So i have a Rigol Digital load and i'm trying to load test a Li-ion battery to calculate how many 'mAh' the battery really is. The battery claims 4.2v and 4500 mAh. I need to know how much load to actually put on the battery and when to stop the load. Can anyone give me some tips?
The data sheet of a good quality battery will give
you the test information.
what brand is the battery?
The battery capacity depends on the load you apply, so it makes sense to use the intended load.
Don't let the battery voltage drop below about 3.0V or it will be destroyed.
If you want to see close to the nominal capacity the convention for Li-ion batteries is to discharge at 0.5C from fully charged (4.2V) to 3V. But since the capacity is heavily influenced by the load as said it makes sense to test at the currents you expect to be using.
Steve
jremington:
The battery capacity depends on the load you apply, so it makes sense to use the intended load.Don't let the battery voltage drop below about 3.0V or it will be destroyed.
Yea i have had a few of them go bad trying to drain the down to nothing. They are UltraFire YF 18650 4800-mAh.
I have been having trouble locating a datasheet for them, this is what they look like,
slipstick:
If you want to see close to the nominal capacity the convention for Li-ion batteries is to discharge at 0.5C from fully charged (4.2V) to 3V. But since the capacity is heavily influenced by the load as said it makes sense to test at the currents you expect to be using.Steve
The load that will be on the batteries is 0.0700 amps. When i load them down to .7 amps i get about 1250mAh until 3v. I was just curious how i'm actually suppose to test them. The digital load im using can do constant current/constant voltage/ constant resistance. it has a battery mode that test the actual capacity in mAh
It turns out these might be fake and not even made by ultrafire. Can any of you recommend a good 18650 battery, preferably 4.2v so i can just swap the batteries out. Or should i ask this in a new thread? whats the REAL max mAh im going to find in this type of 18650. Honestly im thinking about switching to LI-PO batteries but i think these 18650 are safe and if needed can deliver more output
The load that will be on the batteries is 0.0700 amps.
Then test them at that load. Use a 47 Ohm resistor.
If you want guaranteed quality, buy the batteries from a reputable seller and/or one that guarantees returns.
jremington:
Then test them at that load. Use a 47 Ohm resistor.If you want guaranteed quality, buy the batteries from a reputable seller and/or one that guarantees returns.
What is the purpose of the 47 OHM resistor?
It is a load that draws about 0.07 A from a 3.2V battery.
jremington:
It is a load that draws about 0.07 A from a 3.2V battery.
I have a Rigol 3031a thats what i'm going to use it has auto shutoff/graphs/other statistics. The batteries are 4.2v.
Cool!
Hi,
notsolowki:
So i have a Rigol Digital load and i'm trying to load test a Li-ion battery to calculate how many 'mAh' the battery really is. The battery claims 4.2v and 4500 mAh. I need to know how much load to actually put on the battery and when to stop the load. Can anyone give me some tips?
Have you looked at your Rigol manual and YouTube to see if your load can work out the the battery characteristics?
It is designed for battery testing.
For $2440.00 you would expect it to be able to make coffee and scones for smoko.
Tom.... 
TomGeorge:
Hi,
Have you looked at your Rigol manual and YouTube to see if your load can work out the the battery characteristics?
It is designed for battery testing.For $2440.00 you would expect it to be able to make coffee and scones for smoko.
Tom....
Well it was only 1200 USD. But i dont think its capable of finding the most suitable load for maximum mAh vs most current output although that would be nice. I mainly use it when learning to build power supply circuits and load testing transistors and voltage regulators. It is nice for batteries tho. I will say it has some pretty hardcore bugs. If you use the PC software you can make it short the battery even with the load off. Sometimes it does that even you use the hardware interface. i would almost say its a dangerous POS except when it does work. not to mention the first one i bought was junk out of the box and shorted the load no matter what. when i took it apart it looks like someone did a real bad job repairing it. You just have to keep an eye on it.
Can any of you recommend a good 4.2v 18650 battery with a proper datasheet?
Hi,
Have you weighed them against a know good Lipo, mass will filter out the real bad fakes.
google
SAMSUNG Lipo batteries.
Here is a battery test report that may help.
https://lygte-info.dk/review/batteries2012/Samsung%20INR18650-25R%202500mAh%20(Green)%20UK.html
Tom...