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-   -   Dual Battery System Danger (http://www.jeepgarage.org/f157/dual-battery-system-danger-72362.html)

robbie 03-03-2014 07:09 AM

Dual Battery System Danger
 
I plan to install a dual battery system in my WK2 diesel Overland to power a refrigerator for off-road trips.
However the Jeep/Chrysler Technical Support Manager advised me against this citing possible damage to the electronic management system which manages the alternator.
I have seen a couple of posts from down under where the use of dual battery systems on the Grand Cherokee has been reported.

Has anyone who has installed a dual battery system on a Jeep GC had any problems?
:confused:

Peter.T 03-03-2014 07:38 PM

Re: Dual Battery System Danger
 
Quote:

Originally Posted by robbie (Post 985315)
I plan to install a dual battery system in my WK2 diesel Overland to power a refrigerator for off-road trips.
However the Jeep/Chrysler Technical Support Manager advised me against this citing possible damage to the electronic management system which manages the alternator.
I have seen a couple of posts from down under where the use of dual battery systems on the Grand Cherokee has been reported.

Has anyone who has installed a dual battery system on a Jeep GC had any problems?
:confused:

I have installed a couple of dual systems on MY13 Grand Cherokees, one for me and one for a friend. In both cases I have used a DC to DC charger to:

a. keep the second battery divorced from the Jeep system and
b. to make sure that the second battery does in fact achieve a correct and full charge.
A second battery with a solid link to the main cranking battery via a VSR will only ever get around 85% charge.

I also fitted a solenoid with a manual switch which will link both batteries if the need ever arose that more starting current etc. was required.

The batteries were fitted under the passenger seat. However this will only accommodate a battery if the car in not Quadralift. It requires some modification of the plastic receptacle under the seat and it is quite tight.

I can provide photos and further information if needed.

Pete

John47 03-04-2014 02:11 AM

Re: Dual Battery System Danger
 
I use a dual battery system in my 2012 Laredo, to power a 12v fridge and other accessories.
I fabricated a slide in module for the cargo area and when going away the module is slotted in, with the fridge, the 80AH deep cycle battery, table and chairs and lots of other stuff.
Like Peter T, i use a DC-DC charger mounted on top of the battery box, and connected with Anderson plugs and 6 B&S cable back to a Piranha DBE 140S battery isolator mounted down beside the main battery.
I installed the Piranha in the first few days of ownership and it has remained connected for 20 months and 53,000K with no issues.
The module has been in and out probably 10 times and each time the setup works perfectly, charging and maintaining the accessory battery. Some pictures in this thread: http://www.jeepgarage.org/f73/second...s-53030-2.html
A number of Aussie owners have installed similar setups with different VSR units.
The only issues I have read about have been with VSR units that have the cut in threshold too high to be compatible with the WK2 system voltage. Fitting programmable VSr units have solved that issue.
With the proper research and components you'll be able to enjoy cold beers on the track.
John

robbie 03-05-2014 08:53 AM

Re: Dual Battery System Danger
 
My thanks to Peter.T and John47 for the response.

I propose to use a CTEK D 250S DC/DC charger for the job with a loose battery box in the rear of the jeep.

Regards,
Rob

Peter.T 03-05-2014 03:45 PM

Re: Dual Battery System Danger
 
Just a cautionary note on the use of DD to DC chargers.

Some vehicles use Variable Voltage Alternators that are on the vehicle CANBUS system. The output can vary from approx. 12.3 to 15 Volts depending on driving conditions and as such it is possible that the DC to DC charger may not in fact be activated from the alternator output. 12.3 Volts is below the switch on threshold of some chargers.

The 2013 onwards JGC is in this group and to really achieve correct DC to DC operation the charger should have a Low Voltage input. This is a trigger which is activated by an ignition connection and ensures that the DC Charger is on all the time that the vehicle is running.

There are several points in the JGC from where this ignition feed can be taken, the cig accessory socket in the rear quarter is probably one of the easiest as is the socket in the front box under the radio. I believe that it can be also taken from the windscreen wiper motor feed but can't confirm this.

Zenith 03-10-2014 11:05 PM

Re: Dual Battery System Danger
 
Peter,
I intend to use a Redarc BCDC1220-ign battery charger, that I understand is compatible with the variable output of my MY14 alternator to keep my caravan fridge supplied with sufficient voltage, which it is lacking at the moment and intend mounting it in the van next to the van house batteries fed through the anderson plug connections.
Do you have any experience with fridge voltage control for caravans with house batteries?
Rgds, Zenith.

Peter.T 03-11-2014 12:00 AM

Re: Dual Battery System Danger
 
Hi Zenith,

Certainly I can try and assist with any questions you have. I would need to know if you are using a 3 way fridge or a compressor drive in order to advise you correctly. I assume that you are not changing anything relating to the fridge wiring although if its a 3 way fridge there are some things that need to be considered.

Pete

Zenith 03-11-2014 01:32 AM

Re: Dual Battery System Danger
 
Pete,
Tku for the quick reply.
I have a 175ltr 3 way 2 door fridge in the van with 2 house batteries in the van.
I have recently upgraded the gauge of the battery to fridge wires to minimise the voltage drop.
At present, the car is putting out 13V most of the time, with 12.6V at the fridge when not turned on and 11.6V when turned on.
Can you pls advise what other info you need?
Rgds,
Zenith.

Peter.T 03-12-2014 02:48 AM

Re: Dual Battery System Danger
 
Hi Zenith,

I need to know what you are trying to achieve.

The 3 way fridge genre is grossly inefficient on DC and that is why most are wired DC only to the tow vehicle and then switched over to gas when stationary. On DC they draw approx. 20 Amperes which will flatten a 100 Ah battery in around 2.5 hours.

So if you are intending to run the fridge off your two house batteries you will have a very limited refrigeration time.

If you are trying to charge the house batteries from the tow vehicle then a DC to DC charger is required to achieve correct charge. Normally there is no direct connection from the house batteries to the fridge but I don't know how your van is wired.

Sorry if I misunderstand your requirements. Can you please clear it up for me.

Pete

Zenith 03-12-2014 03:14 AM

Re: Dual Battery System Danger
 
Pete,
Tks again for the reply.
The fridge is wired to receive power from the van house batteries only while connected to the car, via an Anderson plug while travelling. Currently, the car battery is fitted with a Redarc isolator to protect it when stopped. My aim is to get sufficient voltage to the fridge while we are travelling so as to maintain fridge temp. I am considering removing the existing isolator from the car and installing the Redarc DC to DC charger [includes own isolator] in the van to boost the house batteries and in turn provide a constant 13.8 volts to the fridge while travelling. Do you know of any better alternative solution to this issue?
Many thanks,

Rgds,
Zenith.

Peter.T 03-12-2014 03:54 PM

Re: Dual Battery System Danger
 
Hi Zenith.
Now I understand.

Yes this will work and is similar to the way we wire our caravans at Bushtracker.

The DC to Dc charger will provide the correct charging algorithm and you will get a full bulk charge cycle whenever the car is running with the van attached. I assume that you have AGM batteries in the van and so you will get a bulk voltage of about 14.4V top up.

Pete

Zenith 03-12-2014 10:57 PM

Re: Dual Battery System Danger
 
Thanks for your advice Thomo.
Much appreciated.
Rgds,
Zenith.


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