Charging A123 M1 Cells?

[MetalMan]

Originally Posted by squeeforever

Is 3.6 the nominal, like 3.7 would be for a LiPo cell? My E-Station 701 is capable of charging 3.6 or 3.7 volt cells. 3.7 being the nominal for LiPo like 1.2 being the nominal for NiMH.

The nominal voltage on A123 cells is 3.3v. 3.6v is the max. voltage. The 3.6v setting on your charger is for the nominal voltage of older Li-Ion cells, where the max. charge voltage would be 4.1v.

Originally Posted by BrianG

I'm curious to know how the Lipoadaptor works.

A traditional lipo charger charges at a constant current until the cells reach 4.20v per cell. Then the charger switches to contant-voltage mode and charges at a steady 4.20v until the charge current dwindles down to ~0.1A.

A typical peak detection charger is simply a contant-current charger. The output voltage simply goes as high as needed to push the desired charge current through the batteries. Another circuit monitors (but does not limit) the pack voltage until it starts to drop. Then the charger stops.

Since the lipo adaptor hooks to a peak-detection charger, does that mean it never charges in constant voltage mode? If not, then wouldn't the M1 cell(s) not get the full charge due to the missing CV stage? If it does, how does THAT work?? Once the lipo adaptor hits 3.6v, it would lock the voltage. Then the battery should start drawing less current just like lipos. But since the constant current charger is still trying to force the charging current through it, the voltage will go higher and higher and higher until it hits the limit. This extra voltage and current (don't forget, Li cell current should be dropping here) has to go somewhere since it's not going to the battery. And the lipoadaptor doesn't look near big enough to shed that kind of energy.

I know it must work, I'm just confused how it works. And if it does NOT charge the constant-voltage portion, then the cells aren't getting charged to the full capacity. Or are the M1 cells different from other Li technology and not need the CV stage?

The Lipodapter cuts off when the pack reaches 3.6v/cell. In a picture it looked like there was a FET, so it is very likely that this FET is used to disconnect the battery from the charger when it reaches the right voltage. Because of this, the Lipodapter can't go into a CV mode. But the cells should be about 90% charged by the time they reach 3.6v, where the actual percentage depends on the charge current used.

One thing you could do is a manual CV phase. But you need a charger that will allow you to adjust the charge current during charging (the Duratrax ICE can do this). As the voltage nears 3.6v/cell, you decrease the charge current. When the voltage nears 3.6v/cell again, decrease the charge current some more. This process would take longer than an actual CV phase, but not all of us can afford the $190 TME XTrema charger :mad:1.