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        Discussion Current drain of Hobby King LiPo moniitor

#1 SoloProFan Oct 12, 2012 03:55 AM

Current drain of Hobby King LiPo moniitor
 
Anyone knows or has measured the current drain of this Hobby King LiPo voltage monitor?

http://www.hobbyking.com/hobbyking/s...idProduct=7224

#2 wparsons Oct 12, 2012 03:21 PM

IMO, don't buy it. 6v is way too low for a cutoff on a 2s pack. You want something more like 3.4v/cell, or even higher if you run high C packs.

#3 SoloProFan Oct 12, 2012 04:52 PM

I already have it, and the different led conditions make it possible to stop way before the 3 volts. I don't let it get beyond flashing blue light anyway, and certainly won't drive till it starts buzzing.

But the reason I wonder about the current draw is that the connector is under the body of the car, and if I can keep it connected I don't have to remove the body when I go drive for 10 minutes in my morning break, and then later that day in another coffee break or so.

#4 wparsons Oct 13, 2012 01:44 PM

As a general rule, you shouldn't leave the battery plugged into anything when not running it.

#5 Bugman Jeff Oct 13, 2012 04:09 PM

I agree that you shouldn't leave a battery plugged in regardless. That said, and if no one knows the answer, you can do your own sort of test. When you get home some night, plug it in and record the battery voltage with a voltmeter. Come back an hour later and check the voltage again. If it hasn't changed much, check it again an hour after that. It should only take an evening to figure out if it's going to drain to quickly.

#6 SoloProFan Oct 14, 2012 02:34 AM

It's not that the car is out of my sight during the pause, where it is deactivated until the next coffee-break. But there is a risk letting it plugged in if something comes between me and driving my car. I could opt for a small switch between saver and battery, that way I can still leave the saver connected but not powered and I can leave the body on, but have all the electrics unpowered.

Measuring voltage drop can be a little deceiving, it's hard to determine the used mAh as the voltage drops very slowly on a LiPo. I think it's better to measure amp draw directly, or in this case probably milli-amp draw...

#7 raw111 Oct 20, 2012 10:03 PM

I don't know specifics but my summit originally had one on one 2s and i would notice after every run the one it was on since you only connect to 1cell was always. .10 lower than the non monitored side and this was usually after a 30 min run. I would advise against as it unbalances your cells. If need one get one that checks all cells, or upgrade to a lvc esc, or even a novak smart stop, its what i run on my summit now

#8 SoloProFan Oct 21, 2012 01:21 AM

This one looks at the tota voltage, not a single cell. That is why you need to buy a seperate one for each type of battery, 1S, 2S, 3S, etc. So no risk of unbalancing the lipo. But so far I end up driving only once a day, so I don't leave anything plugged.

#9 cenracer1 Oct 22, 2012 10:00 PM

I have a couple of these units and I use them in some of my boats and my sons 1/16 Traxxas before switching to brushless. Couple of things here.. They do monitor the whole pack not just one cell, They blink before they go solid red and the alarm although faint does sound.. And lastly, do not leave it plugged into the battery for an extended period. I did one and forgot it overnight.. The used battery that was at 3.6 volts fell to well below 3 volts when I remembered the next day. Thankfully it was a smaller cheap pack and nothing but a lesson learned.. Don't leave lipo's plugged in ever when not using them....I can't say they will drain a larger pack if left on for a long period, but smaller packs you have to be aware.

#10 SoloProFan Oct 22, 2012 11:46 PM

Thanks for the insight. What do you consider a small pack, what capacity? From 3.6 to 3.0 isn't that much in capacity usually, as 3.6 unloaded voltage means the lipo is already over 85% drained, probably more close to 90%, and voltage tends to drop much faster in that stage then going from full state, at 4.20 volt, to considered pretty empty, 3.7 volts. The current drain of a regular SMD led can't be that high.

#11 cenracer1 Oct 23, 2012 07:48 PM

The small pack i was refering to was a 1300 mah 3 cell lipo in one of my small heli's.. I unplugged the esc, but forgot the lipo monitor was still plugged in. just in too much of a hurry I guess.. It was raining and had to run inside.. Thankfully, discharging the battery usually kills the battery but didn't in this case lead to anything else.. Puffed or worse.. Battery looked fine, just wouldn't take a charge after that


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