I need to charge a 96 volt battery pack

heynow999
heynow999 Solar Expert Posts: 80 ✭✭✭✭
in General Solar Power Topics #1
I am working on a project for the local zoo. They want to convert a jeep based, mini train, people mover to electric, and they want to put solar panels on top for opportunity charging during the day. They reaslize that it will not provide all of the power, but it will help maintain the batteries by not leaving them flat.

They will have a pack of 16 x 6v/283 ah/hr lead acid batteries on each unit. On each unit it will alos have 4 x 200 watt panels. What we need is a way to charge the 96v batteries from the 4 x 200 watt panels. I was thinking an outback CC, but they only seem to output 48v. Could we split the output of a CC and charge half at 48v and the other half at 48v? Any other ideas?

All help is appreciated

Thanks

Peter
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Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: I need to charge a 96 volt battery pack

    Yes, but you'd need two charge controllers and probably a hub & MATE to co-ordinate them. Basically feeding two of the panels to each controller, then 'split' the battery pack at 48 volts. NOTE: you'd have to isolate all wiring! The grounds on these things are connected to the chassis!

    That would be a lot of extra equipment to drag around, though. You might be able to get away with just feeding the panels directly to the batteries without a controller, depending on the charge/usage ratio. Since there would be less than 10 amps (800 watts/96 volts) coming from the panels in peek sun it may not be a problem as that's only 3.5% of the battery amp/hr.

    Why don't they use a 48 volt motor? Probably not enough HP.
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  • heynow999
    heynow999 Solar Expert Posts: 80 ✭✭✭✭
    #3
    Re: I need to charge a 96 volt battery pack

    96v was used because there is a lot of industrial equipement that works at that voltage, AC chargers and such. I think we should look at just feeding the panles straight into the batteries. It would be good to have something to protect the batteries from over-charging. What if they charge it at night and roll it out of the garage and let it sit for a few hours in the sun? We need to make it a bit idiot proof.

    We are trying to keep it cost effective. We can't have all kinds of extra equipement to make it work or they might not go for it.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #4
    Re: I need to charge a 96 volt battery pack

    I think that the limited number of PV watt available, relative to the size of the battery is pretty small. As long as you monitor the water in the batteries I think you would be fine to connect them directly.

    I think adding more panel capacity in the future would be nice too,, and then you would have to consider a cc.

    Tony
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  • heynow999
    heynow999 Solar Expert Posts: 80 ✭✭✭✭
    #5
    Re: I need to charge a 96 volt battery pack

    If the panels put out 30v each, 4 would make 120v. Could we feed 120v into a 96v battery pack? That seems a bit much? How about make two strings of two panels, and feed 60v to each side of the pack at 48V?
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #6
    Re: I need to charge a 96 volt battery pack

    Your going to need someone with more expertise than I!

    Tony
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #7
    Re: I need to charge a 96 volt battery pack

    you are dealing with an odd-ball charging voltage for a odd-ball battery system so there isn't ready made stuff for that in solar applications. you have to have regulation or you will have at least higher maintenance and possibly risk an over charge to the batteries. as long as this stays small in terms of current to the batteries a split arrangement with 2 pwm controllers might work. your charge rate will be in the area of about 1.6%. normally this would be frowned upon due to creating a possibility of an uneven charge condition to the batteries and make no mistake that this can still happen. there is not any way you can idiot proof this and ideally you should have a regulator that covers all of the batteries in series without a split being created in the batteries for float charging. you obviously have a charger for 96v and it may be conceivable to contact that company to see if some type of regulator can be made for you with the voltage input range offered by the pvs you have. this will be from 0v to 4x the open circuit voltage of each pv as all 4 will be wired in series and their voltages added. another requirement of this regulator would be to not allow any backfeeding of battery power when lighting from the sun goes below the charging voltage level for the batteries.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #8
    Re: I need to charge a 96 volt battery pack

    Your battery pack should be able to take 120 volts from the panels, as that is "open circuit" voltage and would drop considerably when under a load. A 96v battery pack should "absorb" at about 112, in fact.

    The simplest solution would perhaps be a relay that would activate above 96v and disconnect the panels from the batteries just to be safe. Where you'd find a "96 volt" DC relay I don't know. There may be some 110-120 VDC relays out there that would actuate at an acceptable level. The other end is it would have to use a small enough current to stay engaged until the battery voltage fell off significantly before re-connecting the panels. A lower voltage relay in series with a resistor might fill the bill, but experimentation would be required to find a combination that was satisfactory for both criteria. In any case, it would not be as good as true electronic regulation.

    Too much charging, as in leaving the panels connected when the sun is shining and the unit is not being used, will result in 'boiling' the batteries. Even keeping up the electrolyte is no guarantee against their being eventually damaged by over-charging.

    Niel's idea about contacting the manufacturer of the standard 96v "wall" charger is excellent. Perhaps another such unit could be adapted to take input from the panels instead of a transformer/rectifier circuit and regulate the output appropriately.

    Many panels these days have built-in rectifiers to prevent back-feeding of the panels. Check yours specifically.
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