Charging A123 M1 Cells? - RC-Monster Forums

jhautz · **Charging A123 M1 Cells? -** 10.23.2006, 06:08 PM

How is everone charging the A123 cells? Is the A123 charger capable of charging 6s packs of the M1 cells? I was wondering if its possible to charge them using a standard lipo charger or do you have to use the A123 charger.

MetalMan · 10.23.2006, 06:21 PM

SLK Electronics offers the LiPoDapter that allows you to charge up to 10 A123 cells with a NiMh charger:
http://slkelectronics.com/lipodapter/index.htm
I believe starscream has one.

starscream · 01:50 AM

The A123 Sonic charger can only charge up to 3S so you will have to use another method if you want to make a 6S pack. I currently use a 4S pack and 2S pack in series.
The M1 cells should be charged with the cccv method. A Lipo charger will work but you will have to manually monitor the voltage and pull the packs off before they reach 3.6 volts per cell. The LipoDapter allows you to charge up to 8AMPS and cuts the charge off at 95% capacity for the M1's and 85-90% for Lipo's. I got my M1 packs and LipoDapter from Pete at www.modelelectronicscorp.com

jhautz · 10.24.2006, 02:40 AM

so really it just needs a lipo charger that has a 3.7v cut off on the charge vs the 4.2 a lipo would use.

Are there any lipo chargers that have an adjustable cut off voltage? That lipodapter seems really confusing.

starscream · 03:47 AM

Quote:

Originally Posted by jhautz

so really it just needs a lipo charger that has a 3.7v cut off on the charge vs the 4.2 a lipo would use.

Are there any lipo chargers that have an adjustable cut off voltage? That lipodapter seems really confusing.

The cutoff voltage for M1's isn't 3.7 its 3.6 volts per cell. The LipoDapter is really easy to use and has automatically cutoff at 95% capacity every time I've used it. The Xtrema is an example of a charger that has the capability to charge Lipo's and M1 cells. It runs around $190. I already have a NiMh charger that I can charge up to 7.5 AMPS so I went with the LipoDapter. There really isn't anything fancy about the LipoDapter, its straight forward and easy to use.

squeeforever · 10.24.2006, 04:34 PM

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.

BrianG · 10.24.2006, 05:02 PM

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?

jhautz · 10.24.2006, 05:24 PM

from my understnding that is exactly how the lipodapter works. It just skips the constant voltage stage and only charges them to 90%.

Its a simple device. Its just having to understand what the number of blinks mean and pressing the same button the correct number of times at the right times in a startup sequnce every time you charge a battery with no feedback from the device as to if you did it correctly sounds like a mistake waiting to happen to me.

If sure it works fine if your carful.

MetalMan · 10.24.2006, 06:11 PM

Quote:

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.

Quote:

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.

squeeforever · 10.24.2006, 07:54 PM

I was suppose to get an Xtrema as a beta tester or at least at a large discount and they never sent me an e-mail when they came out....

BrianG · 07:58 PM

OK, thanks. It makes sense now. The cutoff is easily done with the FET, I just couldn't understand how it would do the CV stage.

You think that the CV stage is good for only 10% of the charge? When the pack reaches 4.2v, the current is still at the full charge current, but then slowly falls. I would think that's at least 15-20% of the charge. For instance, with my 2s2p emoli, I get about 4500-4800mAh when it hits the CV stage and I end up with a total of ~5800mAh put into the cell. That's at least 17% of the charge missing if I were to pull the pack off at that point. Unless emolis act different than M1's or Lipos?

Even if it was only 10% due to the lack of the CV stage, that's 10% less pack capacity. I don't know if I'd like that. I understand the cost factor, but the price of these packs, sometimes it's worth getting the "good stuff".

starscream · 10.24.2006, 09:42 PM

The "Dapter" cuts the connection to the charger when the cuttoff voltage is reached. Yes, you have to manually count the number of blinks per cell. I don't find it hard to count to 6 though :005:
Counting blinks beats the $200 price tag for the Xtrema, especially when I have never used the cells before. If I invest more into the M1's, I'll reconsider the Xtrema.
My multimeter typically shows my 6S pack at 20v when the "Dapter" cuts the charge. Thats 92.5% capcity in 16 minutes at 7.5 AMPS. I can live with that for now. I sent my Xtrema back because I couldn't justify keeping it when the $40 LipoDapter charges my packs just fine.

jhautz · 10.25.2006, 01:41 AM

Yea but in the instructions I found on line they not only talk about counting the blinks for the cell count, but also when the red light blinks 3 times then you push the button and hold it until it blinks again and then when the green light blinks 3 times you push it again and then you are in M1 mode or something goofy like that. Then how are you sure that you are in M1 mode???? I'm sure that you probably get used to it since you have to go through the whole routine of putting it into M1 mode every time you hook up a battery.

I'm sure it is actually much simpler than the instructions make it sound. All I'm saying is there is more to it than counting the cell count blinks. And from what I read there seems to be a pretty good chance for error.

Maybe I'm just paranoid from Lipos:p.

starscream · 10.25.2006, 02:29 AM

Quote:

Originally Posted by jhautz

Yea but in the instructions I found on line they not only talk about counting the blinks for the cell count, but also when the red light blinks 3 times then you push the button and hold it until it blinks again and then when the green light blinks 3 times you push it again and then you are in M1 mode or something goofy like that. Then how are you sure that you are in M1 mode???? I'm sure that you probably get used to it since you have to go through the whole routine of putting it into M1 mode every time you hook up a battery.

I'm sure it is actually much simpler than the instructions make it sound. All I'm saying is there is more to it than counting the cell count blinks. And from what I read there seems to be a pretty good chance for error.

Maybe I'm just paranoid from Lipos:p.

I see what you mean about the process but after doing it a couple times, its easy. I also understand about being paranoid from charging Lipos :eek:
Thats why I like these cells so much, they can take a lot more abuse than Lipo cells. I have only done a few charge cycles on these cells but there haven't been any errors thus far. The only thing I noticed is that the "Dapter" only see's 5 cells after I use the pack so I have to increment 1 cell every time I charge. I am also hearing that these cells tend to not accept a charge once they have peaked. I'm not sure how that would work out if you left them on the charger for an extrended period of time but gives credence to thier durable nature.