What NiMH Charging Rate? 2 opposing opinions

[Benito]

I have a La Crosse battery charger. They say:

"In general, 200 mA is a recommended charging current if rapid charging is not necessary. It is definitely safe and optimum to the rechargeable batteries"

However, Battery University say:

"It is difficult, if not impossible, to slow-charge a NiMH battery. At a C rate of 0.1 to 0.3C, the voltage and temperature profiles fail to exhibit defined characteristics to measure the full-charge state accurately and the charger must depend on a timer"

So which one is it????!!!

 

[Lawn_Care]

I've always used .5C, and have NiMH AA's that are 5-years old and still going strong. I have the MAHA Powerex C-9000, but the model you have should have an adjustable charge rate as well.

Read in many places that too low a charge rate and the charger doesn't read the Negative Delta trigger to tell it when to stop charging. Supposedly a rate of just over 1/3 (.4C) is good enough to trigger the charger's program, so I always rounded up to 1/2 (.5C) just to be safe. Even at .5C, the cells still charge relatively cool and overheating has never been a problem at that charge rate.

The other method is a controlled overcharge for 16-hours at .1C, but that's mostly used in forming new cells or reforming cells that have sat unused for well over 6-months. Make sure to first discharge the cells before doing this - for maximum effectiveness.

 

[Benito]

I've read that also about the 0.4C.

So why do Lacrosse suggest 200mA which is way below that and below 0.1C in some instances?

 

[Lawn_Care]

Originally Posted By: Benito
I've read that also about the 0.4C.

So why do Lacrosse suggest 200mA which is way below that and below 0.1C in some instances?


I haven't used a Lacrosse charger like yours, so all I can go on is my experience with the Powerex C-9000 - and extensive online research. I can't see their programming being all that different regarding the Negative Delta triggers for NiMH cells, as the protocol is pretty standard in smart NiMH chargers.

 

[Benito]

There seem to be some folks saying the LaCrosse's are good at detecting voltage drops at low charging rates.

 

[gathermewool]

I just bought this same charger, since we're going to depend a lot more heavily on rechargeable batteries from now on.

I've followed their instruction manual and left it alone at 200mA, but have my 2k mah flashlight battery charged faster would definitely help, though I usually keep at least one backup battery.

I'll be following this thread closely, since what you're saying about the very low XC rate concerned me, as well. Glad to see someone else thought it was odd, as well.

 

[901Memphis]

Originally Posted By: gathermewool
I just bought this same charger, since we're going to depend a lot more heavily on rechargeable batteries from now on.

I've followed their instruction manual and left it alone at 200mA, but have my 2k mah flashlight battery charged faster would definitely help, though I usually keep at least one backup battery.

I'll be following this thread closely, since what you're saying about the very low XC rate concerned me, as well. Glad to see someone else thought it was odd, as well.


Get some 18650 rechargeable batteries and compatible flashlights if you want superior performance and charge times. Plenty of quality chargers out now too. The Panasonic 3400 mah batteries are everywhere now.

Check out this stuff for tests.

http://lygte-info.dk/

 

[Johnny2Bad]

I bought an Energizer charger and 2AA's for about $20, plus a few more 4-packs. I think they are 2200 mAH.

Charger seems to work fine, have had many dozens of charges without issue. Use them in a GPS I need daily. Some are 5 years old and still taking a charge.

They don't last as long as alkaline cells, about 10 hours versus about 20, but rechargeable beats buying and throwing.

The charger looks pretty basic, I can't imagine there is much in the way of sophisticated charging patterns there, but it works overnight no problem.

 

[gathermewool]

Originally Posted By: 901Memphis
Originally Posted By: gathermewool
I just bought this same charger, since we're going to depend a lot more heavily on rechargeable batteries from now on.

I've followed their instruction manual and left it alone at 200mA, but have my 2k mah flashlight battery charged faster would definitely help, though I usually keep at least one backup battery.

I'll be following this thread closely, since what you're saying about the very low XC rate concerned me, as well. Glad to see someone else thought it was odd, as well.


Get some 18650 rechargeable batteries and compatible flashlights if you want superior performance and charge times. Plenty of quality chargers out now too. The Panasonic 3400 mah batteries are everywhere now.

Check out this stuff for tests.

http://lygte-info.dk/


When I purchased my last two flashlights I had a set of goals:

1. I'd like to keep it in my pocket or attached to a belt loop, for easy access.

2. I'd like to be able to replace the battery, if need be, with a standard Alkaline AA, which my department provides for free, and can be brought down to the deck plates to me by one of my colleagues or "persons in training", if need be.

3. I'd like it to be very bright. This requirement meant that I could use an alkaline battery, but that the battery life would die quickly, necessitating the use of a good rechargable NiMH.

The above are due to where I work, where I use my flashlight everyday and often for simple tasks, like checking the status of poorly-lit things (lower setting) to illuminating a work area (higher setting.) I crawl around in odd spaces and don't like the feel of a clunky, large flash light, so smaller is definitely better for me. I literally have my flashlight on me at all times, even if I'm not at work.

I initially purchased a Fenix LD15, which will actually last a good while on a standard alkaline AA, but nearly forever (relatively speaking) on a 2k mAh NiMH. This flashlight is now my backup flashlight, and mostly stays in the kitchen, in a drawer for backup use.

I now DC a Zebralight SC52w L2, which is substantially brighter, but the second high setting (there are two high settings) will not work after only a few short days with a standard alkaline, but will last for a week plus of casual use with 2k mAh NiMH battery, and will provide good illumination for weeks of casual use on all other settings.

//

The battery I'm using now in the Zebralight is years old and has been used for many cycles, though I don't track use. I used to charge it exclusively with a cheap Energizer rapid charger. I just checked the capacity with the charger and it shows 2.0Ah. Even if that's off, it's heartening to see that the charger shows a full capacity.

I used the 700mA setting, based on this thread and other reading and it was nice to have a fully tested (takes longer) and charged battery, ready for use this morning!

 

[Lawn_Care]

Originally Posted By: 901Memphis
Get some 18650 rechargeable batteries and compatible flashlights if you want superior performance and charge times. Plenty of quality chargers out now too. The Panasonic 3400 mah batteries are everywhere now.


Lithium cells are definitely the way to go regarding capacity in a smaller/lighter package than NiMH is capable of. I use Lipo packs regularly in a few of my RC Planes, and they are leaps forward compared to NiCad or NiMH technology.

One thing about the 18650's, make sure and use a decent quality charger. It doesn't take much to make a Lithium pack (or cell) go thermal if overcharged. Since their charging cutoff is voltage-related, if the charger were to continue charging it to a higher voltage - it could definitely go nuclear. Never had it happen to me personally, but have read quite a few reports of this happening with the cheap ($4) ebay chinese chargers. (You get what you pay for I guess)