dewalt bms smarts level?

[ejonesss]

i was wondering does the dewalt bms modules detect the voltage of any of the cells or the entire pack for the lvc?

because i like how the bms has a built in speed controller and i would like to wire one to a power supply to use just for the speed control.

bypassing the overload protection should be rather easy by soldering up the shunt.

the thing i am worried about is if it uses the voltage of the entire pack or a single cell to determine lvc.

or would i be better off getting a brushed scooter controller for the job,

 

[Doctorbass]

Yes I already tested that.

This BMS cut the output of the cells if any cells goes below 2.500V

The major problem with the use of BMS without great hysterisis is that the users usually do repetitive try on the trigger of the drill and make the bms to cut many times until one of the cell wont goes back to above 2.5V and stay completly drained under 2.5V and make the battery to refuse to cahrge on the dewalt charger and make all 3 leds to blink.

I confirm.. that dewalt bms cut if ANY cells goes down to 2.500V LVC


Doc

 

[jk1]

has anyone been able to bypass the over current protection on the 28 or 36v BMS, this is a big restriction down to i think 20 or 25 amps per pack on the 36v ? Also if u bypass this current limiter will the rest of the pack survive or will the cell connections melt ? it may not be a good idea to do ?

 

[ejonesss]

you mean it is like people holding the throttle on the electric bike while the fechter/ggoodrum bms is cycling until it draws the cells down to the point that the bms stays off?

i thought that you said the dewalt is not good for ev use ?

this project i got one of them drill powered wire stripping machines to get the copper from the wire and for some wires i have to run the machine slow or the wire slips off the cutter wheel.

since dewalt makes it easy to use a rotary pot instead of the trigger type i can be able to run the machine continuous.

Yes I already tested that.

This BMS cut the output of the cells if any cells goes below 2.500V

The major problem with the use of BMS without great hysterisis is that the users usually do repetitive try on the trigger of the drill and make the bms to cut many times until one of the cell wont goes back to above 2.5V and stay completly drained under 2.5V and make the battery to refuse to cahrge on the dewalt charger and make all 3 leds to blink.

I confirm.. that dewalt bms cut if ANY cells goes down to 2.500V LVC


Doc

 

[Doctorbass]

ejonesss,

Yes, if you still make repetitive atempt to draw the last electron on a nano dewalt pack, it draws the cells down to the point that the bms stays off.

So the first time it cut you must charge the pack and not continu to try using the last mAh.

About the Current limiter protection, yes you can bypass it but the BMS will no longer work to protect the cells.

What cut the power is a mosfet. And the bms have a shunt that sense the output current and protect against overload and also is controlled by the lvc circuit that can open the connection if one or more cell goes to 2.5v or under.

You could beef the shunt to allow more current but the mosfet might not be able to hold higher current.

3 years ago I already posted pictures of the indide of that Dewalt bms.. do a search on the forum you will find that.

Doc

 

[ejonesss]

doc i was intending on using one of the junk bms i got from another user one time and wire it to a power supply just to use for the speed controller.

there would be no cells attached the 2 power wires would go to a 30 volt power supply and that is why i was wondering if the bms would still activate if the monitor taps was left disconnected.