Battery charging

[Baz84]

Hi all. New to this so have a quick question.

I have a 8.6v 1600 mah nimh battery and my charger info says it will take 14 hours to fully charge it.

Not one for leaving it charge un attended and don't fancy sitting there watching it for 14 hours, can I charge it at work for about 8 hours then bring it home and carry on there for the remainder of the time?

I know there's no memory issue on these types of battery's, so just wondering if that would work?

 

[david0512]

That's perfectly fine if you don't want to leave it unattended and I see no reason why it should cause any problems. What I've done to avoid that problem is get two 8.4v 1150 mah batteries and chargers, so I can charge them both at the same time and it takes less time to charge them.

 

[RR01]

Check the charge rate of the charger you already have. For a 14 hour charge of a 1600mAh battery the charge rate will be around 170mA. If it's more or less than this then the number of hours changes. The basic formula for working out how long to charge a depleted battery is: mAh of battery x 1.5 divided by mA of charger = hours to charge, so 1600mAh x 1.5 / 170mA = 14.1 hours.

You need to reduce the charge time if the battery is only partially discharged. The easiest way to work it out is to check the voltage of the battery. A fully charged 8.4V NihM will show around 9.8 - 10.1V. Discharged to around 9.2V would knock about 3.-4 hours off the charge time, but down to 8V would need the whole 14 hours.

Nihms rarely cause a problem if left on charge. I leave mine charging overnight and check them when I get up, although I do use a timer switch if I want to stop the charge early. It's really only Lipos that can have issues with charging, but Lipos usually charge very quickly compared to NihM & Ni-cads.

 

[Baz84]

Lovely. Thanks for the help.

I have ordered myself another battery and a smart charger with indicator lights so can't go wrong.

My charger says its 150 output for 8 cells so hope the new one puts out more!!!

 

[AK47frizzle]

i'd suggest a better charger with more output for faster charging.

My charger output is 250 mA

I use the same charger for 8.4v and 9.6v batteries.

 

[Richard65]

I may be wrong but mI seem to remember reading that fast chargers can wear out batteries quicker than if you use a slower charger - just can't find the page now!