Where's my watts gone?

[awol]

I wired a spare watt meter to show the power going into my battery whilst being charged just to compare with the watts I was using and there is some watts missing somewhere.
With the same journey twice and battery charged to full -
Power used 3.37aH / 117wH
Charge back in 3.5aH /145 wH
next
Power used 3.12aH / 108wH
Charge back in 3.22aH / 132wH
Is this normal for an old worn out weak battery? or just a difference between the 2 watt meters?
or something else?

 

[Alan Quay]

Charging is not 100% efficient. Your results show that charging your battery is about 80% efficient, which is about right.

Sent from my HTC 10 using Tapatalk

 

[Deleted member 4366]

You lose a bit through the bleed resistors in the BMS, which bleed the cells down from 4.2v to about 3.17v in order to balance the battery.

 

[Alan Quay]

You lose a bit through the bleed resistors in the BMS, which bleed the cells down from 4.2v to about 3.17v in order to balance the battery.

That's a typo, I'm sure D8 means 4.17v

Sent from my HTC 10 using Tapatalk

 

[Deleted member 4366]

It was a typo, but sometimes the bleed resistors get stuck on, which bleeds the cell down to 0v, and then you need an new battery

 

[PH001]

..the missing watts is really just heat dissipated in all the charging components and the battery itself.