On Loading the MH-C9000

[Bones]

I thought it might be helpful to be able to visualize the shape of the contact tangs when deciding how to load the MH-C9000:

It's not evident from this image, but each positive tang sits in its own slot in the charger body, and has no provision for compression.

Although the manual suggest inserting the positive end of the AA cell in first and removing it last, this can cause torn wrappers on the bottom end of the cell. To avoid this, users are choosing to seat the negative end first; then exerting enough pressure on the cell to compress the negative tang and allow the positive end to slip into (and out of) place.

There have also been been query's as to whether the AAA cell should sit parallel to the bottom of the charging bay, and it should. In those situations where it doesn't, it may be getting hung up on the wedge shaped protrudence situated between the upper and lower contact points on the positive tang. I presume the wedge is there to prevent AAA cells from popping out of place.

My personal technique for loading the MH-C9000 is to first unplug the charger and then insert each cell into place starting with the negative end. After making sure each cell is properly seated, I give it a rotation along its longitudinal axis to maximize its contact. While rotating the cell, I also position the seam of its wrapper at about twelve o'clock. This prevents it from inadvertently interfering with the heat sensor which is located on the left side of each slot just forward of the negative tang. Only then do I plug the charger in and proceed with programming.

Incidentally, those are home-made spacers on the back of the positive tangs. They are there to ensure the relatively short positive post of the original Eneloop can make solid contact. They were fashioned out of the bottom fold of an Oxford file folder.

 

[Mr Happy]

Re: MH-C9000 Contact Tangs - Exposed

I thought it might be helpful to be able to visualize the shape of the contact tangs when deciding how to load the MH-C9000:

Nice pictures. One interesting thing about the negative tang for AAA cells is that due to design or manufacturing defect it is not tall enough. Therefore, instead of sitting in the middle of the negative cell plate, the V-shaped contact (circled) only just reaches the edge of the cell. If an AAA cell has insulation that wraps round the end, the insulation will tend to stop the negative tang from making contact with the cell.

Although the manual suggest inserting the positive end of the AA cell in first and removing it last, this can cause torn wrappers on the bottom end of the cell.

That's true.

To avoid this, users are choosing to seat the negative end first; then exerting enough pressure on the cell to compress the negative tang and allow the positive end to slip into (and out of) place.

This is exactly how I do it.

My personal technique for loading the MH-C9000 is to first unplug the charger and then insert each cell into place starting with the negative end. After making sure each cell is properly seated, I give each a slight rotation on its longitudinal axis to ensure the best possible contact. Only then do I plug the charger in and proceed with programming.

I don't do the unplugging thing though. When plugging the charger back in this leads to a race to program every cell before the last ones fall back on the automatic charge program.

 

[Bones]

Re: MH-C9000 Contact Tangs - Exposed

...
One interesting thing about the negative tang for AAA cells is that due to design or manufacturing defect it is not tall enough. Therefore, instead of sitting in the middle of the negative cell plate, the V-shaped contact (circled) only just reaches the edge of the cell. If an AAA cell has insulation that wraps round the end, the insulation will tend to stop the negative tang from making contact with the cell.
...

Thanks for mentioning this Mr Happy. It's another factor to consider when loading the MH-C9000, and one I hope MahaEnergy considers when replenishing their supply of negative tangs.

As well, because the negative tang contacts the AAA cell on it's outer edge, it can make rotating the cell to decrease its contact resistance inadvisable if the tang could be digging into its insulation.

...
I don't do the unplugging thing though. When plugging the charger back in this leads to a race to program every cell before the last ones fall back on the automatic charge program.

I have a first edition, so our chargers may not work the same, but I find that powering up the charger after the cells are properly seated gives me more time to program.

My settings only activate for one slot at a time starting with the outer left, so with the cells already seated, I'm ready to start programming as soon as the settings activate for each slot. I also find that being able to move directly from slot to slot allows me to establish a sort of rhythm if you will.

However, if I'm customizing the settings for each individual cell, then loading and programming each slot sequentially seems to work better at times as well. Fortunately, the MH-C9000 can accomodate either preference.