Hello all, forum newbie here so perhaps I should introduce myself first.
My name is Paul, I Love flitetest (who doesn't) and have been into RC for some time. I now (mostly) know what I'm doing (at the expense of several planes) and like to dabble (what a strange word) in other things such as electronics.
Since RC and electronics kind of go together and since I always have a bunch of batteries lying around, I decided to build a charger for my laptop that uses two LiPos in series. Version 1 worked fine, but I didn't trust the ex-USSR military mini analog voltmeters that I picked up off of eBay, so it was rebuilt with smaller digital meters.
Unfortunately, the new meters do not like their polarity reversed (as I found out the hard way), so I tried adding diodes between the batteries and meters, but the voltage drop rendered the readings useless. The next option was to add a diode between the batteries as shown in the diagram (this also having the added benefit of preventing back-charging, which I also discovered the hard way), but this yields strange results.
When measured at the charger board, the voltage is 0 even though the batteries each read 12.4V. At the diode, the voltage is negative 24.8V. What gives? It seems that the diode is backwards, but current flows from V+ in to V- in, right?
While drawing the diagram, it became apparent that perhaps this was not the case within the pack arrangement. i.e. while current flows in one direction overall, it flows in the opposite direction between the batteries, but still from + to -.
I may have just answered my own question but just want to be sure before I go fry more meters.
Regards,
Paul
TL;DR: Diode probably backwards, please confirm!
My name is Paul, I Love flitetest (who doesn't) and have been into RC for some time. I now (mostly) know what I'm doing (at the expense of several planes) and like to dabble (what a strange word) in other things such as electronics.
Since RC and electronics kind of go together and since I always have a bunch of batteries lying around, I decided to build a charger for my laptop that uses two LiPos in series. Version 1 worked fine, but I didn't trust the ex-USSR military mini analog voltmeters that I picked up off of eBay, so it was rebuilt with smaller digital meters.
Unfortunately, the new meters do not like their polarity reversed (as I found out the hard way), so I tried adding diodes between the batteries and meters, but the voltage drop rendered the readings useless. The next option was to add a diode between the batteries as shown in the diagram (this also having the added benefit of preventing back-charging, which I also discovered the hard way), but this yields strange results.
When measured at the charger board, the voltage is 0 even though the batteries each read 12.4V. At the diode, the voltage is negative 24.8V. What gives? It seems that the diode is backwards, but current flows from V+ in to V- in, right?
While drawing the diagram, it became apparent that perhaps this was not the case within the pack arrangement. i.e. while current flows in one direction overall, it flows in the opposite direction between the batteries, but still from + to -.
I may have just answered my own question but just want to be sure before I go fry more meters.
Regards,
Paul
TL;DR: Diode probably backwards, please confirm!