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Everglades Powerwall
#1
Here's my Everglades camp electrification project.

I should start by saying I very much appreciate the knowledge and expertise that you all share in this forum. I'm learning a lot. In posting my own mistakes and successes I hope that someone else can benefit as I have by reading about your projects.
 
So we have a cabin and 3 acres in the Big Cypress National Preserve in the Florida Everglades which we've owned since the 1960's before it was a Preserve. The location is very remote and reachable only by a loooong ride via off-road vehicle (swamp buggy). We love spending time there, but it's often hot, humid & uncomfortable so we can only really enjoy it from October to May. Even then it can be unpleasant some days. Learning about this Powerwall idea got me thinking about the possibility of trying to make the place a little more comfortable.
 
A little about the current setup. The camp is very basic - about 20 x 40 ft with a metal roof and no insulation. The "windows" are screened 4x8 ft openings with plywood awnings which are propped open while we're there. These get bolted down to keep the bears out while we're gone. It's always been a hunting camp even though none of us have hunted in years. So really just a relaxing, beer drinking, "get away from the rat race" camp. Sleeps 7.

 

About 5 years ago, I "solarized" the place with an 18W panel I salvaged from a USCG dumpster, a 20A Morningstar PWM controller, and a 91 Ah "D" size John Deere tractor battery. Certainly not the ideal setup, but everything was free and has been working great for 12V LED lights, charging tools & cell phones, and running small computer fans to "knock the sweat off". The little solar panel is probably way undersized for the battery, but we're rarely there for more than 2 nights, and often go a month or more between visits. It pretty much stays fully charged.

 

So I'm thinking now about how best to use these 18650's I'm collecting to make things better. We have an ancient 1940's full size Servel gas refrigerator / freezer that works great and a gas stove / oven. No indoor plumbing except a kitchen sink drain.
 
Some of the things I'd like to add:
  • 110V Ceiling fans - probably 2 or 3.
  • An efficient LED TV & satellite dish (so we don't miss the football games).
  • Convert existing 12V LED lighting to AC.
  • Power tool charging, and occasional corded tools.
  • Maybe an LTE modem / router if I can figure out how to pull in a nearly non-existent signal. If I get that figured out, I'd love to add remote powerwall monitoring, weather station, WiFi game cameras, etc.
 
Based on these loads (and doubling it to cover stuff I didn't think of), I'm shooting for a system capacity of about 6 KwH so my plans for the battery bank is a 14s60p configuration. Here's my calculations - hope they're correct:

14s60p = 840 cells @2100 mAh average.
14 packs * 3.7V = 51.8V
51.8V * (60 cells * 2.1 Ah) = 6.526 KwH

I'm numbering cells individually and tracking them in an Excel spreadsheet. I'm only planning to keep cells better than 1900 mAh & 75% of rated capacity. No "heaters" allowed.  Here's what I've got so far in about a month of scavenging and testing. I added another pack this morning, so we're halfway there:

 

I cobbled together an 8 slot TP4056 charger that really helped speed up the process. Still only have two OPUS testers though so that's my bottleneck. I'm in no big hurry.

 

Not planning to start soldering busbars until I have enough cells for the entire string. I want to distribute capacity as evenly as possible across packs. I should probably start practicing with some throwaway cells first. I've ordered a fat iron. Is plumbing solder just as good as electronics solder for this application? Is there any value to using a solder paste pen to ease this process along? Last thing I want is to ruin cells by overheating them.
 
I definitely plan to include a BMS. Batrium is very nice - especially the monitoring. I'll probably go that route unless I find a less expensive solution.
 
I'm still really concerned about safety of the system with nobody there to monitor for problems. I'm considering putting the entire system in a separate shed and just running AC to the cabin. That way if something goes wrong and it burns up we minimize our losses. Anyone else using this approach for absentee powerwall systems? Need someone to put my mind at ease about this.
 
In any event, I'll be assembling and testing everything in my barn at home for months before I declare it's safe. Then I'll take it down to camp for installation.
 
Thanks for reading. I know it's kind of long. I'll be posting shorter updates when they happen.
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#2
Wow, nice! Can't beat free! Big Grin

The one thing I'll bring up, is that you are going to want to make sure Lithium cells stay dry. That means away from the humidity, as well. You're gonna want to put them into some kind of container you can keep the moisture out of. Otherwise you'll end up with a whole other issue to deal with later.

There's no reason to change to AC led lighting. You can still run LED's on high voltage DC if you "need" the 120V. It gets rectified or serialized anyways. You can accomplish this by using a Boost converter.
If you stick with 12V LEDs, then you could use a Buck converter to run those. You won't be drawing much amps overall. You can set each light with it's own Buck converter right at the light (as opposed to at the switch to minimize voltage drop).
The reason I say to go these two routes is to keep your conversion losses to a minimum. A buck or boost converter is far more efficient than inverting to AC then converting back to DC.

Ceiling fans will either "have" to run on Pure Sine way inversion, or get DC rated fans. The DC fans you can find looking at RV/Boat supplies

Most other electronic devices can probably run off of 120VDC, such as the TV, computer, modem, etc. As mentioned earlier, they drop the voltage down and convert it anyways.
Perhaps a little google foo on running AC electronics on DC can get you some guides to go by.

Now, I don't suggest you run your wiring at 120VDC. That's too dangerous. I would only suggest this is done right at the device that requires it. And if you can get away with "not" boosting the voltage that high, go that route instead.


Side Note: I see you have a gator avatar, fan obviously. Did you grow up in/near gville?
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#3
(10-18-2018, 08:57 PM)Korishan Wrote: Wow, nice!  Can't beat free!  Big Grin

The one thing I'll bring up, is that you are going to want to make sure Lithium cells stay dry. That means away from the humidity, as well. You're gonna want to put them into some kind of container you can keep the moisture out of. Otherwise you'll end up with a whole other issue to deal with later.

I had wondered about that, but nearly all of the cells I've harvested so far have seen years of storage in non-air conditioned storage spaces. Pretty much the same environmental conditions they'd see in the powerwall (aside from being actually used).

Quote:There's no reason to change to AC led lighting. You can still run LED's on high voltage DC if you "need" the 120V. It gets rectified or serialized anyways. You can accomplish this by using a Boost converter.
If you stick with 12V LEDs, then you could use a Buck converter to run those. You won't be drawing much amps overall. You can set each light with it's own Buck converter right at the light (as opposed to at the switch to minimize voltage drop).
The reason I say to go these two routes is to keep your conversion losses to a minimum. A buck or boost converter is far more efficient than inverting to AC then converting back to DC.

Ceiling fans will either "have" to run on Pure Sine way inversion, or get DC rated fans. The DC fans you can find looking at RV/Boat supplies

Very good points, and something I've been considering. I think where I'd run into trouble though is if I go with the idea of keeping the powerwall system in a separate shed and running only AC to the cabin. Depending on the load needed, bringing 48V DC 75 feet or more would require pretty substantial cabling, right?

I've got an old APC 2200XL rack mount UPS that's 48V and sine wave. Damn thing weighs almost 100 lbs without batteries. I'm considering using it. Will definitely test with it. I looked into those DC RV fans and freaked out at the prices.. LOL.

Quote:Most other electronic devices can probably run off of 120VDC, such as the TV, computer, modem, etc.  As mentioned earlier, they drop the voltage down and convert it anyways.
Perhaps a little google foo on running AC electronics on DC can get you some guides to go by.

Now, I don't suggest you run your wiring at 120VDC. That's too dangerous. I would only suggest this is done right at the device that requires it. And if  you can get away with "not" boosting the voltage that high, go that route instead.



Side Note: I see you have a gator avatar, fan obviously. Did you grow up in/near gville?

I'm from SW Florida. I'm a UF alum and two-time Gator dad. Youngest is enrolled there now. Go Gators!

BTW, I've looked at the 48V-12V buck converters on Ebay and Amazon, but it looks like they're all built for golf carts and fairly low amperage. Where to find something a little beefier with a higher duty cycle?
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#4
If you use the buck at the led lights, each one/strip that is, then you'd only need one that puts out 3A, as the LED light won't be pulling a lot.
You can also parallel some, but this isn't always the best and involved adding a couple more diodes to the mix.

Going 75Ft from where the Batteries are to where they'd be used at. Hmm, yeah, that's 150FT electrically and that's a lot of loss. I will have to agree with AC inversion at this point, unless you go high DC voltage. But again, that's not safe. And even less so in the high humidity of the Everglades.

Using the UPS is a good idea. Just remember that you will need to add extra cooling for the constant duty cycle. I have the same unit. That thing is a beast. Is yours rack mount or stand alone? Mines stand alone. Huge transformers in it. I plan on adding some cooling fins to them and mounting them separate from the electronics. Custom cage for the whole thing

If the cells where inside a laptop pack, even exposed to outside elements for long durations, they are still fairly separate from humidity, by nature of the design of the pack. If your pack designs exposes the ends directly to changing conditions like the weather is down there, then it could be a problem. At least I would recommend keeping them behind some sort of cabinet that minimizes humid air flow across them. You still need airflow to keep them cool, especially during charging. But you can minimize the damage the humidity could cause.
If you were not surrounded by so much wet, I wouldn't of mentioned it in the first place. But you are practically living on the water there Tongue As long as the sump pumps keep working, you'll be fine. But if they fail, you 'will' be living on the water Wink

Hahha, nice. I leave near gville. Not much of a sports fan overall. But the rest of the family is. I'll watch the occasional game with them, or at least parts of it.
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#5
6.25kwh is quite a lot of power (I ran with that all summer until this Sept). With all the losses you will end up around 4kwh of usable power (3.5kwh for me, but that's because I wasn't pushing my batteries but for you it's not about the number of cycles since you're not living year round so you can push it harder). That's enough to run 300watts continuously for 12 hours. So a full size fridge is possible (takes up roughly 500-1000wh per day), along with a couple hours of TV with no issues (they run around 150-200watts). Lights don't take up much power (ac or dc), all LED lights are now 6-8watts, that's practically nothing.. Fans will be troublesome part, a box fan takes upwards of 80-100watts to run. Stick to smaller directional fans like a vornado or equivalent. They put out lots of wind at around 30-50watts. If you have enough panels, a small 5000btu window a/c is also possible, although only a few hours at night. For rainy days then you'll have to resort to gas generators to charge the batteries.

For leaving it while you're gone, unless you really want to keep it up and running 24x7, I'd just suggest turning the whole system off. If you want remote monitoring, then use your current setup, which is a smaller setup just with enough juice to run the monitoring system. Turn the main system off. Better piece of mind.

Just run your setup at home first once you set it up. Just extension cord everything up at your home and see what it can do. You'll be presently surprised.
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#6
(10-19-2018, 12:11 AM)not2bme Wrote: 6.25kwh is quite a lot of power (I ran with that all summer until this Sept). With all the losses you will end up around 4kwh of usable power (3.5kwh for me, but that's because I wasn't pushing my batteries but for you it's not about the number of cycles since you're not living year round so you can push it harder). That's enough to run 300watts continuously for 12 hours. So a full size fridge is possible (takes up roughly 500-1000wh per day), along with a couple hours of TV with no issues (they run around 150-200watts). Lights don't take up much power (ac or dc), all LED lights are now 6-8watts, that's practically nothing.. Fans will be troublesome part, a box fan takes upwards of 80-100watts to run. Stick to smaller directional fans like a vornado or equivalent. They put out lots of wind at around 30-50watts. If you have enough panels, a small 5000btu window a/c is also possible, although only a few hours at night. For rainy days then you'll have to resort to gas generators to charge the batteries.

For leaving it while you're gone, unless you really want to keep it up and running 24x7, I'd just suggest turning the whole system off. If you want remote monitoring, then use your current setup, which is a smaller setup just with enough juice to run the monitoring system. Turn the main system off.  Better piece of mind.

Just run your setup at home first once you set it up. Just extension cord everything up at your home and see what it can do. You'll be presently surprised.

I agree this is probably bigger than needed right now. But free batteries,  and who knows what loads we'll throw at it later?

Having real ceiling fans is pretty much the whole point of this build. This is one I was looking at. Says it draws 64 watts which I assume is at high speed. Running 3 of those overnight for 7 hours would consume about 1300wh. We'd probably skip watching the game just to run fans it was hot.  Smile  There are more efficient fans available, but at crazy prices. I'll keep looking for the best bang for the buck in terms of CFM / watt.


Keeping the old 12V system in place is something I hadn't even considered. I could easily replace the 18w PV panel with something a little bigger and run the coms / monitoring stuff 24/7/365. Thanks for that suggestion.

One concern though... we usually leave camp at around 9 or 10 in the morning since it's a 2 hour buggy ride out, and another 1.5 hours road trip to get home. If we drew down the powerwall overnight and shut it down without enough sun time to charge before we left, would that hurt the bank over time?

Reading your Outhouse project thread now. Very nice setup. Cheers!
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#7
You could set a timer that was voltage based. It would allow the system to charge back up to about 3.65V/cell to allow for storage. And then periodically (if you wish to do so) come on and give a jolt from time to time.
But one things for certain, you don't want the cells sitting low voltage for storage. You'll shorten their life span. Free or not, don't waste them Wink
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Certified 18650 Cell Reclamation Technician

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#8
The UPS being rack mount and server grade, will most likely not require any extra cooling. However they are usually a little on the inefficient side. But given you already have it, I would definitely consider using it.

Using 12v buck converters to run lights would be great - especially at night - when you didn't need the AC you could shut the UPS off to save power.

Agreed with dropping the batteries to storage charge when not in use. You will definitely prolong their life expectancy. You may find that if you leave early in the morning that they may be close to the right voltage. Perhaps even switch the PV off before going to bed, then they won't charge in the morning.

You will want to check very carefully for self discharge. If a cell goes rogue while you are away it could potentially damage all of the others in the pack.
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#9
Hi there.

Could the powerwall be stretched to do a small AC? If so, I'd go for a <$100 one, like this: https://www.brandsmartusa.com/arctic+kin...tioner.htm. It should pull about 4 amps when cooling and if you set the temperature moderately, it won't have to run all night. There's a slight risk the ceiling fans will pull the metal roof heat down.

If you don't have a source for your panels, I recommend Tony at sunelec.com in Miami Lakes. They have inexpensive panels and also sell inverters, cables, etc. It's great to have them as a local shop for quick runs/no shipping.

Regards,
JR
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#10
(10-19-2018, 09:54 PM)JRoque Wrote: Hi there.

Could the powerwall be stretched to do a small AC? If so, I'd go for a <$100 one, like this: https://www.brandsmartusa.com/arctic+kin...tioner.htm. It should pull about 4 amps when cooling and if you set the temperature moderately, it won't have to run all night. There's a slight risk the ceiling fans will pull the metal roof heat down.

If you don't have a source for your panels, I recommend Tony at sunelec.com in Miami Lakes. They have inexpensive panels and also sell inverters, cables, etc. It's great to have them as a local shop for quick runs/no shipping.

Regards,
JR

Hey JR,

I posted a question and link to some used sunelec.com panels in another topic this afternoon. I just found them yesterday googling. Turns out they're just 3 hours away. I'll be sure to look up Tony when I go there - thanks for that.

I'm pretty sure that A/C is out of the question given that the cabin isn't insulated at all. You'd have to stand in front of it to get any benefit, LOL. That's OK though... our family has a long history in S. Florida and we all grew up without A/C. But ceiling fans are made in heaven when it's hot and the bugs are bad. Smile
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