how to calculate nimh charging time?

[detach8]

hello guys... i was wondering how to calculate charging time.. i don't seem to be able to get full capacity out of my nimh batteries...

batteries rated capacity 650mah, charger 300mah

I did a rough calculation and it goes around 2 hours plus. so long meh?

[detach8]

latest update.. the charger is 12v and my batt is 8.4v... does the voltage matter? if taking voltage into consideration, it would take around 1h50mns to charge the battery. Am i correct?

sidetrack: i fell asleep left my battery charging overnight last night and forgot to unplug the charger only to wake up finding my battery super hot! it went on charging for about 4hrs. i don't know if i damaged my charger or battery. sigh..

[aerobird]

hello guys... i was wondering how to calculate charging time.. i don't seem to be able to get full capacity out of my nimh batteries...

batteries rated capacity 650mah, charger 300mah

I did a rough calculation and it goes around 2 hours plus. so long meh?

Want to buy a Tahmazo Charger, I letting go mine for just $80/- you won't get overcharged batteries.

Anyway, to answer your question. If your battery is 650mah, and your charger is only 300mah, then your charger will charge at a rate of 300mA within 1hr. It will take just over 2hrs to fully charge your battery.

If you have a 650mA charger, then it will take 1hr. If you have a 1Amp charger, then it will take 1/2 hr to charge and so on.

As for forgetting to unplug your charger, depends on what charger you got. If your charger cannot sense full charged condition, then you would have overcharged your batteries. Luckily that's a NiMH. If it was a LiPO, you would have burned down your house. Your NiMH would still be usable but you might have shorten the life somewhat.

[slackerz]

As for forgetting to unplug your charger, depends on what charger you got. If your charger cannot sense full charged condition, then you would have overcharged your batteries. Luckily that's a NiMH. If it was a LiPO, you would have burned down your house. Your NiMH would still be usable but you might have shorten the life somewhat.

shorten the life? i'm surprised it did not kill the batt! I'd expect the capacity to drop to around 50-80% depending on how much you overcharged.

[peary]

the last time i over charged nimh batt pack. a few of the cells die.

[aerobird]

Really depends.

If NiMH is overcharged at 1/10 C, it would not spoil the battery. But using Rapid chargers and overcharging using them will. However, in my experience using NiMH, they are very hardy. Unless you overcharge them to an extreme that they are so hot which you cannot even hold it, they will normally take quite a fair bit of abuse.

Don't try it with LiPos though..