Charging 12v battery s

Discussion in 'Electric Bicycles' started by mikemason, Jul 15, 2008.

  1. mikemason

    mikemason New Member

    I got my hub kit in & am loving in... (I'll make another post about that latter)

    But they sent the wrong charger (I think, & they haven't emailed back for two days)...

    I've got 3 - 12v, 7ah, 2.1a SLA battery's (for 36v system (http://www.campsolution.com/index.asp?PageAction=VIEWPROD&ProdID=118) and one 12v, 1a supper charger (http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2518) thought I was getting a 36v charger.

    So, I think I can't charge my batterys in series (36v batterys - 12v charger)... but charging one at a time takes 2.5hrs each... so can I charge in parallel? and will that make the chargers auto-stop not work?

    Also, I have a car battery charger with the lowest setting 12v, 10a with no auto-stop, can I use it on my batterys in parallel if I unplug it after 2hrs +/- ?

    Thanks to all in advance, Mike
     

  2. duivendyk

    duivendyk Guest

    The autostop works on voltage and has nothing to do per se with the number of batteries you hook up to it in parallel.If all batteries are used in a series hookup, their state of (dis)charge would be close so you could charge them in parallel (in theory).The charger charges at a 1 Amp rate, so it would take you 7.5 hrs to charge these in parallel.It generally not a good idea to charge batteries in parallel without current equalizing resistors,1 ohm 1watt would be fine.but that would screw up your auto stop (stops before full charge).but you can prob. get away with it if the batteries are clones in every respect.Best scheme use the resistors until charge complete according to auto stop (but not really).Then put charger on each one for maybe about 30 mins (until autostop kicks in)but without the resistor.Forget other charger.If you can't find a 1.0 ohm 5% resistor.you can put let's say 5, 5 ohm ones in parallel ,or 10, 10 ohm ones to, get 1.0 ohm.They can be 1/2 watt.The important thing is that the 3 current equalizing resistors have equal resistance (within 5%), the actual value is not critical.
     
  3. duivendyk

    duivendyk Guest

    There is something amiss with your numbers,it takes 7 hrs not 2.5 hrs to charge a 7AH battery with a 1 Amp charger !,and 21 hrs to charge the lot in parallel from that charger.You should not charge each with more than 1 Amp ! or 3 amp total.If you want to try to use your other charger you need extra resistance in series with the charger(apart from the equalising resistors (or else use larger ones).My guess is 1-2 Ohms.Can only be determined by trial&error I'm afraid.Do you have a multimeter ?.Otherwise you're groping in the dark
     
  4. vegaspaddy

    vegaspaddy Member

    did your chargers come with the kit, if so get in touch with them thats a big screw up on their part.

    this is sort ofcharger you should have received

    http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2920

    i buy tons of bits and bobs from that store (batteryspace.com) for making homemade lights etc, they have excellent customer service and if you need to upgrade drop them a line and they can tell you the proper charger to buy.

    if you havnt already get a small voltage reader (mutimeter) its a must when messing around with the electric kits, a decent one shouldnt cost more than $15.
     
  5. mikemason

    mikemason New Member

    Great reply duivendyk, thanks, I have a multimeter but it's been 15 yrs from the last time I messed with resistors (I'll have to read up again) aways, I've charged the batterys 2 times so far and it takes 2.5 hrs each, I wrote the specs right with a link.... so I don't know why it's amiss (it's7ah & 2.1a dose that fix the numbers?)... but your post will help me alot after I read up some more :)

    Thanks, vegaspaddy, I bought it as a kit but not from batteryspace (although their labels were on the charger) I emailed campsolution to the screw up, yet no after sell reply, maybe they will send me the right one... as in your link, for now I'm charging one at a time.

    Thanks again guys!
     
    Last edited: Jul 16, 2008
  6. vegaspaddy

    vegaspaddy Member

    man that sucks, you could also tell them you are reviewing their product in this fourm with X amount of members, from previous experience if they care about their business in any shape or form it always tends to get them to pull their fingers out of their asses so to speak.
     
  7. duivendyk

    duivendyk Guest

    With a 1 Amp charger you can't charge a 7 AH battery in 2.5 hrs,either it's being charged at a higher rate or it's not fully charged or it's not a 7AH battery,or any combination of thse assumptions.The conservative rule of the thumb used to be,charge at about 10% of capacity.
     
  8. duivendyk

    duivendyk Guest

    Another possibility,it's not fully discharged,that's the most likely one!
     
  9. mikemason

    mikemason New Member

    ya that's probably it :grin:
     
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