Shunt and Battery Monitor

[Dirt Rider]

If I can ask a stupid question, I am going to add a second battery in parallel, how do I add a shunt for each battery, and how will it know which battery it is seeing if both are connected?

 

[buckland]

Well what I know wouldn’t fill a shot glass but if you are making one big battery outta two.... why would you need two shunts? They are performing as one battery unit.

 

[Dirt Rider]

So I know the charge on each battery individually

 

[buckland]

Shouldn’t the charge be the same if they are in parallel ?

 

[Dirt Rider]

Thats the problem, cannot get a real sense of each battery, idealy they should be the same, but if not how would I know?

 

[buckland]

All I would do is disconnect occasionally and put an ohm volt meter on each post to test each battery separately. Would only take a second or two. Otherwise if they are the same type battery attached in parallel they should wear the same. Not a good idea to attach two batteries that are different ages.

 

[Vic Harder]

This is a great question. The BMV has an option for "mid point" voltage testing, but that only works for series connections.

As Buckland suggests, the two batteries should be identical in makup/brand/age. To use the shunt as intended, I would suggest using a buss connection for both batteries to ground to, and from there go to the shunt. You will NOT be able to see individual SOC for each though

 

[PaulT]

I’ve wondered when someone would ask this question.

For a short time, it bothered me that this info was unavailable, but the cost of obtaining it is well past the point of diminishing returns, IMHO.

If it is a concern, attach the positive lead from solar & load on one battery, and place the negative lead from the shunt on the other battery, swallow hard & enjoy your camping. Life keeps getting shorter.

Paul