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Thread: Maha MH C808M Charger

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    Thumbs up Maha MH C808M Charger

    Maha has stepped up to the high capacity charging challenge by offering a new charger in their line up. The C808M is capable of charging AAA, AA, C, and D cells. It defaults to charging at 2 amps, so it does not take an extended period of time to charge up high capacity cells. My 9000 mAh D cells use to take around 36 hours to charge on my Vanson Speedy Box. Using the C808M, it only takes around 6 hours. That is a vast improvement.

    This charger has 8 independent charging bays and charges AAA, AA, C, and D NiMh or NiCd cells. You can mix and match to your hearts content, but once the charge rate or conditioning cycles is set, it is set for all 8 bays. You can not be conditioning cells in bays 1 and 2, then set it up to charge cells in the other bays. The choices are:
    1. default charging (0.7 amps for AAA cells and 2.0 amps for AA, C, and D cells),
    2. soft charging at half the default charging rate, or
    3. conditioning.
    The conditioning cycle first charges the cells (at either the default rate or the soft rate), then discharges them at 0.25 amps EDIT It seems I was a bit off on this, it is more like 350 mA but see post #54 for the real numbers END EDIT, then charges them back up again. At the end of the charging cycles, a trickle charge of 0.007 amps keeps the cells ready to go. This low trickle charge rate may make this the only charger that you can leave your cells in for an extended period of time without harm. I do not recommend leaving batteries on trickle charge, but if you want to do that, this is the charger for you.

    The C808M comes with a 3 year warranty from Maha.

    The C808M does not use springs in its contact set up. It has individual contacts for each size of battery. This makes for a very robust set up, and allows some spacing between cells to keep them cool. The trade off is that the unit has some size to it. The dimensions of the charger unit are EDIT Oops 7.5” x 3.5” x 1.75” is for the C801D the C808M is 12.63" x 5.25" x 3". END EDIT In addition it is powered by an AC switching adapter that is 5.125” x 2.25” x 1.185”. The power supply input is rated at 100-240 volts 50-60 hertz, so it will work worldwide. It uses a maximum of 1200 mA. Mine came with a North American 2 prong blade plug, but you can get power cords to match the outlet style where you are. The power supply uses a DIN plug to connect to the charger. There is no 12 volt DC power provision.

    The back lit LCD display shows a graphic of what is going on in each slot and also displays the English words Condition, Charge, and when the charge is completed, the word Done is displayed for each slot. When an error occurs, the word Done will be flashing in the slot where the error occurred. The graphic is the outline of a battery with three bars in it. During discharging, the outline disappears and the bars change from three, to two, to one, then none at all. When charging starts, the outline comes back on. The charging progress is displayed by the three bars until “Done” indicates the beginning of the trickle charge.

    A very soft “click” can be heard as the unit charges. This is a result of the pulse charging used while charging, and also while on trickle charge.

    You have to pay attention when inserting the cells for charging. The negative end goes in first and then you press down to snap the positive end in place. AAA cells are placed in the bottom and to the right. I had some initial difficulty getting them in the right place, but when I looked at what I was doing, there were no more difficulties. I have noticed that I often don’t get the AA cells completely snapped into place. The display is very good at letting you know that the cell is not in place, because there will be no graphic display.

    The right side of the unit gets warm during discharge, and you are instructed to insert cells starting from the left side. I asked Maha about this, and they said it was simply to keep the cells cooler. You are also instructed to put the larger cells on the left side and work your way right with smaller cells. Once again Maha says that they are trying to keep the heat down.

    The operators manual also states that you should not leave an empty slot when putting your cells in for charging. Maha does not know why that statement is in there… Anticipating some problems, I did a number of tests starting from right to left, filling the middle slots, and skipping every other slot. The C808M took it all in stride and performed flawlessly. It truly is an independent 8 channel charger – with no restrictions.

    I did have some problems charging NiCd AA cells. It seems that they end up at a higher voltage than the C808M thinks they should and I ended up with an error signal. I also tried to charge some Alkaline AA cells and got the same error signal. I talked with Maha about this. They indicated that the charging algorithm was designed for NiMh chemistry, and it should work well with NiCd chemistry as well, but I was finding a bit of a difference. The cells did end up fully charged, they just ended on an error signal and the trickle charge was terminated.

    So, if you are charging NiCd cells, you may run into this same thing. Please note that this did not occur with every cycle. Sometimes everything came out fine, but other times I would get the error signal.

    The cells come off the charger warm. The highest temperature I observed was 96 F. Maha claims the high temperature cut off is set at 120 F. The charging is consistent from bay to bay.

    I am used to cells coming off the charger at around 1.45 volts. My cells came off the C808M at 1.43 volts. This charger is right there at the top of the pack as far as complete charging goes. The AccuManager 20 just barely beat it out, and it does slightly better than the BC-900. It also just barely beats the Vanson Speedy Box after the charge has completed and the cells have trickle charged for an additional 24 hours.

    I am very pleased with the C808M. It will take very good care of your cells during charging and won’t cook them during trickle charging. It also does a very good job of packing a lot of capacity into your cells.

    The only error I noticed was while charging NiCd cells, and when I tried to “trick” it into charging Alkaline cells. I believe the NiCd error was because the voltage went higher than expected.

    I can give this charger a big “thumbs up” and highly recommend it.

    Tom

    Edit: I forgot to mention that this charger does not have a on/off switch. The LCD display comes to life when you put a cell in to charge, and goes off when you remove all the cells.

    I received an eMail from William at Maha Energy. He explained that the flashing Done that I am seeing while charging NiCd cells is not an error. It is just indicating that the charge was terminated on high voltage rather than delta voltage. He is considering revising the operators manual to include this information.

    By the way, William is the one that sent me the charger to check out. Thanks William!!! If you have any questions, William is the one that programed the charging algorithm used by this charger. He has been most helpful in helping me understand how this charger works. If you have questions, let me know, or get in touch with William directly at www.mahaenergy.com .

    Another Edit:

    Some people have noticed that the 808 will flash "Done" when charging NiCd cells. This interrupts the conditioning cycle and makes that cycle useless for NiCd cells. This is unfortunate because NiCd cells need to be conditioned more often than NiMh cells do.

    This does not happen with every NiCd cell, but it appears that the 808 will terminate the charge when the voltage reaches 1.6 volts. This keeps people from trying to charge alkaline cells. Some NiCd cells bump against this 1.6 volt cut off, resulting in the flashing "Done" and ending the cycle.

    William was kind enough to reveal a work around for this. You put 1 NiMh cell in slot 1 and select conditioning. When the cell enters the discharge phase, you load up the other slots with your NiCd cells. Once the unit has entered the discharge phase, it does not try to charge the additional cells before discharging them. The results will be a conditioned NiCd cell. You may end up with a flashing "Done" at the end of the charge cycle, but the cell will have gone through the discharge cycle and should be conditioned.

    I must add that I have been using this charger for several months now and still am very pleased with it.
    Last edited by SilverFox; 07-21-2006 at 08:41 AM.
    Behind every Great man there's always a woman rolling her eyes...

    Most batteries don't die - they are tortured to near death, then murdered...

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