Multiple battery

[ArthurEld]

I think this is the one smoothJoey recommends - https://www.amazon.com/AiLi-Battery...s=battery+monitor+shunt&qid=1600632621&sr=8-5

Or this one is probably better if I only use one- https://www.amazon.com/AiLi-Voltmet...s=battery+monitor+shunt&qid=1600632722&sr=8-4

 

[ArthurEld]

What is the purpose of the shunt in your setup HRTKD?

 

[John Frum]

I updated my picture and I tried to look up the size cable I will need.
I think 2/0 AWG from the inverter to the power switch, fuseblock to power switch and inverter to negative busbar. And 3 AWG for the rest.
I think that is thicker than the minimum recommended. My cables will be less than 6 feet.
The battery monitor shunts were either 100A or 350A. I don't know if 350A would be better.

Actually if those BMSs are smart you might be able to use them to track the current from individual batteries.
3 awg is not the most common size.
4 awg should be fine for the battery connections.
for the main wire 2/0 is a too small 330 amps * .75 fuse headroom = 247.5 load amps
3/0 has no breathing room at all.
suggest 4/0 awg for the main wires.

 

[John Frum]

I think this is the one smoothJoey recommends - https://www.amazon.com/AiLi-Battery...s=battery+monitor+shunt&qid=1600632621&sr=8-5

Or this one is probably better if I only use one- https://www.amazon.com/AiLi-Voltmet...s=battery+monitor+shunt&qid=1600632722&sr=8-4

I recommend the 350 amp version of the aili.

 

[ArthurEld]

Thanks again guys. I feel much better about this now.

 

[HRTKD]

What is the purpose of the shunt in your setup HRTKD?

It provides an overall state of charge. It tracks charge/discharge, though not as well as a two shunt configuration which separately tracks charge and discharge.

 

[ArthurEld]

So far, I'm liking my Victron BMV-712 for battery monitoring. I would not want to have four of them. There is a new-ish product from Victron that is just the shunt and it has some smarts in it. Enough that you could go with that and skip the wall readout that is used by the BMV-712.

However, having to aggregate the data from four shunts would not be what I consider an elegant solution. If possible, I would stick with one shunt, even though I understand the suggestion for monitoring each battery. If one of Victron's other monitoring solutions can do the aggregation, then that would be a good way to go.

Sorry for the stupid question. When I looked up your BMV-712 it doesn't show the shunt so I wasn't sure how it worked. I looked further and see how it works now.

 

[ArthurEld]

Can I put the fuses and busbar close to my Inverter/Controller so I will be able to use short 4/0 AWG cables?

 

[HRTKD]

Can I put the fuses and busbar close to my Inverter/Controller so I will be able to use short 4/0 AWG cables?

That's a good question. I would calculate the cost of the length of the four runs of 4 awg wire versus the 4/0 awg wire. Normally, you want the fuse as close to the batteries as possible.

 

[John Frum]

The further the fuse is from the power source the greater the chance for a short upstream of the fuse.
That is why these https://www.waytekwire.com/item/45576/Littelfuse-0FHZ0201Z-SMZ-Series-M8-Stud-Mount/ and these https://www.waytekwire.com/item/45575/EATON-s-Bussmann-Series-MRBF-Mounting-Bar-/ exist.

 

[ArthurEld]

Thanks guys. My batteries will be less than 6 feet from my charge controller.
So, I think my 4/0 AWG cables will be 1 to 3 feet long depending where I decide to mount the on/off switch and busbars.
Do the smaller 4 AWG cables need to all be the same length? They will be about 2 - 5 feet from the busbars.
I will put terminal fuses on the batteries.
I think it will be ok if I use 500A busbars with 3 terminals connected as shown. Or I could get the 5 terminal one if that is better.

 

[John Frum]

Do the smaller 4 AWG cables need to all be the same length?

Yes, it is very important to match the wire length in order to match the resistance of each current path.
You want to ensure and verify that the batteries pull together is equally as possible.
What BMS have you chosen?

 

[John Frum]

The 3 terminal should be fine but you will have to stack lugs which could complicate maintenance a bit.

 

[HRTKD]

The 3 terminal should be fine but you will have to stack lugs which could complicate maintenance a bit.

This * 100! Stacking lugs adds to the complexity of making cables and connecting them. A 5 post bus bar would work better. Bus bars with covers don't like it when the cables/lugs come in at angles - at least mine didn't. A 90° approach is ideal, but you can fudge that to maybe 60° at most.

What gauge wire are you planning to use with the solar charge controller? My Victron 100/50 was explicit that 6 AWG was the largest to use. That was a bit squishy as you could go slightly larger. I used ferrules on my 6 AWG wire and it fit into the solar charge controller ports OK.

 

[ArthurEld]

What BMS have you chosen?

I have been thinking about using the 200A JK (Heltec) with 2A active balance.
I haven't ordered any yet but 4 of those for $800 seems pretty good.

 

[ArthurEld]

This * 100! Stacking lugs adds to the complexity of making cables and connecting them. A 5 post bus bar would work better. Bus bars with covers don't like it when the cables/lugs come in at angles - at least mine didn't. A 90° approach is ideal, but you can fudge that to maybe 60° at most.

What gauge wire are you planning to use with the solar charge controller? My Victron 100/50 was explicit that 6 AWG was the largest to use. That was a bit squishy as you could go slightly larger. I used ferrules on my 6 AWG wire and it fit into the solar charge controller ports OK.

I will use the 5 post busbar.
My charge controller has ring terminal connectors and Sol-Ark recommends 4/0 AWG battery cables.

 

[HRTKD]

I will use the 5 post busbar.
My charge controller has ring terminal connectors and Sol-Ark recommends 4/0 AWG battery cables.

Ah, OK. No need to worry about the wire gauge then. All you need to do is get 4/0 lugs that match the post type. Don't forget to buy heat shrink tubing that is big enough to fit the wire.

 

[ArthurEld]

Ah, OK. No need to worry about the wire gauge then. All you need to do is get 4/0 lugs that match the post type. Don't forget to buy heat shrink tubing that is big enough to fit the wire.

Now that you mention it, it will be awkward to connect to the busbars. The cable is .75 thick.

 

[HRTKD]

Now that you mention it, it will be awkward to connect to the busbars. The cable is .75 thick.

There are ways to do it. If you have to put two cables on the same stud, make sure you crimp them 180° different. They fit on the bus bar better that way and you don't have to angle the two cables differently. But this depends on your bus bar.

 

[ArthurEld]

I thought I might buy the cables with connectors on them. Another thing to figure out.
Thanks