How do you charge C/D batteries in the Maha C9000? 20,000mAh

[Zero_Enigma]

DoI've heard the C9000 can charge as high as 20,000mAh batteries. Now the question is how do you charge the C/D batteries when the charger is for AA/AAA??

I know Maha makes D cells with 11,000mAh which would make good power packs for my night biking.

 

[TorchBoy]

Lots of MH-C9000 users are waiting for an adaptor that will plug in to an AA slot in the charger that will allow a D cell to be charged externally. There are only home made products at present, and not too many of those.

 

[SilverFox]

Hello Zero Enigma,

You will have to find one of the original C-9000 units to do that. The original units had a safety timer that shut off at 20000 mAh, but the "improved" units shut down at 4000 mAh.

The exception is the "Break-In" function. If you can figure out a way to hook up a C or D cell to the C-9000, you can use the Break-In function to form the cell.

Tom

 

[Zero_Enigma]

SilverFox,

Then why the flip would they say the charger can charge up to 20,000mAh when they cut off at 4000mAh now. I bought my charger (firmware 0G01A) and got my charger last weekend thinking Ican charge up to 20,000mAh if I had some adaptor or somewhat to charge the 11,000mAh cells so I can charge those D cells for my bike for night riding.

I am cheezed off right now after reading what you wrote.

 

[Mr Happy]

I remember reading it was 20,000 mAh, and this is the first time I've heard mention of 4000.

More likely though is the difficulty of finding a set of D-to-AA adapters. I imagine you'd have to rig up something yourself for the purpose.

 

[SilverFox]

Hello Zero Enigma,

Let me see if I understand...

You pick up some 11000 mAh D cells, then purchase a AAA and AA charger hoping to modify it to charge them. Now you are upset because the modification is a little more involved.

Is this correct?

Did you happen to notice that Maha also offers the 808M? It also charges AAA and AA cells, but also charges C and D cells. No modification necessary.

If I am sounding like a smart alack, that is my intention. I apologize if it offends you in any way. I would hope that you and others would search through the C-9000 threads to understand how it works. We have put that charger through a microscope, several times.

Getting back to your question...

The C-9000 has a safety timer set to 20000 mAh on the break in mode. If you can come up with a way to connect a larger cell to the charger, you can select the "Break-In" mode and go with that. The highest value you can select is 9900 mAh, so your charge rate will be roughly 1 amp. Your cells will get 1 amp for 16 hours, so I guess we are still at little bit short on the 20000 mAh claim.

With normal charging, you will need to reset the charger a couple of times in order to get a full charge. If the cell has been completely discharged, you would have to restart the charge an additional 2 times to get a complete charge. The C-9000 will shut off after around 4000 mAh. You restart the charger and pump an additional 4000 mAh in, and now you are up to around 8000 mAh. One more restart should bring you up to a full charge. During this normal charging, you can select a charging current of 2 amps, so the charging time will be around 6 hours.

On the other hand, the 808M also charges at 2 amps, accommodates C and D cells, and you don't have to restart the charger.

As I mentioned earlier, if you can find a 0F C-9000, it has the safety timer set to 20000 mAh during normal charging. It also has "issues" with missed terminations, and the result of a missed termination could be "cooked" cells because of the extended timer. The "improved" C-9000 addressed these issues by making the charge termination algorithm a little more conservative and adjusting the safety timer.

I hope this helps you understand that the C-9000 is probably not the best charger for D cells. It can be done, but it takes some extra effort and you have to come up with a way to hook your cells up to it. By the way, if you decide to go this route, pay attention to your cell holders. Some of them are not capable of handling 2 amps.

Tom

 

[rizky_p]

as i recalled only the first firmware which has 20000mah charging caps while the newer firmware is far lower than that.

I use magnets and aligator clip to charge any battery sizes even C and D just make sure the cable is big enough that the internal resistance test doesnt go crazy and reject the cells.

 

[GaryF]

Also don't forget that you are defeating the charger's ability to detect the battery's temperature - part of it's thermal protection - by rigging a way to charge cells externally. It may well never be a problem, but at least be aware of the risk you are taking when you do this.

 

[rizky_p]

Also don't forget that you are defeating the charger's ability to detect the battery's temperature - part of it's thermal protection - by rigging a way to charge cells externally. It may well never be a problem, but at least be aware of the risk you are taking when you do this.

yes i am aware of that, at the moment i think its the only way. I am an R/C player(electric helis) charging various type of batteries almost part of my life, as long as you know what you are doing then it is ok but if you think it is dangerous then dont do it.

 

[TorchBoy]

Just a point to bear in mind - whether you think you know what you are doing isn't going to stop something going wrong and causing a cell to overheat unexpectedly, which you might not catch even if you were watching it. Your call on whether that's worth it.

 

[Darkpower]

Also don't forget that you are defeating the charger's ability to detect the battery's temperature - part of it's thermal protection - by rigging a way to charge cells externally. It may well never be a problem, but at least be aware of the risk you are taking when you do this.

Precisely. NiMh have a rapid temperature rise at the end of the charge cycle that corresponds to the -Delta/voltage change that signifies the end of charge. Some fast chargers monitor temperature to make sure they don't fry the batteries during a high current charge cycle while others also to determine end of charge by temperature rise rather then by a small change in voltage.

 

[rizky_p]

Just a point to bear in mind - whether you think you know what you are doing isn't going to stop something going wrong and causing a cell to overheat unexpectedly, which you might not catch even if you were watching it. Your call on whether that's worth it.

Yeah good point though, you got me on that.

 

[NA8]

Those indoor/outdoor thermometers with the long wire probe for the outdoor temp are handy for monitoring the approx temp of your battery under charge. Get one that has the peak temp/button memory feature. Oregon Scientific had one like that.

 

[TorchBoy]

Hey, I've got one like that. A rubber band to hold the outdoor probe to the D cell, and there you go. I've also got a digital multimeter with a temperature probe. Just one problem... I don't have any NiMH D cells.

 

[rizky_p]

Hey, I've got one like that. A rubber band to hold the outdoor probe to the D cell, and there you go. I've also got a digital multimeter with a temperature probe. Just one problem... I don't have any NiMH D cells.

but that doesnt stop the charger automaticaly when temprature is critical, just a read out.

 

[wptski]

Precisely. NiMh have a rapid temperature rise at the end of the charge cycle that corresponds to the -Delta/voltage change that signifies the end of charge. Some fast chargers monitor temperature to make sure they don't fry the batteries during a high current charge cycle while others also to determine end of charge by temperature rise rather then by a small change in voltage.

The rapid increase intemperature after -deltaV or after it misses it. Besides that, if you read "all" the C9000 threads, you might see some posts where cells melted the wrapper without stopping for high temperature!

EDIT:
I might also add in some of those old C9000 threads are graphs I posted while charging two cells, one inserted in the C9000 and the other connected externally. The externally connected cell ran much cooler. If I remember correctly, it was over 20F cooler!