backchannel: solar FUD

I left a comment on this video. It was a response to this exchange:

[commenter] Why should I continue to watch any video that just outright lies about solar panels, within the first minute of so, just to try to make this product look better

[video creator] State the part you disagree with. And let’s discuss

My response is below. Quoted parts are from statements made in the video, as accurately as I could transcribe the video.

---

@RCReviewChannel Good video, especially the lessons learned part.¹ I’m not the original commenter but I have some idea what some of his objections might be. I do think his wording was needlessly harsh.

Full disclosure: I charge my bank with both solar and alternator, since each charging method has both strengths and weaknesses.

If you use your solar panels they’re very expensive and very slow

Are they? The flat-mounted array on my rig cost $234 and is making 439w at this moment, well past local solar noon. I woke up late (overslept after binge-watching a series last night) – when I finally did wake up the solar setup was silently and autonomously recharging the bank. No buttons to push, no action to take. It’ll also work when I’m out on a hike or reprovisioning in a grocery store.

Actual example: at this location in November I’ve been using 1.47kWh/day so that’s what solar has harvested. When I put the spurs to it it’s been maxxing ~2.8kWh/day at this time+place. To get that average harvest with an 800w DC-DC I’d need to run the engine almost 2 hours each day. To match maximal November harvest would require running the engine 3 1/2 hours each day.

Is one better than the other? No. If I was a delivery driver or overlander I would use the alternator to do the heavy lifting. If I were a boondocking off-grid full-time (I am) I’d make solar the centerpiece (I do). Horses for courses.

in a lot of shade you’ll have to reposition them

Stipulating shaded conditions for solar is like stipulating DC-DC output when the engine is off. It’s not how either one is intended to be used.

But since we are stipulating shade I assume the DC-DC box is being used at idle under the same shade. Anyone charging with 800w (plus buck/boost losses) at idle better know what they’re doing.

” and “you’ll be lucky to get a couple hundred watts out of it”.

Peak watt harvest isn’t particularly important, other than in sizing a solar charge controller. Watt-hours of total harvest is what’s important in recharging any depleted bank.

800w. It’s amazing. Most grid chargers don’t go that fast. .

There’s a reason why quick-charging LiFePO4 isn’t the default behavior: charge rates (expressed as a fraction of C, the bank’s capacity) strongly affect LiFEPO4 degradation. Assuming the manufacturer of one’s power station publishes info on the cells they use (unlikely) you can look up the cell manufacturer’s data sheets and see what charging rates are recommended/allowed for the cells at given SoC and cell temp.

1. from the auto-generated summary, “two key lessons learned during the installation, including the need to turn on the charger using the app and the ability to daisy chain power stations for extended charging.” ↩