Roof with some solar and a opening hatch or solar only ?

B85

Adventurer
Have a roof that I can put 5 x 300 watt panels or have a hatch to the roof but only have for 4 x 300 watt panels.
That would you do ? I know that more is better but ?
This is a 24 volt system.
Thanks,Randy
 

shade

Well-known member
Have a roof that I can put 5 x 300 watt panels or have a hatch to the roof but only have for 4 x 300 watt panels.
That would you do ? I know that more is better but ?
This is a 24 volt system.
Thanks,Randy
Depends on your loads, but if you plan to spend time in the American Southwest, sun is usually abundant, as well as heat. I'd probably go for a little less solar and more ventilation. To make up the difference, you may source more efficient panels: 4x360 is almost 5x300.
 
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Joe917

Explorer
We have 2X315 Watt panels, a hatch and 3 fantastic fans in our roof.
We are (almost) never short of power, 12v full size fridge, lights, computers etc.
The hatch allows roof access without an external ladder. (11'6")
 

luthj

Engineer In Residence
You need to do an electrical system usage/charging budget. You may only need a few panels. I suggest doing it all in watt-hours, as the combination of a 24V system and likely some 12V appliances make AH more complicated (and error prone) for calculations.

Last I checked there were a few ultra low profile roof vents that may fit under a solar panel. May be worth a look.
 
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Peter_n_Margaret

Adventurer
You can not have too much solar and it is not the good days that decide how much would be useful.
There are other ways to get on the roof or provide ventilation.
Maximise the solar!
Cheers,
Peter
OKA196 motorhome
 
I full time in my truck camper which is equipped with (2) 320 watt solar panels, (2) vents, (1) fantastic fan, and a huge sky light that opens. I also carry a Honda generator which I've never used. I camp in all types of weather.

My previous truck camper which I had for 13 years and used on average (6) months per year had identical solar, (2) vents, and (1) fantastic fan. It had a built in propane generator which I almost never used. Most hours on it were just running it monthly to keep it fit.

The biggest issue I have is condensation.....not lack of power. Condensation sucks in extended foul weather. It was huge in my decision recently to move south.

I'm certainly not qualified to know how to answer your question but my real life experiences say that maybe you meet in the middle, get (3) solar panels (if that's a big concern) and not forgo the vents.
 

B85

Adventurer
Thanks for the ideas and input. I have a Honda 2K to add power when needed.

Anybody using the Tesla battery packs ? Been thinking about them.
 

rayra

Expedition Leader
I'd rig the panel over the hatch with some pivots on the trailing edge and a couple springloaded locking pins in a frame on the leading edge with a coated wire between the pins. So if I have to open the hatch I do and pull the cable to swing that 5th panel up and over onto the 4th, clear of the hatch.

but then again I like building custom stuff ;)

solarpanelmount85 installed.jpg
 
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luthj

Engineer In Residence
Tesla packs are not nearly as safe as LFP. I personally would not do a DIY pack in a location where I sleep at this point. Now as the DIY tesla specific BMS systems get more users/time that may change.
 

shade

Well-known member
Tesla packs are not nearly as safe as LFP. I personally would not do a DIY pack in a location where I sleep at this point. Now as the DIY tesla specific BMS systems get more users/time that may change.

Adding to what he said, Tesla uses LiNiMnCoO2 (NMC) batteries; I'd stick with LFP for a house battery. Punctured LFP batteries result in boring YouTube videos, but NMC batteries are more exciting.



I think it's worth noting that Tesla vehicles have firewalled battery compartments to limit the potential for thermal runaway. If those packs are used to construct a house battery, they may lack that protection.
 
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B85

Adventurer
Thanks. Maybe I will go back to the Blue battery's ?
Anybody know what gas is given off from the nail test ?
 

luthj

Engineer In Residence
That puncture test is showing vaporized and venting electrolyte. The electrolyte is flammable in LFP (just not nearly as much as the NMC chemistry). The temperatures produced during a failure event like that are also much lower.

That electrolyte is pretty nasty stuff when vaporized, so you won't want to breathe it. The important thing, is even a catastrophic failure doesn't produce fire (typically).

LFP prismatics are the best option for building your own lithium battery pack. There are also drop-ins if you prefer to reduce the challenges of building and implementing your own BMS,
 

shade

Well-known member
There's a lot to learn about using LFP batteries. Here's a good starting point: https://marinehowto.com/lifepo4-batteries-on-boats/

The main point of that article is that an LFP battery installation is best approached as a system. Just installing an LFP battery into an existing system that was designed around charging lead batteries won't go well.

I've been slowly working my way through building a system with off-the-shelf parts, mainly from Victron Energy. Being new to LFP, I decided it was wiser for me to go that route than DIY, but there are good reasons for a DIY approach. Typically, you can get more battery capacity for the money, and you can tailor the control system to do exactly what you want. I'd guess I'm spending roughly $1000 more for my system than I would if I pieced together a battery management system and individual LFP cells, but I'll (hopefully) gain a system that has already been designed & tested to work well together.

I have much more to learn, and I've enjoyed the experience, but it's not simple or cheap.
 

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