Trojan Deep Cycle

Trojan are reputed to be the finest wet cycle DC's available, with a price to match. I would guess the one you are looking at will cost $250-300. At this price you could consider an "AGM" battery. A 100 amp Fullriver or Remco (both Chinese) will set you back around $250, or a Lifeline (USA) $350.

Conventional wet cell DC's will only accept charge at around 5 amps/hr which means you have to do a lot of driving each day to get them charged. They also only charge to about 80% capacity from and alternator. They need a solid charge from a 3 stage 240 volt charger (very expensive) to get to full capacity. An AGM on the other hand will accept a huge rate of charge. In testing my AGM (as scientifically as I could with a multimeter) it took 20 amps in 20 minutes from the alternator.

It's worth some thought.

Have a look here, it's a great site.

http://www.windsun.com/Batteries/Battery_FAQ.htm#AGM,%20or%20Absorbed%20Glass%20Mat%20Batteries

Also have a chat to the bloke at Federal Batteries in Sydney, they have a 1300 number in the yellow pages. He knows his stuff.

Good luck,

Jim.

Glenn. Have had 2 Trojan Deep cycles in my Cruiser for over 1 & 1/2 years & they work brilliantly. I have actually got rid of the starting battery & wired the two deep cycles in parralell. They run the fridge & lights for 4 days & still have enough to start the diesel. Many on this forum rag the deep cycle batteries stating they're too slow to accept charge, couldn't be used for starting & are not suitable for winching but on all 3 accounts in practice I've found this not to be the case. The Trojan is arguably the best deep cycle battery & in your system together with the solar charge circut would probably be ideal. (Trojan are highly recomended by WA Solar)
They have handled being shook up on the Cape, Simpson & Canning & that is what you pay the extra $ for. Cheers Craig...............

The AGM type of battery is certainly worth consideration.

However, the physical size may be an issue. I would replace my wet deep cycle battery with an AGM type (when it expires) if it wasn't too bloody big to fit in the cradle.

Brett

Charge rate is indeed governed by the internal resistance of the battery, but as deep cycle batteries have far fewer but thicker plates, their internal resistance is higher than that of a starter battery. The heat generated whilst charging thus limits their charge rate to about 25% of the amp/hour capacity (to about 60% charge) then to 10-15% thereon. In practice, heat build up is the ultimate determinant of charging rate and top quality charging systems use battery temperature monitoring to govern charge rate.

It is true that a deep cycle is unlikely to charge at a rate much over 5 amps from a conventional alternator/regulator, but this is because the voltage is really too low. For the same reason, conventional lead acid batteries (both starter and deep cycle) will not charge much beyond 70% from a standard car alternator/regulator system. Because of voltage drop, caravan batteries are more commonly limited to about 65% charge.

Many solar regulators will supply boost voltage as high as 15 volts, as will (smart) three-stage battery chargers. Both will bring a deep cycle battery to well over 90% charge.

So-called 'smart regulators' are obtainable for vehicle alternators (and i have had one on my OKA for years) but most are incompatible with computer engine management systems. They are very effective otherwise however. Mine will charge the OKA's 450 amp/hr battery bank at up to 100 amps. There are several suppliers of these devices in Australia.

Re water usage. A correctly charging deep cycle battery should use about a centimetre of water every 8-12 weeks in temperate climates. If less, it is probably being undercharged.

As with gel cells, AGM batteries have very low internal resistance. This enables them to charge quickly from as little as 14.1 volts. Their recommended float voltage is however lower than most (typically 13.2-13.3 volts) and there are reports of shorter than expected battery life in hot areas that is believed to be caused by this.

Further, AGM battery makers advise that the products should not be charged in parallel with standard batteries. Many people ignore this advice however.

Incidentally - most of the above re internal resistance and charging rate etc was described by Peukart in a paper written in 1897! (Anyone interested in Peukart's Law, drop me an email and I'll email you a copy).
Collyn Rivers

Glenn,

I have trojan 130 amp/hr deep cycle. Have just returned from cairns - darwin via gulf return with only good things to say about it. It didnt use any water ad handled the corrugations without any problems. I think i paid about $230 for it in cairns.

Cheers

Kevin