Mike's Li-SAVER
 

I'm just about to order mike's li-saver. Question is how many cells can it handle? and what voltage does it cut off at?

The Li-saver is good for 2-10 cells.

I dont see it in the documentation anywhere, but I believe it cuts off at 3.0v/cell.

nice one...

has any had any issues with this save cutting out too low?

I have used the lisaver on 4s with no problem at all.

how does this li-saver react when voltage is low? total cut off or reduced power?

Total cut off. going back to neutral resets it and you can move again to get it off the track, but you shouldnt drive after the cut out.

Nice - Would be a great feature to include with CC UBEC... option to cut power to RX...

thanks for d input guys!!!

I'll definately get it for my Schulze controller.

Here's a question: Have any of you had problems with the li-saver cutting too early?

If I jump on the throttle, the truck jumps forward and immediately (violently) stops, which makes me think that the li-saver is cutting in.

The truck drives fine if I'm easier on the throttle (more gradual). If I bypass the li-saver, the truck acts like I expect it to and wheelies all the way down the road.

Are my batteries just dropping that much voltage that it trips the lvc, or is the lvc too sensitive or set too high?

Thoughts?

(Set-up: BL-Revo, MM, UBEC, 2 x 2s 6k lipos fully charged, Spektrum rx/tx)

Thanks!

If those 6000mah lipo's are the Max Amps ones, then they are probably the problem. They tend to drop their voltage without even a huge load on them.

They definitely drop their voltage under load more than higher quality packs, but they were fresh off the charger at 16.8V. They can't be dropping that much voltage, can they? The same packs don't trip my MM's LVC.

I think I need to hook up my Eagle Tree to see what's happening when it cuts out like that.

Thanks again for your help.

I remember having a similar problem when I first used that Lisaver. I was using 5s 8000mah 10C batteries in a heavy savage. I changed to better batteries and havent seen it since. I actually forgot about it until I read this post. The LiSaver seems to have a very hard cut off. If it touches 3.0v it shuts down.

I would be interested to see your eagle tree data though. I never did that... but probably should have looking back.

Any reason why you are not using the internal lvc on the mm? I have used it all of the time when running 4s, and works fine.

Oh oops, I wrote the wrong thing earlier when I posted the set-up.

The li-saver is being used with a BK9920 in my Revo.

I used to have an MM in the Revo with the same motor and packs and the MM LVC didn't trip like this one does.

I'll try to get the EagleTree data tomorrow. I'll also try it with 5s True R/C 8K packs to see if it does the same thing.

Sure enough! I just got my EagleTree data and every time it hits 60 amps or greater, the voltage drops to 12V or below. To be a little fair though, they weren't freshly charged this time. They started at 3.9V/cell.

The peak current was 130A and that dropped the voltage to 9.1V. Yikes.

I have 4 total 2s 6K MaxAmps packs, so I'll have to test a few more combinations of them to see if I can narrow down one of them that might be causing the problem.

For this graph, I just averaged the voltages for everything under 110A.

http://i192.photobucket.com/albums/z...ltDropRevo.png

That'l do it. Glad to see you at least identified the problem.

I dont know if you have room, but try running 2 of those packs in parallel just to verify that a battery that holds voltage better solves the problem.

I think the reason the MM doesnt kick out is CC put a timer on the LVC in the MM. It needs to stay below the cut off voltage for a few seconds before it cuts out.

Good call. I'll give that a shot. Thanks again for your help.

BTW... That really sucks that those lipos drop voltage that badly. I would be writing a letter or calling MaxAmps and looking for a refund if they were mine. a 20C battery should stay well above 3.0v at the 20c load. That isnt even constant, its just burst. the 6000mah pack at 20C should stay above 3.0v at the 120A load you showed. 2.3v/cell is useles at 20c draw.

Hell... Those arent even good numbers for a 10c cell.

I'm going to keep somewhat of a running diary here.

So, I have 4 total 2s 6k MaxAmps packs. Let's call them A, B, C, and D.

Last night's test was with packs A and B, but they weren't fully charged.

I did a 10 minute run with the A and C combo just now (fully charged). They hit the LVC at 80A or above.

Interesting observation is that pack C was 99F while A was only 85F. Motor was 113F and BK9920 was 105F.

My next test will be with packs B and D.

http://i192.photobucket.com/albums/z...tDropRevo2.png

Another update.

Another 10 minute run with packs B and C fully charged.

The combo hit the LVC at 70A and above.

Both packs were 95F. Motor was 116F and ESC was 105F.

At 157A the pack hit 8.82V.

http://i192.photobucket.com/albums/z...tDropRevo3.png

And here's both runs next to each other with a bit of smoothing:

http://i192.photobucket.com/albums/z...tDropRevo4.png