BatteryMooch
10 kW
Hello all,
After hearing of several CBA II's burning out their MOSFETs, often along with other components, I decided to do a thermal analysis of the CBA. I've posted it at: http://www.camlight.com/techinfo/CamLight_Systems_CBA_II_Thermal_Analysis.pdf
For those who don't want to wade through all those pages , my conclusions and recommendations are as follows:
- For reliable, long-term operation of an unmodified CBA, do not exceed 65W when discharging at under 29A.***
- To help prevent the burning out of the MOSFET (and perhaps other components) in an ummodified CBA, never exceed 86W when discharging at under 29A.***
- To help prevent the fuse and fuseholders from dropping out of the circuit board and possibly shorting out your battery pack, do not use an unmodified CBA for discharges above 25A.***
- Replacing the CBA’s MOSFET and fan allows for reliable, long-term operation at up to 80W when discharging at under 29A.
- Replacing the CBA’s MOSFET and fan can help prevent the short-term burning out of the MOSFET at up to 106W when discharging at under 29A.
- Replacing the CBA’s MOSFET and fan can help prevent the dropping out of the fuse from the circuit board at higher discharge current levels.
- When discharging at a current level above 29A, the long-term reliability power level and absolute maximum power level mentioned above can be increased a bit. But, I recommend not exceeding the levels mentioned above to give yourself a bit of a safety margin.***
*** These recommendations are based only on temperature measurements and calculations. Any derating that might be required as the battery voltage rises cannot be determined since the CBA’s MOSFET doesn’t have a rating for use as a load. Even when operated well within these recommended ratings, the IRL2910 MOSFET could burn out at any time. Especially for discharges at higher battery voltages.
I'd be very interested in your thoughts on the paper and about any mods you've done to your CBA!
After hearing of several CBA II's burning out their MOSFETs, often along with other components, I decided to do a thermal analysis of the CBA. I've posted it at: http://www.camlight.com/techinfo/CamLight_Systems_CBA_II_Thermal_Analysis.pdf
For those who don't want to wade through all those pages , my conclusions and recommendations are as follows:
- For reliable, long-term operation of an unmodified CBA, do not exceed 65W when discharging at under 29A.***
- To help prevent the burning out of the MOSFET (and perhaps other components) in an ummodified CBA, never exceed 86W when discharging at under 29A.***
- To help prevent the fuse and fuseholders from dropping out of the circuit board and possibly shorting out your battery pack, do not use an unmodified CBA for discharges above 25A.***
- Replacing the CBA’s MOSFET and fan allows for reliable, long-term operation at up to 80W when discharging at under 29A.
- Replacing the CBA’s MOSFET and fan can help prevent the short-term burning out of the MOSFET at up to 106W when discharging at under 29A.
- Replacing the CBA’s MOSFET and fan can help prevent the dropping out of the fuse from the circuit board at higher discharge current levels.
- When discharging at a current level above 29A, the long-term reliability power level and absolute maximum power level mentioned above can be increased a bit. But, I recommend not exceeding the levels mentioned above to give yourself a bit of a safety margin.***
*** These recommendations are based only on temperature measurements and calculations. Any derating that might be required as the battery voltage rises cannot be determined since the CBA’s MOSFET doesn’t have a rating for use as a load. Even when operated well within these recommended ratings, the IRL2910 MOSFET could burn out at any time. Especially for discharges at higher battery voltages.
I'd be very interested in your thoughts on the paper and about any mods you've done to your CBA!
