question

cbouch avatar image

What Shunt Capacity do I need?

I am a little confused which is not that hard to do.. I am buying a bmv700 battery monitor that comes with a 500 amp shunt. My battery bank has a total of approx 665 amps..do I need the 1000amp shunt??the manual says that the 500 amp shunt is satisfactory in most cases. So do you base the shunt size on battery total capacity or what you expect the total maximum amp draw will be at any one time. I would expect that my max draw would not exceed 400 amps and then only when the 2000 watt inverter and bow thruster operating at the same time and then only got a couple of seconds at a time. Thanks

BMV Battery Monitormonitoring
2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

2 Answers
Murray van Graan avatar image
Murray van Graan answered ·

Hi @Cbouch, the 500A shunt means that that is the amount of current that can flow through it at any time. For a 12V system 500A translates into usage of roughly 6KW, a 24V system 12KW and a 48V system 24KW. Your battery bank rating is 665A/H, that is the total amount of Ah’s it can supply over a period of between 10 and 20 hours.

2 comments
2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

So does this mean that the provided shunt is ok for my situation??

@Cbouch, yes. The only time we've particularly recommended one of the bigger shunts is when the BMV will be monitoring a start battery, under which condition it's easily possible that >500A would be flowing through the shunt. For what you've described, you're absolutely good to go with the shunt you have.

spirou avatar image
spirou answered ·

It would greatly help the confusion to use correct units. In the US it seems acceptable to use amps when talking about current (amps) and capacity (amp hours). Your battery bank is 665 Ah, capable of delivering xy A. The shunt does not care about capacity.

2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.