Is this an ok alternative dual battery setup?
Submitted: Wednesday, Aug 12, 2009 at 11:42
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PradOz
For dual battery car setups, I know most people suggest that the starting battery only has the standard vehicles equipment on it (exception be a winch) and then all other equipment is on the second battery.
But I have also heard of another way as a suitable setup which an autoelec friend also seems to think is ok. So can anyone please explain why the following setup shouldn't be done, or is it ok and maybe just considered 'different'.
In this setup the vehicle has no winch. Accessories such as a car fridge and spotlights are attached to the vehicles starting battery. The second battery is kept free of accessories.
Suggested reasons being: if the vehicles main battery runs flat for example from the kids not shutting a door properly and the internal light being left on; or car stereo, headlights or some other item is left on; or some other fault runs the starting battery flat - the vehicle can be simply 'jump started' from the second battery (which to my thinking becomes just like carrying a spare battery except it is connected keeping it charged etc)
So can someone please explain to me the reasons for and against this type of setup.
If it ends up as an alternative suitable system setup I believe it would then come down to personal choice - is that right?
Also in this type of system - would you fit some type of item to the second battery simply for the purpose of being able to put some type of load on it at different times or is that not necessary?
Over to all the EO experts - thanks....
Reply By: leachy_9 - Wednesday, Aug 12, 2009 at 11:50
Wednesday, Aug 12, 2009 at 11:50
The issuse with this setup would be that cranking batteries are not suited for deep cycle application like running fridges.
Leachy
AnswerID:
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Follow Up By: Tenpounder (SA) - Wednesday, Aug 12, 2009 at 12:03
Wednesday, Aug 12, 2009 at 12:03
I agree. Running a cranking battery down and then jump starting the vehicle may get you out of that particular crisis, but it will still risk terminal battery damage to a cranking battery. The proposal actually uses the cranking battery as the storage battery, and the storage battery as a reserve cranking battery. Might be good for business, if you are an auto elec and your customers buy their batteries from you!!
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Follow Up By: Boobook2 - Wednesday, Aug 12, 2009 at 12:05
Wednesday, Aug 12, 2009 at 12:05
What Tenpounder said. Plus if you have all the load on the main battery and keep flatening it, then it won't last long. At least you will *need* that spare battery more :-)
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Follow Up By: Tenpounder (SA) - Wednesday, Aug 12, 2009 at 12:18
Wednesday, Aug 12, 2009 at 12:18
Incidentally, in terms of protecting the cranking battery, I use the following:
(1) wire low current essentials (eg UHF) directly off the battery;
(2) always turn off the ignition and remove the key whilst parked;
(3) turn off the interior lights at the switch.
I don't take the risk with toys like radios and CDs: I use a battery powered radio in
camp. It's asking for trouble to use the car as a power station while
camping
FollowupID:
646018
Follow Up By: Member - Fred B (NT) - Wednesday, Aug 12, 2009 at 12:19
Wednesday, Aug 12, 2009 at 12:19
As above... plus
your auxiliary battery will always be on "float" and no load. Battery's are designed to do some work from time to time.
If you have a decent fridge, then it should never flatten the aux battery completely, as it (the fridge) should cut out on low voltage anyway.
regards,
FollowupID:
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Follow Up By: olcoolone - Wednesday, Aug 12, 2009 at 14:16
Wednesday, Aug 12, 2009 at 14:16
Good quality deep cycle battery's will sit happily for 10 plus years on float with out loosing hardly any capacity, it's discharging and uncontrolled environments that shortens there life span.
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Follow Up By: Sand Man (SA) - Wednesday, Aug 12, 2009 at 19:31
Wednesday, Aug 12, 2009 at 19:31
Yes but the original poster did not specify that the second battery was a deep cycle one.
I agree that high current drawing equipment such as fridges should be run from a deep cycle battery source which are specifically designed to handle constant discharge/charge cycles.
Having a second battery in a dual battery setup purely as a backup for the primary starting battery does not make sense to me.
Bill.
FollowupID:
646060
Reply By: stevesub - Wednesday, Aug 12, 2009 at 12:22
Wednesday, Aug 12, 2009 at 12:22
How are you going to charge the second battery as it will self discharge over time.
We have 2 batteries with the standard vehicle stuff off the main battery and fridge, etc from the second battery. We have also used jumper leads to start the vehicle from the second battery a couple of times.
You will need some sort of charge controller to go between the 2 batteries - some are electronic, some are a combination of relays like we have (done before we bought the vehicle but it works). This is to isolate the second battery when starting the vehicle so you don't fry the wiring between batteries.
Stevesub
AnswerID:
378638
Follow Up By: Member - Graham H (QLD) - Wednesday, Aug 12, 2009 at 13:06
Wednesday, Aug 12, 2009 at 13:06
Why would you fry the wires and why would you use the system proposed by the poster
After all a Redarc and other isolators have the facility to connect both batteries to start the car.
I have a relay which when turn the key to "start"it automatically hooks them together as was done originally in the vehicle. I have 2 B& S cable between the two as you should and would fry the car before they let go.
All the accessories run off aux battery so you dont need to jump start which in todays computerised vehicles can be fraught with danger with one spike.
His system seems rather illogical to me
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Follow Up By: stevesub - Wednesday, Aug 12, 2009 at 13:20
Wednesday, Aug 12, 2009 at 13:20
In my Troopy which had a dual battery setup by a previous owner, it uses non-starter capable wires between the 2 batteries with a system of relays to isolate the batteries when starting or when the ignition is switched off.
I have had no experience with the latest electronic controllers as the system in my Troopy has never given a problem. My system was only ever designed to charge/isolate the second battery, never to start the vehicle from it.
If I was starting from scratch like PradOZ, I would be having the second battery run all my extras and have a electronic controller so either battery could be used for starting and both being charged at the same time.
Stevesub
FollowupID:
646027
Reply By: PradOz - Wednesday, Aug 12, 2009 at 13:10
Wednesday, Aug 12, 2009 at 13:10
I know of 2 setups like this that have been running for at least 3 or 4 years with no problems at all to either. They are charged from vehicle and have an isolator fitted. They have extra separate switches fitted that allow them to either jump the car from 2nd battery; charge the battery; also monitor the charge of both batteries. They also dont run the main battery down deliberately with the excuse the 2nd battery can get them out of a jam.
I think the set up is this way just as extra insurance for the time it happens. I am also not asking if you would also attach extras like separate
camp lighting etc for when you are actually camped. Its more a question if this set up is ok for simple items added ie: spotlights which wont always be left on with a vehicle off and a fridge which as others mentioned should switch off before the car battery anyway
Also note my last question in original post: "Also in this type of system - would you fit some type of item to the second battery simply for the purpose of being able to put some type of load on it at different times or is that not necessary?"
Thank you for your responses and opinions. I am just trying to find a reason(s) why it can or cant be done
Cheers....
AnswerID:
378646
Follow Up By: Tenpounder (SA) - Wednesday, Aug 12, 2009 at 13:33
Wednesday, Aug 12, 2009 at 13:33
Hi again. The most important thing is you've got us thinking, which has to be a good thing!
I suspect the key issue (for me, anyway) is whether
camping loads (fridge over several days, for instance) should be supplied from a deep cycle battery rather than a cranking battery. I know there are supposed to be compromise batteries that do both jobs, but there are differences of opinion here too.
I suspect the system you are talking about uses two conventional batteries, being cheaper to buy, and interchangeable. Others will go for AGMs etc which changes the equation.
Thanks for your contribution.
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646028
Reply By: olcoolone - Wednesday, Aug 12, 2009 at 13:12
Wednesday, Aug 12, 2009 at 13:12
The way your auto elec said to do it is the way emergency vehicles do it to ensure they can always start the vehicle if the starter battery goes on the blink.
This depends on the application but for 4x4's we always run everything of the auxiliary battery as axillary battery's are usually deep cycle and the main emphasis is not to flatten the start battery.
Emergency vehicle we do the other way unless stipulated by the customer.
With a 4x4 the chances of running a starter battery and axillary battery flat at the same time if wired correctly is very slim.
AnswerID:
378647
Reply By: kiwicol - Wednesday, Aug 12, 2009 at 17:49
Wednesday, Aug 12, 2009 at 17:49
Hi, I have this set up on my GQ Diesal Patrol, and have been using this system for 25 yrs. I only use 2 cranking batterys and have them hard wired together with an anderson plug to disconnect the second battery when i pull up for the nite. I run every thing of the starter battery including fridge, sterio, lights, phone, and shower. I also have a winch running through an isolation switch which connects to both batterys.
Every 4-6 months i swap batterys from side to side, and i have been averaging 3 yrs per set of batterys. I only use century overlanders. I have now purchased a 25 amp c-tek charger to see if i get longer use from the batt. I also use a christy generator when camped for long periods.
I swear by this system as its very hands on which keeps you up to date with what is happening with your batterys, and also no electronics to let you down when
camping on your own. The only problem i have had is i have forgotten to disconnect second batt when stopping for nite. To charge starter batt i disconnect second battery while driving to fully charge battery. I have also never been let down with fried wires, flat batterys or any other problem.
Cheers Col
AnswerID:
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Reply By: Robin Miller - Wednesday, Aug 12, 2009 at 19:53
Wednesday, Aug 12, 2009 at 19:53
I use a setup a bit like that PradoZ
I use only 1 main battery to keep weight down , and have a tiny second battery that can fit in your hand and which can start the car if used correctly.
2 points to keep in mind , The main battery should be capable of some level of deep cycle capacity. I currently use a Centruy Overlander , previously an Exide Orbital - both good units.
2nd point is that if the main battery just goes flat , then it takes little charge to be enough to restart the car , espically if its a petrol.
A 10 pack of AA's will do the trick , but currently I use a lithium motor cycle battery which fits in the palm of you hand but can deliver some 200 amps.
Normally you connect your small battery up for a couple of minutes and let it put energy into your flat main battery before clicking the go button.
In my case this setup drives a winch as
well as everything else.
AnswerID:
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Follow Up By: Wok - Friday, Aug 14, 2009 at 08:17
Friday, Aug 14, 2009 at 08:17
Hi Robin,
Interested in your Lithium Motorcycle battery......link pls?
I have been looking @ harvesting Emolis from DC
tools to do this job...but a "ready-made" sounds good :)
Thks...eng hoe
FollowupID:
646327
Reply By: tonysmc - Thursday, Aug 13, 2009 at 19:25
Thursday, Aug 13, 2009 at 19:25
PradOz don’t change your autolec he knows what he is talking about, however I believe he just didn’t explain the setup
well. I have been using this setup for years and IMHO it is the only way to go.
The whole idea of a dual battery setup is that you run your accessories and still be able to start your car. I think we all agree on that. The way this set works is you connect EVERYTHING to your 1st battery (as if you only have one battery). Whether you want to use Starter, deep cycle or AGM it doesn’t matter. Then with your 2nd battery connected with whatever system you prefer (redarc, solenoid, etc) you connect ONLY the starter motor main wire, not even the smaller starter solenoid wire.
Your ignition is still going through you 1st battery which is also running everything else in the vehicle. You only need enough power in this battery to operate the starter motor solenoid, not the actual starter motor. If you do happen to flatten this battery completely you only have to clip a small wire or a jumper lead between the positive terminals, the solenoid kicks in and away you go.
I hope this all makes sense,
Cheers Tony.
AnswerID:
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