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  1. #1

    Battery chargers

    My chair originally came with a 24v 4amp on-board charger. Lately I've been using a 24v 4amp off-board charger (it has 2 NF22 batteries). I just bought a set of MK 22NF Gel batteries. They suggest using their 24v 8amp charger but I'm not willing to use a 8amp charger on a chair that was wired for 4amp charger. But when I search for replacement chargers for my chair there are a lot of 24v 5amp chargers listed. So I ordered a 24v 5amp charger designed for Gel batteries(I actually got it today but it was the model for AGM batteries, it has a higher charging voltage, so I'm sending it back). Does anyone think using a 5amp instead of a 4amp will cause problems with my chairs wiring? I talked to the people who make the charger and they said a 5amp charger was a minimum I should use and my 51ah batteries and 51ah batteries was the max a 5amp charger could handle. Makes me wonder how my 4amp charger managed. Anyone have any experience with this type of situation???

  2. #2
    What make/model is your chair?

  3. #3

  4. #4
    From what I found out you're correct in that a 4 amp charger should be used.

  5. #5
    Thanks Rusty,

    your probably right, that's definitely what the chair was originally equipped with. But both MK Batteries and Universal Power Group (the people who manufacture the charger) recommend a higher Amp charger. I'm not going to use a 8amp as MK suggested but I'm going to go to try a 5amp. If it screws up my wiring I'll post back.

  6. #6
    You'll probably be ok with the 5 amp, but I wouldn't charge it unattended. You could charge the batteries at higher amps but you would need to run heavier cables to the batteries.

  7. #7
    Well, I got my new MK 22NF Gel batteries

    I got a new UPG 24v 5amp charger for Gel batterries. I checked my batteries after being charged and they both measure @ 13.3v

    The next day after I used my chair I charger my batteries using the 24v 4amp charger that came with the chair. The batteries both measured @ 13.5v.

    To be honest I can't seem to find out which charger to use to get the longest life span out of the batteries. I don't mean for a single charge, I mean the longest span before having to replace the batteries.

    Any experts out there????

  8. #8
    Are you letting them sit overnight after charging, then checking the voltage?

  9. #9
    Rusty, Thanks for the reply.

    I checked the voltages probably 3hrs after they were done charging. Both chargers have float charging so wouldn't they stay fairly close to that voltage?

    I was just looking at the battery specs and they're suppose to Float at 13.4 - 13.6. It looks like I might have bought a charger with to low of float.

    I can use the on-board charger, it will take longer to charge but that's not a problem, I usually only use my power chair 2-3 hours a day when I'm away from the house. But I'm worried about what voltage it charges at, because Gel batteries need to charge at a lower voltage than AGM. I haven't been able to find those specs for the on-board charger.

    Beside the obvious fact that a battery 13.3v has less stored energy than a battery with 13.5v, I'm curious what effect that has on the life of the battery.

  10. #10
    If it's an onboard charger it should be fine for the gels. Try using the different chargers but next time let them sit over night and see what you have. Regardless, we're not talking much difference here. Be happy that it seems like you got a good set of MK's!

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