BFL13 wrote:
IMO the batteries are fine. You got them as good as they can get, and those SGs and resting voltages after differences are not especially significant. When the batteries really do go downhill someday it will be obvious.
It is very unclear what that particular 75 amper behaves like. I don't remember you saying it ever did 75 amps even for the famous 15 minutes before or after the mod.
I see Randy has his adjustable voltage version 75 amper up now. The owner's manual should be interesting. Maybe Randy can say what happens to the regular 4B 75's stages when you do the mod like why that 15 min is still there, etc. No problem with the PM3 so why is there with the PM4 mod?
I'm thinking perhaps you're a mind reader? Let me explain.
Like I said to Niner, I spent the whole day yesterday considering all the possibilities and data. And just as I would lean heavily toward the charger being the problem, something would make me suspicious of the batts. Half an hour later, I'd be eye-ing the pm with suspicious contempt. :)
I have been doing all my testing at my brother's place, and his neighbour has his own business working on boats and rebuilding engines, etc. So I decided to get his take on things. After explaining my whole dilemma, he did a load test on both banks, with a hand held gizmo with a heat element, and said the batts are fine. I asked if it was possible for the batts to seem fine, as far as accepting a charge, holding a charge, and handling a load/discharge, BUT be only capable of accepting around 45 amps during a 50-?% charge? He said no. So there's one persons opinion, at least. Then I considered taking the batts in somewhere to have them tested? But I'm not sure if that would help?
As for the pm4b, indeed, it has never gone above 46 amps output, pre or post mod, so I was becoming more and more convinced it was a 45 amp unit labeled as a 75 amper. I figured one way to figure this out was to check its input current, (Erinn had told me it should be about 9 amps), and I was getting impatient waiting for my new clamp-on AMP meter to arrive, so I powered up the pm off the near full bank, through the inverter, and hit the not so charged bank for about 20 seconds with the pm set to warp speed (full voltage). The pm came on in what I like to call "Boobs Mode" (neither boost nor abs) and volts began to rise to the lower 'abs' setting, which is the usual for the pm on discharged batts ... Hey, maybe that's what the B in pm4b should stand for??? ;) ... The Trimetric showed the amp draw quickly rise to the -90 amp range; so about 9 amps at 120v, like erinn said. Just for amusement, I switched things up and hit the near full bank the same way, and of course the voltage shot way up, real quick, and set off the low voltage alarm on the inverter; and the amp draw quickly rose to about -90 amps as before.
So just as I was becoming convinced I was dealing with a 45 amper, it appears it is a 75 amper. So now I have to consider the possibility there is an internal problem with the pm, and something is keeping it from putting out its rated amperage.
I was actually hoping it would turn out to be a 45 amper, seeing as that could actually work out better in the end. I am planning on making full use of the gennie while it's running, and seeing as top charging takes so long, I figured I could develop a charge regimen that would allow me to do a 50-?% with the pm while doing a ?-97% with the gophert 1620. A 45 amper would actually help bring the two charge times more in sync. The 75 would be too quick, AND it draws too many amps (along with the ~4a draw of the 1620), for the gennie. So, I'm thinking this whole thing is a wash... Well, I guess I could keep it around for fast charging, if and when necessary, or if i go back to the larger bank. But I think I'm looking at yet another charger! The pmbc looks promising, but my faith in pm is quickly diminishing!
I can certainly utilize the peak 40 amper; IF the input current is low enough (i'll check that tomorrow), and IF the 30a glitch it had on the 430 Ah bank doesn't happen on the smaller banks; but i'm concerned about the higher voltages during summer temps... this I would like to have more control over (Yeah, I know, I'm preaching to the choir). I am fully convinced that was causing the excessive gassing. And I am definitely going to improve ventilation of both the batt and the charger cabinets!
