Battery monitoring mystery

[amazinghank]

Well that’s good to know, I tried to get instructions from battery company, but it was a little vague. Glad for the forum and thanks for the help

 

[amazinghank]

What is the best way to wire these 4-batteries? What is your feeling on these battery balancer/optimizer I see advertised? See photo, if you look hard I added notes for Shunt & Fuse.

 

[MisterSandals]

What is the best way to wire these 4-batteries?

The "best":


See this thread. Post #3 and #4 are exactly what you are asking.

Calculation of parallel string battery currents

Hi, everybody! I'm a retired EE. I didn't want my EE skills to fade away after retirment, so I exercise them when I can. Whenever I see a non-trivial circuit analysis problem on one of various forums I frequent, I challenge myself to solve it. Recently I watched Will's video about current...

diysolarforum.com

What is your feeling on these battery balancer/optimizer I see advertised? See photo, if you look hard I added notes for Shunt & Fuse

If you implement the above pic or your pic in post #19 in this thread, you should not need a balancer. I don't have experience with them (i concentrate on getting the wiring right).

The shunt looks good. The fuse is probably ok too fusing on the negative side. I prefer fusing positive.
If you have your negative grounded (to vehicle frame for example), then i think you should put the fuse on positive.

 

[amazinghank]

Ok, I like it. I’ll wire the fuse into the positive and look on how to fabricate or buy a long copper busebar

 

[MisterSandals]

and look on how to fabricate or buy a long copper busebar

The wire lengths and type from bus bar to batteries should be identical. Thats the only trick.

 

[amazinghank]

Ok, I like it. I’ll wire the fuse into the positive and look on how to fabricate or buy a long copper busebar

I wonder how I determine how wide/think of a busbar for 4-105ah batteries. I guess I need to figure for what 50 amp’s?

 

[MisterSandals]

I wonder how I determine how wide/think of a busbar for 4-105ah batteries. I guess I need to figure for what 50 amp’s?

How big is your fuse? What is your largest anticipated load?

 

[MisterSandals]

This is from another discussion but it may give you an idea how to wire the bus bar. Note the positive and negative wires are connected to opposite bus bar ends "diagonal" across the batteries, not from the same end (the top).

 

[amazinghank]

When I looked at your “best” diagram and saw that the connections are in the middle between 4&5 of the positive and the middle of 1&2 of the negative, I tried to in vision how to actually make that connection, I read later in your post a post from SolarRodthat showed connecting the batteries with a busbar and drilling a hole in those locations to make the connection

How big is your fuse? What is your largest anticipated load?

i have a 30amp trailer, and a 40amp inverter , so just guessing 50amp for the busbar, but as you can see, I’m not the sharpest tool in the shed. Only reason I thought busbar was not knowing how to “T” into existing wire.
.

 

[MisterSandals]

i have a 30amp trailer, and a 40amp inverter , so just guessing 50amp for the busbar,

No you are mixing voltages.
30A trailer at 120V AC = 3600W
This equated to 12.8V DC as: 3600W / 12.8V = 281A

What is the size of the fuse that you put on your battery? That is the minimal size that your bus bars should handle.

Only reason I thought busbar was not knowing how to “T” into existing wire.

Yes, that is the problem with that design! The bus bar makes things easier to get right.

 

[amazinghank]

You’re right, I believe that a 100amp fuse came with the inverter. I will check, thanks for setting me in the right direction.

 

[MisterSandals]

Maybe helpful:

Custom Bus Bars From Copper Flat Bar

The first iteration of my system used all 2/0 cabling between the big components such as between the battery and the shunt and fuse. I'm in the process of rearranging my system to make way for an inverter/charger upgrade. In doing so, I decided to ditch the 2/0 cable where I could and use...

diysolarforum.com

 

[amazinghank]

Maybe helpful:

Custom Bus Bars From Copper Flat Bar

The first iteration of my system used all 2/0 cabling between the big components such as between the battery and the shunt and fuse. I'm in the process of rearranging my system to make way for an inverter/charger upgrade. In doing so, I decided to ditch the 2/0 cable where I could and use...

diysolarforum.com

Well I finally solved the false reading on the 4-lithium battery bank. Once I was able to get to the battery bank, I reset the 4 individual BMS buttons and that corrected the issue. I assume that at some point one of the batteries was discharged too much.

I’m now going to re balance the batteries and use a 24” x 1/4” copper bus bar to connect the four batteries and then connect as your image showed.

I really appreciate you support and educating me on battery balancing.

Thanks hw

 

[amazinghank]

Well I finally solved the false reading on the 4-lithium battery bank. Once I was able to get to the battery bank, I reset the 4 individual BMS buttons and that corrected the issue. I assume that at some point one of the batteries was discharged too much.

I’m now going to re balance the batteries and use a 24” x 1/4” copper bus bar to connect the four batteries and then connect as your image showed.

I really appreciate you support and educating me on battery balancing.

Thanks hw

Do you have any suggestions on what type of metal bolt to use to make the connection to the bus bar? I need a 3/8” x 1” bolt & nut. Was thinking I might need brass, bronze or aluminum, but I may be overthinking this?

 

[MisterSandals]

Do you have any suggestions on what type of metal bolt to use to make the connection to the bus bar? I need a 3/8” x 1” bolt & nut. Was thinking I might need brass, bronze or aluminum, but I may be overthinking this?

Nearly all the connection and current is from the surface contact, not the bolt. Get those surfaces clean, scoured and snug. Some anti oxidization goop like Nolox helps too.