Questions regarding "So, you want to setup a good electrical system in your camper?"

[Vic Harder]

Good info Vic and you are a talented writer! Looking forward to the rest. You should be a technical writer!

Steve

I've done some of that Steve...

 

[Tom S]

Hi everyone.
I’m new to the forum and new campers as well but I’ve got a fair bit of experience with boat wiring. Firstly a big thanks to Vic and all the other contributors for their work as well as thoughtful and honest discussion. I’m going to upgrade the charging system of my truck and camper. I don’t see any sense in reinventing the wheel here so I’m following Vic’s recommendations pretty much to the letter. I’m aiming for adequate rather than ideal in this build so I might substitute fuses for circuit breakers etc. I’m planning on sticking with the agm battery for now and am installing a Renogy DC DC charger with MMPT and a Renogy monitor with shunt. I don’t have solar now but have got the MMPT with an eye on adding that in the future. I have a couple of questions:

First what size of Anderson connectors are you using? I’m using #2 awg wire I have had sitting around for ever. I was thinking the Sb 120 amp ones but I’m wondering if these are too big? They are rated at 120 amps but at what voltage? Would the 50 amp ones work here because the voltage is so low?

Secondly does anyone have a clean way of mounting the connector in the truck box? I see there are some flush mount kits for the smaller ones that are mentioned in the Australian sites but nothing for the larger ones that I’ve seen so far. (Full disclosure I haven’t looked as hard as I could!)

And lastly could someone please explain the reason for a circuit breaker or fuse at both the truck end and the camper end of the positive supply wire? It seems like when the camper is connected their are two breakers protecting the same wire. Are they there to protect the wires in the case of a short when the truck and camper are disconnected? That's probably it but I feel like I’m missing something here. Don’t even mention age!!!

Cheers and thanks again.

Tom

 

[PaulT]

Hi everyone.
I’m new to the forum and new campers as well but I’ve got a fair bit of experience with boat wiring. Firstly a big thanks to Vic and all the other contributors for their work as well as thoughtful and honest discussion. I’m going to upgrade the charging system of my truck and camper. I don’t see any sense in reinventing the wheel here so I’m following Vic’s recommendations pretty much to the letter. I’m aiming for adequate rather than ideal in this build so I might substitute fuses for circuit breakers etc. I’m planning on sticking with the agm battery for now and am installing a Renogy DC DC charger with MMPT and a Renogy monitor with shunt. I don’t have solar now but have got the MMPT with an eye on adding that in the future. I have a couple of questions:

First what size of Anderson connectors are you using? I’m using #2 awg wire I have had sitting around for ever. I was thinking the Sb 120 amp ones but I’m wondering if these are too big? They are rated at 120 amps but at what voltage? Would the 50 amp ones work here because the voltage is so low?

Secondly does anyone have a clean way of mounting the connector in the truck box? I see there are some flush mount kits for the smaller ones that are mentioned in the Australian sites but nothing for the larger ones that I’ve seen so far. (Full disclosure I haven’t looked as hard as I could!)

And lastly could someone please explain the reason for a circuit breaker or fuse at both the truck end and the camper end of the positive supply wire? It seems like when the camper is connected their are two breakers protecting the same wire. Are they there to protect the wires in the case of a short when the truck and camper are disconnected? That's probably it but I feel like I’m missing something here. Don’t even mention age!!!

Cheers and thanks again.

Tom

The reason for a circuit breaker or fuse at each end is to protect the wire and vehicle in the case there is a short to ground anywhere in the wire because there is a battery at each end of the wire, Think of the case where the camper is off the truck If the wire from either battery to the connector is shorted, there is sufficient energy to cause a fire in the camper or in the truck.

For the case where the units are connected together, a short anywhere will be energized from both ends until the fuse/CB breaks the connection from the battery with the fuse/CB However, there is still a path from the other battery without a fuse/CB.

Paul

 

[Vic Harder]

First what size of Anderson connectors are you using? I’m using #2 awg wire I have had sitting around for ever. I was thinking the Sb 120 amp ones but I’m wondering if these are too big? They are rated at 120 amps but at what voltage? Would the 50 amp ones work here because the voltage is so low?

Cheers and thanks again.

Tom

Hey Tom. I'd just go by the wire size. Their website allows you to filter the results by amps or wire size
Anderson Powerpole and SB Connectors | Powerwerx

 

[Tom S]

Thank you Paul and Vic. That makes sense now with the breakers. Yes two batteries with ample opportunities to raise havoc. I’ll check the Anderson site this evening. I’m just making a small electrical panel out of laminated arborite that will house the water pump panel, new USB chargers, energy monitor and the thermostat for the heater. I’m hoping this will allow me to significantly enlarge the tiny drawer that’s up there. And the panel is going to be easily removable so you can get at all the wiring!

 

[Jon R]

Regarding connector sizing, what matters is the current rating of the connector and whether it will accept and provide a solid mechanical and electrical connection with the wire you are using. Any of these connectors are rated for much higher voltage than any RV DC system is using. An SB 120 is rated for 130 amp and wire size ranging from 10 AWG to 1AWG. An SB50 (next size down) is probably large enough for your truck charging connection from a current rating standpoint (not sure what DC-DC charger you are usng), but it accepts a maximum wire size of 6 AWG, so too small for your planned 2 AWG.

 

[Tom S]

Thanks Jon. I ordered the SB 120 connectors. They fit the #2 wire. Both the wire and the connectors are going to be ridiculously oversized for the installation as it is now but seeing as the wire was already here it seemed like an easy choice. If I do decide to upgrade to the lithium batteries in the future or even a larger Agm setup then the wiring will already be in place to handle it. I went with the 30 amp DC DC charger as I thought it to be correctly sized for the 100 ah Agm battery. It remains to be seen how much and how we use the camper as to what the rest of the electrical system will need to be. And that’s going to be the fun part!! Not crawling around on your hands and knees with a headlamp trying to turn your arm around three 90 degree corners to put in another mounting cable tie. Lol

 

[ntsqd]

We use SB120's at work with a right angle bracket that places the open end of one flush to the panel it is mounted on. I think that they found that bracket on the powerwerx page, but I don't know that for sure. In our truck's bed I merely bolted it flat to the bedside pointing up. I pointed it up deliberately so that water & moisture would drain thru the connection uninhibited.

Going back to the weight of the batteries, an example of the importance of this. Our Chucara XL has the 2x 2GC's in a box on the side of the camper, aft of the truck's RR tail light. The camper does not normally come off the truck.

I now need to replace the rear springs as they are slowly collapsing and losing ride height. The weight is an issue for sure, but the placement of that weight makes it an even bigger issue. I'm considering moving them to under the step that is adjacent to the forward dinette seat. Enclosing and venting them there will take some thinking, but at least then they will be inside the wheel base of the truck instead of hanging off the rear of it.

 

[ntsqd]

Found a pic, not that it should need it, but why not?

EDIT: Just in case there's any confusion, that is NOT house wire. It is Ancor Duplex 6 ga.
https://www.ancorproducts.com/en/120710

 

[Tom S]

Hey thanks for that. I’m going to do a very similar installation in my truck. I’m still waiting for the Anderson connectors to show up but most of the hard work has been done inside the camper. The DC DC charger, shunt, and fuse block are all mounted as is the new battery box and the 125 ah AGM battery. I had to do a bit of cutting of the aluminium angle so that the new battery could drop straight in but it fits in there great. Just the actual wiring now. It does look like house wire but that tinned copper boat wire is nice stuff. Use that with heat shrink connectors and Boeshield T-9 or ACF-50 on the terminal blocks and that’s as good as it gets!!

 

[ntsqd]

The contacts are silver plated, under a fair amount of contact force, and experience significant wiping during mate and de-mate. Use care with the heat shrink, easy to get it where it won't allow the contact to engage the connector body correctly or move like it should.

 

[Tom S]

Hi everyone. So the Anderson connectors finally showed up and both the truck and camper are now fully wired.. This is what I finally ended up with:

#2 awg wire from truck to camper via 120 amp Anderson’s in the truck box.
Blue sea 50 amp breaker under the hood.
Renogy 30 amp DC to DC charger with MPPT.
#4 awg wire from charger to battery..
Blue Sea 40 amp fuse block between camper battery and DC to DC charger.
Renogy 500 ah monitor with shunt in the camper battery negative.
Stark Energy 125 amp hour AGM battery.
Pre wired for solar with a 50 amp Anderson clone (Pico) located outside on the drivers side.
Just bought 2 Renogy 100 watt solar panels.

I’m super happy with how it turned out. I could have got away with a bit smaller wire size between the dc dc charger and the camper battery but I went bigger in case I upgrade to lithium some time in the future and increase the size of the dc dc charger. Right now I’m building a folding storage box to carry the solar panels. We carry a canoe on the roof so the panels will be on the ground. My question is this. (And I probably already know the answer and don’t want to admit it to myself.) The negative terminal on my truck battery is an odd affair that the big #2 wire wouldn’t attach to easily. So I attached the the wire to the frame ground about three inches away. Toyota has a jumper between here and the battery negative but it is only I’m guessing something like a #6 wire. This bugs me. Should I upgrade this? It seems like a weak link in a pretty good system. I have two options. Put a second smaller wire between the ground and the negative terminal or cut off the terminal and replace it with one with a stud that accepts the bigger lugs. On the Toyota terminal the negative wire is crimped directly to the terminal body. I’m pretty sure I know where this is going. lol. You’re never really finished are you?
Thanks again for the help.

 

[rando]

A few centimeters of #6 AWG wire is no issue at all, your wire is already oversized for the job, and you don't care about voltage drop anyway as you have a DC-DC charger.

This is not at all a problem in your system as your wire is all more than sufficient, but in general it is more important that the wires between the DC-DC charger and the battery are fat (and short), as opposed to the wires between the truck and the DC-DC charger. The charger will compensate for voltage drop on the wires to the truck, but not between the charger and battery.

 

[Wallowa]

Brian G.,

My recent saga is on the forum but my 2x75 amp AGMs ['16 Hawk] faded on me during cold temps with very minor load.

Ironically I also have an appointment with SixGun for about what you are doing: 100Ah BB LiFePo4; DC 2 DC; Victron 110/30 Controller [replacing Zamp Controller]; re-wiring my 170 & 160 W Zamps from parallel to series * ; new roof connector. I already have a Victron 712 w/temp. My appointment is June 4th, 0900-1600hrs. They rewire and install.

Brian when are you having your work done?

* Question: I have read the differences in putting solar panels in parallel vs series. Does anyone have first hand experience with the functional difference in terms of battery charging and SOC maintenance?

Thanks...Phil

 

[Machinebuilder]

* Question: I have read the differences in putting solar panels in parallel vs series. Does anyone have first hand experience with the functional difference in terms of battery charging and SOC maintenance?



When I added a second panel I wired them in series.

My reasoning is when you look at the Victron manual the voltage from the panels needs to XX volts over the Battery voltage to start charging. When you put them in series it hits the voltage difference in much lower light, ie earlier am or on a cloudy day.
I don't have the exact voltage in my memory or available right now.

I have not tested this completely as part of the reason for me to upgrade is I killed my AGM battery by over discharging it.
I have a 100AH Battleborn LifePO coming this week.

 

[Wallowa]

hanks MachineBuilder,

My ignorance again...I thought the voltage even during shading did not vary, or did not change much, just the amps delivered did...my concept was that higher voltage could more effectively 'push' amps and develop watts..as I remember my panels are about 19volts each...and around 9.4 amps each ...at best. I looked at the Vic Controller and it recommended 5V over battery voltage...17V?

Wish all this would pop in place and make sense to me....still feeling like I am basically clueless! Even claims that MPPT can deliver 30% more power than a PWM gets lost with me...hype or real difference...

Phil

 

[Jack]

The short answer: if your panels are the same type/brand (or same wattage and very similar Vmax), connect in series up to what your MPPT controller can handle. I have four 100W 19Vmax panels - 76V - on my 100/30 Vic, which can handle up to 100V input. Some controllers are limited to 30V or 50V.

Your panel voltage will vary by about 2V to 4V depending on how much sun and how much current you are asking the panel to supply.

The higher voltage from two panels in series does not pull more current out of the panels - but the higher voltage (38V instead of 19V - it varies by a few volts) means that the voltage is always more than 5V above your battery voltage and the MPPT controller will always be adjusting the voltage (up and down) to get the most watts (current X voltage). The MPPT controller actually sets the output voltage of the panels to get the maximum watts.

You can see this with your AGM batteries. Charged and with almost no load, they should be about 12.6V. Now add load by turning on the overhead fan and the furnace (about 7A) and watch the battery voltage drop. The amount of current drawn out of the batteries changes the battery voltage. The MPPT, by controlling the current drawn out of the panels changes the panel voltage. What's different about solar panels is that the change is non linear. Lets say, for the same amount of sun, your two panels in series are producing 40V at 5A. That's 200W charging your battery at 14V X 14.29A. (The MPPT takes in whatever voltage and current the panels supply and outputs what is needed for the battery.) But if the MPPT finds (generally by trial and error with small changes) that if it lets 5.4A flow from your panel, the panel voltage will drop to 39V. 39V X 5.4A is 210.6W. Your MPPT just got you an additional 10.6W so your battery will now charge a bit faster at 14V and 15.04A. As the amount of energy from the sun coming into your panels changes, this sweet spot changes. Your MPPT is always hunting for it when the panel voltage is 5V more than what is needed to charge the battery or meet your load.

 

[Vic Harder]

Nice explanation Jack.

In comparison, a PWM controller can't do the fancy juggling of varying power and current to maximize the power output. All it can do is reduce the voltage if it is too high. So, 20V in at 5A = 100W, but the battery only needs 13V, so it cuts the voltage down to 13V. That 100W panel is now only producing 13*5 = 65W. Oops. In the same scenario, the MPPT is still getting 100W out of the panel.

 

[BrianG]

Wallowa, my appt is April 19.

 

[A.Smith]

How are you guys getting #4 wire into an Orion-Tr Smart 12/12-30 Dc/Dc charger ?
Try as I might, a number of strands are not making it into the opening.
#6 fits fine, but..

I am going to run #4 from the truck battery to the Anderson Connector, but what gauge from the Connector to the charger and what gauge from the charger to the battery ?
Charger will be close to the BB LiFePO4, but wire garage is important, so do I worry about a few strands of #4, or use #6 ?

Thanks,
Fred
A.Smith