Can a variable DC power supply charge Thundersky LIFEPO4 battery packs on an electric scooter?
We made some observations on a large electric scooter with 16 cells of Thundersky 40AH in 3 packs with a BMS.
All the voltages mentioned will be the average cell reading, i.e. Total Voltage divided by the 16 cells mentioned.
3.333 V - Scooter is at rest 48 hours or more after a full charge
3.22 V - Scooter voltage, stopped, after running 1/2 of its normal 50 KM range
3.17 V - Scooter voltage, stopped, after showing some minor performance slowdown and voltage sags on the "energy meter" (fuel guage)
3.1 V - Scooter really slow (only walking speed) perhaps due to BMS or controller limiting features to prevent damage to Thundersky batteries.
When using a digital variable DC power supply (0 to 72V, 0-1.5A) to charge a 75% discharged scooter, the Thundersky LIFEPO4 cells:
.. rises to 3.33V in an hour (as shown on the power supply display), obviously not charged much.
.. rises slowly to 3.7V, but voltage rise imho is rising faster than my own estimation for a correct State of Charge.
What is your own experience with using a variable power supply on LIFEPO4 prismatic cells, like Thundersky batteries?
The preferred charging algorithm for LiFePO4 is - CVCC - constant voltage until a cutoff point, then constant current. Your variac won't do this properly.
Also - by showing us average voltage you haven't shown us that the voltage of each cell in the pack is balanced. You haven't shown us that your system guards against over charging or over discharging (both of which can kill cells). And what if your pack is imbalanced, you do a discharge that shows a safe total voltage, but one cell is weaker than the others and goes below the low voltage cutoff? That cell will be damaged.
- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
Shouldn´t it be CC-CV?
The voltage raises automaticly to a preset value, then the charger lowers the current.
Maybe - I wasn't sure though, and yahoogled "cvcc lifepo4" and found several pages such as on endless-sphere using those two phrases. In any case the thing I wanted to imply is that proper lifepo4 chargers aren't all that expensive and will do a more correct job than simply dialing in a voltage on a variac.
- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
a charger *is* an adjustable DC power supply.
most follow constant current, then constant voltage.
some have a constant current phase after that to allow the BMS to do balancing (though I would only do that on the first charge).
Its rather more important to have a BMS than a smart charger.
what specific scooter is this?
Matt
Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km
a charger *is* an adjustable DC power supply.
most follow constant current, then constant voltage.
some have a constant current phase after that to allow the BMS to do balancing (though I would only do that on the first charge).
Its rather more important to have a BMS than a smart charger.
what specific scooter is this?
Matt
Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km
The scooter is a Electric Motor Sport (makers of the GPR-S) Native Z6 with Lithium (not the SLA model).
ahh,
its good to talk to an owner of an EMS bike.
I Don't know what charger or BMS they use, but a few pictures will point in the right direction.
Its not likely they would have made their own due to lack of scale of manufacture (though not impossible).
Matt
Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km
Hi,
I am also need the answer of this question.
Hi
do you also own a Z6?
have a look at the other thread.
post more pictures if you can :)
Matt
Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km