discussion NI MH Battery help

[Guest]

Hi folks maybe a daft question, but following an off the cuff comment from a club member i am starting to question my own judgement !!!!

but is there an ideal 'trickle' charge rate for Ni-mh cells ?

i dont need to fast charge these items - they are used in my model sub and get used about once or twice a month, they run the model for around 4 to 5 hours per charge - everything seems fine to me !

i currently use a 'multi lader' charger- with at output charge rate of 500ma- its not a peak detect type charger.....

so currently i am charging a 12 volt ( 10 x D cell ) 9000mah pack at 500ma for 22 hrs.....

everything seems fine but fellow club members seem to think the charge time is way too long.....??? i am not bothered about charging the cells quicker....But i want them to be 100% fully charged or as near as possible...

so am i fully charging them ?

is the charge rate sufficient ?-

should i 'warm' the cells up abit more by increasing the charge current !?

any thoughts ?

 

[Guest]

sounds ok to me for the number of cells there is

 

[Guest]

As long as you are below the ten hour rate you should not damage your Ni-mh cells at all.

Divide your pack by 10, and if your charge rate is below this figure you can in theory not cook your cells, even if you leave them on continuously. In your case 9000mah/10 = 900mah, so you could in theory charge at 900mah continuously and do no harm, so if you are charging at 500mah then 18 hours (9000/500=18) will give you a full charge.

This rule also applies to nicads, but these should be discharged to 1.1 volts per cell before charging otherwise they will gradually reduce their capacity due to 'memory', ie if you use a 6 volt pack (5 cells), discharge by putting something like a 12v car bulb across the contacts until your meter reads 5.5volts, then start to charge. Do NOT fully discharge nicads, they can go into what is called reverse polarity, another name is bin fodder.

In other words, charge away as you are.

 

[Guest]

cheers bogstandard, i did not think i was damaging the cells !

will continue as i am then - 500ma charge rate for 18-20 hrs.....

will tell the thursday fossils at the club ( the retired old boys ! ) that they are wrong !- makes me feel a whole lot better !!!

thanks everyone !