Multi Plus II

[SolarPoweredRV]

Back from my first test in Quartzsite Az. For as small as my system is, I was happy with the performance. Going into this project my main goals were to have a few cups of coffee in the morning, watch satellite TV and be able to charge our cell phones. The weather was pretty cold so the heater ran quite a bit during the night. Most mornings my Renogy battery monitor showed 82% SOC. When the percentage dropped to about 71% and I was using the coffee maker, the Victron remote switch would light up the red LED for ''low battery''. A little confused why it would do that if I had 71% battery power left? Still much to learn.

I have attached a pic of my install on the 351M. It's tight, but is working for me.Attachment 44581

I am guessing that the way you have your batteries wired together is causing your voltage to sag, or, the internal BMS is limiting the amperage output of both batteries to just the output amperage of a single battery.

To fix this, you need to wire your batteries using a "Buss Bar" system (each battery is wired to a Buss Bar and the load is taken from the Buss Bar instead of the battery posts). When you wire your batteries to a Buss Bar, each battery can contribute 100% of it's rated capacity to the load, versus, both batteries being limited by the first battery in the parallel configuration.

Here is a research paper explaining why a "Buss Bar" system is better...

And here is a picture of the type of Buss Bar I am talking about...

[Redapple63]

I am guessing that the way you have your batteries wired together is causing your voltage to sag, or, the internal BMS is limiting the amperage output of both batteries to just the output amperage of a single battery.

To fix this, you need to wire your batteries using a "Buss Bar" system (each battery is wired to a Buss Bar and the load is taken from the Buss Bar instead of the battery posts). When you wire your batteries to a Buss Bar, each battery can contribute 100% of it's rated capacity to the load, versus, both batteries being limited by the first battery in the parallel configuration.

Here is a research paper explaining why a "Buss Bar" system is better...

And here is a picture of the type of Buss Bar I am talking about...

I agree with this especially when dealing with such a large battery bank. Additionally, I might add that it may also be good to take the batteries out and charge them separately with an external charger until they get to a known 100%, otherwise the system may be reporting an incorrect value. One battery may be at a different SOC than the others. Starting of from a known good point can help with that.

Good Luck!
Bill

[Brother_Bluto]

I've seen a couple of installs now with the MP-II mounted horizontally on top of the dog house. Any concerns about heat build-up inside the MP-II?

[Rich38]

I am guessing that the way you have your batteries wired together is causing your voltage to sag, or, the internal BMS is limiting the amperage output of both batteries to just the output amperage of a single battery.

To fix this, you need to wire your batteries using a "Buss Bar" system (each battery is wired to a Buss Bar and the load is taken from the Buss Bar instead of the battery posts). When you wire your batteries to a Buss Bar, each battery can contribute 100% of it's rated capacity to the load, versus, both batteries being limited by the first battery in the parallel configuration.

Here is a research paper explaining why a "Buss Bar" system is better...

And here is a picture of the type of Buss Bar I am talking about...

Good information. Going to be a little challenging getting all the cable lengths equal, but will probably give it a try.

[Rich38]

I've seen a couple of installs now with the MP-II mounted horizontally on top of the dog house. Any concerns about heat build-up inside the MP-II?

I haven't had to run the generator yet, so not much concern. If I need a generator, I also have a Honda 2200.

[xxn5ac]

Someone asked to see pictures of the install. Here are a few. You can’t see all the panels because there are 1-2 behind me near the ladder. I have a total of 9 panels: the 350W that came with the trailer and 8x 200W panels I installed.

You can see a picture I took of the Cerbo GX in installed by the TV. This was a rather humorous thing that happened: my wife was warming something in the microwave, one of the kids had a hair dryer going in the bathroom and the A/CS we’re running. It’s not every day I see 6kW getting pushed through the trailer, of course!

I apologize that the pictures are flipped around. I’m posting from my iPhone and Apple loves to store things flipped. I’ll try to correct when I get near a computer.

[Redapple63]

Looks awesome! Thanks for sharing!

On Edit: I rotated the pictures.

Bill

[Redapple63]

[ExNihilo]

That is pretty! I know that was rough climbing through the basement.

Here is mine

[Redapple63]

That is pretty! I know that was rough climbing through the basement.

Here is mine

Well Done. I am hoping my install looks as clean as all of you folks.

Bill