Deep cycle batteries

Thanks Allyn, I will do the research

It seems most places only give 6 months on deep cycle batteries. It's a bit of a worry your measuring 15.2 volts with 2 dead cells, You should never charge the battery beyond 14.2 volts, the fact 2 cells are dead the voltage is probably even higher per cell than it should be. Follow 2 simple rules, never discharge below 10.5 V and never charge beyond 14.2V and all should be ok.

Wet cell "Equalizing" charge goes WAY past 14.2 volts!! More like 15.5 or 16 volts
Battery might still probably be stuffed if SG is low on some cells!!
Id be after a waranty replacement.
Never discharg below 11VOLTS- Not as low as 10.5!!!!

BTW
The voltage does depend on weather it is on "discharge" or not.
in other words under load or not. The more you flatten it, the sooner it will die PERMANENTLY!!!
If it is down to 10.5v OFF LOAD then it is VERY FLAT and you are wrecking your batery by discharging ot TOO MUCH!!!
I try not to discharg below 50% and batterys last a long long time.
Happy easter. Its nearly over!!!!

Yes 10.5 is very flat but without a load I still find it's relatavely safe, sure 11V would be safer, but how many people have no idea about these voltages and run them absolutely dead flat, then wonder why it didn't last too long. I'm curious as to what you mean by Wet cell "Equalizing". I use a float charger when recharging and have it adjusted to spot on 14.2V, and that gives a full charge, don't you start boiling after that? I can't imagine charging a battery untill it's terminal voltage read 16V.

Flash is right- Brett is too partly.....
Wet Cells do well to have an equalising charge occasionally-
Thats what a good computerised battery charger will do (such as the Plasmatronics PL20 solar controller and many similar smart chargers)
Basically it does a couple of things including bringing up "lazy" cells, reduces stratification in the electrolyte, and reducing sulphation.
It's too complicated to go into much here- borrow a decent battery book from your local library and you can read all about it IF you want.. but basically if you do it every month or so while watching the electrolyte level carefully-don't let it get too low- you'll do your battery a great favour.
Only a very simple charger uses a steady voltage for all stages of battery charging- still thats better than no regulation..
There are 4 stages to good charging..
Bulk (fast) absorbtion (slow) equalizing (occasional over charge) and float (usually the state to keep your battery in for best storage.)
As I said elsewhere though - you don't need to be TOO scientific for good battery life, just avoid
1 Deep discharge (the less the better)
2 Heat
3 Vibration
Also when discharged the sooner it's recharged the better.
There is some scientific evidence to suggest the Megapulse helps significantly with the sulphation (there will always be sceptics!!)
Cheers- hope this helps