Lithium Polymer cells, used mostly in the e-bike community to describe soft-pack RC like cells, generally have a lighter weight per watt-hour, and they have a high percentage of cobalt in its anode, which makes them very power-dense (lots of amp-hours in a small package) and also capable of very high amps of discharge (for high performance). Single cell LiPos are connected together in series to form a battery pack.

More than likely this problem is BMS related. The BMS usually trips in that scenario for one of two reasons: 1) The load pulled by the controller is too high for that BMS, or 2) one or more cells are weak or damaged and when the load is applied strongly, it causes the voltage of that parallel group to drop below the LVC of the BMS.

[74V, 89V, and 104V @ 13Ah are available by connecting 2 batteries below in series.  37V 26Ah and 52V 26Ah are available by connecting 2 batteries below in parallel.  Instructions provided upon request.]

Different batteries have different amperage capacities. Most cheap lithium batteries are not capable of putting out much amperage. If you have a 48 volt bike that performs well when using 25 amps, you are going to want a 48 volt battery that has close to a 20-Amp-hours or more.  If you want to eventually hot rod your ebike (read our hot rod hub motor primer here), you may want to  invest now in a high amperage battery. This will “future proof” your system by paying a little bit more now for the battery, but then you can program more performance from the controller in the future, if you want…

I then took my second sense wire (or your third sense wire if you have one more sense wires than parallel groups) and soldered it to the positive terminal of the second parallel group. Again, note that I’m soldering this wire to the nickel in between cells to avoid heating any cell directly.

What does that mean?. Well, it is like having another fit bicycle rider helping you pedal, but without their weight. No matter how hard your hills, or heavy your bike is, this motor will always work t…

I’d recommend going with a cell that can output 10A, giving you 40A continuous power rating. You’ll use less than that, meaning the cells will be happier (and cooler). Something like the Sanyo 18650GA or LG MJ1 would give you good power and capacity (both are around 3,400 mAH per cell).

NiMH-Nickel Metal Hydride. This was the battery of choice for military application and the first-gen Prius hybrid car. Very reliable and stable, with a long cycle life. It has a high nickel content, so its expensive now (but the nickel can be re-cycled). With a low C-rate, you need a very big battery to draw high peak amps. Perhaps not a problem on a car with its huge battery pack, but on a bicycle, the smaller pack restricts the user to low amp-draw performance.

Also changing the fuse to a higher one could cause the wires to start a fire and the whole house would burn down if batteries for e bikes wires are not thick enough. Also in sweden a fuse gets bigger as they are rated higher so you can fit a 20A fuse in a 10A slot, for safety.

One of the first advantages of lithium batteries is their small size. You can fit a lot of lithium on a bicycle frame. This alone can give your ebike some seriously impressive range. Two or three mid to large capacity lithium batteries could easily fit on one ebike, giving potential ranges of 100 miles (160 km) or more. I guess this would be great for people that don’t mind sitting on their bike for three to five hours at a time, or that for some reason don’t want to charge up for weeks (hey, when riding your ebike through a zombie apocalypse, the last thing you want to be doing is searching for an outlet).

You’ll also notice in the following pictures that my charge and discharge wires are taped off at the ends with electrical tape. This is to keep them from accidentally coming in contact with each other and short circuiting the pack. A friend of mine recently tipped me off to another (and probably better) option to prevent shorts: add your connectors to the wires first, then solder them onto the pack and BMS. Doh!

I am just trying to install a battery on a velomini 1 that I traded for. I don’t have a problem using the above battery as a hang on battery, but don’t know if it has the BMS in it or if my current charger would charge it. It is pretty cheap.

For example, suppose you see a 24V 4Ah NiMH battery pack on ebay, that is rated for 1C continuous and 2C max for short times. You might want to get two of these to make a 48V 4Ah battery for your ebike. You calculate that the range will be more than adequate for your short commute to work and back. The problem is that 1C is just 4 amps, while your ebike will probably draw 10-20 amps. If these cells are subject to such discharge rates, then the voltage will sag considerably, leading to slower performance, and the cycle life of the packs will be greatly reduced.

I’m mostly familiar with BesTech’s 72V BMS’s and haven’t used a 52V BMS from them, so I can’t give you a recommendation on a specific 52V (14s) BMS from them, sorry. I have used this 14s BMS twice and it’s worked great for me on two 14s7p packs I made with Samsung 26F cells.

For discharge wires you’ll want something bigger, like 14 awg silicone wire. 12 awg would be better but might be overkill for your use. For charge wires, 16 awg silicone wire would be fine and you could probably get away with 18 awg silicone wire.

If you charge batteries off the bike, I suggest doing so on a metal rack that has wheels on the bottom (very inexpensive at hardware stores) whith the battery(s), and chargers on the rack. In the event of smoke, bad smell, or fire, you can shove it out the door quickly. Locate it closest to a doorway that you can use to eject the battery easily, quickly and without coming in contact with the burning material or breathing the fumes. Consider how you would get a bike out the door. I have a boat hook that could be used to drag just about anything outside, and it is ~2 meters long.

I guess I’ll just have to risk some deterioration on the cells. I don’t think there’s much of an effect, as I did it on an old 18650 cell to test. The joint and surrounding areas were cool to the touch within 1-2s of removing the heat.

Lithium batteries are also small enough to allow you to place your batteries pretty much anywhere on your bike. This is especially true for people who want to assemble their own pack or use heat shrink wrapped lithium batteries instead of hard case lithium batteries with prefabricated bicycle frame mounts. This can help spread the weight around or hide the batteries to make a stealthier bike.

A big downside of lithium batteries is that they are much more expensive than lead acid batteries. Prices vary depending on the voltage and capacity of the lithium battery, but standard ebikes usually have lithium batteries starting in the $300 range and rising quickly from there. Most bikes I build have lithium batteries in the $400-$500 range.

The other thing to consider is that if you have one 48-volt 10-Ah battery putting out a measly 20 amps, you can add a second version of the same battery, wire them together in parallel, and you will have a 20-Ah pack with a 40-amp capacity, thus effectively doubling your range and doubling your amp output performance. [redirect url=’’ sec=’7′]