Maha C9000 with D cell adaptor, is it possible?

[Mr Floppy]

Has anyone tried using the C9000 with D cells?

What I was considering doing when I get the C9000, is to make an adaptor by connecting a plastic D cell holder, crimping the wires to thumb tacks on both ends of an AA sized bit of dowel.

Are there any warnings in in the documentation that advise against doing this? Does any one have any experience/advice/warnings they wish to share?

[rizky_p]

age old question.

yes it is possible, but as some might argues that charging Nimh without thermal monitoring is somewhat dangerous.

Not sure if additional length in charging path will increase resistance that the charger will refuse to work.

[VidPro]

OOPS , i think i messed up, edited, it should be more correct now

you see the 9000 terminates on high voltage right?
so it would not have the same issues a lacross 900 would, (if that is true).

The added resistance and the slower charge in C things (for a big D) means the charger wont terminate on a V-Drop , that is what the "smart" charger is expecting. so after you restart the charge a time or two to get the full charge due to whatever timeouts it has , it still needs a termination method, at the end of charge, or a slow charge rate, that is within the specs for the cell.

IF the/YOUR 9000 WILL certannly terminate at around 1.47v then it should stop before overcharging, and then if you charge below .1c by a little bit you will stay in spec, FOR a slow overcharge rate ALSO either or.
then caculate the rate it runs if a power interruption occurs, and see if that is within spec, for a slow rate.
that just leaves it timing out before a complete charge, based on the miliamps that its set for before it decides that a AA would be baked to death.

the lacross 900 will still be looking for a termination that wont exist properly, and used at 1000-1800 it would not be the thing to do it with, the 900 could be done at slower rates, and still be within the slow rate charge specs. This is of course (again) after having cycled the charger enough to GET to the end of charge.

Any added resistance could change the voltage termination, or the v-drop termination, brads and magnets and bad solder joints, cheap wire, long wire, any added resistance will change what the stupid computer sees .

so either achieve a viable readable by the stupid machine V-drop by having a very fast charge FOR the cell , and low resistance connection, that would be like at least 2+ amps,
or
have a voltage termination, when it reaches high voltages, finished off by topping,
Or
just slow charge it within slow charge rate specs.

[Mr Floppy]

yes it is possible, but as some might argues that charging Nimh without thermal monitoring is somewhat dangerous.

The features of the MH C9000 include:

* Negative delta V, peak voltage, dT/dt (temperature rise) and max
* The MH-C9000 Battery Charger has excellent Temperature protection
* Four independent thermocouples to manage rechargeable battery temperatures.

So that factor is covered?

you see the 9000 terminates on high voltage right?
so it would not have the same issues a lacross 900 would, (if that is true).

I was contemplating getting the lacross BC-900 too.

I dont have the Maha yet, but one of the features I read about was the ability to program the charge rate. Not totally sure what that means, will know more about it when I get the charger.

With the resistance, what are we looking at here? 1 ohm? 1/2 an ohm? I thought I read something about setting termination conditions but I could be mistaken.

One of the things the Maha unit says is:
"

The micro controller can support higher capacity batteries without any problem (however the capacity calculation limit is 20,000mAh)."

Would that not mean that some of those calculations are factored? Maybe not the resistance factor.

Another question, I used to charge 1/2 AAA and 3mm AA batteries with just my regular battery charger. They seem to charge ok and the charger goes off into trickle mode. I basically made up the length but using a bit of dowel with a wire covering the length and tacking it to the ends. So what should I have been considering when I charged them like this? They normally have a capacity of around 270 - 300 mAh

[VidPro]

yes but how do you get the thermal protection TO a battery that is hanging out the side, that is the issue, not that the chargers or power adaption, has thermal protection but the battery is monitored, so if/when when the batteries overheat the computer can react. the thermal probes are very close to any battery that is in the original battery slot.

20amps, yes that is right the 9000 does have the capacity thing covered, so you don't have to keep recycling the battery back on.

if it was OHMS of resistance it wouldnt be a problem, heck some 1000feet of copper wire are only a single ohm or so, so i dont use that kinda math stuff, its the voltage drop with any of the connections and wires, and any looseness or burping or minor changes in those connections. A mere foot of say 22ga wire can change a power curcuit by a lot, its the reality not the math, to try and quantify the small ammount or determine a limitation would be a waste of time, the Rue Goldberging of the charger would just be done as well as you can do it, then it will work.

the way it comes batteries lock into the metal, solidly, the metal is connected to the board, with like 0 resistance, calibration and testing and programming junk was all done with the intended connection that doesnt get a inch away and is all in copper foils on the board. it would not TAKE much variations from that to have a variation to the Brain, not because your adding in large resistance, but because there is so little to begin with.

so you would try and keep all the wires short , of fair ga. size, of good copper quality, all conections very solid, nothing bumping things, or rattling them, ya know how many things can rattle a connection that is not perfect. within the capability of still accomplishing your goal, not nessisarily going overboard. so the brain still can do its testings and comparisons

a commonly sluffed off voltage drop of say .02volts would (for example) raise the 1.47 to 1.49v a huge difference in very carefully selected voltage termination. (assuming your model has this feature) that is why there should be as little resistance as possible.

a variation in the connections of mere milivolts used to determine the v-drop would effect any termination based on V-drop, which the computer samples and resamples and resamples, with PULSES of power occuring, pulses that can be changing any connection that is not very well connected. that is why no connection should "Change" in resistance at all.

[TakeTheActive]

Has anyone tried using the C9000 with D cells?

Sure! CLICK on my Sig Line LINK and look under Maha Powerex MH-C9000.

...What I was considering doing when I get the C9000, is to make an adaptor by connecting a plastic D cell holder, crimping the wires to thumb tacks on both ends of an AA sized bit of dowel...

...Does any one have any experience/advice/warnings they wish to share?

• You lose MAX TEMP protection
  .
• IIRC, someone mentioned that wooden dowels DO conduct some electricity
  .
• You shouldn't leave it unattended.

[Mr Floppy]

Thanks VidPro for the explanations, and big thanks TTA for that list. It answers a lot of questions.

Interesting point about the dowels. I have to see what else I can use.

[Mr Happy]

Don't worry about the dowels. Dry wood is a perfect insulator at low voltages. Leakage current through wood is only an issue when potential differences are in the hundreds of volts and above.

[Bones]

If you own other than the first release of the MH-C9000, then I believe the only realistic way to utilize it to charge D-cells is by invoking a timed charge with the Break-in function.

Revised versions lowered the maximum capacity cut-off from 20000mAh to 4000mAh, so charging terminates when that point is reached during any other charging mode.

However, the Break-in function still provides for cells up 20000mAh in capacity, so you can utilize it to invoke a timed charge at up to 2Ah for up to 16 hours.

For those with an original release MH-C9000, the caveats already mentioned apply for charges that will require less than 20000mAh.

Power Me Up's D-cell charging setup:

http://www.candlepowerforums.com ,,, post2705095

Power Me Up also provided an alternate source for the adapters that were utilized in this post:

http://www.candlepowerforums.com ... post2705813
.

[leon13]

Revised versions lowered the maximum capacity cut-off from 20000mAh to 4000mAh, so charging terminates when that point is reached during any other charging mode.
.

I just talked to MAHA technical support and they are not aware of any cut-off lowered from 20,000mAh to 4,000 mAh. Would you mind sharing where you obtained the information? I would not want to buy the charger if the cut-off has been lowered but, as I said, MAHA claims that is not the case.

Thank you in advance for any information.

[desirider]

Leon, thanks for clearing this up with MAHA. I am also working on building a D cell adapter for the C9000. Several people have done this before and there are a few threads here that walk you through the process.

Even assuming a 4000 mAh cutoff I thought the adapter was still worth it. You can always reset the C9000 and repeat the process multiple times to fully charge D cells. Looks like we don't even have to do that.

Thanks,
Desirider.

[Viking]

I just talked to MAHA technical support and they are not aware of any cut-off lowered from 20,000mAh to 4,000 mAh. Would you mind sharing where you obtained the information? I would not want to buy the charger if the cut-off has been lowered but, as I said, MAHA claims that is not the case.

Thank you in advance for any information.

It's mentioned in this thread.

http://www.candlepowerforums.com/vb/...9000-20-000mAh

[Russel]

The reason that I made an adapter was so I could use the MH-C9000 to run a break-in cycle on my D cell NiMH batteries. The 4000mAh charge limit doesn't apply to break-in mode.

[desirider]

Russel, can confirm or dispell the 4000mAh limit in the regular "Charge" mode?

I read your original thread about the D cell adapters and was certainly inspired by it. I found Bulgin D cell adapters to replace the ones you built.

[Russel]

Russel, can confirm or dispell the 4000mAh limit in the regular "Charge" mode?[...]

Yes, I can confirm the 4000mAh limit in "non-breakin" modes. The first MH-C9000 units that were sold didn't have that limit, but the firmware was changed latter.

Here is a post with some good information, although you should take the time to brouse through the whole thread:
http://www.candlepowerforums.com/vb/...=1#post1891028