We have an older Hatteras yacht with a 32v electrical system. There are two banks of 4ea 8v batteries. Each bank serves as a starting bank for the 12-cylinder engine on that side of the boat. Additionally, one of the banks serves as the “house” bank for DC loads. All charging is handled via a Sterling Power AC to DC charger. I would like to install a shunt on the bank that handles house loads, but I’m unsure how to do the since it also handles starting the engine, which is in the neighborhood of 1000A when it happens. I see the Lynx system has a 1000A fuse…would that be a good starting place?

Hi @adt2 If you’re talking just a Shunt (rather than a ‘bms’), then many of the Victron shunts come with a range of Amp choices. An example… https://www.victronenergy.com/upload/documents/Datasheet-SmartShunt-EN1.pdf The Lynx unit is really designed to fit within the Lynx wiring system, and may not suit what you want to do. See the full range on the Victron website. Look under Battery Monitors, but they can be set up as plain meters too.

If you want to monitor currents only for the house loads section, then install the shunt only “towards” that part of the circuit, without including the starter after it. The starter will take its negative directly from the battery - and before the shunt - as it is now.

Actually, on both sides, the batteries connect directly to an ancient dual battery switch and then run to the starters and other loads. It’s kind of a big scary looking piece of kit, and even when the switches are off there’s still a few things that get DC power - which is one of the things I’m trying to decipher. I assume the easiest solution is to install a new switch and shunt between the batteries and the existing switch gear, but I’m not sure how I’d break out the starter functionality.

Found some diagrams I did a while back while noodling on this issue…maybe these will help. [SCR-20240921-fkcz] [SCR-20240921-fkiv]

Someone elsewhere suggested a modification to my proposal…still looking for some feedback from Victron peeps. [IMG_3383]

The shunt needs to be directly between the battery and the busbar. Otherwise the shunt won’t “see” the current that the engine needs to start and also not the energy that’s coming from the alternator (if there is one).

I may be wrong, but maybe he wants to monitor only the house loads… [image] Andrew Taylor: I would like to install a shunt on the bank that handles house loads

Alex is correct. I don’t really think I need to monitor the engine starters, but I would like to monitor everything else. Unfortunately, the way my boat is set up, each battery bank serves an engine and house loads. So I need an effective way to separate the two functions.

On your proposed V2 diagram is the green box the starter motor. If so, that will only measure current flowing to the house bank. Do you just want to measure the current or do you want it to act as a battery monitor measuring SOC. If you want to measure SOC then your charger needs to connect to the load side of the shunt, not the battery side. Ignoring the Ah used by the starter is probably OK unless you end up doing a lot of cranking one day.

How to Remove Starter from Shunt Circuit - Will This Wiring Layout Work?

DIY

pwfarnell 17 October 2024 16:38 8

Have a read of this FAQ and the drawings in it that I have copied below.

https://community.victronenergy.com/t/shunt-battery-monitor-not-reading-the-correct-soc-amps-missing-solar-decreasing-daily-or-other-misreading-problems/87

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How to Remove Starter from Shunt Circuit - Will This Wiring Layout Work?

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