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jrnymn7's avatar
jrnymn7
Explorer
Aug 16, 2014

when should a powermax pm4b drop into float mode

Hey everyone... hope your summer has been as enjoyable as mine. (...loving the cooler than normal weather!!!)

I recently installed a new pm4b 75amp charger and Trimetric meter. My batteries are 4 Transcanada tc-2gc-220, wired in series/parallel for 430ah.

I have been unsuccessful in finding any specs on these batteries, although they are considered among the best out there. I have also read that a really good battery can be charged, in ABSORPTION mode, to as much as 99% of its capacity, i.e; until the charge current reaches 1% of the ah capacity, before it will kick some chargers into float mode. so, in my case, that would be when the charge current drops to 4.3 amps.

But according to the meter, I have reached a charge current as low as 2.4 amps before I've just shut things down and gone to bed... that's almost 99.5% charged!

So, I either have an amazing set of batteries, or something is stopping the pm4b (and all but one other charger I have tried) from dropping into float mode. I cannot obtain any info on the pm4b as to it's parameters, and I'm concerned about whether there's something amiss with either the charger or one or more of the batteries?

The batteries seem to charge well, and hold their charge well at rest. For example, last winter they sat for 5 or 6 weeks in freezing to sub freezing temperatures, and held steady at 12.78 volts. But they seem to discharge rather quickly while under load... thus the reason I installed the meter and shunt. The meter does not detect any unaccountable loads, and everything seems to be drawing power as expected. So now it's just a matter of keeping better track of my actual usage.

So I find myself in a position where, 1) I don't feel comfortable leaving the charger unattended (even though it's at a reasonable 13.67 volts in absorption mode, and 2) not sure as to what readings I should consider the batteries to be "fully" charged?

any help and experience you can share is much appreciated!

399 Replies

  • Look, hydrometer readings -verify- they are a state of charge polygraph. If you test cells and find them full and the controller or coverter is still in absorbsion...

    BAD

    If the controller or converter drops from absorbsion to float but a hydrometer reading says the batteries are not at full density

    BAD

    If batteries are presented a uniformly predictable charge regimen every day they are not going to do the Dr Jekyll Mr. Hyde routine. If the charging device can't walk and chew gum, stick behind a rear tire and back the vehicle up a foot or two. That is an effective fix-it tool for schizoid mechanisms.

    Once a charging management device is dialed-in it should stay that way for months. Temperature and battery condition will affect the dial-in.

    Most charge management devices do not allow to user to dial-in (tweak) charge protocols to suit the battery. The battery gets angry and has the last word.
  • rjxj wrote:
    Let it charge. Keep an eye on it but it will drop to 13.2 My Progressive Dynamics will take a day or more and will eventually drop. Converters and real battery chargers are not created equal. As mex says, you do want to know what it takes to reach full SG and recognize your converters ability and you wont have to check it all the time.


    so i'm not the only one with this issue... good to know. i think maybe it's all part of having a fairly large battery bank?

    i very rarely have access to shore power, and obviously running the gennie for 24+ hours isn't an option, so i'll have to arrange something where i can hook up for at least a couple days just to determine whether or not the charger will drop into float.

    in the meantime, however, i cannot charge my bank 24/7, so i still need to know what constitutes a reasonably "full" charge... so that i don't continually under charge. i guess i'll have to do several SG readings after bringing the batteries to various charge current readings, i.e; down to 8a, 7a, 6a, etc.
  • Let it charge. Keep an eye on it but it will drop to 13.2 My Progressive Dynamics will take a day or more and will eventually drop. Converters and real battery chargers are not created equal. As mex says, you do want to know what it takes to reach full SG and recognize your converters ability and you wont have to check it all the time.
  • mena661 wrote:
    X2 MEX. My converter will go all the way to 0 amps and the batteries are still not full. Converters don't fully charge batteries. None of them do (I've used 3 different one's).


    so, should i shut things down at around 5 or 6 amps charge rate?
  • Flyfasteddie wrote:
    I have wondered about this myself in the past. I installed a PD4645 4-stage converter a year ago and have it feeding a single 12v 80ah battery.

    My converter stays in absorption mode at 13.65v until the Trimetric has been showing 0.00a to 0.01a for around 12-24 hours.

    My understanding is that the 13.2v maintenance mode is just that - it won't drop to that until the battery is 100% charged, and 13.2v will then maintain 100%.

    It makes sense to me since the old single stage chargers use to run around 13.6v, and I'd only run it for a few days every month or so to maintain the charge without boiling the batteries.


    if the trimetric reads 0.0 - 0.1, then there is no current going in or out, and the charger has turned off. not sure how or why your charger could still be in absorption mode at that point???
  • MEXICOWANDERER wrote:
    When one of these...




    Reports than all cells in the bank have returned to full specific gravity. All other qualifiers are bogus info.


    the last time i checked all cells were at full specific gravity, but it's been a while, so i will check them again. i usually charge my bank every other day, and my batteries are in a compartment under my bed... so that would mean pulling apart my bed every other day... so that's not a viable option. but i agree it's the best reading possible.
  • X2 MEX. My converter will go all the way to 0 amps and the batteries are still not full. Converters don't fully charge batteries. None of them do (I've used 3 different one's).
  • I have wondered about this myself in the past. I installed a PD4645 4-stage converter a year ago and have it feeding a single 12v 80ah battery.

    My converter stays in absorption mode at 13.65v until the Trimetric has been showing 0.00a to 0.01a for around 12-24 hours.

    My understanding is that the 13.2v maintenance mode is just that - it won't drop to that until the battery is 100% charged, and 13.2v will then maintain 100%.

    It makes sense to me since the old single stage chargers use to run around 13.6v, and I'd only run it for a few days every month or so to maintain the charge without boiling the batteries.
  • When one of these...




    Reports than all cells in the bank have returned to full specific gravity. All other qualifiers are bogus info.

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