Battery monitor stupid question

[St3v3]

I know lead acid batteries should not be taken below 50%.

So when looking at the percentage on the battery monitor does it mean I have, say, 80% useable capacity left? Or just 30?

It's a victron bmv if it makes any difference...

 

[wildebus]

I know lead acid batteries should not be taken below 50%.

So when looking at the percentage on the battery monitor does it mean I have, say, 80% useable capacity left? Or just 30?

It's a victron bmv if it makes any difference...

The BMV shows the SOC - State of Charge (of the whole battery) - and that does not take into account what DoD - Depth of Discharge - your batteries can go to (the general default DoD for Lead Acid is no lower than 50%, but many can go to 60% without issues and there are actually some Lead Acid batteries where it is totally ok to go down to 100% DOD just like Lithiums.

So if your Battery Monitor shows 80% SOC; and you have batteries that you don't want to drop below 50% DoD, then you have used 40% of your USUABLE battery capacity. (or have 60% left, depending on how you look at it)

I did actually have a discussion about this with the Victron Technical Manager as in many ways it would be better if you could set the monitor up so the SOC was actually the usuable Battery life (based on your specific batteries) left in percentage terms for those folk who just want to look at a meter and see something like "40%" and know it means that they just have 40% of the total [available] power left to them.
But officially you can't.

(PS. the BMV has a cycle counter that ticks up each time the SOC drops to 50%. If you were to 'tweak' the settings so that the SOC was the USABLE SOC, that cycle counter would click up each time you hit 25% (real) DoD and a total discharge event each time you hit 50% (real) DoD. Doesn't really matter in many ways but it becomes harder to use the extra info the BMV can tell you)

 

[Admin]

You can set the BMV to alarm at 50%.