“scooter with battery +bike battery”

Rang: 18-25km(36v 6ah). Motor: 36V 250W brushless. Battery: 36V4/6AH lithium battery. The eco-friendly bicycle is 100% electric and emissions free, saving both your wallet and the environment. New Out…

Having built a 13s4p battery to the best of my ability and hooked it up to my 48V 1000W ebike conversion kit…. the lights on the throttle turned on and the wheel spun! Initially I thought the project was a success but after mounting the battery and controller onto the bike and taking the bike for a test spin I ran into a major problem.

Since you mentioned the charger, the link you sent me came with a 2 amp charger but it would take 10 hours to charge that size battery. Could I use a larger amp charger like 5 or even more for faster charging? How do you tell what is too much so you don’t damage the battery? Thanks!!

18650 cells, which are used in many different consumer electronics from laptops to power tools, are one of the most common battery cells employed in electric bicycle battery packs. For many years there were only mediocre 18650 cells available, but the demand by power tool makers and even some electric vehicle manufacturers for strong, high quality cells has led to the development of a number of great 18650 options in the last few years.

If any one battery cell varies significantly from the others, do NOT connect it to the other cells. Paralleling two or more cells of different voltages will cause an instantaneous and massive current flow in the direction of the lower voltage cell(s). This can damage the cells and even result in fire on rare occasions. Either individually charge or discharge the cell to match the others, or more likely, just don’t use it in your pack at all. The reason for the voltage difference could have something to do with an issue in the cell, and you don’t want a bad cell in your pack.

Thank you very much for quick answer. You give me a good advice and I will use it. To sum up, now I am on the cross Li-ion or LiFePO4, can you sugest me some othre examples like Panasonic 18650 which you tested and you clame are good batterys? For BMS, is there special tipe which are good or there is no different or just like you says it must be for a bit stronger etc. batterys give 30A we must have a bit stronger BMS like for 40A?

I love this article and I am inspired by the knowledge here, I have a question, I need to build a 72v battery and the one I’m looking at is using 38160 cells, these cells are very expensive so how can I manage this the best using the smaller normal size cells like you’re using! Do I really have to make a battery 20 cells deep to reach this and to bump up the amp hours I would let say go 10 wide for a 30 amp hour right? Pretty close! Big battery but is it feasible or is there a better product

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Regarding your second question: I wouldn’t say the max amperage of the BMS is “dependent” on the controller, but it should be chosen with consideration to the controller. Think of it this way: your controller is what decides how much current your battery is going to supply. The controller is basically pulling that current from your battery. If it’s a 20A controller, that means the most it will pull out of your battery is 20A. So if you plan on riding in a style that uses full power for long periods of time (like hill climbing, dirt riding, etc) then you’ll need to make sure your BMS is rated at least 20A continuous. However, most people that ride on flat roads spend very little time at peak current. My ebike’s controller is a 22A unit, but I spend most of my time around 10-15A when cruising. A 20A continuous BMS would be good insurance in that case, because it means my BMS is rated to handle more continuous power than I generally will pull through it.

Next, I added the third parallel group after the second, hot gluing it in place in the same orientation as the first, so the top of the pack alternates from positive terminals to negative terminals and back to positive terminals along the first three parallel groups.

my questions are obviously related to sla’s as this is what i have now but if answers differ according to battery chemistry i would like to know this as well for future reference any info much appreciated cheers craig

The figure that matters most when comparing how far a given battery pack will take you is not the amp-hour capacity but the total energy stored watt-hours. To make things more familiar, one watt-hour is one-thousandth of a kWh, the unit of energy used to measure household electrical usage. The watt-hours stored in a battery pack is approximated by taking the actual amp-hours and multiplying it by the pack voltage.

For any other case, lithium batteries’ advantages greatly outweigh SLAs. Of course, for your specific ebike you might have other reasons that could sway you either way. At the end of the day, your ebike is all about you. I hope this information helps you make the right choice for your own battery needs.

We like to use Anderson Powerpole connectors as the standard discharge plug on all of our ebike battery packs. These connectors are ingenious since they are genderless, allowing you to use the same plug both on both a load and a source, and the connector design allows them to withstand the arc of inrush current when plugged into capacitive loads much better than bullet style plugs. For the charging port, we like to use the female 3-pin XLR plug standard. This is directly compatible with the Satiator charger, and the quality Neutrik XLR plugs are rated for a full 15 amps per pin allowing very rapid charging. Unfortunately, this option is not available for the smaller Hailong frame batteries and we are forced to use the lower current DC 5.5mm barrel plug instead.

40% grade hills? That’s huge! You’ll definitely want a cell that can perform at high current since you’ll be pulling peak power from those cells to get up those big hills. Something like the Samsung 25R would be a good choice for this application.

Hello Micah: Thanks for this most interesting and useful article! I want to build a battery in a 39mm x 520mm seatpost for fueling a 250W motor that normally uses a 7.2 Ah – 25 V bottle-shaped battery. The new seatpost battery should only have an autonomy of 7 miles of steep hills (40%) between each daily charge. What are your recommendations? Happy day! Fred

I just found your article, and as if it were destiny, this is exactly what I am trying to do (build a battery pack with BMS, and charge with charger). I am new to this, however, and have a question or two…

This is the old technology for e-bikes that is heavy as bricks and does not have longevity. Lead acid will double the weight of your electric bike. Unless you have to because of money restraints, we advise to steer way clear of lead acid batteries.  Your bike will have a completely different feel and range if you spend the money on one of the new lithium technologies.

I’m a little worried that your batteries aren’t what you think they are. If they really are AA sized, which is rare in the lithium battery world, then they are not 3,000 mAh. Next, 10 cells in series is going to give you 36V, which is twice what batteries for electric scooters replacement 18V drill is rated for. 5 cells in series and 2 in parallel would be a better method. I usually recommend a BMS but you can skip it if you have another way of diligently monitoring your cell voltages and then charging using an RC style balance charger like an iMaxB6 charger through an JST-XH connector.

Interesting that they claim the controller is balancing the two batteries. I highly suspect that is false, and just marketing fluff, but who knows. They probably have a simple diode built into the internal battery. I checked with a friend and he reminded me that it would be a good idea to include a diode in the discharge cable of your auxiliary battery. That way if you ever plugged in your auxiliary battery when it was low on charge and the bike was fully charged, the bike wouldn’t try to charge your auxiliary battery in reverse.

RC motors and RC batteries used what E-bikers considered to be fairly lower voltages (14V-22V), which RC enthusiasts needed in order to keep the batteries small in the compact RC planes. The number of E-bikes outside of China is low compared to the the number of global RC products. People who would never ride a bicycle under any circumstances might have several expensive RC models. Since RC components were designed to use lower voltages, the users tweaked their systems to draw more amps for better performance. RC buyers didn’t care about the occasional fire (a rare event), they wanted higher-amp batteries.

I have an unrelated problem. I am prototyping a 1/3 scale model of a top fuel funny car.It’s 5 ft long, 2ft wide, wt. is approx. 100lbs.. I need to go 120 mph in under 4 seconds in 333 feet. Will the 5405 mtr. suffice? I know your going to ask alot of tech. questions but thats all I have for now.Any help in this quest for speed is greatly apprecated. Thank you robert lathrop

One Reply to ““scooter with battery +bike battery””

  1. i noticed that bms installation is different (as i guess) from the video (https://www.youtube.com/watch?v=rSv9bke52eY&index=10&list=LLDXj2cy8mbQoc0dz3RO3zFw) i have watched before. In this video bms wires were connected on the negative poles of batteries lifepo4. In my amateur opinion i could not understand how we organize BMS connections for my 13s pack. if you illuminate me, i will be preciated.
    As you sugested in one of your articles, using lead acid is a great way to prototype the build, so if I am happy with the performance if not the weight of the lead-acid, I can convert to lithium in the future and save some big weight.

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