Would this little AGM be any good?

Surfpath

To cut to a small portion of a very long story.....

I have an expensive Yamaha 6kw generator that's been sitting at the dealer for 13 months (Vic knows much of the story). I wont get into the generator story, too depressing. However... when it was dropped off at the dealer I mentioned the starter battery needs periodic charging to keep it happy. A few months later I repeated this advice.

Short cut to today: I asked one of the mechanics if they did this charging & I did not get a positive answer (was told that 'it is being charged now'). 10 minutes later another dealer mechanic said yes they did this monthly (avert eyes, look around). Ie they lied, they did not do anything.

So, even if this little AGM is being charged now, what are the chances it will be ok?

Here is a link to a very good spec sheet for this exact model. I am sure when I dropped it off it would have been 100% SOC. So at 12 months of shelf life it says 64% (it's probably been at 75-83 degrees). Is this cause for concern? If they manage to fix the genny, will the battery be good to me for any length of time?
-SP

inetdog

Re: Would this little AGM be any good?

Surfpath wrote: »

To cut to a small portion of a very long story.....

I have an expensive Yamaha 6kw generator that's been sitting at the dealer for 13 months (Vic knows much of the story). I wont get into the generator story, too depressing. However... when it was dropped off at the dealer I mentioned the starter battery needs periodic charging to keep it happy. A few months later I repeated this advice.

Short cut to today: I asked one of the mechanics if they did this charging & I did not get a positive answer (was told that 'it is being charged now'). 10 minutes later another dealer mechanic said yes they did this monthly (avert eyes, look around). Ie they lied, they did not do anything.

So, even if this little AGM is being charged now, what are the chances it will be ok?

Here is a link to a very good spec sheet for this exact model. I am sure when I dropped it off it would have been 100% SOC. So at 12 months of shelf life it says 64% (it's probably been at 75-83 degrees). Is this cause for concern? If they manage to fix the genny, will the battery be good to me for any length of time?
-SP

The main reason that AGMs can tolerate longer times off charge than floating batteries is that they have much lower self-discharge currents.
But, like any lead-acid battery they are vulnerable to sulfation, especially if they spend a long time below 80% SOC.
Since your battery has probably been below 80% for about five of those 12 months, I would expect it to have lost some capacity.
The good side is that I do not see any way that it could have lost more than about 36% of its capacity to sulfation, and you may be able to recover some of that by careful treatment.
A couple of problems there though.
1. The typical warranty "end of useful life" criterion is 80% of the original capacity, so in that sense it may well be "dead", even though it could still have a lot of useful life left in it.
2. If, for example, you end up with 64% of the original amp-hour capacity, you may need to scale back the maximum charging current of the alternator or other charger that is servicing it to avoid putting too much current through it. (The maximum charging current for a battery is often expressed as a fraction of the 20 hour amp-hour capacity number, C₂₀.