Connect batteries individually to bus bar for true perfectly balanced charging/discharging

[BigCharlie]

I was planning on wiring my six FLA's as outlined in the article below.

Then it dawned on me, why not connect each battery individually to a bus bar?
Then connect that bus bar to another that is attached to shore power, MPPT, inverter, and a fuse block. A shunt in between the two bus bars.

Is that not the best way to achieve near "perfectly balanced charging?"

And for my setup, it would use less wire and look very clean.


Something like this. Put the wire going to the second bus bar in the middle.


I mentioned this in klachman 's 1bus bar post but thought I should start a new thread.

https://www.impactbattery.com/blog/post/how-to-charge-marine-and-rv-batteries-in-parallel

 

[sunshine_eggo]

Generally speaking bus bar setups are optimal; however, the "halfway" method is also very effective if done correctly, though it is challenging with 6 batteries.

I doubt the proposed bus bar would have a significant advantage and may be worse.

Here's what Victron has to say about paralleling in their "Wiring Unlimited" manual:



Note how the bus bars are MASSIVE. They present substantially lower resistance than the battery terminals themselves and allow for very short interconnects. I would be concerned that the extra wiring you would need to connect to such small bus bars might be more restrictive. the total length of wire for each battery would need to be the same.

 

[AleksK]

You can not Wire 6 batteries and get balanced charging the same way they show in the picture with 4 batteries.

The only way to do six, is to tie a set of two together and run cables from opposite corners of the pair. From there you would end up with 3 equal length blacks and 3 red's which would go to a small bus bar, then each set of small bus bars need an equal length run to a bigger bus bar where they all join the inverter battery cables.

It's complicated but that's how it works, only 2 or 4 batteries can be balanced together in parallel perfectly, from there you go by sets of 2 or 4

 

[BigCharlie]

Generally speaking bus bar setups are optimal; however, the "halfway" method is also very effective if done correctly, though it is challenging with 6 batteries.

I doubt the proposed bus bar would have a significant advantage and may be worse.

Here's what Victron has to say about paralleling in their "Wiring Unlimited" manual:

View attachment 97818

Note how the bus bars are MASSIVE. They present substantially lower resistance than the battery terminals themselves and allow for very short interconnects. I would be concerned that the extra wiring you would need to connect to such small bus bars might be more restrictive. the total length of wire for each battery would need to be the same.

Thanks, man. I like the idea of the post. It seems to me that would be a good compromise between diagonally and busbars.

Do you have a suggestion for a post that can handle the amperage, if that seems like a good answer?

 

[Swan59]

Question; marine solar install: 900 w from 3 solar panels with a Victron smart charger controller. I need 200 Ah to run the vessel 24 hrs. 24 v boat. Series connection on the panels gives me lots of V but low amps. (135 V /8.5 A continuous in ideal sun). Parallel connection on the panels gives me high amps (45 V /24 A). I am confused on this one point as everyone says hook the solar panels up in series. I know about sun hrs /day cable needs etc. but can't reconcile this one point.
Does the Victron see watts and with battery feedback make magic adjustments to feed the batteries high amps if in series?
David

 

[time2roll]

The negative bus pair with a shunt/monitor between will serve you well.

There was a thread a while ago with a good mathematician / engineer that had an expandable formula to connect any set balanced. Not sure how to find it. I would go with the bus and equal length connectors.

 

[Swan59]

I have 2 banks each with 4 x 6v batteries to give me 24 v in total. series connection on the 4 each, then paralleled out to the 24 v system on my boat. Victron 150/70 charger. Would the bus bar idea be much better than normal hook up on the terminals. Also with busbar diagram above I would need 4 busbars and then connect the output of each bar before entering the controller. Correct? Is this a simple connection of the 2 + and 2 - before Victron?

 

[Zwy]

Question; marine solar install: 900 w from 3 solar panels with a Victron smart charger controller. I need 200 Ah to run the vessel 24 hrs. 24 v boat. Series connection on the panels gives me lots of V but low amps. (135 V /8.5 A continuous in ideal sun). Parallel connection on the panels gives me high amps (45 V /24 A). I am confused on this one point as everyone says hook the solar panels up in series. I know about sun hrs /day cable needs etc. but can't reconcile this one point.

It seems you are discussing 2 totally different topics. For the panels, the SCC would have to be rated for the 24A, most SCC's will accept around 20A and clip the rest so it is wasted energy the panels produced. Efficiency is higher with higher PV voltage, you don't see a high voltage drop and less power loss. With 3 panels, best option is 3 panels in series, but you have to have a SCC that can handle the higher voltage.

Does the Victron see watts and with battery feedback make magic adjustments to feed the batteries high amps if in series?
David

Preferred battery arrangement is to purchase a 24V battery than put two 12V in series.

 

[Texas-Mark]

You can not Wire 6 batteries and get balanced charging the same way they show in the picture with 4 batteries.

IMO too many people over-think this. If cables are properly sized to begin with, there will be negligible "unbalancing" regardless of how they are connected.

 

[Swan59]

It seems you are discussing 2 totally different topics. For the panels, the SCC would have to be rated for the 24A, most SCC's will accept around 20A and clip the rest so it is wasted energy the panels produced. Efficiency is higher with higher PV voltage, you don't see a high voltage drop and less power loss. With 3 panels, best option is 3 panels in series, but you have to have a SCC that can handle the higher voltage.


Preferred battery arrangement is to purchase a 24V battery than put two 12V in series.

there are 3 panels the SCC for each is 9.17 so ok on the panels. In series it would be 8.5 In parallel additive to 25.5 .
I have a marine solar install: 900 w from 3 solar panels with a Victron smart charger controller. I need 160-200 Ah to run the vessel 24 hrs. 24 v boat. Series connection on the panels gives me lots of V but low amps. (135 V /8.5 A continuous in ideal sun). Parallel connection on the panels gives me high amps (45 V /24 A).

I am confused on this one point as everyone says hook the solar panels up in series for more V but the controller would limit the V to the batteries to say, 30 V max. Right? So why the excess in V? In parallel, I would get around 40-45 V and 24 A.



So, how do I get the amps needed?



I know about sun hrs /day cable needs, etc. but can't reconcile this one point.


Does the Victron see only Watts and with battery feedback, make magic adjustments to feed the batteries high amps if in series?

 

[Zwy]

there are 3 panels the SCC for each is 9.17 so ok on the panels. In series it would be 8.5 In parallel additive to 25.5 .
I have a marine solar install: 900 w from 3 solar panels with a Victron smart charger controller. I need 160-200 Ah to run the vessel 24 hrs. 24 v boat.

24V system times 200Ah is 4800Wh per day plus overhead of an inverter and efficiency losses

With 900W of solar, you need a yield over 6 hours long of high yield just to cover daily needs charging a LFP battery. The best money spent is on efficiency and energy conservation, I'd seriously look at what you can do to implement reduced load and energy consumption. Peak output is at high midday sun, on each side of midday sun, the yield is less.

Series connection on the panels gives me lots of V but low amps. (135 V /8.5 A continuous in ideal sun). Parallel connection on the panels gives me high amps (45 V /24 A).

Must be some difference in you calculations because the watts don't agree in both scenarios. The 135V/8.5A comes to 1,147.5W and 45V/24A= 1080W

Doesn't matter though. Unless you have shading problems, which is highly unlikely on a boat, the panels in series will always yield more watts due to the higher voltage (less voltage drop) and less power loss. Power loss is current squared times resistance.

I am confused on this one point as everyone says hook the solar panels up in series for more V but the controller would limit the V to the batteries to say, 30 V max. Right? So why the excess in V? In parallel, I would get around 40-45 V and 24 A.

So, how do I get the amps needed?

Don't worry about amps, you use watts.

I know about sun hrs /day cable needs, etc. but can't reconcile this one point.


Does the Victron see only Watts and with battery feedback, make magic adjustments to feed the batteries high amps if in series?

The SCC will just convert high voltage PV current to the system voltage.

Take the 135V/8.5A peak output and a 24V system. The SCC will reduce the voltage to what is needed to charge the battery. In your case, it appears to be lead acid (more on this later) which would be around 29.2V max. The 1148 watts produced at peak output would be converted to 29.2V at 39.30A.

Here is the next problem with your system and that is the lead acid batteries. Lead acid chemistry requires an absorption charge to reach full charge. You need to keep lead acid chemistry close to a full charge on a daily basis if possible to prevent sulfation and reduced capacity. The problem with absorption is it takes time because the internal resistance of the battery will be higher as it nears full charge and the amperage will be reduced. You did not state what Ah size the 6V batteries are but I'll assume 200Ah and you have 2 banks(4 x 6V each), which you want to parallel together. That gives a total size of 400Ah with 2 banks in parallel. With lead acid, you have 50% useable capacity, so with 200Ah used per day, you would be OK with that size of bank in parallel. But it will take way more than the 6 hours I mentioned above due to the absorption charge. I doubt you will be able to reach full charge in a day. It won't matter if you add more panels, once you hit absorption, the battery will only accept X number of watts.

Again, I can't stress it enough, look seriously at load reduction and energy conservation. More efficient appliances, changing lighting to led and adding timers, more efficient food storage (refrigerator and/or freezer). You would also benefit from a switch to LFP batteries, LFP gives increased useable capacity and no absorption charge plus you can partially charge and not worry about sulfation.

 

[629658]

Victron Power In’s are the only way to go IMO. 1000 amp rating, protected covers, neat and tidy. I couldn’t DIY 2 quality buss bars with time and materials any cheaper.