When are Eneloops Ready to Charge?

I've been using two AA Eneloops in my Romisen RC-N3 Q5 for the last week or so. The light has been dimming and flickering, so I suspect the batteries are ready for a charge. Is is necessary to completely discharge the cells, or can I simply charge them now? Will charging a partially discharged cell (say, 30% charge remaining) reduce its life?

Hello BlueBirdTS,

NiMh cells do benefit from a complete discharge every once in a while, but you don't need to do this with every discharge cycle.

Charge them up and use them.

Tom

The answers to this set of questions are difficult to search for on this forum.

For NiMh cells:
If my charger says 500mA output, can I charge 2000mAh batteries for 4 hours and assume they are fully charged?
If I use a charger that says 400mA output, do I charge the same cells for 5 hours to get a complete charge?
How can I be certain that 2900mAh C cells are charged if I follow the above type of assumptions?

Many thanks,

being such a slow charger, the -dV may not terminate. it is suggested that you purchase a GOOD charger with about a 1A charging rate(MAHA)

Lucero said:

The answers to this set of questions are difficult to search for on this forum.

For NiMh cells:
If my charger says 500mA output, can I charge 2000mAh batteries for 4 hours and assume they are fully charged?
If I use a charger that says 400mA output, do I charge the same cells for 5 hours to get a complete charge?
How can I be certain that 2900mAh C cells are charged if I follow the above type of assumptions?

Click to expand...

Most chargers that charge at 400 or 500 mA have an automatic end of charge detection. You can simply put the batteries on charge and wait until the charger says done.

However, if for any reason you are timing manually, you need to put in a little more than the rated capacity due to losses. For instance, Sanyo say about Eneloops that the nominal capacity is 2000 mAh and a fast charge is 2000 mA for 1.1 hours. From this you could assume that at 500 mA you would charge for 4.4 hours giving 10% extra.

Using charge time assumes the batteries start out fully discharged, otherwise they will be overcharged. Normally it is better to use the charger's automatic end of charge detection and just use the timings as a safety backup.

Thanks for the responses! I see I still have quite a bit to learn.

I bought a Eneloop pack that included a Sanyo Eneloop brand charger. The manual says to charge them for 10 hours but it says the charger only shuts off automatically after 16 hours? Does this charger not have an automatic shutoff when the maximum capacity is reached?

eneloops give more realistic capacity ratings than most NiMHs I've seen....being that it rates their cells to be within a certain capacity range. ~2000mah

That being said, if your planning to time your charges, regard that not all batteries [even from the same batch] live up to this capacity. Some are higher while others may be lower...especially after many deep cycles