Maha MH-C9000 SUPPORT / FAQ - continuation

[stroberaver]

Thanks for the advice - when I rang them they were unable to tell me the batch/revision numbers, but told me all their current Maha stock arrived last Christmas.

[Doug.S]

0G0IA

Maha is sending another replacement and will test this failed unit I'll return to them.

Replacement unit arrived and is another 0G0IA

I ran 4 AA's "break-in" and worked just fine.

Installing a next batch of batts, the unit did not activate by inserting batt in any slot. Unplugged and re-plugged in power and it did start-up check OK and next set of batts now charging OK.

Just sent unit back to Maha so no news on cause of previous slot 1 failures.

[Black Rose]

Anyone know of a smaller wall wart that can safely be used with the C9000?

The wall wart that comes with the C9000 covers up 3 outlets on my power bar. I'd like to find one that is designed like the wall wart for the C800S.

[Mr Happy]

It's likely that if you found another wall wart of the same electrical specifications, it would be of similar size and weight.

However, I have a vague recollection of seeing some kind of short extender cable that allows you to plug in a wall wart without it covering up adjacent outlets. You could try looking for one of those maybe?

[Bones]

Anyone know of a smaller wall wart that can safely be used with the C9000?

The wall wart that comes with the C9000 covers up 3 outlets on my power bar. I'd like to find one that is designed like the wall wart for the C800S.

These three prong adapters stand almost an inch tall, and the metal tang can be bent or cut back if necessary, which will almost always allow the utilization at least one adjacent outlet.

They're very common in hardware stores and home improvement outlets, so don't expect to pay Radio Shack's usurious price.

I have two in use at the moment to work around bulky adapters, one in a power bar and another in a wall outlet.

[Bones]

Anyone know of a smaller wall wart that can safely be used with the C9000?

The wall wart that comes with the C9000 covers up 3 outlets on my power bar. I'd like to find one that is designed like the wall wart for the C800S.

These rather nifty 8" mini extension cords from Radio Shack are even purpose built to work around adapters.

[Black Rose]

These rather nifty 8" mini extension cords from Radio Shack are even purpose built to work around adapters.

Those would do the trick.

I'll have to see if I can track down something like that here. We don't have Radio Shacks up here anymore. Radio Shack withdrew the RS naming rights in Canada when Circuit City bought out the RS licensee up here.

[Black Rose]

Found some. Had to order them from Tiger Direct.

I got a chuckle out of the packaging. Said it was RoHS compliant, and then the label on the cord basically says "Warning: Contains chemicals, including lead. Wash hands after handling".

I always assumed that RoHS meant lead free...

[Mr Happy]

Heh heh. They probably came from California.

California passed a law that requires any product to be carry a warning if it contains any substance that has ever been shown to be harmful. As a result, everything in California now has such a warning attached.

Which reminds me, I must take this up with the water company. They put fluoride in tap water and that has definitely been shown to be harmful. They need to put this warning on everyone's water bill.

[Black Rose]

They were made in China (what a shocker) but the warning label did specifically name California.

They are supposedly Cables Unlimited liberator cables, but came in a Ziotek bag.

[jusko]

I read somewhere in this forum that the newer version C9000 will terminate the charging process when the battery voltage reaches 1.47V. I have version 0G0E02 and it does terminate before reaching 1.48V. That means I will never see 1.48V appears in my C9000.

But then I found that most of my batteries are prematurely "DONE" including the Powerex 2700 cells. Using the Refresh Analyze mode, my earlier version (the first launched version) of C9000 recorded around 2500-2600mah discharged capacity for the Powerex 2700. Due to missed termination of the early version, I exchanged it with a newer version 0G0E02 which showed a capacity of only around 2200-2300mah for the same cells.

I have run a capacity test for the same cells with another intelligent charger and found the discharged capacity of around 2500mah, quite similar to the early C9000.

I am disappointed that Maha adopted this "Voltage Termination" method resulting in premature termination in most of the batteries.

What do you think ? I want to see your view and comment please.

jusko

[45/70]

jusko, did you let the C-9000 top off the cells for two hours after "DONE"? That would add another 200mAh or so, as this is the "top off" charge method used. Basically, I'm with you though.

Dave

[jusko]

Hi, Dave, I used the "Refresh Analyze" mode and let it do all the thing until finished. I noticed there was "REST" (topping off) after the initial charging phase and then discharge and finally charging again.

Best Regards
jusko

[45/70]

Humm, I'm too tired to look around for it, but I believe it was determined that in the "refresh and analyze" mode, the C-9000 does not top off during the rest period. This way the cells get a rest before discharging, and aren't "hot off the charger". Not sure though, you may want to look around.

Dave

Edit: After re-reading your post, I did see where you were using R&A mode. Missed that when I first posted.

[Black Rose]

I have a few Eneloops that reported 3.1% to 3.8% capacity loss during their first break-in cycle, so I decided to give them and the other June 2006 Eneloop AAs I have a refresh & analyze treatment.

I discharged the cells at 1A before performing the R & A. I used 1A for the charge and discharge values.

After the R & A cycle, the capacities reported were even lower than those from the break-in cycle (1948 after break-in, 1884 after R & A). The other cells showed similar capacity differences.

The Maha manual says that R & A is useful when the capacity of a cell needs to be determined, but if it's reporting lower capacities than the break-in cycle is it really useful?

[SilverFox]

Hello Black Rose,

The capacity of a cell is rated at a 0.2C discharge load. If you discharge at a higher rate, you can expect the capacity to drop off.

Also, keep in mind that while they are listed as 2000 mAh cells, they qualify that by also giving a minimum rating.

Tom

[Mr Happy]

IThe Maha manual says that R & A is useful when the capacity of a cell needs to be determined, but if it's reporting lower capacities than the break-in cycle is it really useful?

One could argue it's useful because it's reporting the capacity likely to be obtained from a normal charge on the C9000. Since you don't normally charge cells with the slow timed charge that the break-in mode applies, the numbers from that are less directly applicable to real life.

[Black Rose]

OK, I see. So if I used 400 or 500 mA discharge rates, I'd see better numbers.

I just put another set on the C9000 for an R & A, 1000 mA charge and 500 mA discharge. Will see how that goes.

[Mr Happy]

OK, I see. So if I used 400 or 500 mA discharge rates, I'd see better numbers.

I just put another set on the C9000 for an R & A, 1000 mA charge and 500 mA discharge. Will see how that goes.

You might see better numbers, but probably not a huge difference. NiMH are quite tolerant of variation in discharge rates and the measured capacity doesn't decrease all that much when you discharge at higher rates.

What makes more more difference in my opinion is the charging. When you do a break-in charge it is a bit like brimming your fuel tank in the car. It is like filling to the auto-cutoff, and then filling some more, and then trickling fuel in until the level is right up the filler pipe to the gas cap. On the other hand, a regular charge is like just filling to the auto-cutoff and stopping right a way.

Later model C9000s are particularly sensitive to this since they have a very conservative auto-cutoff. They stop charging quite a little time before the batteries are completely brimmed.

[jusko]

I found the latest version of C9000 uses the 1.48V cutoff rather than -△V if you would care to look at it at around that voltage.

But most cells won't be fully charged until the voltage is well beyond 1.5V. So the 1.48V is rather conservative.

[TorchBoy]

I have one from this year that stops at 1.46V or 1.47V with my Eneloops, before the top-up charge which takes them to 1.50V or sometimes 1.51V. Which version is yours, jusko?

[Mr Happy]

I have 0G0B01 and it stops at 1.48 V, but you have to watch very carefully to catch that. Once it stops charging the voltage drops in a few seconds to 1.47 V or lower so if you blink you will miss it.

The voltage actually drops all the way down to about 1.45 V and then slowly creeps up over the next hour to maybe 1.49 V on the top off charge before eventually resting back down to 1.44 V after two or three more hours.

[jusko]

......Which version is yours, jusko?

My version is 0G0E02 which acts the same way as Mr. Happy's.

Best Regards
jusko

[Handlobraesing]

So, I've found this charger is no good at discharging batteries in not so good health or testing the capacity of batteries suffering a high internal resistance.

The termination voltage on discharge is fixed at 0.90v. The discharge current is fixed at 0.9-1A and you can not change it. Changing the current setting only changes the discharge duty cycle.

The discharge voltage is taken during on cycle, so the voltage is actually the voltage under 1A load. A deteriorating cell that works fine at 250mA that can't maintain 0.9v at 1A will cause this device to stop discharging immediately only to find that the battery still holds an open circuit voltage of 1.3v

If you want to cycle the cell to improve their health, this charger won't do it, because the discharging process will immediately terminate if the voltage under 1A load falls below 0.9v

So, 500mA discharge is really more like 1A discharge for one second, no discharge for one second, 1A discharge for one second and so on.

This charger is loaded with a lot of cool OPTIONS, but the method of modulating the current is flawed in my opinion.

Both the charging and discharging current is the maximum current and changing the setting only changes the 2 second time weighed average.

[SilverFox]

Hello Handlobraesing,

You have made an important discovery... Crap cells don't perform well.

I have found that it is far less frustrating to recycle crap cells and replace them with new cells that are performing well. However, there can be some educational opportunities from playing with crap cells.

If you want to play, try this...

Charge your cells at 1000 mA. When Done is displayed, set a timer for 3 hours. When the timer goes off, start a 500 mA discharge.

Record the capacity you get and compare it to the labeled capacity of the cell.

Leave the cells in the C9000 and set a timer for 30 minutes. Then do another discharge at 200 mA.

When that discharge is completed, once again, set the timer for 30 minutes, then do another discharge, this time at 100 mA.

Next, do a Break-In cycle. Once again, record the capacity and compare it to the labeled capacity.

Set a timer for 1 hour, then discharge at 500 mA.

Record the capacity and compare it with what you got during the first 500 mA discharge. If you see an improvement in capacity, the cell is starting to recover and you can repeat this process again.

After 10 rounds of this, if your crap cells are going to recover, they should be at or above about 80% of their labeled capacity.

On the other hand, if your crap cells are still crap, recycle them and move on. If you have a secial "attachment" to them, find a crap application for them and don't be frustrated when they crap out on you.

Have you tried running any healthy cells through charge/discharge cycles on the C9000? How did they do?

Tom

[Handlobraesing]

Simple. There is almost no difference in read-out voltage in 100mA or 1,000mA, because the voltage reading is taken under load and 100mA is just 1A at 10% duty cycle.

The voltage falls below 0.90v(which is 0.95v at the terminals measured externally), then it immediately displays DONE Avail. cap 0mAh

[Black Rose]

However, there can be some educational opportunities from playing with crap cells.

If you want to play, try this...

Wow, thats a lot of time to try and recover a set of cells. I guestimated that process would take approx 25 days for 2000 mAh cells.

It would be interesting to see how much electricity would be used by the C9000 during that process compared to the results (i.e. is it worth investing $X.00 of electricity to attempt to revive the cells).

As a test to see how much power is used by the C9000, I currently have it hooked up to an energy meter to see how much power it uses for a 1A discharge cycle followed by a break-in cycle. I noticed a sizable spike on my last electricty bill, so I'm curious to see how much the break-in cycles played into that.

[SilverFox]

Hello Handlobraesing,

OK, so your crap cells show 0 mAh under a 100 mA discharge on the C9000. What do you get after running the Break-In cycle?

Tom

[Handlobraesing]

Hello Handlobraesing,

OK, so your crap cells show 0 mAh under a 100 mA discharge on the C9000. What do you get after running the Break-In cycle?

Tom

It wouldn't complete the break-in cycle. It would force charging at 2A * n% duty cycle and once it's done, it rests, and switch over to discharge, drops <0.90v and says "done".

If the cell can't hold 0.90v at full one amp, MH-C9000 will terminate prematurely. The voltage measurement is taken under pulse load which causes the voltage to drop to what you'd get under 1A load.

[Mr Happy]

I think the important part of the break-in cycle is the charging part. If the 16 hour 0.1C charge did not improve the performance of the cell to the point where it can sustain any discharge at all, then the cell is toast methinks.