Unable to reconnect to Victron 100/20

[marter]

Thanks for the replies Rich and Bob. I have to GC-2 batteries from Sam's so no need for a BMS. Maybe someday.....

So it would appear I have 2 choices. Install the Blue Sea switch to be able to cycle the MPPT controller or rewire as Bob suggests. I think the parasitic draw on the MPPT is 0.3a. If I run it directly to the batteries will I lose BMV monitoring? Do I care? Can I run the neg to the BMV shunt and achieve both?

Thanks,
Mike

[marter]

Here's a pretty brief diagram of what I have; doesn't show everything but I think it represents what I'm asking about.


Any comments? I'm planning on changing out 10ga from MPPT output to 6ga. Anything else?


Thanks,
Mike

[Troutboy]

Mike. I don’t think that you should be having the problem I had.

From your diagram above, it looks like you should always have the mppt powered up, unlike mine. So I don’t think your issue is the same as mine with the BMS.

[marter]

Rich,

I'm starting to agree. I finally tried recycling the power on the controller and still could not discover it either with my phone or my laptop. All the while it was putting 70-80 watts into the batteries according to the BMV. I'm thinking the bluetooth may have failed.

The manual says to remove the jumper if configuring with bluetooth, which I was able to do when I first installed it and updated the firmware.. I dont see anything documented to enable or diisable discovery mode, so I assume it should always be discoverable. Not sure what else to try.

Any thoughts? Any comments on my wiring ddiagram?

Thanks again,
Mike

[Troutboy]

Mike on the wiring diagram I would add the following if possible:

1. The on/off selector from solar panels to disconnect the MPPT if needed
2. A battery disconnect on/off between shunt and battery negative
3. An inverter disconnect on/off between battery and fuse on positive inverter line
4. Optional - but would recommend a breaker 30-50 amp off battery before positive buss bar.

Also, why are there two negative lines from battery negative to shunt>

[marter]

Originally Posted by Troutboy

Mike on the wiring diagram I would add the following if possible:

1. The on/off selector from solar panels to disconnect the MPPT if needed
2. A battery disconnect on/off between shunt and battery negative
3. An inverter disconnect on/off between battery and fuse on positive inverter line
4. Optional - but would recommend a breaker 30-50 amp off battery before positive buss bar.

Also, why are there two negative lines from battery negative to shunt>

Rich,

Good observations on the switches and breaker. I have to evaluate how often I would need/use these switches vs. physically disconnecting the cable with a socket wrench. I assume this is as much a matter of convenience as necessity.

Regarding the breaker isolating the bat pos from the pos bus, I looked on AMSolar's site and it looks like a 30a breaker would run around $60. What would you think of something like this one? The protection sounds like a good idea but I need to choose where I spend.

Finally, re the pair of cables from the bat neg to the shunt, the factory used a 4ga to the Inverter and a 6ga to the neg bus, so my logic was to leave them both in place and connect them to the shunt. I haven't changed the load, just the connection point. Does that make sense or would you do it differently?

Thanks again,
Mike

[Troutboy]

Mike,

I think the disconnects are essential, for safety and ability to isolate system as needed, so those mentioned as 2 and 3 above. The last breaker at the end is (no 4) optional. I also think the stock bus bar airstream provides might have the breaker you identified above already in place, so check that out.

I am not up to knowing the codes etc, but I seem to remember that the disconnects are either required or highly recommended.

Also, I’m not sure if you need both of those wires to the shunt, but not sure if it causes any issues. I just don’t have that experience or knowledge. Maybe someone else can weigh in on that.

Thx

[marter]

Thanks for your input Rich, much appreciated. I think I'll go ahead with the disconnects. The wiring diagram for my trailer refers to 20, 30 and 50a breakers built into the pos bus bar so I believe it's already protected. I'm going to trace each cable to see that nothings been moved.

I'll post a new thread on the two cables from the battery. It seems logical to me but I'm no expert either.

I'm going to call AMsolar today and order the disconnects and a new MPPT controller. I'm hoping that its the bluetooth module failing on the one I have in now. Don't know what else to try, and I can't get Amazon tech support to answer the phone. 🤔

Thanks again,
Mike

[Pencilpusher]

Originally Posted by Troutboy

Mike,

I think the disconnects are essential, for safety and ability to isolate system as needed, so those mentioned as 2 and 3 above. The last breaker at the end is (no 4) optional. I also think the stock bus bar airstream provides might have the breaker you identified above already in place, so check that out.

I am not up to knowing the codes etc, but I seem to remember that the disconnects are either required or highly recommended.

Also, I’m not sure if you need both of those wires to the shunt, but not sure if it causes any issues. I just don’t have that experience or knowledge. Maybe someone else can weigh in on that.

Thx

Mike:

Regarding your wiring diagram, the stock Airstream wiring has a 100 amp terminal post fuse on the 4ga positive wire leading to the inverter. It is also my understanding that the positive buss bar has a 50 amp fuse built into the bar.

There is not really any reason to have the two negative leads off the battery to the shunt. From what I have seen the preferred setup is to always have single leads off both the positive and negative leads from the battery to a shunt or disconnect switch.

Eric

[uncle_bob]

Originally Posted by marter

Thanks for the replies Rich and Bob. I have to GC-2 batteries from Sam's so no need for a BMS. Maybe someday.....

So it would appear I have 2 choices. Install the Blue Sea switch to be able to cycle the MPPT controller or rewire as Bob suggests. I think the parasitic draw on the MPPT is 0.3a. If I run it directly to the batteries will I lose BMV monitoring? Do I care? Can I run the neg to the BMV shunt and achieve both?

Thanks,
Mike

Hi

At 0.3A, yes, you would care. Even at the ~0.02A it pulls, you eventually will care, but that is below the cut out point most people have set on the BMV.

Bob

[marter]

Originally Posted by Pencilpusher

Mike:

Regarding your wiring diagram, the stock Airstream wiring has a 100 amp terminal post fuse on the 4ga positive wire leading to the inverter. It is also my understanding that the positive buss bar has a 50 amp fuse built into the bar.

There is not really any reason to have the two negative leads off the battery to the shunt. From what I have seen the preferred setup is to always have single leads off both the positive and negative leads from the battery to a shunt or disconnect switch.

Eric

Eric,

You're correct on the fuse sizing, at least closer than I am. I believe it's actually 110a but in the process of verifying.

Regarding the pair of negative cables, here's my logic. The trailer was built with two 12v batteries in parallel and Airstream used 4ga cables to the inverter and 6ga cables to the positive and negative buss', a pair from each battery to balance the load.

I've gone to two 6v batteries in series, so only one positive and negative connection point instead of two. I haven't reduced the potential load, just the number of connection points. So it makes sense to me to use both cables.

Adding the Victron BMV-712 and shunt, I need all negative cables from the batteries on one side of the shunt. So the same capacity but one connection.

I don't know if this is the right way to do it but I'd hate to run that load over one cable without increasing the size. This would seem to do the same thing without running a much larger cable.

Any thoughts? Anyone else that's converted to 6v batteries, what did you do?

Thanks,
Mike

[marter]

Originally Posted by uncle_bob

Hi

At 0.3A, yes, you would care. Even at the ~0.02A it pulls, you eventually will care, but that is below the cut out point most people have set on the BMV.

Bob

Bob, you're absolutely correct, thanks for the catch.

I'm going with the 4 post Blue Sea switch to isolate the solar ahead of the controller and another Blue Sea switch to isolate the batteries while in storage.

Still not getting bluetooth to work even after power cycling the controller so assuming the bluetooth module has failed.

Any thoughts, including my pair of neg cables to the shunt? I'm barely above water here.

Thanks,
Mike

[uncle_bob]

Originally Posted by marter

Eric,

You're correct on the fuse sizing, at least closer than I am. I believe it's actually 110a but in the process of verifying.

Regarding the pair of negative cables, here's my logic. The trailer was built with two 12v batteries in parallel and Airstream used 4ga cables to the inverter and 6ga cables to the positive and negative buss', a pair from each battery to balance the load.

I've gone to two 6v batteries in series, so only one positive and negative connection point instead of two. I haven't reduced the potential load, just the number of connection points. So it makes sense to me to use both cables.

Adding the Victron BMV-712 and shunt, I need all negative cables from the batteries on one side of the shunt. So the same capacity but one connection.

I don't know if this is the right way to do it but I'd hate to run that load over one cable without increasing the size. This would seem to do the same thing without running a much larger cable.

Any thoughts? Anyone else that's converted to 6v batteries, what did you do?

Thanks,
Mike

Hi

Unless you are pulling crazy large currents from the batteries, a single cable will do fine. The trick is to make sure it is a fat enough cable. If you have a #6 and a #4 right now, go with a #2 for your single cable. (Amazon will be happy to sell you a pre-made cable).

======

The interesting thing about the giant fuse on the inverter is that it's at the wrong end of the wire. The battery is the power source. The cable is what you are protecting. The protection is at the load end rather than the source end ... hmmm.... Yes, if you put the fuse away from the inverter and bury it somewhere, who would ever find it if it blew ....

Indeed that part gets really weird when you go to an inverter / charger. You now have a battery at one end ( a power source) and a charger at the other end (also a power source). Two fuses ... lots of fun. Run two cables between them, now you need four fuses .... yikes !!!! ... good luck troubleshooting that .....

If the cable is 12" long, all this sort of does not matter. If it's 20' long ... well it does matter.

Bob

[marter]

Thanks Bob. Good point on the inverter fuse. And I don't see an inverter/ charger in the future, at least not in this trailer. I'm already way too far down this slippery slope of not leaving well enough alone. My DW keeps asking me if I have an off switch, and she's not talking about in the trailer.

So help me understand why staying with the pair of cables is a bad idea. We hardly use the 600w inverter, but I don't want to forgoe it completely.

I assume that power over the negative cable(s) will take the path of least resistance, i.e. the 4 ga cable. But doesn't that resistance increase as amperage increases? So electrons would start to flow over the 6 ga cable, right? Does it "self balance" based on resistance?

Not trying to be obstinate, just wanting to learn. And maybe save a little money and effort. But not if it's stupid or dangerous.

Thanks in advance,
Mike

[uncle_bob]

Originally Posted by marter

Thanks Bob. Good point on the inverter fuse. And I don't see an inverter/ charger in the future, at least not in this trailer. I'm already way too far down this slippery slope of not leaving well enough alone. My DW keeps asking me if I have an off switch, and she's not talking about in the trailer.

So help me understand why staying with the pair of cables is a bad idea. We hardly use the 600w inverter, but I don't want to forgoe it completely.

I assume that power over the negative cable(s) will take the path of least resistance, i.e. the 4 ga cable. But doesn't that resistance increase as amperage increases? So electrons would start to flow over the 6 ga cable, right? Does it "self balance" based on resistance?

Not trying to be obstinate, just wanting to learn. And maybe save a little money and effort. But not if it's stupid or dangerous.

Thanks in advance,
Mike

Hi

If (for whatever reason) the #4 comes loose, you have all the current through the #6 cable. Unfortunately there are a lot of ways for lugs and cables to get mucked up. If you have a single cable and it goes out .... all current stops.

Is that a big deal? No, it's not a massive, this will kill you today issue. The only issue like that is not having a 4x4, F-350 dually diesel with a $4,000 hitch .... (to pull your 19' trailer ..... ).

Bob

[marter]

Got it. Thanks for hanging in here with me.

Mike

[ASIS17]

This most likely isn't related, but I have 6 different bluetooth devices installed on my phone. I rarely have an issue with any of them except the AS audio system. I found that if I put the AS into the store setting, I have to remove the system from my phone and re-add it each time, to get it to work. Sounds way too simple to be a similar problem though.

[marter]

Thanks, but i've tried that multiple times. Problem is I'm unable to rediscover the MPPT controller. I have a new one waiting to go in as a replacement and hopefully that will solve the problem.

Thanks,
Mike

[Troutboy]

For what it’s worth. I switched the the negative Oitpit from the controller as described above and now my controller always has power and it’s working great. Hope you figure out your issue soon. Keep us posted.

[marter]

Thanks Rich. I'm hoping it was the MPPT's bluetooth module. We'll see.

I'm waiting for a chance to bring the trailer home from storage so I can remove the old 50w panel, install the two 100w Renogy panels on the roof, new MPPT controller, and Blue Sea switches. I'll post the results soon.

Thanks again,
Mike