Battery Voltage Discrepancies ??
Hello battery experts and fellow nerds :C I have noticed small voltage differences between the three Odyssey PC2150 batteries that make up my "bank". This is after resting with zero load for 24 ho...
Forum Discussion
Muchas gracias for the thoughtful and mostly intelligible response Mex' ;)
This was one the first things I did. At a constant voltage of 14.7 the charge acceptance rate is the same across all three batteries... However this is tempered by the fact that my built-in ammeter (TriMetric) only offers resolution to one decimal place.
I s'pose a fun over-the-winter project will be to do a controlled capacity test and data-log it with the TriMetric. I need to locate something sensible to use as a fixed resistive load, maybe a 55W automotive headlamp would work... that's ~4.6A which is pretty close to the 20-hr rate of these batteries. I can say that the testing I have done to date has not indicated a noticeable loss of capacity (yes, of course I know the batteries are used and have aged & sulfated and as a result have less capacity than they did when new... there's no free lunch)
So what is your recommendation for this top charging?? Odyssey says to never exceed 15.0V unless the battery has been deeply discharged (mine have never been below 50%). A ~15V CV charge would be easy to do and monitor, but what do you recommend that I use as the termination parameter? Delta-temp'? Time? Charge acceptance rate?
Or do you think that the top-charge should be CC? I could do that but it would take a bit more re-programming and (depending on voltage) might even require me to use a bench power supply.
YES I know... and in my case it's 18 different cells! And of course I have no way to check cell voltage or SG. Ah, the joys of AGM ownership :C
The good news is that these batteries have always performed flawlessly and have exceeded my every expectation. Their high discharge rate capability is truly remarkable! In addition they are lovingly cared for by a couple of carefully-programmed, microprocessor-controlled, charging devices... in strict accordance with the manufacturer's charging spec'... always temp' compensated... seldom deeply discharged. During camping season they get a daily solar charge to 14.7 when in use and to 13.6 in stand-by (The MorningStar controller allows for 2 selectable charge profiles and I have a switch to choose which one to use). In the winter the camper is stored indoors and they get a weekly 14.7V charge from the Prosine 2.0 and the batteries are disconnected between charges. It's a good life... ya' know, if you're a battery.
Cheers,
-Mark
MEXICOWANDERER wrote:
Impress a constant VOLTAGE across EACH battery now. Does the lowest reading battery NOT accept an amperage different from the highest SOC battery?
This was one the first things I did. At a constant voltage of 14.7 the charge acceptance rate is the same across all three batteries... However this is tempered by the fact that my built-in ammeter (TriMetric) only offers resolution to one decimal place
I s'pose a fun over-the-winter project will be to do a controlled capacity test and data-log it with the TriMetric. I need to locate something sensible to use as a fixed resistive load, maybe a 55W automotive headlamp would work... that's ~4.6A which is pretty close to the 20-hr rate of these batteries. I can say that the testing I have done to date has not indicated a noticeable loss of capacity (yes, of course I know the batteries are used and have aged & sulfated and as a result have less capacity than they did when new... there's no free lunch)
I am firmly convinced that the "agonizing exertion" of spending an hour with an AGM battery every six months or so can extend its life dramatically. Determining if loss of capacity has occurred then correcting it by top charging if necessary is vital.
So what is your recommendation for this top charging?? Odyssey says to never exceed 15.0V unless the battery has been deeply discharged (mine have never been below 50%). A ~15V CV charge would be easy to do and monitor, but what do you recommend that I use as the termination parameter? Delta-temp'? Time? Charge acceptance rate?
Or do you think that the top-charge should be CC? I could do that but it would take a bit more re-programming and (depending on voltage) might even require me to use a bench power supply.
You must understand that an aggregate voltage total of six extraordinarily different cells add up to a .07 volt "difference".
YES I know... and in my case it's 18 different cells! And of course I have no way to check cell voltage or SG. Ah, the joys of AGM ownership :C
The good news is that these batteries have always performed flawlessly and have exceeded my every expectation. Their high discharge rate capability is truly remarkable! In addition they are lovingly cared for by a couple of carefully-programmed, microprocessor-controlled, charging devices... in strict accordance with the manufacturer's charging spec'... always temp' compensated... seldom deeply discharged. During camping season they get a daily solar charge to 14.7 when in use and to 13.6 in stand-by (The MorningStar controller allows for 2 selectable charge profiles and I have a switch to choose which one to use). In the winter the camper is stored indoors and they get a weekly 14.7V charge from the Prosine 2.0 and the batteries are disconnected between charges. It's a good life... ya' know, if you're a battery.
Cheers,
-Mark
