lower voltage of 13.8 just means that it will take longer to charge.
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FollowupID: 366700

Reply By: Darrell Lewis - Sunday, May 01, 2005 at 15:14

Sunday, May 01, 2005 at 15:14
Hi Brett
Yes I agree it is very expensive but from allthe feedback its the best on the market and does charge all the batteries up to there max.

Darrell
AnswerID: 109070

Reply By: Russ - Sunday, May 01, 2005 at 20:08

Sunday, May 01, 2005 at 20:08
Darrell,
I have a Redarc in my TDLC 04 model. Use it to run/charge a Blue Apple/Waeco HD battery 64amp. More than happy with its performance and was just over $300.

Russ
AnswerID: 109119

Reply By: drivesafe - Monday, May 02, 2005 at 10:53

Monday, May 02, 2005 at 10:53
Hi Darrell, to charge the batteries properly you have to fit heavy cables. Once you have fitted heavy cable, then can just about use any reliable charge controller / isolator and they will work properly.

If you concentrate on installing 6 B&S or greater size cable you should be able to recharge your batteries in a reasonable time frame and charge them as well as any alternator will be able to charge them.

What you will have to make sure of is that your vehicle’s alternator can provide the current required to charge 4 batteries at once.

There is a lot more to charging every thing, the way you want it to be done, than just fitting a suitable controller. But if you fit the correct cable in the first place then you can then go any way you want.

Cheers.
AnswerID: 109195

Follow Up By: Darrell Lewis - Monday, May 02, 2005 at 10:59

Monday, May 02, 2005 at 10:59
I have battery cable between the aux and start battery 50 amp cable from the solinoid to the anderson plug then 8mm from the anderson to the van batteries the alternator is rated at 120 amp I feel this should be ample.

Cheers
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FollowupID: 365892

Follow Up By: Mainey (WA) - Thursday, May 05, 2005 at 01:30

Thursday, May 05, 2005 at 01:30
Darrell,
8mm is far too small for your purpose as I see it posted here....
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FollowupID: 366318

Follow Up By: Spade Newsom - Friday, May 06, 2005 at 01:35

Friday, May 06, 2005 at 01:35
Interested in some comment.

Reading about the more soffisticated rotronics systems(fancy letters as mentioned above), one of the features is that an auxillary will be shut down if it's voltage drops below a specified level as a method of protecting the auxillary battery.

1. I would much prefer the battery to give its all for the team to keep my beer cold as long as possible. After all a deep cycle can handle the odd flogging especially for someone like me who only roughs it half a dozen times a year.
2. If the cut out settings don't run to plan than you could get an unexpected black out. Again, beer one - me nil. I have heard these cut out switches can and do play tricks. (Think I read it on a Collin Rivers article)

For most adventurers whether the battery has 120 recharges or 500 recharges is not the priority.

My humble conclusion.
Flash you beaut systems for hard core 12V users where 500+ recharges is an economic necessity and basic no nononsense systems for those whose cold beer requirements exceed battery life requirements.

Notice no tech speak.
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FollowupID: 366537

Follow Up By: Mainey (WA) - Friday, May 06, 2005 at 08:25

Friday, May 06, 2005 at 08:25
This information and annotations may clarify the situation!
Here we are talking about 95% Dis-charge of a battery!

Most quality built fridges today have a battery dis-connect system built into them which is generally set higher than 95% of battery Dis-charge, so the fridge would turn off well before the Rotronics system is activated.

This Rotronics system is state of the art and yes expensive, it is generally used where three or more batteries are used in larger motor homes or caravans where battery performance is paramount. The person who has this system will most probably also have a solar system to automatically recharge their battery bank, and not allow the batteries to get down to 95% dis-charged situation to turn off the fridge.

Low Voltage Protection;
A Red LIGHT on the Monitor, which is installed on the dash of the vehicle, will "Turn On", when the Auxiliary battery has discharged down to ..80%.. of battery capacity, nearly everyone, at this point, would do something to remedy their battery dis-charge situation, if it is a $29 solenoid or a Rotronics system is not relevant, eg, they would start their vehicle to recharge their batteries, so their drinks did remain cold.. L0L

The Red LIGHT will "Flash" and the Low Voltage Protection circuit will "Turn On", when the battery dis-charges further down to ..95% of it’s capacity, eg it has only 5% capacity, it is basically almost dead and the fridge will not be working anyway in a short period of time if allowed to remain connected.
The fridge will remain Off until the alternator OR the solar panel/s recharges the auxiliary battery. This system will AUTO RESET and the fridge will restart.

3ST12CFV operation;
The Main battery is recharged first, when the Main battery is " On Charge ", the isolator connects either the Auxiliary battery or the Caravan battery/s, as selected by the Auto Select Circuit for recharging and Isolates the Main battery from the Alternator and Vehicle Electrical System. The Auxiliary battery is Isolated when the Caravan Battery bank is selected. This ensures the maximum Recharge Current is supplied to the Auxiliary battery during the auxiliary battery recharge cycle. The vehicle auxiliary accessories are controlled directly by the isolator and will continue to operate.
The Auxiliary battery will be connected by the isolator once the Caravan battery bank begins to recharge. The Main battery is also tested by the isolator for State of Charge when isolated, and reconnected for further recharging as required to maintain full charge of the Main battery.
The Main battery, the Auxiliary battery and the Caravan Auxiliary battery banks are all Isolated, from each other, when the engine is "Off ".

Hope this information is understandable and constructive
no high tech words were damaged in their deletion or substitution
Mainey..
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FollowupID: 366546

Follow Up By: Spade Newsom - Friday, May 06, 2005 at 23:05

Friday, May 06, 2005 at 23:05
mainey,

you seem much more knowledgable than I and maybe you could enlighten me on the following.

I had a basic soledoid isolator and 70 ah ABC deep cycle fitted a year or so ago. Local auto elect supplied and fitted and runs fridge like a charm.

Looking now to add 12V to my trailer also. My plan is to parallel a 100 ah AGM (or maybe 2 x 50 ah AGM) via large guage cable and anderson plug to my existing auxillary. Also plan to connect small solar panel with voltage regulatorat say 5 watts to the trailer - not really to charge but to give a little trickle if not used for a couple of days.

Spoke to auto elect who said that would work with heavy cable, however disconnect the solar when the motor is on. Why? just in case, might harm the panel gut feeling. I of course don't want to have to remember to connect and disconnect the solar and also driving in the middle of the day seems the best time for solar to work.

In your opinion,
1. Will this basic system harm the solar panel if not disconnected.
2. Is mismatching different batteries a problem.
3. Will any of the trickle charge reach my in vehicle under bonnet auxillary.
4. Will attachinga solar of this size achieve any purpose.

Also considering banking 5 x 7ah deep cycles on the roof rack and also connect in parrallel. These little 7ah are great for pulling off the bank and setting up shower pumps, lights etc away from vehicle. Swap them over each day. Would also attach a 5 watt solar to this.

again
1. Is this fanciful or could it work.
2. Are the 7ah too small to parralel with main auxillary. significant mismatch in size.
3. Will any of the trickle charge from this set up get to the in-vehicle auxillary.

Your thoughts appreciated. (If you find answering such questions a nuisance please say so and I will stop bothering you)

Spade
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FollowupID: 366685

Follow Up By: Mainey (WA) - Friday, May 06, 2005 at 23:32

Friday, May 06, 2005 at 23:32
(Quote)My plan is to parallel a 100 ah AGM via large guage cable and anderson plug to my existing auxillary. Also plan to connect small solar panel with voltage regulatorat say 5 watts to the trailer(end quote)

Spade
In my opinion;
1. No
2. Yes, see my post follow up #366687 above
3. Not likely at only 5 watts
4. Not likely at only 5 watts
At only 5 watts you wont need a regulator!

and again
1. power would get there but it would be so dam small it would not be noticed
2. I would not use 7a/h
3. Not likely at only 5 watts

read information on the forum ...relevant to what you want to achive
and ask questions of the people with the same system you would like to install!

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FollowupID: 366691

Follow Up By: Spade Newsom - Friday, May 06, 2005 at 23:55

Friday, May 06, 2005 at 23:55
Mainey,

all batteries should be identical.
I assume this excludes the cranking battery.

spadenewsom
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FollowupID: 366693

Follow Up By: Mainey (WA) - Saturday, May 07, 2005 at 10:52

Saturday, May 07, 2005 at 10:52
spade,
technically, yes all batteries should be identical!

However, if you use the Rotronics independent system then the batteries in each area can be totally different because they are charged independently.
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FollowupID: 366722

Reply By: drivesafe - Monday, May 02, 2005 at 11:26

Monday, May 02, 2005 at 11:26
Hi again Darrell, 8 mm would be just OK for a single battery and then it would still add to the recharge time.

For two batteries in your trailer, you will be able to charge them but the time to get them fully charge will be quite significant.

8 mm cable is rated at about 100 amps ( depending on what brand of cable it is ) and this 100 amps is usually based on the constant current capacity of 1 metre of cable.

The distance you have will mean there will be a large voltage drop because of the current load needed to charge the two batteries.

You will probably find that at the worst load situation, you will be lucky to get 20 to 25 amps at around 12 volts.

Note you will still be able to charge both batteries but no matter what brand of charger / isolator you finally decide on, you will still have to allow a much longer charge time.

No charge controller can magically produce more current than is available in the first place.

The installation of heavy cable in the first place, can usually remove 90% of potential problems associated with dual battery charging systems.

cheers.
AnswerID: 109200

Reply By: normc - Thursday, May 05, 2005 at 08:20

Thursday, May 05, 2005 at 08:20
This is a description, taken from the Rotronics web site, of how their system works. It may help some of the technically minded to understand the system a bit better. Also, They supply a wiring kit (for $290) which includes 19m of the heavy duty cable they recommend, which should overcome the cable size problem mentioned by some posters.

"The Main battery is recharged first. The voltage is monitored at the Main battery by the 3ST12CF and when the Main battery is " On Charge ", the 3ST12CF connects either the Vehicle Auxiliary battery or the Caravan Auxiliary battery/s, as selected by the 3ST12CF Auto Select Circuit for recharging and Isolates the Main battery from the Alternator and Vehicle Electrical System. The Vehicle Auxiliary battery is Isolated when the Caravan Battery bank is selected. This ensures the maximum Recharge Current is supplied to the Auxiliary battery, during the auxiliary battery recharge cycle. The vehicle auxiliary accessories are controlled directly by the 3ST12CF and will continue to operate. The Vehicle Auxiliary battery will be connected by the 3ST12CF, once the Caravan battery bank begins to recharge. The Main battery is also tested by the 3ST12CF for State of Charge when isolated, [ during the auxiliary battery recharge cycle ] and reconnected, for further recharging as required, to maintain full charge of the Main battery. The Main battery, the Vehicle Auxiliary battery and the Caravan Auxiliary battery banks are all Isolated, from each other, when the engine is "Off ". The 3ST12CF Monitor will display which battery bank is "On Charge". The Test Circuit for the Anderson plug, will check the Anderson Plug for connection and the 3ST12CF will Auto Select from 2 - stage to 3- stage Charge Control.

The 3ST12CF Monitor incorporates a Main Only select switch, to allow Only the Main battery, to be charged if required, i.e. short run with the vehicle, stop - start etc. The main only switch also selects the Winch Control Circuit, [ if a winch is fitted ] and disconnects the auxiliary battery charge cycle, to protect the alternator from overheating and damage. Also included is a Vehicle Auxiliary "Boost" Select Switch to connect the vehicle Auxiliary battery for recharging i.e. the winch has discharged the vehicle auxiliary battery. This function will parallel the Caravan Auxiliary and the Vehicle Auxiliary batteries for charging. The 3ST12CF Monitor also incorporates a manual control push button, to restart the Auxiliary battery recharge cycle as part of the P.C.A.P. [ Peak Current Alternator Protection ] circuit. The circuit allows the full peak current output of the alternator to recharge the auxiliary battery without overheating the alternator.

The % recharge for a lead acid battery is 100%. The maximum % recharge for a sealed Auxiliary battery is 90%. For 100% recharge, use a 240volt/14.7volt 10Amp minimum output battery charger to provide battery maintenance -- refer to the battery specs.

This System is Guaranteed for 3 - Years and comes with a 3 - Year System Tech Support free call Telephone No.

This system is compatible with :

Solar panel/s fitted
240V/14Volt Battery Charger connected to the auxiliary battery
Generator/Battery Charger connected to the auxiliary battery"


AnswerID: 109760

Follow Up By: drivesafe - Friday, May 06, 2005 at 08:29

Friday, May 06, 2005 at 08:29
Hi normac, I think you might get a slightly different story if you read some of the data put out by the different battery manufactures.

This can take a bit of deciphering at times but basically most say ( including AGM makers ) that the optimum charge voltage is anything up to 15 volts while charging. This is obviously unobtainable in a conventional vehicle, but if you read up on the full charging characteristic of these batteries, nearly all of them can be fully charged to 100% if a minimum charge voltage of 13.8 is used and as most vehicle charge and operating voltage is between 13.8 and 14.2, there is no reason why a standard vehicle can not get all your batteries fully charged.

The advantage of a 15 volt charge is that it will fully charge the battery quicker and please note, the 15 volt charge level is primarily for AGM batteries. Wet cell deep cycle or cranking batteries can actually be damaged if this higher charge voltage is used for any length of time.

The one place most people fall short is as I post earlier, is by using too small a cable size when connecting batteries to the vehicles electrical system.

Thicker cable allows a high charge voltage to get to the batteries in the first place and thus gets the batteries charged quicker.

cheers.
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FollowupID: 366548

Follow Up By: normc - Friday, May 06, 2005 at 08:54

Friday, May 06, 2005 at 08:54
Thanks Drivesafe. My AGM is recommended for charge at 14.7V. I use this setting on my 240V 3 stage charger. After I have the vehicle system set up, I will still do battery maintenance using this charger when I get back from a trip. Apart from being sensible, it is recommended by Rotronics.

The problem with cable size for the layman is that there are at least 3 (I think) different size measures. I don't have a clue what it all means. My fridge manufacturer has recommended (and supplied for fridge connection)10mm2 (ie 10mm squared) cable. This cable is about 8mm thick and has heaps of small copper wires in it. Will I need something even bigger for the run to the trailer batteries via the Anderson Plug? The trailer manufacturer has supplied a 50 Amp Anderson plug. Is this big enough?
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FollowupID: 366551

Follow Up By: drivesafe - Friday, May 06, 2005 at 10:15

Friday, May 06, 2005 at 10:15
Hi again normc, if you are going to be charging one battery in your caravan or camper trailer, 10mm2 is fine is fine. I have 10mm2 laid through my 4by and use 50 amp Anderson Plugs to connect the cable to a camper trailer. I have 2 x 220 amp 6 volt deep cycle batteries in the trailer and the cable size allows the batteries to charge up at a fairly quick rate, this charge time still depends on battery usage prior to charging and the amount of the trailer is towed and batteries are able to be charged.
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FollowupID: 366567

Follow Up By: normc - Friday, May 06, 2005 at 11:19

Friday, May 06, 2005 at 11:19
Thanks, Drivesafe. Learning all the time. Came across a guy from the local 4WD Club the other day who has one of your Traxide isolators for his vehicle auxiliary. Used it to replace a solenoid which was giving him trouble. Said it works great.
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FollowupID: 366575

Reply By: normc - Friday, May 06, 2005 at 08:40

Friday, May 06, 2005 at 08:40
Hi Darrell,
Let us know if you install the Rotronics system and how it goes. Including the installation.
I've just got a temporary installation at the moment. AGM in back of Hilux, which I charge with 240V 3 stage charger. Waiting for Piranha and others to make battery cradle available for 05 Hilux so I don't have to get one made. The temporary set up will be OK until early July when we will be heading out on some longer trips.

Your feedback might help me in determining what I do at that time.
Thanks
NormC
AnswerID: 109976

Follow Up By: Darrell Lewis - Friday, May 06, 2005 at 16:29

Friday, May 06, 2005 at 16:29
Hi Norm
Will do Im still waiting for Rotronics to contact me as they were in the process of building my unit hope to install it as soon as it arrives heading off for a trip early June for 2 weeks so will give it a workout..

Cheers
Darrell
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FollowupID: 366624

Reply By: Truckster (Vic) - Sunday, May 08, 2005 at 00:39

Sunday, May 08, 2005 at 00:39
read Willems trip report, his Rotronics hasbleepitself.
AnswerID: 110252

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