Carthago hab panel displays low battery 10v but shunt reading over 13v. Solar readings similar. Where to check next ?

[AdrianChen]

The Out terminal is connected to the main voltage point that distributes power from the leisure battery (B2) to all the habitation fuses. On the charging side, the split charge relay output connects to that voltage point directly. The Out terminal could be used for solar or B2B input too, or any extra outputs from the leisure battery.

The main voltage point (and the Out terminal) is separated from the B2 (leisure battery) terminal by a shunt resistor with a very low resistance. The voltages on the B2 and Out terminals should be equal. There will be a few millivolts dropped across the shunt resistor, but probably almost undetectable by a multimeter. If the voltages are different then maybe the shunt resistor has failed.

Thats worth a checking I guess - but given Mark has replaced the batteries, Solar, EHU charger, and added a B2B, all as I understand it connected to busbars, I am intrigued as to what those two cables in his photo are now connected to at their other ends, and if they are carrying any current in or out!

I think (from my dodgy memory) originally my CBE charger and solar outputs were connected to OUT, I suppose they would then share the charge to B1 (up to 6 amps was the spec), this still happens when the voltage on the Habs is over 13.5v and the panel is switched on but not when the panel is off. So I have an Ablemail.

 

[AdrianChen]

No trickle charger attached. No charger active either as i have victron inverter/charger turned off.
Regardless of a meter or panel, because the panel determines the voltage to the ALDE then i get no heating. Even if i put it on EHU the ALDE still needs 12v to fire up. So at present waste on time and money installing lithium and inverter if i can only use EHU.

Mark - I wonder if someone has been playing with your panel - or if in the past it has been replaced, but not calibrated.

It might be worth checking in the panels menu system to see if it is set so you get the same voltage as your meter reads on B2 - Not sure it's relevant to the main issue though, but I think you can go +/- 0.5v.....

 

[MarkHoughton]

Hi Adrian,
The dealer said that the “CBE” had been replaced by the previous owner, I did not have the paperwork for that though, so not aware if he meant the distribution board or the contol panel.

Anyway, as I had not snipped any R28 or R37 connections, I decided to unbolt the B2B connections from the busbars…guess what Full volts reading on HAB panel and ALDE heating up nicely this past 10 minutes !?!

So I appreciate that the B2B could create a loop “without the zero ohm snipping” but why if the engine is off ?

Though in addition prior to the disconnection just now I noticed the HAB panel was showing a steady +0.8 even though solar has been disabled all morning and ehu not been plugged in since yesterday afternoon.

I am nervous just now to snip and connect as everything appears to be working, the inverter is boiling the kettle, ALDE is heating water and bedroom.
Thoughts on next stage for the B2B ? Just realised that I had also fitted a VanBitz battery master to the B2B ( followed guidance from Offgrid Solutions ) so could this be the source of the +0.8v on the panel and trying to back feed the engine battery ?

I guess I now need to fit a relay ala Roger Ivy …

Installing a Relay alongside a DC-DC Charger — Offgrid Power Solutions

If you’re installing a DC to DC charger into a motorhome, you should consider installing a relay to bipass the existing electrical system. This article is a must-read as it explains how to install a bypass (change-over) relay alongside your DC-DC charger. It also includes a comprehensive list of com

offgridpower.solutions

 

[autorouter]

So I appreciate that the B2B could create a loop “without the zero ohm snipping” but why if the engine is off ?

A quick test to see if the split charge relay has stuck closed is to measure the voltages on the B1 and B2 terminals. If they are always the same, something is connecting them, possibly the relay stuck closed. If they are different, the relay is not stuck closed.

 

[AdrianChen]

Hi Adrian,
The dealer said that the “CBE” had been replaced by the previous owner, I did not have the paperwork for that though, so not aware if he meant the distribution board or the contol panel.

Anyway, as I had not snipped any R28 or R37 connections, I decided to unbolt the B2B connections from the busbars…guess what Full volts reading on HAB panel and ALDE heating up nicely this past 10 minutes !?!

So I appreciate that the B2B could create a loop “without the zero ohm snipping” but why if the engine is off ?

Though in addition prior to the disconnection just now I noticed the HAB panel was showing a steady +0.8 even though solar has been disabled all morning and ehu not been plugged in since yesterday afternoon.

I am nervous just now to snip and connect as everything appears to be working, the inverter is boiling the kettle, ALDE is heating water and bedroom.
Thoughts on next stage for the B2B ?

I guess it is to fit a relay ala Roger Ivy …

Installing a Relay alongside a DC-DC Charger — Offgrid Power Solutions

If you’re installing a DC to DC charger into a motorhome, you should consider installing a relay to bipass the existing electrical system. This article is a must-read as it explains how to install a bypass (change-over) relay alongside your DC-DC charger. It also includes a comprehensive list of com

offgridpower.solutions

Hi Mark - That is really odd! I wonder if the panel/DS were ever calibrated, the Amp display maybe wrong as well, although you cant alter it by much.

I agree, work out what's wrong before snipping the resistor

How did you have the B2B triggered - by D+ or voltage engine start detection? Either way it should have been off! It should not be the cause of a low hab battery voltage, because it should not pass a current the wrong way (from Hab to Cab), even if on.

What happens with the B2B connected but without the Battery Master?

I suppose it is possible that the Relay in the DS box is faulty and constantly paralleling the b1/b2 terminals - easy way for you to check is replace the b2b, but disconnect B1, the cab battery wont show on the panel, which will give an alarm/red main switch, but no current will be able to flow, your B2B should work because you have the new 25mm cable in place, as should the Battery Master.

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[AdrianChen]

Hi Mark - That is really odd! I wonder if the panel/DS were ever calibrated, the Amp display maybe wrong as well, although you cant alter it by much.

I agree, work out what's wrong before snipping the resistor

How did you have the B2B triggered - by D+ or voltage engine start detection? Either way it should have been off! It should not be the cause of a low hab battery voltage, because it should not pass a current the wrong way (from Hab to Cab), even if on.

What happens with the B2B connected but without the Battery Master?

I suppose it is possible that the Relay in the DS box is faulty and constantly paralleling the b1/b2 terminals - easy way for you to check is replace the b2b, but disconnect B1, the cab battery wont show on the panel, which will give an alarm/red main switch, but no current will be able to flow, your B2B should work because you have the new 25mm cable in place, as should the Battery Master.

Years ago on a boat an owner had turned the engine off, but left the engine control panel on, this left the battery linked to the alternator, which busied itself by warming itself up and draining the battery - I wonder if you have a similar issue, either with the main 70amp cab to hab relay, or the hab to cab link Autorouter described earlier.

Worth doing a few test, easy if you have a DC clamp meter, or a warm alternator!

 

[MarkHoughton]

Years ago on a boat an owner had turned the engine off, but left the engine control panel on, this left the battery linked to the alternator, which busied itself by warming itself up and draining the battery - I wonder if you have a similar issue, either with the main 70amp cab to hab relay, or the hab to cab link Autorouter described earlier.

Worth doing a few test, easy if you have a DC clamp meter, or a warm alternator!

No clamp meter and no warm alternator either as indoors now as the rain has arrived. Having read the instructions from Roger Ivy's webpage above I ordered the relay he suggests, so Amazon will deliver that tomorrow. I did not want to dis-assemble the cables from the B2B/Battery Master as it was a fiddly job to get them in whilst on the "mounting board" on the kitchen worktop. Would involve removing all of that to access again, so parking that suggestion for now.

B2B is to be activated by engine start voltage as I have not determined where the D+ is, so will visit that along with the Amazon relay.
For now I am happy at least that I have a functional habitation area. Had planned to get away to Northumberland this coming weekend, so will hopefully get it resolved by then.

 

[AdrianChen]

I think your D+ is the grey cable coming out of the 4 way connecot near the middle of the board. if 0v when engine of and 12v+ when running its that one. Miine was not connected to anything, and so I used that cable!