Issue with new dual battery setup - reading 24v?? (1 Viewer)

[NearJetties]

Hi,

I just finished setting up my new dual battery system.

Something bizarre is happening.

Readings:

13.1 volts across battery terminal
13.1 volts at all points on the smart battery monitor. Smart monitor app reads 13.1 volts

….then it’s showing 24 volts (WTF) at the chassis ground which comes off the smart battery monitor.

And also 24-25v at the 12v power socket…wtf.

I disconnected the redarc bcdc to isolate it. When I had it connected and the vehicle running it the Lithium profile light was blinking indicating no charging/standby. Is that because the battery is fully charged?

Charge lights on the bcbc never came on

Battery: Dakota lithium lifepo
Redarc 1240d bcdc
Redarc smart battery monitor
Redarc bcdc wiring kit

Cc: @emorth

*not everything is secured at the moment because of testing/troubleshooting

 

[e9999]

how did you wire the batteries? Seems like they are in series someplace?

 

[NearJetties]

how did you wire the batteries? Seems like they are in series someplace?

Like this (no solar input at the moment):

The the chassis ground on the auxiliary battery has this added in line:

I’ve double checked the install and these readings were with the bcdc disconnected from the aux battery so the start battery is also disconnected.

The readings at the redarc terminal block were also 13.1v

https://cdn.intelligencebank.com/au/share/yE9N/zJpl/6geNM/original/BCDC+Wiring+Kit+Instruction+Manual+English

 

[emorth]

Agree. Seems like a series circuit.

Confirm the ground connections and aux battery connections.
If the output of the converter goes to the negative post on the auxiliary battery without a ground connection then you have 12v coming out of the converter plus the 12v from the aux battery which gives you the 24v from the aux positive terminal to the chassis ground.
Just a thought

 

[NearJetties]

Got it, I’ll try adding another ground from the auxiliary negative battery post to the chassis. I thought the single one with the smart monitor would be enough but maybe not.

Although I’m still confused how I’d get series with this disconnected:

 

[NearJetties]

@e9999 @emorth running another ground from the neg aux battery to the chassis fixed it! Thanks gents!