Positive terminal getting a little crowded. Time for a Bus Bar?

[DaPhatty]

I've been building a house power system based on Will's 400W Solar Power w/ Alternator blueprint and, as the title states, I think I may need to expand beyond Will's original design. Our implementation leverages two SOK 100Ah batteries connected in parallel. At present, the main positive battery terminal has three distinct ring connectors - One for the positive parallel cable, one for the primary battery positive cable, and one for the Renogy Battery monitor. The photo below should give you a good indication of what that currently looks like.

(Please disregard the dangling black cable in the background. It's for a temperature sensor that has yet to be mounted in its permanent location.)



In addition to the above, we also intend to install a Victron IP22 AC to DC charger to be leveraged for occasional shore power charging. My original thought was to connect the IP22 directly to the main Positive and Negative Battery Terminals and call it a day. But now I'm not so sure. The positive stud seems to have plenty of thread left so my original setup should work, in theory. But I am open to suggestions, particularly if there is a a better and/or safer way of doing things.

Or maybe I'm just over thinking this.... Thanks in advance for your feedback.

 

[FilterGuy]

I generally do not like 3 ring terminals on one post but 3 is allowable. However, the way you have it set up is asking for trouble. The highest current cable should be on the bottom and the lowest current wire should be on top.

Basics for putting lugs on posts

I saw some folks on the forum that were assembling lugs onto their cells incorrectly so I thought it might be useful to document how to do it. Click on the orange 'download' button in the upper right corner to get the document. As with all...

diysolarforum.com

 

[mikefitz]

Dont forget the fuses/breakers to protect each cable, ideally close to the positive battery terminals or buss bar. A fault on the light gauge red wire could be interesting, ( like smoke, melting metal, fire).
A layout for illustration or demonstration will often omit or incorrectly place fuses/breakers.

Mike

 

[mikethebike1958]

just a side note Will did say on one video that batteries do not like being linked in paralell series is way more efficient or did i get that wrong?

 

[mikefitz]

Parallel connected batteries double the capacity in Ah and maximum current but have the same output voltage.
Series batteries double the voltage but have the same capacity in Ah and maximum current capability.
With Lithium batteries the BMS may limit the connection in series but usually parallel connection is allowed.
Before connecting in parallel or series the batteries should be fully charged.

that batteries do not like being linked in parallel series is way more efficient

Without knowing the context of this statement its difficult to comment.

In general the higher the voltage that a system runs at the higher the efficiency. With a hobby system a 12v system is usable up to 2000 watts of load, over that consider a 24v or higher system.

Mike

 

[dixonge]

I've been building a house power system based on Will's 400W Solar Power w/ Alternator blueprint and, as the title states, I think I may need to expand beyond Will's original design. Our implementation leverages two SOK 100Ah batteries connected in parallel. At present, the main positive battery terminal has three distinct ring connectors - One for the positive parallel cable, one for the primary battery positive cable, and one for the Renogy Battery monitor. The photo below should give you a good indication of what that currently looks like.

(Please disregard the dangling black cable in the background. It's for a temperature sensor that has yet to be mounted in its permanent location.)

View attachment 68513

In addition to the above, we also intend to install a Victron IP22 AC to DC charger to be leveraged for occasional shore power charging. My original thought was to connect the IP22 directly to the main Positive and Negative Battery Terminals and call it a day. But now I'm not so sure. The positive stud seems to have plenty of thread left so my original setup should work, in theory. But I am open to suggestions, particularly if there is a a better and/or safer way of doing things.

Or maybe I'm just over thinking this.... Thanks in advance for your feedback.

May I introduce you to my positive terminal?


@FilterGuy don't look! LOL FYI, just read your Resource on lug stacking. Pretty sure I did it wrong. Also, busbars arriving from Amazon in two days...

 

[Zil]

well, dixonge. that is not the worse i have seen. i would redo the crimps.

 

[dixonge]

well, dixonge. that is not the worse i have seen. i would redo the crimps.

Starting that project in a few hours, plus heatshrink

 

[eXodus]

In general the higher the voltage that a system runs at the higher the efficiency. With a hobby system a 12v system is usable up to 2000 watts of load, over that consider a 24v or higher system.

Mike

I don't like going over 100-125A Wires are getting unpractical and everything's is getting expensive above that threshold. Further above that you actually loosing efficiency in electric losses.

That mean in my opinion
Max 1500W for 12V
Max 3000W for 24V

and usually there is no need for a 120v devices to draw more then 3000W in a vehicle setup.

 

[Zil]

I have had no trouble with my 12VDC system. 2000W sine wave inverter. 1000W microwave. 400W solar w/ 45 amp TriStar PWM. 12V fridge, water pump, fans, furnace blower, and lights. Originally 690AH CG2 battery bank. Now converting to a 200AH LiFePo experiment. The largest cable is 2/0 marine grade with professional crimps by GenuineDealz. Battery to inverter 2/0 total one way is 24 inches to BusBar, then, plus 18 inches to inverter. I have a measured less than 2% voltage drop, battery to inverter while the microwave is operating on high.

 

[eXodus]

I have had no trouble with my 12VDC system. 2000W sine wave inverter. 1000W microwave. 400W solar w/ 45 amp TriStar PWM. 12V fridge, water pump, fans, furnace blower, and lights. Originally 690AH CG2 battery bank. Now converting to a 200AH LiFePo experiment. The largest cable is 2/0 marine grade with professional crimps by GenuineDealz. Battery to inverter 2/0 total one way is 24 inches to BusBar, then, plus 18 inches to inverter. I have a measured less than 2% voltage drop, battery to inverter while the microwave is operating on high.

so even when you got 2000W inverter -you are not using more then 100A to feed the 1000W microwave.
My point is - that for the money you spend on a 12V 2000W inverter - you can buy a 24V 3000W and the 24V is smaller.

I know converting an existing system from 12V to 24v is expensive.

But going back to the initial topic:

It really depends how much amps you are pulling through those terminals. I wouldn't mind sub 100A with 3 cables attached.
But I sure would only have a single terminal there when I'm pulling 200A

 

[Ampster]

Will did say on one video that batteries do not like being linked in paralell

I agree with @mikefitz that context is important. It is also important to distinguish between the term batteries and cells. I drive two EVs that have as many as 70 cells in parallel and that manufacturer has determined that their approach is optimal.

 

[DaPhatty]

May I introduce you to my positive terminal?

View attachment 68531
@FilterGuy don't look! LOL FYI, just read your Resource on lug stacking. Pretty sure I did it wrong. Also, busbars arriving from Amazon in two days...

Ha! Cut from a similar cloth we are.

It really depends how much amps you are pulling through those terminals. I wouldn't mind sub 100A with 3 cables attached.
But I sure would only have a single terminal there when I'm pulling 200A

In our case, the SOKs are rated at 100A maximum output. We also don't have an inverter, although I suspect eventually we may add one down the line. Not sure if that changes whether or not we should add a positive bus bar.

I generally do not like 3 ring terminals on one post but 3 is allowable. However, the way you have it set up is asking for trouble. The highest current cable should be on the bottom and the lowest current wire should be on top.

Basics for putting lugs on posts

I saw some folks on the forum that were assembling lugs onto their cells incorrectly so I thought it might be useful to document how to do it. Click on the orange 'download' button in the upper right corner to get the document. As with all...

diysolarforum.com

I didn't realize the importance of stacking the positive ring terminals top to bottom from least to greatest current. I'll implement that right away. Considering this, is it safe to say that the wiring gauge should also be stacked from smallest to largest? It's hard to tell in my photo but there are three different gauge wires connected at that terminal - 2 AWG (+ parallel), 4 AWG (in/out from batteries), and (IIRC) 16 AWG (to the battery monitor).

 

[FilterGuy]

I didn't realize the importance of stacking the positive ring terminals top to bottom from least to greatest current. I'll implement that right away. Considering this, is it safe to say that the wiring gauge should also be stacked from smallest to largest? It's hard to tell in my photo but there are three different gauge wires connected at that terminal - 2 AWG (+ parallel), 4 AWG (in/out from batteries), and (IIRC) 16 AWG (to the battery monitor).

Typically, the larger wires are also the higher current wires.... but I guess it could be different. I would always stack by the current.

 

[FilterGuy]

I didn't realize the importance of stacking the positive ring terminals top to bottom from least to greatest current.

The reason for this is to ensure the larger current paths see the least resistance. If the high current lug is on the top, the current has to go through the other lugs first and each connection adds resistance.

In addition, the ring terminals for the smaller wires are often smaller... if this small ring lug is between two large ring lugs, it limits the contact area, creating a higher resistance point.

 

[DJSmiley]

I'd prefer adding a fuse block.

I love the mega/midi fuse blocks.

Just make 1 thick cable (capable of handling the max current), M6 (battery side) to M8 (fuse blok side).
Mega fuse for any inverter, other fuses upon need, so you can fuse for the proper wire gauge.

Also it's better for safety reasons: If your BMS can provide 150A, and you're using 8AWG for example for a charger, the short current will overload the 8AWG.. with this setup you can fuse the 8AWG to for example 30A, without any risk over overloading the wire.

Also from a relaibility point of view I don't prefer stacking. First, unless using studs, you're limiting the amount of usable thread, potentially stripping the terminals out (especially on aluminium posts like prismatic cells) and with all the wires there will be a lot of weight causing stress on the terminals. Especially in a non-stationary environment.

In your case I won't prefer the Victron directly to the cells. Its very likely the Victron's cables aren't able to handle the current of 2 paralled LFP cells.. so if not a dead short, but near dead, it might burn the cable, without tripping the BMS overload.. 200A is A LOT to trip.
It's more likely the cable starts melting/burning if you accidently drive a screw into the wire near the Victron's side for example.

Using a seperate fuse (rated slightly above the Victron's charge current) would prevent it.

 

[dixonge]

I'd prefer adding a fuse block.

I love the mega/midi fuse blocks..

looks nice, don’t find any of them for sale in the US ?

 

[DJSmiley]

Victron has something similar, more stackable.

https://www.victronenergy.nl/upload/documents/Datasheet-Modular-MEGA-fuse-holder-and-high-current-busbar-EN.pdf

You can also stack multiple regular MIDI/ANL fuse holders. Those can be clicked together. If you have some leftover busbar or similar piece of copper you can use it to act as a busbar. I did my install with it: Just drilled holes accordingly to the number of required fuses.

However, the one above is preferred if you have a big inverter, since MEGA fuses are available in higher current ratings than regular MIDI fuses


Littlefuse has also something similar:

Fuse Only Power Distribution Modules (PDM) - Littelfuse

www.littelfuse.com