Gel Batteries

Submitted: Friday, Mar 27, 2009 at 21:14
ThreadID: 67267 Views:3081 Replies:5 FollowUps:8
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hi, right ive just installed a 100ah gel sealed battery in my 2.7l prado as a secondary battery to run fridge etc, i also put in a trickle charger to charge it up when on power, we have just returned from a 3 week trip with no probs, charging from alternator/charger and running fridge etc, but... i am learning now that possibly the type of charger and the alternator could be damaging the battery? is this true and what should i be using/ doing to get the best from it? also i was told that i should not mix batteries, ie wet acid as the starter and gel deep cycle? i have installed a brain etc. Any help/ advice would be much appreciated, ta Chris
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Reply By: Member - Phil G (SA) - Friday, Mar 27, 2009 at 21:46

Friday, Mar 27, 2009 at 21:46
Unlikely/impossible that a Prado alternator will damage a gel battery. Worth checking the manufacturer's specs for charging your battery. Where is the gel battery installed? What brand/model no?

No problem mixing cranking and gel battery, provided you have an isolator that disconnects them when you turn the motor off.

" i have installed a brain etc." I am very happy for you :-))

AnswerID: 356661

Follow Up By: christoflam - Saturday, Mar 28, 2009 at 15:18

Saturday, Mar 28, 2009 at 15:18
yes brains are good, i have found, thanks for your reply, its a commander c12-100sdc.
Its in the back next to the fridge is a purpose made box, so a trickle carger may do it in? can you suggest a good make/model charger i can install with the battery?
thanks, chris
FollowupID: 624813

Follow Up By: Member - Phil G (SA) - Sunday, Mar 29, 2009 at 09:08

Sunday, Mar 29, 2009 at 09:08
Thanks. You'll get a better answer now. Sorry its not a simple one line answer.

All the replies below are correct! The trickle charger is out. No point in trashing a $500+ battery with a $20 charger.
I have looked up the commander website, and your model isn't listed, but I'll assume it is the same as the c12-100DG.

Gel charging info could only be found in the FAQs:
Charge with constant voltage automatic charger at 14.1-14.3V.
(No info given regarding float charge).
Limit charge current to 20amps for the 100Ah battery.
Charge to full capacity after use.
The battery should receive a monthly equalising charge.
"gel electrolyte batteries are not suitable for under-bonnet use."

So when it's hooked up to the Prado's alternator, the Prado's voltage (usually 13.8-14.2) is perfect. But you need to limit the charge current to 20Amps. This current limit is likely to be exceeded when the battery has been deep cycled and you then drive the Prado.

2 ways to limit current:
#1 The simplest way to do that is to use nothing bigger than 8Ga cable to the gel in the back. Given the length of the cable will be about 5 metres and the earth back to the cranking battery is another 5 metres, the wiring resistance will work in your favour. I assume you also have a fuse or fusible link at each end of this cable for short circuit protection. Measure the current with a ammeter when the battery is half discharged and being recharged by the alternator at say 2000rpm if you want to be sure you're not exceeding 20amps.
#2 The best way is to fit a constant voltage device in line. A friend had the same dilemma with a gel battery and bought an Arrid 20amp twincharge, and specified a maximum charging voltage of 14.2V instead of 14.4V. Arrid modified the unit for him.

240V chargers:
I can't think of any 14.2V chargers off the top of my head - most are 14.4V or higher. Common brands such as CTek will say they are suitable for gel batteries, but I'd expect they would still charge at 14.4. May not do any damage given its only 0.1V over.

I've used gels a lot in years gone by, and simply kept them charged with a 3-15V regulated power supply. I'd set it at 14.1V or therabouts and turn it off when the battery current had dropped to 0.5amp. My son took that when he left home, so I replaced it with a 20amp 13.8V regulated power supply that only cost $100 and that is what I use now for the small gels I still use.

FollowupID: 624888

Follow Up By: christoflam - Monday, Mar 30, 2009 at 08:06

Monday, Mar 30, 2009 at 08:06
cheers phil, thanks for your efforts ill give it a go!
Ta, Chris
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Follow Up By: Member - Mike DID - Monday, Mar 30, 2009 at 17:10

Monday, Mar 30, 2009 at 17:10
Applying an Equalising Charge to a Gel Battery is pointless - the purpose of Equalising is to stop dense acid settling at the bottom of the cell - that can't happen with a Gel.

If you apply a voltage that would casue a wetcell to gas strongly to stir up the acid, it would cause bubbles to form in the gel, which can't be removed.

"Equalisation process will not work for GEL Batteries."

FollowupID: 625152

Follow Up By: Member - Phil G (SA) - Monday, Mar 30, 2009 at 19:37

Monday, Mar 30, 2009 at 19:37
Thanks for pointing that out. I just cut it from the Commander battery website.
FollowupID: 625171

Reply By: Nomadic Navara - Friday, Mar 27, 2009 at 22:44

Friday, Mar 27, 2009 at 22:44
It's not the Prado generator that will stuff the battery, it is the trickle charger that will do that. The trickle charger is not regulated. When the battery reaches near full charge the output voltage of the charger will rise higher than necessary and boil the water out of the gel. Instant destruction if you give it some overcharging.

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AnswerID: 356667

Reply By: Sigmund - Saturday, Mar 28, 2009 at 07:31

Saturday, Mar 28, 2009 at 07:31
Your charger must have a gel battery cycle.
AnswerID: 356690

Reply By: RV Powerstream P/L - Saturday, Mar 28, 2009 at 18:08

Saturday, Mar 28, 2009 at 18:08
Gels aint Gels Sol.

What Gel as there are three types of Gel available Exide or European Spec Gel that charges @ 14.4V /20oC and floats @13.8V/20oC
GelUsa Specs that charge @14.1V/20oC and floats @ 13.5V/20oC.

Australian Gel that charge @14.7/20oC and floats 13.8V/20oC.

A trickle charger is supposed to hold charge at float voltage.

With a battery in the back of the car there is no way the normal alternator will damage the battery as normally voltage drop will stop that from happening.

First establish what Gel Battery you have then your trickle charger and apply the above.

If you have a constant load on the battery the trickle charger may never float it so will not damage it.

AnswerID: 356737

Reply By: Member - Mike DID - Monday, Mar 30, 2009 at 15:38

Monday, Mar 30, 2009 at 15:38
" i was told that i should not mix batteries, ie wet acid as the starter and gel deep cycle?"

That is a classic case of "a little knowledge is dangerous".

When you wire batteries in parallel, it's important that they're identical in type and age - but as soon as you put a Battery Isolator between them, they're no longer discharging in parallel !!!

What is important is that EACH battery is compatible with the Alternator's output voltage e.g. don't put a Gel battery in a Discovery with an Alternator output designed for Calcium-Calcium battery.

AnswerID: 357052

Follow Up By: jdwynn (Adelaide) - Monday, Apr 20, 2009 at 10:17

Monday, Apr 20, 2009 at 10:17
Mike, sorry to start oldish thread going again, but I know you're full bottle on this stuff. I have a year old 100ahr Remco AGM, hasn't had much use - I was looking to get another soon and wire in parallel. How bad is this given age. I certainly need second battery. Have you any suggestions? thanks JD
FollowupID: 628286

Follow Up By: Member - Mike DID - Monday, Apr 20, 2009 at 18:09

Monday, Apr 20, 2009 at 18:09
If you've looked after the battery, then after 12 months it will have lost little capacity.

Sealed batteries actually INCREASE their capacity during the first 30 charge-discharge cycles.
FollowupID: 628354

Follow Up By: jdwynn (Adelaide) - Monday, Apr 20, 2009 at 18:12

Monday, Apr 20, 2009 at 18:12
Sounds good, thanks Mike
FollowupID: 628356

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