It seems the Overkill BMS eliminates the need for a shunt

[Samsonite801]

I can double the number in my head is close enough for me. Yes they don't discharge perfectly equal either but still close enough. Worst case l have to look at both. Mostly just a curiosity anyway as I have way more power now with no more worries. Never had a shunt before and they seem to have their own periodic issues too.

So I have the 6 Overkill BMSs now in parallel, I can log into any one of them and get an idea of SoC, since they are all usually within a percent of each other. However, one reason I did purchase a Victron BMV-712 shunt was because it has a POE data cable / remote display which I can mount in the living area (in the kitchen), and it has the actual bluetooth radio on that remote display unit, so it gets a nice strong signal from anywhere in the motorhome front to back.

The Overkill BMSs, and their bluetooth radios of course, are in the basement of the coach, and so to even be able to get a good enough signal to connect to them, I pretty much have to go stand (or sometimes even kneel down) right over the floor above them in order to connect.

I do like to log into each one of them periodically to make sure none of them have tripped or anything. I did have one trip before when one cell was out of balance.

But for normal daily use, I'd just like to see the one SoC indication and it's also nice to have the voltage, battery bar, and SoC percentage indicator, battery temperature, etc, on a physical display in the kitchen too (so it doesn't require opening a software app to see it)...

 

[RV10flyer]

I have 132kWh battery bank consisting of 10 BMS's, 10 hall-effect sensors or shunts, 10 various battery monitors. Two are Overkill. One has an accurate internal shunt, one does not. I don't depend on the BMS alone. I consume 2 kWh per battery, per night average. One check in the morning and evening and its easy to see if something is not normal.

 

[chrisski]

Is this assumption I am making correct?

If you have a shunt, recommend keeping it in the system. I have two Batteries so two BMS's and I need to check both BMS by logging on with two different bluetooth devices and add them up or just log into the shunt that measures everything also...

The BMS is simply not accurate for tracking SOC. May be fine on a small battery, but my bank needs better tracking.

I second this right here. My experience is that one of my two BMSs reads 30% under the actual SOC. I know the battery is full because I watch the other data like individual cell voltage and the fact the battery is not taking a charge, so I know its full. I can not find a BMS setting to "synch to 100%" like I can my shunt. I've been hoping after several charge cycles the low BMS will read SOC correctly, but does not. Others have said they've seen this, but tends to disappear after several cycle once the BMS knows the battery. Mine has not disappeared.

 

[740GLE]

Everyone’s build is different simple small systems people may find the BMS perfectly adequate for their needs. Once you start expanding your system a shunt is a great tool.

Someone coming from premade 100ah packs having the info if the JBD BMS in front of you is a huge improvement. The OP may not see the value in adding a shunt now but if he expands the system it might’ve worth it.

 

[Lt.Dan]

Everyone’s build is different simple small systems people may find the BMS perfectly adequate for their needs. Once you start expanding your system a shunt is a great tool.

Someone coming from premade 100ah packs having the info if the JBD BMS in front of you is a huge improvement. The OP may not see the value in adding a shunt now but if he expands the system it might’ve worth it.

I disagree. I've had some BMS's that were highly inaccurate. One of my Daly BMS's was perfect and exactly followed a Victron Shunt. The next one would should 30% when Victron showed 0%, current was never even close with the Daly BMS. Same with the JBD, one exactly the same as a shunt, one wildly different.

DONT assume your BMS is great and you never have to compare it to a proven product that does exactly what you need.

 

[740GLE]

Again comparing a system with no ability to monitor to one that has some data, yeah it’s a pretty sweet feature.

I’d much rather have some data that I know maybe inaccurate vs no data.

 

[Henderson]

There is also an optional switch setting that can be used with two wires and a remote switch. I am experimenting with that on a roto tiller conversion. It might eliminate needing a contactor.

What type of remote switch/brand/model are you looking at? I'm in the market for one but not don't know alot about these types of devices. Will be researching them though.

 

[carl2591]

Get a real columb meter or shunt and you'll see the difference. I did with my setup. I find the shunt far superior

"shunts" are designed to measure flows like amps, volts etc, whereas the "BMS" is designed to protect.. high voltage, high amps, too cold etc... with both being referred to as "BMS" (battery monitor system or battery management system.. ) might need to refer to them as BMS1 for management and BMS2 for monitor ..

 

[Ampster]

What type of remote switch/brand/model are you looking at?

I will just look in my parts bin or search Amazon.