Deep Cycle Batteries

Submitted: Thursday, Feb 13, 2003 at 10:26
ThreadID: 3354 Views:2056 Replies:4 FollowUps:1
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I own an 80 series L'cruiser on gas and petrol. I also tow a caravan quite alot and because of the space under the car bonnet I have installed a Trojan DSB on the drawbar of the c'van.
I have run two pairs of 8g cables from the car battery via a solinoid to a large diameter Utelux type socket at the rear of the car. One set of these cables goes straight to an Electrolux 3way fridge in the caravan. The other pair of cables connect to the DSB on the drawbar and in turn feed the internal lights in the caravan, the radio and an Engle fridge.
While the ignition on the car is turned on and the engine running all electrical equipment is running and when the engine is off the Electrolux fridge is isolated but the remainder of the equipment is being fed from the Trojan battery which is also isolated from the car.
I have not fully tried out the system and would like to have any comments that may be forthcoming.
I must add that the road lights and electric brakes are all fed via a seperate socket at the rear of the car. Both pairs of auxillery cables are connected directly to the main battery of the car.
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Reply By: desert - Thursday, Feb 13, 2003 at 13:26

Thursday, Feb 13, 2003 at 13:26
Sounds OK, but be aware that once the solenoid is energised ie when attemrting to start the car (ignition on), for a split second, full cranking amps are going to try and feed from the second battery, this may fry the solenoid contacts and/or over heat the wiring. Might be better to switch the second battery via a manual switch after the car has started? However, you need to remember that if you forget about it overnight - two flat batteries. Also, charging sensing is still only going to sense the original battery and will prevent full recharge of the second battery as the alternator cannot "read" it clearly.
AnswerID: 13033

Reply By: David - Thursday, Feb 13, 2003 at 21:07

Thursday, Feb 13, 2003 at 21:07
I basically agree with desert...
What you've done is good, but you will probably never FULLY charge your second battery with that setup. ("Smart chargers go through 3, and occasionally FOUR stages of charging ie: BOOST-ABSORBTION-equalisation- and FLOAT--- all at different voltages)
Actually by fitting the battery somewhere other than the engine bay, you'll probably dramatically extend the life of the battery. Batteries hate being flattened, but they also HATE excess heat. I had a mate who moved the battery from under his bonnet to his boot and tripled the time he was going between battery changes (I wouldn't go that far as you'd need humongous cables- but anything you can do to keep your battery cool helps...)
Do you have solar or some other way of charging- if so accept the fact that the alternator will NOT fully charge the battery, even after driving all day, and try to top it up fully when and if you can. Even if you occasionally have 240v available and top it up with some other charger, it would help. It does not do a wet cell battery any harm at all to have a good "overcharge" occasionally, as long as you watch the eletrolyte level.
AnswerID: 13066

Reply By: raybates - Thursday, Feb 13, 2003 at 22:47

Thursday, Feb 13, 2003 at 22:47
Hi David & Desert,
thank you for the advice on my setup.
I do not have a solar panel connected to my system but I have been considering one.
While travelling I carry a 700w gen set and at one stage I had a battery charger fitted in the circuit that used to charge the battery when the genset was running. The genset usually ran after we had stopped for the night and the DS auxillery battery would run the fridge after we ritired for the night and supplied power for the auxillery lights after the genset had been shut down.
I no longer have a battery charger in the circuit but am reconsidering installing one after the comments that you made regarding charging rates from the vehicle alternator.
If either of you know a system that I can install that will allow full charging to take place I would be very much oblidged
AnswerID: 13077

Follow Up By: Rum Pig - Saturday, Feb 15, 2003 at 16:50

Saturday, Feb 15, 2003 at 16:50
hi raybates we are having a dual battery set up fitted the set up is rotronics web site ts 4wd centre advised this is the best suited to what we need eg running a 12 v slide on {3 year warranty}
FollowupID: 7729

Reply By: Member - Nigel - Thursday, Feb 13, 2003 at 22:54

Thursday, Feb 13, 2003 at 22:54
I use a LEAB charger on my camper trailer and also for topping up my aux battery in the vehicle. It's a bit dearer than most, but is waterproof and can cope with vibrations, will cope with generator power between 170-240 volts), etc. The australian distributor is

For me the charger was much cheaper than premature failure of my 3 deep cycle batteries from undercharging.
AnswerID: 13079

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