Need help making a Li-ion charger for a 36v/~10Ah eBike battery. - Page 1
Forum section: electronics / projects

author: TECH_GEEK10
author_rank: Contributor
timestamp: March 01, 2015, 05:25:35 am
content: I recently bought a used electric bike from a friend who was selling it because the charger caught fire while a transformer at the local power station was shorted for over a week.I have been looking for a charger for this ebike but all I can find are $100+ chargers unless I buy from china. I have decided I would try to build one from my own set of parts.So I guess what I am asking here is for a super simple schematic that is suitable to charge the bike's battery and that uses as few IC's as possible.Here is what I know about the battery pack:16 Amp hoursUses a total of 10 Li-Ion single cells aranged in series (very large/long rectangular)Built-in BMS (Battery Management System)Internal low voltage cut-off triggered at 36vConstant balancingTemperature sensing?Maybe more?...Keyed power switch (for manually disconnecting power when not in use)Integrated voltage displayHere is a picture of how the pack appears to be assembled:I would design this myself however I am still learning what the components are & what they do...I'm guessing I need a power supply 40.8V DC constant current power supply that shuts off when it senses the battery has a voltage of 40.8Volts?

author: TECH_GEEK10
author_rank: Contributor
timestamp: March 01, 2015, 05:47:14 am
content: Quote from: 3roomlab on March 01, 2015, 05:44:40 amYou are in luck! It actually uses the same plug as the wand on a HAKKO FX-888D.

author: TECH_GEEK10
author_rank: Contributor
timestamp: March 01, 2015, 05:48:52 am
content: I would like to get a bit of experience making it than sourcing a turd from china.

author: SeanB
author_rank: Super Contributor
timestamp: March 01, 2015, 06:30:56 am
content: Is the charger that cooked that you cannot repair it? It likely uses a regular transformer inside, as if it was a SMPS it would not notice the high mains in the US for a long time, at least not till all the electrics in the house have fried.

author: TECH_GEEK10
author_rank: Contributor
timestamp: March 01, 2015, 06:34:55 am
content: Quote from: SeanB on March 01, 2015, 06:30:56 amI have no access to the charger. It fried 2 years ago, and was originally bought in a shop that rebranded everything.www.mncebike.comIt fried because the surge protector next to it caught fire enough to cause the sprinkler system to activate.

author: TECH_GEEK10
author_rank: Contributor
timestamp: March 01, 2015, 06:45:23 am
content: The internals of the pack contain only 4 FETs a handfull of transistors an resistors of many shapes & sizes, a diode or two, and one of these:http://www.digikey.com/product-detail/en/S-1142B33I-E6T1U/728-1062-1-ND/2352755

author: TECH_GEEK10
author_rank: Contributor
timestamp: March 01, 2015, 07:05:55 am
content: Well maybe not 2 years, not sure when to be honest, but it is 40% full at this time and I can get it to power the bike on and run the motor for a solid minute.

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 01, 2015, 04:32:33 pm
content: Assuming it's actually a hybrid and not a pure EV, you can charge it with regeneration. Maybe take it a step further and get a stand to raise the rear wheel so you can use it as a stationary bicycle at home.Probably the easiest would be to get a surplus 48V telecom PSU and tweak down the voltage to 41V or so. Then add a blocking diode and a car light bulb as a current limiter. Or use two surplus laptop PSUs in series.

author: TECH_GEEK10
author_rank: Contributor
timestamp: March 01, 2015, 04:38:36 pm
content: Quote from: NiHaoMike on March 01, 2015, 04:32:33 pmIt has a one way bearing on the drive wheel so no way to charge it using the bike as a dynamo.QuoteHow would I go about that? I have a Verizon psu, and many laptop and atx psu laying around.

author: TECH_GEEK10
author_rank: Contributor
timestamp: March 01, 2015, 06:27:19 pm
content: QuoteI think I can do it that way but how are the bulb and diode wired in relation to the 41v psu?

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 01, 2015, 07:41:45 pm
content: Connect them in series.