4500mah nimh farting!

[pmath]

Sorry if it's crude but it is the best way to explain the noise one cell in a set of three new 4500mah Titanium NiMH cells made after having been charging for 4 or 5 hours on my Ansmann ACS charger.

On inspection one end of the cell has leaked enough to discolour the cardboard (?) end and there is slight discoloration along the seam in the case.

Any clues as to why this may have happened?

The only thing I wondered was if I have had the cells too long before actually charging them for the first time?

Your comments appreciated as ever,

Peter

 

[Mr Happy]

There are a few things you have not mentioned.

What charge rate were you using?

How warm was the cell at the time of venting?

What was the previous history of the cells? (When purchased, when last charged, when last used, etc...)

 

[Sgt. LED]

Batteries are not recharged by feeding them beans. Stop it.

 

[lctorana]

What size batteries are we talking here? C?

 

[pmath]

Sgt Led - we know that beanz meanz...

Ictorana - they are c's

I have quite a few of them stock up for about 18 months, so I'm thinking I should charge them singly using a clamp so as to test them before building packs.

Peter

 

[SilverFox]

Hello Peter,

Your cells are venting. Your charger missed the end of charge termination signal. If the cells have been in storage for a period of time, they may recover by running a few charge/discharge cycles on them. However, a cell that vents will have less capacity and reduced performance, so you should mark it and keep an eye on it. It may be OK for awhile, but eventually it will degrade.

Tom

 

[pmath]

Thanks very much for your answer Tom. I've now found three in my batch of 50 cells. I've notice that my Ansman is highly inconsistent in time to charge.

May need a better charger I suspect.

Peter

 

[LuxLuthor]

Pull my finger.

 

[mdocod]

The charger may not really be at fault.... leaving cells in rest for long periods of time can change their behavior on a subsequent charge. A few 0.1C charge rate cycles (~14-16 hours charging time) would be ideal to help get them back to somewhat normal....

One problem with owning a LOT of NIMH cells is that unless you are exercising them at least semi-regularly, they are going to develop problems in storage. LSD type NIMH chemistry seems to negate some of this effect and allow for a greater deal or neglect without harm.