Educate me: solar panels, DC to DC charger, Inverter

[bmklawt]

I'm thinking of adding solar and lithium batteries to my 1975 Tradewind, I can get six 100 watt solar panel on the roof, start with three 100Amp batteries with the option to add more if I find I need them.
I've been reading a lot, mostly on Victron components and am still not clear on a few things. My questions are.


1, To charge my camper batteries from my truck it looks like I need a DC to DC charger, What size do I need, isolated or non-isolated, how many amps can you put through the power connector on a 7 way trailer plug. How do you keep from running down the truck battery.


2, Solar panels, I read about connecting them in series, parallel or series/parallel, I don't get it, I know what series and parallel are but why one over the other


3, Inverter Charger, would it hurt to use a Victron Multiplus 3000VA inverter even if I will never need that much power, I would choose the 3000VA just because it is physically smaller than the 1600VA or 2000VA inverter.


Thanks much for your input.

[Winemaker]

Originally Posted by bmklawt

I'm thinking of adding solar and lithium batteries to my 1975 Tradewind, I can get six 100 watt solar panel on the roof, start with three 100Amp batteries with the option to add more if I find I need them.
I've been reading a lot, mostly on Victron components and am still not clear on a few things. My questions are.


1, To charge my camper batteries from my truck it looks like I need a DC to DC charger, What size do I need, isolated or non-isolated, how many amps can you put through the power connector on a 7 way trailer plug. How do you keep from running down the truck battery.

The higher the amps on the Orion the larger wire you will need to run from the tow vehicles battery, the more load you will put on it's alternator, and the faster your trailer battery will charge. There are a ton of variables (i.e. the gauge of wire in your existing 7 way plug) that need to be considered but it will always be safer to just run the right wires for the model you buy. Keep in mind that Victron provides no way to limit the amperage draw from the tow vehicle to the Orion.

2, Solar panels, I read about connecting them in series, parallel or series/parallel, I don't get it, I know what series and parallel are but why one over the other.

There is a ton of great information here:
https://www.explorist.life/how-to-ch...trical-system/

and here:
https://youtu.be/KJ5zCY5EBeQ


3, Inverter Charger, would it hurt to use a Victron Multiplus 3000VA inverter even if I will never need that much power, I would choose the 3000VA just because it is physically smaller than the 1600VA or 2000VA inverter.

Main issue with a "larger than needed" inverter would be the power it uses just to run itself and the noise the fan will make if it needs to cool itself. All inverters will use some energy just by being on. Bigger inverters will have bigger cooling fans that will be louder when they are working.

Overall I think the Explorist series of videos is one of the best resources around...
https://youtube.com/playlist?list=PL...aI5SQrS1kKLgEF

It's a deep rabbit hole you are entering into but there are some people on the forum who are 1000 time more knowledgeable about all this than I am... Lewster for example.

Hope this helps at least get you started!

Mitch

[Winemaker]

Forgot to address the isolated/non isolated part...

Originally Posted by bmklawt

1, To charge my camper batteries from my truck it looks like I need a DC to DC charger, What size do I need,]isolated or non-isolated, how many amps can you put through the power connector on a 7 way trailer plug. How do you keep from running down the truck battery.

Isolated will have a unique ground wire (positive and negative input and output) and non-isolated will share the ground wire and just have three inputs (positive from the tow vehicle, common ground/negative for both vehicle and trailer, and positive out to the trailer batteries). unless there are non-conductive materials in the construction of the trailer (fiberglass shell, wood... usually not an issue for Airstreams) you should be able to use the non-isolated model.

[dznf0g]

Originally Posted by bmklawt

I'm thinking of adding solar and lithium batteries to my 1975 Tradewind, I can get six 100 watt solar panel on the roof, start with three 100Amp batteries with the option to add more if I find I need them.
I've been reading a lot, mostly on Victron components and am still not clear on a few things. My questions are.


1, To charge my camper batteries from my truck it looks like I need a DC to DC charger, What size do I need, isolated or non-isolated, how many amps can you put through the power connector on a 7 way trailer plug. How do you keep from running down the truck battery.


2, Solar panels, I read about connecting them in series, parallel or series/parallel, I don't get it, I know what series and parallel are but why one over the other


3, Inverter Charger, would it hurt to use a Victron Multiplus 3000VA inverter even if I will never need that much power, I would choose the 3000VA just because it is physically smaller than the 1600VA or 2000VA inverter.


Thanks much for your input.

Fine, Winemaker set the bar with Lewster, and that ain't me but I'll throw in my bit.

1) If you want to use your existing TV wiring (I assume it is a 30 amp circuit), you will need to stick with a (Victron) 20 amp unit. The 30 amp model supplies 30 amps, but draws a few amps more than that, so it most likely will blow fuses from time to time. I chose an 18 amp Victron, isolated.

2) Parallel is less affected by partial shading, Series is more efficient, especially if your wiring is smaller gauge. Series parallel could be a good compromise. Much is dependent on your most frequent campsite solar lighting.

3) I, personally only use an inverter to run items I have to have 120V for. No hairdryers, coffeemakers, microwaves, etc. I only have a 600 watt inverter, and really don't use it much. I see no need whatsoever for a MASSIVE multiplus.

This is a very 30,000 foot level answer. Much is dependent upon your individual lifestyle, and there is much more detail that needs filling in, but you need to make those lifestyle decisions before going down the rabbit hole, IMO.

[bmklawt]

I would like to be able to use a microwave, coffee pot, TV, charge laptops, phones and I’m sure my wife would like to use a hair dryer and the normal 12 volt stuff.

[dznf0g]

Originally Posted by bmklawt

I would like to be able to use a microwave, coffee pot, TV, charge laptops, phones and I’m sure my wife would like to use a hair dryer and the normal 12 volt stuff.

Then you are definitely going to need a larger lithium battery bank, and probably a large dedicated DC/DC converter circuit from tv battery all the way back.

Sent from my SM-G950U using Airstream Forums mobile app

[vanderwielen]

Originally Posted by bmklawt

I would like to be able to use a microwave, coffee pot, TV, charge laptops, phones and I’m sure my wife would like to use a hair dryer and the normal 12 volt stuff.

Possibly. The issue will be the allowable current draw from the lithium battery. Most allow a 1C draw, which on a typical 100AH battery, would be 100 amps or about 1200 watts...which won't quite make it with a hair dryer or Keurig coffee maker.

So...You should budget for a few more lithiums or a BattleBorn GC series battery.

From the sound of your needs, budget about 8K if you install it yourself.

Good Luck.

[waninae39]

Its best to run as high a voltage to the MPPT controller

this double the V is half the I for the same power W.
power loses are I2 *R

[jnm30327]

I wanted to be able to run microwave, coffee maker, toaster, or high dryer. Not all at once of course, but the 1000 Watt stock inverter limits what you can do. I opted for the Multiplus II but used AC Out 2 from the Multiplus to power air conditioners and water heaters. Everything else in the trailer can run from batteries.

I don't know your budget, but two Battleborn GC3s (270 Amp-Hrs each) fit nicely under the bed and their form factor uses less space than an equivalent number of 100 Amp-Hr lithium batteries. I connected solar panels in series to keep wire size down but also carry a 160 Watt suitcase solar panel for shady campground.

DC-DC charger feels to me like an essential to avoid potentially damaging the TV alternator.

With 300-400 watts of solar, these arrangements will give several days of comfortable experiences and few limitations on what can be used.

Main limit on boondocking or dry camping - gray water.

[Winemaker]

Originally Posted by jnm30327

I don't know your budget, but two Battleborn GC3s (270 Amp-Hrs each) fit nicely under the bed and their form factor uses less space than an equivalent number of 100 Amp-Hr lithium batteries.

I went with the SOK 206 Amp-Hr marine batteries. Could buy two for the price of one Battleborn GC3 and have 412AH. Get 4 of them for less $$$ than two of the GC3 and they will take up less room and provide 824AH.

https://www.us.sokbattery.com/produc...ed-plastic-box

I agree on gray water being a limit that is harder to overcome than power!

Cheers!

[jimdelane]

Solar panels:
Put in parallel, you have less problems with shading. Putting in parallel, you use smaller wires and the higher voltage produced is more efficient but partial shading on a series will cause issues. Go with a lithium compatible MMPPT solar charge controller. They are close to 100% efficient - 25 to 30% more efficient than a PWM controller. In real terms that means that theoretically, you harvest over 95% of a 100w panel (95-100w) vs 70-75% of the panel (70-75w). Combine that with the fact that solar panels never put out 100% of rated power and the difference adds up to a lot of power. Panels are rated under optimal conditions - perfect sun, temp and max sun angle. In real life, due to clouds, time of day/year and location, this is not likely. Figure about a solar output of 75% efficiency. Putting (2) panels in series to produce 24v and parallel with the other panels placed in series will provide a good voltage which, even reduced due to conditions, will efficiently produce good power. Most 12/24v solar chargers will autodetect the incoming voltage and adjust accordingly.

Inverters:
There is no reason to live like a refugee. With a large enough inverter, you can run microwaves, hair dryers, instapots, air fryers, induction stove tops and air conditioners. Usually 3000w is a good number. Watts = amps x volts
1200w = 12v x 100A = 120v x 10A
A 1500w hair dryer will draw 125A on a 12v bank.
It is a good idea to oversize the inverter as the harder you work them the hotter they get. It is better to run 1900w on a 3000w inverter than a 2000w inverter.
Also, a lot of times, you may have the fridge, coffee pot, lights, radio, and a couple of other things going at the same time. More energy is better.

Lithium batteries:
100Ah batteries have 1280 watt hours. 1280w for 1 hr/128w for 10hr
200Ah batteries have 2560 watt hours.
300Ah batteries have 3840 watt hours.
400Ah batteries have 5120 watt hours.
and so on.
Do an energy audit. Figure on how much you might use and figure on how you will replace it on a daily basis. Figure on having enough capacity to go a few days in a worst case with little or no charging.
The more amp hours (energy), the better. Lithiums have 99% charge efficiency which means every watt that goes in, stays in - none wasted on heat like LA/AGM batteries. The low internal resistance allows max charge until the battery is full and then the BMS cuts the charge off - both features can cause issues with an improperly designed alternator system. Hence the DC-DC charger/Sterling APD/HD alternator/external regulator stuff.
Lithiums can be discharged over 80% and still have over 12.5v. You can cobble a bunch of 100Ah batteries together or go with fewer 200,300 or 400ah batteries to achieve the larger bank. Larger batteries generally will provide a smaller footprint and higher charge/discharge rates. For example, (1) BattleBorn GC2 has recommended 50A charge/100A discharge whereas (2) in parallel has recommended 100A charge/200A discharge capacity and so on. The BattleBorn GC3 270Ah battery has a 135A charge/300A discharge. Both the Chargex and AMPS 300ah batteries have a 300A charge/300A discharge capacity.
You have lots to choose from. Remember that what you take out - you need to replace. That is where the Victron 712 or Victron SmartShunt come in. Both are shunt based and give you an accurate idea of how much energy you actually have.

Hope this helps

[dsatwork]

You already have the answers you need on DC to DC charging and the solar panel question, I'll tell you about my reason and experience with our Victron Multiplus ll I just finished installing on our 50amp 2015 30RBQ and we live in it fulltime. There are many advantages to having a Victron Multiplus ll on a 50 amp RV and if you are 30 amp you only need a standard Victron Multiplus. Either way you can power your entire trailer including all of your appliances and your inverter, gfci and bedroom outlets. The most useful feature I think it offers is power assist. As I said, we live fulltime and that setting has kicked in almost everyday since we installed the MP ll. As a 50 amp trailer on a 30 amp service, power assist takes the guesswork of constantly monitoring power needs by pulling any power over the 30 amp service from the batteries. This is a game changer for fulltime living. In regards to noise, our boondocker 60 amp converter was more annoying than the MP ll. Of course we can also pullover anytime on our travels and use anything we want in the trailer without kicking on a generator. The Victron 30 amp DC to DC charger protects our alternator and makes sure we are topped off by the time we get to our next location. We also have our 400 watts of solar on the roof in parallel along with too bluetti 200 watt panels in parallel as well for ground deploy when the sun angle is bad or additional wattage is needed.

[steve46]

I, too, am considering adding solar to my vintage Airstream. I have a ‘76 Trade Wind that has been totally redone and it only has one battery, a conventional Interstate 12 volt lead acid type. While we do not do a lot of off grid camping, since this Airstream has just the one battery, and I cannot easily add another at this point, it seems that a portable solar unit would be wise to implement, at least as insurance. That way the battery can be recharged in those instances where we may not have ready access to shore power.
While solar is a new concept for me, and I am rather uninformed about solar, I am leaning toward one of the portable Zamp kits—they have a 140 watt and a 180 watt kit, both of which look fairly straightforward to hook up and use. Perhaps the most vexing issue is what size solar arrangement is really needed, which appears to be a personal choice, largely based on power usage, which I certainly don’t monitor.
I look forward to your decision on what you select, however it does appear that you are seeking something upsized from what I envision, and perhaps you desire a permanently attached versus portable solar choice.

[bmklawt]

Looking at a different system now "MPP Solar" all in one system https://watts247.com/product/pip-lv2424-msd/
Have a couple of questions, can I add a 10amp DC to DC charger to the batteries and use the existing 7 pin trailer wiring and would this negatively affect the MPP Solar inverter, trailer batteries, truck Batteries or alternator?


Your input is greatly appreciated,
Bruce

[KSA63]

Originally Posted by bmklawt

Looking at a different system now "MPP Solar" all in one system https://watts247.com/product/pip-lv2424-msd/

Your input is greatly appreciated,
Bruce

Hi Bruce, the system you linked to doesn’t look suitable for a trailer. It looks more like this system is designed as an entry level home/cabin system.
Kevin

PS> if you are looking for some cost savings in an all in one 12v charger inverter then you may be interested in a Renogy or Kisai product. You will still require a separate solar charge controller.

[uncle_bob]

Originally Posted by bmklawt

Looking at a different system now "MPP Solar" all in one system https://watts247.com/product/pip-lv2424-msd/
Have a couple of questions, can I add a 10amp DC to DC charger to the batteries and use the existing 7 pin trailer wiring and would this negatively affect the MPP Solar inverter, trailer batteries, truck Batteries or alternator?


Your input is greatly appreciated,
Bruce

Hi

Going to a 24 volt system in a trailer is a bit exciting. Most if not all of your existing 12V gizmos will no longer work dire t off the batteries. Charging off of the 7 pin will indeed mean a 12 to 24V DC/DC. If you are looking at a massive system, you might just go to 48V and be done with it. Put in something like 8 or 12 BB 12V batteries and away you go.

For a system that only has one or two 100AH / 12V batteries, there really is no advantage of going to 24 or 48V. Even at 4 batteries, it's still not obvious you would want to pay all the extra that doing the higher voltage involves.

Bob

[bmklawt]

To be honest I totally didn't think about needing to run my 12v stuff, Duh.
I'm liking the MPP Solar for it simplicity and cost, couldn't I run a Victron Orion 24/12-40 DC-DC Converter

[uncle_bob]

Originally Posted by bmklawt

To be honest I totally didn't think about needing to run my 12v stuff, Duh.
I'm liking the MPP Solar for it simplicity and cost, couldn't I run a Victron Orion 24/12-40 DC-DC Converter

Hi

In order to be legal, you need a 12V battery for the break away setup. Having that run through a bunch of this and that sounds iffy. It's not clear if it's even legal ( I'm not a lawyer so I don't know that answer ...).

If you have real loads on 12V ( like a fridge ) the efficiency loss through even a good DC/DC is going to be noticeable.

If cost is the only concern here, there are a lot of lower cost options. This is a "you get what you pay for" sort of world. I'm not sure that going with the lowest bidder is the best approach on something like this ...

If complexity is the concern, you really aren't saving much. There still is a lot to be done and getting a home solar gizmo to be happy in an RV adds more issues to the list.

Bob

[tusocks]

I had Vinnies in Tallahassee Florida install a Victron 12/12-18 DC charger in my F250 diesel recently. They stated that they knew how to properly install such a charger however they obviously did not since they have never been able to get it to effectively charge the lithium batteries in our Classic that has the electric refrig. Despite numerous phone calls back and forth from our home in Michigan to Vinnies after returning home from his shop in FL he finally admitted that they did not know how to get the charger to function properly so they just simply refunded my money. Much frustration & time (not to mention expense of towing) was wasted on my behalf. I would appreciate recommendations for any service center that is known to have a good reputation for installing DC-DC chargers that is within a 2 days drive in any direction from southern Michigan. Thanks for your help.

Mark/Jeannie

[JeffKim]

Originally Posted by tusocks

I had Vinnies in Tallahassee Florida install a Victron 12/12-18 DC charger in my F250 diesel recently. They stated that they knew how to properly install such a charger however they obviously did not since they have never been able to get it to effectively charge the lithium batteries in our Classic that has the electric refrig. Despite numerous phone calls back and forth from our home in Michigan to Vinnies after returning home from his shop in FL he finally admitted that they did not know how to get the charger to function properly so they just simply refunded my money. Much frustration & time (not to mention expense of towing) was wasted on my behalf. I would appreciate recommendations for any service center that is known to have a good reputation for installing DC-DC chargers that is within a 2 days drive in any direction from southern Michigan. Thanks for your help.

Mark/Jeannie

Sort of wondering, they installed the charger in the TV? How is it connected to the batteries in the trailer? Almost always it's installed in the trailer. There are also a number of parameters with the charger that need to be set properly to detect a running engine. Are you able to hook up to it with Bluetooth when connected?

With an 18A charger, it's nice to have but it will take a while to fully charge a battery. For a 100Ah battery that's 5 1/2hrs. Driving with the refrigerator going full blast at something like 5A however it should be able to keep up.