SSC P7 8x7135 2.8A Board

[DocD]

Hi
Can this be used with three or four 1.2volt,10,000mAh rechargeable batterys any idea of the run times with a P7? cheers DocD

 

[KrisP]

Yes, it can be used with both, but with with 3, it might go out of regulation quite soon. The voltage drop over the circuit is meant to be low, but from a few tests i've done it seems to start dropping the current output very early when run from three cells.

4 cells will work perfect but you may want to heatsink/pot the board as it can get quite hot.

 

[TorchBoy]

Yeah, what KrisP said. He got it in a nutshell.

 

[freedom2000]

Yes, it can be used with both, but with with 3, it might go out of regulation quite soon. The voltage drop over the circuit is meant to be low, but from a few tests i've done it seems to start dropping the current output very early when run from three cells.

4 cells will work perfect but you may want to heatsink/pot the board as it can get quite hot.

It might not --> it will !

The drop out of this driver is 0,1V
3 cells in serie gives 3.6V --> 3.5V with the driver's drop out... just below the Vf of a SSC P7... so "useless" with 3*1.2 V batteries (excepted at the very beginning when they are fully charged)

JP

 

[DocD]

It might not --> it will !

The drop out of this driver is 0,1V
3 cells in serie gives 3.6V --> 3.5V with the driver's drop out... just below the Vf of a SSC P7... so "useless" with 3*1.2 V batteries (excepted at the very beginning when they are fully charged)

JP

can you place say two 3.7volt rechargeables two make 7.2 volts instead of one 3.7 volt rechargeable will this work or willl it go

 

[TorchBoy]

It might not --> it will !

The drop out of this driver is 0,1V
3 cells in serie gives 3.6V --> 3.5V with the driver's drop out... just below the Vf of a SSC P7... so "useless" with 3*1.2 V batteries (excepted at the very beginning when they are fully charged)

According to the specsheet it's in regulation with 0.12V dropped across it (and that reduces as the supply voltage continues to drop under what's required to stay in regulation). The voltage under load of three NiMH cells will depend on their state of charge and how well they hold up under the particular load. Eneloops do quite well, many other brands don't. The Vf of a particular model of LED is not a fixed number either. Hence the use of a generalisation is reasonably justified. Having said that, I'd personally go for four cells, not three.

can you place say two 3.7volt rechargeables two make 7.2 volts instead of one 3.7 volt rechargeable will this work or willl it go

I suggested in another thread a day or two ago that you could use power diodes to drop the supply voltage 0.6V per diode. A bit wasteful, but it would get rid of excess voltage without the linear regs having to burn it off.