Victron Multiplus SoC at 22%, what should be happening?

[The Brockerts]

I've got a Victron Multiplus 12/3000/120 unit on 2 8D Batteries. The Victron tells me the SoC is at 22% and the voltage is 12.80. The batteries have a battery charger on them that sits in float mode all the time.

My volt meter tells my voltage is 13.4

If the SoC is that low shouldn't the battery charger kick in more?
Victron says the the voltage at 12.8, thats different than a volt meter at 13.4!?

Some tells me the math doesn't add up or something is wrong, or I just don't understand how all this is works.

Float batteries are 18 months old

The Brockerts

 

[rslifkin]

If there's anything that adds or removes power from the batteries other than the Multiplus, you can't use the Multiplus SoC meter and expect it to be accurate. If you want an accurate reading, you need an external monitor with a shunt that sees all power going in and out, like a Victron SmartShunt or BMV.

 

[mvweebles]

Do you have any other charging source such as solar? My magnum inverter seems to do a mass balance calculation - amps in vs amps out. I need to check my grounds as clearly not everything is being accounted for.

Odd as it may sound, you may want to count noses on all ground cables and make sure they are going through your shunt. That's the most common reason for an imbalance

Peter

 

[twistedtree]

All the above is good advice regarding the SOC % being off. But the voltage reading is another issue. Unfortunately a lot of volt meters are pretty poor, but thankfully many are adjustable.


Where is the Multi reporting 12.8V? Do you have some sort of display, or is that based on the LEDs on the front panel? If the LEDs, I would take them only as a "suggestion" about what the voltage might be.


And when you say your meter reads 13.4V, what is that meter? Some sort of panel display, or a hand held VOM?


Also, is the remote voltage sense on the Multi connected directly to the batteries (with a fuse)?

 

[MacPhid]

If the battery bank's parameters have not been programmed into the meter (Ahrs capacity) the SOC could be off. 22% reported at 12.8v seems a lot, but combined with unaccounted grounds etc could contribute to the cause.

James

 

[The Brockerts]

Lots of good information.

- Probably most of my DC does not go through the Inverter. And once I’m off of shore power my DC, non inverter usage goes up even more. That’s why I’m seeing SoC change so much will cruising.
- All charging is from external sources so the Multiplus doesn’t see any of that. The boat came with a charging systems for both banks and I keep is running. The Multiplus does have a charger but it’s on there for backup.
- The Multiplus meter voltage is read via an iOS app connected to the the Multiplus via bluetooth so I assume it’s reading as a directly connected to the batteries that is fused.
- I use a handheld VOM and test right on the battery terminals


I’ll play around once I’m back in port and see if I can get it to a usable number.

THANKS !

 

[DDW]

Use the same VOM and test right at the Multiplus DC terminals.

 

[twistedtree]

Is it a multiplus II? I don't think the original Multi has bluetooth.

 

[READY]

One other suggestion is to turn off all charges and disconnect the battery and then measure your battery voltage. Now selectively restore any connections and record the voltage readings for each. This can minimize variables/confusion about true voltages.

SOC readings confuse a lot of people. Essentially it is only accurate if it "knows" that the battery is full (100%) AND it counts all current in and out of the negative battery post AND it knows the total battery capacity (amp hours). If any of these are incorrect the SOC value is meaningless.