# How to verify advertised capacity of a 10,000mah phone replacement battery from China

#### bigrobot

Joined Feb 19, 2017
40
Some people have warned me against buying SSDs and batteries from Chinese sellers, like from AliExpress. Because the seller could be lying about storage or cell capacity. But when it comes to a battery, if I have a multimeter, can't I verify the advertised capacity? If real capacity matches the advertised capacity, very good. If not, I can always return and complain to aliexpress.

My smartphone's original battery is just 3,220 mAh.
So my question: Don't I need just a multimeter to verify the advertised capacity? Wouldn't this remove any risk of buying batteries from unknown sellers? (As long as you buy from a website that has buyer protection for dishonest selling.)

Tue May 16 21:28:29 PDT 2017 update: here's an example of what i was thinking of buying https://www.aliexpress.com/item/New...-Samsung-Galaxy-Note-4-N9100/32718870300.html

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#### #12

Joined Nov 30, 2010
18,217
A huge 8000 mahr battery is about 1/10th the amp-hours of a car battery. Huge is relative.
You will need a resistor to use up the available current, a volt meter, a clock, and a pencil.
Measure the resistance, connect it to the battery, and mark the voltage at some time intervals.
When the battery arrives at the alleged discharge voltage, sum up all the amp minutes and see what the result is.

That doesn't subtract the risk. It verifies the product.
You still have the risk of fussing with a return product.

#### bigrobot

Joined Feb 19, 2017
40
A huge 8000 mahr battery is about 1/10th the amp-hours of a car battery. Huge is relative.
You will need a resistor to use up the available current, a volt meter, a clock, and a pencil.
Measure the resistance, connect it to the battery, and mark the voltage at some time intervals.
When the battery arrives at the alleged discharge voltage, sum up all the amp minutes and see what the result is.

That doesn't subtract the risk. It verifies the product.
You still have the risk of fussing with a return product.
thanks "#12".
what resistor do you suggest? Would using a resistor that drains the phone more quickly a good idea? Or are there downsides to using a quick-draining resistor?
If the only risk is "fussing", I'd take a $15 unknown battery over buying a known "ZeroLemon" for$65.

#### #12

Joined Nov 30, 2010
18,217
what resistor do you suggest?
It depends on what kind of battery, but a 10 hour discharge rate is common for some batteries, and you get less amp-hours if you try to empty it in 3 hours. So, that's a start.

You also did not tell the voltage, so R = V/o.8 amps is also a starting number.

This resistor might be a light bulb out of a car for a 12V battery or something entirely different.

#### bigrobot

Joined Feb 19, 2017
40
It depends on what kind of battery, but a 10 hour discharge rate is common for some batteries, and you get less amp-hours if you try to empty it in 3 hours. So, that's a start.

You also did not tell the voltage, so R = V/o.8 amps is also a starting number.

This resistor might be a light bulb out of a car for a 12V battery or something entirely different.
Sorry, for my lack of info. According to item page, "Voltage limit: 3.85v". Max v: 4v.
Lithium ion.

#### #12

Joined Nov 30, 2010
18,217
Li-ion batteries are famous for high amps, so I think we can speed this up. What is 8 amp hours in 3 hours? 8/3 of an amp. What resistance will allow 8/3 of an amp at 3.9 volts? 1.46 ohms. What do you have laying around at about 1.5 ohms?

Nothing? Then you will have to buy a resistor and it's going to have to be about 20 watts rated.
Got any 10 watt light bulbs that want about 4 volts?
(Yes, you run a light bulb a lot hotter than a resistor.)