Cut off voltage for LiFePO4

[funflair]

I know there are some experienced LiFePO4 builders and users on here so asking for a friend what would be a sensible voltage for the BMS to cut the supply to protect the cells from damage, I know our SuperB info says end of discharge voltage = 8v but I think that would be a bit low for protection and longevity.

Martin

 

[Floydster]

Hi Martin
My V min is set at 12v, as you say 8v is low IMO

Paul

 

[Two on Tour]

I use a Victron Battery Protect on my LiFePo4 and mine is set for 10 volts and I would not want to go below that personally.
I have see 2.6 volts per cell banded about as as the lowest before damaging the cells.

 

[ManTheVan]

Mine’s set to 10v too, but I wouldn’t ever want to let it get that low.

 

[jongood]

While you are on that subject, any thoughts on a battery monitor that will monitor current Lead acids and be transferrable to Lithiums at a later date please?

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[ManTheVan]

The Victron stuff is excellent, as is Sterling. There are various Chinese alternatives too, but it can be pot luck with those, as I’ve found.

 

[Two on Tour]

While you are on that subject, any thoughts on a battery monitor that will monitor current Lead acids and be transferrable to Lithiums at a later date please?

I have been using a Victron BMV 700 for a few years and when I changed over from lead acid to LiFePo4 it was just a matter of selecting the LiFePo4 from the menu, although you can alter the perimeters to suit your needs as I did.

 

[BwB]

I think 11v would be a sensible discharge cut off for 12.8v LiFePO4 "drop in" batteries.

 

[autorouter]

While you are on that subject, any thoughts on a battery monitor that will monitor current Lead acids and be transferrable to Lithiums at a later date please?

The Victron BMV monitors are top grade. There are various models, some with Bluetooth, and they have an alarm function that trips a relay, you could use it to trigger a battery cutoff. For example a Victron Battery Protect relay.

There is a cut-down version called a SmartShunt with no alarm relay, which has no display but can communicate via Bluetooth, either to a phone app or to other Victron devices.

 

[autorouter]

Deciding the low voltage cutoff value is a balance between protecting the battery against excessive low discharge and nuisance tripping due to voltage dips when a device starts up. Ideally the 10% level, about 12.0 volts, is where you would want the cutoff.

But it then depends on whether any of your loads cause a dip down to that level. You may need to set the cutoff lower. Even better would be some kind of dynamic cutoff, where the voltage has to be below the cutoff for a number of seconds, to avoid some nuisance tripping due to startup transients.

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