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Replacing a lead acid 12 volt battery with a Lithium ion Polymer battery

  1. Feb 24, 2009 #1
    I got this idea that I could maybe replace the heavy lead acid battery on my motorcycle with a lithium ion polymer battery. I found that you can buy batteries for RC cars that match the power requirements. The lead acid battery is 12 volts, 6Ah. It seams that L.I.P. batteries for RC cars are either 11.1 volts, or 14.4 volts. I was thinking maybe this battery would work, and I could connect the wires from the alternator to the L.I.P. charger. Am I way off base? Would this work? First off 11.1 volts isn't 12 volts. But, the voltage in an AC system varies and doesn't hurt anything.


    Anyways, tell it to me strait, is this possible, or just a stupid idea?
    Last edited: Feb 24, 2009
  2. jcsd
  3. Feb 24, 2009 #2
    Doubtful that anything on the bike is particularly voltage sensitive. The charging system is the real issue. You can't safely connect the Li-Poly directly in place of the lead-acid unit.
    But, since you will need to design a suitable charging circuit, might as well incorporate a DC-DC converter the bring the volts up to spec, too.
  4. Feb 24, 2009 #3
    Thanks for the input. I'm going to look into it. The charger they sell for the battery has dc input of a wide range of voltage. Would it be suitable to disconnect the connection between alternator and battery, and wire in between. Also, is it even safe to charge while it is drawing current?

    If something goes wrong, how bad would it be if it exploded?
  5. Feb 24, 2009 #4
    I know car batteries are designed to supply a huge short term current while cranking the engine. They have a rating for cold cranking amps (CCA). I don't know if another type of battery would be capable of delivering the amps needed to start the engine. I'm not certain this applies to motorcycles, but I would assume it does.
  6. Feb 24, 2009 #5
    I have a lot of experience with lipo batteries so believe me when I tell you that you don't want to use them in your motorcycle. They are very temperamental, difficult to charge, don't like continues high current draws, and require a lot of maintenance. If you get your charging circuit wrong or stall the starting motor on your bike, here is a glimpse of what will happen.

    http://video.google.com/videosearch?hl=en&q=lipo%20battery%20explode&um=1&ie=UTF-8&sa=N&tab=wv# [Broken]
    Last edited by a moderator: May 4, 2017
  7. Feb 24, 2009 #6
    I would stick with lead acid.
  8. Nov 25, 2009 #7
    Pertaining to the same subject concerning standard motorcycle 12v-6amp battery.
    I have a Yamaha Enticer 125cc. Standard electrica system with a approx. 44 watts total requirments for all lights, etc.
    What I need to do is add two halgon - 55watts X 2=110 watts to my system.
    Obvisiously the 12v -6 amp will not support the extra wattage.
    Can some please inform me how to resolve this issue? I need to add two additional halogen lights to my motorcycle.
  9. Feb 1, 2010 #8
    Lithium batteries are really different from lead-acid. There's the problem of charging them, first. You can't just plug them in where you had a lead-acid battery. I looked into a similar problem like this before. Once you've got a microprocessor to monitor the charging process, then there's the difference in how lead-acid batteries respond. In a car or motorcycle lead-acid batteries charge over a long time and then discharge for a short time. Lithium batteries were invented with a different purpose in mind. So I'm guessing you will have a different life-span on your alternator, if you change to lithium batteries. I've got a friend in Hong Kong who races electric motorcycles professionally and I could set you up to talk to him. I'm sure people who use electric bikes would understand what you are trying to do better than most other people.
  10. Feb 19, 2010 #9
    I'm sure that I don't understand the intricacies of an electrically powered vehicle.

    For those of us seeking to improve the capabilities of our gas-engine motorcycles using newer battery and electronic technologies, there is a quite different paradigm. A raft of us are uneducated about anything much more than maintaining our bikes' original systems and replacing the occasional component with something improved.

    Motorcycles which rely on electric motors for starting have a momentary requirement for high current draw at relatively consistent voltage and must plan both charging and storage systems around those requirements. Electric start motorcycles concede the issues of somewhat massive (some would say robust) systems which can be manufactured at low cost. Accessories - ignition, lights and horns, instruments, cooling fans, electronics - including electronically augmented fuel, braking, transmission, and suspension controls, and power connections for rider heating and communication accessories are easily engineered into the circuitry attendant to such massive generation/storage systems. It's not that technology hasn't advanced in the arena of electric start systems - they have grown first to be reliable, second to be durable, and third to be much less penalizing in space and weight terms.

    Motorcycles not having an electric starter motor offer a much different set of issues more conducive to address by advanced battery and electronic technology. Older motorcycles relying on lead/acid battery supplied current to operate other accessories could benefit from weight reduction by a lighter battery and a system not as subject to failure from vibration. More modern motorcycles designed to operate without battery are generally confined to rudimentary accessories, i.e. minimal lighting and instrumentation.

    My own interests fall into both the latter categories, a kick-start bike with a battery system and one without. My interest is modernizing their electronics to take fullest advantage of native generator/alternator output - something very hard to change - to provide for upgraded lighting, instrumentation, and power for other accessories such as GPS devices, radio, and, ideally, heated clothing.

    I would really appreciate a dialogue with someone who's been down this route or whose understanding of the constraints I face makes patient allowance for my shortfall of understanding electricity. I like to think I'm a quick study, but I need to know what to study.


  11. Feb 19, 2010 #10
    I'm not that educated about it either, but I might have some answers. I mostly looked into using lithium batteries because my hobby is solar power. I currently have enough lead-acid batteries and solar panels to run my washing machine twice a week off solar, which is putting a serious dent in my electric bill. And the setup I have didn't cost that much! But I had to figure out basic electronics as I went along. Now I'm trying to get some engineers to walk me through putting my product together and getting it on the market: http://wat.asiaeast.org

    Lead-acid batteries work really well because they've been around forever and everyone has most of the problems worked out. But like you know, they are heavy and take up room and have other problems. It hasn't happened yet, but I'm pretty sure everyone will be using lithium batteries some day in the future, just like you are suggesting. Imagine plugging something the size of the backup battery on your laptop into your motorcycle and then recharging it again overnight. That approach might work, but I don't think you can recharge a lithium battery from the motorcycle engine directly.

    The problem with lithium on a motorcycle is this:

    Lithium batteries charge in two stages. First, a microprocesor applies a predetermined current and then raise the voltage until the maximum voltage required is reached. At this stage, if you disconnect your battery, it will appear to be full. But in fact, the battery inside really isn’t.

    During the second stage, current continues to flow into the lithium battery until it drops to 0. This usually means there’s no more room in your battery for electricity. Microprocessors for lithium batteries are programmed to assume you are going to leave the battery charging until it is full.

    But, if you are recharging the battery on a motorcycle, the flow of current could stop simply because you switched the engine off. This would lead the microprocessor to think that the battery was full, when in fact it wasn't. Because it tracks where the battery is at in the charging stage, if you unplug it before you finish charging, the chip can lose track of where in the process you were.

    At this point, you will need to reestablish where in the charging process you were. That's why I suggest unplugging the battery from the bike every time you are done and recharging it from the wall. This will reset the parameters inside the microprocessor again. After that, things should remain stable.

    With my ipod, for example, I plug it into a solar panel. When the sun goes behind a cloud, the flow of energy drops to 0 and the ipod thinks the battery is full. It will even say "Charged" on the display. When I unplug it from the solar panel, the lithium battery is still empty!! That's why I have to recharge my lithium battery from lead-acid batteries or recharge on a day when there's no clouds in the sky.

    So on your motorcycle, unless you can reprogram the chip somehow, everytime the battery looks low, the alternator will start to pump out juice, right? But if you turned the engine off while it was recharging, the microprocessor would think the battery was full. Then, when you turned it on again, the microprocessor would never send out the single to the alternator to start pumping again. Eventually you'd have a dead battery.

    Like I said, I'm not educated about this. However, my experiments with lithium tells me I'm pretty close to correct.

    Probably best to recharge the lithium independently of the engine. Also, can you run a lithium battery for lights and radio, etc. and a smaller lead-acid battery for starting?
  12. Jun 22, 2010 #11
    I have an xTreme mobility scooter, and live in mountainous (hilly) terrain. My scooter uses 4 12volt lead acid batteries. I would like to replace them with something that weighs less, and can travel farther and/or longer. I would also need information about the correct type of recharger to use over night plugged in to USA 110 AC current. The scooter people insist it be 48 volts to work with their controller, etc.

    Help from anyone with experience using electric bikes or scooters would be appreciated.
  13. Nov 18, 2010 #12
    That would be a great tips for owning an RC cars and choosing the right batteries for your RC cars just like choosing the Motorcycle battery on your motorcycle.
  14. Jul 30, 2011 #13
    SSCONDRON. Did you ever resolve your XTREME battery issue? I have the XTREME-5xx model and the batteries are shot. I don't get enough power to get up a certain hill and thus when replacing the 4 12Volt-14Amp batteries, I would like to increase power and not so much duration. I am contemplating purchasing 4 12Volt-22 Amp batteries but have been told this will only increase duration in the current configuration. the XTREME-6xx and 7xx have these increased AMP batteries yet they can get up the hill (so I am told). What is the other factor? Thx
  15. Aug 19, 2011 #14
    I did this type of conversion about 1 year ago. I bought a lithium battery (12v 10Ah) for about £80 on ebay, already prepared as a straight swap for the lead acid battery, works a treat, the cranking power is amazing.
  16. Aug 20, 2011 #15
    I think I would avoid using Li-Ion as a gas powered motorcycle battery. They are tempermental and if there's a problem, the batteries can catch fire.

    When running Li-Ion cells in series packs, there are balancing issues that can arise normally dealt with by using a "balancing" charger. So, to replace the lead acid battery in a gas powered car or motorcycle, you would need a balancing charger for the battery plus the necessary protection from over-current and over-discharge.

    People do use Li-Ion "pack" chargers that simply treat the battery as a higher voltage single cell, but that's not the proper way to charge a Li-Ion pack. Using that method can lead to battery performance and safety issues.

    For electric vehicles, they're a best fit because of their high energy density. The level of electronics required to keep them safe is pretty much assumed. If you're going to replace lead-acid with lithium-ion for an electric vehicle, you'll need a level of electronics to go with it. Doing it partially or improperly will lead to safety issues. When these batteries go, the event can be fairly violent.
    Last edited: Aug 20, 2011
  17. Dec 1, 2011 #16
    Be careful about grouping all lithium batteries into one group, there are actually many different chemistry mixes involved. Traditional Li-Ion batteries are a no-no for replacing lead-acid in motorcycles.

    The ones available on the market for this application are LiFePO4 - Lithium Iron Phosphate. This is a very stable configuration and very tolerant of abuse that would cause a Li-Ion battery to explode. Main benefits are weight-savings since they weigh only 20% of what a lead-acid would for the same capacity. And take up about 50% as much space.

    Some vendors:
    http://www.lifepo4-battery.net/lifepo4-motorcycle-Battery.html [Broken]
    http://www.raitbattery.com/html/en/product/PowerBattery/c371.html [Broken] (48v 30ah battery for electric vehicles)
    Last edited by a moderator: May 5, 2017
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