At what price does LFP storage make it possible to go off-grid?

[svetz]

Example Spreadsheet now Available​

First pass anyway....
https://docs.google.com/spreadsheets/d/14AMvgJr2mxrx2NPxqzGxOkh3kuu4hjsc4KaJWOOP72o

Not 100% sure if you leave your edits in there if the next person can see them or not, so you might want to copy it to your own workspace....
Theoretically, all the formulas are "protected" from change, so you'll need to copy it to make any changes to them.

Feel free to modify with improvements and repost the next generation.

 

[NPhil]

A self-powered van system is a reasonable thing to have, especially if you're not anchored to a piece of real estate.

LCA Tesla 2170 battery, and to a much lesser extent LiFePO4 - people have seen their vans and houses incinerated by battery packs. Some sort of fire containment and an ejection system might be a good idea, to protect your "home". Metal box, smoke detector, Anderson plug and a chain to yank it out of the vehicle?

Yes! I found out a spot under the (full frame) van, on the opposite side from the fuel tank, where the 2170 cells will fit, in trays which I intend to secure with plastic, which I expect to melt if there is a fire, and drop them on the road, perhaps with the assistance of a "jettison" lever which I intend to add to cut the cables (individually). The LiFePO4 will be in the cabin, in plastic cases, with only a thin layer of fiberglass heat-reflective mat between them and the plastic. "Oh well", as they say. Perhaps I should refine my design to include a jettison for those, too. Possibly one, or both of those (conceptual, at the moment) jettison systems will be automatic, if I get a design concept which I don't think is, on balance, a bad idea.

 

[NPhil]

Yes! I found out a spot under the (full frame) van, on the opposite side from the fuel tank, where the 2170 cells will fit, in trays which I intend to secure with plastic, which I expect to melt if there is a fire, and drop them on the road, perhaps with the assistance of a "jettison" lever which I intend to add to cut the cables (individually). The LiFePO4 will be in the cabin, in plastic cases, with only a thin layer of fiberglass heat-reflective mat between them and the plastic. "Oh well", as they say. Perhaps I should refine my design to include a jettison for those, too. Possibly one, or both of those (conceptual, at the moment) jettison systems will be automatic, if I get a design concept which I don't think is, on balance, a bad idea.

You reminded me that I do have Anderson plugs in my parts bin, so I probably won't cut the cables to jettison. On the other hand, I don't want to make removal of those battery trays too convenient, because it will complicate the design of my anti-theft systems.

 

[12VoltInstalls]

don't want to make removal of those battery trays too convenient, because it will complicate the design of my anti-theft systems.

I’m not sure what you do for a living but you sound like your mind develops ideas and your hands obey acceptably well.

A thought: for myself and others I have made or incorporated into a number of things with hidden compartments. Once the first one was under my belt (hidden compartment in twin fancy drawered jewelry boxes I made for my two daughters) many customers and others got hidden compartments with stealth/hidden releases kind of thing. (several customers are totally unaware of their hidden spaces. So far nobody has contacted me regarding the hidden notes I left in the hidden compartments. I did it for fun and personal entertainment LOL)
It occurred to me along the way that ‘locks’ or releases for not-hidden stuff could use the same principles to secure things.

In your case the point is I’m betting a fail-safe and secure jettison release could be designed in and incorporated…

 

[Hedges]

You reminded me that I do have Anderson plugs in my parts bin, so I probably won't cut the cables to jettison. On the other hand, I don't want to make removal of those battery trays too convenient, because it will complicate the design of my anti-theft systems.

"In-flight disconnects", we called them. Literally. These had a latch and release mechanism.

Other space-flight systems use a guillotine to cut cables. Two, one on each body, for redundancy.

Automatic? That could be "IED deployment system"

 

[eXodus]

Why not just install the batteries in the Garage in a Brick, Block etc. enclosure?

When I used to work in power electronics - we had our flammable transformers in concrete enclosures. Those things contain a flammable oil for cooling. When one those shorted and started burning - there was no way of putting them out. You needed to let it burn until it had no fuel anymore.

Can't be that difficult to do, just stack cinder blocks around the battery bank. Cover it with a some long concrete bricks (A/C pads) or a few layers of hardi-board.

Cover the gaps with some liquids seal for foundations. Concrete bricks are cheap. Further you are adding and ton of thermal mass. Which is good against ambient temperature swings. Helps with calendar aging.

 

[12VoltInstalls]

Why not just install the batteries in the Garage in a Brick, Block etc. enclosure?

because he’s vehicle developing

 

[wattmatters]

First pass anyway....

No access to sheet. Can you change the access setting?

 

[NPhil]

because he’s vehicle developing

Well, there is "Aircrete". Apparently, it is fire resistant. But, the van I have is not large.

"In-flight disconnects", we called them. Literally. These had a latch and release mechanism.

Other space-flight systems use a guillotine to cut cables. Two, one on each body, for redundancy.

Automatic? That could be "IED deployment system"

I never had the opportunity to work with such things, myself, but, I have always supposed that using them would involve, eh, drama:

 

[svetz]

No access to sheet. Can you change the access setting?

Let me know if you still have problems...

 

[eXodus]

because he’s vehicle developing

completely lost track where this thread is going

 

[wattmatters]

Can see it now, thanks.

Seems to be about battery costs only. A focus on battery alone isn't sufficient. I can add all the battery in the world but it wouldn't enable me to be off-grid.

I couldn't go off-grid without significantly increasing my PV capacity. And I would have to change inverter to a larger off-grid unit(s), and provide a housing for a battery storage system and undertake significant trenching and cabling to connect to ground mount arrays, let alone construct the ground mount system.

 

[svetz]

Seems to be about battery costs only. A focus on battery alone isn't sufficient. I can add all the battery in the world but it wouldn't enable me to be off-grid.

True, was assuming people had solar... but I can add that in easy enough... will post when it's updated.

completely lost track where this thread is going

ROFL.... people do seem to wander off topic!

 

[NPhil]

I’m not sure what you do for a living but you sound like your mind develops ideas and your hands obey acceptably well.

A thought: for myself and others I have made or incorporated into a number of things with hidden compartments. Once the first one was under my belt (hidden compartment in twin fancy drawered jewelry boxes I made for my two daughters) many customers and others got hidden compartments with stealth/hidden releases kind of thing. (several customers are totally unaware of their hidden spaces. So far nobody has contacted me regarding the hidden notes I left in the hidden compartments. I did it for fun and personal entertainment LOL)
It occurred to me along the way that ‘locks’ or releases for not-hidden stuff could use the same principles to secure things.

In your case the point is I’m betting a fail-safe and secure jettison release could be designed in and incorporated…

Hidden compartments? I wish I had time, and space, for those! I'm relying on the chaotic storage system. But, it occurs to me that if I use compressed air, or perhaps CO2, instead of explosive bolts, to effect the jettison, I might not get arrested by some evil empire before I even have a chance to find out if it works!

 

[svetz]

Put the solar calculations in, here it is with some fake numbers:

The spreadsheet picks the winter or summer insolation based on the energy consumed in january vs july using the two day max, should be close in most cases. The array size is the average of the two highest consecutive days, obviously that's a matter of opinion. If like me your two consecutive winter days are outliers when you're okay running the generator you should adjust them downwards.

 

[Hedges]

I never had the opportunity to work with such things, myself, but, I have always supposed that using them would involve, eh, drama:

Stage separation

https://ntrs.nasa.gov/api/citations/19790013213/downloads/19790013213.pdf

(Actually, that one is different in that 3rd stage is described as being pushed backwards out of the equipment section by a small rocket motor)

Looks like the guys testing this stuff in development had a lot of fun.

I never did the actual work, but was assigned to witnessing testing and reviewing data submission for things like separation charges.

I think this shows 1st stage separation:

 

[12VoltInstalls]

Hidden compartments? I wish I had time, and space, for those!

Not hidden compartments: hidden releases for your visible batteries slung under the frame!

 

[svetz]

V1.2

• fixed the array size (previously ignoring oversize)
• fixed error in array cost (using wrong cell)
• a couple of minor formatting changes

 

[jberger]

@svetz
First, thank you!
Second, is the Maximum kWh any consecutive 2 days, actually the peak of the range over 2 consecutive days or the total of the max of 2 days?

 

[svetz]

thank you!

You're welcome. Please consider it as a rough calculation, possibly something to start with to refine your personalized version. Hope it's of some help.

@svetz
First,
Second, is the Maximum kWh any consecutive 2 days, actually the peak of the range over 2 consecutive days or the total of the max of 2 days?

It's the sum over 2 consecutive days, so if the values are 95 and 75 you'd enter 170.

It's not very scientific, the idea is the highest day is the outlier you wouldn't mind the generator running on, but averaged with the next day to sort of get a between value to minimize the generator time. It was the first thing that came to mind to handle outlier data (see post#168), probably better ways of doing it.

Update: added a note to the cell header to explain it better.