jucasan said:
Sorry about the link
https://bafangusadirect.com/collections/motor-kits/products/complete-bafang-1000w-bbshd-mid-drive-ebike-motor-kit-battery
regarding the battery there is not much information and specifications. I'm struggling with the idea of how much is 1 amp. I know there are formulas and stuff like that, but I don't know how that translate to real life.
Well, I don't think that the "amp" you are referring to is the same as what the batteries you list have for specifications in your post. Those show Ah, which is amp-hours, which is a measure of capacity. A plain amp, or A, is a measure of current, or how much electricity is flowing at any particular instant. They look similar, but are very different things in relation to ebike part specifications.
For a rough idea of what Ah means practically, it may take 0.5 to 1Ah per mile for 15-20mph riding, depending on riding conditions, weather, terrain, riding style, and ebike system used. So that 11.6Ah could, under the right conditions, potentially give you 20 miles of motor-only range. If you also pedal, and/or use the motor a lot less, then could be a lot more than that. If you use only the motor and ride it hard and fast, you might get 10 miles or less.
Batteries have other important specifications like Amps (continous, and max/peak) that they can provide. If the motor takes more A to work than the battery can provide (say, 10A battery and 30A controller/motor), the battery may (if designed to) shutdown and turn off to protect itself, or if it cannot do so, it can be overheated and damaged, or at best just sag a lot in voltage while under that load, reducing speed and performance. If the battery has more ability to provide A than the motor needs, (say, 30A battery and 10A controller/motor), then the battery has an easy time of it and performs well and lasts longer.
For example, what is a better choice. A 48V 20.3Ah or a 52V 11.6Ah for $274? I also don't have a clue what the 2900 means. Apparently, the kit comes with a free 48v 11.6Ah. Is that too weak? I'm not trying to break a record, but I want something somehow fun to ride.
Fun is too subjective to truly help you decide on.
If you define specifics of what "fun" means to you in numbers, like speed, range, riding style, and on what terrain and weather conditions, etc., and possible total bike+rider weight (which changes performance on hills and at startups), it is a little easier to do.
If it comes with a free battery, try it out with that. If it doesn't do what you want, *then* start worrying about what to replace it with.
If you provide a link to each specific battery you wish us to compare for you, we can do that. Otherwise we can't tell you which of them is better, except for some general guidelines.
A 52v battery is "14s", so it has one more cell group in series than a 48v "13s" battery, and so has a little more total Wh capacity if they are otherwise identical.
It also creates a slightly higher top speed of a motor, compared to the identical 48v battery, assuming the controller doesn't limit this already. That may not translate into higher bike speed, depending on your riding conditions, gearing, etc.
If a specific battery is lower priced compared to another one that is the same voltage and Ah (or very similar), especially by a lot, it's probably not as good a battery. You'd need details on each one to compare them. Without those details, you can generally assume it will not be as good or perform as well or last as long as the more expensive one. It may or may not be true; no way to know without side-by-side testing of both.
One sign of sellers to avoid is when you find conflicting info on a product page. The more conflicting items, the more I'd want to avoid them. It means they either change specs frequently enough to not catch all changes, or that they don't care enough to provide accurate info, or they copy/paste other sale pages (theirs or other people's) and edit them (poorly) to use them for their product, or even that they just make up info as needed to make thing sell faster.
Good or bad reviews may or may not be definitive; that's a judgement call based on the seller and the reviews that you have to make.
A sign of sellers to buy from and stick with is accurate and complete info, prices that aren't "too good to be true", reviews both on their sale page and elsewhere on the internet, especially for people that have had problems with their pack, so you can tell how good their customer service and warranty actually are.
There are quite a few things to know about a battery before you can directly compare it to another, and the cheaper the pack the less likely this info will be provided (or it may be made up):
V
A (max/peak)
A (continous)
Ah
Cell type
Cell brand and model
Number of series and parallel cells (14s8p, etc).
BMS type (balancing, non balancing, etc)
(I've forgotten something but can't remember what
)
Other info that's useful but rarely provided:
combined or separate charge and discharge ports
pack construction type (spotwelded, busbars, soldered, "weldless", etc.; cell holders or loose held only by welds/etc.)
water resistance level (IP67, potted, sealed, etc).
Pack weight, which can loosely be used to validate the actual number of cells/etc. (around 48g/cell, so if there's 100 cells, that would be 4.8kg, so a pack that weighs 5-6kg would be reasonable for that, etc...but a pack that only weighs 3kg can't possibly be real if it's supposed to have 100 18650 cells).