Should I bother with a 12 to 24v B2B charger with 400W solar exposed while driving?

[Justdeansd]

I have very limited real estate on my roof, just enough for 2 200w panels so I'm stacking 2 others underneath to pull out when parked. In the past I have spent my travels with no more than 2 days in one location, but that was without solar and I think I will spend more time parked now. So I already spent the $271 for the charger but I think I might be okay with the batteries charging without the B2B since I will have 400W exposed. I have 2 12v 100Ah LiPo batteries wired in series. My travels vary but it's usually in the winter in the mid to southern hemisphere.

Should the batteries be charged with 4 to 5 hours driving with 400W then the rest of the day with 800W? I can still return the charger at this time.

 

[sunshine_eggo]

So you went from 0W solar to now having 800W solar when parked and 400W solar when driving?

Opposite hemisphere production on a flat roof is about 40% of rated.

My gut says you probably won't need it, but I'm voting "probably best" just because it's probably a small cost in the grand scheme of things, and having a reasonable backup is never a bad idea.

 

[ianganderton]

You don’t say where you are. This is an important piece of the puzzle.
Summer with solar is easy, it’s ensuring you can replace back into the battery energy used in winter that’s the challenge.

 

[fratermus]

I think I might be okay with the batteries charging without the B2B since I will have 400W exposed

I have ~twice the solar mounted, half the battery capacity, stay in place in 14d stretches, and still am grateful for alternator assist.

Most of the time it's because I'm relocating after several days of crappy sun. Before I take off I set every rechargeable thing on it's charger in order to get the most of the alternator's contribution. Sometimes I set up a crockpot or rice cooker in the sink so dinner will be ready after the drive. A more extreme example is when I was trapped on the coast by Oregon wildfires and in the haze my array was harvesting only 1.5% (!) of rated power at local solar noon. D'oh! For a few weeks I was surviving off mainly alternator charging.

My system is 12v so I'm doing it with a $60 VSR. The cost/benefit analysis might be different for your use case.

the rest of the day with 800W?

If this means 400w mounted + 400w portable, IME alternator charging is much easier (ie, automatic) than deploying/picking up portables. I carry 200w of portables and it's such a PITA I only deploy them when desperate.

 

[Justdeansd]

You don’t say where you are. This is an important piece of the puzzle.
Summer with solar is easy, it’s ensuring you can replace back into the battery energy used in winter that’s the challenge.

My mistake, I meant to say the southern part of the US. I'd like to visit the southern hemisphere again. I was last there in 1989 when the USS Ranger CV-61 pulled into Perth for a week. I should have spent my time more wisely so I would have seen and remembered more of the city.

 

[Justdeansd]

I have ~twice the solar mounted, half the battery capacity, stay in place in 14d stretches, and still am grateful for alternator assist.

Most of the time it's because I'm relocating after several days of crappy sun. Before I take off I set every rechargeable thing on it's charger in order to get the most of the alternator's contribution. Sometimes I set up a crockpot or rice cooker in the sink so dinner will be ready after the drive. A more extreme example is when I was trapped on the coast by Oregon wildfires and in the haze my array was harvesting only 1.5% (!) of rated power at local solar noon. D'oh! For a few weeks I was surviving off mainly alternator charging.

My system is 12v so I'm doing it with a $60 VSR. The cost/benefit analysis might be different for your use case.



If this means 400w mounted + 400w portable, IME alternator charging is much easier (ie, automatic) than deploying/picking up portables. I carry 200w of portables and it's such a PITA I only deploy them when desperate.

I appreciate your contribution in helping me figure this out, it sounds like a convincing case of why I should go ahead and install it. Especially since I live in Northern Ca where wildfires are almost as common as a change in the weather. We were evacuated 18 days for the Dixie fire and the hook-ups cost a fortune.

By deployable I mean remote controlled. Right now I am building my system which is a total of 4 200w panels with 2 exposed while driving then when I park I can hit the remote control to case the other two to slide out from underneath the top two. Very limited roof space with the vents, AC, skylight, ladder and satellite dish, so I have to get creative. I spent months trying to figure out how to design it. Only few on Youtube and none of them documented exactly how they built and mounted everything. But I learned enough that I was able to fill in the blanks. Now I am vlogging it in detail to help those who have the same problem.