On 29/01/13 00:13, Anthony Anson wrote:
I have several chargers with different rates of delivery: has anyone any idea where I should start looking for data relating to recharging NiCad and Nion batteries?
Like:
Output of charger Time to charge per mA capacity of each type of battery
Or a way to calculate time, allowing for (expected) losses in the process.
No, I'mnot being (very) lazy. On this GPRS connection a thorough websearch is time-consuming, and, at £15 per Gig. expensive.
Nion ??
Li-ion batteries you have to be very very careful with...there isn't a workable single phase charge model Constant Current or Constant Voltage that is safe with these. Overcharging can result in fire and undercharging will result in cell damage. You can't safely charge Li-ion without a smart charger..don't even try :)
NiCd and NiMH are pretty straightforward...Constant Current charging model. For CC charge models the charge rate is described as a fraction of the cell capacity so 1C is a charge rate in milliamps equal to the cell capacity in mAh
Trickle charge can in theory be applied indefinitely by a constant current circuit and is usually in the order of something like C/12-14 (so 14 hour charge on a 1800mAh pack, current regulated at say 150mA). In reality it will shorten cell life if you apply it indefinitely. "Dumb" CC charge circuits usually just charge at the trickle charge rate and hope that at some point you remember to unplug them.
Smart chargers will typically charge at up to 1C but usually with some delta-v monitoring going on to detect when the pack is fully charged or at the very least some form of cutoff..because overcharging at 1C will result in cell damage and overheating..maybe even venting/rupture of the cells.
Charging losses vary with charge rate, discharge level and environmental conditions. You need a good spec sheet with a pretty graph. From memory I think a typical NiMH cell being charged at 1C absorbs about 85% of the energy you put into it
The spec sheets for the batteries when available can be a great source of info.
Lead Acid (Pb) chargers use the Constant Voltage model..don't use those on a NiMH/NiCd battery or vice versa
To read up on it properly http://batteryuniversity.com/ isn't a bad place to start.