Battery Voltage

[oldblue2010]

I usually run my 2 or 3s batteries in my crawler till they no longer run the truck is this bad for the battery? Sounds stupid I know but an airplane guy said to get a battery alarm when the battery falls below (?) voltage the alarm goes off- I told him the crawler don't fall from the sky...usually-my 3s went down to 8.78 before it quit- any ideas or suggestions? Thanks in advance- Vic in SoCal

[Inspector86]

You did not specify what truck, ESC or batteries you're running but it sounds like your ESC is hitting low voltage cut off. Every modern ESC that can use LiPo batteries includes a low voltage cutoff feature to protect the battery from over discharging. It sounds like you are just running your batteries until you hit the cutoff and at 8.78v the cutoff is set a bit too low.

[midwest_rippa]

3.2v per cell is what i run down to. so for 3s 9.6v is the minimum id recommended

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[nightcrawler48]

If you're down at 8.78V on a 3s you're letting the battery get too low. Minimum voltage for each cell needs to be 3V+ which would be 9V+ total. You have at least 1 cell, or more, below minimum voltage. Most people like to set their Lipo cutoff at about 3.3V per cell, so 9.9V for your 3s. It would seem your ESC battery cutoff is too low or nonexistent. A battery alarm, as Inspector86 suggests, would be a good investment before you totally destroy your battery(s). Relatively inexpensive, around $5, and most are adjustable to set your individual cell voltage to a safe level. The one you're looking for plugs in to the balance plug on the battery.

[Crawler Cads]

What ESC?

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[Zondar]

LiPo batteries are very delicate. You really, really don't want to run them down below their minimum voltage, and preferably not very close to their minimum.

At 3.2V per cell minimum, you would want to stop at 9.6V. Better ESC's will shut down the truck when reaching some pre-set or programmable minimum value (again, typically 3.2V as a default per cell).

Likewise, you really, really don't want to over-charge your batteries (max is usually 4.2V per cell for normal LiPo), but your charger hopefully knows about that.

Also: Don't leave your batteries fully charged for very long. Ideally, you would charge up and run down the battery the same day. If you do store your batteries for a long time, then you should condition them to about half their full voltage. Don't leave them fully charged or empty.

[nightcrawler48]

Originally Posted by Zondar

Likewise, you really, really don't want to over-charge your batteries (max is usually 3.7V per cell for normal LiPo), but your charger hopefully knows about that.

Actually, a fully charged Lipo will be at 4.2V per cell, therefore 3s will be 12.6V with a full charge. There seems to be a thought nowadays that charging should be topped at a little less, maybe 4.1V per cell. I have some batteries that are 6 years old and have always been charged to 4.2V per cell without any issues.

Also: Don't leave your batteries fully charged for very long. Ideally, you would charge up and run down the battery the same day. If you do store your batteries for a long time, then you should condition them to about half their full voltage. Don't leave them fully charged or empty.

3.8V to 3.9V per cell is the recommended storage voltage for Lipo batteries. Most chargers will automatically charge or discharge to this voltage when you select "storage" in the charger menu. Storage voltage is key to battery longevity. Some people say if you have run the battery today and plan on using it tomorrow then just do a full charge on it and you're ready to go tomorrow. However, any more than the one (1) day and I always do a storage charge when I get home from a run. There are posts on this forum from people who have storage charged their batteries, put them away, and pulled them out 6 months or a year later and the batteries are still good to go with a new charge in them.

Proper battery maintenance = battery longevity

[oldblue2010]

this esc is an old hobbywing (writing wore off a while ago) brushless on an Ax10 I believe

now on my TRx4 I have a hobbywing 1080 esc- the same batteries are 3s lipo I will take everyone's recommendation to set the esc shut off at 9.9 / 9.6v- thanks for the info- now to check the manual on how to do this

[nightcrawler48]

Originally Posted by oldblue2010

this esc is an old hobbywing (writing wore off a while ago) brushless on an Ax10 I believe

now on my TRx4 I have a hobbywing 1080 esc- the same batteries are 3s lipo I will take everyone's recommendation to set the esc shut off at 9.9 / 9.6v- thanks for the info- now to check the manual on how to do this

The HW 1080 doesn't set Lipo cutoff by voltage. Program Item 3 is "Cutoff Voltage" and if enabled you have three choices - Auto (Low), Auto (Medium), and Auto (High). Don't know if anyone ever did figure out the actual voltage for those settings. I started out with the Auto (Medium) setting and after a test run thought it was too close to 3.0V for my liking so changed to Auto (High). I'm happy with that but I'm also conservative so you may be happy with Auto (Medium). Didn't even consider Auto (Low) after the Auto (Medium) test.

Not too sure where to find it now but a few years ago there was a post asking members to list the settings they were using for all the program items. For Cutoff Voltage - Auto (Medium) and Auto (High) were about a 50/50 split.

[Zondar]

Originally Posted by nightcrawler48

Actually, a fully charged Lipo will be at 4.2V per cell, therefore 3s will be 12.6V with a full charge.

Ah, yes, sorry. That 3.7V is the normal operating voltage, but one charges to as high as 4.2. Thanks for the correction.