Unusual questions about charging batteries

Batteries and Chargers Rechargeable Batteries
1

First, when my batteries start getting hot in the charger, around 105F as they are charging, I put an ice pack on them wrapped in a towel, which cools them off, is that interfering with some chemical process inside the battery, that is needed as part of the charging process? Does your answer apply to all types of batteries?

Second, what does it do to my 2000mAh batteries, if I tell my Maha C9000, that they are actually 2100mAh (or 2200mAh) batteries? Is that a way to help tired batteries?

Third, I don’t need to charge my NIMH batteries but once or twice a year generally, and I keep most of them new and unused and stored, would it be better for the batteries, for me to discharge and charge all of them, 3 or 4 times a year? Am I hurting rather than helping by not putting them through occasional cycles?

2

About your first point. I don’t think you really need to worry about the heat unless it’s a really shifty charger. Normally I would just stick the batteries in and let it charge to full unattended.

I don’t really understand your second point.

Third, if you’re storing li-ions, keet the charge at about 30%

3

I added that question three was about NIMH, are they better lying dormant, or better to do a break-in, or discharge/charge cycle a couple of times a year, or annually?

Question two meant, when your Maha C9000 asks you to enter the mAh for a battery break-in, what does your battery gain, or lose, by entering a higher mAh than it actually is?

4

If you’re using a Maha C9000 then you must be talking about NiMH batteries rather than Lithium Ion. In general I don’t believe there is any value in charging and discharging them 3 or 4 times year. Just charge them up when they need charging and let the charger figure out the capacity. If the cells are not giving you the mAh you are expecting, I believe that particular charger has a Refresh & Analyze feature you could try using.

5

Aha I have no idea when it comes to NiMh.
as for qn2, my charger doesn’t asks for battery capacity, it just chargers lol

6

Follow the directions in the manual: http://www.mahaenergy.com/content/manual_mhc9000.pdf

More info in the FAQ: http://www.mahaenergy.com/FAQ-C9000/

1. You should reduce the charging current to avoid the temperature rise. That is better than extra cooling. But stay within the recommended currents 0.33C - 1C. However the charger will detect dangerous temperature rise and temporarily halt the charging.

2. There is nothing to gain from "lying" about the capacity. Possibly it may even be harmful. I think the capacity is mainly used when running the break in program, and then the cells are gently "overcharged" using a low current. If you have lied that may lead to more than a "gentle" overcharge.

3. Just top the cells up now and then. If it is LSD/Eneloop perhaps every 6-12 months year or so. Ordinary NiMH perhaps every 1-2 months. No need to do a full charge/discharge/charge cycle often if you don't intend to use the cells, that will only cause extra wear. However if you intend to use the cells after extended storage they will get significantly higher capacity if you give them one or two refresh cycles first. Perhaps 10% or more.

The life of the NiMH cells is reduced by the number of charged/discharge cycles, overheating and chemical change under storage. NiMH cells age the slowest if you store them fully charged.

In the manual it is recommended to refresh the cells every 10 cycles and break in every 30 cycles. But that depends on how fast you rotate your cells. I refresh all my cells once a year, and only break in new cells. And I rotate my NiMH cells so they get used at least once every year.

Try to spread the wear evenly over all your LSD/Eneloop NiMH cells so they all get used at least once or twice every year, that way they are refreshed in use. Try to store them topped up. Discard cells if they don't regain usable capacity after say 3-4 refresh cycles.

For Li-ion it is better to put the wear on as few cells as possible, just rotatat the cells needed for the flashlights that are in use. Store unused spare cells cool and dry and partially discharged. At 3.6-3-7 volts. When one individual cell is too degraded to be usable, discard it and put another in circulation instead.

Li-ion cells age faster if you store them topped up or discharged, and slowest if you store them partially discharged at 3.6-3.7 volts.