Solar/charge system

[NM]

I'm not an electrician and am in the dangerous position of having done a great deal of internet research and thinking I can design a DIY system for the van. I would appreciate it if a few who do know what they are doing could cast an eye over what I think is the right solution.

The van is a 2019 Euro 6 sprinter with smart alternator. The plan is to be completely off grid and never to need to hook up, all the power we need coming from Solar or the DC-DC charge from the alternator. We will be on the move much of the time, not planning on staying in one place longer than a couple of days. With everything on we will be drawing about 100Ah per day. To get 2 days use in Scotland when it's tipping down we need a usable 200Ah. I'm keen to go Lithium to minimise weight so need 250Ah plus. On those occasions when we do get a bit of sun I want to make the most of it so plan 3 x 175W panels on the roof which with roof mounted awnings, two ceiling vents and a roof rack is about all I have room for. This should give about 40A of charge so 2.5 hrs goo sunshine or equivalent is enough to put back in a days usage. The DC-DC charger is going to take about 3.5 hours of driving to put a day's charge back in which I would like to reduce, but I don't think you should take much more than 30A off a Merc alternator. With any luck the combined force of the DC-DC plus the Solar should keep us out of trouble. If not we will just have to manage our power usage.

I want to use Victron kit as have used it on various boats and I have faith in its reliability. So I have designed the attached. My biggest worry is how to wire it all together, what wire size to use where and what size fuses to use.

If someone could advise where they believe I have gone wrong and put me right I would be very grateful.

 

[funflair]

It all looks quite doable, we have the same Solar regulator and it has 16mm2 cables which is the max that the terminals will take and fused at 50A from memory. If your budget will run to it I would be tempted to stick a bit more LiFePO4 in just in case.

 

[NM]

Thank you Martin. Much appreciated. I had been thinking 16mm2 for all but the main battery cables which I would size at 20mm2.

 

[cmcardle75]

I was doing similar calculations, although we use less than 100Ah a day, even with the compressor fridge. I'd say we can go 5 days on 300Ah, but we don't have inverters and coffee machines or hairdryers.

However, as we do lots of driving in the UK and often use in winter, we calculated that it was best to sack off the solar and spend the difference on a bigger battery (300Ah). A lot less work to install, too, and better for fuel economy and stealth mode.

If you're a drive to the Med, park up and sit on the beach type, it would be a completely different matter and solar is a good choice.

 

[NM]

I was doing similar calculations, although we use less than 100Ah a day, even with the compressor fridge. I'd say we can go 5 days on 300Ah, but we don't have inverters and coffee machines or hairdryers.

However, as we do lots of driving in the UK and often use in winter, we calculated that it was best to sack off the solar and spend the difference on a bigger battery (300Ah). A lot less work to install, too, and better for fuel economy and stealth mode.

If you're a drive to the Med, park up and sit on the beach type, it would be a completely different matter and solar is a good choice.

The OffGridVan.Life battery is 280Ah, so not far what you have. I think we will be mainly summer touring and will be as far north as Norway and as far south as Italy so I think solar is the way to go for us, but with the back up of DC-DC and a decent battery bank for when the weather is not so flash. The solar install itself (panels and controller) is going to add £1k to the build but I think it will be worth it.

I think the biggest limiting factor to time off grid will be the water capacity, but that's another issue.

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[cmcardle75]

The OffGridVan.Life battery is 280Ah, so not far what you have. I think we will be mainly summer touring and will be as far north as Norway and as far south as Italy so I think solar is the way to go for us, but with the back up of DC-DC and a decent battery bank for when the weather is not so flash. The solar install itself (panels and controller) is going to add £1k to the build but I think it will be worth it.

The difference was that we decided the B2B would be primary, given we can go 5 days without charging, but never actually would. In reality, we're usually at 100% every evening, as just an hour or two of driving is enough to top off that day's usage, and that would be below our average driving. After crunching the numbers, we decided that we'd never actually need the solar (although I admit I have got an uber-cheap 100W poly panel stashed onboard (not mounted) that can be used if required, which was actually enough to keep up in summer conditions when I had to park for 2 weeks for a scout camp).

I think the biggest limiting factor to time off grid will be the water capacity, but that's another issue.

That's why I went for the 210 litre tank!

 

[paddymcc]

I would have thought that the Merc alternator could cope with more than 30A.
Make sure your breakers are good quality or use a fuse. I've heard of poor quality ones having poor contacts that overheat.

 

[mitzimad]

Use a fuse rather than a circuit breaker many are prone to failure i always buy a spare fuse and tape it to a cable close by

 

[NM]

The difference was that we decided the B2B would be primary, given we can go 5 days without charging, but never actually would. In reality, we're usually at 100% every evening, as just an hour or two of driving is enough to top off that day's usage, and that would be below our average driving. After crunching the numbers, we decided that we'd never actually need the solar (although I admit I have got an uber-cheap 100W poly panel stashed onboard (not mounted) that can be used if required, which was actually enough to keep up in summer conditions when I had to park for 2 weeks for a scout camp).



That's why I went for the 210 litre tank!

All very interesting. It's this sort of feedback that makes this forum so good.

Could you tell me what make and size of B2B charger you have fitted and where on a Sprinter do you store 210 litres of water? The best I can do at the moment, without taking up garage space, is to fit a 170L tanks in place of the spare wheel under the back of the vehicle. Too far back for my liking really but at least it's low.

 

[cyberyacht]

It might be worthwhile putting an isolator between the panels and your controller in case you need to disconnect anything in the system at some stage.

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[cmcardle75]

All very interesting. It's this sort of feedback that makes this forum so good.

Could you tell me what make and size of B2B charger you have fitted and where on a Sprinter do you store 210 litres of water? The best I can do at the moment, without taking up garage space, is to fit a 170L tanks in place of the spare wheel under the back of the vehicle. Too far back for my liking really but at least it's low.

I've just got a 30A Victron Orion for the B2B. The van is a L3H3 Vauxhall Movano. The layout is a fixed double bed. There is no garage. That leaves space underneath the bed for the 210 litre water tank, a large waste tank, the compressor fridge, water heater and lots of storage for tents/BBQs/chairs etc. The advantage of this is that the tanks are inside the insulated envelope, so it is winterised without any specific tank heating.

 

[graham39]

I'm not an electrician and am in the dangerous position of having done a great deal of internet research and thinking I can design a DIY system for the van. I would appreciate it if a few who do know what they are doing could cast an eye over what I think is the right solution.

The van is a 2019 Euro 6 sprinter with smart alternator. The plan is to be completely off grid and never to need to hook up, all the power we need coming from Solar or the DC-DC charge from the alternator. We will be on the move much of the time, not planning on staying in one place longer than a couple of days. With everything on we will be drawing about 100Ah per day. To get 2 days use in Scotland when it's tipping down we need a usable 200Ah. I'm keen to go Lithium to minimise weight so need 250Ah plus. On those occasions when we do get a bit of sun I want to make the most of it so plan 3 x 175W panels on the roof which with roof mounted awnings, two ceiling vents and a roof rack is about all I have room for. This should give about 40A of charge so 2.5 hrs goo sunshine or equivalent is enough to put back in a days usage. The DC-DC charger is going to take about 3.5 hours of driving to put a day's charge back in which I would like to reduce, but I don't think you should take much more than 30A off a Merc alternator. With any luck the combined force of the DC-DC plus the Solar should keep us out of trouble. If not we will just have to manage our power usage.

I want to use Victron kit as have used it on various boats and I have faith in its reliability. So I have designed the attached. My biggest worry is how to wire it all together, what wire size to use where and what size fuses to use.

If someone could advise where they believe I have gone wrong and put me right I would be very grateful.View attachment 600987

Hi i have 3 off 300 watt panels through an epever system set at 40 amp breaker wired with 4 mm at yhe battery terminals andcstandard 6 mm from the solar panels in reasonable sunshine my two 135 amp batteries power the big fridge all day all the lights power for my diesel heater at night a two cup kettle and bursts on the 800 watt microwave delivered by a 6000 watt /4000 watt inverter bought from halfords i use the van from April to September you need 4 hrs of sunshine to use this system properly dull days i just dont use the microwave but i have Can oven and hob on gas as well hope this helps someone