22 replies to this topic

[JWL]

I am still in the planning phase while waiting for my Hawk shell and am now trying to figure out the solar and all that I need for that, so this topic does interest me as well. But from what I just saw the other day are the two wires from the solar connectors the one on the roof and the other on the side of the camper?

 

[Vic Harder]

JWL, is your camper of the same era as that video?  FWC wiring has been changing over the years.  

 

What is your end goal?

[JWL]

Well Vic I guess I didn’t catch the date on that video when I saw it. And since my Hawk has yet to be delivered I’m hoping it’s going to be a 2020, if not we are all in trouble!
My goal is to take this time and put all the pieces together, solar panels, charge controller, battery monitor etc. so that when it does come I can get on it. And as far as this wiring stuff goes just so I can have it straight in my head.

So how has the wiring changed? Not to step on the OP but maybe that could help him as well.

Thanks!

[Vic Harder]

My feeling is that if you are going to do solar on an brand new camper, it is best to do it right.  That said, my right may not be yours!  There are a bunch of factors to consider, including:

1) Where do you mostly camp?

2) How long do you stay in one spot?

3) How much power draw will you have?

4) What's your budget?  Both dollars and space wise.  Lots of solar/batteries consumes space too.

 

Let's start with that list.  Take a look at the link in my sig for the "more power scotty" thread.  Lots of deliberations in there.  

[JWL]

My feeling is that if you are going to do solar on an brand new camper, it is best to do it right.  That said, my right may not be yours!  There are a bunch of factors to consider, including:

1) Where do you mostly camp?

2) How long do you stay in one spot?

3) How much power draw will you have?

4) What's your budget?  Both dollars and space wise.  Lots of solar/batteries consumes space too.

 

Let's start with that list.  Take a look at the link in my sig for the "more power scotty" thread.  Lots of deliberations in there.  

Thanks again Vic. 
short answer is; Simple, keeping it as light as possible, don’t stay in one place more than a day or two. But I am planning on the future so I don’t have to do it all over again, but the sky is not the limit, so best bang for the buck. (That’s the hard part) 

And trust me I have been perusing your threads. Thank you for doing all that! 

[Vic Harder]

JWL - Well, my current build (#3 for me) might be overkill for some, not enough for others.  Try it on for size!  Considerations:

 

1) We camp all over the west.  Sometimes in big treed areas with lots of shade/rain, sometimes in the desert

2) We tend to drive to trail heads daily, usually about 30 -60 minutes a day.  So one hour of charging from the truck

3) When parked at a trail head, we tend to park so the sun hits the solar panel

4) Solar & driving should be able to recharge a 50% battery state in a day in order to keep us going indefinetly

5) Most we stay in one spot with no charging is 2-3 days

6) We need to be able to monitor battery state so we don't get surprised and run out of juice

7) Match battery capacity to daily draw

8) Worst case, match battery draw to water draw.  If we run out of water we have to drive to get more

9) Mountains/trees are worst for solar, as water is usually plentiful, sunshine isn't

10) Longest we've boondocked is 10 days in a row.  More of that coming

11) We can get away with sponge baths.  Typical water usage is a gallon each per day for water, washing, cooking, etc

12) Most battery draw used to be the fridge.  Typically 20-40AH a day depending on outside temps

13) We are now adding an induction cooktop.  That uses 160A when on high.  Yikes.  But, we will monitor typical usage this year (?) to see what that's like.  We added another 100AH BattleBorn battery to run/cope with the high demand

14) I am limiting battery charging from my alternator using a DC-DC charger.  Limit is 40A.  This protects my alternator from burning out, since the dual BattleBorn batteries could stomach 200A of charging for far too long.

 

So with all that background, I can start to figure out what I need.

 

A) Item #4 tells me I can tolerate using half of my battery capacity in a day.  That's 90AH in my case.  200AH of LiFePo4 that I am willing to take to 10% so 200 - (200*10) = 200 -20 = 180AH of capacity.  180* 50% = 90AH.  If I go two days without charging, I am at my limit of 10% left.

 

We still need to monitor that so I can tell if this realistic and matches my projections, so #6 means I need a real battery monitor.  Victron BMW 712 comes to mind.  Cheap Chinese knockoff may work, as does the Trimetric.  Volt/Amp meter is not enough.

 

C) To recharge 90AH in a day, I need about 2x as many Watts of solar as AH drawn.  So, 180AH at least.  That's in ideal conditions. Figure 60% of that as more realistic on most days. So, 180AH * 140% =  252AH.  If using the 160AH panels that FWC is using these days, I would want two of them.  I chose a great household panel (not fond of the flexibile panels designed for sailboat biminis, as these overheat and fail fast when glued down to a solid surface) that is rated at 330W.  Literally the biggest I could find at the time that would fit on my roof.  A little bit of overkill.  Today I could get a 440W panel that would fit, and I would.

 

D) What if I can only charge by driving, because of shade/rain/snow?  I limit my charging to 40A with my Renogy DC-DC charger.  If I took that out, I could through 90A (most I have observed on my in-cab Blue Sea Ammeter) for a short while.... dunno how long it would take before smoke started coming out of my alternator.  Not something I want to discover while 100 miles from nowhere.  90A/40 = 2 hours and 15 minutes of driving to recharge my 50% batteries.  And that's a best case with LiFePo4 batteries.  AGM and other lead acid batteries will resist charging as they fill up, so it will take way longer.

 

Driving while charging also means having big enough wires to carry the current your alternator can push out.  Call it 50A.  Using this table - LINK - I would pick 4 AWG which is rated at 60 Amps.  That is MUCH bigger than the stock wiring harness that FWC and other RV companies use... 14 AWG worst case for your typical 4 conductor trailer harness, 10AWG if you are lucky.  10 AWG is rated at 15A.

 

Driving while charging also means a DC-DC charger like the Renogy, RedArc or some other cheap voltage booster (rando linked to a good setup here).  

 

If your alternator isn't "Smart" and your batteries are lead acid AGM or flooded, you can just use fat wires and a good battery separator like the Blue Sea 76xx series.  

 

Situation #9 (and others) above mean I want a good solar controller that can make the best use of my solar panels.  I may want to add portable panels to position them in the sun while the camper is in the shade.  I like Victron MPPT controllers.  I chose a 100/30 model for this setup as it give me some expansion room (up to 440W).  The table towards the bottom of this www page gives you sizing recommendations.  With my setup, if I wanted to add portable, I could add about 160W and not typically exceed the limit of the charger... but could.  I made the mistake of undersizing my controller on my Hawk build.  If adding 100W or more of portable,  I would add probably add another Victron controller to the mix.

 

Summary:

 

a) You need to monitor your draw = Victron or other BMV

You need to know how much you can recharge on a given day - that's solar and alternator capacity

c) You need enough battery to so that they don't get discharged too much between charges.  AGM = 50%, LiFePo4 = 5-10% SOC

d) You will need enough solar to recharge with.  Figure at least 2x the AH used.  160AH is a good size for the typical 75AH batteries installed in our campers from the factory

e) You will want a good solar controller that has expansion room, or get two

f) You may want a good ACR like the Blue Sea 7622 and/or a DC-DC charger or a combo unit (Victron makes one now)

 

The latest I hear is about more combo units.  They are not the best in all conditions, but are super simple.  Stuff like the CTEK, RedArc or Victron that combine several features.

 

I hope that helps.

[JWL]

All good stuff Vic, thanks.

so in C above you stated that you would put more on the roof? I was thinking of going maybe 100 (or so) on the roof just for charging while driving and if parked in a sunny spot. Then going with more in a portable for parking in the shade. Plus from what I understand is the roof mounts are the least efficient due to the lack of being able to angle them toward the sun. Thoughts?

 

My biggest draw will be the Fantastic Fan(s) or the heater. We pretty much have the cooler thing down from dirt bagging it in the topper of my truck (up to 5 days so far) so I’m not planning on getting a fridge but I know I will at some point so I want to get a controller now that will handle that need. I was thinking about seeing how I fair with the one AGM battery that comes with the Hawk for a bit but rather than buy a second AGM was wondering about going with a single Lithium battery. Are there any concerns or reasons not to go this route? 

[Vic Harder]

single lithium is great idea if you have no other batteries yet.  If the camper is coming with an IOTA on board charger, you will want the lithium chip for it.

 

Just fan and furnace is low draw, probably less than 20AH a day.   The standard 75AH AGM can handle that for a few days.

 

You were thinking portable.   I gather you camp in warm places?   Portables are great for maximizing the angle of the sun and finding a sunny spot while you chill in the shade, but...

1) You have to be there to move the panels as the sun and shadows move during the day

2) The potential loss of panels due to theft (and WIND) becomes an concern.

 

On the roof is "install it and forget it".   You will want heavier capacity shocks too.  I have 80# shocks on mine roof.  Fine with the panel on in, and as I found out now during roof/ceiling repair on mine, impossible to lower with no heavy load on top.

 

I imagine the first thing to do is get a battery monitor and use that to see if you even need solar, given your low draw.

[RHarries]

Thanks all for input and guidance.  I took Ed's advice (and a few beers) and found that the box affixed to the underside of my 87 watt Kyocera PV panel is only a junction box used for setting up differing PV array configurations.  After a few more beers (and advice from FWC), I was able to locate the Sunsaver 6 charge controller in the front driver's side cabinet near the electrical disconnect.  Access to this requires removal of a couple cabinet panels.

 

Also, as suspected, one set of wires entering the battery cabinet is from the solar controller, and the other is from the IOTA load center.

 

I did take the forum's advice and acquired a Victron BVM 712, and am now starting to appreciate its value, although I haven't fully learned its functionality.

 

I have been living off-grid for the majority of this "panic-demic" and found that my 100 AH AGM battery and 87 watt PV panel is sufficient for MY electrical demands (water pump, furnace fan, Fantastic Fan, Stereo, dual USB charging ports).  Weather has been partly cloudy here in SW Colorado, and the battery is fully recharged each day without starting the truck for alternator charging.

 

I have a Norcold 3-way fridge that I run on propane only (due to power demand), and get 2+ weeks of cold food, beer, and ice in a single 20 pound tank.  IMO, the propane fridge is a great solution for my needs.  I do cycle the Hot water tank off during warm periods as i sense it uses quite a bit more fuel than the fridge.

 

Ride on and on and on and ...

[RHarries]

After a bit of monitoring the BMV, I am still a little confused how the system is supposed to function.

 

The solar controller that i have is a SunSaver 6 which has the following setpoints for a sealed battery)

• Low Voltage Disconnect  (LVD)= 11.5 Volts
• LVD reconnect = 12.6 Volts
• constant voltage regulation = 14.1 Volts.

As I understand this: the controller will connect the PV panel input to the battery only if the battery voltage drops at or below 12.6 Volts and would apply up to 14.1 Volts to re-charge the battery.  I am unclear what the LVD 11.5 V setpoint is used for (?) 

 

In reviewing the Victron Battery monitor 712, I have been surprised that there never appears to be a positive current flow (only negative)  even during full sun exposure. Perhaps this is because the battery voltage has remained at over 12.6 volts.

 

I started wondering if either the controller or panel were broken.  I have been taking voltage readings at the solar and battery terminals on the charger.  The solar voltage reading has always been near to the open circuit voltage (Voc) of 22 Volts and the battery voltage is reading correctly.

 

It seems odd that the panel could be broken if the Voc is at its specification.  I do not know how to test  what current the the panel is producing.

 

I plan to discharge the battery down to below 12.6 Volts and then see if the controller switches to charging at near the battery voltage reading.

 

Any thoughts/advice on how to diagnose problems would be appreciated.

Edited by RHarries, 29 April 2020 - 10:51 PM.