For 48V systems (which can achieve 56V) where do you folks source things like breakers?

[MegaMosquito]

I see tons of DC breakers rated at 48V but I am thinking that a breaker that is rated for 48V is not safe for a 48V (nominal) system. My 48V system will actually run at about 56V. It seems I can buy fuses rated at 58V and above, but I am struggling to find a appropriate *breakers* for this voltage (e.g., for 200A and 56 or more volts).

Can anyone please suggest suppliers for 56VDC (or better) breakers?

Glen.

 

[B-ManFX4]

https://mou.sr/3PYTGJ2

 

[MegaMosquito]

That's awesome @B-ManFX4 ! Thank you so much! I actually looked on Mouser before posting but apparently my searching skills are terrible.

A related question but maybe this is the wrong forum. I am planning an isolator switch for the solar panels, and a breaker for the battery side. But I have read that the solar panels should only be attached to the Victron Multiplus II when the battery is connected. So I am worried that if the breaker trips while the solar panels are attached the Multiplus II then it may get damaged. Do I need to wire a relay so that battery disconnection on the battery side (when the breaker trips) also turns off the soar panels? Or how do folks usually handle this?

 

[B-ManFX4]

Your solar panels will wire into a MPPT controller. The MPPT output is typically wired into the battery bank via a bus bar. The Multiplus-II is typically wired into the battery bank via the same bus bar. Where are you putting the battery breaker?

 

[MegaMosquito]

Yes, sorry. I meant the MPPT, not Muiltiplus II. When the breaker trips, the solar will remain connected to the MPPT, and I think I read that this is a problem. Maybe I need to go back and re-read the MPPT documentation?

This is my current design schematic (haven't bought any of it yet):

 

[B-ManFX4]

I am not a fan of breakers on the battery side of the system. A properly sized fuse and a battery switch is a more reliable solution, IMHO. Victron sells 275 amp battery switches for about $35 - put one on each battery feed in place of the 58V 200 amp breaker in your diagram. If you need to take a battery out for some reason you can still have the other battery in place and working. FWIW I also have two battery switches between my bus bar and my two Multiplus units. Not having to disconnect cables when working on a system is very handy - especially in tight quarters.

If I were you I'd look at saving some cash by using a more appropriately sized MPPT. A 150/100 is way overkill for your proposed solar array. Unless you plan to add a large number of panels I'd consider a more moderately rated MPPT.

At Current Connected the 150/100 MPPT is $516.30. It can deliver a whopping 5,800 watts @ 48VDC. The 150/35 MPPT is $184.45 and it can deliver 1,800 watts @ 48 VDC. Both solutions can deliver way more power than your proposed solar array is capable of generating.

I see you haven't come up with a 12VDC power solution for the RV. It isn't the most efficient method but for starters you can just leave your existing 120VAC to DC converter in place and let the MP-II power it like shore power does. Are you keeping a 12VDC battery for things like the tongue jack, stabilizers, etc.? Getting a 48VDC to 12VDC converter that has serious ampacity is a trick. My RV system is 24VDC so I used a Victron Orion 24-12 100 amp unit for the DC power side. It is way overkill but I didn't do enough research before I started buying parts.

Current Connected has the Victron Orion-TR 48/12 DC-DC converter for $201.45. It can output 30 amps and you can parallel units for more capacity if needed. The money you save buying the 150/35 MPPT instead of the 150/100 MPPT will more than pay for the Orion !!!

As far as proper sequence for starting and stopping the MPPT, you are correct - you should shut down PV first and then remove battery power. On start up you apply battery power first and then apply PV power. From the 150/35 MPPT solar charger manual:

Page 34 - Operation

6.5. Shutdown and restart procedure

The solar charger is always active when the PV and/or the battery terminals are powered. The solar charger does not have an
on/off switch.

To shut down the solar charger, perform these steps in the prescribed order:
1. Disconnect the PV supply to the solar charger by switching the PV supply off or by removing the external fuse(s) or circuit breaker(s).
2. Disconnect the battery supply to the solar charger by switching the battery supply off or by removing the external fuse(s) or circuit breaker(s).

To restart the solar charger after it was shutdown, perform these steps in the prescribed order:
1. Connect the battery supply to the solar charger by switching the battery supply on or by inserting the external fuse(s) or circuit breaker(s).
2. Reconnect the PV supply to the solar charger by switching the PV supply on or by inserting the external fuse(s) or circuit breakers(s).

 

[MegaMosquito]

I am not a fan of breakers on the battery side of the system. A properly sized fuse and a battery switch is a more reliable solution, IMHO. Victron sells 275 amp battery switches for about $35 - put one on each battery feed in place of the 58V 200 amp breaker in your diagram. If you need to take a battery out for some reason you can still have the other battery in place and working. FWIW I also have two battery switches between my bus bar and my two Multiplus units. Not having to disconnect cables when working on a system is very handy - especially in tight quarters.

Thanks for replying with such detail! All of this is very helpful to me.

I like the above suggestion very much and will put a switch on each battery. That will be very convenient.

If I were you I'd look at saving some cash by using a more appropriately sized MPPT. A 150/100 is way overkill for your proposed solar array. Unless you plan to add a large number of panels I'd consider a more moderately rated MPPT.

At Current Connected the 150/100 MPPT is $516.30. It can deliver a whopping 5,800 watts @ 48VDC. The 150/35 MPPT is $184.45 and it can deliver 1,800 watts @ 48 VDC. Both solutions can deliver way more power than your proposed solar array is capable of generating.

Good point. Once I settle on the final PV array, I'll re-size the MPPT appropriately. From discussions in another thread I am planning to actually use two MPPTs (and both will need to be sized appropriately).

I see you haven't come up with a 12VDC power solution for the RV. It isn't the most efficient method but for starters you can just leave your existing 120VAC to DC converter in place and let the MP-II power it like shore power does. Are you keeping a 12VDC battery for things like the tongue jack, stabilizers, etc.? Getting a 48VDC to 12VDC converter that has serious ampacity is a trick. My RV system is 24VDC so I used a Victron Orion 24-12 100 amp unit for the DC power side. It is way overkill but I didn't do enough research before I started buying parts.

Current Connected has the Victron Orion-TR 48/12 DC-DC converter for $201.45. It can output 30 amps and you can parallel units for more capacity if needed. The money you save buying the 150/35 MPPT instead of the 150/100 MPPT will more than pay for the Orion !!!

Lol. There seem to be a lot of inexpensive DC/DC buck converted (like $40-ish on Amazon) that can do 40A at 12V from a 48V (or 24V) system. I will check out the Victron Orion line too. I really like every product I have seen from Victron so far.

As far as proper sequence for starting and stopping the MPPT, you are correct - you should shut down PV first and then remove battery power. On start up you apply battery power first and then apply PV power. From the 150/35 MPPT solar charger manual:
...

So I wasn't going crazy. It was in the manual! Thanks for digging that up.

This makes me think I should power normally open relays for connecting the PVs to the MPPTs. Then if the battery power goes off for any reason (a fuse blows, or I stupidly turn off both batteries) the relays will protect the MPPTs by disconnecting their PVs. To me that seems like something they should have built-in to the MPPTs if it is such an important concern.

Thanks again. I'm revising my design based on comments from you and others and will create a new post to seek feedback on that... probably in a few days.

 

[B-ManFX4]

Thanks for replying with such detail! All of this is very helpful to me.

I like the above suggestion very much and will put a switch on each battery. That will be very convenient.

Good point. Once I settle on the final PV array, I'll re-size the MPPT appropriately. From discussions in another thread I am planning to actually use two MPPTs (and both will need to be sized appropriately).

Lol. There seem to be a lot of inexpensive DC/DC buck converted (like $40-ish on Amazon) that can do 40A at 12V from a 48V (or 24V) system. I will check out the Victron Orion line too. I really like every product I have seen from Victron so far.

So I wasn't going crazy. It was in the manual! Thanks for digging that up.

This makes me think I should power normally open relays for connecting the PVs to the MPPTs. Then if the battery power goes off for any reason (a fuse blows, or I stupidly turn off both batteries) the relays will protect the MPPTs by disconnecting their PVs. To me that seems like something they should have built-in to the MPPTs if it is such an important concern.

Thanks again. I'm revising my design based on comments from you and others and will create a new post to seek feedback on that... probably in a few days.

I don't know if this will help or hurt but here is an as-built diagram for the system I have installed in my RV. Note that there are only 3 panels installed on the RV - the other 3 panels are ground-deployed when needed:

 

[Brucey]

I see tons of DC breakers rated at 48V but I am thinking that a breaker that is rated for 48V is not safe for a 48V (nominal) system. My 48V system will actually run at about 56V. It seems I can buy fuses rated at 58V and above, but I am struggling to find a appropriate *breakers* for this voltage (e.g., for 200A and 56 or more volts).

Can anyone please suggest suppliers for 56VDC (or better) breakers?

Glen.

Midnite Solar 250Amp 125VDC Panel Mount Breaker

Click here for Midnite Solar, Inc. Midnite Solar 250Amp 125VDC Panel Mount Breaker from altE® - Making Renewable Do-able since 1999.

www.altestore.com