battery capacity tester

[nirvana]

there's obvs a load o crap surrounding new fangled lithium ion battery capacity ie 'power bricks' are v.popular for recharging your phone on the move etc but something advertised at say 20,000mAH (why don't the fukkers say 20Ah for starters? lol) might not be anything like....

I got interested in these 50Ah batteries but I'm sure they're nowhere near...

https://www.aliexpress.com/item/1005003193186060.html

like what's the difference between this mad bastard fooker

https://www.aliexpress.com/item/4001153199791.html

and this thing?

https://www.aliexpress.com/item/32363192222.html

[belfastchild]

26 minutes ago, nirvana said:

there's obvs a load o crap surrounding new fangled lithium ion battery capacity ie 'power bricks' are v.popular for recharging your phone on the move etc but something advertised at say 20,000mAH (why don't the fukkers say 20Ah for starters? lol) might not be anything like....

I got interested in these 50Ah batteries but I'm sure they're nowhere near...

https://www.aliexpress.com/item/1005003193186060.html

like what's the difference between this mad bastard fooker

https://www.aliexpress.com/item/4001153199791.html

and this thing?

https://www.aliexpress.com/item/32363192222.html

I'll give you an example. I have a couple of old lead acid leisure batteries.

Attached to a solar panel the bottom meter would read 14.4v. Disconnected from the solar panel the bottom one would read about 11.6v.
Attach the next one up and the voltage very quickly drops to 6v then almost zero (it introduces a load).

[invalid]

 

Regarding powerbanks (i.e the USB brick things to charge your phone), the stated capacity is normally at 3.6v which for the USB needs to be boosted to 5v.

 

ACTUAL 5V mAh = 3.7 X Advertised mAh / 5

For a 10,000mAh powerbank – 3.7 X 10,000 / 5 = 7,400 mAh

So a 3.7V 10,000 mAh powerbank really only supplies 7,400 mAh output at the 5V USB connection. So straight out of the box is a 23% reduction in the stated mAh. This is not the actual level as there is also conversion loss.

 

I've bought lots of 18650 and 32700 cells from Ali and they generally test close to rated capacity using a B6 charger to test.

 

[nirvana]

10 hours ago, invalid said:

32700 cells

that's a new one for me, they look quite chunky, do you buy them with tabs on or bolts?

cheers

[invalid]

54 minutes ago, nirvana said:

that's a new one for me, they look quite chunky, do you buy them with tabs on or bolts?

cheers

 

The Littokala ones with tabs, they are LiFePO4. I've tested a few and they come in around 6.5Ah vs the stated 7Ah, close enough.

Not sure about any of the other brands.

If you buy any from China the shipping will take months, they go by train.

https://www.aliexpress.com/item/4001069782413.html?spm=a2g0o.productlist.0.0.560d5df8ewsQoL&algo_pvid=32a338d0-a19c-4574-b6cf-09ac0d7be44e&algo_exp_id=32a338d0-a19c-4574-b6cf-09ac0d7be44e-2

 

 

[nirvana]

21 minutes ago, invalid said:

If you buy any from China the shipping will take months, they go by train.

ah yeah, is it goods only? I'd like to go on a train ride and buy some cheap bikes in China lol

[onlyme]

100% get a decent RC/multi format battery charger that also has cycling, discharge and capacity testing all built in.

You'll need something to test charge any battery you might try anyway, In most cases you will want something to accurately balance batteries as well.

Something like an Imax B6 or better.

 

[nirvana]

3 hours ago, onlyme said:

Something like an Imax B6 or better

so with those ones do you buy a separate 'tray' to hold the cells in?