Batteries Only Accepting Low Amperage

[nhschneider]

Originally Posted by David B

Consider decent FLA's. Half the price, half as fussy, and last nearly as long (8 years or so). I keep doing the maths, and unless you have a special need, FLA's keep winning the $'s vs Ah's vs yrs race.

David B-
I have not done a spread sheet to actually analyze the reconciliation between FLAs, LiFePos and AGMs but it sounds like you have spent some time calculating the numbers. Even without accurate numbers, anecdotal information would suggest that your analysis is correct. The one factor that would be difficult to add to the formulae is the difference in weight, however, on my boat it's not a significant concern.

The Trojan T-145 FLA has a projected number of cycles at 1,200, assuming a 50% discharge. Many of the LiFePos claim up to 5,000 discharges, however, their discharge can be much lower. I have been quoted US$189 each for the T-145 (delivered to my boat) and LiFePos seem to start at about US$600.
On the initial blush, that seems to be very close to similar pricing. Granted, the FLAs will probably need more maintenance.

I'm sure this argument has been rehashed many times on this forum and many others so forgive me for the repetition.

Please accept my very best wishes for a happy, healthy and safe holiday.

[Stu Jackson]

Happy Holidays to you, too, and to all others.

Look, the $/ah have simply not changed much in the past few decades.

The only change I have seen (and maybe I missed some...?) is the NEW TECHNOLOGY that did not exists a "few decades ago." I think that's pretty understandable, don't you?

Therefore, it's pretty simple.

Here's a battery type analysis that a friend of mine wrote, and that I helped him edit, back in 1999 or so:

Detailed discussion of battery types by Jim Moe

AGMs, IIRC, were pretty new back then. Their limitations (i.e., short life if not fully recharged regularly) had not become apparent and weren't included in that article. Maine Sail has since repeated, often, those limitations. The "memo" is out, unfortunately many haven't "gotten the memo" as has become apparent all too often from my reading of this and many other boating forums about the limitations (compared to the advantages) of AGMs.

So, it wouldn't take much more effort to answer the question you raise here. You really don't have to reinvent the wheel.

Your boat, your choice.

Originally Posted by nhschneider

David B-
I have not done a spread sheet to actually analyze the reconciliation between FLAs, LiFePos and AGMs but it sounds like you have spent some time calculating the numbers. Even without accurate numbers, anecdotal information would suggest that your analysis is correct. The one factor that would be difficult to add to the formulae is the difference in weight, however, on my boat it's not a significant concern.

The Trojan T-145 FLA has a projected number of cycles at 1,200, assuming a 50% discharge. Many of the LiFePos claim up to 5,000 discharges, however, their discharge can be much lower. I have been quoted US$189 each for the T-145 (delivered to my boat) and LiFePos seem to start at about US$600.
On the initial blush, that seems to be very close to similar pricing. Granted, the FLAs will probably need more maintenance.

I'm sure this argument has been rehashed many times on this forum and many others so forgive me for the repetition.

Please accept my very best wishes for a happy, healthy and safe holiday.

[sailinglegend]

Originally Posted by nhschneider

... when I would start the genset, I would see about 120 amps of charge that would slowly drop to about 50 amps over the course of about an hour and ten minutes. Now I see initially about 100 amps, tapering off to about 50 amps in about five minutes......

This is a very good example of getting to "know your boat" and being able to detect when something is not quite right.

Yes this does look like repeated PSOC which has led to the batteries loosing much of their capacity. One sign would be that they won't last as long at anchor before dropping below 12.2v, and as observed by the op, they seem to get charged quicker because the current they will accept drops very quickly. This observation doesn't appear very often on this forum so it must be added to that "know your boat" list in your head.

A simple explanation is that because the capacity of the battery bank has fallen - maybe dramatically - the bank gets to absorption voltage much more quickly and the charger changes from a constant current device to a constant voltage device when the current accepted by the bank starts to fall off very quickly.

A good post by nhschneider.