Which one is in trouble ?

[RRRRRRRRRRudy]

I recently entered my rv in the garage. He's been there for about a month. So it is not connected to the shore and for recharging with the sun ... well it obviously does not work.

Yesterday I entered the rv and as I usually do, I connect to my BMS Daly to see the battery status. It is 89% and the voltage is 11.8 volts. Suddenly everything turns off and nothing more works in the rv.
However, I made the adjustments on the BMS as indicated by my salesperson BUT I have doubts.

I panic a bit and plug the rv into the shore to recharge the battery.

So: is it normal to have an 89% battery BUT such a low voltage?

 

[MichaelK]

Were there any loads on the battery as you were reading the voltage? Voltage is a notoriously poor indicator for the state of charge. After fully charging, I'd disconnect everything and test the battery after it's been just sitting there resting. This is more a truism for lead-acid than Li.

 

[Struc]

Capacity indicator not properly reading small loads?

 

[chrisski]

I have seen similar with my RV when stored for 2 months with the solar off, but with FLA. Would be interesting to see what others have seen with Lithium.

====================
Had FLA batteries with a Victron Shunt Attached and ither than that, the battery disconnected from the system. After this two months SOC was 60%, even though the Battery Monitor read 100%. I charged the batteries and they took 40% of the power.

Two things happened in my case:

1) THe FLA batteries naturally discharge. This would not apply to you with Lithium Batteries.

2) The shunt draws power that does not get registered in the battery meter. My Victron says it is a low draw 5 mv and compares this to most other shunts that are 50 mv, and then showseven though its a minuscule load, how over several weeks this can drain a battery. My assumption is a BMS has some draw that can add up that may bypass its own current reading for SOC.
===================
Do you have a way to measure any parasitic draw? I have ad problems with cars in The past. A Clamp type ammeter can make measuring easier.

 

[RRRRRRRRRRudy]

Thank you all for your reply.

I just did the parasitic draw and it is .35amp So for about a month 24 hours a day it drawn a LOT of amps and like you wrote, the BMS just did not add up htat really small charge.

I know what I have to do now. If I have to put my rv in the garage for a long period of time, i will open the breaker.

Thanks again

 

[time2roll]

So: is it normal to have an 89% battery BUT such a low voltage?

Does the Daly BMS have a provision to reset charge level based on voltage?
My Overkill does but I am not sure if or how it really works.