Charge controller for 64V (32 cell) pack

I'm looking to put a solar panel for battery maintenance on a locomotive and passenger coach. The equipment tends to sit for weeks at a time (also, all winter) without active use. The locomotive finishes the operating day fully charged, but then the battery slowly decays over time and we often find it is significantly discharged.

Our current plug-in charger is a "dumb" charger that can't be left on 24/7, so it only gets plugged in the night before planned operation. A proper 3-stage charger is rather expensive for this type, and would still require actively plugging it in, and babysitting to make sure a breaker didn't trip or a cord wasn't pulled out or "borrowed" to run a tool and not restored. Happens all the time. A solar install would make this "automatic" :)

However I'd need to find a controller capable of 3-stage charge (or at least 3rd stage trickle or pulse charge) of a "64v" (32 cell) lead-acid battery pack. I know that's an oddball size. Anyone know of a reliable supplier who can provide a charge controller for that voltage?

Second question. Ditto, ditto, passenger coach, ditto, 32 volts (16 cell) ditto ditto, however this battery deep-cycles and the solar panel may be somewhat larger to actually replenish it.

Comments

  • VicVic Solar Expert Posts: 3,145 ✭✭✭✭
    Re: Charge controller for 64V (32 cell) pack

    Hi Wolf,

    The MidNite Solar Classic 150 SHOULD be able to do the job. Here is the spec sheet:
    http://www.midnitesolar.com/pdfs/classicSpecSheet.pdf

    Classic 150 Manual is here:
    http://www.midnitesolar.com/pdfs/classicManual.pdf

    The MidNite Forum is here:
    http://www.midniteforum.com/index.php

    Will poke around on that Forum, as know that this type of question has come up on that Forum previously.

    Good Luck, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Charge controller for 64V (32 cell) pack
    Vic wrote: »
    Hi Wolf,

    The MidNite Solar Classic 150 SHOULD be able to do the job.
    But the Classic is pretty expensive for what may just need a battery maintainer. Especially if the OP feels that a good 3-stage mains-powered charger for 64 volts is pricey.
    SMA SB 3000, old BP panels.
  • VicVic Solar Expert Posts: 3,145 ✭✭✭✭
    Re: Charge controller for 64V (32 cell) pack

    Hi inetdog

    I have not priced a 64 V Mains Charger recently (or ever). If it is a Maintainer, then is should be less expensive than a charger, but have not priced those either.

    I did notice that there was a reference to the chagrins of keeping a Mains Charger really on Mains, and something about Solar.

    "Priciness" seems relative:
    http://www.solar-electric.com/misocl.html

    EDIT: Did re-read the OP, and it does say "panel", so perhaps the Loco batt is not huge. IIRC many Diesel Starters are in the range of about 1200 AH, but perhaps this batt is not nearly that large. There may well be small Solar CCs that can do 32 and 64 V, have not used either of these system voltages, so am not too familiar with the inexpensive CCs available for these V ranges.

    All FWIW, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • Wolf HarperWolf Harper Registered Users Posts: 10
    Re: Charge controller for 64V (32 cell) pack

    Yes, 64V is an oddball voltage rarely used outside locomotives, so a proper mains charger is unique and fairly expensive. It's the same story: they want to sell you a 20++++ amp replenishment charger when all I want is a maintainer. I've been having trouble finding a plug-in unit that I liked, particularly since I'm "all about" the maintenance mode, and want one that'll do the pulsed thing to attempt to desulfate the pack. Sulfation is a big problem for us and we only get 5 years out of batteries that ought to last 10.

    The batteries are Exide KDZ-2701, so 450AH. Lead-acid, eight of those in series.

    Much as I'd love to have 200 square feet of panel charging them, I'm limited by cost, and sites on the locomotive which can accommodate the panel, probably about 15 square feet. Like I say, it ends the day fully charged, I just need maintenance/desulfation.
  • BB.BB. Super Moderators, Administrators Posts: 32,608 admin
    Re: Charge controller for 64V (32 cell) pack

    If you can split the bank in 1/2--You might be able to find some less expensive PWM charge controller that could (as a pair) charge the battery set (programmable charging voltage--and make sure you don't "mix" grounding--The "high side" controller would be running at +32 to +64 volts on its battery leads--so you don't want to "ground" the negative terminal with any other metal/electrical connections).

    The problem is you need ~80 volts to properly recharge/sulfate that battery bank.

    If you did not "care" too much, you could probably get a solar array with Vmp>75-80 volts, a blocking diode and ~1-2% of the battery bank capacity. That would be, roughly, a 360-720 watt array (without a charge controller). 1% rate of charge should keep up with a "good battery"... You might need 2% (or even more) with a deep cycle battery nearing the end of life for maintenance charging.

    I would start with the 360 Watt array and monitor the specific gravity and battery voltage. Watch water usage--If you use a lot of water (have to fill the cells every month--then that is probably a bit too much charging current. If you are not having to add water every 2-3 months, you can probably increase the size of the array.

    As long as the plates are not exposed, and the batteries do not get hot or bubble a lot every day--You should be OK.

    For the coaches where more charging would be needed--Typically we would recommend 5% rate of charge minimum and a "real" battery charger/controller (not cheap if the Midnite would do the job--But that is a fairly large array near 4kW). 450 AH at 64 volts is a very healthy sized device.

    Some alternatives--Look at reducing power needs (i.e., do you really need 450 AH @ 64 volts for your situation)/standardizing voltages and increasing efficiency in the coaches (i.e., LED lighting, 120 VAC inverter running on 12/24 or 48 volt battery bank). Conservation/conversion may be very helpful here (may not be worth the trouble or "violation" of your historical cars either). Setting up something to charge a 48 or lower voltage battery bank from a "64 volt train bus (or AC main bus) is probably not that difficult (although, it would not be "cheap"--something like $200-$400 per conversion).

    Are you paying something like $3,000 per 450 AH 64 volt battery bank? That is enough to take my entire 3 bedroom suburban home off grid with 2 days o back up power and 50% maximum discharge (~7.2 kWH per day). That sounds like a lot of power for a train car on a museum line. If through conservation you could cut the power usage to 1/4 -- You could also reduce your battery bank size (or even do a conversion) based on the cost savings on batteries alone.

    Another suggestion--I put "dumb" chargers on cars that are not driven often behind a simple lamp timer. Set the timer for 1-2 hours per day and monitor the battery bank... If it needs more charging set to 3-4 hours per day... If it needs less, crank it back. Only time "it fails" is if somebody leaves a trunk light on--then the battery still gets discharged because the charger is not on 24x7--So you need to make sure everything is "off" on the car at night/over winter).

    You might also look around for phone company charging gear... Especially from Europe where there can be 72 VDC systems (I think--was many years ago).

    Otherwise, may have to look at some DYI electrical design (always a pain in the butt to maintain years down the road).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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