Solar charges, SOC goes down?

[LeoKa]

I have been trying to see if CombiMaster will go into charging, but no luck so far. The SOC is down to 34% and the voltage is 13.09V. My load is mostly lights. I turned on the nav instruments for a day and sometimes pumps run. The draw right now is 3.4A, so it will go down slowly. I did not use solar charging since I started this test. Let's see how low the batteries will go, before they shut down.
The MasterAdjust software monitoring pretty much shows the same thing. I don't think it shows anything accurately. If CombiMaster is completely out of commission, that can explain it. The fan come on couple times on CombiMaster, but I think it was temperature. I had to turn on the furnace two days ago.

 

[SteveK]

3.4A load is nothing. put a load of more than 10a on it. If the charger does not start bulk charging below 12.8v then it is toast.

 

[twistedtree]

I have been trying to see if CombiMaster will go into charging, but no luck so far. The SOC is down to 34% and the voltage is 13.09V. My load is mostly lights. I turned on the nav instruments for a day and sometimes pumps run. The draw right now is 3.4A, so it will go down slowly. I did not use solar charging since I started this test. Let's see how low the batteries will go, before they shut down.
The MasterAdjust software monitoring pretty much shows the same thing. I don't think it shows anything accurately. If CombiMaster is completely out of commission, that can explain it. The fan come on couple times on CombiMaster, but I think it was temperature. I had to turn on the furnace two days ago.

I wouldn't waste any time on the combi, or anything that depends on it like masteradjust. We know it's junk, so you are just poking at a dead body.


The only thing I would consider spending time on would be to open it up and see if there happens to be an internal fuse that blew. But only do that after disconnecting EVERYTHING from the combi, and even then, assume there are residual high voltages inside. In fact, get someone else to do it. I don't mean offense, but it's something you are unqualified to do safely. It's something you need to learn only with a knowledgeable person at your side.

 

[LeoKa]

I might sent the CombiMaster to a repair shop. Depends how much they charge.

 

[LeoKa]

The new inverter/charger has arrived, but I cannot get to it for couple weeks.
Meanwhile, the battery bank voltage is down to 12.67V, which means the CombiMaster is blind and dead. The draw down goes slow, even with 14.2A load on the battery bank. I will let it go all the way to shut down as a test. I want to see, when will the BMS turn off the batteries? The battery manual suggests 10.5-11.8V BMS cutoff.

 

[Bmarler]

You’ve got to be happy with the performance of the batteries. You’ve been drawing them down for quite a while now. It’ll be interesting to see how fast they come back up when you get the new charger online.
I don’t have much experience with lithium banks yet, but is it harmful to discharge to the point where the bms drops them out?

 

[LeoKa]

You’ve got to be happy with the performance of the batteries. You’ve been drawing them down for quite a while now. It’ll be interesting to see how fast they come back up when you get the new charger online.
I don’t have much experience with lithium banks yet, but is it harmful to discharge to the point where the bms drops them out?

Yes, you are making a good point and secretly I was worried about this myself. The draw down has taken about a week, which is a good news. It means, my house usage on 12V can be on for over a week, without any charging available. The AC side is another story, since it needs the inverter. I did a test in the past for AC/DC load and the battery bank lasted for 3.5 days, while I was on board. This means occasional pump runs, espresso machine, head use. This was before I had the solar system up.
The test I ran now, with solar off, inverter/charger dead, but AC is on from shore using the passthrough. If there is no AC usage on the boat and I am away for longer period, the 12V is still good for over a week or longer, since I was turning on all lights, navigation instrument, heating circulation pump, etc. In case of power outage in the city, this can be important.
If we add the solar charging, the boat can be by itself indefinitely on 12V.

About the test.
I started over a week ago, having 12V on only. Finally last night, the battery bank went down enough for the BMS to turn off the bank for safety. I believe, it was at 10.2V as the lowest setting by the BMS. This morning, the 12V system was all out. Nothing worked on 12V, even the battery monitor was off. I activated the solar chargers and waited to see some charges. For a while nothing happened. Of course, at this time, big rain clouds were passing by, so the panels were mute. However, once there was a little clearance, the lights on the MPPTs started to blink. Soon, all of them become steady and the charging started. I could see this on my computer software. The 12V system was not alive until the battery bank reached 12.01V. This took about 35-40 minutes. After this point, the 12V system was available and the battery monitor come alive, too. The charging is still on. Luckily the sun come out and gave a boost to the charging current. At one point, the panels provided 41.5-42.2 amps to the batteries. As the voltage started to rise on the batteries, the amps got lower. Right now, it is still in ' bulk ' mode, but the current is only 12.45A.
I believe that the solar system and BMS passed the tests. I feel better now, because my goal was to have a system, which can provide to the boat, while I am away for few months. Yes, I will have the new inverter/charger installed, so AC can run, too. But that only applies for few weeks periods. If I am away for months, the AC appliances will be turned off and only 12V will be on. Plus, the new Renogy inverter/charger has remote access feature, so I could monitor the batteries from any location, as long the wifi in the marina is active.

 

[LeoKa]

The only thing I would consider spending time on would be to open it up and see if there happens to be an internal fuse that blew.

I am happy to report back to you that I resurrected the Mastervolt Combimaster. As you have stated, it was the blown fuses from the polarity crossing. The fuses were cheap. The access to the section with the burned fuses was a little tricky, but I figured it. Now I have a working inverter again.
Since I ended up with two inverters, I decided to create redundancy. I installed an AC auto switch and connected both sources. One bank/inverter from Renogy, another bank/iinverter from Mastervolt. Today, I had a test by eliminating one source and the switch moved nicely to the other providing for the AC loads. Once the main AC source was restored, the switch migrated back to the original source.
I am quite happy with it, particularly with the recovery of the dead inverter.