Dual battery set-up

Submitted: Tuesday, Apr 22, 2008 at 12:46
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Hi all

New to the forum. I am in the process of putting together a dual battery set-up for my TD Lux. I have done my research but have a couple of further questions. I intended to use a Redarc isolator with my system to charge the crank and aux batteries. I will be running mainly only one fridge (50l Waeco) and maybe a fluoro or two for camping. The maximum we would stay is two days without any driving. Most of the time we would explore around the area for around 2 - 3 hours.

Is this the 'best' system for my requirements?

If I run a AGM Fullriver battery (same 120AH) as my aux battery, what should I use as my crack battery?

I was hoping not to have to install the aux battery under the bonnet due to excessive heat from the turbo and size of battery. My dog often rides in the tray (Canopy). Can I install the battery in the tray with affecting the dog? Does in need to be vented some how?

Thanks in advance
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Reply By: Mainey (wa) - Tuesday, Apr 22, 2008 at 13:16

Tuesday, Apr 22, 2008 at 13:16
Forget about the "best" system they are used in long term camping use, settle for the redarc as your not doing any long term camping and a redarc battery isolator is a reasonable low cost method.

Nothing wrong with a 120ah AGM Deep Cycle for the use you intend.
Put it into a plastic battery box in the tray with the dog - will have no hassles as they don't spill.

Use nothing less than "battery cable" to connect to the redarc !!

You ask "" what should I use as my crack battery?""
What's wrong with the present Cranking battery ???

Mainey . . .
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Follow Up By: TWJ - Tuesday, Apr 22, 2008 at 17:48

Tuesday, Apr 22, 2008 at 17:48
Mainey

I was only looking at replacing the crank battery because I was under the impression that it was better to have similar batteries in the dual battery set-up (charging?). If this is not the case then I will run with the current crank battery and add the AGM battery to the system.

So no hazardous gases are released while charging with an AGM battery? If that is the case then I will put it in the tray.

Would I be better to get a HGL or DC AGM Fullriver battery?

Could you recommend any battery places in Perth for Fullirver batteries?

Cheers for the advice everyone


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Follow Up By: Mainey (wa) - Tuesday, Apr 22, 2008 at 20:41

Tuesday, Apr 22, 2008 at 20:41
The Fullriver DC is a Deep Cycle AGM battery
(not HGL which is a Cranking battery)
Ummm, now your teasing me... what suburb do you live?

Mainey . . .
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Follow Up By: Member - joc45 (WA) - Tuesday, Apr 22, 2008 at 21:37

Tuesday, Apr 22, 2008 at 21:37
Check Challenge Batteries in Osborne Park for prices on Fullriver. 'Twas a couple of years ago I checked, but they quoted quite competitive prices.
Gerry
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Follow Up By: TWJ - Tuesday, Apr 22, 2008 at 22:30

Tuesday, Apr 22, 2008 at 22:30
Mainey - I am out near the hills.

So it is better to go the DC rather than the HGL?

joc45 - cheers will give them a call tomorrow

TWJ
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Follow Up By: Mainey (wa) - Tuesday, Apr 22, 2008 at 22:38

Tuesday, Apr 22, 2008 at 22:38
TWJ,
definitely get the Deep Cycle battery (not HGL)

Contact number for Challenge 9446 6122

Mainey . . .
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Follow Up By: Member - Mike DID - Wednesday, Apr 23, 2008 at 11:35

Wednesday, Apr 23, 2008 at 11:35
"TWJ posted:
I was only looking at replacing the crank battery because I was under the impression that it was better to have similar batteries in the dual battery set-up (charging?)."

That's a myth perpetuated by dealers who want to sell you two batteries instead of just one.

Both batteries have to be compatible with the voltage put out by the Alternator - if you install a Calcium-Calcium battery on an alternator putting out 14.4 volts it won't charge fully - whether it's the second battery or the only battery.
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Follow Up By: bigjohn1 - Friday, May 02, 2008 at 17:08

Friday, May 02, 2008 at 17:08
i use an AGM battery for my camper and its 12v 100ah.I just got it for $299 with a 2yr warranty.Best thing i ever got and the cheapest I know.I feel you got to see experts in this and the guy i got it from really knew his stuff.
check out his site.
www.allpurposebatteries.com.au
bigjohn.
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Follow Up By: Mainey (wa) - Friday, May 02, 2008 at 21:43

Friday, May 02, 2008 at 21:43
John,
it's definately not the "cheapest" - but yes, it may in fact be cheap...

Mainey . . .
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Reply By: KSV. - Tuesday, Apr 22, 2008 at 13:30

Tuesday, Apr 22, 2008 at 13:30
I use KISS method. Connect two identical semi-deep cycle batteries in parallel without any isolator at all. Proven to be the best possible design – it like to have twice bigger battery, it crank so happily it is not a joke. If I stop for an hour or so I do not bother to do anything, but if I camp and plan to use battery for whatever reason I disconnect main battery from body and keep it fully charged. If in the morning I cannot start from second battery (never happens as yet), then I disconnect second battery, connect main, start vehicle and connect secondary back. Always guaranteed to start car, no voltage drop, no extra cabling around and nothing extra to brake. Only disadvantage that does not bother me at all I need to remember to disconnect battery and connect it back.

Serg
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Follow Up By: Mainey (wa) - Tuesday, Apr 22, 2008 at 14:18

Tuesday, Apr 22, 2008 at 14:18
Serg, there's nothing KISS about it, because as you say, you HAVE to be there to remember to DISCONNECT and Reconnect the two batteries.
Sure you say it suits you, but it's a problem if you miss disconnecting the battery only just once, you WILL end up with two flat Cranking batteries and if it happens in the bush your stranded, maybe even dead and the lousy few $$ saved is not worth the hassle.

However. if you want to camp long term with a Cranking battery to run the fridge the Cranking battery will NOT last as long as an AGM Deep Cycle battery and will NOT charge as fast as an AGM battery either.

An AUTOMATIC isolator system is fool proof as it safeguards the Cranking battery by keeping it fully charged, and will allow automatic recharging of an AGM Deep Cycle battery by the Alternator.

Mainey . . .
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Follow Up By: Member - joc45 (WA) - Tuesday, Apr 22, 2008 at 14:47

Tuesday, Apr 22, 2008 at 14:47
Inclined to agree with Mainey.
The Redarc is a good-value battery isolator. It's a good balance between "the best" and too bog-simple.
And mounting your AGM away from the engine bay heat is better for long life.
But if you're electrically-inclined and can wire a circuit board, Oatley Electronics have a neat 80A battery combiner kit (kit K227) for $22, which just needs a box to put it in.
Even better, it can be easily modified to become a low-voltage cutout to stop you running the battery too low;
ie, buy one as the isolator and one for a cutout.
It uses a voltage sensor circuit to kick in or out a relay. When idle, the combiner _Affordable_Storage_Drawers.aspx almost zilch current, as it uses a bi-stable relay, which only _Affordable_Storage_Drawers.aspx current during changeover from on to off and vice versa.
Gerry
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Follow Up By: KSV. - Tuesday, Apr 22, 2008 at 14:52

Tuesday, Apr 22, 2008 at 14:52
Mainey,

Some points. I am not using cranking batteries, but “mixed” type that is closer to deep cycle. They perfect for cranking because they a bit of oversized (always use biggest what physically can fit) and they working in parallel. Secondly I do not have fridge and not planning to buy one, as least for a while. Also I do not camp with car stationary more then 2 days. And last, but not least, I do not have any issue with voltage dropping. I do not believe any claims about “zero voltage dropping” from primitive device and reckon that more then few lousy $$ would required to solve problem properly. And if not solved it would lead to premature battery failure. Loose-loose situation.

Forget to disconnect it just once? How about forgetting to put oil back when changing it? Or forget to put air-filter back? Consequences much severe because at worst with flat battery I can start my car by pushing it.

My main reason to have two batteries is for bigger capacity and winching rather then running fridge for long period, thus my solution is perfect for me. If one plan to use extra battery to run fridge, that I reckon that using step-up charger and completely isolate fridge battery from main one is much more appropriate solution.

Cheers
Serg
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Follow Up By: Mainey (wa) - Tuesday, Apr 22, 2008 at 16:38

Tuesday, Apr 22, 2008 at 16:38
Serg,
why use two "mixed" batteries when one Cranking battery will do the job, or as in my case one 6+ year old Deep Cycle battery is used as a Cranking battery, but it's correctly charged by the "primitive device" installed.

If you check with knowledgeable people who understand 12v batteries you WILL be advised that Cranking batteries are recommended for winch power, because of the extra high amperage drain they are designed for.

As to your method of charging your fridge battery... it's your (expensive) choice, but not mine.

Mainey . . .

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Follow Up By: Crackles - Tuesday, Apr 22, 2008 at 22:09

Tuesday, Apr 22, 2008 at 22:09
Serg I reckon you're on the right track but to make your system foolproof all you need is an inexpensive low voltage disconnect device to run your lights & fridge through, eliminating any chance of not being able to start the car in the morning.
I run 2x130 ah deep cycles together full time,(No start batt) this way I can use 160 amp hours & yet still have 50ah in each battery avoiding damage due to deep discharge & still have plenty to start.
This also avoids the pitfalls of charging different size or constuction batteries.
2 big batteries, LV disconnect & wiring $600. Can't get much simpler than that for 3 or 4 days of charge without restarting the car.
Cheers Craig........
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Follow Up By: Mainey (wa) - Tuesday, Apr 22, 2008 at 22:43

Tuesday, Apr 22, 2008 at 22:43
Crackles,
there is no direct correlation between Amp Hours (AH) and Cold Cranking amps (CCA)

There is no way you would accurately know how many AH's you have used or have remaining !!

......... OR

Can I just simply ask you what *technical instrument* you use to know you have used 160ah and have 50ah's remaining ??

Mainey . . .
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Follow Up By: KSV. - Wednesday, Apr 23, 2008 at 10:36

Wednesday, Apr 23, 2008 at 10:36
Mainey,

I been research battery topic for quite a while and experimenting with different set-ups before I have came to what I use now.

There is no such thing as “specially design cranking” battery. Starting battery in fact no more then bastardized cheap version of “normal” lead-acid batteries known as “deep cycle” one. To achieve more cranking amps and reduce cost they develop thinner plates, thus they can pack more of them in the same space achieving more amps because amps directly related to surface of plates. To make plates thinner (and cheaper) they drastically reduced usage of lead in plates, but instead use specially developed paste. It is true that “cranking” batteries produce more amps for the same size of battery (remember – more plates = more amps) and they are cheaper and smaller for CCA given, but we have to pay for this. Such batteries have two main disadvantages that in my eyes make them absolutely useless for 4WD applications. First they not tolerant at all to deep discharge – if such thing happens paste get detached and fall to bottom ultimately making short circuit and killing battery. It is not even necessarily to all banks fail to make battery useless – one fail and it is dead. On this fact alone I would not use cranking battery in winch application. Second fact also related to usage of this paste – such batteries not like shaking much – again paste gets detached and it doomed. Therefore in my opinion such batteries only good for suburban cars.

There is nothing wrong in usage of deep cycle batteries for starting. They pump slightly less amps *FOR THE SAME SIZE*, because they use lesser and much thicker plates made from lead (less plates = less amps). Answer is simple – install upsize battery. Or even better two of them running in parallel. I do not use “cranking” battery even in my passenger car – have bigger sized deep cycle one. Yes, it is more expensive, but in long term it pays itself by much longer life and heck, I do not pollute our land with unnecessarily big numbers of used batteries. Also they much more robust and easier tolerate abuse.

I can accept that my setup is not for everyone - some have amnesia for example. So when I will eventually develop one, I probably will install an isolator. As for my method of charging fridge battery – probably it is a bit more expensive, but it does not suffer from voltage dropping and with proper setup guaranteed to charge supplemental battery fully even if it totally different kind of. Plus supplemental battery can be installed in cargo area (or even better can be made easy movable with fridge) without necessity to run thick expensive and potentially hazardous cable and without any negative consequences.

Also it is possible to figure out how much AH left over pretty accurately by using high-precision voltmeter and take into consideration battery temperature.

Cheers
Serg
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Follow Up By: Crackles - Wednesday, Apr 23, 2008 at 17:42

Wednesday, Apr 23, 2008 at 17:42
"there is no direct correlation between Amp Hours (AH) and Cold Cranking amps (CCA)"...... Mainey I never suggested there was ???? As I said I have deep cycle batteries & the amp hour rating is printed clearly on the side (130ah each) The amounts I used were hypothetically not measured. (Maybe I should have expressed it as a percentage of available power)
The average punter on this site has a standard starting batt & a 2nd batt separated with various isolators usually around the 100ah size. Theoretically if they ran it flat the best they could get out would be 100ah where as the system I run can provide 50% more power, not discharge either battery below 35% and still be cheaper overall to install.
As I've said previously it has run a 73L fridge & 2 lights in up to 35 degree heat for almost 4 days without a solar panel or genny in sight. Like Serg, this system wont suit everyone's needs but is a proven option that works well.
Cheers Craig............
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Reply By: Sand Man (SA) - Tuesday, Apr 22, 2008 at 16:31

Tuesday, Apr 22, 2008 at 16:31
Serg,

The setup you use may be OK for your use, although personally, I believe you would be better off with two cranking batteries.

Crankers enable high current drain for short periods and as you would (should) be running engine when winching, you will not experience a problem.

TWJ on the other hand requires an auxiliary battery to run a fridge and Mainey has given sound advise on what is the best battery for this operation.

TWJ
A 120Ah AGM battery is well and truly sufficient for your stated needs.
As far a cranking battery (if you need a new one) I can recommend the Exide Extreme if you do some off-road travel. The plates are "heavy duty" and the battery is designed to handle "extreme conditions".

Bill
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Follow Up By: KSV. - Wednesday, Apr 23, 2008 at 13:02

Wednesday, Apr 23, 2008 at 13:02
Bill,

I have negative opinion and negative experience with cranking battery - see my replay above. I do not use them even in sedans.

Cheers
Serg
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Reply By: Bonz (Vic) - Tuesday, Apr 22, 2008 at 22:04

Tuesday, Apr 22, 2008 at 22:04
First off, almost every dog we have had has been self-venting. Sometimes in the car they were over venting.

Secondly the setup you have researched is a good one, I would look for a marine battery, they have both deep cycle and cranking capabilities. It can safely go in the back with the aforementioned self-venting pooch. Run the fridge and lights off the aux battery with 2-3 hrs run a day you wont have a zot of trouble. Even a 2 day camp with no driving would be fine from say a 100AH aux battery.

I wouldnt recommend just joining the two batts, if u have a fault you'll drain both. Use at least 35mm cable to join the two batts. Problem solvered
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Follow Up By: Nomadic Navara - Sunday, Apr 27, 2008 at 21:10

Sunday, Apr 27, 2008 at 21:10
Bonz

The only people who will tell you a marine battery is a combination of cranking and deep cycle styles is those who sell them. Those who know will tell you they are just ruggedised starting batteries with handles. If you require a deep cycle battery then get a proper one.

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Reply By: Nomadic Navara - Sunday, Apr 27, 2008 at 21:22

Sunday, Apr 27, 2008 at 21:22
TWJ

I posted this on another forum, it was written around charging a battery in a caravan. However this applies to your battery in the tray of your vehicle. In both cases the battery is at ambient temperature and not the elevated under bonnet temperature.

Charging deep cycle batteries in a van from the alternator in the tug is not very efficient. If you have a look at the charging voltages that your intended C-teck charger puts out you will see that the maximum voltages are in the order of 14.2 to 14.5 V depending on which type of battery you have it set up for. The manufacturers of multi stage battery chargers have established that this is the sort of voltage required to fully charge a deep cycle battery.

PeterD

The regulator in the alternator has built in temperature compensation. This reduces the charging voltage as the under bonnet temperatures rise. Warm batteries require less charge voltage than cold ones. If the charge voltage is not reduced with rising temperature then your vehicle battery would be overcharged and would boil dry. Most vehicle charging systems run at less than 14.0 V with operating temperatures - 13.6 to 13.8 V is a common range.

Whilst your warm vehicle battery is being well maintained, your van battery is is still cool and therefore will not be accepting much current. It will therefore not be charged much over 50% by the alternator. As I said earlier, you need a voltage higher than 13.8 V to charge a batty fully. 13.8 V is the level that battery experts have established is required to produce a maintenance float charge, not a replenishment charge.

If you need to charge your battery from the alternator in your tug, you require a battery booster or an inverter to drive your C-teck battery charger. These battery boosters do the same job as an inverter with a battery charger. There are a couple of boosters on the market. The older model is the Arrid Twincharge Battery Charger – It has a fixed voltage output which is too high for sealed batteries – I attribute the use of one of these to the demise of my last battery due to overcharging. The newer model is the RanOx Battery Booster http://www.ranox.com.au/401.html which incorporates a 3 stage charger – I now have one of these in my van.
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Follow Up By: Nomadic Navara - Sunday, Apr 27, 2008 at 21:29

Sunday, Apr 27, 2008 at 21:29
I don't know how it happened but my signature ended up in the body text instead of the end.

I also forgot to add that the updated model of the RanOx battery booster incorporates sensing circuitry that switches the unit on as the alternator starts to charge and off when it stops. This saves having to spend $100 plus on a battery isolator as well as the booster. (This may be switched off if you already have an isolator.)

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Follow Up By: KSV. - Monday, Apr 28, 2008 at 08:17

Monday, Apr 28, 2008 at 08:17
Hi Nomadic Navara!

“The regulator in the alternator has built in temperature compensation.”

I never hear about this – sounds quite odd to me considering that regulator actually sits inside alternator and later one can get much hotter then “underbonet air” because of load. Plus batteries have finite efficiency and also get hotter when charged or discharged with quite enough current. Could you please provide little bit more info on this? Otherwise I completely agree with your point – it is impossible properly charge remote battery without “step-up” charger.

Cheers
Serg
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Follow Up By: Member - Mike DID - Monday, Apr 28, 2008 at 08:32

Monday, Apr 28, 2008 at 08:32
Putting the temperature sensor in the Alternator has some benefits -

- It protects the Alternator by reducing the charging voltage and hence the current into the battery as the load increases. It diverts more current to the load as demand increases.

- It allows faster charging of the battery without overcharging - immediately after starting it puts out the Absorption voltage to replace the used charge quickly, then reduces voltage to the Float voltage when the Engine and Alternator heat up to avoid overcharging. It's a basic 2-stage charger without using current sensing - based on a typical driving pattern.


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Follow Up By: Member - Mike DID - Monday, Apr 28, 2008 at 08:34

Monday, Apr 28, 2008 at 08:34
Plus also -

- One less wire to install, to break, to be wired in incorrectly during a repair.
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Follow Up By: Member - Mike DID - Monday, Apr 28, 2008 at 08:38

Monday, Apr 28, 2008 at 08:38
"Otherwise I completely agree with your point – it is impossible properly charge remote battery without “step-up” charger."

- unless you use an AGM battery - they can be charged fully at 13.6 volts.

- I won't be debating it - if you disagree, contact the manufacturers and tell them to change their data sheets (then try to convince me my tests didn't really charge the battery fully at 13.6 volts)
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Follow Up By: Member - bushfix - Monday, Apr 28, 2008 at 09:20

Monday, Apr 28, 2008 at 09:20
G'day,

the Arrid model I have is designed for sealed batteries. It has a max output of 14.1 V which just happens to be the the max charge voltage of my Apollo AGM. Works well so far.
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