Testing C/D cells in Maha C9000

[Bonky]

yep, the reason wood popped into my mind is that it's easy to find a dowel the right diameter and easy to cut it to the right length. Plastic would have to come pre-formed (like the adapters) and would be more expensive.

 

[VidPro]

wanna make your OWN plastic things, you could try TAP plastics acrylic tubes, and BALLS, the tubes come in many sizes, and the balls fit in the end, and with acrylic solvent (called glue) you could meld the ball into the end of the tube.
then you could saw/drill the solid ball and mount in the solid connections, it would all work out great till the heat hit and turned it all into a acrylic blob but that is one way to get plastic that cuts as quick as dowels. with the one caveat that they are certannly not heat resistant.

 

[Black Rose]

Is there a desired guage of wire to use for connecting the C/D cell adapters to the C9000?

All I currently have is 24 guage teflon coated silver braided wire.

 

[Bonky]

I would assume the bigger the better.

 

[Black Rose]

But wouldn't a larger wire result in more resistance?

The D cell holders I am looking at come pre-wired and have what looks like 22 or 24 guage wire.

I'm thinking it may be simpler just to buy a charger designed for D cells and be done with it, although using the C9000 on them would be nice.

 

[VidPro]

But wouldn't a larger wire result in more resistance?

The D cell holders I am looking at come pre-wired and have what looks like 22 or 24 guage wire.

I'm thinking it may be simpler just to buy a charger designed for D cells and be done with it, although using the C9000 on them would be nice.

the larger and the better a wire is the less resistance it has, like a good copper wire, less resistance.
The "stuff" that comes on a RadShack holder is , , , easily replaced.
also many battery holders have press-fit or riveted stuff in them, i always like to solder that direct, so the wire is on the tab and spring , so it doesnt come disconnected/loose, hard to do when they melt so easily.
speaker wire often has nice copper in it usually and its cheap.

resistance higher and lower is always confusing at first thought, less is more and more is less, so its a bit confusing.
so a person could think ZERO resistance is "best", then its easier to think of it, anything more than zero is more resistance, and resistance is less connection.
More resistance is less connection.
bet that didnt help

 

[Bonky]

think of it like water in a pipe, the larger diameter the pipe the easier the water will flow through it.

 

[Black Rose]

Well here's my latest invention, based on ideas I've gleaned from others on this forum.

18 gauge copper wire with #8 ring terminals soldered on the ends.
Hardwood dowels with electrical tape on the ends (in case there is any moisture in the wood).

1/4" nickel plated rare earth magnets hold the ring terminals to the positive and negative ends of the batteries.

The D cell holders that are available locally are $5 a piece and have 22 or 24 gauge wire attached.
The holders I really want are too expensive to obtain at the moment, so this will suffice for now.

 

[TakeTheActive]

1. Is the Dowel -> Ring Terminal -> C9000 connection a "Pressure Fit" or are there screws too?
   .
2. Is the Cell -> Magnet -> Ring Terminal connection magnetism only?
   .
3. What is your source and price for the magnets?
   .
4. Have you charged the D with 2000mA and checked all the connections for heating?

Thanks!

 

[Black Rose]

1. Pressure fit.
2. Magnetism only.
3. Lee Valley tools - variable price depending on quantity purchased. I bought 10 and paid 0.27 each CDN.
4. No, I'm only planning on doing 1500 mA (0.5C)

EDIT: I have been checking the cells and connections during the discharge cycles (1000 mA) to check for heating.

 

[Black Rose]

I did a charge of the Rayovac Hybrid D cells at 1500 mA using the C9000 and it seems to be working OK.

There were no heat issues with the cells or the connections with this first charge, so that is a good thing.

EDIT: There was a problem with a bad connection due to the pressure fit of the ring terminal that resulted in one channel not having full contact.
That affected the overall charge for that bay. I have resolved that issue and am now recharging the cells to see what affect it had on the capacities.

I'm not sure how much additional resistance, and possibly charging innefficiencies, have been introduced by using the wire jumpers and magnets to charge the cell.

 

[Bonky]

I can't imagine you could do much better than that. The voltage readings on the charger might be a little off with the extra wire, but I can't imagine it would be enough to make a difference.

Might be interesting to read the voltages at the battery terminals themselves with a multimeter to see if there's any difference vis-a-vis the charger's display.

 

[Black Rose]

Well I completed a break-in cycle on the Hybrid C & D cells and it went well.

My only concern about the setup I used was that the slightest bump had the potential to break the connection to the positive or negative ends of the cells, since the only thing holding the ring terminals on them was magnetic force.

I can't afford to buy a Maha C808M, so I am tempted to buy some C & D battery holders and solder leads to those to have more solid connections.

The wooden dowels seem to have worked OK (nothing burned) but I'd like to use safer material for the dummy cells.
I might bite the bullet and order those AAA->AA adapters from KD and do something with those.

Or I could spend $27 and get the ROV PS20 Universal charger and hope it uses a charge current that is within the preferred range for NiMh cells.

 

[Mr Happy]

Well I completed a break-in cycle on the Hybrid C & D cells and it went well.

My only concern about the setup I used was that the slightest bump had the potential to break the connection to the positive or negative ends of the cells, since the only thing holding the ring terminals on them was magnetic force.

I can't afford to buy a Maha C808M, so I am tempted to buy some C & D battery holders and solder leads to those to have more solid connections.

The wooden dowels seem to have worked OK (nothing burned) but I'd like to use safer material for the dummy cells.
I might bite the bullet and order those AAA->AA adapters from KD and do something with those.

Or I could spend $27 and get the ROV PS20 Universal charger and hope it uses a charge current that is within the preferred range for NiMh cells.

If you feel the magnetic connections were weak maybe it is because you had the ring terminals between the magnet and the battery. I somehow feel that if the magnet was fixed directly to the battery it would be very difficult to shift, especially with the very strong magnets around these days.

I am also curious why you should have any fear about the wooden dowels being unsafe...? There really is no chance of a problem there unless something gets hot enough inside the charger to start a fire, in which case your C9000 will already be melting into oblivion.

On balance I would say what you have there is fundamentally good and just needs a bit of fine tuning.

 

[TakeTheActive]

...EDIT: There was a problem with a bad connection due to the pressure fit of the ring terminal that resulted in one channel not having full contact.
That affected the overall charge for that bay. I have resolved that issue and am now recharging the cells to see what affect it had on the capacities.

I'm not sure how much additional resistance, and possibly charging innefficiencies, have been introduced by using the wire jumpers and magnets to charge the cell.

I was initially concerned about your using 'tinned' ring terminals and if filing off the coating would 'reduce the resistance / improve the connection'.

 

[Bonky]

There's nothing unsafe about the wooden dowels. What I would do is put a small screw in each end that not only holds down the wire (via a loop connector) but also serves as the connection to the charger.

And I would solder the magnets onto the ring connectors of the other ends and attach them directly to the cells.

 

[Bonky]

Unless you soak your dowels in sea water for a month before using them, they are going to have a resistance pretty close to ∞ for our purposes..

 

[Black Rose]

If you feel the magnetic connections were weak maybe it is because you had the ring terminals between the magnet and the battery.

I had the magnets on their sides, so that the side of the magnet passed through the hole in the ring terminal to hold it in place.
I also tried having the magnet flat and holding the terminal in place that way. Either way the connections seemed they might come off if the wires or batteries were moved enough.

I somehow feel that if the magnet was fixed directly to the battery it would be very difficult to shift, especially with the very strong magnets around these days.

I could try attaching the magnet to the battery, but I would have to sandwich the ring terminal between two magets.
The ring terminals I bought do not appear to be made of a material that the magnets will adhere to. I'll check that again tonight.

Maybe I simply need to get the next size up in the magnet (3/8", 5lb strength).

I am also curious why you should have any fear about the wooden dowels being unsafe...? There really is no chance of a problem there unless something gets hot enough inside the charger to start a fire, in which case your C9000 will already be melting into oblivion..

Good point. I had read SilverFox's comment and saw your formulas
Not sure if I needed the electrical tape on the ends of the dowels, but it's an extra layer of protection.

On balance I would say what you have there is fundamentally good and just needs a bit of fine tuning.

You're right, it just needs some fine tuning.

Even my wife questioned why I want to significanlty later paths when what I did worked quite well.

She went from "You're not going to leave that thing running overnight are you?" to "If it works and it's safe, why spend the extra money to significantly change it?".

What I would do is put a small screw in each end that not only holds down the wire (via a loop connector) but also serves as the connection to the charger.

And I would solder the magnets onto the ring connectors of the other ends and attach them directly to the cells.

I could try that as well. The magnets are cheap enough and easily available locally if they get heat damaged.

 

[Black Rose]

I confirmed that the magnets will not adhere to the ring terminals.

I did try sandwiching a ring terminal between two magnets, and that is one solid connection. I think that may be the answer to that problem.

Can too much magnetic force do any damage to a battery?
The magnets I am using are rated at a maximum of 2.5 lbs of magnetic force.

 

[Bonky]

I confirmed that the magnets will not adhere to the ring terminals.

Sux

I did try sandwiching a ring terminal between two magnets, and that is one solid connection. I think that may be the answer to that problem.

Nice!

Can too much magnetic force do any damage to a battery?
The magnets I am using are rated at a maximum of 2.5 lbs of magnetic force.

It'll be fine.