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silverms avatar image
silverms asked

Can the 712 monitor 2 different battery types?

I just got the BMV 712. I'm in the processing of wiring everything up. I have a Lead Acid battery for my pickup in the engine bay. I have a 100mA lithium in the bed as my auxiliary. So my question is can the 712 monitor BOTH batteries or do I need to pick one? It shows a diagram for 2 batteries in the installation but I could find nothing on monitoring 2 different types of batteries. I have the shunt installed between the battery and my dc fuse panel before heading to chassis ground. Would it be fine to have the battery in the engine bay to chassis ground rather than connecting to the shunt and use a bunch more wire? Any help would be appreciated. See the picture on how I planned my system. I don't show the 712 connected to the starter battery since I wasn't sure if it could work.

installation
20191106-222848.jpg (1.6 MiB)
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klim8skeptic avatar image klim8skeptic ♦ commented ·

Hi Silver,

You have 1 small error. The negative of the inverter has to be on the Load side of the bmv's shunt.

You can use the bmv's second input to measure the battery temp, or the starter battery voltage, not both.

Dunno much about the Ctek 25000, is it suitable for lithium?

I cant work out what the Blueseas 9009 is for. A mains/inverter change over switch?

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silverms avatar image silverms klim8skeptic ♦ commented ·

I'm not sure what you mean by the load side. Are u saying connect to the negative of the inverter to the shunt side between the dc panel and shunt? So basically I should just get rid of the second wire going to the engine bay if it only tells me volts and nothing else? I could care less about the temperature since the redarc acts as a isolator so it won't be an issue in temperature up there.

Yes the Ctek is fine for lithium.

The 9009 is a 2 way switch. So when I'm plugged into shore power I can select if I want straight AC going into the AC Panel powering the system OR switch to the DC side (check ac to dc battery charger) to charge the battery or I can even set the ctek to a power supply and supply straight DC to the panel while doing a maintenance charge to the battery. This schematic I threw together so I didnt screw up when wiring.

The pickup will be wired for everything regardless if it is running off the alternator, solar, shore, generator. Figured if I was putting an inverter in I might as well install everything.

I'm mainly in need of figuring out the victron setup since everything else will be fine.

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silverms avatar image silverms silverms commented ·

Nice thing about the battery I got it has a built in readout so it may help me troubleshoot if this inverter is in the wrong location giving a different reading than the 712

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klim8skeptic avatar image klim8skeptic ♦ silverms commented ·

Hi Silver,

"I'm not sure what you mean by the load side. Are u saying connect to the negative of the inverter to the shunt side between the dc panel and shunt?"

That's right, that way the amps the inverter uses is counted by the bmv, and the battery soc is right. https://www.victronenergy.com/upload/cache/1498571568_upload_documents_1600_640-Shunt_300dpi.jpg

Shunt photo.



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silverms avatar image silverms klim8skeptic ♦ commented ·

Got it. TY.

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JohnC avatar image
JohnC answered ·

Hi Silver. Best to apply the BMV shunt to the batt you're 'cycling'. Normally the engine batt would be left alone and used only as a starter unit.

The BMV has an 'auxiliary' functionality though, and can be used to monitor the V of the engine batt as well. That's a thing with a choice of one of 3 options, but if you don't need batt temp or bank midpoint V, then use it as a V monitor of your engine batt.

And oh, your diagram has the shunt in the wrong place - the inverter -ve wire should be going through it too.

And for fun, look through the Victron display van install. Even with every gizmo known to mankind included, they still leave the engine batt as a no-touch-mission-critical item. They chose a different aux function, but could have done otherwise.

https://www.victronenergy.com/blog/2019/06/18/the-victron-van-install/

Edit: Posted before seeing the other comments, but left unchanged.


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silverms avatar image silverms commented ·

Thanks John it is starting to make sense now. I will make sure I put the neg of the inverter after the shunt coming off the battery. Though I may have to change the 6awg to 0awg to reflect the change and still eliminate most voltage drop from the battery to the inverter.

I will not even bother monitoring the battery in the engine compartment.

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silverms avatar image silverms silverms commented ·

Here is a revised version. Is this where the negative should go?

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JohnC avatar image JohnC ♦ silverms commented ·

Yeh, that's the one. Can't speak for the rest of your system (unfamiliarity), but the BMV shunt needs it that way.

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