How much battery capacity and solar do you need?

TonyL

Active member
Pro
So on previous vans I have had at least 200w of solar and loads of battery capacity (no lithium in the old days)

My current van came with 100w solar and around 85 Ah of useable battery storage (AGM batteries), an upgrade is on the cards.But I was intrigued to see how long the van could survive off grid. Well I am surprised. Currently on the east coast, temperature is 10deg C during the day (but sunny) and cold at night. With the heating on (diesel) and a compressor fridge the van is coping well without a hook up. Batteries are always fully charged during the day and are reading 12.5v first thing in the morning. The system is basic so I can't see what the solar is doing apart from whether it is charging.

I am sure that in different circumstances it would be different - very cold with minimal solar, or perhaps hot with the fridge running a lot more.

So what have you got and how does it cope?
 
It’s surprising how you can manage with little power 👍
As you allude though, outside of the summer months, topping up the solar can be sluggish.


Everything on our van is 12v, we do have additional mains sockets for when hooked up but we have only used them once as we off grid all the time.

Roof has 360 solar and we replaced our 2 yr old failing 320 Ahr AGM batteries with a ‘drop in’ 230 lithium replacement from Roamer.

Roamer were brilliant, with fab customer service, and talked me through making sure my settings were correct.

Oven and hob are gas, and we run a Truma 4e and a compressor fridge. All lights are LED.

We manage 6-7 days totally off grid until the loo/ water tanks needs sorting.


Life is very good, we love our Crafter
 
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Without a shunt battery monitor I doubt you are getting fully charged every day. Voltage can be misleading and with one compressor fridge I think you are running in deficit. It won’t show yet as you got new health batteries. With one 100w solar it’s impossible to run a compressor. Only in middle of summer 2-3 months tops.
A compressor takes about 0.3kwh per day. That’s 25ah at 12v, plus inefficiencies, other loads etc. So you need to harvest daily in excess of 30-35ah and have those batteries in float by 2-3pm at least.
We have 600w on the roof, and 230w portable with a 400 lithium bank. In winter we do not cope with our consumption, and we need to plug in at least once a week. We run one compressor fridge in winter, and a additional freezer in the summer. We use gas in winter, and solar in the summer for most things. Heating is done by diesel.
 
Try to get a victron bmv, battery monitor. It will count everything going in and out of the battery. It will help you keep track of your energy, it will spot problems before they arise, and will help you manage energy efficiently and very accurate. Even if it’s a simple system, it’s a great add on, and it’s future proof for any eventual upgrades.
 
Hi Tony.
I’ve a 3 x 100amp battery set up…..why 3? Because if one battery was to go down, and they can, I have the other two to carry on , providing the power (re jig the cables etc). Relying on one battery for the power source is fine, but being a realist modern technology can fail at any time.
The solar array is max output of 480watts.. so having a 2000watt inverter this will heat up the 10l hot water tank in 45 mins from cold to 56/57*c. Recovery is a couple of hours to 13.5v or so.
On average, the battery doesn’t get much lower than 13.2 v, except when heating the hot water , then it goes 12.8v.
 
It is maths. Had a quick look at the match’s and built myself a spreadsheet this afternoon.

You can’t beat a good spreadsheet
 
I would like to recommend this amazing battery. It has been developed and designed by a friend of mine from Germany.
His name is Pascal and he is a man of absolutely amazing knowledge and skillset.

Below is an example of his recently installed battery and a link to his website.

IMG-20230525-WA0017.jpg

 
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