Victron Smart Shunt Midpoint Monitoring

manyman297

I’m getting ready to install two LiTime 100ah batteries and just found out about midpoint monitoring. Apparently it’s a better way to monitor the health of two or more batteries in series or parallel. Does anybody have any insight into this at all? I currently don’t have my smart shunt wired like this but I’m unsure of if it’s worth the extra work.

elbolillo

I’ve only read a bit on the usage of mid point monitoring. Doesn’t seem like something that is very useful for small battery banks.

manyman297

I read similar but anything that would help give better insight into the health of each battery would be great.

YanniLazarus

It made me feel good to see the midpoint difference for my 2 6V AGMs is .2% - with my new Victron smart shunt. 

The more I know about my battery health the less likely I am to panic buy something new!

Grumpy_G

Midpoint monitoring is only practical for batteries that are connected in *series*. In case of an RV that means 2 x 6V golf cart batteries in series, not parallel 12V batteries.

manyman297

Yeah, I was confused about this but after looking at the wiring diagrams it may only work (or is just more common) in series wiring.

Grumpy_G

It only works for series configuration. Take the simple case of two 6V batteries in series. Midpoint monitoring compares how much charge the individual batteries take and alerts if there is a significant difference. If a cell in either battery fails in this configuration it takes down the whole battery bank. With parallel 12V batteries a failing cell reduces the capacity but does not leave the battery bank completely non-functional. I suppose one could run a smart shunt per battery to detect problems with an individual battery.

As a side note, many LiFePo batteries have battery management systems that can be monitored via bluetooth. That would be the easiest way of monitoring individual battery and even cell health.

manyman297

@Grumpy_G Thanks for the info! It sounds like I should’ve done midpoint wiring when I installed my smart shunt initially…I just didn’t know about it.

The new LiTime batteries showed up. Impressed with how they were packaged. Build quality feels good. I hope they last.

I’m planning on installing them using bus bars. Does anybody know how to size a bus bar to these batteries? The common bus bar sizes I’m seeing are 300A.

Grumpy_G

The batteries put out 100A continuous/280A for 5 seconds. A 300A bus bar is fine.

manyman297

Thanks @Grumpy_G