Older Chargers and new NiMH cells /2700mAh, Eneloop, RayoVac Hybrid/

Wurkkos

stamat

Newly Enlightened
Joined
Oct 28, 2005
Messages
44
I wonder if my 3 year old MH-C401FS Maha charger is good for the new high capacity cells. The 300mA on "slow charge" seems pretty low (0.11C for a 2700mAh cell). On the other side it has been recommended to avoid the fast charge mode of this charger.

Could some of the more knowledgeable members give some guidance.

Q1: Would the delta V algorithm for ending the charge be still reliable with the higher capacity cells at the 300mA slow charging current? I believe that higher capacity cells woud exhibit slower voltage changes (at same charging current).

Q2: I have always speculated that there may be a time limiter in the charge algorithm - to end the charge after so may hours even if no end of charge delta V condition was detected. If so - then the time limit might end charging of high capacity cells prematurely. (I may need to reset the charger for a second charge session to get a full charge).

Q3: Would the C401FS work well with the new low discharge cells. I noticed that if I discharge a Rayovac Hybrid below 0.95V the slow charge algorithm refuses to charge it (I have to switch to fast charge for a minute or so to get it started).

Any advice appreciated
Happy holidays
 

SilverFox

Silver Moderator,
Staff member
Joined
Jan 19, 2003
Messages
12,449
Location
Bellingham WA
Hello Stamat,

Q1: No... Yes... Maybe... :)
The battery manufacturers recommend a 0.5C charge rate for a strong end of charge signal. I would guess that with new cells you will have problems. However, once the cells are "broken in" and have a few cycles on them, it may work just fine.

Q2: You will have to ask Maha if there is a timer limit on this charger. I don't know. If you do try a second charge cycle, make sure you let the cells completely cool off before initiating it.

Q3: There should be no problems with the low self discharge cells.

How did you get a NiMh battery to drop to 0.95 volts open circuit? Did you not notice the light go dim? NiMh cells should always read above 1.0 volts open circuit. If you are running your batteries down beyond that, you can expect poor performance and poor cycle life from them. You may also find that your charger doesn't want to charge them back up.

Tom
 

stamat

Newly Enlightened
Joined
Oct 28, 2005
Messages
44
How to Run Batteries below 1.0 V :)

Thanks, SilverFox

When taking a walk in the woods my vision seems to adapt pretty well to slow light changes.
It could be hard to pinpoint the moment when the light *Starts* to dim, especially if your attention is focused elsewhere :)
I have a diffuser on the flashlight and the wide beam mixes with the ambient ligtht.
A cloud moving in the night sky can have as large effect on the amount of ambient light as the "full blast" of my tiny L1T.

On my Fenix L1T the impeding demise was more noticeable with Alkaline batteries.
When the high and the low stage gave the same light output - the battery was close to dead.
When I turned the light off and then it did not whant to turn on - the battery was practically dead.
Probably due to the low internal resistance of the NiMH the Fenix L1T always turns on and doesn't shut down untill the cell is sucked dry.
 

coppertrail

Enlightened
Joined
May 21, 2006
Messages
920
I've been charging my Sanyo 2700 Cells on a my C401FS, and haven't had any problems. I have observed that during the last 2 charging cycles, the middle 2 cells took quite a bit longer to finish the charge than the outside 2. Performance has seemed fine, I've not put them through a refresh cycle since this charger claims to condition them as it charger.

Tom - Thoughts on the middle cells taking longer to charge than the outside 2 cells?

Note: Since I purchased my Sanyo cells 6 mo. ago, I've only charged them with the 401FS on slow mode.
 
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