Hey everyone!I'm running into an issue where I have some servos hooked up to an Arduino, but they aren't drawing enough amps from the LiPo battery. I can hear and see them act much faster when I hook it up to my desktop power supply. The reading on the desktop power supply is telling me it's consuming around 5Amps, but when I use my Lipo battery and try to test it with my multimeter, the max amperage is 1.25 (also it feels like testing amperage with the multimeter is making my servos noticeably slower, do I have a shitty multimeter that is introducing more resistance than normal??) Mutlimeters in current mode do add a shunt resistance which cuts down the voltage a little that the servos will receive, it's called it's 'burden voltage'. Is your battery under servo load putting out the same amount of voltage as your desk power supply?I'm using a 7.4v 1800mah 25C LiPo battery which from what I read on the internet, it should have a max amp draw of 45?The so called C rating (as in 25C) is a somewhat variable rating, kind of like gas mileage ratings on cars, your batteries C rating may vary with age and usage. Capacity * Discharge rate / 1000 = Max amp draw1800 * 25 / 1000 = 45 amps45 amps discharge but only for like 2.5 mins, and there is no condition where your servos will be trying to draw 45 amps. So the question is when on the bench supply what amps do the servos draw at what voltage output, compared to what amps they draw at what voltage when on the battery?By the way most servos want voltage anywhere from 4.8 to 6.0 volts. What voltage are you trying to feed them and is it above the recommended maximum voltage the servos are rated for? I'm powering my motors separately than the Arduino so that shouldn't be a problem. I tried switching to a battery with a higher discharge rate of 65C and everything seemed to work fine, but I'm wondering why the other battery can't output as I expected...Could just be a tired battery not able to output it's rated current any longer?Thanks for the help!-Alonso
Hi Retrolefty,I have an adjustable power supply which I'm setting to 7.4v, and the LiPo battery also shows 7.4v when tested with the multimeter. The batteries are brand new so there shouldn't be any problems with the discharge rate being lower than original. I'm using three of these high voltage servos: http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=18399
Hey Lefty,I will definitely check the voltage as you mentioned when I get home, but in theory that battery should be able to handle those high-voltage servos no problem right???Time will tell, make your measurement tests. You don't usually have to worry about wire gauge when dealing with amperage below 15 right??No, any given wire size might be too small for some amount of current, that is why you will measure to see if you are dropping voltage on the way from the battery to the servo positive and back from the servo negative to the battery negative. It's a case of measured data out weights opinion and guesses.-Alonso
You have done something wrong there, because LiPo batteries have a huge current capacity.
Quote from: michinyon on Apr 05, 2013, 07:16 amYou have done something wrong there, because LiPo batteries have a huge current capacity.Or might be a bad battery / bad battery protection circuit.