Just finished install of MultiPlus II, what a great box

corn18

Village Idiot
Joined
Sep 9, 2021
Messages
325
Finally got my MPII 12/3000/120x2 in and got it installed and working. Why didn't I get this in the first place?

Hookup is easy:

AC in from my shore power, AC out to main panel. That's it. No sub panels, no transfer switches. Other than 6/3 Romex being a beast to work with and the Victron AC connectors being a finicky, is was a pretty easy.

DC hookup from bus bars (used 2/0) and the chassis ground.

That's it. It's ready to do great things.

But I really wanted the GX display, too, so I hooked up a Cerbo GX comm box and a GX display. I also hooked up a multi control panel to make it easy to turn on and off. Turns out that was brilliant for another reason (more on that). Also hooked up the Victron smart shunt and Victron smart solar charger controller.

First test was to get it to turn on. The three way switch on the MPII itself has Sanskrit labels and I had no idea what symbol meant what. So I read the manual. Nope, nothing in there. So I went on the internet. Nope, nothing there. So I guessed and flipped it to the double line setting and oila!, it powered up.

Now I get to see the GX display in action.

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This is on batteries with all the AC breakers on. How cool is that display? The 217W is the fridge cooling, 2 TV's in standby, the stick vac charging and the King WiFi thingy. With everything off, the MPII draws 8W, so not too bad. You can also see the solar input.

I turned on the microwave and that worked great. 1300W I believe. Turned off the micro and turned on the rear 15,000 BTU A/C. I have a soft start on it. About 400W for the fan only and then 1,000W once the compressor kicked in. Won't be running the A/C off the batteries, but nice to know I can. The only thing that would not run off the inverter was the fireplace on high. It drew 900W on low and on high I quickly saw 3000W+ before the main breaker tripped. That thing must be a hog. Will have to see what it draws once I get hooked to a 50A service.

Let's hook up the genset. 1800W Champion inverter genset. When I tested it before, I could run the A/C but just the A/C. I could not run the A/C and the fridge, which was a bummer.

Hooked it up with no AC loads. Here's a pic of the display while charging the batteries:

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Nothing revolutionary here. But wait for the best part: Power Share! When I turned on the fridge and the rear a/c, the genset cutoff again. But wait, this fancy thing is supposed to assist the generator (or shore power) with some inverter help. Turns out I needed to adjust the input current limit, which is really easy to do since I have a multi control panel:

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Hard to see but that bottom panel is the multi control for the MPII. It doesn't do much, but it does make it easy to adjust the current limit from shore/gen power. You can do this in the GX display, but it takes a lot of selecting things.

I set the current limit from the genset at 10A (it was at 50A which is why it shut off). Now I turned on the fridge and A/C at the same time and it all worked. The MPII was providing help to the little genset with some watts from the inverter. This is what the display looked like:

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See where it says assisting? The genset is providing 763W and the inverter is providing 468W. How cool is that? The Champion could have provided more, but I had limited it to 10A to keep it quiet. Granted, I am pulling 24A from the batteries, but now I don't have to buy a bigger or another genset to run the A/C and fridge.

That feature alone is the coolest thing ever. It is neat to watch all the Victron stuff work together. It's always adjusting between shore/genset, AC loads, DC loads, charging the batteries and using solar. Victron got this one right, for sure.

Here's the schematic for the whole system:

DC wiring 290RL.jpg

This is where I am going with the 2 batteries:

DC wiring 290RL lynx 1 solar.jpg

And this is where I want to end up:

DC wiring 290RL lynx 3 batts 2 solar.jpg
 

rmaddy

Full-time Solar-powered Trailer Life
Joined
Nov 16, 2019
Messages
1,678
Location
USA
It is nice when it all works together.

If you want an even better GX experience, and eliminate the need for the multi control, see:


I use a modified version of those mods on my Raspberry Pi. I can control my MultiPlus, including charging the current limit, with two taps on the screen. Very handy when needed.
 

CaptainSnowbeard

New Member
Joined
Nov 14, 2021
Messages
2
I would love one of these but they're just far too expensive in Australia. Over the past few months I've watched as the price gradually increased from marginally affordable to "umm no I don't want to sell a kidney". Instead I've had to opt for an inverter with transfer switch and 60amp AC charger.

One day, I hope to be able to go full Victron.
 

corn18

Village Idiot
Joined
Sep 9, 2021
Messages
325
It is expensive here in the US @ $1750. Looks like it's A$2236. Ouch. And you need a GX setup to see the cool displays. And an adaptor to program it. And, and, and...

I am rationalizing the cost by not needing to buy a second genset (or a bigger one). And I can sell my 2 inverters and converter to make up some cost. The math doesn't work, but it makes me happy, so I'll run with it. 🤑
 

HRTKD

Boondocker
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Apr 24, 2020
Messages
6,492
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Somewhere South of Denver
Nice writeup and great results. You're where I would like to be soon. It's too bad that Victron doesn't have bluetooth in the Cerbo GX. All the Smart Victron devices and you still have to connect them with a cable to the Cerbo GX.
 

CaptainSnowbeard

New Member
Joined
Nov 14, 2021
Messages
2
It is expensive here in the US @ $1750. Looks like it's A$2236. Ouch. And you need a GX setup to see the cool displays. And an adaptor to program it. And, and, and...

I am rationalizing the cost by not needing to buy a second genset (or a bigger one). And I can sell my 2 inverters and converter to make up some cost. The math doesn't work, but it makes me happy, so I'll run with it. 🤑
Oh wow. I had no idea it was that expensive in the US as well!

Haha I think your justifications are fair and justified.

I had thought about the GX path but I was thinking of going the VenusOS path that rmaddy had mentioned. But I only have a BMV-712 shunt at the moment so major overkill 🤣
 

blutow

Solar Addict
Joined
Dec 20, 2020
Messages
326
One of the standard main pages on the cerbo/gx display allows quick and easy adjustment of input power and also allows you to turn to inverter on and off. There is really no need for the separate controller unless you like the physical switch and knob.
 

corn18

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Sep 9, 2021
Messages
325
I like the physical switches. But if I hadn’t bought the separate control panel with the multiplus I probably wouldn’t add it.
 

blutow

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Joined
Dec 20, 2020
Messages
326
I like the physical switches. But if I hadn’t bought the separate control panel with the multiplus I probably wouldn’t add it.
Yep, sometimes it's nice to not use a touch screen for everything. One other thing to keep in mind - once you connect the physical controller, you can no longer control the multi through the cerbo/GX screen. It's one or the other. So, that also means you also lose the ability to control the multi remotely (over the air) or from a phone locally. Not that big of a deal depending on your deployment, but it can be a nice feature. Beyond the cool factor, the remote capability is useful at times. I can log into my van and turn on the inverter and that can make the AC kick on (or anything turned on and plugged into 120v like a tank heater, etc.). The cerbo system is really slick and I haven't even started playing with the code red custom stuff.
 

corn18

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Sep 9, 2021
Messages
325
Just as an update, I finished redoing my control center. Got rid of the 250A breaker and went with a T400A fuse and 600A cutoff switch. Works well. Did another test and was pulling 2527W from the inverter. The LED was showing overload, so I didn't let it run for long. At least I know my two SOK batteries can take the inverter to overload and not trip the BMS.

DC wiring 290RL lynx.jpg

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blutow

Solar Addict
Joined
Dec 20, 2020
Messages
326
Just as an update, I finished redoing my control center. Got rid of the 250A breaker and went with a T400A fuse and 600A cutoff switch. Works well. Did another test and was pulling 2527W from the inverter. The LED was showing overload, so I didn't let it run for long. At least I know my two SOK batteries can take the inverter to overload and not trip the BMS.

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I know I've run my multi at about the same watts continuous without it complaining. I also don't remember seeing low voltage like that, so I assume the high amps and low volts is why the multi is barking. I can't remember ever seeing voltage drop below 13v on my system even when running it hard, but maybe it did and I didn't notice. Besides the batteries, the biggest difference between your system and mine is that I'm running 2x 2/0 all the way from batteries to inverter and you are running 1 x 4/0. I wouldn't expect too much of a different based on that. I think the bottle neck is the BMS's. I'm surprised your BMS's didn't shut down if you ran it at this rate for any time. The SOK 206 batteries are only rated for 100a continuous (see below) and you are pushing over 140a through them. Maybe worth reaching out to SOK to see how those parameters are set. The BMS's might not be your issue, but you are getting serious voltage drop somewhere and it seems the BMS is the most likely culprit given the 100a rating vs. what you are pulling.

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corn18

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Sep 9, 2021
Messages
325
I know I've run my multi at about the same watts continuous without it complaining. I also don't remember seeing low voltage like that, so I assume the high amps and low volts is why the multi is barking. I can't remember ever seeing voltage drop below 13v on my system even when running it hard, but maybe it did and I didn't notice. Besides the batteries, the biggest difference between your system and mine is that I'm running 2x 2/0 all the way from batteries to inverter and you are running 1 x 4/0. I wouldn't expect too much of a different based on that. I think the bottle neck is the BMS's. I'm surprised your BMS's didn't shut down if you ran it at this rate for any time. The SOK 206 batteries are only rated for 100a continuous (see below) and you are pushing over 140a through them. Maybe worth reaching out to SOK to see how those parameters are set. The BMS's might not be your issue, but you are getting serious voltage drop somewhere and it seems the BMS is the most likely culprit given the 100a rating vs. what you are pulling.

View attachment 73241
On the SOK Facebook page, they say that if you call SOK, they will tell you the BMS can handle over 130A. There are several tests running at 150A continuous. I gotta say, that is a LOT of amps. I really don't see a reason to pull that many. Fireplace would never be on when on batteries alone. I can see running the microwave and fridge and the furnace (1600W). Or maybe the AC and fridge for a short while (1200W). I just wanted to see what the SOKs could do. Saves me having to add another SOK.
 

blutow

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Dec 20, 2020
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On the SOK Facebook page, they say that if you call SOK, they will tell you the BMS can handle over 130A. There are several tests running at 150A continuous. I gotta say, that is a LOT of amps. I really don't see a reason to pull that many. Fireplace would never be on when on batteries alone. I can see running the microwave and fridge and the furnace (1600W). Or maybe the AC and fridge for a short while (1200W). I just wanted to see what the SOKs could do. Saves me having to add another SOK.
That makes sense. My BMS's are rated at 120a continuous and they heat up in a hurry once you approach 100a. Everything I've read about FET-based BMS's is that running them hot greatly increases the chance of failure. I try to make sure they never go beyond 60a or so continuous and they seem really happy with that and basically no heat build up anywhere on the battery or BMS.
 

curiouscarbon

Science Penguin
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Jun 29, 2020
Messages
1,803
indeed; operating a FET / MOSFET hot from high amps leads to them failure

super wise to evaluate amps that cause minimal heat and call that the real spec 👍👍⭐
 

jharrell

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Aug 11, 2021
Messages
36
I ran the tests on the SOK Facebook page to try and find the SOK BMS cutoff limits as I just installed two 206ah's in my RV. I ran a test with just one 206 pulling over 130 amps continuous for 10 minutes with no shutdown, I then charged back up at 108 amps continuous for about 15 minutes no shutdown. So the BMS current limits are obviously higher than 100 amps, my hope is if SOK thought more than 100 amps continuous was too much they would set the over current limits there similar to Battelborn. The cells in the 206 can handle 1C continuous so they are no problem. I even ran my ac and microwave a the same time for a couple minutes at 300 amps from two batteries without issue.

I based my test on info I found here on this Forum from Cinergi who got a response directly from SOK that the BMS actually can handle up to 150 amps continuous and even that is not an instant shutdown here is the post: https://diysolarforum.com/threads/is-this-12v-battery-better-than-battle-born.10087/post-134056 and relevant quote:

"For the 100ah battery, the recommend current on the spec sheet is 20A.but we mark it on the website, the maximum charge current is 50A, we think 20A is a little bit low for most customers. the BMS we rate: charge Current is 50A, discharge current is 100A, but we design it charge current is 140A~150A, discharge current is 140A~150A
if the charge or discharge current over 150A, the BMS would be cut off in 10 or 15 minutes.But we don't suggest customers do like this, it would short the cycles life of the battery cells."

So it seems the BMS itself can handle 150 amps charge/discharge and the current limits are set there and SOK responded to my post that they may change the published current limits soon upping them to 150 amps for the 206 at least since the cells can handle it. I have found the over temp limits more likely to be hit in my testing. Ran my AC for 3 hours off both batteries which hit about 125F at the terminals, I then started charging back up at 100+ amps and after a few minutes they shutdown for about 10 minutes which they cooled off some then started charging again, they did this twice and once the terminals hit about 108F they continued charging without shutdown for 3 hours. I also hit over temp on discharge in hotter conditions when running the AC for about 2.5 hours and terminals hit 135F. These are extreme tests to see how the batteries work, I will not normally be attempting to run my AC off them, if you wanted this kind of continuous draw/charge you need good cooling specifically on the top of the battery which is where the BMS is.
 

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blutow

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Dec 20, 2020
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326
I ran the tests on the SOK Facebook page to try and find the SOK BMS cutoff limits as I just installed two 206ah's in my RV. I ran a test with just one 206 pulling over 130 amps continuous for 10 minutes with no shutdown, I then charged back up at 108 amps continuous for about 15 minutes no shutdown. So the BMS current limits are obviously higher than 100 amps, my hope is if SOK thought more than 100 amps continuous was too much they would set the over current limits there similar to Battelborn. The cells in the 206 can handle 1C continuous so they are no problem. I even ran my ac and microwave a the same time for a couple minutes at 300 amps from two batteries without issue.

I based my test on info I found here on this Forum from Cinergi who got a response directly from SOK that the BMS actually can handle up to 150 amps continuous and even that is not an instant shutdown here is the post: https://diysolarforum.com/threads/is-this-12v-battery-better-than-battle-born.10087/post-134056 and relevant quote:

"For the 100ah battery, the recommend current on the spec sheet is 20A.but we mark it on the website, the maximum charge current is 50A, we think 20A is a little bit low for most customers. the BMS we rate: charge Current is 50A, discharge current is 100A, but we design it charge current is 140A~150A, discharge current is 140A~150A
if the charge or discharge current over 150A, the BMS would be cut off in 10 or 15 minutes.But we don't suggest customers do like this, it would short the cycles life of the battery cells."

So it seems the BMS itself can handle 150 amps charge/discharge and the current limits are set there and SOK responded to my post that they may change the published current limits soon upping them to 150 amps for the 206 at least since the cells can handle it. I have found the over temp limits more likely to be hit in my testing. Ran my AC for 3 hours off both batteries which hit about 125F at the terminals, I then started charging back up at 100+ amps and after a few minutes they shutdown for about 10 minutes which they cooled off some then started charging again, they did this twice and once the terminals hit about 108F they continued charging without shutdown for 3 hours. I also hit over temp on discharge in hotter conditions when running the AC for about 2.5 hours and terminals hit 135F. These are extreme tests to see how the batteries work, I will not normally be attempting to run my AC off them, if you wanted this kind of continuous draw/charge you need good cooling specifically on the top of the battery which is where the BMS is.
I find it interesting that SOK's specifications are so much more conservative than the BMS configurations. On one hand, I applaud them for being conservative in their advertising. You usually see the opposite with vendors overstating their capabilities. On the other hand, they aren't doing their customers any favors by letting the BMS's run at 150a continuously with that much resistance/heat and voltage drop. It's not likely to kill them by running tests a few times, but I'm sure some people are overloading them frequently without even understanding what they are doing. Based on your testing, it sounds like BMS temp may be the primary cutoff criteria in their current BMS settings rather than "> x amps for y seconds". Why allow that kind of abuse to happen when it dramatically exceeds their stated specs? It's totally reasonable to allow a 10-30 second surge through the BMS, but I question why they allow it to go on for 10+ minutes. Maybe they are cutting things off at a really safe heat level, but I suspect those BMS's are getting super hot in a hurry when you see that much voltage drop (assuming the drop is across the BMS's).

I'm not saying the SOK batteries are bad, just wonder what the logic was allowing the BMS's to run like this.
 

jharrell

New Member
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Aug 11, 2021
Messages
36
They state 200 amps for 3 seconds and 300 amps for 16ms on their spec sheet for surge. There isn't anything magic about 150 amps vs 100 amps continuous, just increase the size and or number of mosfets and make sure all traces and connecting wires can handle the current along with large enough heat sinks. Based on the physical size of SOK's BMS which looks to be significantly larger than Battelborns it doesn't seem suspicious that it can handle more continuous current. There are other mosfet based BMSs around up to 300amps continuous or more.

There wasn't much voltage drop, and it took a significant amount of time for the battery to heat up, in my 10 minute test it went from 70F to 99F, the spec sheet lists 149F as the BMS over temp cutoff probably on the heat sink, which is why I would see it occur at 125-135F at the negative terminal. Again I would hope their actual programed limits are within a significant safety margin otherwise they should lower them, I can understand recommended charge/discharge vs the actual limits as well and I wish they where more clear about it.

I was actually more trying to determine if there was an actual 50 amp charge rate cutoff, but as I suspected it is the same as the discharge limit since for the BMS it doesn't really matter which way the current is flowing as far as how much it can handle. Since my charger can max out at 125amps which ends up around 110amps at the battery I wanted to see if there was issue with exceeding the 50 amp charge "limit" on the SOK's since the Gafeng cells can handle 1C charge and 0.5C recommended which would be 206 and 103 amps respectively and I am just maxing out at 55amps per battery. Not sure where they get 40 amps recommended charge on the 206's as that only around 0.2C.
 

corn18

Village Idiot
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Sep 9, 2021
Messages
325
Finished cleaning up my install. I ended up removing everything including the batteries and painting the whole compartment with high temp paint. I also added Lynn wool behind the components. Should be all set until I decide to change something else.


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DC wiring 290RL.jpg
 
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