~100kwh for 24/7 off grid home

[tanoshimini]

I saw a video of some guy in Northern Vermont that uses a seedling mat to heat his bank. He has a wooden box enclosure with 2" of blue board. He has it rigged to turn on automatically, and it draws about 500wh per day.

That’s a variation on the same theme I’m looking into: Basically some sort of resistive silicone heating mat. @Will Prowse recently did a video on some reasonably priced ones, designed to heat waste-water tanks in RVs and boats. Those shake out to ~$35/ea. and are self-regulating. The ones that are being sold specifically as battery heaters are 2-3x the price, which seems ridiculous. I was looking into these 12v/25w silicone heating mats and thinking of putting 4-5 of them, wedged between pairs of modules. The casings on the modules are steel and should distribute the heat well. I bought a set and will do some tests before doing them all.

I'm curious what draw will be for a metal box and 1" of foam.

I doubled-up the 1” foam, so I have 2” all-around, same as buddy. (I used 1” because it made it easier to fit around some of the internal gusseting in the boxes.) The XPS foam (blue or pink board) has a smidge better R-value than the EPS foam I used, but doesn’t have a radiant barrier. I’m curious to see how well it works out, too.

Also, do you mind me asking where you got these batteries from? I'd like to buy some from a local company as well, but I feel like I'm grasping at straws.

I bought mine from Battery Hookup, which is in Bensalem, PA — ~50mi (~80km) from our current house in Delaware. I could easily take 16 at a time using our little diesel Colorado pickup, and I avoided all of the shipping charges, which would have increased the cost of the pack considerably. They loaded them right into the back with the forklift; super simple.

I’d picked up a 12’ (~4m) tandem-axle utility trailer last month, and then built four of the batteries directly upon it, as I would not be able to move them at all once they’d been assembled. We hauled the first four up to Maine this past weekend, and I was able to pluck them off the trailer with our telehandler (Bobcat V723) and some pallet forks. All of this was theoretical up until that point, but everything went smoothly and I was able to reach in and pluck them all off in under 20 minutes; no drama. I was relieved that I didn’t have to disassemble anything in just to unload them.

 

[Freep]

There's one thing about silicone heating mats that is always in the back of my mind. Most of them have the capability to get very hot. Possibly too hot. Heating pads that can't get hot enough to overheat your cells would be ideal but I haven't come across the right one yet.


You're living the dream, man. I've been thinking about moving off the grid for a long time. When I get my chance I will definitely be learning from you.

Will you be using HomeAssistant as part of your final system?


Edit: I missed a key phrase "self-regulating". It seems like you were also worried about overheating.
I don't see why tank heating pads shouldn't be used. It looks to me like "designed for batteries" is just a marketing premium.

 

[reg]

I bought mine from Battery Hookup, which is in Bensalem, PA — ~50mi (~80km) from our current house in Delaware. I could easily take 16 at a time using our little diesel Colorado pickup, and I avoided all of the shipping charges, which would have increased the cost of the pack considerably. They loaded them right into the back with the forklift; super simple.

I just purchased a battery from Battery Hookup that I'm quite happy with. Seeing as how you've been there, I have a question. How big an operation is it? Is it a storefront operation? A large enterprise? Somewhere in between?

There's a possibility that I'll purchase a good number of batteries from Battery Hookup. It's less than 100mi from me, so like you I'd pick them up.

 

[Ampster]

They’re known to be very price-competitive for pre-built systems, which is why I used them as a baseline for my cost model.

Yes, I agree. I actually had a reservation on two Powerwalls 3 years ago from a third party installer. I cancelled it because I concluded I could DIY one with a better match of the capacity factors I needed. Like you, i wanted more kWh battery capacity but did not need the kW inverter capacity that adding multiple Powerwalls would have meant.

 

[David S]

Just for a point of reference, you might want to check out the Wild, Wonderful Off Grid YouTube channel. The homeowner is an electrician and he just recently completed his very large scale fully off grid build in W Virginia. He followed a somewhat different design pattern to you. Good counterpoint.
Fantastic build, great work so far!

 

[Ampster]

Just for a point of reference, you might want to check out the Wild, Wonderful Off Grid YouTube channel.

Yes, i have enjoyed their videos. He does offer some technical tips especially on the AC 240 volt side of things. I don't remember the batteries he used and he does not get into the nitty gritty of batteries as is done on this forum. That may be because they used SimpliPhi or similar.

 

[mesquito_creek]

Wow... I am super excited to see someone who did something similar. As a "beginner" I was afraid I would be fed to the wolves for doing something similar. I am running an RV fully off grid and I needed something to house the solar components exterior to the RV with a ground mount PV array. I put the inverter and batteries into a Job box. I had to slot the top shelf of the internal job box to allow the top vent on the inverter to vent. I am in southern Utah with very few temperature considerations based on the battery spec, but it will get too cold in the early AM for about 2-3 months. My plan is to just let the BMS charging protection manage that for the few hours its below 32. Every day I have seen at the worst mid 40s after the coldest part of the morning. 50s in more common even in the dead of winter.

The first problem I had was the color of the box. In direct sun It would get very hot upwards of 100+. I painted the box white and now it tracks just a few degrees warmer than ambient temp. I plan on shading the box soon before the summer temps hit.

I have installed 2 temperature controlled 4 inch fans. One as intake and one as exhaust. Time will tell if this works.

I just plug the RV 50 amp plug into the box and it is just like a giant solar battery generator. I do not live full time here, just a few weeks at a time

4000 watt solar arrray, Mpp solar LV6048 and 4 - 48V Hsky 103 ah bigbatteries.

You have inspired me to post and I suppose I can take the bad feedback....

 

[tanoshimini]

Just for a point of reference, you might want to check out the Wild, Wonderful Off Grid YouTube channel. The homeowner is an electrician and he just recently completed his very large scale fully off grid build in W Virginia. He followed a somewhat different design pattern to you. Good counterpoint.
Fantastic build, great work so far!

Yep. I’ve checked in on them from time to time. As I understand it, they’re using brand new LFP 48v batteries from Simpliphi. At ~3.8kWh (and ~$2500) each, their six batteries are going to give them ~23kWh of storage at a cost of roughly $15k. That works out to somewhere in the $650-700/kWh range. My setup works out to ~1/6th the cost, including components (like the boxes, BMSs, etc.) that are reusable should I want to upgrade the actual battery modules to something else.

Given what I know about what they’re doing on the battery front, I can say...

Pro:

• New cells have a new cell warranty — depending on the company that may be worth something or not.
• New cells should meet their rated capacity, and will take up less physical space for the same kWh. I have no idea who is making the actual cells that are in their batteries.
• Generally plug and play (details like the BMS included / hidden away, etc.)
• Less work to make something that doesn’t look DIY; slick packaging / wiring.
• Less time involved in sourcing components that fit, etc.
• Lower learning curve.
• LFP is a generally safer chemistry.

Con:

• More expensive. As always, you pay for convenience (and not having to know the details.)

One of the things I really like about going the route I am, is that the battery boxes that i’ve built are going to fit 16U of standard, 2U rack-mount batteries. So, when the time comes to upgrade, I know that if I buy more rack mounted batteries, that everything will just fit. Going forward, it’s almost inconceivable that datacenters and power companies will move away from this commodity / rack format — so batteries that fit this system are likely to become more and not less prevalent on the secondary market.

 

[David S]

Yes, i have enjoyed their videos. He does offer some technical tips especially on the AC 240 volt side of things. I don't remember the batteries he used and he does not get into the nitty gritty of batteries as is done on this forum. That may be because they used SimpliPhi or similar.

And likely because their channel isn’t intended for an audience of solar nerds like us. ?. They have close to a million subscribers after all.

 

[David S]

Yep. I’ve checked in on them from time to time. As I understand it, they’re using brand new LFP 48v batteries from Simpliphi. At ~3.8kWh (and ~$2500) each, their six batteries are going to give them ~23kWh of storage at a cost of roughly $15k. That works out to somewhere in the $650-700/kWh range. My setup works out to ~1/6th the cost, including components (like the boxes, BMSs, etc.) that are reusable should I want to upgrade the actual battery modules to something else.

Given what I know about what they’re doing on the battery front, I can say...

Pro:

• New cells have a new cell warranty — depending on the company that may be worth something or not.
• New cells should meet their rated capacity, and will take up less physical space for the same kWh. I have no idea who is making the actual cells that are in their batteries.
• Generally plug and play (details like the BMS included / hidden away, etc.)
• Less work to make something that doesn’t look DIY; slick packaging / wiring.
• Less time involved in sourcing components that fit, etc.
• Lower learning curve.
• LFP is a generally safer chemistry.

Con:

• More expensive. As always, you pay for convenience (and not having to know the details.)

One of the things I really like about going the route I am, is that the battery boxes that i’ve built are going to fit 16U of standard, 2U rack-mount batteries. So, when the time comes to upgrade, I know that if I buy more rack mounted batteries, that everything will just fit. Going forward, it’s almost inconceivable that datacenters and power companies will move away from this commodity / rack format — so batteries that fit this system are likely to become more and not less prevalent on the secondary market.

1000% agree. I find their stuff interesting because they, like you, are using well reasoned thought processes to prioritize their build.

 

[David S]

Wow... I am super excited to see someone who did something similar. As a "beginner" I was afraid I would be fed to the wolves for doing something similar. I am running an RV fully off grid and I needed something to house the solar components exterior to the RV with a ground mount PV array. I put the inverter and batteries into a Job box. I had to slot the top shelf of the internal job box to allow the top vent on the inverter to vent. I am in southern Utah with very few temperature considerations based on the battery spec, but it will get too cold in the early AM for about 2-3 months. My plan is to just let the BMS charging protection manage that for the few hours its below 32. Every day I have seen at the worst mid 40s after the coldest part of the morning. 50s in more common even in the dead of winter.

The first problem I had was the color of the box. In direct sun It would get very hot upwards of 100+. I painted the box white and now it tracks just a few degrees warmer than ambient temp. I plan on shading the box soon before the summer temps hit.

I have installed 2 temperature controlled 4 inch fans. One as intake and one as exhaust. Time will tell if this works.

I just plug the RV 50 amp plug into the box and it is just like a giant solar battery generator. I do not live full time here, just a few weeks at a time

4000 watt solar arrray, Mpp solar LV6048 and 4 - 48V Hsky 103 ah bigbatteries.

You have inspired me to post and I suppose I can take the bad feedback....

Absolutely brilliant!

 

[reg]

Yep. I’ve checked in on [Wild Wonderful Off-Grid] from time to time. As I understand it, they’re using brand new LFP 48v batteries from Simpliphi. At ~3.8kWh (and ~$2500) each, their six batteries are going to give them ~23kWh of storage at a cost of roughly $15k. That works out to somewhere in the $650-700/kWh range. My setup works out to ~1/6th the cost, including components (like the boxes, BMSs, etc.) that are reusable should I want to upgrade the actual battery modules to something else.

I think the difference is that these people make their living by selling a lifestyle. The husband says that his occupation is video maker. They have about 850,000 subscribers on YouTube and 300,000 on Facebook. Their revenue comes from advertising, sponsorships and sale of clothing. Estimates vary, but they are not hurting for income.

They are pumping out a couple of videos a week, which is a full-time job or close to it. Their projects are the raw material for their videos. They have every reason to spend what's necessary to ensure that the projects are trouble-free, apart from what's needed for drama to keep viewers viewing, and to avoid experimentation and the risks associated with saving money.

Nothing wrong with it, but channels like this sell a fantasy. Judging from viewer comments on their channel, they are also selling the fantasy of a perfect, trouble-free marriage. Showing real problems, whether on a project or in their relationship, gets in the way of the fantasy

All of which is a long way of saying that successful lifestyle YouTubers are in the business of selling entertainment.

A final observation... Interestingly, they say in the video linked in the quote above that they are not "sponsored" by the companies that supplied the solar materials. If that is true (is getting a healthy discount "sponsored"?), it was almost certainly a business decision related to perception of credibility. Some YouTubers, such as Peter McKinnon and Marques Brownlee, are very deliberate about who they receive money from and on what terms.

 

[tanoshimini]

You're living the dream, man. I've been thinking about moving off the grid for a long time. When I get my chance I will definitely be learning from you.

I appreciate the complement... but please don’t take anything I say or do as the gospel — rather, consume lots of information from lots of sources, and apply the filter between your ears to screen out the junk. Ask questions; lots of questions. (My grandfather constantly reminded me that there are only two kinds of “dumb” questions: 1) the ones you don’t ask, and 2) the ones you have to ask twice.)

Will you be using HomeAssistant as part of your final system?

I didn’t even know that was a “thing” until you mentioned it. I’ll definitely be looking into that as I move forward. Thanks for the tip!

 

[tanoshimini]

And likely because their channel isn’t intended for an audience of solar nerds like us. ?. They have close to a million subscribers after all.

I tried wearing tighter jeans on my video thumbnails, but it didn’t work out as well for me as it seems to for them. ????

 

[Ampster]

it didn’t work out as well for me as it seems to for them

I can't believe the subtle cheesecake there is in some Youtube videos. I am not referring to that channel although she is attractive.

 

[serene_badlands]

Will you be using HomeAssistant as part of your final system?

Thanks for this!

 

[Freep]

I'm curious if you thought about going underground for thermal protection? You know, making a little mini basement for all your equipment instead of the boxes.

 

[Picasso]

Don't forget to let the boxen breath for condensation. I like these for sealed job box solar builds, wish I could get them cheaper but beats cutting a big square hole and using a PC case metal filter. https://www.solutionsdirectonline.c...4x-ventilation-kit-for-enclosures-p10499.aspx

 

[Freep]

Don't forget to let the boxen breath for condensation. I like these for sealed job box solar builds, wish I could get them cheaper but beats cutting a big square hole and using a PC case metal filter. https://www.solutionsdirectonline.c...4x-ventilation-kit-for-enclosures-p10499.aspx

It looks like a good thing for someone with a 3d printer to make.

 

[Weldman]

I'm curious if you thought about going underground for thermal protection? You know, making a little mini basement for all your equipment instead of the boxes.

I am underground for my thermal protection here as I live full time off grid, you need to be sure to be lower than your frost line in depth. Around here it's 60 inches but some insulation between will help. There is more things stored in here but this is before I buried it 4' ft underground.