Multiple MPPT's and Connection to Battery Bank

Oski

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Jan 10, 2020
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Good Morning ... first let me say ... I have looked around the web for an answer to this question. It seems like it will be easy for those that know there way around electrons! Here it is ....

I am in the process of doubling the wattage and battery capacity of my solar charging setup of my overland truck. To that end I am adding a second 100/50 victron smart solar unit to handle the additional four 200w panels (wired per Will in 2x2 series and parallel for 24v). This will work to charge a four battle born 100ah 24v battery bank. Obviously I want to find a setup that is the most efficient /safe/long lasting way to charge the batteries.

My question is ...what is the best way to connect the second controller to the battery bank?

A) Connect positive lead from MPPT #2 to an appropriate sized bus bar to combine it with MPPT #1 .... big cable to the positive battery terminal #1 (first two parallel wired batteries)
Result - Both MPPT's connected to one point in battery bank

B) Wire the MPPT#2 positive lead to the positive battery terminal #2 (second two parallel wired batteries) on battery bank
Result - Two individual MPPT's connect to different points/sides of the series wired battery bank

C) It doesn't really matter .... either way will work the same

I have had issues in the past with lithium batteries having issues with balanced charging. That knowledge prompts this question. Given the cost of the batteries, I want to be sure to set it up properly.

Thanks in advance!

truck xs.jpg
20220120_174017_resized.jpg
 
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MisterSandals

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our battle born 100ah 24v battery bank.
I have had issues in the past with lithium batteries having issues with balanced charging.
How do you have these wired? Maybe that's a problem.

B) Wire the MPPT#2 positive lead to the positive battery terminal
There are 4 positive battery terminals. Do you mean battery bank terminal? This whole paragraph is REALLY confusing.

In general, its fine to have multiple charges charging a battery bank. You probably already have 2 chargers, your SCC and alternator so having a 3rd is not that uncommon. If you have shore charging capability that'd be a 4th. The trick with MPPT's is that they must be configured identically or they will slam dance as they both hunt for optimal charging.

I would consider looking at your existing array and seeing how that works with your new panels. Are they all the same? You imply that they are 12V panels but that is a marketing term. If you look at the specs on the back, you will see the Voc and Vmp are significantly different. You may have an opportunity to optimize your array(s).
 

Oski

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Jan 10, 2020
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Sorry for the confusion ... I was trying to be brief.

My current system is based on two 12v 100ah BattleBorn batteries wired in series to get my 24v system. My plan is to double that by adding two more batteries. These will be wired in series to double my AH's and maintain the 24v system. So here are the two options in graphic form ...
Diagram001_OptionA.jpg


OR
Diagram001_OptionB.jpg

PS: All of the panels are the same model ... just different production runs.
 

MisterSandals

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Both of those options are completely unbalanced and will result in very unbalanced batteries.

This is the simplest for me to visualize:
Screen Shot 2022-01-21 at 12.51.28 PM.png
 
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Bluedog225

Texas
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Nov 18, 2019
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I like battle born. I have two recently acquired. I was going to get two more to have a 48v system.

But in a blinding flash of the obvious, I realized I could have a 48v 100ah rack battery for the price of two more battle borns.

I’m going that direction since it is the same $ out of pocket, and will use the two incumbent battle borns for 12 volt auxiliary systems.
 

OffGridGuy

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Western Washington
Howdy, looks like a nice project.

The Victron line of MPPT charge controllers has a $39 dollar device, called the Victron Smart Battery Sense.

You connect it to battery and via Bluetooth it will network both of your charge controllers.

So then both of your charge controllers will be in sync and charge your batteries, as if it was one large SSC....

It's a great well thought out solution that works great.....

Enjoy....
 

HRTKD

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Option A or B? None of the above. Wire each 24v "battery" to a common bus bars using equal length cables. Positive cables the same length. Negative cables the same length. That gives each "battery" equal access to the charge.

Wire each Victron MPPT to the common bus bars.

Adding to what OffGridGuy wrote, if you have the Victron BMV-712 or the Smart Shunt, it can network the two MPPT devices. I have the BMV-712 and have my two MPPT networked.
 

Oski

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Jan 10, 2020
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Option A or B? None of the above. Wire each 24v "battery" to a common bus bars using equal length cables. Positive cables the same length. Negative cables the same length. That gives each "battery" equal access to the charge.

Wire each Victron MPPT to the common bus bars.

Adding to what OffGridGuy wrote, if you have the Victron BMV-712 or the Smart Shunt, it can network the two MPPT devices. I have the BMV-712 and have my two MPPT networked.
Thank you so much ... this is exactly what I was HOPING to learn!
 

Oski

New Member
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Jan 10, 2020
Messages
21
Howdy, looks like a nice project.

The Victron line of MPPT charge controllers has a $39 dollar device, called the Victron Smart Battery Sense.

You connect it to battery and via Bluetooth it will network both of your charge controllers.

So then both of your charge controllers will be in sync and charge your batteries, as if it was one large SSC....

It's a great well thought out solution that works great.....

Enjoy....
Thank you "OffGridGuy". This looks perfect for what I need. A big reason I like Victron is the bluetooth capability. PS: greetings from the frozen tundra of Eastern WA!
 

sunshine_eggo

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I need to chime in.

Option B is actually catastrophically bad. You NEVER charge individual components in a string unless you're deliberately drying to destroy them OR you're deliberately trying to restore balance by individually charging the lower voltage components.

Option C:

1642808098471.png
 
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