Thudersky Real World Experience
Posted: Fri Jun 08, 2007 4:28 am
It's been a while since I posted an update on the older TS 200ah cells, but with the recent discussion on the list, here is what my real world EV experience over 20,000 miles tells me.
1) I bought 30x200ah TS cells in August 2003 (Nearly four years ago)
2) I use them in my pure EV van at www.solarvan.co.uk
3) Initially I used all 30 cells in a 108v DC drive setup.
4) 2 years ago I changed to a 28 cell 96v AC regen drive. (I have two spare cells now)
5) The cells have worked absolutely fine over this time.
6) They are rugged and easy to link together (unlike Kokam), and do not require a complicated BMS. I use Cedric Lynch's simple cell protectors, and a Zivan NG3 IUa charger.
http://agnimotors.com/home/index.php?op ... &Itemid=39
7) They do not burst into flame or explode at the drop of a hat, a switch fault a while ago meant my cell protectors became disconnected during a charge cycle, the zivan charger just completed it's normal cycle and switched itself off with no harm done. (It was adjusted initially to provide about the right pack end voltage though)
They are ageing of course, and this manifests itself as higher internal resistance rather than reduced capacity. This means it is more difficult to charge or discharge them quickly, as the voltage rises too high or drops too low at high currents, and they heat up more quickly.
9) They do not like cold weather, and need to be at a minimum 20C+ to work effectively now. 25C-35C is better. (I keep them in a heated insulated box)
10) The voltage sag under load is increasing as they age, especially at low temp. A fully charged cell at 20C will still supply 300A+ but the voltage will drop from 4.2v to <2.5v under load. I try to keep to <200A max discharge current. When warm at 30C+ voltage sag is much less.
11) When regen is operating, partly charged cells will still accept charge currents of upto 100A, so long as the cell temp is at least 25C.
12) The limiting factor in their life in my vehicle will be the internal resistance build up to the point they cannot deliver the currents required without damage/overheating. I estimate at the current resistance increase rate they may last another 3 years in my EV application. This gives me a useful life of 7 years. Range is not my limiting factor as my work commute is 26 miles a day total.
13) They may well still be ok as a standby power pack, or ev charge dump pack when EV life is over. I certainly won't be skiping them anytime soon.
14) Would I buy them again? Yes, and I would never go back to lead again. Once you have been spoilt by Li-Ion range/capacity you just can't put up with anything less.
In conclusion I would buy TS cells again tommorrow, I recommend 200ah cells as the mimimum size for most systems, the newer TS 200ah cells are 1.5x heavier than the ones I bought, and I understand have lower internal resistance, and can deliver higher currents. Technology marches on, and I expect their performance will continue to improve. You could wait forever for the EV battery holy grail, and be dead before it arrives, I and the other early adopters of these TS cells took a big gamble. For me it paid off and I have been very happy with them. Good luck.
Peter
1) I bought 30x200ah TS cells in August 2003 (Nearly four years ago)
2) I use them in my pure EV van at www.solarvan.co.uk
3) Initially I used all 30 cells in a 108v DC drive setup.
4) 2 years ago I changed to a 28 cell 96v AC regen drive. (I have two spare cells now)
5) The cells have worked absolutely fine over this time.
6) They are rugged and easy to link together (unlike Kokam), and do not require a complicated BMS. I use Cedric Lynch's simple cell protectors, and a Zivan NG3 IUa charger.
http://agnimotors.com/home/index.php?op ... &Itemid=39
7) They do not burst into flame or explode at the drop of a hat, a switch fault a while ago meant my cell protectors became disconnected during a charge cycle, the zivan charger just completed it's normal cycle and switched itself off with no harm done. (It was adjusted initially to provide about the right pack end voltage though)
They are ageing of course, and this manifests itself as higher internal resistance rather than reduced capacity. This means it is more difficult to charge or discharge them quickly, as the voltage rises too high or drops too low at high currents, and they heat up more quickly.
9) They do not like cold weather, and need to be at a minimum 20C+ to work effectively now. 25C-35C is better. (I keep them in a heated insulated box)
10) The voltage sag under load is increasing as they age, especially at low temp. A fully charged cell at 20C will still supply 300A+ but the voltage will drop from 4.2v to <2.5v under load. I try to keep to <200A max discharge current. When warm at 30C+ voltage sag is much less.
11) When regen is operating, partly charged cells will still accept charge currents of upto 100A, so long as the cell temp is at least 25C.
12) The limiting factor in their life in my vehicle will be the internal resistance build up to the point they cannot deliver the currents required without damage/overheating. I estimate at the current resistance increase rate they may last another 3 years in my EV application. This gives me a useful life of 7 years. Range is not my limiting factor as my work commute is 26 miles a day total.
13) They may well still be ok as a standby power pack, or ev charge dump pack when EV life is over. I certainly won't be skiping them anytime soon.
14) Would I buy them again? Yes, and I would never go back to lead again. Once you have been spoilt by Li-Ion range/capacity you just can't put up with anything less.
In conclusion I would buy TS cells again tommorrow, I recommend 200ah cells as the mimimum size for most systems, the newer TS 200ah cells are 1.5x heavier than the ones I bought, and I understand have lower internal resistance, and can deliver higher currents. Technology marches on, and I expect their performance will continue to improve. You could wait forever for the EV battery holy grail, and be dead before it arrives, I and the other early adopters of these TS cells took a big gamble. For me it paid off and I have been very happy with them. Good luck.
Peter