Dual Battery Systems

Submitted: Thursday, Jan 10, 2008 at 20:24
ThreadID: 53309 Views:2086 Replies:7 FollowUps:3
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Hi All
I was looking for recommendations for a dual battery system to suit my 2004 GU Patrol. I plan to run a 3 way fridge and a winch from it. Is there any brands to avoid or other helpful ideas about dual battery set ups out there?
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Reply By: raunchy - Thursday, Jan 10, 2008 at 20:43

Thursday, Jan 10, 2008 at 20:43
Hi Donald,
Most will do the job depending on what you are doing, the main factor being hte life of the battery. The more expensive like the AGMs and some Gels will handle discharging regularly and last longer, but you must at least have a deep cycle or marine battery otherwise you will not get more than a year out of the battery. Also you say 3 way fridge, 3 way fridges are not suitable for running off a battery while stationery as they draw a huge amount of current and draw it constantly. You would need an excessively large battery to cope overnight. However if you can run on gas overnight you would be OK, and as long as you switch to gas straight away and therefore may not need a dual battery.
As for the winch, you can only run this off a dual battery that is designed for cranking also, such as an orbital, marine or similair, in most cases you would run the winch of the main battery and have the engine running. The majority of dual battery systems will not allow enough current flow to let the second battery assist but htere are a few. ideally you would need to connect the second battery directly to the first to allow it to assist the winch. If your engine is running then in most cases you will have enough power to winch out of most situations with just the starter battery.

AnswerID: 280831

Follow Up By: Member - Mike DID - Friday, Jan 11, 2008 at 17:11

Friday, Jan 11, 2008 at 17:11
"The more expensive like the AGMs and some Gels will handle discharging regularly and last longer, but you must at least have a deep cycle or marine battery otherwise you will not get more than a year out of the battery."

The plate construction (thick=deepcycle, thin=starting) are totally independant of the electrolyte storage (wet, gel, AGM) so you don't have to choose between AGM and Deep Cycle.

You can get AGMs as Deepcycle or as Starting.
FollowupID: 545357

Follow Up By: raunchy - Friday, Jan 11, 2008 at 23:07

Friday, Jan 11, 2008 at 23:07
Agreed, that is why I stated Deep Cycle or Marine as they have thicker plates. This is independent to the construction. Sorry if the comment may have been misinterpreted.
AGMs and Gels in my experience do last longer than plain wet cells in the environment in question.

FollowupID: 545445

Reply By: Andrew from Vivid Adventures - Thursday, Jan 10, 2008 at 20:48

Thursday, Jan 10, 2008 at 20:48
Just to add to Ray's comments, there are a lot more things that are worth considering than just the battery type.

There are articles under "Electrics" on the left, and there are advertisers on ExplorOz like Derek Bester from ABR whose system I have been using successfully for a few years.

There is a lot to think about.

AnswerID: 280832

Reply By: Sand Man (SA) - Thursday, Jan 10, 2008 at 21:26

Thursday, Jan 10, 2008 at 21:26
I am of a different opinion, although never having experience with an electric winch.

I would run the winch off the starter battery (with engine running of course). The reason being the winch draws heavy amperage for a relatively short time and a starting battery is more suited to this type of use.

As for the three way fridge, I wouldn't bother installing an auxiliary battery. Three way fridges running on 12 volts are very marginal in efficiency and as you are only running them while travelling in an attept to maintain a consistent temperature, again you can use the starting battery as you wouldn't (shouldn't) be depleting the battery voltage with the engine running. A short stop wouldn't drain the battery down that much.

A compressor type fridge is an entirely different situation and a deep cycle auxiliary battery becomes much more practical.

That's my thoughts anyway.


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AnswerID: 280845

Reply By: keith & louise - Thursday, Jan 10, 2008 at 21:28

Thursday, Jan 10, 2008 at 21:28
hi Donald
do not run a 3 way fridge of a battery. it will destroy it in days. the winch is a complicated decision. winches draw huge amounts of current and will damage a deep cycle battery very quickly, but can also damage an alternator just as fast. a typical alternator is designed to supply 80A for a duty cycle of 10-20%. a typical winch draws around 300A continuous. meaning if you need to winch for more than one pull you could damage your starting battery and alternator at the same time. the best idea is to use a high quality marine battery as they will have a high CCA and Ah rating and when winching the dual battery wiill regulate the current from the alternator to the axillary battery to minimize the possible damage to the alternator.

AnswerID: 280846

Follow Up By: Member - Kiwi Kia - Friday, Jan 11, 2008 at 07:33

Friday, Jan 11, 2008 at 07:33
Hi Keith,
Do you have any practical experience of a winching operation damaging an alternator ?
FollowupID: 545241

Reply By: Willem - Thursday, Jan 10, 2008 at 22:31

Thursday, Jan 10, 2008 at 22:31
I run two 700 CCA cranking batteries through a simple solenoid and through an on On/Off dash switch. The winch cable heads for the positive on the main cranking battery and I only connect it when I want to use the winch.

Both batteries are now 4 years of age and the aux battery runs a Twozone Engel when I am travelling. Its all good and works well.

I wouldn't run a 3 way fridge for all the reasons mentioned above.

AnswerID: 280869

Reply By: Mainey (wa) - Thursday, Jan 10, 2008 at 23:48

Thursday, Jan 10, 2008 at 23:48
Can you change the plan...?

If not, for some of the reasons mentioned, run the WINCH off the CRANKING battery, not the Deep Cycle or Accessory battery and for security reasons only connect the Winch to the battery on the day when its most likely to be required with a simple on/off switch or 'wing nut' to (+) battery post.

To expect a 3 way to run successfully off a battery with-out the engine charging the battery for more than a few hours is far too risky.

Change the fridge or only run it on gas when parked for a few hours.
AnswerID: 280888

Reply By: Member - Steve Y (NSW) - Friday, Jan 11, 2008 at 14:29

Friday, Jan 11, 2008 at 14:29
What we do with the three way is run it on 240 to get it cold before we go, I have a seperate loom from the starter battery for this fridge while traveling. Now I can use the deep cycle as well as I have two seperate looms for that battery but I use the start battery just to level things out. it also help the regulator get a static current draw, IE, It always knows what it needs to provide - which is heaps these days. But you could just as easy use your second battery, up to you. They do work OK on 12 volt but as mentioned realy use the power, 7-10 amps so you need this direct connection else you'll melt your standards vechile lighter connection. When you stop for fuel etc you'll be OK but any longer than an hour and you will need to get the gas going and for that you need to take it out of teh truck. it's not a good idea to run gas in the vechile. Also, you need your three way on gas to be perfectly level (Spirt level - level!) if you can do all that it will workfor you. I also have a waeco CF50 that we use to freeze food and to be perfectly hounest uless camping for a week or so don't take the gas fridge with us prefering to use the compressor type running of the 100amp deep cycle.

Then your winch issue is as described, you will kill it if you draw the amps needed to support the winch. I have a hand which so I'll leave that answer to the experts.
AnswerID: 280987

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