12 volt to 36 volt converter

Discussion in 'Tech/Mech General' started by Snowbird, Jul 10, 2011.

  1. Snowbird

    Snowbird Funster Life Member

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    I have 2 X electric bikes that are 36 volt, I would like to charge them directly from my 12 volt leisure batteries.
    I don't want to charge them from an inverter as there is already an inverter in the original power supply lead.
    Has anyone ever done this to charge a bike,buggy,wheelchair etc.
     
  2. pappajohn

    pappajohn Funster Life Member

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    see my reply on RVOC Dave :thumb:
     
  3. scotjimland

    scotjimland Funster Life Member

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    Hi Dave... 12vdc-36vdc step up converters are produced by rather pricey ..

    but in any case, that's just adding another bit of kit that uses power....

    what is your objection to using your existing inverter with the bike charger ?
     
  4. Snowbird

    Snowbird Funster Life Member

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    Hi Jim, My main objection is that I only run a small inverter,300 watts.
    I don't think this would be man enough to charge the bikes for the amount of time required to charge them, and of course there's the voltage loss issue.
    Also the bike mains chargers that came with them have an inverter already built into them,so there would be a lot of wasted power running the two inverters if you follow my meaning.
    I just thought it would make more sense to charge directly from my 12 volt supply using a stepup converter. Am sure there are others in a similar predicament,ie wheelchair users and because of the increase in the use of electric bikes.
     
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  5. scotjimland

    scotjimland Funster Life Member

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    What's the power rating of the bike chargers Dave ?
     
  6. Snowbird

    Snowbird Funster Life Member

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    Hi Jim, The power rating is...Input 230 VAC 60/50 Hz 3 amp.

    Output VDC 2 amp.

    Thanks for the imput pal.
     
  7. scotjimland

    scotjimland Funster Life Member

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    Hmm .. input power is 230v x 3a = 690 watt

    and output power is 36v x 2a = 72 watt ,,,doesn't add up ..

    I think the 3 amp input quoted is a nominal figure .. perhaps the fuse rating ? , without testing it's hard to say .. but, if that is the case then your 300watt inverter is plenty big..

    have you tried it on the inverter ?
     
  8. Snowbird

    Snowbird Funster Life Member

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    Sorry Jim, misread in the dark of the garage.

    Input 115/230 VAC 60/50 HZ 3/1.5 Amp

    Output 36 VDC/2 Amp.

    Maybe its for 110 volt or 230 volt.

    Do you think my inverter would run it without to much wastage.
    I would still of course prefer to charge direct from my batteries.
     
  9. scotjimland

    scotjimland Funster Life Member

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    That makes better sense ..

    Inverters are around 90% efficient .. but no matter how you convert there will be a loss.... no electrical kit is 100% efficient .

    sorry, that's all I can suggest .. maybe Brian will have a brighter idea.

    How about just using the genny .. :Laughing:
     
  10. Snowbird

    Snowbird Funster Life Member

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    Yep I could use the genny but the batteries take up to 6 hours to charge and my genny is 6 KVA.:Eeek:
    I have enough solar panels and a big enough battery bank to charge the bikes so I thought I could get something wired up to charge them from the battery bank. Papajohn found something on ebay that would do the trick but its damned expensive.
    I know I cant take it all with me but am trying to hang onto as much as possible.:Rofl1:
     
  11. hilldweller

    hilldweller Funster Life Member

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    I saw you and PJ and knew I did not need to comment, but since you ask :Smile:

    First terminology.

    An inverter takes in 12(ish) DC and outputs standard 240V(ish) AC.

    A CHARGER usually takes in 240V AC and outputs a suitable volts/current profile for the battery it is sold with. 36V could be Lead Acid or Lithium. Vast difference in charging profile. Neither will output 36V. If lead acid it would of course be 14.5 * 3 = 43.5V.

    So there is only one way, Inverter --> Charger.

    Yes, this will incur a conversion loss but that's the deal.

    Inverter size ? 36V 2A so ball park 100W each charger.

    Load on 12V ? Say 10A. 6 hours mentioned. 60Ah each. Better have BIG batteries and the means to recharge them.

    Usual dilemma - what type of inverter do you trust to plug the charger into. At least the chargers should not be mega expensive so to plug in one is probably an acceptable risk. A 300W inverter should do it.
     
  12. Snowbird

    Snowbird Funster Life Member

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