Need, Odd cell charger help. Update: so is this what I need?

[Juggernaut]

What's the best way to charge one F or M sized NiMH battery? I need to be able to charge either a single cell of one or the other type, probably an F cell since I can't find any M cells in stock:shrug:. Thanks:thumbsup:.

 

[donn_]

Re: Need, Odd cell charger help.

The cheapest solution would be one of these:

http://www.batteryjunction.com/rc900.html

or something like it. Then use magnets on each end of the cell, and fasten the alligator clips to the magnets.

 

[Juggernaut]

Re: Need, Odd cell charger help.

Yes I figured I'd have to attach leads on the terminals, but what smart charger is rated to charge 13,000-26,000 mah that I could use?

 

[donn_]

Re: Need, Odd cell charger help.

I doubt if you'll find a smart/hobby charger which will charge these cells at their maximum possible charge rate. The F cell at BatterySpace will take a 13A charge rate. To do that, you'll need a serious (and more expensive) outfit. A Bantam BC6, for example will cost you ~$170, and will only do a 5A charge rate. That get's your charge time to a bit less than 3 hours.

 

[HarryN]

Re: Need, Odd cell charger help.

The Triton 2 max charge (per charge cycle) is 10,000 mah. Depending on your view, this might work (or not).

My experience is that often, my cells are not even 1/ 2 dead when I re-charge them, so it is not a big deal if the cell capacity exceeds the charger limit.

In the case that the cell really needs more than 10 AH of charge, just run 2 cycles in series.

Of course, there is always Schultze, the wonder chargers. I don't know, but would guess that they have a model that can work for you (technically).

The R/C folks will sometimes do some fairly abusive "fast / constant voltage" charging of high capacity cells in the field to keep the day going, probably at the expense of cell life - but they think of cells as almost disposables sometimes anyway.

From my perspective, if you are spending the $s on a quality cell, going to a cheap or abusive charger is just wasting the money you spent on the cells. Then again, I don't mind charging for a few hours either.

 

[Juggernaut]

Re: Need, Odd cell charger help.

I don't need to charge it fast, any amount of time is fine "within 18 hours" I only need one, and there is no reason to have more for what I need it for. I was going to run 7x NiMH AA batteries in parallel, but that's just stupid when I can use just one of these cells, and since they cost the same, it is obvious which is the right choice:ironic:.

The Triton 2 cost $135! That's not bad since it charges just about anything:thumbsup:, but I need it to charge one cell. I have a 1.2 volt NiMH charger for sub-C cells but it is a simple "dumb" charger and only charges at .3 ah so it would take over 36 hours:shakehead!!

 

[donn_]

Re: Need, Odd cell charger help.

The cost of the cell(s) is not the only consideration, as you are discovering.

There is a far larger market for AA cells, and, consequently, adequate chargers for them.

Look at the cost of the entire package...cells, charger, time, etc..

 

[Juggernaut]

Re: Need, Odd cell charger help.

Dang, this sucks:mecry:, that cell would have been great for around $15, now I'll have to buy 8 AA batteries, and a charger "yes I can do it under $20" but I have to build some igneous devise to run all them together, with proper contact "that can be taken apart to recharge them very often" I'd like to ask for some advise on a good 8-6 AA charger/ battery combo deal:thinking:. But I'd think I'd need a new thread for that:sigh:.

 

[Mr Happy]

Re: Need, Odd cell charger help.

Dang, this sucks:mecry:, that cell would have been great for around $15, now I'll have to buy 8 AA batteries, and a charger "yes I can do it under $20" but I have to build some igneous devise to run all them together, with proper contact "that can be taken apart to recharge them very often" I'd like to ask for some advise on a good 8-6 AA charger/ battery combo deal:thinking:. But I'd think I'd need a new thread for that:sigh:.

Well hey, you don't need an expensive charger to charge a single NiMH F cell. A cell that size is going to be pretty robust and will not be fussy about whether or not you are using a $135 power supply to feed electricity through it!

Look at it this way. Suppose you have a 14,000 mAh F cell. To charge it, all you need to do is feed current through it. Have you got a 12 V charger for car batteries, or some other power supply that can provide 2 A or so? Let's say you have, then you can hook up that supply to your F cell in series with an automobile bulb to limit the current, say the regular 12 V 21 W variety of brake lamp bulb. This is going to feed a little under 2 A into the cell, so it should get charged in 8-10 hours or so.

So go ahead and do that. Now you need to know when the cell is charged. You can monitor the voltage across the cell and stop when it is no longer rising. Or you could stop when it reaches about 1.5 V. You can also feel the cell or measure its temperature and stop when it starts getting warm. At the last resort you can stop after 10 hours of charging.

Basically, there is nothing to it. You do not need expensive battery chargers for this job. All you need is a way to feed a measured amount of current through the cell and a way to stop at about the right time. Go ahead and play!

 

[Juggernaut]

Re: Need, Odd cell charger help.

Great Idea:twothumbs:twothumbs!! I jest went to see if it would work, well I chucked my 2,4,or 6 amp smart charger up to my 30 watt RayOvac lantern, the light turned on strong, while giving the battery "a 2650 mah Duracell AA" 1.75 volts:thumbsup:. The bulb pulls 2.5 amps. I can charge this cell up to 1 C, so what is the best setting to use? 2,4, 0r 6 amps? 6 should work fine right:shrug:? Does the battery see 6 amps? Because then it would only take a bit over 2 hours to charge and that would be great:thanks:.

Since I have found what appears to be an easy universal charger for these cells, my next step is to try and find M-cells! battery space.com has them but they are out of stock:sigh:. I think people use them for high performance scoters and stuff:thinking:, so there has to be a place to buy them, but were? I'm looking for the 20ah one for $20, since any higher and I'll start to out strip the SLA "in capacity" they are going to be running with.

 

[Mr Happy]

Re: Need, Odd cell charger help.

Great Idea:twothumbs:twothumbs!! I jest went to see if it would work, well I chucked my 2,4,or 6 amp smart charger up to my 30 watt RayOvac lantern, the light turned on strong, while giving the battery "a 2650 mah Duracell AA" 1.75 volts:thumbsup:. The bulb pulls 2.5 amps. I can charge this cell up to 1 C, so what is the best setting to use? 2,4, 0r 6 amps? 6 should work fine right:shrug:? Does the battery see 6 amps? Because then it would only take a bit over 2 hours to charge and that would be great:thanks:.

Well you've got to use the bulb to limit the current, so the 2, 4 or 6 amp setting won't really make any difference. And if you are charging a cell manually, you don't want to go too fast because you won't have accurate control over when to stop charging, and it will be easy to damage the cell by overcharging it. To be safe I wouldn't go above 0.2C.

 

[Juggernaut]

Re: Need, Odd cell charger help.

Ok these F- cells charge up to about 1.42 volts while on the charger and when left on for another hour don't increases anymore. If I let them sit for an hour they read 1.36-1.38 volts. Is this charged enough?