On 30/01/13 23:22, Wayne Stallwood wrote:

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.

Many thanks. Shall be in N&NUH for a couple of days, and I might get tired of reading hard copy. I have dozens (no exaggeration) of NiCad and NiMH cells - AAA; AA; C; D; PP3, and we'll forget about the old phone batteries, then... Of course, I meant Li not Ni -- Tony

On 31/01/13 10:54, Chris Green wrote:

There are chips (can't remember the manufacturer, there is one major specialist) specifically for NiMh and NiCd chargers which detect the delta-V fully charged voltage step from the battery. There are also chips specially designed for charging LiIon of course.

'Intelligent' chargers (i.e. ones which detect delta-V) for NiMh and NiCD are so cheap nowadays that it's almost certainly not worth DIY except for one's own satisfaction.

Thanks - I had in the back of my mind something larger and more comprehensive than the usual 4-cell charger - something like 16 bays. Ideally each one would be switchable to take all single cell types. Somewhere, I have the circuit diagram for a dry cell depolariser too, hence the 'all', so each bay could be switched to three modes. But in the meantime, my enquiry was just so I could know how to set the timer for say, 4 NiMH cells - I have 2,000 maH, 1,3000 maH, 1000 maH in AA NiMH cells alone, and I have AAA, C and D cells as well. As an aside, I remember the days when some people still took their wireless accumulator in to the local garage, electrician or in my memory, cycle shop, to get it recharged. I wish I still had my old (mains supplied) walnut veneered wireless, which ended its days upside-down (sagging filament in one of the valves) in my workshop. -- Tony

On 31/01/13 12:24, Chris Green wrote:

On Thu, Jan 31, 2013 at 11:30:20AM +0000, Anthony Anson wrote:

...

On 31/01/13 10:54, Chris Green wrote:

/snip/

...

Thanks - I had in the back of my mind something larger and more comprehensive than the usual 4-cell charger - something like 16 bays.

I have a ten bay one which was very reasonably priced, quite a few people sell them, mine came from CPC.

I also have a 4 x anything bay charger for the few C and D cells I have, from 7dayshop.

I'd better spend some of this upcoming forced idleness in using that wifi then. At home, I'm restricted to a GPRS connection, and 'slow' is a wild and optimistic exaggeration. -- Tony

On Thu, Jan 31, 2013 at 11:21 AM, James Freer <jessejazza3.uk@gmail.com> wrote:

On Wed, Jan 30, 2013 at 11:22 PM, Wayne Stallwood <ALUGlist@digimatic.co.uk> wrote:

...

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.

...

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

I use NiCd and NiMH quite a lot.

The following seems to comply with the recommended times given by Uniross and others.

Charger rate = 150mA Battery say = 1800 mAH add 40 % for losses

1800 / 150 = 12 hours

allow for loses 1.4 x 12 = 16.8 hrs Compare that with info on the charger and it'll correspond pretty well. I have seen losses quoted for NiMH at 50% - i think that's a bit much.

I think 35% is a better bet to use. My batteries have all lasted a good while - i've got two D's that have been going for 20 years... and they were a cheap make! The AA don't last anything like as well.

james

as for timing i just use a mechanical 24/7 timer