Gel Batteries

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

Chris,
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.

Cheers
Phil

cheers phil, thanks for your efforts ill give it a go!
Ta, Chris

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.

From http://www.ozcharge.com.au/OC-SW121210.html
"Equalisation process will not work for GEL Batteries."

Mike,
Thanks for pointing that out. I just cut it from the Commander battery website.

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

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.

Sounds good, thanks Mike