Higher pinions = safer MMM's? Or no? Someone's lying.... - RC-Monster Forums

BrianG · 11.03.2009, 02:24 PM

lol, I'm not an EE, just an enthusiastic hobbyist.

J57ltr · 11.03.2009, 02:49 PM

The ICE charger I have only measures resistance when doing a discharge. After a few minutes during the discharge cycle you can see the graph rise then fall back down, so basically you have what looks like a cosine pulse. To me it's the charger dropping the load and allowing the voltage to rise then applying the load again, then it calculates the resistance. It doesn't seem to change too much with loads between 1 and 10 amps. I have noticed that different packs have different readings and they do change but they are usually within about 5% from what I have seen on this charger. this is the only charger I have experience with that has this function, but I thought that all chargers only did this during discharge.

One question I have is how much resistance is too much? The other thing I see is that the internal resistance will increase with the number of cells. So basically all things being equal a 6S pack will have a higher internal resistance than a 4S pack made from the exact same cells.

Jeff

snellemin · 03:18 PM

Quote:

Originally Posted by J57ltr

The other thing I see is that the internal resistance will increase with the number of cells. So basically all things being equal a 6S pack will have a higher internal resistance than a 4S pack made from the exact same cells.

Jeff

This is why you would use parallel packs to bring the resistance down. Or use a bunch of caps to compensate.

J57ltr · 11.03.2009, 03:40 PM

Quote:

Originally Posted by snellemin

This is why you would use parallel packs to bring the resistance down. Or use a bunch of caps to compensate.

As I see it if ripple is the problem then caps would help, but if the voltage is rising to a dangerous level then you need the TVS as well. To me since we are talking about IR of battery packs the problem would be that you couldn’t shove the electrons in to the battery fast enough so the voltage “backs up” (or rises) to an unsafe level. So then you need something to clamp this voltage to a safe level, enter the TVS that’s what its job is that’s what it does. So basically both are needed if the IR of the pack is too high. What is too high?

Jeff