Hello, I touch you on this board because I has a xm3500li sold by mounten Chen.
Indeed, in 3 months I will change my li xm3500 with a new engine from 6kW kelly. I owns my xm 40 cells 40Ah LFP in packs of 2 or 60 volts 40Ah. 60 volts 80Ah
I will soon hook up to 40 cells in series to give me 120 volts 40Ah. My concern is as follows:
The new engine operates at kelly 72 volts and 90 volts maximum. The controller also!
I am afraid of burning the motor and controller in 120 volts?
I think a converter add to 120 volts for 90 volts but I do not know the net!
Please could you help me?
Laurent
20 LiFePO4 cells is really about 75 volts maximum, so 40 cells in series would be about 150 volts max.
26 cells would be about 90 volts.
Might be best to buy 12 more 40 Ah cells and have 26 x 2 for 80 Ah at 90v max?
Cheers, Gary
XM-5000Li, wired for cell voltage measuring and logging.
Huh?? 20 * 3.2v = 64 volt nominal 26*3.2=83.2 volt nominal
- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
Nominal 3.0 or 3.2 yes, but the Maximum voltage applied to a controller would be over 3.6 or 3.7 volts per cell.
Cheers, Gary
XM-5000Li, wired for cell voltage measuring and logging.
a kelly 72v motor will run fine on 120v (actually it will run much better than fine).
a kelly 72v controller will be destroyed by 120v.
if you want to use 40 cells, use the 144v controller. it has a max voltage of 180v, which allows up to 50 cells.
alternatively, you can use the 120v controller. it has max voltage of 136v, which allows up to 38 cells.
top speed will be massively improved by going to 120v.
Matt
Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km
at 1C load, at cooler temperatures, the TS actual voltage is 3vpc.
an AGM battery of the same (electrical) size is 12v.
therefore, it is convention to replace every 12v block with 4 cells to maintain original voltage under load.
so 20 cells is only "60v"
Matt
Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km
Laurent, How are you going to fit all the cells in the xm3500li. I'm running 28 now. I have thought about eventually doing something like what you said. I'm interested in how your going to fit the batteries.
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
But unfortunately at rest after a recharge the controller will see 20 * 3.7 = 74V. Thus, all three numbers presented here are important:
3.2V is the nominal voltage and is the best to use when calculating pack capacity (cell count * 3.2V * cell capacity * 80% = "usable energy").
3V under load is the best to use when figuring out on-road performance (cell count * 3V * Volts per RPM for your motor will help determine top speed)
3.7V is best to use when looking at controllers (cell count * 3.7V must be less than controller max voltage - otherwise the controller will simply refuse to operate).
Hope this helps.
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.
John is correct.
most "48v" controllers use 75v gates on the power stage.
so a 20 cell pack is the absolute maximum of what should be used with these controllers.
i personally only charge to 3.6v, but this has more to do with your BMS than the actual cells. anything above 3.4v on a LFP cell is fully charged.
as far as working out rpm under load for your motor, you want to use rpm/V (if using V/rpm, you need to divide)
Matt
Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km
Ooops! Sorry about that.
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.