20″ 250W 36V White Folding Electric Lithium Battery B ike. Motor: 36V 250W Rear Hub Motor. The 20” Sheep is a 36V 7AH Lithium Battery powered Electric Bicycle. This Folding Electric Bicycle is the per…
Also changing the fuse to a higher one could cause the wires to start a fire and the whole house would burn down if the 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.
I haven’t seen that exact BMS in the flesh before, so I can’t speak too confidently about it. The description claims it has a balancing feature and so I assume it does, but I’ve also seen BMS that were supposed to have balancing capabilities, but arrived with the balancing components missing from the board.
You can actually buy an E-bike NMC pack right now, but it remains to be seen which retailer will prove to be the most reliable. An NMC pack will be about 25% smaller and lighter than an equivalent LiFePO4/LiMnO2 pack. The extensive testing done by Zero, Tesla, and Nissan gives us a great deal of confidence in the safe and effective use of NMC over the next year…
One term you will frequently come across is the ‘C’ rate of a battery pack. This is a way of normalizing the performance characteristics so that batteries of different capacity are compared on equal terms. Suppose you have an 8 amp-hour pack. Then 1C would be is 8 amps, 2C would be 16 amps, 0.25C would be 2 amps etc. A higher ‘C’ rate of discharge is more demanding on the cells, and often requires specialty high rate batteries.
An older battery technology that was popular around 10 years ago as replacment for lead acid in some more expensive commercially available e-bikes. Today it has been obsoleted in e-bike applications because of the recent availability of LiPo and LiFePO4 cells. NiMH is a finicky technology to deal with. The packs do not have long life expectancy, and have to be treated delicately. One big problem https://en.wikipedia.org/wiki/Electric_bicycle DIYers is that its very hard to safely charge NiMh cells that have been soldered together in parallel. Extra care is needed for NiMH in both assembling and charging.
The only two ebike companies that sell LiPo to the public are Optibike and Pi-cycles, and both contain the battery in a strong metal box which makes up of the frame. The companies fire tested these enclosures and are confident that their frame are effective and safe vessels for LiPo storage.
In general, the size and cost of a cell will scale directly with its amp-hour capacity. To a first order, twice the amp-hours would mean twice the size, twice the weight, and twice the cost. In practice this deviates a little due to different packing densities and production scales, but it’s usually pretty close. For instance, the familiar ‘AA’ NiMH has about 2 Ah, a ‘C’ cell has 4 Ah, a ‘D’ cell is about 8Ah, the large ‘F’ cells are 12-13 Ah, and double-D cells are 18-19Ah.
The spacers you linked to make battery building a bit easier as you can set it up modularly, but as you indicated, they add a good amount of volume to the battery. I like to make my batteries as small as possible so I rarely use them. When I do, I use these ones, but it’s not very often.
Another advantage of lead acid batteries is their high power output potential. Lithium batteries generally don’t like to handle too much current. SLAs, on the other hand, can provide huge amounts of current. If you are planning a very high power electric bicycles, SLAs might be a good option for you.
As far as dimensions, I prefer to use 0.1 or 0.15 mm thick nickel, and usually use a 7 or 8 mm wide strip. A stronger welder can do thicker strip, but will cost a lot more. If your welder can do 0.15 mm nickel strip then go for it; thicker is always better. If you have thinner strips then that’s fine too, just lay down a couple layers on top of each other when necessary to create connections that can carry more current.
RC packs may be fine for enthusiasts that know what they’re doing, but even telling others about them scares me! FIRE! And secondly, they typically don’t have any BMS so don’t have any inherent protection from over-under voltage or balancing. FIRE!
Note: At multiple points along this article I have inserted videos that I made demonstrating the steps involved in building a battery. The battery used in the videos is the same voltage but slightly larger capacity. The same techniques all still apply. If you don’t understand something in the text, try watching it in the video.
To determine how much power you need, you’ll need to determine the voltage you want and the capacity you need to supply that power (voltage times current). Read this article to learn more about calculating your ebike’s power: http://www.ebikeschool.com/myth-ebike-wattage/
The battery’s placement on the bike depends on different factors, especially the shape of the bike’s frame. Most electric city bikes (more than a half) will have the battery mounted on the carrier rack, while mountain bikes usually have them on the down tube.
In the end, I opted for a DPDT+OFF rocker switch, as using diodes introduced forward voltage drop and this interfered with charging enough for me to have second thoughts. This arrangement does require that the BMS be “flashed” to initiate it, which can be done by the charger in charging mode but for discharging, I found that shorting the B- and the P- for less than a second initiated the BMS and it then latched itself on, so I installed a reset button. If I had used a DPDT switch without an off position then I would not have needed to do this. However, when the BMS hits a low voltage group e.g. going up a steep hill, it will not automatically reset when the voltage recovers, so you need to use the reset button if you want to get the last bit out of the battery. I’m toying with latching this button when discharging, as the voltage drop knocks the controller out, so I think I’ll get a reaction like traction control, without having to manually reset the battery (which is annoying as it’s in a backpack).
9S, 32.85VDC, 2890MAH, 94.93WH. THE ENERGY DENSITY OF THESE CELLS ARE SPECTACULAR. YOU GET A POSITIVE AND NEGATIVE LEAD WIRE AND ALSO BALANCE CONNECTORS IF YOU WANT TO BALANCE THE CELLS. IF YOU BUILD …
Ideally, I would buy a battery with the same type of connection and just carry the spare one unconnected and swap them over but I don’t seem to be able to find the type of battery case for sale anywhere. It’s a quick release bottle type battery that has two sprung terminals about half inch in diameter that contact with two large terminals on what I think must be the motor controller integrated into the bottom of the bottle mounting bracket.