products for measuring lithium battery capacity?

[Chendy]

Hi gang,

Are there any reasonable priced products to measure the mAh capacity of Lithium batteries? Happy to fully discharge. I want to verify the stated capacity of Chinese batteries.

Failing that, whats the simplest roll-your-own solution?

I was thinking logging battery voltage, and voltage across a large-resistor, then using ohms law. Or I think people prefer using a constant current load, and measuring time for battery to get below a certain voltage.

many thanks

[MosherIV]

Raw battery or with safety/charger circuit ?

Many LiIon/LiPo chargers can do a charge/discharge cycle and tell you the capacity. I think these work for both raw and built in circuits.

The other thing I have seen are the USB power monitors, they can measure both the volt and amps and then give you a charge capacity. These will only work for USB battery banks.

[Skashkash]

A Chinese tester for Chinese batteries?

I found this cheap gizmo on ebay to be surprisingly accurate for battery capacity testing.
Also just really useful as a programmable load.

http://www.ebay.com/itm/271941351786

Note, I don't think the battery holder is included, but can be acquired elsewhere.

[HKJ]

There are many products.
A charger like Opus BT-3100 is acceptable for it, another charger is LiitoKala Engineer Lii-500.
The best charger is SkyRC MC3000, it can be calibrated and is fairly precise.
Westmountainradio sells a CBA for the it.
My favorite is to use an electronic load (Itech).
You can also find a couple of cheap Chinese loads, I have tested one here: http://lygte-info.dk/review/Review%20Electronic%20load%2060W%20UK.html

[Chendy]

@MosherIV not sure, finding out if raw or not, thanks
@Skashkash thanks
@HKJ thanks, I think Im will get the SKYRC MC3000. It even outputs data as CSV apparently. Also your website is excellent thanks

[DBecker]

I use the under-$5 capacity testers that use an external resistor.

1.5~12v Battery Capacity Meter discharge Tester 3.7v 18650 lithium lead-acid

They start by reading the initial voltage to guess the end of discharge voltage.  You can modify the termination voltage at that point.  They then switch on the load resistor and measure the current, displaying the voltage, current and mAH in sequence.

I have since added alternate resistors and a variable load with fan

15W 3.7-13V Industrial Electronic Load Resistor USB Discharge Battery Tester

This results in a pretty flexible testing system, but isn't as convenient as having a single-purpose charge-discharge battery analyzer.
 

[edavid]

I use the under-$5 capacity testers that use an external resistor.

1.5~12v Battery Capacity Meter discharge Tester 3.7v 18650 lithium lead-acid

They start by reading the initial voltage to guess the end of discharge voltage.  You can modify the termination voltage at that point.  They then switch on the load resistor and measure the current, displaying the voltage, current and mAH in sequence.

This works great for me, since I have a power decade box to use as a load.

They only cost $3.70 on AliExpress: https://www.aliexpress.com/item/1-2-12V-battery-capacity-tester-external-load-discharge-capacity-test-18650-New-Design/32701874526.html

Here's a helpful English description: https://syonyk.blogspot.com/2015/10/zb2l3-v20-zhiyu-battery-tester.html

[RoGeorge]

whats the simplest roll-your-own solution?

For charging only, the battery's phone. For charging and logging, a Rigol DP832 Power Source with a small SCPI script for logging, and an improvised connector for the battery.

For discharging, two 15ohm/8W resistors in parallel and a Metrix mtx3293 DMM that can log both the discharging current and the battery voltage simultaneous. For very old batteries, a thick old pot was used against possible fire/explosion damage.

As a fun tale, one Nokia battery that was tested was from a phone lost on a very circulated road about 10 years ago, after many cars drove over the phone. There are dents and bending signs all over the battery. The phone was damaged even worst. That battery was forgotten until a few weeks ago, when it was measured. The battery was still about 1/4 charged after all that time. With all the dents and its very old age, that battery is still working at about 70% of its original capacity.

[DBecker]

I suggest *not* using only a resistor to discharge.  It takes hours (typically you are targeting either 10 hours or 20 hours), and it's far too easy to forget.  An over-discharged lithium cell is permanently damaged and dangerous.

The cheap discharge testers will disconnect the load when the termination voltage is reached. 

[RoGeorge]

ALL Li-ion batteries have a protection circuit for overcharge/overdischarge/shortcircuit protection embedded in their body, so there is no way to destroy it by overdischarging.

If you look in the charts above, you will see a voltage drop to zero after a few hours (where the blue cross is). That is the point where the protection circuit triggered, at 2.2726V for this particular chart. Once it is triggered, the battery stays disconnected.

LATER EDIT:
Seems like this claim is wrong, so I take it back. Sorry for that.

[HKJ]

ALL Li-ion batteries have a protection circuit for overcharge/overdischarge/shortcircuit protection embedded in their body, so there is no way to destroy it by overdischarging.

NO

[RoGeorge]

My bad, I was talking about phone batteries.
Are there any phones with the protection circuit outside the battery?

[HKJ]

My bad, I was talking about phone batteries.
Are there any phones with the protection circuit outside the battery?

I do not know that, but round batteries are often sold without protection and LiIon packs for hobby use is also sold without protection.

[RoGeorge]

Indeed, round cells like 18650 replacements for laptop battery packs don't have protection circuit inside them. There is only one circuit in the battery pack case that do all the protection and load balancing.

Round cells similar with 18650 but for hobby use, should also have a protection embedded, otherwise they will be a too big fire hazard to be sold for public use. Usually it is specified by the seller if the round cells have the protection embedded.

[HKJ]

Round cells similar with 18650 but for hobby use, should also have a protection embedded, otherwise they will be a too big fire hazard to be sold for public use. Usually it is specified by the seller if the round cells have the protection embedded.

Many vapers buy without protection, because they need very high current.
For smaller round cells there can be a problem with space for protection.

I have not counted how many with and without protection I have tested, but there are many of both types:
http://lygte-info.dk/review/batteries2012/CommonSmallIndividualTest%20UK.html
http://lygte-info.dk/review/batteries2012/Common18650IndividualTest%20UK.html
http://lygte-info.dk/review/batteries2012/Common26650IndividualTest%20UK.html

[DBecker]

My bad, I was talking about phone batteries.
Are there any phones with the protection circuit outside the battery?

Yes, absolutely.  Most replaceable phone and camera batteries have protection circuits, but not all.

Back in the flip phone era it became common for original batteries to have internal protection circuits, and for the phone to rely on them in certain conditions.  Some sleazy aftermarket batteries continued their previous practice of omitting them.  Hilarity resulted.  (By "hilarity" I mean "pants on fire" and "not fire, just venting with flames".)

[RoGeorge]

OK. It looks like I was wrong, sorry about that.

I take my words back about the claim that all Li-ion batteries have a protection circuit embedded.

[ez24]

Aliexpress version

https://www.aliexpress.com/item/Constant-current-electronic-load-Discharge-9-99A-60W-30V-battery-capacity-tester-Free-shipping-with-tracking/32546800281.html?spm=2114.01010208.3.1.d18Wtk&ws_ab_test=searchweb0_0,searchweb201602_4_10065_10068_10000007_10084_10083_10080_10082_10081_10060_10061_10062_10056_10055_10037_10054_10059_10032_10099_10078_10079_10077_10073_10097_10100_10096_10070_423_10052_10050_424_10051,searchweb201603_9&btsid=33f6be78-d770-48a5-8627-33a366b44ec9