Tired Batteries??

[twombo]

Heres Is where I am at and what I am seeing:

I have six T105 batteries set up in three parallel strings for 12 volts and 675 amp hours capacity. The batteries have been in service nearly four years and the first three years they suffered a LOT of abuse by the previous homeowner. I have getting by reasonably well  and they have been hold the load pretty well. (Actually I am surprised these batteries have made it this long.  I have been nursing them along pretty closely!)

I use about 1.5kw of power a day. With my 440 watts of solar panels and about 1 - 2 hours  of generator backup I had been getting the batteries to about 1.25 specific gravity using the Xanstrex 2412/ gen set and C-40 charge controller. Equaliization has failed to get any more out of them.

In the last week, it has been taking more and more generator run time (5.25 kw Coleman Powermate) to get the S.G back up. I ran about 4 hours last night and 1.2 s.g was tops.

Battery cables are ( and have been) clean and corrosion free, but looking in the batteries, I see a lot of distortion in the plates and a certain amount of gravelly looking residue  between the plates the battery jars are even bulged a bit.  Tey were like that when I moved in.  I think it goes without saying, my battery bank is probably entering a death spiral,  Whaddya think!!

My "get better" plan is as follows:

1.  Finish up the single cylinder Kubota DC genset ( EB300D prime mover, Xantrex XAR-12 charge controller and 160 amp Leece Neville 2800 alternator) I should be able to make 80 to 100 amps at 12 volts. ( I figure I need a good makeup source of charging right off  the top since that charging efficiency of the Xantrex inverter charger is  less than optimum withthe powermate genset
   
2.  Replace my battery bank with four or six  L-16s. I could probably go cheap with 6 more T-105s, but, that seems "penny wise and pound foolish"! Six of these big boys are  pricey but  I simply can't afford  to go to a 24 volt system  and forkllift batteries anytime soon.
   
3.  Add a couple more solar panels (my solar exposure is less than optimum and it's particulary bad this time of year, given clouds trees and low sun angles!
   
   

Sounds about right?

Thanks for any comments, Need anymore info?  

Thanks all!

Mike

[scottsAI]

Hello twombo,

1. 5kw as in 1.5kwHr?
   
1500. a / 12v = 125aHr
      
      

Simple math suggest one pair of T105 should be able to handle your needs per day.

You have 3... Yes, something is wrong.

When the battery bank is charging has it made it to finishing charge?

Does the controller support finishing charges?

First measure each battery voltage, they should be nearly the same.

Measure the individual temperatures of the batteries while being charged, a warmer one is possibly the problem. (not always)

I would split the 3 battery strings unless they all look the same. See if one battery is pulling down the others. By charging the strings individually, along with measuring the batteries voltage.

440 watts solar, 3-4 hours of sun should charge up the batteries each day, due to efficiency losses once a week run the generator. I am assuming you have more than one pair:-) of batteries.

Your setup looks like 4 batteries are needs for on the cheap. 4 days need to run gen. 6 batteries 1 a week run generator. Adjust basted on how much sun you get each day.

Something to think about. The cheap batteries lasted 4 years, poorly maintained. How long could they have lasted if properly maintained? The more expensive will last how long? Unless in survivalist mode, consider the lowest cost storage. Cost / life.

I use 8 golf cart batteries from Costco, $53 each, for back up only. Expect to get 7 years, currently on year 1.

Have fun,

Scott..

[twombo]

Yes, 1.5kwHr, sometimes (rarely) as high as 1.8kwHr per day. Some 10 hours of CFL at 14 watts/hr and 10 hours of Imac and Satellite modem at about 300 watts/hr. No TVs, microwaves or other such nonsense!

Voltages measured at rest, at least 1 hour after charge of discharge is a voltage definitive check, or are we just looking for a battery to battery relationship... a "spread", if you will?

Will split and do separate charges.

I don't really have any battery temp issues of note. Actually I don't see a lot of gassing/bubbling even during bulk or equalization. I do show the inverter/charge indications going through all three stages: bulk, absorbtion and float. Normally, I never stop charging until it goes into float and then run at least another 10 minutes or so. Ive read that running aother load like a washingmachine while charging enables the Trace inverter/charger put a better charge output, what say you?

I just got a Trimetric  and a remote display for my C-40 PV charge controller and will be instaling them this weekend for better monitoring capability.

I do want to increase the battery bank capacity to the high side a bit to give me more time for shop lighting in the workshop which I will be spending a lot more time in pretty soon when I retire. I also plan to add a cell phone amplifier to set up some level of phone service capability. I do see my electrical consumption going up a bit over time, so going a bit larger than my current needs seems wise.

Interesting thoughts on  cost / benefits. increasing the the individual battery size  would allow me to  reduce  from three strings to two, which I understand to be  better across the board for long term battery survival, I appreciate yur suggestion. It is amazing that the batteries have lasted this long. The previous owners were pretty vocal about the many low voltage disconnects  they experienced. The inverter is set at the normal 20% SOC disconnect point.  

Maybe I have been living with a weak battery bank for all this time and don't have much of a reference to what a good set is capable of. I might just buy a set of four to get going and take it from there!

Thanks a bunch Scott!!

Mike

[Volvo farmer]

What votage are you equalizing at and how long are you holding it at that voltage? I'd think you want to boil 'em at 15.5 or 16V for two hours and see if things improve.

[twombo]

Yo Farmer

Equalizing as we speak. Voltage is 15.5 and I got some good bubbling going on. Checkedmy calender and it's been a month since the last equalize, so I may have some electrolyte stratification which would explain the slow rise in S.G. It has been pretty chilly too.

Thanks for the reminder.

With low sun days I charge till I have float every day or so  to avoid letting the battery bank sit in an undercharged state. I ran the cable for my Tri-Metric tonite and will get it hookedup this weekend to have a better monitoring capability.

68 220 is almost on the road, maybe this weekend!

Cheers

Mike

[Volvo farmer]

You got cold batteries? 15.5V equalize is for 70F batteries. I don't know the exact numbers but I'd think +1V in the 58F range and +2V in the 45F range. Seriously... boil the crap out of them for a while. My guess is that sulfation is a greater danger than the occasional overcharge in your case.

I just sold my 1800 :-(  Maybe I'll get my 220 on the road again to comfort myself.

[twombo]

Installing an insulated battery cabinet this weekend with .250" by 1.5" copper positive and negative buss bars. The garage tends to be about 15 degrees or so warmer than outside air temp so it was 40 degrees this A.M. Did get the S.G up last night to about 1.25 and some change which looks like about the max for the temp out there.

Big power system rework going in this weekend it looks like. Got  a big pile of parts for system upgrades and most of the basic wiring is now pre-run.  Just gotta break things down and install the prefabbed system board and reinstall everything in the new and upgraded configuration. The "kludged up" power system will finally be a thing of the past, I hope!!

Sunday P.M sounds like a good time for a good healthy stir.

Guess the wagon will have to wait another  week. I rolled my old wagon, you know? Is that the 1800 you got in Arizona a couple years ago! Cain't fit a sheet o' plahwood in one o' them swedish meatball sports  cars anyway, right!!!

Finally sold my old house in town and I can focus on life off the grid more fully. Couple inches of snow yesterday too!!  

Best to you!

Mike