DC - DC Battery charging

Discussion in 'General Electronics Chat' started by Dieseltwitch, Oct 23, 2014.

  1. Dieseltwitch

    Thread Starter New Member

    Apr 18, 2013
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    I have an application that I've been turning on for a bit and not sure if its going to work the way I think it will for it will go poof the second I plug it in.

    Little bit of background here. I live in one of the coldest places in the Continental US: Gunnison, CO. I ride some thing called a snow bike. Its a cross between a dirt bike and a snowmobile (Youtube "Timbersled" to see what Im talking about) Any ways my bikes have electric start. they use a small 12Ah LIFEPO4 battery. In the super cold (down to -35F) they have a hard time starting the motor. Right now I pull the machines out hook up a jumper pack and then crank. this works ok but is a pain the.... What I want to do it hook the bikes to the truck's power system while I'm driving to top them off and warm the up before I ride. I'm not sure how the cold truly effects these batteries but I've found that a simple charge seams to give them their full life back for cold starting. Im guessing that the cold either lowers the battery's output voltage or degrades the amount of current that the battery can provide.

    My question is this: Is plugging the batteries into a system capable of pushing a huge amount of current going to be a problem?

    I've always struggled with the idea of current flow as it relates to usage. I remember dropping a wrench on battery terminals and seeing it go pop. while at the same time hooking up a simple light using 22 gauge wire and having no problems at all. So If i do this with out any type of current control is the battery going to get its top off charge or is it going to go poof like my wrench? I was going to put a 20Amp Aircraft style circuit breaker to make sure that it doesn't actually explode but I still don't want to waste my time.
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    The B6AC RC programmable charger (~$30.00) can be used with 6 types of battery technologies, it has the feature of AC mains or 12v portable operation, I have a Cigar Lighter connector on mine for portable use.
    It has features such as storage charge as LiPo etc should not be left fully charged or flat.
    Max.
     
  3. alfacliff

    Well-Known Member

    Dec 13, 2013
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    chemical reactions like in batteries weaken with cold.
     
  4. Dieseltwitch

    Thread Starter New Member

    Apr 18, 2013
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    That is exactly what Im looking for! I can put it inside a pelican case in the bed of the truck, thank you!

    Im still wondering about how current would flow if I just hooked them together? would the demand battery pull a limited amount of current or would the supply battery push uncontrollable amount of current? Going to use the B6AC. Im just wondering for my own purposes.
     
  5. Dieseltwitch

    Thread Starter New Member

    Apr 18, 2013
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    I also noticed that is saying I must use the balancing leads when using the battery? The batteries i use have the PCB built in the battery... will this cause problems?

    Heres a link to the battery I use http://earthxmotorsports.com/shop/etx12a/
     
  6. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    It would be easier to pull the battery out of the bike and stick it under the heater vent in the truck cab while you are driving to where you use the bike...
     
  7. crutschow

    Expert

    Mar 14, 2008
    13,014
    3,234
    In general, you should not parallel batteries to charge them (such as with the truck battery and the snow bike battery. The one with the slightly lower voltage will take most of the charge, which could be excessive for the bike battery if it had the lower voltage. Better to use a regulator of some type. Or wrap a 12V hot pad around the battery, powered by the truck to warm it up on the trip.
     
  8. Dieseltwitch

    Thread Starter New Member

    Apr 18, 2013
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    Yeah it would't be. Its a pain to remove the battery in a nice garage... don't even want to try to do it in -35F at 2am. I should have mentioned that I work with a SAR team and we go out in the middle of the night to find and look for stranded skiers, snowmobilers, hikers..... so having a machine that starts every time is vital.
     
  9. Lestraveled

    Well-Known Member

    May 19, 2014
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    I would like to second Max's suggestion of using a programmable charger. The charging/float profiles between lead acid and LiPo are very different.

    Also, you might consider attaching a 12 volt strip heater, powered by your truck, to your bikes battery and crankcase. It would improve the bikes starting ability.
     
  10. Dieseltwitch

    Thread Starter New Member

    Apr 18, 2013
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    We've tried it and it really doesn't do much. Most of us run 0-W40 oil and warming the motor seams to make almost no difference at all. We even tried using exhaust to heat up the motor. it wasn't until we started to charge the batteries that thing inproved. we noticed that once the battery was cold, even after rewarming that it didn't put out full power. I think I will be going for the charger also. Do you know what that is simpler that i could just plug in and go. Otherwise I'd have to hit a button each time... again cold. taking gloves off is not fun! Take a look at the photo 50-60mph winds at -30F at 12,300'
     
  11. MaxHeadRoom

    Expert

    Jul 18, 2013
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    The instructions show a Charge mode rather than cell monitored Balance mode if needed.
    So I suspect the Imax would work?
    Max.
     
  12. Dieseltwitch

    Thread Starter New Member

    Apr 18, 2013
    6
    0
    After looking at the system I think i want to try and find a different way. Only reason being I don't want to have to start the charger every time I get in my truck.

    I also found out that the batteries have an internal BMS. could I use just a simple DC-DC Battery charge meant for lead acid? would the BMS no just disconnect once full?
     
  13. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    You'd have to check the BMS datasheet/spec to be sure.
     
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