Battery Voltage

[Buddy1012]

Just getting used to new set-up, lithium plus new inverter/charger, additional solar, plus a battery master for the starter battery. All working well it seems however I am getting a discrepancy with the starter battery voltage. On my app for the Scorpion Tracker it is always between 12.7 and 12.9 volts, whereas a reading directly off the +ve and ground connections on the input side of the New DC2DC is usually around 12.3 volts. If I go to the Schaudt panel it is usually showing just one of the green LEDs ie somewhere around 12.2 volts.

For information the EBL no longer provides any of the charging functions and the fuse has been removed from the original booster circuit (EBL side 80 amp fuse) although I cannot locate the 70 amp one that is supposed to be next to the starter battery.

Is the voltage discrepancy something that I should be concerned with or should I just accept that if it works then all is okay?

Any advice / comments / suggestions appreciated!

 

[pappajohn]

If the starter battery is accessible put a multimeter on the terminals.
That should give an accurate voltage.....electronic panels can vary

 

[fred_jb]

Just getting used to new set-up, lithium plus new inverter/charger, additional solar, plus a battery master for the starter battery. All working well it seems however I am getting a discrepancy with the starter battery voltage. On my app for the Scorpion Tracker it is always between 12.7 and 12.9 volts, whereas a reading directly off the +ve and ground connections on the input side of the New DC2DC is usually around 12.3 volts. If I go to the Schaudt panel it is usually showing just one of the green LEDs ie somewhere around 12.2 volts.

For information the EBL no longer provides any of the charging functions and the fuse has been removed from the original booster circuit (EBL side 80 amp fuse) although I cannot locate the 70 amp one that is supposed to be next to the starter battery.

Is the voltage discrepancy something that I should be concerned with or should I just accept that if it works then all is okay?

Any advice / comments / suggestions appreciated!

Are you sure that the Scorpion tracker is not connected to the leisure battery rather than the starter battery? If so it could explain the higher reading. My starter battery is topped up from the leisure battery by an Ablemail unit and sits at about 12.4-12.5V whereas the lithium leisure battery is at about 13.4V

 

[AdrianChen]

Our Scorpion app reports the voltage at around midnight - it is normally 0.18v above the Victron B2B reported figure. The connection from the start battery to the B2B runs through a couple of Iveco fuse panels, a midi fuse 9m of cable, the return through a busbar, to the chassis.

The Victron figure and the Ablemail trickle charger are connected at the same point, but the Ablemail reports 0.02v higher than the Victron figure. But still pretty close.....

The CBE main panel on ours is adjustable, so no good as a reference.....

I suppose we loose a little from a substandard connection/ground or fuse along the run, and one day I may look for it, but I don't know how good or bad the Scorpion voltage report is, since I haven't directly measured the battery recently.

Your start battery voltage at 12.7-12.9v seems appropriate given you have a Battery Master, but a difference that size may indicate something is loose, etc. 0.6ish is quite a lot with only low currents running

I think I would look to see if there is a larger drop across the system when the B2B is going at full tilt since any shortfall in the fuses and connections will show up more when a large current passes through, even just checking for a hotter element than the others.

 

[autorouter]

The general principle is that you should only get a voltage drop along a cable if there is some amps flowing through it. The more amps, the higher the voltage drop. If the amps value is very small, then the voltage drop should be very small too.

A voltage drop of 12.7-12.9V down to 12.3V is too large to be explained by cable thickness or connections that are OK but not perfect. Maybe the calibration of the measuring device is suspect. You should put a multimeter on the exact spots that the Scorpion Tracker is using, to see if you get the same result. I know the multimeter calibration may not be spot-on, but I've never come across one that is out by more than 0.1V compared to a certified calibrated bench meter. If the multimeter agrees with a second multimeter then I would trust that over any other measuring device like a tracker or a control panel reading.

Can you access the batteries to take a reading direct from the terminals?

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[Buddy1012]

Are you sure that the Scorpion tracker is not connected to the leisure battery rather than the starter battery? If so it could explain the higher reading. My starter battery is topped up from the leisure battery by an Ablemail unit and sits at about 12.4-12.5V whereas the lithium leisure battery is at about 13.4V

Definitely to the SB as without the master in place or an alternative eg solar charger it discharges pretty quickly. Your readings are not dissimilar to mine to be fair - today LB at 13.2 with SB at 12.3 (directly off the terminals).

 

[Buddy1012]

The general principle is that you should only get a voltage drop along a cable if there is some amps flowing through it. The more amps, the higher the voltage drop. If the amps value is very small, then the voltage drop should be very small too.

A voltage drop of 12.7-12.9V down to 12.3V is too large to be explained by cable thickness or connections that are OK but not perfect. Maybe the calibration of the measuring device is suspect. You should put a multimeter on the exact spots that the Scorpion Tracker is using, to see if you get the same result. I know the multimeter calibration may not be spot-on, but I've never come across one that is out by more than 0.1V compared to a certified calibrated bench meter. If the multimeter agrees with a second multimeter then I would trust that over any other measuring device like a tracker or a control panel reading.

Can you access the batteries to take a reading direct from the terminals?

Just done it (nothing relating to base vehicle is ever accessible in an A Class is it) SB at 12.3v so it is the Scorpion reading which is the flaky one it seems.

 

[fred_jb]

Not sure what you are getting at? I was just suggesting that the tracker may be powered from the leisure battery in which case I assume that the leisure battery voltage would be the voltage it reported. The 12.9V reading could then be just a slightly low reading of that rather than a very high reading of the starter battery.

 

[Buddy1012]

Not sure what you are getting at? I was just suggesting that the tracker may be powered from the leisure battery in which case I assume that the leisure battery voltage would be the voltage it reported. The 12.9V reading could then be just a slightly low reading of that rather than a very high reading of the starter battery.

Maybe crossed wires? Excuse the pun. Wasn’t getting at anything just confirming that in my case it is on the engine (starter) battery. I think I’m there now - checked actual battery with 2 MMs & concluded that the Schaudt panel is more or less accurate & that the tracker one is the erroneous one which I can live with as in the two and a half years I’ve had it, this week was the first time I actually took any notice of it.

 

[AdrianChen]

Just done it (nothing relating to base vehicle is ever accessible in an A Class is it) SB at 12.3v so it is the Scorpion reading which is the flaky one it seems.

Was the battery master connected/running?

Good to know the tracker asn't great. I can put off checking now!

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[Buddy1012]

Was the battery master connected/running?

Yes - red light confirming trickle from LB to SB as it should be. I think I’ve only ever seen it green once and for a few seconds at that. This time of year, no EHU (no need) and virtually no solar I would think that’s always going to be the case unless of course engine is running

 

[AdrianChen]

Yes - red light confirming trickle from LB to SB as it should be. I think I’ve only ever seen it green once and for a few seconds at that. This time of year, no EHU (no need) and virtually no solar I would think that’s always going to be the case unless of course engine is running

OK - Though it might be higher with the BM running, but pretty sure you've cracked it....

 

[Buddy1012]

OK - Though it might be higher with the BM running, but pretty sure you've cracked it....

I did actually - sort of 12.5 upwards which it always seemed to be. Just have to monitor it as we go. At the moment I have taken the +ve LB feed off the EBL 12v connection which is a 5m run of 25mm2 cable. This may be an explanation? If so I can remedy this by going all the way back to the actual batteries instead. I did it this way for expediency and just to tidy things up.

 

[fred_jb]

Maybe crossed wires? Excuse the pun. Wasn’t getting at anything just confirming that in my case it is on the engine (starter) battery. I think I’m there now - checked actual battery with 2 MMs & concluded that the Schaudt panel is more or less accurate & that the tracker one is the erroneous one which I can live with as in the two and a half years I’ve had it, this week was the first time I actually took any notice of it.

It's just that I wasn't sure of the relevance of your comment about the SB discharging until reading again just now. I guess you are saying that because the SB discharges quickly without EHU or solar then you are assuming that the Scorpion must be powered from the SB. A reasonable assumption I suppose, but it could be something else draining the SB, as trackers should only take a fairly minimal current.

It might be a reasonable idea in a camper to run alarms, trackers and other such always on stuff off the leisure battery rather than the starter battery as the former tend to have more capacity, and in vehicles with smart alternators and a B2B, the leisure battery is generally maintained in a higher state of charge than the starter battery.

 

[Buddy1012]

Just done it (nothing relating to base vehicle is ever accessible in an A Class is it) SB at 12.3v so it is the Scorpion reading which is the flaky one it seems.

Just getting used to new set-up, lithium plus new inverter/charger, additional solar, plus a battery master for the starter battery. All working well it seems however I am getting a discrepancy with the starter battery voltage. On my app for the Scorpion Tracker it is always between 12.7 and 12.9 volts, whereas a reading directly off the +ve and ground connections on the input side of the New DC2DC is usually around 12.3 volts. If I go to the Schaudt panel it is usually showing just one of the green LEDs ie somewhere around 12.2 volts.

For information the EBL no longer provides any of the charging functions and the fuse has been removed from the original booster circuit (EBL side 80 amp fuse) although I cannot locate the 70 amp one that is supposed to be next to the starter battery.

Is the voltage discrepancy something that I should be concerned with or should I just accept that if it works then all is okay?

Any advice / comments / suggestions appreciated!

Further to this and the hints / suggestions which followed (thank you!)
Checked today - leisure battery at 13.1 volts starter battery on the actual terminals is 12.3 volts (2 x multimeters). Observing the set-up BM kicks (red light) below 12.3 and stops (green lights) once it is back to 12.3. All connections appear sound and whatever the voltage it seems to be working (always starts at 1st turn etc).

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[Ingwe]

Accessing the cab battery terminals directly is a pain. Is using the points provided for jump starting the van, under the bonnet, acceptable for taking cab battery voltage readings?

 

[Buddy1012]

Accessing the cab battery terminals directly is a pain. Is using the points provided for jump starting the van, under the bonnet, acceptable for taking cab battery voltage readings?

That’s what I do for occasional checking but after first of all comparing the two just to check whether any variance between the two. In my case there wasn’t.