Sanyo 2500's from Costco 1000mah at 2amp Discharge

Something has to be wrong here. Just picked up a 6 pack of the Sanyo branded 2500Mah NiMH cells with the 1 hour charger and 2, 900mah AAA's to boot. Brought them home....threw them in a 6aa-2d holder and charged then up at 1 amp charge rate. Then I dishcharged them at 1amp and only got 1100mah...............recharged them at 1amp again and discharged at .5 amp and got 1300mah. All cells where measuring 1.38 volts fully charged. Whats going on here???


Mac

cmacclel said:

Something has to be wrog here. Just picked up a 6 pack of the Sanyo branded 2500Mah NiMH cells with the 1 hour charger and 2, 900mah AAA's to boot. Brought them home....threw them in a 6aa-2d holder and charged then up at 1 amp charge rate. Then I dishcharged them at 1amp and only got 1100mah...............recharged them at 1amp again and discharged at .5 amp and got 1300mah. All cells where measuring 1.38 volts fully charged. Whats going on here???


Mac

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Mac:

It's better to use C/10 or 250ma charge rate in your case for 14-16 hrs. on new cells.

I've never seen or used a 6AA>2 "D" holder but that means three cells in parallel and then in series or a 2S3P pack. Maybe not the best way for a first time charge at 1A. What charger did you use for that? Did you happen to compare the voltage on the cells?

The charger that came with them was a 1 hour charger. so I figured 1amp was going easy on them The Charger used was the Triton. Each cell measured 1.38v full charged. The 6aa-2d holder is series 6s1p.


Mac

Do a few more charge/discharge cycles?

I have noticed different readings with Sanyos when differing the load and charge rates.

Did a conditioning cycle on my LaCrosse BC900 and my Sanyo Industrial 1700mAH batteries returned a 1790 to 1815mAH capacity at 700mA charge / 350mA discharge. These are the batteries used in my 8AA to 2D adapter to fit my stock Mag 2D.

Then the evil Cadex 7400ER battery analyzer/conditioner equipment showed up at work. It is a very expen$$$$ive analyzer to check medical batteries at the hospital. Went through the programming and set it for C/3 (560mA discharge, 560mA charge rate, 0.8V discharge cutoff and other various settings) It went through two cycles of charge discharge (plus some reverse conditioning it does) gave my results at 95% and 95%.

The differences between the two readings from two analyzers on the same analyzers has to do with a few things. Obviously the Cadex costs 74 times more than the LaCrosse and that has something to do with it. The LaCrosse checked each cell and ran the test gently at 700mA charge/350A discharge VS the Cadex 560mA charge / 560mA discharge. The Cadex also ran my batteries as a pack so the weakest cell is the rating.

This week I will take a Sanyo Industrial 2300mAH NiMH AA cell and set it for 700mA charge rate, 1.7 amp discharge rate with a 1.1V cutoff. It will give me the capacity and time it will run meeting those parameters. The oddball cutoff is to see how long the cell will run a MillerMods Fenix L1P (on order) My wildest hope is a runtime of 60 minutes.

I get all sorts of weird readings when using new batteries on the LaCrosse BC900. Took some Sony 2500's and ran them through a test cycle. They gave readings of 1200 to 1800mAH at a 700/350 rate. Then conditioned them for at least five cycles with readings of 2450 to 2490mAH. Using brand new batteries in a pack would give you readings of the lowest performing battery. Hammering them at 2 amps brand new will give you really poor performance (as you said) I would give them 5 cycles at 1000mA charge/500mA discharge before testing them again at 2 amps.

Hello Mac,

Send them to BenHead for a check up on the Cadex...

Another thing to consider, my NiMh cells (with the exception of the Eneloop cells) come off the charger at about 1.45 volts (the Eneloop come off at just over 1.5 volts). If your cells are coming off at 1.38 volts, I don't think they are fully charged.

A new cell will often give a false end of charge signal. That is why the forming charge of 0.1C for 16 hours should be used for the first charge on a new cell. You may see an increase in capacity over the next 5-10 cycles, but after that things should settle down to a pretty constant capacity.

Tom

SilverFox said:

Hello Mac,

Send them to BenHead for a check up on the Cadex...

Another thing to consider, my NiMh cells (with the exception of the Eneloop cells) come off the charger at about 1.45 volts (the Eneloop come off at just over 1.5 volts). If your cells are coming off at 1.38 volts, I don't think they are fully charged.

A new cell will often give a false end of charge signal. That is why the forming charge of 0.1C for 16 hours should be used for the first charge on a new cell. You may see an increase in capacity over the next 5-10 cycles, but after that things should settle down to a pretty constant capacity.

Tom

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Sure,
Send them to me although it might take over a month to get it here, tested and returned across the Atlantic. Tom keeps teasing us with the Eneloops 4A discharge and higher voltage capabilities. The Cadex 7400ER with printer is pretty cool although we don't have the computer interface yet.

To help Tom with his testing of the new Sanyo Eneloop AA and AAA cells, I volunteer to test them on the Cadex 7400ER analyzer/conditioner. Send me about 2 dozen AA cells and maybe... half a dozen AAA Eneloops and I will give results after 5 cycles of conditioning, .25A, .50A, 1.0A, 2.0A, 4.0A, 5.0A and 10A discharge rates. I'll even send half of them back with cool stickers stating their capacity. Think of it COOL STICKERS! Anything for Tom and CPF... I would need the spare dozen of AA Eneloops to do long term testing for the next year or two... for scientific reasons... I'll be expecting a PM asking for my shipping address, Tom!

Discharged them at .5 amps recharged at .3 amps still 1000mah capacity Looks like there going back to Costco!

Mac

Could the combination of new cells and different Delta V settings cause this? As I picked up my Sanyo pack when I was out of town, I charged them up first in the included charger, then ran them down in my Mag85. The rest of my charges have been from my Triton at 1A or so and I'm getting 2300+ per cycle.

cmacclel said:

Something has to be wrong here. Just picked up a 6 pack of the Sanyo branded 2500Mah NiMH cells with the 1 hour charger and 2, 900mah AAA's to boot. Brought them home....threw them in a 6aa-2d holder and charged then up at 1 amp charge rate. Then I dishcharged them at 1amp and only got 1100mah...............recharged them at 1amp again and discharged at .5 amp and got 1300mah. All cells where measuring 1.38 volts fully charged. Whats going on here???


Mac

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Hi,

I'm not a battery expert but I know that capacity ratings for rechargeable cells are usually determined at a specific discharge rate (probably much lower than what you expect, making capacity ratings somewhat meaningless since I doubt every manufacturer follows the same standard).

NiMh cells have rather high internal resistance and at higher discharge rates the I²R losses increase, meaning more wasted energy (less capacity). That is one possible explanation. The trick would be to discharge them at the manufacturers rate used to determine capacity and then see if you have a problem. Even still, you're assuming a constant current load which may or may not be the case.

I would check the datasheets for the cells or see if you can get in touch with an application engineer for Sanyo who can give you more detailed info on the ratings. Good luck.

Nickel

Did anyone know you can limit the MAH input into a NiMH battery with the triton??? I didn't !!!! Mine was set to MAX 1000mah. I guess that explains my problem . I've been using this charger for over a year for Li-Poly's and never knew there was such a setting. My tri-lux may be much brighter with a full charge!!

Does anyone know why this option even exists??? Why would you wanted to only put a certain amount of power into a cell??


Mac

So the charger won't destroy your cells if it fails to detect end of charge properly. It's a backup termination method

IIRC it's more there for NiMH and maybe NiCD cells. mainly becuase if you overcharge NiMH cell it's life will be affected very quickly.