Will This Screw Up the Charging Circuit? MH-C401FS

[Ginseng]

I've just recently been using the fast-charge setting of my Maha AA charger and it gets the batts pretty hot, easily over 150F just before the charger green-lighted. This last set got very hot to the point where I got scared and turned a small fan on the charger and batts. This cooled them right down. My question is this:

Will force cooling the batteries and charger fool the charger into thinking the batteries are not yet full and cause it to continue charging, thus potentially damaging the batteries?

Any assistance would be greatly appreciated.

Wilkey

 

[charliek]

Re: Will This Screw Up the Charging Circuit? MH-C4

I've been charging Nimh batteries in a 1hr charger for a while- each time they get too hot to touch.... so far they haven't failed.... I don't think the charger uses temperature as a sensor to know when to switch to trickle... if they did I'd find thermistors lining the battery compartment when I strip chargers for parts. /ubbthreads/images/graemlins/smile.gif

 

[LitFuse]

I would tend to doubt it. I don't think the charger uses the temperature information as a factor in determining when the cells have reached their capacity. It may have a temperature sensitive "cut-off" as a safety feature, but that's a seperate issue.


Peter

 

[Ginseng]

Re: Will This Screw Up the Charging Circuit? MH-C4

Thanks for your comments guys. /ubbthreads/images/graemlins/smile.gif

Wilkey

Now, I wonder if keeping the fan on quickcharging batts is a good idea for prolonging life.

 

[CM]

Re: Will This Screw Up the Charging Circuit? MH-C4

I usually use a fan on the charger and batteries when charging. The charger I'm using uses -dV/dt for charge termination and not temperature. Also chargers that use temperature to cutoff charging uses a dT/dt, meaning it senses a *change* in temperature so cooling it mildly using a few CFM of air should not hurt.

 

[Ginseng]

Re: Will This Screw Up the Charging Circuit? MH-C4

Thanks CM! I looked through the manual (surprise, surprise) and it says the 401 uses 1000mA fast charge current and a negative delta V microprocessor.

Wilkey

 

[kitelights]

Re: Will This Screw Up the Charging Circuit? MH-C4

The fan is a good thing. It will help your cells to last longer and will not interfere with the charging cycle (according to Maha's tech).

What kind of cells are you using? Mine don't get that hot. (100 - 120)

 

[OrBy]

Re: Will This Screw Up the Charging Circuit? MH-C4

I just ordered and got a MH-C401FS and 8 PowerX 2200mAh NiMH AA cells.
I got excited and put 4 of em on on fast charge cause I wanted to see what they can do. I checked on their temp with my hand (no tools to do it the right way) and by the time they were almost done I could not leave my hand it them because it was just to hot!!!
I almost was about to pull em out cause I thought the charger was defective when the light went green on 1 cell then I realized they were almost done.
I have noticed that NiMH seem to get very warm right near the end of the charge - MUCH more so then NiCd.
kitelights - Thank you for posting that info from Maha - I will setup one of the spare pc fans I have around to do this.
On a side note - HOLY @$%^$#%$^#$%^#%$@$% these 2200's make my BB400 Q3 bright!!!

 

[Ginseng]

Re: Will This Screw Up the Charging Circuit? MH-C4

Kite, I use Maha Powerex 2000Ah AAs. I've measured surface temperatures over 140F regularly from about 50% drained condition.

Wilkey