Hi Graham:

Heat and usage, along with the type of usage, and the type of batteries is what eventually leads to their demise.  There are only so many charge-discharge cycles stored in a battery and the more of those cycles used over a give time frame will hasten their "consumption".  Proper charging and battery maintenance also impact batteries and varies depending on the type of battery.  I think that if you had good service for 2.5 years in hot conditions with frequent use of flooded lead acid batteries such as your Trojans, that is about all you can expect.  Frequent charging, minimal discharging, careful maintenance etc will yield greater longevity.  I have Trojans aboard my boat and I find that it is a constant battle to keep the water levels topped up in the heat of the Caribbean. I think the Trojans battery cap design is not the best.  I have to add significant amounts of distilled water every month.  When I leave the boat on the hard, I have solar panels trickle charge them, but still have the caretaker plug the boat in for 6 hours one a month for a better top-up and also service the water level every month.  I only use the boat for about 3 months a year, and with this regimen I get about 4 years from a set of batteries.  Sad but true, the heat, the cycling, the motion etc, all take their toll.

Sincerely, 

Gary Silver

s/v Liahona 

Amel SM Hull # 335

On the hard in Antigua