Hey if you cut it off at 2.7 then at least its above the "permanently damaged and reduced capacity" point

There's are tons of arguments about how much each under volt affects the overall life. Here on rcgroups they suggest you have reduced your battery life to 80 percent at 3.5 volts but I don't think they have tests to confirm that. http://www.rcgroups.com/forums/showthread.php?t=190495 I have read of people using them in planes and running them down to 3.1 volts but then they only get around 30 to 40 cycles of life through them which to me sure feels like a significant impact on the longevity of a lipo.

@rich it doesn't sound like you have been through more than a cycle or two , just adjust it for 3.7 volts in the future and you will max the possible future life out of them. Happy batteries lol

Undervolt batteries will not charge, at least not on any decent charger, they will error and refuse to try.

Just checked it on google and a bunch of RC forums and 2.7v is the absolute minimum, most claim 3v so even the cheaper LiPos don't undervolt. Retail protection circuits hard cut off at 3.0v and soft cut off at 3.3v. Everything I found suggests a low level cut off at 3.3-3.4v

Where did you get the 3.7v from since everything I just read (and remember reading when I was making the LiPo monitor script) seems to say otherwise (3.3v to give that wriggle room before damaging the cells).

In case it's not apparent, I'm not arguing it It's just I have provided people with scripts etc. for shutting off or warning on LiPos and since it's other people's batteries I want to make sure it's all OK. I'm not worried about my battery, I have only charged it once and then I don't think it was even that low. What I don't want is to have a lot of angry people coming on because of a script I provided

how can I tell that a lipo battery is going to undervolt and how can I prevent it the cheapest way?

Use the lipo circuit and monitor I did a tutorial on (it's linked to in an earlier post here).

It's a very cheap and simple circuit, one cell connects directly to one ADC port the other goes through a voltage divider (3 resistors), with a diode for over voltage protection on the ADC port (optional, but recommended). Then a script runs and checks the voltage every x ms, the discharge rate isn't too bad so every 500ms or even 1s would be fine. If it's getting low it tells you, it can shut down things or even disconnect the EZ-B from the PC. It doesn't shut off the battery though so you will need to disconnect or charge it relatively quickly depending on min voltage level set.

Or, you can get balance port monitors that plug in to the balance port, report the voltage and buzz when low. They are cheap and stand alone, but don't shut the battery off.

Or try the auto shutoff circuit I posted, but I haven't had chance to test it yet. This one will shut off power to everything on low voltage but does draw current itself so eventually will undervolt the battery (would take a fair amount of time, like hours or maybe even days).

Melvin uses the monitor circuit and reports the voltage on the LCD in a similar way to the battery icon on a phone. The only time I undervolted a battery was when I forgot to disconnect it and didn't touch it for weeks.

Rich built a circuit and can show you how to monitor it on your ezb. He's very talented with script.

@Rich, I use to be into rc cars and planes. I've always stayed with the 3.7 volt rating from the factories but lots of individual hobbiest like to push the equipment as far as they can before something noticeably bad happens. 3.7 is what I have stayed with and worked very well to maximize battery life. I use to work for horizon hobbies and we tested all kinds of stuff , even melted just about every lipo bag too. To be safe I would have the script stop at 3.7 volt. Thats my suggestion. I realize that others claim various voltages but for me its safe over sorry lol.

That's good enough for me I'm not 100% sure what I put in the script anyway, I know it's a variable at the start so the user can set it themselves if they want to risk going lower but it's always good to have good values as defaults.

Edit: Just checked, it's set at 3.7v for low and 3.5v critical anyway which should be OK depending on the current draw of the robot and circumstance.

now for me to do all that, slim. I barely understood half of what I just read. Yes lipo batteries are awesome for life, but the care you have to take with them is to far out of what I think of as my standard.

I would love to use lipo batteries but I just dont have the patience and/or understanding to work with them.

@jstarne, Ni-mh batteries you can drain completely, and charge from anywhere in its power level.

On another note, what is the next best battery?