[Feedback Please] RV Plans: LiFePO4+Growatt+Electrodacus SBMS0

[andrewl04]

I am close to finalizing my plans for my travel trailer. This will be my first full install so I want to check myself. I have tried to incorporate all the best practices I have seen on this forum. Thanks in advance for your feedback.

I have attached my plans as a PDF. (Happy to share the .drawio file once revised/complete if anyone wants. I was hesitant to share since it is an 11MB file)

A few specific areas I wanted to check; letters below correlate to the lettered circles on the diagram:
b/g. I was considering using DIN mounted mini breakers for PV and shore power protection. Any feedback over flat mounted ones?
c/j. Confirming PV and battery shunts on positive wires per Electrodacus spec?
d. Do I need a SSR to allow the Electrodacus SBMS0 to isolate the PV input from the Growatt 24v SPF 3000TL LVM?
e. Confirming SBMS0 to control the Growatt inverter by wiring into the Growatt's switch?
f. Confirming the need for a SSR to allow the SBMS0 to control shore power isolation by only isolating the line (not neutral) of the AC circuit?
u. I have seen some posts about using a AC GFI breaker between the inverter output and my main panel [f] to reduce the risk of AC somehow making a circuit via the trailer frame/etc. Needed? Any feedback?
General question: Am I fused at all the right locations? Anything I don't need? Feedback on the amps I calculated?

Thanks!

 

[HRTKD]

I'm not familiar with the Electrodacus landscape, but shouldn't the shunt be between the battery and the common bus bar?

 

[andrewl04]

I'm not familiar with the Electrodacus landscape, but shouldn't the shunt be between the battery and the common bus bar?

A bit odd I realize but that is actually by design; from the SBMS0 manual (see step 4):
The Battery current shunt is mandatory as it is needed to calculate the battery SOC (State of Charge) and gets connected to Battery+ terminal on one side then on the other side to a fuse or circuit breaker and your Load and chargers.
The PV current shunt will be great to have as it will provide way more info than just with just the battery current shunt mentioned above all you see is battery current and you have no idea of how much the load uses or how much the PV array is producing.

 

[andrewl04]

A bit odd I realize but that is actually by design; from the SBMS0 manual (see step 4):
The Battery current shunt is mandatory as it is needed to calculate the battery SOC (State of Charge) and gets connected to Battery+ terminal on one side then on the other side to a fuse or circuit breaker and your Load and chargers.
The PV current shunt will be great to have as it will provide way more info than just with just the battery current shunt mentioned above all you see is battery current and you have no idea of how much the load uses or how much the PV array is producing.

@HRTKD I may have missed your valid point at first read... the shunt should be closer to the battery on the other side of the bus bar. I’ll fix that. Thanks!

 

[andrewl04]

I updated the diagram to reflect the above correction for the battery shunt location. Please see this version and NOT the one in my first post.

 

[HRTKD]

@HRTKD I may have missed your valid point at first read... the shunt should be closer to the battery on the other side of the bus bar. I’ll fix that. Thanks!

Glad I can help. I can spot obvious stuff. The rest of it is all greek to me since it's Electrodacus.

 

[grizzzman]

I updated the diagram to reflect the above correction for the battery shunt location. Please see this version and NOT the one in my first post.

There will be some level of voltage drop caused by your switch. Swap the shunt and switch.

 

[andrewl04]

There will be some level of voltage drop caused by your switch. Swap the shunt and switch.

Makes sense. Any safety concerns by not being able to isolate the shunt from the battery? Or in the rare occurrence I need to do something there I just disconnect the battery itself?
Thanks

 

[HRTKD]

I'm using DIN rail mounted DC breakers. Nice and compact for my situation. I use dual pole for each incoming string of solar panels. I have a couple single pole breakers that I use just to turn things on/off like the battery warming pads. I couldn't find a decent wall mount switch that I was happy with, and I had room on the rail.

You said "travel trailer". It's not a fifth wheel, correct?

 

[andrewl04]

I'm using DIN rail mounted DC breakers. Nice and compact for my situation. I use dual pole for each incoming string of solar panels. I have a couple single pole breakers that I use just to turn things on/off like the battery warming pads. I couldn't find a decent wall mount switch that I was happy with, and I had room on the rail.

You said "travel trailer". It's not a fifth wheel, correct?

Good to hear about the DIN breakers. I haven’t seen a lot of them around here so good to confirm they are a good option. Thanks
Is a dual pole necessary for the solar inputs vs. just the positive? Dual needed for safety/maintenance isolation?

Correct, not a fifth wheel. It’s a 32’ Keystone Passport (bumper pull). Curious why you were asking?

 

[HRTKD]

Good to hear about the DIN breakers. I haven’t seen a lot of them around here so good to confirm they are a good option. Thanks
Is a dual pole necessary for the solar inputs vs. just the positive? Dual needed for safety/maintenance isolation?

Correct, not a fifth wheel. It’s a 32’ Keystone Passport (bumper pull). Curious why you were asking?

You can find a decent selection on both the Bay Marine Supply and Alt-e sites. Keep an eye out for a label that indicates that the breaker is polarity specific. You have to wire them according to the instructions. Polarity specific breakers are not to be used between an inverter/charger and a battery because power goes both ways.

I asked about trailer type because fifth wheel trailers often have rather high amp loads that are 12v. This requires a very large 24v to 12v converter or multiple converters to handle the load.

 

[andrewl04]

You can find a decent selection on both the Bay Marine Supply and Alt-e sites. Keep an eye out for a label that indicates that the breaker is polarity specific. You have to wire them according to the instructions. Polarity specific breakers are not to be used between an inverter/charger and a battery because power goes both ways.

I asked about trailer type because fifth wheel trailers often have rather high amp loads that are 12v. This requires a very large 24v to 12v converter or multiple converters to handle the load.

Thanks for the tips on the breakers.

My 12v loads are fairly small. Thanks for checking. One slide is biggest single 12v load. I was planning on a 40a 24v to 12v converter. I will mount it right next to my existing DC distribution/fuses. I’m hoping to re-use the 6AWG run from there to original 12v battery location since that is near where I will be mounting the inverter. If that works as planned the only long wires will be the AC shore power to the inverter and the return AC to power the original AC panel. That will make for an easier effort of pulling behind the chloroplast.

 

[Whinny]

You may want to go with a class T fuse coming off the battery-there is lots of talk on this, then to the shunt, to your switch. I like the idea of a mrbf type fuse block instead of the buss bar-keeps things neater and everything past the switch needs a fuse anyways. You don't need the 30a fuse between the 2 converters. Are you keeping a 12v battery for the trailer brakes?

 

[grizzzman]

Makes sense. Any safety concerns by not being able to isolate the shunt from the battery? Or in the rare occurrence I need to do something there I just disconnect the battery itself?
Thanks

No

 

[andrewl04]

You may want to go with a class T fuse coming off the battery-there is lots of talk on this, then to the shunt, to your switch.

I had seen some talk of this but wasn’t sure if my setup would benefit from a class T. I guess when it comes to the inverter it wouldn’t hurt. Thanks for the suggestion.

I like the idea of a mrbf type fuse block instead of the buss bar-keeps things neater and everything past the switch needs a fuse anyways.

Are you thinking something like the Victron Lynx distributor? Anything cheaper that would work effectively?

You don't need the 30a fuse between the 2 converters.

Ok thanks. Wasn’t sure. Figured better to be safe and add until someone told me otherwise.

Are you keeping a 12v battery for the trailer brakes?

My trailer has a separate battery for the runaway brakes protection that will plan to keep charged of the 7-way harness from the tow vehicle.

Or do I also need 12v to power the brakes for regular use? I thought that power came from the tow vehicle’s brake controller. If I do need power for that I still have the FLA 12v on the tongue that I had hoped to get rid of. Or I could power off my 24v to 12v converter.

Thanks

 

[Whinny]

Your good to go on the brake front then.....
The class T is to protect the wiring from the crazy amount of amps that can be delivered by the battery in a short circuit situation.
Here is the discussion-it's long

LiFePO4 prismatic cell short circuit current and main circuit protection

I am building a LiFePO4 battery bank for my vehicle using 8x EVE 105Ah cells in a 2p4s configuration (12V, 210Ah). While not an EE, I am fairly comfortable with circuit design and protection. My question pertains to main circuit protection, specifically short circuit protection. I see a lot of...

diysolarforum.com

MRBF -I'm sure you can get a better price-but anl is fine as well

MRBF Surface Mount Fuse Block - Independent Source - Blue Sea Systems

Easily and economically satisfies ABYC 7 circuit protection rule by mounting on a 3/8 battery post, battery switch or bus bar.

www.bluesea.com

edit-not that one...

Blue Sea Systems 5196 Fuse Block MRBF 3Circ Common, Fuse Boxes - Amazon Canada

Blue Sea Systems 5196 Fuse Block MRBF 3Circ Common in Fuse Boxes.

www.amazon.ca

probably don't want to buy from amazon.ca though...

Blue Sea Systems 5196 MRBF Surface Mount Fuse Block, Common Source | Waytek

Blue Sea Systems 5196 MRBF Surface Mount Fuse Block, Common Source is in stock and ready to ship. Order today!

www.waytekwire.com

 

[HRTKD]

Or do I also need 12v to power the brakes for regular use? I thought that power came from the tow vehicle’s brake controller. If I do need power for that I still have the FLA 12v on the tongue that I had hoped to get rid of. Or I could power off my 24v to 12v converter.

The brakes, while driving, are energized by the tow vehicle. This is a variable amount of current. Should the breakaway cable get pulled, the power comes from the 12v battery on the trailer for that. When that happens it is a constant level of current. I believe the current draw from each electric brake is a maximum of 4 amps. When the breakaway cable is pulled, that's 16 amps until the pin is inserted back into the breakaway box.

Relying on an infrequent charge on that battery (from the tow vehicle), could reduce the life of the battery.

I have a separate 12v lead acid battery on my trailer that will be used by the breakaway system. It is charged by a solar panel and charge controller that is separate from the rest of my trailer's system.

 

[Whinny]

I don't think it would be an issue.....

 

[andrewl04]

Your good to go on the brake front then.....
The class T is to protect the wiring from the crazy amount of amps that can be delivered by the battery in a short circuit situation.
Here is the discussion-it's long

LiFePO4 prismatic cell short circuit current and main circuit protection

I am building a LiFePO4 battery bank for my vehicle using 8x EVE 105Ah cells in a 2p4s configuration (12V, 210Ah). While not an EE, I am fairly comfortable with circuit design and protection. My question pertains to main circuit protection, specifically short circuit protection. I see a lot of...

diysolarforum.com

MRBF -I'm sure you can get a better price-but anl is fine as well

MRBF Surface Mount Fuse Block - Independent Source - Blue Sea Systems

Easily and economically satisfies ABYC 7 circuit protection rule by mounting on a 3/8 battery post, battery switch or bus bar.

www.bluesea.com

edit-not that one...

Blue Sea Systems 5196 Fuse Block MRBF 3Circ Common, Fuse Boxes - Amazon Canada

Blue Sea Systems 5196 Fuse Block MRBF 3Circ Common in Fuse Boxes.

www.amazon.ca

probably don't want to buy from amazon.ca though...

Blue Sea Systems 5196 MRBF Surface Mount Fuse Block, Common Source | Waytek

Blue Sea Systems 5196 MRBF Surface Mount Fuse Block, Common Source is in stock and ready to ship. Order today!

www.waytekwire.com

I remember reading some of that class T thread. Escaped me when I did my diagram/planning.

Any thoughts on this one (Xantrex holder + Littelfuse 300a fuse)? A lot less than Blue Sea’s class T 300a.

The Blue Sea 5196 looks like a good option for my bus bar needs. The only issue I’m seeing is the smallest fuse is 30a. I was planning on a 20a fuse there but I should still be safe on that 6AWG.

 

[Whinny]

Blue Seas has nice stuff but can be pricey, they just rename things and put "Marine" on it...
Xantrex holder looks good to me-Littlefuse is a big player.
I think #6 is good for 40a-I may be wrong...