Homebrewed Electricity > Other
Using BadBoy charger for 30S battery
mab:
magnetjuice:
I'm afraid i can't make sense of your table or results: something's squiffy; the open cct volts are plausible, as are the loaded volts, but - by definition of ohms law, the voltage across a resistor is proportional to the amps going through it. So if you have ~10v across a 5ohm resistor you should see ~2amps - which you do; but if you have ~14v across 5ohms then the current will be ~ 2.8A. Maybe you had a loose connection to your resistor?
Harold
If your going to go down the route of badboy chargers I'd seriously consider getting hold of a variable transformer if you can - they make hack jobs like this so much easier - not least because you can wind up the supply to your experimental charger slowly until you see the ammeter move, rather than throwing a switch and getting the bang, flash & puff of smoke when somethings not right. Also they can be setup to go from 0 - 100% mains volts but also 0- 110% or more alowwing you to push above mains voltage if necessary.
the charger cct you linked seems to rely on being connected to the supply via long extension leads to use the resistance of the flex as a current limiting/stabilising feature, but also uses an inductor with switchable taps: I've had some success using a standard mains transformer as a series inductor like this, although if you want to go to 20A you need one with a fairly heavy winding - do you have any welding transformers handy?
MagnetJuice:
mab, I know exactly what you are saying. I was puzzled when I took the readings with the larger capacitors in the circuit and saw the decrease in amperage. I double-checked the connections and to be sure, I tried two other capacitors of the 4,700 and 10,000 values. The measurements with the different capacitors were very similar, within 10%. That is understandable due to the rating tolerance of electrolytic capacitors.
Even with the three lower value capacitors, you see the decreasing value of amps as the capacitance increases. Why is it that increasing the value of the capacitor decreases the amperage? There has to be an explanation for that. That is not one of my areas of expertise. I hope that someone can explain it.
Ed
mab:
Ed, just had a brainwave! What sort of ammeter were you using? The only explanation I can think of is if the ammeter was set to a.c. amps not d.c.:- thus it's reading the ripple in the current flow not the current flow - the ripple would of course decrease as cap value increases.
MagnetJuice:
mab, yes, your brainwave was the right frequency. :D
I was using a Fluke 179 to measure current and forgot to switch the range to DC amps.
Thank you for giving this some thought and finding the error.
Here is a table with the correct measurements. I used a 4 ohm resistor for the load this time.
Ed
Harold in CR:
No old welder coils available. Down here, anything not being used is scrapped. ::)
I bought a book for trying to learn electronics, and had it in my suitcase as I was at the bus stop to head for the airport. My plan was to read the book while sitting overnight at the airport. My Son called and said he cancelled my flight ticket because I might not get to return home. He was right.
My trip was to do machining of parts to bring back and lots of stuff I need to keep going on projects, all this, including medicine for my wife.
Well, here I sit, trying to make chicken soup out of chicken $#|+ ::)
Sorry I can't seem to get this stuff through my head, even though I have an O scope and signal generator sitting here that I acquired with a small business and Technician included that knew electronics. I tried to get him to help me understand electronics, but, it was all "secret sauce" and that was why I hired him. Nuff said
I will keep throwing stuff up against the wall and see what sticks, and hope everyone that has tried to help will not abandon me.
Doing a house extension for the wife and trying to get my 3 wheel motorcycle built along with this electronic stuff. Many thanks for all the advice and, I will keep working on this elecronics stuff.
Harold in CR
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