Li-thiiii-um.... continued.

[John in Santa Cruz]

If I add more solar I'll probably upgrade the 100/30 to a 100/50 or larger, and maybe even series wire the panels.

[BobG]

The larger Victron controllers get expensive so you might want to compare that to going with 24 volts and a dc-dc Orion 70 amp converter.


Or, if you decide to add and additional solar panel later then it might be less expensive to just add another 100/30 converter so leave room for it and the panel switch.



If you think you might go series for panels in the future, then you could look at Midnight Solar switch breaker and box or similar. They can handle the higher voltage so in the future you won't have to replace the panel switch.

[Brian B-P]

Originally Posted by BobG

Equipment such as inverter/charger, solar charge controller, compressor refrigerator, etc run on 24 volts or 12 volts. Take for instance the MPPT 100-30; it can deliver 30 amps to the batteries at either 12 volts or 24 volts. However, if the system is 24 volts then it is capable of delivering twice the power(?) to the batteries.

Yes, when a component (the solar charge controller in this case) is limited to a specific current (in this case output current), then doubling the voltage will double the power which can be handled.

[oreo]

I have purchase a 20 amp dc to dc Renogy very affordable . I believe reading the trailer wiring diagram should be enough at 8 AWG size to install this unit with out problems . Also bought three Renogy100 amps lithium for storage just have to upgrade the truck wire to 10 AWG from the battery to the truck plug and also 6AWG upgrade wire and fuse from the WFCO to the batteries .
Do you think I got this right ?

[John in Santa Cruz]

I'm probably going to pull the AWG 4 I have from the battery to the main ground point, and to the battery cutoff switch, then run 6 from the cutoff switch to the batt+ terminal on the fuse board as I'm pretty sure 4 is too thick to fit..

[Kirt]

Originally Posted by John in Santa Cruz

I'm probably going to pull the AWG 4 I have from the battery to the main ground point, and to the battery cutoff switch, then run 6 from the cutoff switch to the batt+ terminal on the fuse board as I'm pretty sure 4 is too thick to fit..

I just looked at my WFCO. The lug size says #14-#2.
Yours looks like Rubicons' which has #4-14 stamped on the lug. The fun part will be bending wire the way you like.

[John in Santa Cruz]

So when I rewire my power stuff, I am planning to put a 100A fuse inline with the + side of the batteries, right next to them, and then run directly to the power center + input (with a terminal strip in the middle for the solar).

I note there are TWO of those thermal breakers over near the WFCO power center... I was going to get rid of them as they aren't adequate for the 55A potential charging current, I'm assuming one is inline between the battery and DC Converter, so whats the other one?

here's a mockup of the wiring board as I'm imagining it (just stuff sitting on a scrap of foamcore I had lying around). Pretend the 100A fuse in the upper right is instead my SmartShunt, inline with the battery ground. That cutoff switch is for the PV so I can switch them off before disconnecting the battery.

[Vermilye]

If your trailer was wired the same as my 2017 21, one of the thermal breakers was between the batteries & the WFCO converter, and the other between the output of the solar controller & the batteries. I also got rid of both of them.

[John in Santa Cruz]

hah, this image is a link to a google drawing, so likely will change when I edit the drawing, but you'll have to hit F5/refresh to get the update in a browser.

since I posted it, I added a rough version of the power center, I still need to add the e-brake

[John in Santa Cruz]

I'm assuming the MPPT is short proof, and that I only have to fuse the batteries themselves. while that drawing doesn't show it, I do believe I'm going to run separate + and - wires from each battery to the fuse and shunt respectively, so that I can use the terminal insulator/covers that the SOK's came with, as they can't deal with 2 AWG 4 wires on a single terminal. this is in lieu of bridging the batteries directly.

btw, those big batts DO fit all the way in the back corner, so my wife can use the storage under the curbside bench, which is 'her' bench, and I can still access the batt terminals to remove/replace them if ever needed.

[dstreight]

You might find this valuable: https://youtu.be/s1P31hxlD3I

For my disconnects between the panel/panel array and the controller along with controller to battery, I used a double pole disconnect; a circuit breaker can be utilized to combine disconnects and circuit protection in one device. https://youtu.be/HOXnWXvLXko

[John in Santa Cruz]

Originally Posted by dstreight

You might find this valuable: https://youtu.be/s1P31hxlD3I

For my disconnects between the panel/panel array and the controller along with controller to battery, I used a double pole disconnect; a circuit breaker can be utilized to combine disconnects and circuit protection in one device. https://youtu.be/HOXnWXvLXko

ugh, i don't want to listen to this guy talking about himself for 7 minutes in order to get 20 seconds of actually useful info. whats the short version?

I'm putting that cutoff switch on the PV side, so I can disconnect the solar panels before I disconnect the battery from the system for maintenance or whatever, the MPPT docs suggest that you should always connect battery to it before the solar.

I know the solar panel itself won't output more than like 8.5 amps even dead short, and that the original AWG10 wires from the roof should handle that adequately. My PV wiring should be *very* robust, I got the 'wirebox' option for the MPPT that acts as a strain relief and physical protector, so it would take something cutting the wires open to short it, like a violent accident that smashes the trailer..

[John in Santa Cruz]

I poked around various threads mentioning the Victron Orion Tr DC-DC charger. My spid-EE senses are tingling a little

if my LFP batteries are discharged enough, they will suck down as much amperage as the charger can provide. If I use a Victron 12/12-18, and my truck can't provide 18ish amps at its trailer jack, will it throttle the output current, or will it try and drag the truck voltage down as low as it can in the hope it can get as much as it wants ? I guess the truck's hitch wiring will determine how much current it can get, I remember that my Tacoma + Casita, if I ran the fridge on DC while driving, it would suck down the Casita battery as the truck was outputting below 12.6V at that amp load, yet in the engine compartment, everything was a happy 14.2V

Does anyone know offhand where on a 2014 E21 classic, the breakaway switch is tied to the trailer 12VDC ? I know that I should put that on the trailer battery side of any DC-DC converter, and that if its spliced up near the hitch somewhere, there will only be one wire back at the power center for truck + breakaway. I guess I could mount the Orion in front, under the bed, so I don't need to run a new wire for the breakaway switch all the way forward from the back of the U dinette where the power center is.

[BobG]

John, I don't know where the 7-pin splice box is located on the 2014 21 but on the 2021 21NE it is on the frame near the tongue jack.


When I looked at your wiring diagram one thing that caught my attention was the location where the tow vehicle wire, 7th pin? 12V, connects to your trailer circuit between the battery switch and the fuse panel instead of to the battery side of the battery switch. I think the emergency brakes are supposed to be on an circuit that can not be interrupted by a switch.


You probably know the following but I will mention it anyway. The power tongue jack (if you have one) and emergency brakes are probably connected to the 7th pin in your 7-pin splice box so if you are installing a DC-DC converter then it would need to be on the tow vehicle side of the 7th pin so that the emergency brake and jack would work when the trailer is disconnected from the tow vehicle. How this is done will depend on your trailer's wiring.

[John in Santa Cruz]

Originally Posted by BobG

John, I don't know where the 7-pin splice box is located on the 2014 21 but on the 2021 21NE it is on the frame near the tongue jack.

k, yeah, i kinda figured it was eitehr out there, or just inside the front. my trailer has the foam underspray insulation so any wires under the floor are invisible.

Originally Posted by BobG

When I looked at your wiring diagram one thing that caught my attention was the location where the tow vehicle wire, 7th pin? 12V, connects to your trailer circuit between the battery switch and the fuse panel instead of to the battery side of the battery switch. I think the emergency brakes are supposed to be on an circuit that can not be interrupted by a switch.

good point. I will ensure the breakaway switch is powered directly off my 'big red terminal strip rather than the power center, even if it means running another wire over where I can connect to it. When my latest orders come in, I will have AWG 4,6,8, 10, and 12 wire available. the 10 and 12 are marine /2, while the 4,6.8 stuff is separate red and black cables, all flexible fine wound copper cable.

and I have hex crimpers for big gauges, and shrink wrap etc. I think I know what I'm doing, I just want to be sure I have it all sorted out right before I commit because this is all new to me.

Originally Posted by BobG

You probably know the following but I will mention it anyway. The power tongue jack (if you have one) and emergency brakes are probably connected to the 7th pin in your 7-pin splice box so if you are installing a DC-DC converter then it would need to be on the tow vehicle side of the 7th pin so that the emergency brake and jack would work when the trailer is disconnected from the tow vehicle. How this is done will depend on your trailer's wiring.

ah, ok, I haven't even looked yet, hah. I'm familiar with those splice boxes, so if it has one of those up front,bingo easy. i'll put the DC-DC charger in the front of the trailer, under the front corner of the bed, and use the existing tow charge wire that comes from the main power center to carry the brake voltage AND the dc-dc output back, and run short new wire from the DC-DC input to the 7-pin box.....

I did just commit to ordering the Orion-Tr Smart 12/12-18 as ~200 watts is all the charge I want to suck out of a tow vehicle, a 12/12-30 (360 watts) would be greedy. So the only thing that will 'fast' charge my battery if its deep will be 120VAC, with 50A of charge, about 700 watts, which will take maybe 7-8 hours to fully recharge a deeply discharged battery.

after I get the 360W LG panel installed on the roof, I'm thinking an external DC power connector that I can use to connect portable panel(s) on a cable in the sun to boost things. even 20-30 feet of cable could mean the difference between a few hours of good sun and none if you're parked under trees. and a pair of 180W panels hinges, paralleled, and with their own MPPT controller, could way more than double the roof panel ....

[John in Santa Cruz]

ok, looks like the 7 blade cable goes up into the front of the trailer, and there's a utility style junction box where it joins a bunch of wires from the rear just inside the front wall, under the bed, and next to the black tank. Not going to be fun to get in there unless I remove a plywood panel under the mattress, but I should be able to install the DC-DC right there, wire the truck cable to its input, and the existing wire that goes to the power center to its output, along with the breakaway switch power.

now, I guess that breakaway switch + truck power should be wired to the battery side of the battery cutoff switch? so even if the batteries are switched off, they are still charging from the tow vehicle AND they are still powering the breakaway switch.

[BobG]

John, yes, I think that the tow vehicle charging and emergency brake switch, should be wired on the battery side of the battery switch along with the solar. One thing I experienced is that a friend with a relatively new Toyota Highlander burned a 30 amp fuse when connecting her trailer to the car. When she started the car the discharged trailer batteries pulled too many amps from the tow car and the 12V circuit fuse burned. Her tow package was an after market install by a trailer hitch company. It seems better to have a DC-DC converter like you plan to do for control of the amount of current pulled from the tow vehicle.

[dstreight]

Although I personally haven't used an Orion...there is considerable chatter on the web about how hot it can get. Forced air circulation (12v computer type fan) and not installing it in a small, enclosed space...help mitigate the heat build-up. Just an FYI/FWIW.

[John in Santa Cruz]

so 360 watt solar, could be as high as 30A charging... for the foot or so long wires from the MPPT to the main + and - terminal strips, should I use AWG 6 or 8? I have both on hand, welding style cable with extra fine stranding. 6 is the biggest that will fit in the MPPT's wire clamps.

[BobG]

8 AWG would be fine for circuit from the MPPT to the busbars. According to BlueSeas it results in less than 1% voltage drop. The panels will very seldom if ever put out 30 amps laying flat.