Willie, It has been my experience that if a bicycle (or laptop) pack is bad, it usually is just a single cell that has gone south. On EndlessSphere you see people bypass cells that have blown up and run an original 5s pack as 4s with original spec capacity, some go to the effort of figuring out why it happened, whether it can be repaired by either charging the one cell separately (which I did) or even replacing that one cell (from a similar pack)
I have seen amazing things from relatively cheap bicycle batteries, including balancing (at very low current) and even overcurrent protection (low resistance MOSFET switch on the pack output that opens when too much current is drawn) which has saved the pack on my wife's eBike several times (crappy controller kept blowing up and shorting itself) BUT I do not see a good protection against over-charging on that BMS, as far as I can see the top voltage of the pack and charger are matched, so that when all but one cell are shunting (balancing) then the last cell coming close to its terminal voltage will also mean it reached the charger's output voltage (the charger being essentially a power supply with current limit). That is not so much a problem with the 24V systems where there are typically 6s but the higher you get, the bigger the chance a cell does not charge fully. But this has been my observation on a particular eBike pack - your pack might be completely different again and soon I will have another datapoint from repairing some stage lighting that is battery powered, where a pack is failing (quitting after 2 hours instead of running 6 hours). That looks to be using laptop cells, so I guess I will find re-packaged laptop solutions. Note that a laptop is typically charged with a much higher voltage than the cell's end voltage so that may be another approach. Success, Cor van de Water Chief Scientist Proxim Wireless Corporation http://www.proxim.com Email: [email protected] Private: http://www.cvandewater.info Skype: cor_van_de_water XoIP: +31877841130 Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203 -----Original Message----- From: EV on behalf of Willie2 via EV Sent: Wed 6/17/2015 6:17 AM To: Electric Vehicle Discussion List Subject: Re: [EVDL] Bicycle battery On 06/15/2015 11:12 AM, Willie2 wrote: > A battery for my Prodeco bicycle turned up dead. The OEM replacement > is nearly $500. Can someone point me toward a better solution? 36v, > ~10ah. Has anyone heard of anyone doing cell replacements? Thanks for the responses! Cors' was especially valuable. I had hoped to be pointed to some battery repair service such as exists for hybrid batteries. The guy working on the bike reported that all cells were bad. I didn't believe him and talked him into opening the case. He wasn't able to get access to all cells without tearing the case up but the two he did get access to seemed good. I have a battery that looks to be a direct replacement coming from China. I don't want to fool with a battery that does not conform to the form factor of the original battery. Hijacking my own thread: In looking for bike batteries, it occurred to me that a bunch of them might make a suitable golf cart battery. My golf carts, with 100ah LFP cells and miniBMS have been FAR too costly to maintain. I've been toying with "lead replacement" batteries that protect themselves from over charging and over discharging. So, several of those might work in a golf cart and not give me the repair/maintenance headache I have now. I wonder if the bike batteries also protect themselves? The "lead replacements" cost around $4/ah/cell while the bike batteries can go as low as about $1.50/ah/cell. I sometimes use 100 amps (@~36v) in a golf cart but I believe I can get by on 80 amps. Assuming a bike battery will do 1C, four 36v 20ah batteries might serve me. I might start with two just to see what trouble I encounter before I spend too much money. IF the bike batteries protect themselves from over charging, I could charge with regular golf cart chargers. Else, I could charge with one or several bike chargers. _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA) -------------- next part -------------- A non-text attachment was scrubbed... Name: not available Type: application/ms-tnef Size: 4919 bytes Desc: not available URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20150617/9f7c342c/attachment.bin> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
