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Home Forums Technical Discussion Insane battery system need help

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    Nick Rosen

    The system is 24 cell 48 volt 96,000 amp hour battery bank with a 5k diesel generator and 16 150 watt 40 volt panels and 8 300 watt 120 volt panels using two outback inverters and charge controllers (FREAKING HUGE).

    The problems

    1.We have a dead battery.(I bypassed it)

    2.I am in way over my head and need help. I don’t really know enough about solar power and dc power. I was out here to learn about solar and dc power when my teacher was fired for theft. The place I live is very poor thanks to my predecessors we cant afford the $900 the battery company wants to come and do an inspection. I fear I am not qualified to work on this system and don’t want to cause any more damage. Please help me keep our place alive. I don’t even know what questions to ask so please ask me things and explain why you are asking. I have the system working but we never seem to have enough power my bad math skills may be the problem but I think we put in 150-250 A.H. in a day and only use 75-100 A.H. and i still have to run the gen. every few days.


    hi i think you may be overstating the amp hours of the battery bank

    96000 sounds way to high.

    elnav may be able to chime in but if it were me the first thing i would do would be to bring the system up to full charge that will probably mean running your generator for a while to get it up fully.most likely you have been running at a low charge rate for a long time only running the generator

    to top up most likely never to full charge.

    if you have been running low for a long time you may have a battery sulphite problem do a search for the cure to cure is low tech and probably

    not the best idea for a learner but i also dont think you need to pay out the big buck for a battery desulphite gadget.

    so you need to research learn and decide what is best for you

    what is the amp hour rating of each cell? because this is the rating of your

    whole system.(because its a series system) i could not imagine the size of a cell to provide 96000 amp hours


    just out of curiosity where are you?

    Nick Rosen

    I may be stating it wrong. Each battery is a Mct II 4000 A.H. telecommunications backup battery for powering cable and phone systems during outages. I am at East Jesus a artist retreat and private venue for musical talents located in the Imperial Valley desert of Southern California here is our website We have an electronic desulfinator thing hooked up I never had it explained to me.


    The system is 4000 amp hours capacity. When series wiring cells the current stays the same but voltage adds up according to number of cells.

    To test you need a hydrometer to test the specific gravity of each cell and a good voltmeter.

    If you give me a phone number I could call you ( or skype) and talk you through the test process.

    Nick Rosen

    Elnav my email is please contact thru that so i can give you a phone # in private



    to me

    Delivery to the following recipient failed permanently:

    Technical details of permanent failure:

    Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 554 554 delivery error: dd This user doesn’t have a account

    Nick Rosen

    sorry i just got your second attempt email i dont know why the first one bounced


    I had a 3 year at least premature dead cell, replaced that battery and then a month later more, then more until all 8 were replaced 3 years early, when the desulfator hype said it was supposed to double battery life. The American Battery company experts told me the desulfators did it with their constant frequency bombardment, and well charged systems didn’t need them.

    The original author better get to reading on batteries and how to set up banks and the proper solar charging. There are lots of handy books like the Independent Home and newer ones. One bad battery or cell can do damage to others. The desulfators are bunk. Too low of a charge controller can over heat even though within its supposed range of operation. Batteries must be checked and maintained at least monthly, generally, for wet cells. You need a hydrometer for checking them and it is handy to have a multimeter. Plus the right wrenches with electrical tape handles to protect from accidents.

    It is not that difficult in theory. + is red and – is black and don’t touch them together. With battery banks it is + to + to keep the same voltage and + to – to increase it. Read the books, look at their bank diagrams, and follow their safety procedures. Be quick, because one battery removed changes the voltage to lower and puts more stress on the rest.


    Dustoffer, I will be the first to admit desulfators are not a magic solution.

    However I have also had sucess in some cases.

    The original poster has a very unique problem. The battery bank is way too big for the available charge source. What the battery manufacturers are not telling us is there is a minimum limit as well as a maximum charge current limit. Joe’s problem is he cannot accumulate enough charge in a day to bring the battery bank up enough with the available solar panels. Consequently the bank is constantly under charged. circumstances beyond his control or even his knowledge compounted the situation.

    You are right, adding one good cell into a bank of older batteries is not good. Its worse when the batteries are in parallel. With care it could sometimes be done when the cells are wired in series.

    When I first had to deal with this kind of problem I always yanked the whole bank. After testing and recharging the batteries I kept the good ones for single battery use, and junked the rest. Prior to that we were lucky to get 18 months from a bank of mixed new and old. Things improved after that. Unfortunately company policy dictated I use size 8D because this was what we could buy at a resonable price from the wholesalers. These are not the best choice for deep cycling. The banks were typically made up of 3 – 6 of these 8D wired in parallel to power 2500 watt inverters in a rental fleet. We had a dozen charters and I was forever changing batteries. Now I know better and would argue the point with the boss because such a practice was not cost effective. But this happened 20 years ago and the industry has learned a lot since then.

    Nick Rosen

    Hello all,

    Due to weather and work here. I have not been able to get back on here till now (my internet was down). We were able to due the specific gravity tests today with the hydrometer after having used no power for 2 days letting the system charge and rest we had an average of 1.1


    Are you saying the average voltage is 1.1V or the specific gravity reading is 1.1?

    Either case indicates way too low a reading indicating severe sulfation problems.

    I have rejuvenated batteries that have been left unused for two years and showed low readings but never ones with such high capacity.

    The issue with sulfation is you need to not only deliver a voltage sufficiently high but also at a charging current that brings up the plates to a usable level.

    For two volt individual cells this requires a power source where you can adjust the voltage and current independently while monitoring the internal battery temperature. I speak from hard learned experience trying to salvage battery packs from telecom installations. Yes it can be done but preferably using lab grade adjustable power supplies and grid power so you can run tests continuously. Sometimes you need to be able to run the charge equalization cycle for several days at low currents. The voltage typically has to be adjusted every few hours.

    Nick Rosen

    the voltage was a steady 2.06 volts per battery the specific gravity tests had 12 of the batteries reading 1.175 on hydrometer and 11 had no reading only the clear part of the hydrometer was bobbing above the fluid and 1 battery the dead one showed .010v and the bobber did not float in the hydrometer


    you have bigger problems than was first apparent. Your original post indicated your daily use was 75 -100 amp hour. The comment that you only need to run genset every few days suggest the existing solar panels are choking on the over sized battery bank. It would be far better to have a much smaller battery bank that the solar panels can cope with. I have seen the exact same problem on sailboats where the owner spend thousands on a huge battery bank then proudly announce to eveyone that they only have to charge the bank once every two weeks. Within two years this oversized battery bank is reduced to a pile of useless lead sulfate because the lead sulfate formed in the first few hours of use is then left sitting until charging is finally done. By that time its very hard to convert back to lead oxide and sulphuric acid. Every battery maker has fine print saying recharge immediately after using. By that they do not mean tomorrow or next week they mean right now this same day. They also know most people ignore the advice so they will soon be back buying new battery replacements.

    For off-grid applications a nickel iron ( NiFe) battery would make more sense but most people are put off by the higher initial unit cost. Brandon who owns a company providing such batteries can maybe chime in here with more data. He did post something about six months ago.

    My own calculations suggest that by making best use of NiFe characteristics you will get better and more reliable service and the price premium is nowhere near as high over a 10 year period compared to lead acid. Critics will argue that NiFe is less efficient but ignore that once purchased solar cells provide power at virtually zero cost. NiFe became unpopular when we still used generators to charge off-grid banks so cost of fuel was a significant factor.


    my thoughts…..i know with my small battery bank 360 amp hours. (4 l16/24 volt) even when they where new and i eq’ed them it took roughly 16 hours. call the battery manufacture for a eq voltage. it may also be a good time to select the best batteries at this moment and reduce the bank size(as enlav suggests) this way you can do it through the solar array and charge controller. if you want to use an inverter/ with a gen set to eq you may need an accessory control modual. for example with outback inverters the mate will perform this.. talk with tech support of your inverter manufacture. take the rest of the batteries to a location with grid service add a desulfator and try to revive the remaining batteries(maybe 6 months if you do it slow and proper.)

    either way it will cost you in time or money.

    once you get pack to par you should do gravity test regularly. maybe every week for starts to see how the batteries are holding up. then ideally about once a month.

    cheers g

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