Suitable n Affordable Battery Meter for Rechargeable AA n AAA batteries.

I am presently using a SANWA YX-3200A battery measuring device. It is an old pc with 2 wires a Black and a Red ending in pins.

For ordinary disposable batteries especially new ones the meter can go half way to the Good Green side .

For Eneloop battery even though I recharge for 12 hours and subsequently charge for another 12 hours , the meter can only go on to just the beginning of the Good Green side .

Does it mean that my Battery Charger a Sanyo NC-MQRO1J/U with Output DC1.2V 460mA x 4 / 920mAx2 is inadequate ?


Kind advice appreciated on both the Battery Tester and the Battery Charger .


Thank you.

baguadao

Hi,

Take a look here: http://www.candlepowerforums.com/vb/showthread.php?332729-Battery-Tester, and maybe do some other searches.

A basic multimeter would be very affordable and serve you well. It will allow you to confirm if it's your tester, charger, and/or cells that are not performing properly.

Here's a good multimeter how-to: http://www.candlepowerforums.com/vb...do-you-use-a-multimeter&p=2727647#post2727647

You don't mention the size(s)/type(s) of Eneloops you're using or how they're performing, but if the only concern is how they show on the tester, and they are performing well, I would discontinue testing them with that tester and just charge them appropriately, being careful not to overcharge.

***Please note: I am not familiar with the tester or charger you are using.

Your battery tester is probably just a voltage reader meant for alkaline batteries. It will show full (green) when the battery has a voltage of 1.6v, which is what a new alkaline cell has for a resting voltage.

NiMH chemistry (Eneloops) have a "full" resting voltage that is about 1.35v - 1.40v. So, your battery tester is reading 1.4v and shows it is not full. That would be true if it was an alkaline cell, but it is wrong for a NiMH cell.

Don't use that battery tester for Eneloops. It gives incorrect results.

Instead, buy a cheap digital multimeter at your local hardware store for $10 or $20. Use it to measure the voltage on your Eneloops. Anything above 1.35v means it is fully charged. Anything below 1.20v means it is almost empty. Between 1.20v and 1.35v means it is partially discharged, with around 1.26v being about 50% discharged.

You can top up Eneloop batteries whenever you want. They have no "memory effect", so charging them when only partially discharged is perfectly fine. Just make sure you use a smart charger that will terminate the charge when they are full.

Charging your Eneloops for 24 hours, like you did, is not good for them. It will greatly reduce their lifespan.

Hey Walk,

Thanks for providing a much more complete and thorough response than I was able to- very helpful and informative to OP as well as me!

WalkIntoTheLight said:

[...] Instead, buy a cheap digital multimeter at your local hardware store for $10 or $20. Use it to measure the voltage on your Eneloops. Anything above 1.35v means it is fully charged. Anything below 1.20v means it is almost empty. Between 1.20v and 1.35v means it is partially discharged, with around 1.26v being about 50% discharged [...]

Click to expand...

For 1900mAh Eneloops 1.26V is not 50%. It's about 18% if it was resting after being discharged from full (red curve below) and 4% if it was resting after being charged from empty (green curve) The difference is due to hysteresis, i.e. the resting voltage depends on the recent history of (dis)charges.

Rather, 50% is about 1.30V if it's resting after being discharged from full (red) and 1.36V if resting after being charged from empty (green).

OTOH, 1.30V is not 50% but only 10% full if resting after being charged from empty, and 1.30V could be anywhere between 10% and 50% if the cell's recent history includes both (partial) charges and discharges. This large uncertainty due to hysteresis shows why it is difficult to estimate NiMh capacity based on (resting) voltage.

Due to this, a multimeter will yield only very coarse NiMh capacity estimates (e.g. above a 40% uncertainty at 1.30V) so will be of very limited value for such purposes. Similarly for devices that claim to be NiMh capacity testers (e.g. see the huge errors of the ZTS mini-MBT battery tester reported by HKJ)

The values above are from AACycler's data here - excerpted below. There the green curve shows the voltages obtained by 1.0A charging from empty to full in 100mAh steps, with voltages measured 24 hours after each incremental step. Similarly for a full 0.5A discharge on the red curve.

Gauss163 said:

Due to this, a multimeter will yield only very coarse NiMh capacity estimates (e.g. above a 40% uncertainty at 1.30V) so will be of very limited value for such purposes. Similarly for devices that claim to be NiMh capacity testers.

Click to expand...

This is interesting stuff!

Would the procedure described here: http://www.candlepowerforums.com/vb...do-you-use-a-multimeter&p=2727647#post2727647 of using a resistor along with a multimeter result in an accurate measurement of NiMh % of charge?

Gauss163 said:

For 1900mAh Eneloops 1.26V is not 50%. It's about 18% if it was resting after being discharged from full (red curve below) and 4% if it was resting after being charged from empty (green curve) The difference is due to hysteresis, i.e. the resting voltage depends on the recent history of (dis)charges.

Click to expand...

Agreed, it is more complex than what I indicated. Still, based on typical usage, I find 1.26v is about 50% drained. Maybe a bit more, but still nowhere near 82% drained. That's for low-discharge usage. When used in a high-drain application, like a Zebralight SC5 on max, you could be right that it's much more drained. But, that's just based on some rough measurements I did years ago. I'm not sure what kind of usage your graphs are based on, but they probably apply to higher discharge than what I typically use. They're interesting, though.

Anyway, the main point is that you can charge up Eneloops whenever you want. I typically top mine up after every use if I use a light for more than a few minutes. There's no advantage to leaving them partially discharged. If I use a light for an hour, it might still be 80% charged, but why not top it up and have it 100% charged in case you need it for longer?