PlaneKrazee

My Feedback: (14)

A while back someone mentioned that Proline used to install diodes across the cells in a battery pack to prevent total loss of power if a cell failed. Does anyone have a schematic of this or could you explain it again?

It seems this is a great idea. Instead of running two packs, run one 6v pack and if a cell fails you can still fly and land. You would find the problem while checking the battery voltage during the next preflight.

Does anyone know what the part number of the diodes would be?

Thanks.

hackken

Years ago it was common to put a 1N4148 or 1N914 diode directly across each cell in the transmitter so that if a cell failed (opened up) the diode would carry the current from the remaining good cells and the transmitter would continue to operate. Since these diodes can carry approximately 200 MA they were adequate for the transmitter. If you were to use a 6 volt receiver pack you could use a higher rated diode such as an ECG 552 which is rated at 1 amp and would carry the load of the receiver and ordinary servos. I suppose if you are using digital servos you might possibly want to use a higher rated diode. The band end of the diode is placed on the positive side of the battery. Hope this information is of some help.

iflyj3

My Feedback: (7)

The common failure mode of Nicads is to internally short. Due to the cell shorting, the diode is not needed. I have not seen a Nicad fail open, but I have not seen everything.
Your five cell pack would work as you described without diodes.

hackken

I agree with iflyj3. The normal failure mode of nicads is to short internally, in which case a diode is not needed. I have messed around with radios and nicads for many years and have only found 2 instances where a nicad has failed in the open mode. In these instances a diode could have been useful.

ChuckA

In 40 year of flying with nicads, I have had one cell open in the air. That was in a Sailaire sailplane and it failed in flight. Fortunately, I recovered the model without damage and was able to find the bad cell. Once in 40 years doesn't make it worth while to install diodes.

dirtybird

My Feedback: (5)

At the time Pro-Line was being made G.E. was the primary supplier of Ni-Cad batteries in the US. GE did not weld the internal connections, relying on only a press fit. An open connection was quite common. The usual result was an intemittant,hard to find trouble. Once the Japanese batteries came on the market this problem went away along with the GE batteries and GE as a supplier.

PlaneKrazee

My Feedback: (14)

What about Nihm batteries? How do they fail?

PlaneKrazee

My Feedback: (14)

bump