DX7 - Lowest safe voltage?

[Si Goodchild]

. Anything below 11.0 volts is likely to be a fault with either the charger, the built in voltmeter or the NiMh pack.

Just took a look at the charger I was sold with the kit. It says that the output is 10v at 60mA. I'll check the actual voltage with a meter at the weekend but this may be the problem!

[cjcj1949]

Mine is 9.6V at 150ma. Don't confuse DC with constant. It's probably full wave rectified without any smoothing. 9.6V is an average. It varies from 0 to 14V 100 times a second. 60ma is a bit low that's for a 600mah NiCd pack from long ago. It will charge them up, but it will take about 30 hours or so from flat. I'm afraid common sense can be very misleading. A meter only measures average values. To see what's going on you'll need a scope. I thought you'd worked on 3 phase stuff.

[Si Goodchild]

I thought you'd worked on 3 phase stuff.

No, not me, but I did get a lesson on it at uni about 18 years ago and understand some basic principles.

I see your point about the rms voltage versus the peak. Like you said it's probably a duff cell so I'll call Inwoods in Huntingdon before tackling Spektrum direct.

[cjcj1949]

I can't remember the difference between average and rms I know that rms is the heating effect one. Never used it. If we wanted to know what was going on we used a scope. I've just looked at a semiconductor manufacturers site and they now design things for you. You just put in the numbers and out comes your design.

[machasm]

RMS
Root Mean Square.

[jamiem]

i was listening to a podcast (allthingsthatfly.com) last week that explained exactly why you shouldnt use a lipo in a dx7. they said it was because the regulator in the dx7 is a linear and disipates the extra voltage by creating heat. The higher the input voltage, the higher the heat level. There is a company that makes a switching regulator that you can retro-fit that will not generate anywhere near the same amount of heat.

If you are going to use a lipo without changing the reg, then run it down a tad first....