Design feedback on solar/electrical system (1 Viewer)

[scotjimland]

Your RCD / Main switch and MCB must be TWO pole.. ie break both Line and Neutral .. see IEE regs I posted for guidance .

You could also install a an RCBO which is both RCD and MCB in one unit.. see earlier posts and picture of mine

as mentioned, your RCD is on wrong side of input socket

 

[Red_48]

Diagram updated.

The alternator will be OEM Mercedes Sprinter. No idea if it's smart of not.

Using the load estimate that includes inherent efficiency loss the watt-hours = 1772.

Wh / Volts @12 = 147 Ah. I used this site to calculate the load:

https://www.wholesalesolar.com/solar-information/start-here/offgrid-calculator#applianceTable

Let me know what I'm doing wrong. I'm happy to overestimate as that will give me longer run times in inclement weather.

 

[scotjimland]

Diagram updated.

sorry it's still wrong,.. you don't seem to have grasped that it has to be TWO POLE RCD or RCBO , and and fitted after the incoming socket

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[Lenny HB]

Diagram updated.

The alternator will be OEM Mercedes Sprinter. No idea if it's smart of not.

Using the load estimate that includes inherent efficiency loss the watt-hours = 1772.

Wh / Volts @12 = 147 Ah. I used this site to calculate the load:

https://www.wholesalesolar.com/solar-information/start-here/offgrid-calculator#applianceTable

Let me know what I'm doing wrong. I'm happy to overestimate as that will give me longer run times in inclement weather.

If it is a new van it will probably have a smart alternator as you are fitting a B2B tthenew ones can be set for smart alternator, have a look at the Votronic ones German made.
In autumn we use around 32 a/h over 24 hours, winter in the UK would probably go up to to 40 - 45 a/h, 147 a/h sounds horrendous and I doubt if it would be suportable.

 

[Abacist]

I am at Vanbitz getting work done on my motorhome. In conversation this morning I was told that a basic van is unlikely to have an alternator of adequate size or capacity. If its got cab air conditioning it will probably be a higher spec than a basic van but evidently Hymers fit 120 Amp Hour alternators and American RV's probably 180 Amp Hours. You had better check yours to see if its up to the job of being worked a lot harder than its used to and change it for a higher spec if required.

 

[DBK]

Diagram updated.

The alternator will be OEM Mercedes Sprinter. No idea if it's smart of not.

Using the load estimate that includes inherent efficiency loss the watt-hours = 1772.

Wh / Volts @12 = 147 Ah. I used this site to calculate the load:

https://www.wholesalesolar.com/solar-information/start-here/offgrid-calculator#applianceTable

Let me know what I'm doing wrong. I'm happy to overestimate as that will give me longer run times in inclement weather.

That link is to a US website and the smallest refrigerator it would accept was 16 cu ft which is probably about 8 times bigger than the typical MH fridge.

It would help if you could list the sort of things which will be drawing power and the folk here should be able to give you a more realistic estimate. For example will it have LED lights? What heating system? A Webasto diesel heater will take more electrical power than a Truma gas one. Are you fitting a three-way fridge which will mostly be running on gas or an electric compressor one? Other things like charging mobile phones, listening to the radio and even the TV will add a small amount but probably not more than a coupe of amps when they are all running - and that won't be all day.
And I think I must point out just once more, B2B chargers are rare things, very few people need them. If you are going to be camped up in the same place for say a week or more in winter then one might be useful. If you are going to be touring and moving every few days you probably don't. If it is a new van check any implications on warranty before fitting.

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[Abacist]

And I think I must point out just once more, B2B chargers are rare things, very few people need them. If you are going to be camped up in the same place for say a week or more in winter then one might be useful. If you are going to be touring and moving every few days you probably don't. If it is a new van check any implications on warranty before fitting.

The B2B works whilst you are driving and is cover for when your solar won't be producing enough like in winter. I never sat in the same place with my van engine running to get the B2B to charge the batteries though I suppose you could if you were in the Alps skiing and the solar was covered in the white stuff. Its also belt and braces so you have 2 meaty methods of charging if one fails with the split charge relay to fall back on and a Battery Master is also sensible. Don't forget that if you run your batteries down too far you are killing them unless its lithium!

 

[NickandClair]

The first thing I see being an issue with the first diagram without the use of a B2B charger is simple, your engine battery restrictions. Most engine batteries are on average 75-95ah and more designed for cranking rather than durability. Connecting a low capacity engine battery to such a high capacity leisure battery in parallel means the larger battery will only ever charge to that of the lower battery, so your proposed single 220AH battery would only ever charge to that of the engine capacity.
Fitting the B2B will do (in layman terms) a bit of gentle manipulation and generate additional power to charge a larger battery capacity at a much higher rate to that of a factory split-charge. Increasing to a larger split charge relay will allow an increased amount of amps to transfer when connected in parallel, but it will not be able to charge a battery with a higher capacity to that of the engine battery (i.e a 110ah leisure battery will only ever charge at 95ah, if the engine battery is rated at 95ah). The B2B's trickery will take the connected leisure battery to it's full capacity through this "manipulation" of the alternator.
As Abacist mentioned previous, it is also safer to restrict the amps transfer so that you are not taking all the available power from the alternator, as you will still need to support equipment that the engine/ancillaries needs and not take all the energy away to charge the leisure battery. Its normally good practice not to exceed 2/3rds of the alternator's output.
If your van has Smart Alternator or Regenerative Braking (common on Euro 6 vehicles), it is pretty important to consider some form of DC to DC or B2B charging, so that the leisure battery's levels aren't compromised being connected to the engine battery in parallel. We have noticed that a few Euro 6 Hymer MLT/MLI Mercedes have been coming through with DC-DC chargers fitted at the Factory, so some motorcaravan manufacturers are realising that the Euro 6 technology does effect the leisure power when on the move. B2B's are also needed when considering the use of Lithium, so that the voltage is a constant input, rather than the big variations that a Euro 6 Alternator will produce.

 

[Red_48]

I was considering a shore cable with integrated RCD. The onboard AC circuit would then have a breaker, hence the RDC is before the AC plug. Not being familiar with circuit diagrams I'm not sure how to represent the RCD, but it looks as though the RDC sits across both positive and negative, correct?.

I added the battery-to-battery charger to the design a few days ago. Other than the suggestion to explore a Votronic unit does the current design look ok?

I don't have the vehicle yet so I can't speak to whether it has a "smart alternator" but it sounds like an uprated unit might be necessary.

The leisure battery is 250Ah, not 220Ah.

The plan will be to "free camp" in all European conditions. Summer heat, winter cold.

The list of appliances requiring 12v power (including the fridge) are listed in the load estimate posted.

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[Red_48]

Diagram updated with inline RDC per

 

[Red_48]

I'm clearly over estimating the load.

It seems to be more common to see appliances listed in watts, or watts per hour to be more accurate.

You can see the calculator factors qty, and runtime to arrive at a daily watts consumption.

Then I converted watts per hour to amp hours. Did I over estimate the appliance loads or just get the math wrong?

 

[NickandClair]

I would have suggested an RCD with also 2 MCB's, 1x for the mains charger and 1x for the sockets. That way if you need to, you can isolate the input to the mains charger. If you decided to go with any combi heater/boiler or your fridge has ac input, this can also be isolated if you have the use of individual MCB's. It is also important as Scotjimland said in having the RCD post input to the van.

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[DBK]

I'm clearly over estimating the load.

It seems to be more common to see appliances listed in watts, or watts per hour to be more accurate.

You can see the calculator factors qty, and runtime to arrive at a daily watts consumption.

Then I converted watts per hour to amp hours. Did I over estimate the appliance loads or just get the math wrong?

I think your maths is correct but I believe you have overestimated the total wattage figure. A very quick Google suggests a MacBookPro will take around 20W unless it is doing a lot of CPU heavy stuff. I'm not sure what a Cbook is but worth checking again. Just because something has say a 1.5A adaptor it doesn't mean it will take 1.5A other than perhaps for a short while when starting up.
When I saw the hair dryer running for an hour I thought that was a bit over the top but then I saw it is a 12v one so might be correct!
You might like to consider adding an inverter into the mix to give you 240v. This is not for things which can run on 12v but for things which work much better on 240v and one of those is a hairdryer. I fitted a 1500W pure sine inverter that cost me about £150 and we use it for hairdryer, Nespresso machine and charging electric toothbrushes - for which pure sine is essential. If you ever get electric bikes these are also much better charged from a 240v supply. The 12v versions, if you can get them, take days apparently.
But I wouldn't over-think the load side as you can't be really sure until you get out and start using the van but as a general observation 300W of solar plus your 250Ah battery seem a very good start. If you do buy a B2B charger as well then you are never going to be left without power.
And do add some instrumentation otherwise you won't know what is happening. One of these is quite good or the UK made NASA BM1 in standard or compact form will do the job.

 

[Red_48]

Thanks guys. I'll look into adding a breaker before the charger and sockets.

I'll sharpen my pencil on the load calc and I hope it'll buy me more capacity.

As for instrumentation, are the Bluetooth interfaces on both solar and AC chargers considered insufficient?

 

[Abacist]

As for instrumentation, are the Bluetooth interfaces on both solar and AC chargers considered insufficient?

Whilst its interesting to know that the solar and charger are working and what they are producing but surely its more important to know how full or empty the batteries are as that is where your power is coming from.

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[Red_48]

Abacist
The VictronConnect App from the manufacturer appears to be quite granular in terms of data provided. And as both AC Charger and Solar Charger have individual Bluetooth interfaces I should be able to monitor the battery from two perspectives also giving redundancy.

I attached a few screenshots of the battery monitor interface. Would this suffice?

https://www.victronenergy.com/live/_media/victronconnect:vc4_iphone_discovery.png

https://www.victronenergy.com/live/_media/victronconnect:vc4_iphone_bmv_live.png

https://www.victronenergy.com/live/_media/victronconnect:vc4_iphone_bmv_settings.png

https://www.victronenergy.com/live/_media/victronconnect:vc4_iphone_bmv_alarm.png

https://www.victronenergy.com/live/_media/victronconnect:vc4_iphone_bmv_batterysettings.png

https://www.victronenergy.com/live/_media/victronconnect:vc4_iphone_bmv_history.png