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Hi everyone - I have had my XM3500 now for almost a year and a half now, and ride it when I can. I have provided no other method for charging the 20 Thunder Sky batteries except using the factory charger. No BMS was used at all. After a year and a half I first noticed my range dropped off almost by half of that when it was new. When new I could get about 25 miles out of it riding it hard.
Yesterday after a charge I got it out and noticed that after about 5-6 miles that the controller would cut off the current to the motor, until the battery level meter came back up. I also noticed that when crusing normal that the battery level meter ran dangerously close to the low indicator. Remind you, that 5 miles ago the bike was fully charged. I limped the bike in economy mode back to the house and let it sit over night without putting it back on the charger. Today I removed the skirting and took individual battery cell readings.
All the batteries reported approximately 3.30 volts, with some being as higher or lower by .05 volts, which in my book was normal, except for one battery that was ZERO! This cell had completely shorted out. I took a picture of that cell you your visual information. Notice the top of the cell appears damaged, and has a white crusty fluid coming from it. Rest assured, nothing hit it. Guess I'll be ordering a new cell, but I wanted to point out what a failed battery looks like, typically.
After a normal charge cycle I noticed only a .25 voltage increase per battery, except for the dead battery.
I'm wondering now, at what voltage does the controller shut off normal operation?
Thanks for your post Nyemaster.
Please keep us posted as far as how things turn out when the bad battery is replaced. I replaced two dead cells in my GPR-S (60 AH Thunderskies) and it still behaves roughly the same as your bike. But none of the batteries are dead at this point. However, one of the batteries has become very bloated and has been leaking fluid (like your dead one) and though its voltage level looks normal at rest, it appears to have a much steeper discharge curve (as well as charge curve) than the other batteries. My theory is that, at the point where the controller cuts off current to the motor, the leaky battery has discharged to such a lower voltage level than the other batteries that it starts sucking juice out of them. So my voltage will sag down to 55 volts overall, the controller will cut off juice, and then when I stop the bike the overall voltage will quickly rise back up to around 79 (24 batteries). And a typical voltage reading of all the batteries at that point will show every battery at 3.33 volts, except the leaky battery is at 3.25 volts.
Anyway, I am hoping the problem is just that one leaky battery (will replace it as soon as the order comes through), and I am hoping that the single dead battery is your only problem. But again, please keep us posted!
Hi Guity - does your GPR-S have a BMS? Did it have a BMS on day one or was it a retro-fit? Thanks!
John H. Founder of Current Motor Company - opinions on this site belong to me; not to my employer
Remember: " 'lectric for local. diesel for distance" - JTH, Amp Bros || "No Gas.
just a thought .these cell that have bloted / leaked are these cells.
upright ?? or layed on there sides.
as wonder if it would vastley reduce there paformance ??
kev
Hi JDH - The GPR-S didn't come with a BMS, which doesn't bother me as much as it would others. But what killed me was taking out the battery trays and trying to balance the charges of the batteries after placing the new batteries in the pack. My method of discharging cells was to attach a 30-watt bulb to a single cell, and pretty soon I learned the hard way that the best way for me to discharge those things would be to actually run the bike. But as soon as I put the battery trays back in the bike I wouldn't be able to check individual voltage any more. So I ended up attaching wires to the positive terminal of each battery which all lead up to three euro-style terminal strips tucked underneath the fake gas tank. So now using those terminal strips at least I can check individual cell voltages and charge single batteries without removing the battery trays. And with the battery trays in I now have the option of discharging the pack by just driving the bike...That's as about as primitive of a Battery Monitoring System as you could get, I suppose...
Kevin, my cells are all upright. The Thundersky people specify that they are supposed to be used that way. I have read, however, that for something like $10 more per battery, Thundersky will build batteries that are approved as far as laying them down -- apparently they place the vents for these special batteries on a different part of the battery casing.
I have seen pictures of folks who were just laying the normal batteries down flat, and these would usually be accompanied by some tsk-tsking on the part of various forum readers, but I haven't read of any actual examples where usage in this way actually caused problems...
The low voltage cut off for 3500li is 52.5v. I would check to make sure all your connections are tight when you get your new battery.
2008 XM3500li Mods/Kelly KBL12251/84v 28cell 40AH pack/ Variable regen brake trigger on left brake handle/Givi/Cycle Analyst/Homemade BMS
KMX Typhoon Home build (recumbent pedelec) with two Astro Brushless 3220motors/twin castle Phoenix ICEHV 160/ Cycl