bigal_scorpio
Active Member
Hi to all and seasons greetings!
I recently bought some Li-Ion battery protection boards with the idea of making a few extra batteries for our power tools as my son now has a 3d printer and can make the housings for them.
While in the testing process I have noticed a few problems, like the tools will only function if the trigger is pressed slowly and if that is not observed then the battery must be removed and replaced before the circuit will reset. I can understand the reset problem but the boards are rated 20A constant load and 30A cutout limit. The drill I am testing on is a Makita 18v battery drill and however I try I can't get it to draw more than 8A without actually stalling it. Odd!
However the real thing that stumps me is that when not in use the board gets warm. The row of 7 tiny 3 legged devices marked 431, which seem to be NPN transistors get warm to the touch, hot to the lips which are a lot more sensitive and my go to form of temp test. Now the text for the boards says the static draw is 0 to 500uA which if true would surely mean nothing got warm enough to feel? So I decided to test the drain on the batteries.
Now I got really baffled. With the boards plugged onto the battery pack and full cells (the boards actually balanced the cells to within 1mV!) and testing the current through the wire from the battery neg to the BAT- pad on the board with the meter on its 200mA scale it wavers between 0.4 and 0.5, however I kept lowering the scale and eventually measuring on the 200uA range I get 0.4 how can it be both? So I dragged out my good meter and on the 200mA scale it shows 13.33, on the 20mA scale it was 4.35 and on the 2mA scale it is 0.583 What is happening here?
If even one of my measurements if close to true how is the board getting warm and how long would anyone think the cells would last before flat. In all the time I have used PIC microcontrollers with the low usage sleep modes I have never felt anything even approaching warmth from them so is it possible that these boards could be only using microamps and still become warm?
Sorry for the long tome but I am just stumped. Oh I nearly forgot to put the link to my boards on. Doh!**broken link removed**
Thanks, Al
I recently bought some Li-Ion battery protection boards with the idea of making a few extra batteries for our power tools as my son now has a 3d printer and can make the housings for them.
While in the testing process I have noticed a few problems, like the tools will only function if the trigger is pressed slowly and if that is not observed then the battery must be removed and replaced before the circuit will reset. I can understand the reset problem but the boards are rated 20A constant load and 30A cutout limit. The drill I am testing on is a Makita 18v battery drill and however I try I can't get it to draw more than 8A without actually stalling it. Odd!
However the real thing that stumps me is that when not in use the board gets warm. The row of 7 tiny 3 legged devices marked 431, which seem to be NPN transistors get warm to the touch, hot to the lips which are a lot more sensitive and my go to form of temp test. Now the text for the boards says the static draw is 0 to 500uA which if true would surely mean nothing got warm enough to feel? So I decided to test the drain on the batteries.
Now I got really baffled. With the boards plugged onto the battery pack and full cells (the boards actually balanced the cells to within 1mV!) and testing the current through the wire from the battery neg to the BAT- pad on the board with the meter on its 200mA scale it wavers between 0.4 and 0.5, however I kept lowering the scale and eventually measuring on the 200uA range I get 0.4 how can it be both? So I dragged out my good meter and on the 200mA scale it shows 13.33, on the 20mA scale it was 4.35 and on the 2mA scale it is 0.583 What is happening here?
If even one of my measurements if close to true how is the board getting warm and how long would anyone think the cells would last before flat. In all the time I have used PIC microcontrollers with the low usage sleep modes I have never felt anything even approaching warmth from them so is it possible that these boards could be only using microamps and still become warm?
Sorry for the long tome but I am just stumped. Oh I nearly forgot to put the link to my boards on. Doh!**broken link removed**
Thanks, Al