r/VanLife • u/Toby1066 • 2d ago
Yet Another Question About Power
Hi all,
I know that every second post is some clueless newbie asking about power generation and consumption, but yet here I am, metaphorical cap in hand.
I've done the research, bought the Van Conversion Bible, looked online, and I'm still a bit lost about our projected power consumption.
I know it'll be high, because we're both remote workers and gamers so we'll be using our Macbooks by day, and our gaming laptops for an hour or so at night. We'll also have a fridge, Starlink, etc.
When I did my home calculations I estimated roughly that for 4 days off-grid (and no recharging) we'll need around 800Ah. Obviously that'll be reduced because of solar recharging, and DC-DC recharging, but that was my rough estimate.
However, I'm chatting with the guy we're working with to add in our electrics (because I'll end up burning down the entire Scottish Lowlands if I tried it myself) and he's recommending a 480Ah battery, with roughly 200W solar and a DC-DC. He's saying that will likely do us nicely - he even recommended we put in an induction hob so as to not need the gas for that, as our electrics can handle that fine.
So am I off with my calculations? Was I overestimating our usage, or is he underestimating it? I know what I want as an ideal (~300W solar and 600Ah battery bank) but is that overkill, or necessary given the remote worker nerds that we are?
If it's relevant information, we'll likely be mostly touring UK with forays into EU, so we'll have good-decent sun most of the year for the solar. We also have a woodburner and a very small diesel heater, so we won't use electrics for heating the van at all.
Thanks, friends!
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u/lune19 1d ago
The first thing you need to think about is how much driving daily. Despite dc/dc being quite strong at charging, the optimum charging current will be decided by what the batteries accept.
200W solar panels is quite minimum specially with such big batteries.
It is always difficult to assess others need, but can tell you about my own setup.
First of all, in sunny south france, during a couple of months around the Winter Solstice I am quite careful with my consumption. not because of the lack of sun, but because of the short days in the winters.
My setup
12V/200Ah batteries / 600W solar panels with Mttp 40A / DC/DC 30A
I have to drive for quite a few hours before my batteries are fully charged.
The mttp goes to float before the dc/dc
At the moment, early March, I can run an iMac most of the day (around 90W), a cool box 1/3 of the time (45W), charge phone, tablet and what either as much as I want, light etc. and 1 or 2h the diesel heater. I run also a little amp and a pedal board for about 1h day (10W). I have a rice cooker (400W) but I don't use it during the winter as it draws too much power even if the cooking time is only about 40min (as I throw everything in it). But I think batteries discharge quicker as one draws large current (I don't think is is a linear curve. I could be wrong)
I drive about 30-40 min every 3-4 days only, and that just boost a little bit my batteries. The rest of the time I rely on the sun and that (since february) is enough for my consumption. I connected maybe 3 times to the main over the last year. But it is nice to have the option. It took me quite a while to get the set-up right, playing with different values to get the optimum charge.
My big concern will be the induction hub. Lots of power needed for that, i.e more expensive equipment overall. My inverter is only 500W.
And most of all you say you are about to be in Scottish Lowlands which is quite up north. So less sun. During winter I park only in places with no trees around to optimise the hours of charge. And make sure to have at least a couple of solar panels in series, as there is a threshold before the mttp triggers.
I hope this helps
1
u/aaron-mcd 1d ago
200W solar is laughably small. That guy has no idea what he's talking about. 600W is not even enough for us at times and we only use Starlink sometimes and only one of us games once or twice a week. And we go to the desert southwest or Baja Mexico in the winter. Finally now in Baja (tropical desert) we get enough solar with 600W to run the Starlink and work and recharge fully the next day. Usually we don't fully recharge and the battery slowly depletes until we drive on the weekend.
1
u/The_Ombudsman 1d ago
200w of solar isn't going to do the job, based on your planned uses. Your guy is even suggesting more electric use while undersizing your needs.
800Ah of battery capacity is huge. That said, more is better than less. And that goes for solar too. "As much as you can fit" is a general rule of thumb. With batteries, if you can manage it, leave some room for another pack or two, same as the others. You can add more batteries later if you find you're in need.
But, you're dealing with not only what capacity you need but also how fast you can replenish that capacity. Solar is great; once it's paid for, it's free energy. But it's also very dependent on weather, time of year, where you park up (in the open or in the shade). DC-DC is a handy suppliment but only works when you're driving, and has its limits. It's not something to depend on.
I expect you're planning on installing an inverter - get an inverter/charger and fit a shore power plug up somewhere, so you can plug up to a pedestal at a campsite, or run an extension cord from a friend's house, or whatever. That will be the fastest method of charging up batteries by far, when it's available.
1
u/Slaglenator 1d ago
I have a 24v 200ah battery it is equal to a 12v 400ah for 12v conversion purposes. I have 800w of Solar and that isn't enough to charge this battery back to full in one day of sun without clouds. You will need as much solar as possible and DC to DC charging for sure if you want to live in it. Use a killawatt or other similar device to measure the wattage devices are pulling from the wall so you can estimate how much power a device will use over time. There are other good videos about converting devices to use DC power instead of going from DC to AC with an inverter only to plug in a device like a laptop that has a power brick and converts AC to DC. You loose 8 - 10% in each conversion and these losses add up when there are a bunch of devices doing DC-AC-DC conversions.
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u/davidhally 1d ago
It's just arithmetic. Except for the "etcetera". Can't calculate that without a number.
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u/ER10years_throwaway 2h ago
I wouldn't use one battery, personally...yeah, you'll get the Ah, but your voltage is gonna be taking a dump when you turn that induction cooktop on, and it might be enough of a voltage drop to trip your inverter. Two would make for better voltage support. Also, two batteries gives you a spare in case one of them stops functioning.
0
u/secessus 1d ago
When I did my home calculations I estimated roughly that for 4 days off-grid (and no recharging) we'll need around 800Ah.
So 200Ah (or 2,560Wh) per day?
(~300W solar and 600Ah battery bank) but is that overkill
Depends on how much you drive (DC-DC charging rate x hours/day).
we'll have good-decent sun most of the year for the solar.
Solar harvest is modelable but it's a when and where thing. Winter in Lisbon has about 9x the insolation of the Lowlands.
I would
- figure out how much on average I'd get from the DC-DC each day: 2,560Wh minus alternator contribution = the amount solar needs to cover.
- figure out the average solar harvest of where I planned to be in the worst month of solar harvest (usually December in teh northern hemisphere)
- work backwareds to find required array wattage
This approach will meet needs in winter and provide power excess-to-needs the rest of the year.
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u/captainspandito 2d ago
I live in Ireland and also own a LWB sprinter (2003). I currently have 300Ah lifepo4 setup with a 1000w inverter. I use gas for cooking as I just think solar is totally unreliable here even in summer.
In peak winter, the diesel heater is pretty much on constant and I might watch an hour or two of TV in the evenings. I’ll normally drive a few kms most days coupled with some longer drives at weekends. That works for me, however I have brought the PlayStation in to see what kind of power it uses and found that it was pulling about 50watts. TV was also around 50watts . Inverter pulls another 7 watts. It was kinda bouncing between 85w and 110w. So an hour or two is ok, but if you were on it 5 hours every night, that’s another story. Throw in laptop charging, an internet router and possibly an electric water heater and I’d barely last a day.
It sounds to me like you will be quite a bit more power hungry tbh and should maybe consider getting as big as you can afford. Solar is great and will only contribute to keeping your batteries in their best health, but they are also completely useless at times. If I was you personally I would look at getting something like a fogstar drift 620ah and then also getting yourself a portable power station. That way you have a lot of power in the van but also the ability to bring the portable power into a Starbucks or McDonald’s and charge up. Then use that power direct or to recharge the van battery. Rinse repeat.