Just to say that the current that the 2500w 60v mopeds put through a 41 amp current. This seems to destroy normal batteries very quickly. I have had 3 sets, the originals, cheap batteries, and a gel pack from Haze. The last two packs lasted about 150 cycles only before dying. Could this possibly be the controller? Should I get a new controller?
Anyway I currently believe they simply are not designed to handle that kind of current. I have now ordered some Lithium batteries from ebay V power.
Do you know the discharge capacity of these lithium batteries? you need 40 amps continous.
I have been assured it is 40 amps; however there may be problems as I simply believe that no one goes to the trouble of doing thorough tests at this unusually high amperage.
can you link to the specific battery you have or are trying to buy?
in EV land, 40A is rather small.
i used TS LiFePO4 40Ah cells at 55A continuous for 18months, cells were still 70% of original capacity after 500 cycles of 18'000km.
the rest of the bike was at end of service life though.
Matt
Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km
Hello Matt
Yes the ebay store is here:
http://stores.ebay.com/vpowerhk
I chose ebay as there is the chance of some possibility of rebate / resolution should problems arise.
The figure I hear most often for lithiums is about a 1000 cycles whilst retaining 80% of capacity.
Hope this clarifies things.
Piers uk
the 1000cycles to 80% rating is true when you keep discharge rate low.
higher discharge rates reduce service life.
my cells for instance were rated for 0.3C (~15A) to get the 2000 cycles to 80%
at 1C, 1000 cycles is probable
at my 1.4C, 500 cycles is what i got
at 3C, a guy over in the states got about 100 cycles
to get the reliable discharge rate you need with these low rate cells, you will need lotsa them.
minimum 40Ah.
you can discharge much faster for brief accelerations without reduced service life.
the ratings for 0.3C 2000 cycles rated cells are like 3C for 20sec and 10C for 0.02 sec to retain the 2000 cycle service life.
Matt
Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km
Hi Matt,
Yes I'm going for a 40ah pack at 41 amp for 60v. Hopefully all will be well. They cost $1200 delivered with BMS and chargers. So I reckon it's about the best I can do AT THIS DATE AND TIME! I'm shouting because prices are bound to plummet. There are cells out there designed for much higher discharge rates. http://www.forsenusa.com/batteries.html shows a good range.
Another positive aspect is that I can make up my own pack when they are dead in a few years just by bulk buying a few dozen cells, this will be extremely cost effective - prices are going to go down and cells alone are much cheaper.
When you have ridden an electric bike its hard to go back to petrol - what are your plans?
Piers
Just to say the lithium vpower batteries from ebay work really well. The weight reduction is really noticeable over Lead Acid and gives a much greater performance, the range also has doubled. I found out that the ah rating for Lead Acid is completely wrong for high 40 amp discharge rates - 40ah represents a low discharge rate and can be as low as 25% of this for high rates. Also causes them to fail much quicker. The chargers for 60v are not great from vpower as they keep running after full charge has been reached so I have bought a timer switch - it's a bit of a hassle but I can live with it. Also I think the 60v lithium pack actually pushes out far more than 60v when fully charged and this has causes a problem with the electronics.
If you put a volt meter on your pack you will find at least 75V immediately after disconnect from charging. What is the output of your charger? My 20 X 40Ah TS charger is rated at 72V but HVC is close to 76.5V. Individual cells are all 3.65-3.75 an hour after charge. NO BMS.
I haven't got around to measuring the output voltage, but the charger is rated for 220v to 240, I run it at 240v so I was thinking of putting in a power supply transformer to reduce it by 10% - 15%, but not quite sure whether this will reduce the output voltage, but guess it will. It's just that last little bit that seems to mess up the drive system electronics, unfortunately the problem persists even when I have ridden for a bit as the batteries warm. I have a bms and when the batteries are charged it puts the power into something called Shunts - which heat up the BMS like a small oven. Wish I was taught all this stuff at school!!! I feel like a cave man staring at the sun.
The output voltage is always regulated.
putting a transformer in between the charger and the mains will have no effect upon output voltage.
what do you mean by the higher voltage mucks up the system?
Matt
Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km
Hi There is a generic problem with the erato (emax) 2500 w bike I ride which stutters occasionally after charging. The weird solution is to turn off the ignition and wheel it forward a couple of inches, before restarting. Since installing lithium this problem has become more accentuated with stuttering starts and low power for quite a while, until sufficient power has been drained from the pack. Unfortunately the warmth which comes from using the pack also raises the output, consequently if I try and ride directly after recharging, on a warm day, I not only get very low speed, but it can also trigger the trip switch. Hey ho, when I undercharge slightly it's a speedy, fun ride. A timer switch for the charger seems to be the only solution?
Piers