diy solar

diy solar

Cinergi's 28 kWh / 4 kW Solar / 10 kW inverter RV build

To expand on sizing -- the sq. ft. per BTU does not work in an RV. So all I can say is that 12k is about right for my ~200SF living room/kitchen with tall ceilings and lots of window exposure. The 9k is too much for the 70SF bedroom with short ceiling and almost no window exposure.

Yeah, I am looking at 12k for the living room/kitchen, 9/10k for the garage, and 7k for the bedroom. Assuming I can source units in that range that fit.

For the window casings, if you have windows with double frames, then you can sometimes put a bit of rubber or plastic between the trim ring and the outer frame. Doesn't work with frameless though.

3M makes a special ceramic tint that reflects most UV, and almost all of the IR, without affecting visible light. They make a huge difference in my vehicle.
 
3M makes a special ceramic tint that reflects most UV, and almost all of the IR, without affecting visible light. They make a huge difference in my vehicle.
may I inquire as to how you source it?

also, may I ask what film model you use?

thanks and no worries if it's trouble for ya
 
Yeah, I am looking at 12k for the living room/kitchen, 9/10k for the garage, and 7k for the bedroom. Assuming I can source units in that range that fit.

For the window casings, if you have windows with double frames, then you can sometimes put a bit of rubber or plastic between the trim ring and the outer frame. Doesn't work with frameless though.

3M makes a special ceramic tint that reflects most UV, and almost all of the IR, without affecting visible light. They make a huge difference in my vehicle.

I've got some Gila heat shield tint to install one of these days. They're frameless windows so yeah ... gonna install them on the outside (despite all the warnings about not doing so especially on dual-pane windows; I discussed with Gila and the only downside is reduced lifetime of the film itself).
 
25 last night. This time I left the LR zone on (BR off, door open). Maintained 65 degrees in the LR all night (zone ran full blast all night). Probably not doable with solar on an RV (I've already consumed 17kWh today and it's only 11am; I have shore power connect at 50% SoC and disconnect at 100% right now) but certainly nice to be able to heat w/out propane even in these temperatures.
 
For comparison an acquaintance has a 30ft composite box mobile office he uses for gas field work. He indicated that it will be comfortable with a 10k split even near zero. I believe its 30x8.5x8ft with 2.5" foam composite walls. It only has 2 small thermal double glazed windows.
 
Last edited:
I've completed the last revision the battery before I head to Kanas next week (in theory) to pick up the new RV and install this (at their facility with their assistance WRT any welding or physical work beyond my capabilities).

The previous revision had a few spots that were +40F under 120 amps of load, so I thought about it and figured out a better way to do the bus bars at the ends of the strings. I previously had 3/4" x 1/8" everywhere ... because I can't fit 1" wide bar through the hall effect current sensor. But for some reason (I've been at this for too long) it didn't occur to me to use 3/4" only for the current sensor, and 1" everywhere else. And that I could still terminate everything with 1" if I build a "bridge" with 2 3/4" pieces sandwiching the 1" pieces on either end:

View attachment 41936

I just ran 9000 watts through the system and observed a +15F maximum temperature rise. Woot!

I also decided to create a dedicated standoff system for the BMS and Breaker boards which would move with the cells as they expand and contract. Having them screwed down to the black threaded rod meant that there were considerable stresses on these bus bars and I saw the contactor ripping away from the plywood.

So this version has heat shrink on the bus bars at the ends of the cells (I don't have enough to do the cell bus bars and man I'm tired of working on this thing lol). I also got all the wires in split loom and secured with strain reliefs.

BMS board with contactor, SSR, and Ethernet for CANBUS:
View attachment 41937

Other side of that board:
View attachment 41938

Looking down the cells from that board:
View attachment 41935

Breaker board:
View attachment 41940

Other side of breaker board:
View attachment 41939

Entire set:
View attachment 41933

Back of the set (this is 1 gauge wire temporarily, will be 3/0 in the RV):
View attachment 41934

That wire, BTW, supported the 9000 watt load with a +25F temp increase.
Hellooo,

What i do not get in those kind of build is ... why bussbars are rigid, will there not be strain on those bars and indirectly on terminals ?
 
We've seen pictures of battery packs for EVs that have rigid (or at least solid) busbars welded to terminals. But they are formed in a shape which allows flexing in the direction of cell expansion.

Obviously busbars holding cell terminals at a fixed spacing is a concern, either for cell expansion or cell movement in a vehicle.
Maybe with compression fixtures clamping cells, any such displacement is limited to thermal expansion of busbars.
 
We’ve seen pictures of battery packs for EVs that have rigid (or at least solid) busbars welded to terminals. But they are formed in a shape which allows flexing in the direction of cell expansion.
Exactly, such as this:

6A5D8E0C-05F6-41A1-B048-EEB9BF969A55.jpeg
Obviously busbars holding cell terminals at a fixed spacing is a concern, either for cell expansion or cell movement in a vehicle.
Maybe with compression fixtures clamping cells, any such displacement is limited to thermal expansion of busbars.
Only time and use will tell whether rigid busbars clamped onto aluminum terminals with grubscrews secured into threads tapped into aluminum terminals (or welded onto them) causes reliability / lifetime issues or not, but I’m happy with my decision to stay away from them in favor of flexible cable connections.
 
We've seen pictures of battery packs for EVs that have rigid (or at least solid) busbars welded to terminals. But they are formed in a shape which allows flexing in the direction of cell expansion.

Obviously busbars holding cell terminals at a fixed spacing is a concern, either for cell expansion or cell movement in a vehicle.
Maybe with compression fixtures clamping cells, any such displacement is limited to thermal expansion of busbars.
I suppose a bussbar with a sort of U/V shape could flex in case of constrain yes, but .. if i'm not mistaken, Cinergi's build got rigid flat bussbars and i feel it could be dangerous in case of expansion. I feel that even a small expansion would put stress on those terminals. And on 16 cells in a line... it even adds up.
 
Has anyone actually seen a cell be damaged from a fixed/rigid bus bar pulling on a terminal? I see talk about it alot, but never seen it happen.
 
I measured the expansion between terminals (earlier in my thread) while in the compression fitting using flexible cables ... and I observed *fractions* of a mm of movement (like, 0.1 to 0.5mm max) Nothing to be concerned about IMO.
 
I measured the expansion between terminals (earlier in my thread) while in the compression fitting using flexible cables ... and I observed *fractions* of a mm of movement (like, 0.1 to 0.5mm max) Nothing to be concerned about IMO.
I suppose expansion is based on multiple parameters like temperature and voltage (state of charge), by that i mean that perhaps you did not reached the worst case scenario.
Flexible busbars solve this risk ... they are not really more expensive... i can't see why not using them.

Remind me the guy that put bottle on a shelf ... add more .. more .. more .. there is no stress visible on the shelves system then all fall down, cause it reached the point of no return but before fail .. nothing as moved.

Now, those terminals are not going down the cell, they are just connectors and then there are some flexible foils going down, the way it's builded i suppose that stress on the terminal is not that critical, appart from a leak..... but again .. i'm not a battery specialist. I use flexible busbars and my box is built with aerated concrete, this way i reduce risk and... seeing some bad situations with Lithium (even LiFePo4) on youtube mostly... i feel safer. Perhaps it's just me, i dunno. Something that is built to last like .. 20 years ... got to be seriuously built. (and no i'm not saying that all build without flexible bars are not seriously built .. :)) some are pretty impressive.. BUT .. flexible bars is must have imo.

prismatic_cell_cross_section_edge.jpgInside Prismatic.jpg
 
Last edited:
I suppose expansion is based on multiple parameters like temperature and voltage (state of charge), by that i mean that perhaps you did not reached the worst case scenario.
Flexible busbars solve this risk ... they are not really more expensive... i can't see why not using them.

Remind me the guy that put bottle on a shelf ... add more .. more .. more .. there is no stress visible on the shelves system then all fall down, cause it reached the point of no return but before fail .. nothing as moved.

Now, those terminals are not going down the cell, they are just connectors and then there are some flexible foils going down, the way it's builded i suppose that stress on the terminal is not that critical, appart from a leak..... but again .. i'm not a battery specialist. I use flexible busbars and my box is built with aerated concrete, this way i reduce risk and... seeing some bad situations with Lithium (even LiFePo4) on youtube mostly... i feel safer. Perhaps it's just me, i dunno. Something that is builded to last like .. 20 years ... got to be seriuously built. (and no i'm not saying that all build without flexible bars are not seriously built .. :)) some are pretty impressive.. BUT .. flexible bars is must have imo.

View attachment 74456View attachment 74457

Those are some very good pictures you found ... excellent teaching points ...
 
I suppose expansion is based on multiple parameters like temperature and voltage (state of charge), by that i mean that perhaps you did not reached the worst case scenario.

I tested 0% SoC to 100% SoC - worst case scenario. Expansion is based on SoC, not temperature.

Flexible busbars solve this risk ... they are not really more expensive... i can't see why not using them.

I had poor performance with wires. The gory history is in this thread. I didn't try flexible - too expensive with 32 cells that's capable of 200 amps.

Remind me the guy that put bottle on a shelf ... add more .. more .. more .. there is no stress visible on the shelves system then all fall down, cause it reached the point of no return but before fail .. nothing as moved.

Except that I measured and we've seen no failures related to solid bus bars.

Now, those terminals are not going down the cell, they are just connectors and then there are some flexible foils going down, the way it's builded i suppose that stress on the terminal is not that critical, appart from a leak..... but again .. i'm not a battery specialist. I use flexible busbars and my box is built with aerated concrete, this way i reduce risk and... seeing some bad situations with Lithium (even LiFePo4) on youtube mostly... i feel safer. Perhaps it's just me, i dunno. Something that is built to last like .. 20 years ... got to be seriuously built. (and no i'm not saying that all build without flexible bars are not seriously built .. :)) some are pretty impressive.. BUT .. flexible bars is must have imo.

All commercial LFP batteries we've seen are built with solid bus bars. Many people here build with solid bus bars. I'm not aware of any failures related to solid bus bars. Combined with my measurements, I'm confident there's no cause for concern.
 
All commercial LFP batteries we've seen are built with solid bus bars. Many people here build with solid bus bars. I'm not aware of any failures related to solid bus bars. Combined with my measurements, I'm confident there's no cause for concern.
The only caveat I would add is that commercial battery packs are engineer solutions, hopefully with some R&D and testing, and are usually more thoughtfully and precisely secured than a lot of DIY'ers will do. Unless we are talking about the many cheap off-brand drop-in replacement batteries coming out, but most of those are pretty new and untested (in the long term).

I'm not saying there is anything wrong with solid busbars, just that being reassured by commercial use should probably only be reassuring if you have designed the enclosure/compression system, as thoughtfully and robustly as comparable quality commercial offerings. In your case, I know that you have, but most folks still opt for less robust solutions (The Will P. electric tape special.. ?, or putting the cells in a roughly sized plastic battery box with some things wedged in to prevent movement, or in some cases no securing the cells at all beyond the busbars and gravity/inertia). But I suppose that is a bit of a tangent.
 
0B43E958-592C-4903-8111-3DB60FBEFC31.jpegThe only caveat I would add is that commercial battery packs are engineer solutions, hopefully with some R&D and testing, and are usually more thoughtfully and precisely secured than a lot of DIY'ers will do. Unless we are talking about the many cheap off-brand drop-in replacement batteries coming out, but most of those are pretty new and untested (in the long term).

I'm not saying there is anything wrong with solid busbars, just that being reassured by commercial use should probably only be reassuring if you have designed the enclosure/compression system, as thoughtfully and robustly as comparable quality commercial offerings. In your case, I know that you have, but most folks still opt for less robust solutions (The Will P. electric tape special.. ?, or putting the cells in a roughly sized plastic battery box with some things wedged in to prevent movement, or in some cases no securing the cells at all beyond the busbars and gravity/inertia). But I suppose that is a bit of a tangent.
What we need is for someone to take a dead cell, attach it to an adjacent dead cell or cell mock-up with a solid busbar, and see how much torque / bottom displacement can be applied before the terminal starts to rip out of the casing…

It’s probably an exceedingly low-likelihood event, and solid busbars will provide a limited amount of flex bending along their length and across their width. But with the possibility of shots and the energy levels involved, seems as though any possible precaution is not too much precaution…

This picture ought to be a reason for concern (BYD battery):

0B43E958-592C-4903-8111-3DB60FBEFC31.jpeg

It’s hard to fathom why they would have gone to the trouble and expense of designing welded solid busbars with flex if they didn’t need to…
 
I tested 0% SoC to 100% SoC - worst case scenario. Expansion is based on SoC, not temperature.



I had poor performance with wires. The gory history is in this thread. I didn't try flexible - too expensive with 32 cells that's capable of 200 amps.



Except that I measured and we've seen no failures related to solid bus bars.



All commercial LFP batteries we've seen are built with solid bus bars. Many people here build with solid bus bars. I'm not aware of any failures related to solid bus bars. Combined with my measurements, I'm confident there's no cause for concern.
https://www.google.com/url?q=https:...sQFnoECAQQAg&usg=AOvVaw2x8_UuGeDUsLXidhjMn96s

Temperature as an effect.

That you did not seen any problems with rigid busbars do not prove that there isn't any.

"Any commercial"... many serious build use flexible busbars. It's pretty obvious that there will be stress !

The only way to have no stress on rigid busbars is to let some space between cells AND constrain them, this way there will be enough space between them to inflate THEN the compression would prevent them to inflate further. Busbars would have to be screw at the max acceptable inflation. This way cells can only deflate and create space between cells.
 
Back
Top