backchannel: how much power do I need in my van?
Some input on this blog article, mentioned in this tweet.
> solar is relatively inefficient in keeping up with the demands put on your electrical system by a full setup
It’s not inefficient, it’s expensive for the amount of power produced.
> in the base package of every van we build we include a 200ah AGM battery along with a 160 watt solar panel.
Undersized panel by any measure, not even up to the 1:1 W:Ah rule of thumb minimum. 200-300w of panel into a 20A MPPT would be better for that setup, and the controller setpoints need to match the battery manufacturer’s specifications.
It’s not that big a deal, given that alternator charging is also present (see below), but it’s disingenuous to undersize the solar install then blame it for not being able to make a heavy lift.
> most charge controllers only truly operate around 60%-70% efficiency.
Controllers are quite efficient. I think you are conflating “efficiency” with the yield PWM are able to extract from the panels on average (judging from the pic of the PWM controller in that picture). The 60-70% figure has to do with
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temperature derating
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local insolation, etc.
MPPT are typically 95% efficient (less than PWM due to the DC-DC conversion) although they have higher yields due to their getting away from the Vbatt == Vpanel problem.
solar is NOT an effective way to keep your batteries charged by itself. It is great as an auxiliary source of power, particular in the summer months, but it will never be enough by itself to keep up. Especially if you’re attempting to live out of your van full time.
Bold claim. My van (offgrid for about 1.5 years on solar power) begs to differ. If you want to run solar only you just have to set the van up for that.
> There are two main[battery] types you’ll see in Camper Vans, AGM and Lithium-Ion
There are more flooded batteries than AGM or Li in campers combined, I’d wager. Half the price of AGM and doesn’t require as much current to stay healthy.
> These batteries will typically run you about $400
220Ah+ of golf cart battery (2x 6v in series) is a little over $200. That’s as close to a standard as one finds offgrid.
> The best way to charge your batteries is to get a smart isolator
What do you mean by “smart”? Voltage sensing? DC-DC converting? The former, judging from the $100 you mention for them.
I agree that alternator + solar charging can be optimal offgrid.
> Solar is obviously a helpful thing to have if you’re parked for a while
Solar works even if you are driving around. The two forms of charging will work together.
> massive solar setup or very large battery bank, but those two things are very expensive
Large/high voltage panels are pretty cheap, typically under 75c/w if you get them locally off a pallet. And flooded GC batts are 1/2 the cost of AGM and 1/5th the cost of lithium.