Battery equalizing / rotating?

Re: Battery equalizing / rotating?

Uh oh. Middle cell in that low battery is off-the-scale low on the hydrometer, I can't even get the float to float. I split the bank and am running off the good half now.

Anyone got an opinion on that? There's no bringing this thing back is there? I've got shorted plates or something huh?

Oh boy, I know I'm not supposed to mix old and new batteries but what are my options, other than throw away $3000 worth of batteries after 4 years and start over?

Re: Battery equalizing / rotating?

Thanks for all the help. I don't know what's going on here, I just measured the battery after 4 hours of rest and it was at 6.6 V. So I don't know why I get abysmal SOG readings on one cell but the voltage at rest seems ok, or even high.
Maybe I'll start a new thread after getting some more measurements. I really appreciate the feedback.

Re: Battery equalizing / rotating?

Cariboocoot wrote: »

I have to point out that if you can't take an "at rest" battery Voltage reading due to constant use then you won't be able to do a proper Equalization either as the batteries are not supposed to be connected to any loads during that process.

I separated my parallel strings for almost 4 hours and measured the battery in the string that had had no charging or discharging for that time. Voltage seemed higher than I would have expected.

So If I have 100A available for charging and 10A out of the batteries through the inverter , you say that I can not get a good equalization charge as I have loads applied to the batteries at this time? This statement does not make sense to me, could you explain further?

Re: Battery equalizing / rotating?

Wow, it's getting more confusing by the minute. I do not have a 100Ahr battery bank, I have a 1060 Ahr battery bank @24V. Sometimes there is a 10ADC load on my system while I attempt to equalize them with 50A@ 24V nominal solar + whatever I can get out of a VFX3524 on a 7500W generator. I guess once I turn on the generator, the 10ADC load switches to the generator and becomes a 2.x VAC load, but the net effect seems to be the same to me.

I equalize my batteries at 32V and they are in an insulated box which was at 64F here today and has never been below 45F in the last four years. I completely understand the voltage limitations of cheap 12V inverters and the effects of cold temperatures on batteries.

I fail to understand how these issues pertain to me and my concern that I have a three cell six volt battery which reads 6.6V after four hours rest yet one of the cells is extremely low when I test it with a hydrometer. I will gather more data and attempt to post a more concise summary of my problem in the next few days. Thanks for the replies.

Re: Battery equalizing / rotating?

Yeah, I would love to try and charge this battery for a good long time by itself. I'm going to work on that, but I think I need a good 24-48 hrs on grid power, I don't know if my 6V charger is beefy enough and these things are heavy!

Final result for the day was the bad cell came up to 1175 with 120F battery temperature. This seems to be OK according to Surette document 605. I took the string off line to let it cool down and will measure SG again in the morning.

I learned a lot in the last 24 hrs! Thanks again to everyone who commented!

Re: Battery equalizing / rotating?

Just an update here. I have managed to bring the bad cell up to 1235 SG today. It has taken three or four cycles of coming through an absorb cycle and trying to push voltage up to 32V with the generator alone. I can only put 55 or so amps into these at 31.x volts through a VFX3524. We have not seen the sun for two days

Anyone reading here with parallel strings, be advised to check them from time to time. I had a little chat with Tom Duffy, who sold me these and he had a funny analogy. He said that battery cells in parallel strings are like children set loose on the playground. They're going to run off in all directions and you have to round them up from time to time.

So if anyone reading this in the future thinks they have a bad battery cell, I suggest the "corrective equalization" procedure, but you have to do it one series string at a time, and you might have to do it several times. What really sucks is having to do this during the shortest days of the year with a persistent cold front. I think I've burned through 20+ gallons of gasoline in the last 3 days.

Re: Battery equalizing / rotating?

BB. wrote: »

120F is awfully hot. I would try to stay below that by 10-20F.

I'm going by what Surrette, the manufacturer of my batteries recommend. I would be interested in hearing why you disagree with them.

Also disconnecting the good strings and using less current just got the one string.

I read this three times, and I still don't understand it. Do you disagree that it is important to equalize one series string at a time? Or are you trying to warn me that I need to equalize the other string as well?

Or, I would use a six volt charger driven by your ac inverter. Using all that fuel for one cell/battery is a killer. Probably disconnect the one string you are charging that battery on.

To equalize a single 6V L16 I need a battery charger that can deliver 8V at approximately 20A and will limit the current at 8V. I would be very interested in learning about an affordable battery charger that meets these specifications.

Also, are you really recommending I correctively equalize a battery on an off grid solar system in the dead of winter, when I haven't seen the sun in two days with the OTHER BATTERIES? to save gasoline? ... REALLY?

Re: Battery equalizing / rotating?

I apologize if I got a little snarky there. I think I was unclear. To equalize this out of spec battery, I would have to haul it to a grid tied location and do it there, while surviving off half my capacity in the dead of winter. I've been a little stressed out lately if it is an excuse, sorry.

I get your point Vic. I know that SG is dependent on temperature, some of my measurements were taken 20-30 degrees off 70F, but I do understand the correlation. I should have mentioned temperature while reporting that. I also realize that SG is dependent on water added to the cell, and this is where things get tricky. I haven't been religious about making sure that the level between cells is exactly the same when I water the cells over the last few years.

Maybe someone can explain this to me. I have four 6V L16 batteries (800AHR @20 hr rate) hooked to my system @24V ( I split the parallel batteries out). They are maybe 20-40% discharged according to SG. I try and absorb charge them with the generator and the VFX3524. I can easily reach 29.2 V within a half hour and charge amps drop to 15A or so within 30 minutes.

I let them charge another 30 min at 29.2V. Amps in are still 15 or so . Batteries might be 80F or so but no higher at this point. I assume I now have fully charged batteries and might try to EQ now. I push the voltage to 32V, but the generator ( through the 20AAC limited VFX3524) cant keep the voltage that high more than 10 minutes. Voltage drops to 31.8, then 31.6 over the next hour.

Do I need to be more patient in my absorb cycle? It is usually programmed into the charge controller for 2 hours, and we hit it and go into float almost every single sunny day of the year. My reported numbers are my observations trying to correctively equalize this bank with a generator over the last week or so.

I thought it was important to hit the 2.66v/cell for a good hour or two to do a proper equalization. My experience has been that I either push the battery temperature way high or that I can't muster enough current to keep the voltage up for that length of time, which confuses me.

Hehe, I should have posted this in the beginners forum, because the more I learn, the more I realize I don't know!