Van solar system - does this make sense?

[josequesado]

Hi there!

First time posting here... I'm building a van with my partner and the electrics are our biggest headache so far. We are noobs on the subject and so, we would much appreciate if someone could check if our solar setup makes sense or if you would change something.

Our system should be:
- 1x 450W; 24v Solar Panel (Vmp: 41,5V / Cmp: 10,85A) (Link)
- 1x MPPT charger: 20A (Link)
- 2x Lithium batteries 100Ah; 12v (Link) (thinking of expanding it to 300Ah when the budget is available and if needed).
- 1x DC-DC charger to use our alternator (we have a 2017 Mercedes Sprinter) (Link)
- 1x Inverter/charger 2000W; 12v (we are at the moment searching for one that is available in Spain that is Lithium compatible so that we can also charge from shore power).


Is there something that does not fit or that you would do differently?
We saw the DC-DC charger from Renogy but ditched it as it did not look like it would be as efficient as having 2 separete components for solar and alternator.


Thanks for any input!

 

[the1andonly]

Are you running a 24v system? The mppt at 20A and inverter charger 12V seem to be in conflict.
Mppt controller should be 40A if 12v.

 

[The Wino]

Maybe indicate what your power is required for and what time of year

 

[tacr2man]

Raul will probably be along soon to give you best advice

 

[gus-lopez]

Or Lenny HB & autorouter

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[TheBig1]

I would not be fitting that solar panel, rather 2 smaller panels. If one panel fails in the middle of nowhere, you don't lose all solar capacity. The physical size on a vehicle makes cracking it an ever present risk

 

[the1andonly]

In your spec there is no method of charging the starter battery .
I use Votronics duo mmpt controllers. One 30A on a 330W domestic panel 48V 1.7x1m a 120w and 100w 20V panel on a 20A duo. The controller can charge Lithium and trickle charge SB Lead.

 

[autorouter]

That setup seems to be powerful and well-balanced, but it's only half the story. What loads will you be powering? Will you have hookup available some of the time, or are you intending to be off-grid all the time.

A Victron Multiplus combined inverter and charger is a very useful setup, even more useful if you will be on hookup some of the time. It will talk to a Victron MPPT solar controller. It is compatible with the BMS of quite a few (but not all) LiFePO4 batteries, so you might like to check this before you buy the batteries.

As the1andonly says, if using 12V batteries the MPPT needs to be 40A. The amps rating is the controller output (at 12V) which will need to be 450/12 = 38A. On the input side, the voltage is the critical factor, but 41V is not very high so any MPPT controller will handle that.

 

[Raul]

Hi there!

First time posting here... I'm building a van with my partner and the electrics are our biggest headache so far. We are noobs on the subject and so, we would much appreciate if someone could check if our solar setup makes sense or if you would change something.

Our system should be:
- 1x 450W; 24v Solar Panel (Vmp: 41,5V / Cmp: 10,85A) (Link)
- 1x MPPT charger: 20A (Link)
- 2x Lithium batteries 100Ah; 12v (Link) (thinking of expanding it to 300Ah when the budget is available and if needed).
- 1x DC-DC charger to use our alternator (we have a 2017 Mercedes Sprinter) (Link)
- 1x Inverter/charger 2000W; 12v (we are at the moment searching for one that is available in Spain that is Lithium compatible so that we can also charge from shore power).


Is there something that does not fit or that you would do differently?
We saw the DC-DC charger from Renogy but ditched it as it did not look like it would be as efficient as having 2 separete components for solar and alternator.


Thanks for any input!

All looks good apart from the mppt. You need a 30A instead of the 20a to small for 450w. And you need it if you plan a inverter.
If budget allows, apart from the batteries ( good choice), try to keep all components victron. You will be able to get a multiplus 2000va 12v 80a inverter charger in Spain. As well as the 100/30 mppt charger . Put all this together you will have a decent system and good balance.

 

[Raul]

Ps. On the charge side you multiply the amps of the charger by the absorb voltage 14,4v, not the nominal 12v. A 30a controller, can handle 30x 14,4v = 432w, unless you plan more solar later, you don’t need a biger solar charger. For charging the starter, it will be done via multiplus, it has a connection for charging a secondary 12v starter, and yes it will charge it from shore as well as solar. That’s what I have and it does.

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[Lenny HB]

Rather than a 450watt panel I would go for 3 x 150 watt then if one or two of them are in shade you will still have power, also not sure how well a panel that size would stand up on a moving vehicle.
As said you need a 40 amp solar controller.

Victron B2B's have a reputation for overheating if not in a well ventilated space. Have a look at the Votronic B2B's they are fan cooled and you can program them for different output levels to suit your batteries & alternator.

Do check the lithiums can be parelleled up OK, some can only be paired i.e. max of 2.

 

[josequesado]

Maybe indicate what your power is required for and what time of year

So we evaluated our energy needs around 180Ah/day. We will be using propane to cook.
Most of our consumptions will be 12 volt (light, fridge, water pumps, toilet fan,...) but we will install an inverter (2000W probably) to be able to use some kitchen appliances and to be able to use some power tool if needed.

Our project is to circle the globe and we are trying to make as much time as possible in summer season. We will be as far north as Mongolia and as far South as Patagonia.

Thank you!

 

[josequesado]

In your spec there is no method of charging the starter battery .
I use Votronics duo mmpt controllers. One 30A on a 330W domestic panel 48V 1.7x1m a 120w and 100w 20V panel on a 20A duo. The controller can charge Lithium and trickle charge SB Lead.

So you charge your starter battery with your MPPT? Wouldn't it be charging from your alternator while you ride?

 

[Lenny HB]

So we evaluated our energy needs around 180Ah/day.

What are you running a furnace?
I would have thought more typical in good weather 15-20ah/day, winter 45-60ah/day.

So you charge your starter battery with your MPPT? Wouldn't it be charging from your alternator while you ride?

The alternator will be kicking out 14.4v the solar controller will see this as the battery fully charged and will turn off. Also it only charges up to a max of 1 amp so wouldn't cause any problems.

 

[the1andonly]

So you charge your starter battery with your MPPT? Wouldn't it be charging from your alternator while you ride?

Not when van is stationary. I have a Ducato base which with quiescent drain (ECU's and alarm immobilizer etc) will drain Starter battery in 3 weeks and may cause problems with the "flakey" electronic Modules on Sevel vans especialy air bag. Which is why there is a particular way to remove the battery. FOr me the duo charge is the simplest method there is an alternative but cant think what it is.

edit having read your earlier post you wont be stationary for 3 week so Lenny HB post is more relevant.
power consumption is a bit on the high side, but ! just check your numbers.

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[josequesado]

What are you running a furnace?
I would have thought more typical in good weather 15-20ah/day, winter 45-60ah/day.

The alternator will be kicking out 14.4v the solar controller will see this as the battery fully charged and will turn off. Also it only charges up to a max of 1 amp so wouldn't cause any problems.

We overestimated it on purpose to be sure we are not underdimensioning the system. I state some of our values in case they are ridiculous you can warn me!

In one day (this is a little exagerated as I said, but we plan on a 200Ah battery bank):
- Charging the computer: 20 Amp/h
- Kitchen blender/cooker: 70 Amp/h
- LED lights: 7 Amp/h
- Fan: 9 Amp/h
- Water pump: 2 Amp/h
- Charging phone: 2 Amp/h
- Charging camera: 1 Amp/h
- Fridge: 9 Amp/h

So... 120 Amp/h/day here. Is there something absurd here?

Sorry for the ignorance but this is really new terrain for me!

 

[autorouter]

- Fridge: 9 Amp/h

This looks a bit suspect, I'd expect it to take a lot more. What fridge are you planning on using? Compressor or 3-way?

A compressor fridge might use say 4A when the compressor is running. If it was running continuously for 24 hours, that would use 4 x 24 = 96 amp-hours. The thermostat will cut in to stop it running continuously, so it might use say 30% of that if it's cold weather, and maybe 50% in hot weather, so that's a daily consumption of 36 to 48 Amp-hours (Ah).

What some websites seem to do is to average that out over a 24hr period, to give the average amps over the whole 24 hour period. So this could be written as 1.5A instead of 36Ah per day, and 2.0A instead of 48Ah per day.

Many of them get the units confused, and call it 1.5A/h, which technically is nonsense, but is quite commonly used. If you don't call it 1.5A, then you could call it 1.5 Ah/h, but nobody is comfortable with that for some reason.

 

[pappajohn]

Two items on the list you can forget......phone and camera.
Just fit a couple of 5v usb sockets.
No point inverting 12/24v to 230v then back to 5v via a mains usb plug

 

[Raul]

A compressor fridge will take 25-30ah per day tops.