Starting need some guidance

Badoem

New Member
Region
Europe
Hey
I currently have a 350w 10.4ah bike
I would currently put a parallel connection on it with 2 cheap online batteries Wich I after wrap with (electrical) tape in a saddle bag or search a shock proofish box for it . They must have the same "status", voltage and % charge when connecting at the start, from then on it doesn't seem to matter cause unless the connection is broken what happens to one happens to the other from what I read (maybe some isolation). Each will have a xt60 male connector that I then solder on. Then a switch with females to keep the current battery compatible.
Another controller that can control output and later the motor.


Now that the question is about the cabling and battery compatibility, and rightness of my values and and the possibilitypossiblity suppose I already change the cabling from the motor to 5,26mm² would this extremely limit of my current 10.4 ah over foldable bike distances? And damper the current performance.
I chose 5,26 I think 10 awh cause 750-1000 what's seems what the battery is for

the programmable controller can potential also limit the output of my wrongly bought 30ah 48v maybe?
I I'll get a discharge/charge device which might also act ass a measures USB..
Can I charge the battery via de 2 parrellel charges batteries at the same time?

This also seems removable I'll eventually change the frame and brake for suspension on the back.
 

indianajo

Well-Known Member
ah is not a measure of current. It is a measure of the energy in the battery, the number of amps it will put out for a certain number of hours. There is no standard number of hours the measurement is taken at for ebike batteries. 10 ah is a bike battery of moderate size, approximately 30 to 50 miles range at low speed.
Paralleling batteries is so fraught with problems that when builders parallel more than one stack of cells, they include a bms (battery management system) to prevent damage. The bms also attempts to balance the charge in the different stacks when nearing full charge. The bms connects to each stack individually, and can shut it off with a transistor.
5.26 mm wire is very thick, more suited to starting a 50 horsepower motor than an ebike. ebikes use about 2 mm wire for the main feed.
Wires twisted together do not make a reliable connection. Electrical tape invariably falls off. May as well short the battery out now and get it over with where you can call the fire department conveniently.
Controllers limit the amount of amps they will deliver to the motor. They do not limit the number of amphours available, which correlates to how far you can ride on one charge.
I suggest you study a 2nd year physics course, the electrical year.
Two batteries charged together need a bms large enough for the total number of stacks of cells. The bms will need access to each stack of cells individually.
Your 750-1000 measurement has no unit associated with it. You learn in a physics course to associate a unit with every measurement, so the numbers have a meaning.
To extend range you can put 2 batteries on a double throw switch, to switch from one battery to the other. 30 to 50 amp rated switches are pretty rare, and are rated for 12 v usually in automotive service. Unplugging one XT90 and plugging in the other XT90 is the more usual practice. ALthough I find XT90's fall off in the most inconvenient places, like 27 miles from my maintenance base. Andersn connectors are more secure, as are insulated .250 flag crimp terminals from 3M, Ideal, T&B, Panduit, AMP, or Dorman. The crimp terminals from ***** melt at 30 amps.
 
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JASmith

Member
Region
USA
Just to add that amp hours doesn't really tell you how much capacity the battery has either, and watt hours is more useful for that. I have a small 10AH power brick and a much larger 2AH lawn mower battery, but the big difference is the 10AH brick is at 5V meant to power tablets and mobile phones so 50watt hours and the lawn mower is at 72V so 144watt hours, about three times more capacity. I don't see an issue with wiring same voltage batteries in parallel, and that should reduce the load on each battery. We were considering that option ourselves, with each of our lawn mower batteries having 1500 watt capacity that increases to 3000 watt and 4500 watt as you add more. They have their own internal circuitry and would cutoff if one's battery health was a tick worse than the others, and in parallel the bike should still run even if one were disconnected. When it comes to charging, for lithium on mine I would certainly want to do them separately which is easy as they are cartridge style, but on my UPS I recently had to swap the two lead acid batteries wired in parallel and they charge just fine but that's different chemistry.
 

indianajo

Well-Known Member
Lead acid batteries don't catch fire when charged incorrectly. Lithium Ion batteries can. Charge & use each lithium ion battery separately, unless a BMS manages each parallel stack. Two bms boards on two parallel LiIon batteries does not make a proven charging arrangement. For more experimental data see endlesssphere forum.
I bought battery a big enough to last beyond when my hips get sore. That $630 17.5 ah 48 v battery has been everything I needed for 3 1/2 years. I'd need a better seat to go beyond 30 miles, and I've tried six.
 
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JASmith

Member
Region
USA
Lead acid batteries don't catch fire when charged incorrectly. Lithium Ion batteries can. Charge & use each lithium ion battery separately, unless a BMS manages each parallel stack. Two bms boards on two parallel LiIon batteries does not make a proven charging arrangement.
Sorry that's what I meant, my landscaping batteries include a BMS circuit board inside them, which I believe most battery packs do these days (even my little drone batteries have internal circuitry inside their plastic case) so maybe I wasn't understanding what OP was referencing and was just going to add packs of raw cells? Regarding two BMS boards, I understand this guy has been doing it for years, even on his paraglider and I saw another DIY guy who had I think 8 dewalt handtool batteries hooked up, but of course he charged them separately.