48v battery charging options

Stdyhand
Stdyhand Solar Expert Posts: 33 ✭
in Off Grid Solar & Battery Systems #1
What other stand alone battery charger could I use besides the Iota for bulk charging a 48v battery bank? The only IOTA charger I see on Solar Electric website is a 48v 15 amp charger, which seems a little on the small side for any 48v bank. I figured the amps going in needed to be 15-20% of the total battery bank capacity. A 15 amp charger would be small even for a 225AH battery bank.

Maybe I'm misunderstanding something. Nevertheless, I wanted to get a good idea of what my options were besides the Iota charger.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: 48v battery charging options

    No, you're not misunderstanding. But you have to realize that 15 Amps @ 60 Volts (charging for 48 Volt system) is 900 Watts. A high current, high Voltage charger is going to be difficult to build and will require quite a lot of power.

    Usually when you have a 48 Volt system you would have an inverter-charger, so the battery charging issue is resolved. There is rarely a need for a stand-alone 48 Volt charger.

    If you did need more than 15 Amps stand-alone you can in fact put multiple chargers in parallel.
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  • arby
    arby Solar Expert Posts: 108 ✭✭
    #3
    Re: 48v battery charging options
    Cariboocoot wrote: »
    No, you're not misunderstanding. But you have to realize that 15 Amps @ 60 Volts (charging for 48 Volt system) is 900 Watts. A high current, high Voltage charger is going to be difficult to build and will require quite a lot of power.

    Usually when you have a 48 Volt system you would have an inverter-charger, so the battery charging issue is resolved. There is rarely a need for a stand-alone 48 Volt charger.

    If you did need more than 15 Amps stand-alone you can in fact put multiple chargers in parallel.

    That is what I did when my 48V bank got so heavily discharged that the Inverter would not fire up as a charger.
    I separated the batteries into 12V pairs and charged them with a couple of ordinary 12V chargers.
    3310 watts panels, Classic 200 controller, 8 Surette S530's, Xantrex 5548 inverter, Honda EX5500 backup Genny.
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #4
    Re: 48v battery charging options

    Try searching for "48v forklift charger", many available.
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  • Stdyhand
    Stdyhand Solar Expert Posts: 33 ✭
    #5
    Re: 48v battery charging options

    I can parallel 2x DLS-54-13 or stack 2x DLS-27-40 in series. I am unsure which would be better. The two DLS-27-40 would provide higher amps going in which I would assume would bulk charge the battery bank faster. Am I wrong? I have a 3250/4050 watt generator to run a couple chargers. Would it be large enough?

    I really don't expect to need these chargers since I plan to have enough panels I should be able to sufficiently charge the batteries with no problem. The Iota chargers are strictly a backup in case the solar charger fails.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #6
    Re: 48v battery charging options

    Personally, I would probably parallel two 48 volt chargers vs stacking two 24 volt chargers...

    If one charger "fails", at least the whole bank is still getting charged. If one charger fails, it is incumbent on you to see the failure and take steps to fix it (not good if you have a non-technical spouse, kids, or guests while you are away).

    Also--You can use a smaller genset on one charger if/when needed (equalizing, slow charging with a smaller/quieter genset, backup to the backup genset, etc.).

    I could probably come up with some good reasons for 2x24 volt chargers (you are sort of "balancing" two 24 volt banks--may be less stress vs "balancing" a weak cell on a 48 volt bank)... And two 24 volt @ 40 amp chargers give you more power for the dollar vs 3x 48 volt @ 13 amp chargers--Hard to ignore.

    There is a 48 volt 20 amp @ 240 VAC charger available (not listed at NAWS)... If you have 240 VAC available, a pair of these would give you equivalent charging (perhaps at similar price point as the 24v/40 amp chargers.

    But, other than price, I cannot really see a good reason to pick 2x24 vs 2-3x48 volt chargers. I think 2x48 volt chargers are a bit more fault/failure tolerant and give you more options.

    You could even set them with two charging voltages... One with 58 volt bulk and the second with 62 volt equalize... Both with bulk charge (timer/generator minding by you), and the second will be available for equalizing when needed (you only need ~2.5 to 5% maximum rate of charge for equalization).

    My two cents worth.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #7
    Re: 48v battery charging options
    BB. wrote: »
    Personally, I would probably parallel two 48 volt chargers vs stacking two 24 volt chargers...

    I would not stack two 24 volt chargers in series. My reason is that I don't want my head to hurt from trying to figure out to ground them.

    Also, it would seem to me that you would need to fuse Pos and Neg on at least the one (or both?) charger that is floating ground.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #8
    Re: 48v battery charging options

    Paralleling two chargers is better. Always try to treat a battery bank as "one big battery" when you can. Series stacking presents the possibility of uneven charging between the two halves if there are any differences in the chargers/wiring.

    It is not as bad as series stacking two solar charge controllers however, as there is only the output side to worry about keeping negatives isolated on. You would not need a fuse on positive and negative of either charger; only on the positives. The two will act as independent DC circuits, which is also the problem.

    (And for the nit-pickers yes there is an advantage to individual charging, but really only if done on a per cell basis.)
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  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
    #9
    Re: 48v battery charging options
    Stdyhand wrote: »
    I have a 3250/4050 watt generator to run a couple chargers. Would it be large enough?

    I run a DLS-27-40 and have a Champion 3500/400 generator and due to the HIGH inrush of the Iota and the crappy power factor, it really puts a load on it. I know if I have it on, and my fridge starts, it just about stalls the generator. I doubt 2 iota 40's would run at the same time on my generator (and mine is a tad larger than yours).

    Bill (bb on here) had a nice formula to determine the generator size you need to run a charger given the power factor and target generator loading, etc. Perhaps he could jump in.

    Note: Some people with Inverter-Generators have had a LOT better luck running multiple Iota's.
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #10
    Re: 48v battery charging options
    Cariboocoot wrote: »
    Usually when you have a 48 Volt system you would have an inverter-charger, so the battery charging issue is resolved. There is rarely a need for a stand-alone 48 Volt charger.
    I really have to agree with Coot on this one. While there are reasons to have a stand alone charger and I have many, a quality Inverter / Charger makes more sense, especially for a 48 V system. Most of the big 3 + Inverter manufacturers products give you a control systems cannot be found in low end Inverters or chargers, so don't cut yourself short. They allow you to limit the Input to the Generator Output and balance the charger to the pass through loads. You have many more options for Voltage, Time and Current. You'll spend more up front, but long term you'll be ahead.
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  • bill von novak
    bill von novak Solar Expert Posts: 891 ✭✭✭✭
    #11
    Re: 48v battery charging options
    Stdyhand wrote: »
    I can parallel 2x DLS-54-13 or stack 2x DLS-27-40 in series. I am unsure which would be better.

    Parallel. I blew out two 24V Iotas trying to series them without a good midpoint battery connection. (I suspect one failed with an output short, and before the fuse blew, the second charger saw the full 48 volts for the entire night.)
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #12
    Re: 48v battery charging options
    Blackcherry04 wrote: »
    I really have to agree with Coot on this one. While there are reasons to have a stand alone charger and I have many, a quality Inverter / Charger makes more sense, especially for a 48 V system.

    Agreed. And if you need a stand-alone charger you can buy a MSW (cheaper than sine wave) inverter/charger, and just use it as a charger.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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