Laptop cell spec

[awol]

I got given a dead samsung laptop battery.
There were 6cells, spec is 18650-22fu and joined in 3pairs and each pair at 3.3v.
I charged the pairs with my bc168 to 4.2v and they held there a few days, so I discharged them at 1a down to 3.2v
This took 6 hours which made me guess each cell is 3000mah each however having just researched online it turns out the cells are rated 2200mah.
So at what volts do the manufactures consider them flat, or is the specified 'mah' rated with a 2200ma load lasting 1hour?

 

[Deleted member 4366]

3v is flat, but there's not a lot of charge between 3.3v and 3v, so your test would show a good representation of their capacity as long as your 1A for the current was accurate. If you use a fixed resistance, the current will drop significantly as the battery goes down. Say you set it to 1A at 4.2v. At 3.2v, it would only be 0.76A. Average would be 0.88A.

 

[awol]

If you use a fixed resistance, the current will drop significantly as the battery goes down..

Does that quote mean a constant 1a? I am using my BC168 discharge feature which says 1.0a constantly so is that a fixed resistance?

 

[Deleted member 4366]

Good question. It probably is constant current.

 

[Alan Quay]

The capacity quoted will be for a certain discharge rate. 1C would be a sensible rate to test them at.

If you repeat the test at about 2.2 amps I guess you will get a different resulting mAh rating.

 

[awol]

The capacity quoted will be for a certain discharge rate. 1C would be a sensible rate to test them at.

If you repeat the test at about 2.2 amps I guess you will get a different resulting mAh rating.

Ah Mike, this ties in nicely with the idea you give me last night about connecting 4way plugs to a battery to get more amp discharge. I am thinking (in line) battery to watt meter to 4way ext to kettle/tumble dryer/bulbs/fans whatever until wattmeter shows enough amps and monitor volts every 15mins.
My only concern with this idea is, because I am connecting 240v equipment to low volts battery could that damage the appliances?

 

[Alan Quay]

As long as the appliances are simple things with no electronics, it'll be fine. Cheap kettles, electric heaters, hairdryers etc.

Your watt meter will integrate the result from volt x amps, so no need to measure every 15 minutes.

It's not the most elegant way to do things, but it is easy and cost neutral.

Others have used a heating element from a fire, with a crocodile clip. This can then be slid along to create the right load, much like a rheostat.

Or, you could use the discharge feature on a Lipo charger.....

 

[awol]

Or, you could use the discharge feature on a Lipo charger.....

Mine only goes to 1.0a so may have some fun with the above idea when I get time.