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offgrididaho
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# Posted: 15 Oct 2018 08:58am
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In the spring we will be bringing proper solar and battery to a cabin we bought in Washington. Basically all that's there now is a regular domestic 120v and a generator.
In my never ending, circular conversation I have with myself about where to put my "power wall" (batteries, charge controller, inverter) I am now considering a shed that is ~65 feet from the cabin. I am doubting I will be able to use Bluetooth from the cabin to the shed to look in on my Victron controller or a Victron battery monitor (possible, but somehow I doubt Victron uses Class 1 Bluetooth).
Are there other ways to "remotely" monitor my battery bank? I don't need to do it from anywhere in the world (although I might eventually have lightweight internet so that would be a nice option), just thinking maybe WiFi or even buried Cat5? I just would prefer not to walk out there every time I want to see how the batteries are doing, as I know I won't do it frequently enough and my batteries will suffer as a result.
Any ideas appreciated.
Thanks.
-- Bass
(OK, my crudest idea would be to put in a mini IP camera pointed at the battery monitor, but that's pretty crude!)
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Borrego
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# Posted: 15 Oct 2018 10:26am
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You can't put it any closer? Maybe build a little shed by the side of the house?
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SCSJeff
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# Posted: 15 Oct 2018 10:33am
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I use a trimetric meter inside my cabin monitoring the batteries out in my shed. I tried running a CAT5 cable, but the individual strands were too small to get reliably attached. I ended up just buying small gauge individual cables from Lowes and running them between the batteries and the meter.
I love it because at any moment, I can just glance over to the wall and see the current percentage of battery left. It if gets too low (for my comfort), I just turn off the inverter then. (Also remotely controlled from inside the cabin)
http://www.bogartengineering.com/products/trimetrics.html
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Nate R
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# Posted: 15 Oct 2018 10:46am
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Yep, I was going to suggest a Trimetric as well. IIRC they can easily do 100+ feet. There's some special wiring instructions for long runs, but it's in the manual. Once one of those is set up, it's sweet to see amps going in/out and how your battery is doing.
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offgrididaho
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# Posted: 15 Oct 2018 11:36am
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Thanks everyone, was not familiar with the Trimetric so will investigate that.
Also looks like Victron has the VenusGX which will consolidate data and make it available via wifi.
I will consider another shed closer to the house but I'm restricted on adding another shed by island regulations... I guess I could just cover something under the foundation (which is open) but then I'm crouched down there when I'm checking water levels etc... I like the idea of being inside when checking on systems but still doing this in a shed instead of the cabin so I don't feel bad about blasting holes in the walls for venting the battery box etc. Plus there is covered open space next to the shed where the generator runs so it makes sense in my mind to put all the "power" in one place.
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SCSJeff
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# Posted: 15 Oct 2018 12:56pm - Edited by: SCSJeff
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Offgrididaho,
That's how my shed is setup. Lean-to behind it with generator under it. Have auto transfer switch inside shed switching between inverter and genny.
The only pain is that I have to walk out to start/stop the genny. Saving up and watching for sales on a wireless genny 
Note: my shed is about 60' from the cabin
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creeky
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# Posted: 16 Oct 2018 10:58am
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Note: My "power house" is 100 ft from my "great room."
Victron has the BMV 712 Smart
"connects to the monitor with a standard RJ12 telephone cable"
It comes with a 10 meter (30ft) cable but shouldn\t be too hard to find a longer cable. I see an online retailer with 75' at $35.
I use the mini IP camera. It was the cheapest option for me. <50. It hasn't been working in 9 months. I'll get it going again now that its fall. I do need the charger a few times in the winter.
By "power wall" I'm guessing you're going lithium also? No venting required. Depending on climate make sure you insulate your battery box. Most of us use a battery blanket. Some folks put it on a thermostat. Again. I use mine so infrequently I have mine on manual. I turn it on remotely with zigbee/wifi.
I would love to find a zigbee/wifi battery monitor if anyone knows of one.
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offgrididaho
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# Posted: 16 Oct 2018 01:41pm
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Thanks everyone for your replies. I wasn't sure how long a cable I could use with the BMV 712 (which I was planning to use), so that might be a good choice too.
Should have been clearer, I have just been calling it a "power wall" because it's going to be one wall of all my components (inverter/charger, inverter bypass switch, charge controller, batteries etc) that I'm going to build onto plywood here at home and take as assembled as possible to the cabin so I don't have to do all the work there. I will be using FLA 6v golf cart batteries, vented through the wall of the shed.
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SCSJeff
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# Posted: 16 Oct 2018 02:59pm - Edited by: SCSJeff
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Not sure how "tight" and/or small your shed is compared to mine. (I have a 6x8). At any rate, I didn't worry about venting anything. I have the FLA batteries sitting inside an old cooler inside of a rubbermaid deck box. None of it is sealed tight. And I don't have any special vents from the box going out of the shed.
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creeky
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# Posted: 16 Oct 2018 04:51pm
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I wouldn't use vented FLA. Lead is dead.
Lithium is 20% more efficient. Your whole system is 20% bigger just by changing the battery. Makes the most difference in the off seasons (winter esp.).
Lithium is the missing element in good off grid solar.
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ICC
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# Posted: 16 Oct 2018 05:47pm - Edited by: ICC
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Lithium batteries are very good. Change to known technology is sometimes slow to take effect especially when a larger initial investment is needed.
A friend replaced 4 lead acid golf cart batteries last year using two of these these. Initial cost was more, but they don't need watering, don't off gas, are much easier to handle, safer because there is no acid exposure risk, and will last longer. They have BMS built in and have a low temperature cut out so you don't even have to remember they should not be charged when below a certain temperature. He did some re-arranging of his system and now has the LiFePO4 batteries on the interior side of the wall where the lead-acid used to be outside.
SCSJeff, with no venting of that battery box you can have a build up of hydrogen and oxygen. Hydrogen is so light it probably leaks out the lid if it is not sealed down, but it could still be a dangerous situation especially if you or anyone smokes around there.
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NorthRick
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# Posted: 16 Oct 2018 07:47pm
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More expensive is a bit of an understatement. Even here in Alaska I can buy 4 golf cart batteries off the shelf for $340. Two of those lithiums are $1900 plus whatever shipping is.
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SCSJeff
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# Posted: 16 Oct 2018 09:57pm
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ICC,
Regarding the safety... No smoking to be concerned about. I don't keep the cooler lid on during the summer and I only set it on loosely with a shim keeping the corner open during the winter. The deck box itself doesn't have anything close to a seal when the lid is closed. Plus the several holes drilled in the back for all the cables will allow additional "venting".
The shed itself is not insulated and or walled up. So I'm sure it has no problem venting the off gas.
Regarding Litium... I'm with NorthRick. Those batteries (with the proper setup to prevent charging below freezing) is way more than I can swallow. I can keep buying Golf Cart Batteries for the next 20 years and still be ahead (expecting 5-7 years per set). My real concern is if I can't charge them below freezing, then what do I do when I use all my power up? Live off generator 24x7 or go home  Unfortunately, moving them inside is not an option as my entire "power shed" is 60+ feet away from cabin
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neckless
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# Posted: 16 Oct 2018 11:53pm
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how do the lithium batteries work in -30 in a shed used on weekends
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ICC
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# Posted: 17 Oct 2018 12:14am - Edited by: ICC
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The unheated shed would be a problem at those temperatures because the lithium should not be charged below freezing, more or less. They can be discharged when frozen but should not be recharged.
The solution is easy. Move them to inside the main dwelling. My friend has them in a part-time use cabin, inside where it is heated when he is there. When he leaves, the batteries are left somewhere between half and 70% charged. He turns everything off; no power is used and the charge controller is turned off. The batteries can be left like that for a year probably. The cabin cools and everything is fine. When he goes back he starts a fire in the wood stove and also uses a propane wall heater if it is very cold. He can use power while the cabin warms up. After several hours the contents of the cabin has warmed and the batteries are warm enough to accept a charge.
There is no need to keep the LiFePO4 batteries separate from the habitable area, unlike lead-acid. Yes, it may require some work to reconfigure the charge controller, batteries and inverter locations but that is a one-time thing. Think of it like doing a renovation. If one of the reasons the batteries were remotely located in the first place is because a generator was involved, that is OK. The generator can probably stay where it is if you run a heavy enough 120 VAC wire from genny to battery charger. The genny may not even be needed as much as the lithium charge faster from the same PV panels and the same amount of sun. Lithium batteries don't waste as much incoming charge current as lead-acid do, so they charge faster.
It is important to keep the lithium warm though in order to charge them. That is one reason Teslas use an integrated 'cooling' system. The system keeps the cells cool when they get heated from charging or heavy use and the system also uses heat from the electric motors to warm the cells when they are very cold.
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FishHog
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# Posted: 17 Oct 2018 07:31am
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Quoting: neckless how do the lithium batteries work in -30 in a shed used on weekends
not well at all. Unfortunately that is one of the downsides of current day lithium. For that reason, I'm sticking with FLA's at the cottage in northern Ontario.
For my conversion van that I'm currently building I went with lithium. Added quite a bit more in initial cost, for the battery and the charging systems that I'm installing, but the weight savings and size made up for that in this case.
I'm still hopeful that as technology improves an even better solution than current day lithium will be available before I need to rebattery the cottage.
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creeky
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# Posted: 17 Oct 2018 10:35am
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Good grief.
I guess retail prices are higher in some places. If you look there are great bargains to be had. I have seen folks assemble lithium storage for less than the cost of lead. Its about the source. And I've observed a few good bargain hunters on this site.
There is no power in a FLA at -30. For solar most manufacturers recommend you don't use lead below -17C/0F.
You can use lithium with a 7% degrade at -25. Far superior to lead.
Keeping batteries warm is a simple two part equation. One, do you need it? If yes, build an insulated battery box.
Two. Put a thermostat and small heater in the box. Lot of us use battery warmers. Smallest we can find. If you're actually off grid. You'll warm your lead too.
The benefits are, imho, too great to ignore when it comes to cottage/camp/tiny home solar.
And its great to see all the folks going this way. Working in the industry I see and hear the stories. They are remarkably similar to mine. "Holy cow. This is much much better." Personally, at over 2 years on my lithium battery pack the benefits still surprise me. We've had an extra rainy fall with heavy cloud. Heavy cloud is no surprise. That's what we get here in the fall. Its just a month early. This has prompted lots of genny starting in my area. Guys have been scrubbing FLA terminals getting the corrosion off. Watering. Fussing with the charge settings. Ordering propane, filling gas tanks. Me, I'm just running my batts at 1/2-3/4 charge. No worry. My batteries will actual last longer. Maintenance = looking at the history on my bluetooth app.
Lead. Sheesh.
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offgrididaho
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# Posted: 17 Oct 2018 11:15am
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Don't think lithium is in the cards for me yet. I can get 6 golf cart batteries for $860 locally, that gives me 660ah (330 usable if going to 50% SOC)... it would take 3 100ah lithium batteries to match that, that's $3k, pretty big difference still.
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SCSJeff
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# Posted: 17 Oct 2018 12:19pm - Edited by: SCSJeff
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Sorry, if I derailed the OPs topic a bit
As prices come down closer to my budget on lithium, I'll seriously consider switching. Even though as ICC said, I'll have a considerable renovation to do (moving panels, inverter, auto-transfer switch, re-wiring main panel in cabin, etc.) Ugh, maybe not...
One advantage of having the power shed a fair distance from the cabin is the piece of mind of a fault (either in solar system and/or generator) starting a fire. Let the whole shed burn down without worrying about losing my cabin
But, it sure would be nice not worrying about off-gassing and having to re-water the batteries periodically.
ICC,
I am however amazed that (2) 12v 100 Ah lithium batteries can equal (4) 6v FLA Golf Cart Batteries (I'm guessing around 200 Ah each) in performance. I realize lithium can be discharged deeper, but that still seems like a big difference. Does your friend have them wired as a 12v system or a 24v? Would it matter much either way?
Creeky,
I looked up battery warmers on Amazon. Seems they pull about 80 watts. I could see on a not so sunny day, that I'd actually be pulling more out of the batteries than putting into them from charging. I guess I'd have to also invest in a battery charger to run off my generator too. That being said, it does seem as though it would address keeping the batteries warm in the shed.
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neckless
Member
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# Posted: 17 Oct 2018 02:12pm
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thanks to all the responce to -30 .i should maybe started a new thread lol
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creeky
Member
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# Posted: 17 Oct 2018 04:11pm
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Battery warmers start much lower. I bought 2 40w. I have my batteries in an insulated box. I run the warmers for an hour usually every 3 days. At -30 (we have cold winters) I may use 2 hrs daily. It does add up. However, when my FLA was at 0F I'd gone from 2.5kw of usable to 1.25 or less. And had to keep my batteries warm anyway.
Of course, with the terrible efficiency of lead I could run the dishwasher and warm the batteries up. smile. Can't do that with lithium.
There seems to be a misconception that FLA can be discharged to 50%. It can. But look at the mfct provided data sheet on aging. Discharging to 50% daily will greatly shorten the pack lifespan. Again, go look at the provided spec sheet.
The off grid standard is a 20% dod on lead.
There's a great primer on heat and cold effects on batteries here.
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ICC
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# Posted: 17 Oct 2018 05:02pm
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Quoting: SCSJeff amazed that (2) 12v 100 Ah lithium batteries can equal (4) 6v FLA Golf Cart Batteries (I'm guessing around 200 Ah each) in performance.
Here's the way I see it working.--- all batteries hooked in series for 24 volts.
two x 12 volt 100 AH lithium batteries, 24 volts at 100 AH, have a capacity of 2400 watts. You can use 70 to 80% of that and not be in trouble. 70% of 2400 = 1680 watts
four x 6 volt 200AH batteries, 24 volts at 200 AH, have a total capacity of 4800 watts. When I had lead acid batteries I would never plan on running them down more than 25% of their capacity. 25% of 4800 = 1200 watts.
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ICC
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# Posted: 17 Oct 2018 05:16pm
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And that capacity comparison is ignoring the fact that LiFePO4 can safely discharge or charge at higher rates than lead acid golf cart batteries, another + for lithium
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creeky
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# Posted: 18 Oct 2018 10:44am
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Quoting: ICC discharge or charge at higher rates
That is one of my favorite points about lithium. You can use high drain appliances (kettles, dishwashers, motors (start up surge), etc) all with no efficiency penalty.
I've posted this before, but the adv. of lithium are:
* longer life (NMC is now thought to have an over 20 year lifespan and at 70% dod even longer)
* proven less expensive by lifespan/charge cycle in 2013 by princeton university. prices have dropped since
* superior performance in charge discharge (peukert effect of 1 vs 1.3 for lead acid)
* lighter, smaller
* no managing toxic gases
* lower maintenance
If you're actually going off grid. And expect to use your camp/cottage etc for many years to come. There are two ways to go. Build cheap and repair. Or. Do it right the first time.
Lithium is like a good foundation. It pays long term. That you have short term benefits like being able to use regular appliances etc. Bonus!
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Ontario lakeside
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# Posted: 18 Oct 2018 11:47pm
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+1 for lithium here. Our part time cabin system is working great. In the winter we shut it down when we are not there. When we arrive on a cold winter day we turn on the supply from the battery and then the lights the fridge etc. start the fire and when the battery is warm enough flip the breakers to the panels and start charging. The whole thing is in a drawer inside the cabin.
https://www.youtube.com/watch?v=yCudeUYf52Q
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Wilbour
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# Posted: 19 Oct 2018 12:23am
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If you don't mind being creative and trusting others who know more, you can get set up with a better system for the same price as lead. If you like plug and play kits from a retailer you will definitely pay more for lithium.
I have a 1kw system that was made from parts sourced by a suppler who looks for deals all over. Each part is robust and efficient. Heck, it even has Bluetooth so I can monitor the whole system from my bed.
In the end I have a flawless system that is modular and a better understanding of what's what.
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offgrididaho
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# Posted: 19 Oct 2018 11:11am
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Wilbour, care to share what supplier you used? I am in solar siberia here (no local anything) so have no support structure to help me source anything other than advertised online plug and play with lots of shipping expenses. Part of the reason the plan is Deca golf cart batteries is because I can actually get them within a 2 1/2 hour drive.
-- Bass
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Wilbour
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# Posted: 19 Oct 2018 11:27pm - Edited by: Wilbour
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offgrididaho
Same supplier as Ontario Lakeside. If you hit his link he mentions the supplier. He is also on this site but is hesitant to advertise too much here.
He's located in the Ottawa area of Ontario.
This is my project https://youtu.be/XHpbI949rgE
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