Battery Voltage discharging to low but Battery Percentage staying at 100%.

oliverbunyan

New Member
Hi all,

I've recently come up with both an issue with my Renogy Lithium 100aH battery. My battery has once been discharged to flat and this way months ago. Apart from that it merely drop below 95% over night. Running my fridge constantly and then re charging the next day via my victim dc-dc charger and the solar when I use it to drive to work etc.

All of a sudden my inverter has been bleeping into a fault when turning my engine on. I've noticed that my battery has been discharging down to as low as 10.5V when the vehicles idle, then the voltage level spiking back up when the engine turns on and the dc-dc is imagine is kicking voltage into the battery.

This is becoming an issue as when I'm staying in the van, the voltage levels dropped to low for me to use my sink etc and I'm going to Europe for 2 weeks in the van in 2 weeks time and now I'm thinking there's no way of my recrifying the battery in this duration.

Has anyone come across this issue and how it can be rectified. The voltage levels are dropping as low as the voltages would drop at 0% but being a 100% battery.

Quite concerned.

Thanks in advance to any responses

I've attached images below showing the voltage spike when the vehicles turned on and also showing the low voltage while the % was at basically 100%. I'm thinking the battery is broken feel like all this started happening with the warm heat.

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It's been fine and showing 13v for a few weeks. Not being used for anything other than some LED spotlights.

I've just connected the charger up to the starter battery and ran it for a few mins. Back up to 12.9v now.

Checked connections and all look ok.
 
Also noticed that without connecting the ignition live, it would charge the leisure battery.

I thought that had to be connected?
 
Also noticed that without connecting the ignition live, it would charge the leisure battery.

I thought that had to be connected?
No, when the starter battery voltage is high enough, the Dc-Dc charger will kick in.
 
Hi all,

I've recently come up with both an issue with my Renogy Lithium 100aH battery. My battery has once been discharged to flat and this way months ago. Apart from that it merely drop below 95% over night. Running my fridge constantly and then re charging the next day via my victim dc-dc charger and the solar when I use it to drive to work etc.

All of a sudden my inverter has been bleeping into a fault when turning my engine on. I've noticed that my battery has been discharging down to as low as 10.5V when the vehicles idle, then the voltage level spiking back up when the engine turns on and the dc-dc is imagine is kicking voltage into the battery.

This is becoming an issue as when I'm staying in the van, the voltage levels dropped to low for me to use my sink etc and I'm going to Europe for 2 weeks in the van in 2 weeks time and now I'm thinking there's no way of my recrifying the battery in this duration.

Has anyone come across this issue and how it can be rectified. The voltage levels are dropping as low as the voltages would drop at 0% but being a 100% battery.

Quite concerned.

Thanks in advance to any responses

I've attached images below showing the voltage spike when the vehicles turned on and also showing the low voltage while the % was at basically 100%. I'm thinking the battery is broken feel like all this started happening with the warm heat.

View attachment 254552

View attachment 254553

View attachment 254554

View attachment 254555

View attachment 254556

View attachment 254557

View attachment 254558

View attachment 254559

View attachment 254560

View attachment 254561
Are you leaving your inverter switched on when not in use? I.e is the inverter permanently connected to the battery, even when not being used?
 
Can you get a better pic of the shunt connections and the battery neg post,
And neg busbar. And neg to chassis connection.... Pls.

Yeah will do.

Shunt is Batt Neg -> Shunt -> Fusebox BusBar
Then the smaller positive feed direct to the Batt Pos.

Battery has a neg direct to the seat base bolt closest to the B-Pillar.
 
Yeah will do.

Shunt is Batt Neg -> Shunt -> Fusebox BusBar
Then the smaller positive feed direct to the Batt Pos.

Battery has a neg direct to the seat base bolt closest to the B-Pillar.
That will be you're problem..

The ONLY connection to the battery Neg post should be the shunt. (Not shunt & seat base)

You need to move that main battery neg to seatbase bolt to the other side of the shunt.
 
I'll get that moved, cheers!

So would that have caused battery drain?

The monitor and the charger were indicating low voltage
 
The shunt won't see the power in and out of the battery..... That's why the soc didn't change.

You run the battery flat without knowing.

The battery will need a full charge to 100% to calibrate the shunt.
 
What should my charger settings be?

The parameters for the battery below don't match the settings I have for the charger.

Screenshot_20250529_172805_Drive.webp
 
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