Installing solar energy on a RV

[missoo]

Hello all !

I am currently thinking of my new solar system, but I have so many questions ... (and sorry If my english is not perfect I hope you would understand me right).

I have decided to install in parallel 2 solar panels of 215W each (they have 72 cells).
I calculate the Voc and Isc (+10 % security) to define which MPPT I need. The numbers I get are : for the Voc 45,52 V and for the Isc 12,15a.
If I understand right, with these results I could use (for example) a MPPT victron 100/20, however on their website they say that this MPPT cannot be used for 430 w solar panel (the limit woud be 290 w with a 12v battery).
Can you explain me why ? I don't understand why we should calculate the Voc and Isc if we are limited by the maximal power of our solar panel anyway...
An other thing, is that somebody told me that I could go with the 20a MPPT anyway ... But if it gets limited at 290 w , there are some energy loss right ?

Also, I am wondering if I can go with epever. Are they still good quality products ?

Finally, I can't decide which battery capacity I'd like. I'm going to build a LifePo4 12 V battery, but I don't know if I go with 200ah or more ....
I know with 430w of PV it's going to be difficult to charge my battery, but I'd like to also charge it while driving. I am not sure the name of the equipment I need in english, if you could tell me My RV is euro 6, so I can't use the cyrix ones, if you get what I mean....
So... any recommandations for my battery capacity ? Is it usefull to get more than 200ah , in case I wan't a backup for cloudy days ?

I'll probably have new questions later.

Thank you so much for your help

 

[HRTKD]

Size your battery on how much power you need on a daily basis and the number of days you want to go without a recharge or a full charge.

The more solar you put up, the faster you can charge the battery.

You can use the Victron 100/20, but if the panels have more watts than the controller can turn into 20 amps then the controller will simply not produce more than 20 amps of charge. If you have the watts and need 30 amps of charge, move up to a larger controller. The key is to not exceed the maximum input voltage rating on the controller.

To charge LiFePO4 from an alternator you will want to put in an DC-DC charger, like the Victron Orion.

 

[missoo]

Thanks for your answer

Yes I forgot to say that my estimated consumption was 100amp per day.

But if I have 430 w PV, does it mean I can really produce 430 w ? I read that the PV could produce 70 % of this maximum power ... Which would be 300 w... Is that true ?
How do I know if 20amp is enough for me ? Is it according to my instant consumption ? I am so confused !

Is there a "risk" to charge slowly a LifePo4 battery ? I believe it will get fully charged only rarely... I planned to stay in some places for a long time, which means I won't drive that much... Is still a DC-DC charger interesting ? How long would it takes to charge my battery for example ?..
By the way, I just saw there was a DC-DC charger Orion 12 - 24V . Does it mean that I can charge a 24 V battery with it ?
Would it be more interesting to get a 24 V battery as my solar panel are 24 V / 72 cells ?
If everything is in 24 V, are there less energy loss ?

Sorry so many questions ! Thank you for your help

 

[HRTKD]

What type of RV? On a trailer, it's easier to disconnect the alternator power from the rest of the trailer, that it is to do on a motorhome. On a trailer you have to keep the 7-pin connected to get lights (brake, turn, etc). The existing 12v power is also used to power the trailer's breakaway brake system (on a trailer with brakes of course). Installing a DC-DC charger like the Victron Orion is a good way to ensure that your LiFePO4 batteries are properly charged from the alternator and not overcharged. The Orion is also a good device to use to ensure you don't burn out your alternator.

Solar panels rarely produce the maximum watts. This is due to many factors. The strength of the sun is the primary reason. Clouds, haze, orientation and dirt all contribute. Overpaneling is a way to work around some of those factors. As long as you don't exceed the input voltage rating of the solar charge controller you're safe.

The voltage of the solar panels doesn't matter in the context of battery voltage. An MPPT solar charge controller will work with the voltage of your battery.

24v batteries make sense when you need to use a big inverter, say more than 3000 watts. 24v systems come with consequences. Almost everything in your trailer is 12v. To get those devices 12v power you have to install a step down converter (24v to 12v) of a necessary size to satisfy the amperage requirements. Tongue jacks and fifth wheel landing jacks can draw a lot of amps!

I boondock for up to 10 days at a time with 1280w of solar and 560Ah of LiFePO4. Spring, summer and fall, I run my generator only to power the microwave and air conditioning. In the winter I use the generator to run space heaters and the tank heaters as needed.

 

[missoo]

I have a renault master 3 of 2018. I don't know if you can find it in US

So, in my situation, I guess a MPPT 100/30 would be enough, even if the theorical maximum production would be 33amp ?

I couldn't find out what are tongue jacks and fifth wheel landing jack, could you tell me ?..

I do have one more question.
Is it necessary to use a battery protect in addition of my MPPT and my BMS ? I thought both of them were alreday protecting the battery of over charging/discharging.

You do have a lot of solar energy !!! I don't have much more space on my roof

 

[HRTKD]

Tongue jack:

Since you have a van, you don't need to worry about a tongue jack, or trailer brakes.

Many inverters have the ability to stop consuming power when they detect a low voltage situation. This a good proactive practice. The BMS can also shut off discharge when it detects a low voltage situation. The BMS should be considered the final step. It's always better to have the downstream devices stop consuming that have the BMS just cut everything off. For example, the inverter might cut off at 11.9 volts and the BMS cuts off at 11.8 volts (made numbers).

I haven't run the numbers to see if you need the 100/20 or 100/30. Go on the Victron website and download their MPPT Calculator. You can enter your solar panel's info and the spreadsheet will help you find the right MPPT controller. Link to the calculator: https://www.victronenergy.com/upload/software/VE-MPPT-Calc-3_7.xlsm

 

[mikefitz]

Two 215 solar panels should be suitable. The OC voltage is a little high to consider connecting in series so you need a parallel connection. I recommend the Victron Smart Solar 100/30 controller, this will allow , under good solar conditions, the full 30 amps output. In practice the typical output may be less, somewhere around 25 amps. You could use the 100/20 but it would limit your current to 20 amps.
EPever controllers are an low cost option but the quality, ease of user programming, and charge process, is not as good as the Victron. Using the Victron phone app and the Bluetooth connection you can see exactly how the Victron controller is performing and it stores a record the past 30 days of energy collected. Setting the voltages and charge parameters is easy via the app.

For charging from the engine you need a battery to battery charger like the Victron Orion. Since you have a powerful alternator on your Renault you could fit a more powerful battery to battery charger from Sterling Power or Votronics ( or use two 30 amp Orions in parallel).
Since lithium charges easily, a 60 amp battery to battery charger would add around 1/3 of capacity to your battery with one hours driving. With your 430 watts of solar and a typical 6 useful sun hours in summer, the batteries will be easily charged, ( you get 6 x 25 amps over the day, say 150Ah). Most power use in a European RV is for the fridge with the battery used as an energy store for overnight.

Dont underestimate the time, skill levels and additional test and charging equipment you need to build a Lithium battery. There are a number of ready built lithium batteries that are cost effective, In my experience 200 Ah of battery is very practical in a camper provided you do not have high power inverters.

It sounds as if you are based in Europe. The major manufactures of solar and other chargers for RVs are, Victron, Votronics, and Sterling Power. All have European support and have proved to be functional and reliable in RV applications.
If you cannot discribe something in English, use your own language. I will be able to translate.

Mike