Need help planning for Solar and DC to DC

[Glenn]

Wow! So I really hate making a post this long but need the reader to know where I’m beginning, Some of this may be wrong. I have been researching and trying to get up to speed the best I can. I’ve done automotive and household electric- my late Father was a journeyman electrician and spent most of my growing up years holding a flashlight


So just recently joined WTW and am hoping I can ask for some experienced help. I started a “New Build” thread for my truck and topper, but have no experience in “house batteries”, DC to DC, or Solar as I’ve always tent camped in the past

I know this is a little (a lot) long so bear with me please..

I was looking at Renogy sites, and had a customer service person recommend their 50A DC to DC w/MPPT. But after reading forums there were a lot of folks who said it was better to separate the two into separate systems into a DC to DC and a PWM Solar charge controller that didn’t see each other.

Part of the reasoning as I recall was on a cloudy day with minimal solar input, it keeps the DC to DC from charging its full charging amperage as Renogy’s system is a 50/50 split.

I do have a 7.3PSD with a 110A alternator and it uses a Glow Plug Regulator and provides high amperage to the glow plugs for the first few minutes, before and after starting. and drops the voltage significantly , which was intended by FORD to protect the glow plugs from high voltage.

My plan is to use a 60A normally closed relay that will power the DC to DC charger, and using a (+) wire from the GPR to activate the coil, opening the circuit to the DC charger. Then when the glow plug relay shuts off, power is no longer supplied to the coil of the relay / DC to DC charger relay and it will close the circuit again allowing it to do its thing depending on the state of charge in my 280 AH Lithium LiFePo4 battery (that I have already purchased.) I mocked up a board of the batteries dimensions to make sure it would fit.

Mu truck (2002 F350) has two starting batteries, and after the initial voltage drop of the glow plugs and starter motor, the voltage quickly comes back to 13.7 to 14. Volts with no heavy loads being pulled.

Q. If I’m on the right track that leads me to which brand dc to dc charger and how how many amp charger to get, 20, 30, 40 ?

Then for solar panels on my topper roof I am currently looking at these:

Rich Solar MEGA 100 Watt Slim Monocrystalline Solar Panel

Buy premium quality Rich Solar Mega 100 Slim Solar Panel RS-M100SL for only $129.99 at Off Grid Stores. Free Shipping!

offgridstores.com

They would fit nicely, staggering the raised rib down the middle of the topper roof. My plan would be to use aluminum T track and 3M 5200 marine adhesive to secure them to the roof, and an end cap on the front to stop air lift from underneath.

Q. Am I right to believe fixed panels are much better than flexable? I know recent improvements have been made on the flex panels.

I am open to suggestions, The dimensions of the above panels are my limit on size. I will be running two panels.. I also need advice on which PWM charge controller?

Q. I was thinking I would run the two panels in Parallel, keeping the voltage the same. Is this best for the occasional 3 to 5 day trips in planning or would wiring in Series be better?

I know my dc to dc charger needs to be close to the house battery. I have a good understanding of electrical and know how to size the appropriate wire given amperage load, fuse selection, length of run, and voltage drop.

All of my Electical hardware is going into the cabinet on the Left side of the truck bed and I am cutting holes and adding vents for ventilation, along with a heating pad for the battery in extremely cold temps.

Thank you so much for taking the time to read and for advice to set me in the right direction. It is much appreciated

Glenn

 

[Glenn]

Never mind, I found the edit button

 

[Wandering Sagebrush]

Never mind, I found the edit button

My understanding is the “Edit Button” will disappear 24 hours after the comment is posted. Following that, it takes intervention by the Site Team to give the more time to edit.

 

[Glenn]

Thank you Steve…… yeah I found the edit button after poking around. I do everything from my smart phone. A few differences, but similar to the other forums I belong to.
Thanks

 

[Jon R]

It looks like your project is power for camping in a truck cap. We need to know a bit more before we start telling you how to spend your money.

What are the loads you want to be able to supply (fridge, fans, lights, etc)?

How long do you want to be able to camp with no solar and without starting your truck?

How many hours of driving would you like it to take to recharge a day’s worth of battery energy?

Comment: in addition to the engine running detection logic settings, the Victron dc to dc chargers have a setting for delay time after engine start before the charger comes on. That setting is intended to provide a simple built in way of dealing with initial truck battery recovery or other brief high loads after engine start. That would save you trying to invent such a feature yourself .

 

[Jon R]

For most camper users, I imagine there are occasionally trips where you really need your solar to work (you want to sit several days or more in one sunny spot) or you really need your truck charging to work (winter overcast camping or forest camping for several days or more). That’s why many of us install both solar and truck charging capability. However, I suspect most trips people take will not be interrupted or ruined as long as either one of those charging sources works. For those trips, having both charging capabilities provides meaningful redundancy.

When you have redundancy and want to achieve the greatest chance of retaining adequate capability after a failure, you want to provide isolation of your redundant features to the greatest extent practical so that you don’t have a single failure or a common cause take out both features.

Based on this principle, personally I am not in favor of the all-in-one charging devices offered by Renogy, Redarc, and others. Just from a system architecture standpoint and charging function reliability standpoint, I think there is value in using separate solar and truck charging equipment to reduce the chance that a single failure takes out both charging capabilities. Most trips I take i could function just fine on either charging source alone and would be able to continue my trip as planned after one failed.

This plus the high level of user control of the charging parameters is why I really like having separate Victron chargers.

 

[Glenn]

Jon R,

thank you for the reply. As far as camping, yes it will be in my topper. Originally I had plans to get a slide in truck camper. I had been working on my Dually since 2018 (for retirement). Then in 2022 I had two strokes, very debilitating. I pushed hard, and in 6 months returned to a very physically demanding job.

I continue to get better, but I won’t be making the travels I (and my wife) had hoped to if purchasing a 5th wheel.
But we will travel by other modes for places we want to see.

My wife doesn’t really care to camp or fish so this is a get away for me, nothing fancy or complicated. I’m envious of the rigs many of you pull and live out of,

I have been doing 3 to 4 day fishing trips to state parks with my 18’ bass boat / 150 hp Merc. Running trot lines, climbing into deer stands, It’s driving my wife nuts but she knows there’s no holding me back.

So my travels will be mixed, around the state (Illinois) with club functions, to our family farm (3 hour drive) and a friends farm near Shawnee National Forest (also 3 hours away) with no electric or water at either as I don’t want to impose.

Hopefully a 20 hour drive to my friends property near Mancos Colorado. I have an open hunting invitation (have been there before) but not sure I’m up for that.

And a trip to Texas hunting wild pigs with my club and our longbows (been before) No electric.

In 2009 I did a 8 day wilderness Elk trip at 11,000 ft in the Weninuchee Wilderness Area in Colorado, thank goodness! - because I think those days are long gone.

Some trips will have shore power at State Parks. But this isn’t for extended boondocking. I Hope that make sense


As to power draws let’s first discuss what I won’t have:

•No AC
•No conventional Furnace
•No electric skillets, etc. Will be Cooking on propane burner.

What I plan to have:

•4 light bars - 3 watts (each?)
•2 small USB 5V fans. 4 watts each
•Fillet knife. 100 to 150 watts
•Fresh water tank 41 watts
heat pad -35*F
with thermostat
•8’ heated cable for 26 watts
Lithium battery
below 35* F
•4.0 gpm 12V 96 watts
water punp
•Small 12V fridge/ 60 watts
freezer
•12V elec. blanket 35 to 50 watts
above 40*F
•12V supply to Watts unknown
Diesel Heater below
40*F
•CPAP machine with 25W / 75W peak
heat & humidifier
turned off

What I’m unsure of:

•12 volt TV limited use. watts ?
•Chullux single serve 800 watts
coffee maker

I realize many of these are not on very long based on amp hours while the CPAP will probably be the longest draw (8 hours)
and the 12V fridge / freezer until it gets to its set temperature and just maintaining

I will still very much be primitive camping of sorts with a Propane bottle for the outside shower, cooking, etc.

I also plan to have a 2000 W pure sine inverter for any item that doesn’t have a 12V supply. I did find a 12V adapter for my CPAP machine.

In most cases, I will drive my truck daily for short trips (1/2 hr to 1 hr.) once a day. For Solar about 3 days would be max. for not driving. If I needed to I could put the inverter on my starting batteries and switch to the high idle tune on the Diesel

Thank you for your guidance, I know it’s a tall ask.

Glenn

 

[Jon R]

First, I hope I didn’t come across as looking down on camping in a truck cap with a DIY setup. It’s what i would be doing if my wife didn’t insist on more amenities for the road trips we hope to take when I retire in a year. We’re only one or two steps up from a topper with our pop-up slide in camper. Camping out of the back of my 2004 Yukon XL with mostly backpacking gear was some of the most comfortable and convenient car camping I’ve done. A topper is about the same size as the back of a Yukon XL.

Traveling with a cap instead of a slide in camper gives you better mobility, visibility while driving, better gas mileage, stealth, maybe a lighter and softer riding truck (though i note you are outfitting a one-ton dually), ability to haul more toys on top and in the topper. Lots of pluses.

Second - I applaud and admire you for keeping going with the outdoor activities you enjoy after having those health issues. Building something like your camping setup is part of the fun for most of us.

With your already having a 280 ah lithium battery, with the loads you’ve described, and for stay lengths of 3 or 4 nights most of the time, I would consider just using that large battery capacity and a dc to dc charger, and not do solar at all if you are trying to minimize spending. That would have the bonus of no stuff on the roof to worry about.

Even with the CPAP machine at 2 plus amps continuously all night plus the fridge and other loads, i think your usage in a 24 hour period won’t exceed 50 amp hours. With that huge battery that’s 5 days of capacity without charging if you start the trip fully charged. If you install a 30 amp dc to dc charger, you would recover more than a day’s worth of energy in a two hours of running the truck. With a 50 amp charger you would recover a day’s worth in an hour of running. One of those configurations without solar might suit your needs and save you some money and complication. You would probably want a 20 to 30 amp charger for charging at home before trips, so it might be cost effective to just add a 30 amp shore power converter/charger, but if you can run your CPAP and fridge directly off of shore power when it’s available, you wouldn’t need a converter/charger when camping for long periods with shore power.

With a 30 amp dc to dc charger 6 awg wire from the truck battery to the camper battery is adequate. With a 50 amp controller you would run 4 awg minimum.

You can always add solar later. If you do add solar, you really want an MPPT controller/charger. Without getting into why, an MPPT will give you significantly better output from your solar panel because it allows the panel to operate at its optimum output at all times. PWM controllers are old technology that is less efficient.

You will see many here recommending a single large solar panel rather than multiple smaller panels. Those recommendations are mostly driven by trying to keep the roof weight down on manually lifted pop-up roofs, but even in a fixed roof simplicity is a plus. Try to go with one large panel or two identical smaller ones. I support the general recommendation you see here to have one large panel if you can find one that is the right size and power for you. I have two parallel wired 200 watt Renogy rigid panels on my camper.

You didn’t mention a battery monitor. I would highly suggest using the Victron smart shunt (only readable via your bluetooth smartphone) or the BMV-712 (dedicated display plus readable via phone). That will allow you to read your battery state of charge in percent, just like your phone battery.

This is a pretty long post at this point. I’ll stop and let you ask questions.

 

[Glenn]

Jon, thank you for the comments. No worries, I took nothing you said as condescending. Thank you for your time in looking over the loads, and advice to start with the DC to DC charger, leaving Solar as a possible future update. That makes sense.

While purchasing my battery I did order a 20A 115V charger as I had read that battery chargers for lead acid can shorten the life of the LiFePo4 batteries.

I looked at the Victron chargers and saw they came in isolated and non isolated. From googling it appears I want the non isolated as both the starter batteries and house battery will share a common ground.

The word “non isolated” through me because I thought isolated meant when the engine was turned off, the house battery couldn’t draw from the starter battery if the house battery was depleted.

I will run a dedicated ground wire from the Starter battery ground terminal to the DC to DC charger and not use the chassis/frame.

I’m leaning towards the Victron 50 amp charger. Should I ever need to replace or upgrade my stock alternator a very common Mod with the 99-03 SuperDuty 7.3 guys is to replace the stock small case 110A alternator with a large case (next generation) 135A 6.0 alternator.

It requires minimal work to fit it in and not enough concern of increased amperage to affect the glow plugs. I have already upgraded to a larger geared starter motor, larger cables, larger crossover cable (battery to battery) larger grounds. So all that would be left is upsize the cable from the 6.0 alternator to the battery. I’m good mechanically and am back to doing all my automotive work in my shop.

So, now that you’ve steered me in the right direction, if I later would add solar for extended trips where the truck sits (week long hog hunt in Texas) i’m thinking maybe solar panels set up outside the truck hooked up to MPPT controller would be an option.

Everything you said make good sense to me, so it’s on to the build

Many Thanks! Glenn

 

[Glenn]

Jon R,

Two things I forgot to add. I will include a battery monitor as you recommended.

And, I bought a Blue Sea fuse block with positive / negative buss bars and 12 fused circuits.

So I will run my cables (pos. fused) from the starter battery, to the truck bed with an Andersen style plug, to the dc to dc charger, and from there to the LiFePo4 battery. From this lithium battery to the Blue Sea fuse block with individuals loads ran and appropriate fuse sizes. Also will run from the lithium battery to the monitor.

So I’ll have a (+) & (-) input to the dc to dc charger. Will it also have a (+) & (-) output going to my Lithium battery. Is the non isolated charger the correct one?

Thanks!

 

[ckent323]

Looks like Jon R. covered most of your questions.

Be sure to install a fuse at each end of the vehicle battery to house battery connection (6 ga or 4 ga wire connection) and appropriately sized. I like the Blue Sea resettable series 285 breakers. I think 80A should be OK.

As Jon R wrote, you definitely want to use an MPPT controller as well as a battery monitor.
I hope this is helpful,

Craig

 

[Glenn]

Thank you Craig! After getting my head wrapped around this, and knowing the house battery will not be grounded to the chassis, I believe the isolated is the correct one. The lithium battery and blue sea fuse block will have its own grounds and positives coming from the house battery…..hang in there, I’ll get the idea you gotta give a welder a break I’m tired…. Today was day 12 of a big machine outage at work. the weekend is finally here.

 

[Jon R]

The non-isolated charger is what you want unless you have a specific reason you want to isolate the truck ground from the camper ground.

Isolated versus non-isolated refers to whether the grounds of the input and output sides of the charger are kept isolated or are connected. Others have said Victron makes the isolated chargers primarily for marine applications where shore power system faults often cause electric currents via the water. An isolated charger on a boat allows you to isolate the house system ground from the engine and alternator ground, which is typically in contact with the water.

The non-isolated charger will have three power connections. One positive in, one positive out, and a common ground. Most people would install a large-post negative bus bar near the camper battery. The negative from the truck battery, the negative for the camper battery, and the negative for the dc to dc charger would all connect to that bus bar, as would the negatives for all of your camper load circuits, usually via another bus bar with smaller connections.

 

[Vic Harder]

you want the non-isolated one. The isolated one is for marine applications where you do NOT EVER want current to flow from shore to ship unless it is protected.

 

[Glenn]

OK, so with the Non Isolated one the house battery still can’t draw down the starter battery when the truck is turned off because..,……. It’s isolated through the positive wire of the dc to dc charger?

 

[Jon R]

Yes the dc to dc Charger functions as a battery isolator and never allows the truck battery to receive energy from the camper battery. The engine running logic determines when the camper battery can receive energy from the truck, and you set the parameters so it only provides current when the engine is running. However, that is not what the “isolated” or “non-isolated” in the product name is referring to. That name is referring to battery negative connection isolation as I described above.

 

[Glenn]

OK, got it. Thank you !

 

[Dadocut]

I can think of a few simplifications to your proposed design:

You can build your system without the 60A relay providing power to the DC-DC converter from the engine battery. I suggest doing what I did: mount a BlueSea MRBF fuse on your engine battery terminal that connects to a thick wire (I used 4 gauge) and run the fused power (and a ground wire connected to the battery) to your camper. Make sure the wire is routed carefully, use some sort of covering over the wire. I used Ancor wire that was recommended on this forum. A great choice, highly recommend. I used a SB120 anderson connector in this path.

To enable the DC-DC charger to run only when you need it, route power from a dashpanel switch to the enable input of the DC-DC charger. My truck has "upfitter switches" that I used for this purpose. This way you only charge the battery and load the engine when you really need it. I'll bet you find that solar keeps your battery charged adequately. I used a 45A anderson powerpole between the truck and camper for this charge enable circuit. I think you'll find a simple switch to the DC-DC charger enable will be much simpler than an engine mounted relay.

The non-isolated charger is the correct choice. You tie the camper ground to the engine ground. One ground is a good thing.

Do you really need a 2000w inverter? Your stated loads are all under 1000w, you could use a 1000w inverter and then require much more reasonably sized wires. A 2000w inverter requires over 150A from a 12v battery! That's a lot and will require both very thick, stiff wire and require the inverter and battery to be immediately adjacent. Generally speaking one should run a 24v battery for a 2000w inverter -- but you really don't want that added complexity and cost. Do consider a 1000w inverter instead. I use a 300w inverter and it powers all my chargers (laptop, camera, Qi, drill battery etc.) just fine. But then I use propane for cooking. Everyone has slightly different requirements.

I second the recommendation for a battery monitor. I use the old school Bogart Engineering Trimetric as well as a bluetooth battery management system in my homemade battery pack.

If you draw a schematic we can accurately comment on what you;re doing. (one of these days I'll draw one for my system!)

Hope this helps

 

[Dadocut]

Regarding your question about solar panels...

Earlier flexible panels glued to the roof had reliability problems. My 2015 flexible cells crapped out and I replaced them with two rigid panels. I have a Halmark popup so the extra roof weight was not a problem. Maybe new flexible panels work? I don't know.

Serial or Parallel? Serial is better in that you have less voltage drop between the cells and the solar controller (this assumes your solar controller can handle the higher voltage of the serial cells). But if one panel is in shade then the power output is zero. Both have to be in the sun to get any output. I did parallel connections so one could be shaded and I'd still get some output.

I also added a "solar panel enable" switch between the positive panel output and the solar controller. I like to be able to control/isolate different parts of my system.

 

[Glenn]

The non-isolated charger is what you want unless you have a specific reason you want to isolate the truck ground from the camper ground.

Isolated versus non-isolated refers to whether the grounds of the input and output sides of the charger are kept isolated or are connected. Others have said Victron makes the isolated chargers primarily for marine applications where shore power system faults often cause electric currents via the water. An isolated charger on a boat allows you to isolate the house system ground from the engine and alternator ground, which is typically in contact with the water.

The non-isolated charger will have three power connections. One positive in, one positive out, and a common ground. Most people would install a large-post negative bus bar near the camper battery. The negative from the truck battery, the negative for the camper battery, and the negative for the dc to dc charger would all connect to that bus bar, as would the negatives for all of your camper load circuits, usually via another bus bar with smaller connections.

you want the non-isolated one. The isolated one is for marine applications where you do NOT EVER want current to flow from shore to ship unless it is protected.

I thought I understood

After reading and thinking about the “negative buss bar”, I’m not sure I trust the thin metal truck bed for a good ground.

So, would running a short #4 ground cable from the chassis frame directly below, and into the truck bed through a grommet and attached to the negative buss bar with the house battery and dc to dc charger neutrals accomplish this?

And if I am using the chassis, then do I really need a #4 negative wire all the way from the starter battery back to the negative buss bar that’s in the bed of the truck for the shared neutral that is already attached to the frame?

I know from experience with my boat trailers and using the trailer chassis as ground, 90 % of the time electrical problems end up being traced back to a bad or poor grounding issue

Thanks guys.