Using BMV-712 to measure SOC of series connected batteries which are charged INDIVIDUALLY.


I am planning to use a BMV-712 to monitor the SOC of two Battle Born 12-volt Li batteries connected in series to run a 24-volt trolling motor. The batteries are charged individually by 12-volt chargers.

I can find multiple diagrams for using a BMV-712 to monitor:

12-volt batteries wired in parallel, and charged separately,

6 volts in series to make 12 volts and charged with one 12-volt charger.

6 volts in series to make 12 volts, with several connected in parallel to increase capacity.

This is what I have in my travel trailer, which is charged through the trailer system, or can be switched to be charged by a Sterling 60-amp battery to battery charger I can connect to the truck with an Anderson connector. This is monitored with BVB 712.

What I do not find is how to use one (or two) BMV-712’s to monitor series connected batteries being charged individually.

My thinking is this:

I have 12-volt batteries A and B connected in series to yield 24 volts.

Both batteries A and B are charged individually.

Connecting to measure both batteries:

If I connect the BMV shunt between the negative terminal of battery A and the trolling motor, the shunt will detect the energy supplied to the trolling motor by BOTH battery A and B, but will only detect the energy charging battery A. With each use and charge, the calculation of the SOC will be off by 50%. The only ways I can think of to compensate for this is to adjust the peukert exponent to be about .52, or the charging efficiency factor to about 200%. The ranges shown in the manual do not include these drastic settings so I doubt either is possible.

Connecting to measure ONE battery of the pair.

If I connect the BMV between battery A and B the shunt measures the current flowing from battery B to battery A. When charging, the shunt will measure the energy used to charge battery B. The SOC should be accurate for battery B. Batteries A and B are “matched” per Battle Born- and under the same load from the trolling motor, so the SOC of A should be very close to battery B.


Is there a way to measure the SOC of both batteries?

Is there a better way to measure the SOC of one of the batteries?


The rest of the story:

I have two Battle Born 12-volt 100 AH Li batteries connected in series to produce 24 volts to run a trolling motor. The batteries are charged individually by two different systems. The primary means of charging is a Dual Pro charger (15 amp per battery) The batteries will also be charged by a Minn Kota MK-2-DC onboard alternator charger. Its output is up to 10 amps per bank with a 25-amp alternator, but my outboard only puts out 20 amps.

It would have been simpler to have two 24-volt Li batteries in parallel charged by 24-volt chargers- but that is not what I have…


hednout asked
Kevin Windrem answered ·

1 Answer

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Guy Stewart (Victron Community Manager) commented ·

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ianwhite16 asked
ianwhite16 commented ·

1 Answer

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I have not received the verification email to complete my registration for VRM and there is no option to resend it. Could someone please assist ?



byron asked
Teun Lassche (Victron Energy Staff) commented ·

2 Answers

Error Message: 'Incompatible VEBus configuration' Error: mk2vsc-61

I commissioned a 135kVA (9 x 15kVA) system on Friday and am trying to adjust settings but getting this error when trying to download configuration:

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I see there is something in Gitmemory about this being an issue > 6 units but it seems solved: https://www.gitmemory.com/issue/victronenergy/venus/758/743233338

warwick asked

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Victron enthausiats,

Almost every time I start the main engine of my boat, I get an alarm or warning for Low Battery, sometimes also for DC ripple.
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harold asked

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I have a Multiplus 24/5000/240 and an Autotransformer. According to the Autotransformer manual the Relay is 12 V, and the output voltage of the Multiplus/Quattro is also 12V regardless of the DC Voltage of the Inverter. Here is what it says in the manual

When the Internal ground relay is not selected in VE Config or Victron Connect, there is 12V on the external terminal of the Multi/Quattro for the ground relay control (on all models 12/24/48V this voltage is 12V).

However if I measure the voltage I get the DC Voltage of my system (in my case 27V) and not 12V. I am afraid this will burn out the coils on the Ground Relay in the Autotransformer.

mfriedel asked
mfriedel answered ·

2 Answers

VRM Dashboard new thing " Time To Go " under Battery section ? , appeared and vanished

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Hi


Just noticed this today , appeared and disappeared within a minute.

Anyone know what that is relating to ?


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teloth asked
harold commented ·

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Tim Chapman asked
1point3liter edited ·

3 Answers

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Hey there, as I commented on the blog post,

"I'm curious if future versions will have VE.Direct or some sort of integration like that with GX devices? Currently, it seems that the MPPT and MultiPlus are able to coordinate their total charge rate with external BMS via the GX devices. But it seems that the Orion-Tr does not participate in this?"

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Now I'm considering purchasing Orion-Tr Smart chargers, however I noticed that they don't have any VE.Direct connectivity, or any other VE connectivity aside from the Bluetooth one. Is something like VE.Direct, VE.Bus or VE.Can planned? Will Orion-Tr Smart chargers integrate with GX devices?

aybabtme asked
cwoody answered ·

12 Answers

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Obviously a newby here, I have 28 390 W Canadian solar panels and would like to know if I can connect them to my smart solar MPPT 250/100 in 7 strings of 4 connected in series.

The Isc is 10.17 A

Voc 48,2 V

Hannes Swart asked
JohnC commented ·

2 Answers

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I now have 2 x 250/100 MPPT's that I have connected 28 x 390W panels 4 in series and 7 strings, 4 strings to one and 3 to the other. My question is why at peak hours am I only producing 6500W?

I have a Freedom Won 30/24 LifePO4 battery connected as well as a generator on remote start

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Hannes Swart asked

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jh8001 asked

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Do I need a transfer switch if the genset is connected to ac-1 input on both quattros?

I would like to wire the quattros with each leg from genset to each Quattro along with each leg from shore power to each Quattro.

just want to make sure the transfer switches in the quattros can handle the transfer between shore and genset without an external transfer switch…

thx for any input

Geoffrey Schwark asked
Geoffrey Schwark answered ·

2 Answers

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Hi,

I have just installed new Victron gear and im not sure what settings i should have for everything.

I have the Smart Shunt, Mppt 100/30 controller, Dc12/12/30 charger and the IP22 12/30 chager 3 ports.


I have 2 Ritar 120 AH AGM bateries connected for a 240AH total.


Which profile should i select for these batteries and are there any other settings i should change?


Thanks

destrvction asked
destrvction commented ·

1 Answer

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paulcooper asked
Ingo commented ·

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Regards

bertie-bezuidenhout asked

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Hat jemand schon eine kleine Autark-Lösung für Wohnwagen realisiert. Im Wohnwagen ist eine Schaudt CSV300 installiert, Ich möchte nicht die Schaudt CSV409 einbauen.


Mit freundlichem Gruß


Wilfried Wendland



ballonwilli asked

0 Answers

smartsolar 100/20 load switches off in float mode

I have noted several people have problems with load switching off eg fridge.

So am testing with a simple halogen lamp which draws 4.5amps. The lamp will stay on in bulk and absorb mode but turns off in float mode. It works fine with no pv panel at all (draws power from battery through reg) but will not turn on in float mode when pv is connected??

Is this a software fault, I am using f/w v1.37

ray-pridham asked
bazbrush edited ·

11 Answers

Difficulty with MPPT100/30 + 305W solar

Hi there,

I got a Victron 305W Solar panel and smart solar MPPT 100/30 installed by a mechanic in my van but I feel like it's not working appropriately.

The Mppt is connected directly to the batteries (2x100Amp in series) (positive on first battery, negative on second). Theres a fuse breaker between mppt and batteries.

My problem is that the app always shows float, no matter how much I've used my fridge, lights etc. It also shows immediately whatever voltage I put in the battery settings. So If I change the battery voltage to 14.0 it just jumps to it without ever entering "bulk" mode. Lastly my wall voltmeter (I know it's not fully accurate) keeps dropping during the day and night.

Not sure if it's important but I also have a split charge relay to charge the batteries while running the engine. So when I drive for a while and stop my wall voltmeter shows 12.8V while the victron app doesn't show a higher voltage. When the engine is running the app is jumping all over the place showing battery voltages between 4 and 15 and going between float, bulk and absorption.

I would really appreciate any help.

Thank you in advance.

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iris123 asked
iris123 answered ·

2 Answers

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codydog asked
jperez (Victron Energy Staff) answered ·

1 Answer

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tilapia asked
gro edited ·

3 Answers

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trwr321 asked
gro edited ·

1 Answer

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Hello

I was recently gifted a VICTRON Blue Smart Battery Charger 12V 30A IP22 (3) Outputs to replace an old Euro style charger for my caravan.

Unfortunately, the gift did not include a lead to connect from the Charger screw terminal (AwG6) to my battery. I would prefer a lead without clamps.

All I can seem to find is IP65 accessories.

What lead do I need to go from the IP22 to the battery?

caittravels asked

0 Answers

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Any thoughts?

David asked
Guy Stewart (Victron Community Manager) answered ·

1 Answer

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BMS assistant installed in Multiplus.

At first startup, I am getting a low battery led on the Multi, even though voltage across the multi's battery terminal shows 14.5, and the Multi is stuck in Passthru mode.

No charging and no inverting functions.

The BMS V+ voltage is 14.6, but the Load Disconnect and Charge Disconnect outputs are low, 0V.

Is it possible the BMS is defective? How would I bench test the BMS.

There was a Cerbo in the system, but it is disconnected at the moment.

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jerrykeefe asked

0 Answers

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What exactly is the warranty when you buy Victron products? Is there a link to "the fine print"?


Has anyone had to claim a warranty for a component that stopped working? If so, how was the process. Did you have to ship the component somewhere? Who paid for that?

agroventuresperu asked
Vance Mitchell edited ·

4 Answers