Weekend only need for small cabin in Wisconsin (gets cold here).

[Supervstech]

lead acids worry me inside a cabin.
I know the sealed lead acids, or agm cels aren’t supposed to vent... but the possibility of overcharging or bursting one indoors... idk, I would have a steel battery box if indoors...

Propane isn’t cheap. Lead acid let’s you allow the cabin to remain unheated when you are away. The propane savings alone could pay for the battery replacements...

Lithium is cheaper from a lifetime standpoint, but keeping the cabin heated 24/7...

 

[SolarRat]

Others are mentioning this as well. I assume because of the cost and "if" they happen to freeze is why you mention? Thanks for your input!

In some scenarios lithium makes the most sense and is well worth the extra cost. In other cases, LA's are a better choice regardless of price. This is the latter.

Say you can't get up to the cabin for a few weeks or months. Life happens, sudden hospital stays, blizzards or storms, road closures etc happen. Will that propane heater still be running?

You are talking about 52 cycles a year max, so lead acids should last you a long long time, even if brought below 50%. But you could get 400ah worth of lead acid for half the price of BB's, so you may never need to cycle anywhere near that low. I'd bet the LA's far outlive the lithiums for your situation.

Lead acids like to be stored at 100% charge, which is perfect for a weekend cabin. Lithiums start losing lifespan when stored above 60% for long periods. Most manufacturers recommend only charging to 80-90% if used daily, but to drop it down to 40-60% when not being used for more than a week. Basically, you are aging your lithiums while not even using them if keeping them charged while you are not there.

I'd build a little "doghouse" for the batteries right outside the cabin, in the sun. Maybe a foot off the ground to get it away from the cold ground. One of those little Rubbermaid garden boxes would probably work OK if you aren't a woodworker. As long as you don't live in Siberia the LA's should be fine. You can keep a spare charged battery inside the cabin for backup for unforeseen problems like theft.

 

[salzbj01]

lead acids worry me inside a cabin.
I know the sealed lead acids, or agm cels aren’t supposed to vent... but the possibility of overcharging or bursting one indoors... idk, I would have a steel battery box if indoors...

Propane isn’t cheap. Lead acid let’s you allow the cabin to remain unheated when you are away. The propane savings alone could pay for the battery replacements...

Lithium is cheaper from a lifetime standpoint, but keeping the cabin heated 24/7...

Thanks. The cabin is pretty small and the propane use is minimal when I drop down to 50 when we are not there. Our pace is an hour away so it's nice to keep the core building a little warm upon arrival. I have owned for many years using 100lb propane and had left on often. Now with 500 gallon tank my plan is to just simply keep it on to keep a few things things from freezing.

Do I need to worry about the Battle Borns gassing and or have in a sealed box? Thanks again for all your help and input.

 

[salzbj01]

In some scenarios lithium makes the most sense and is well worth the extra cost. In other cases, LA's are a better choice regardless of price. This is the latter.

Say you can't get up to the cabin for a few weeks or months. Life happens, sudden hospital stays, blizzards or storms, road closures etc happen. Will that propane heater still be running?

You are talking about 52 cycles a year max, so lead acids should last you a long long time, even if brought below 50%. But you could get 400ah worth of lead acid for half the price of BB's, so you may never need to cycle anywhere near that low. I'd bet the LA's far outlive the lithiums for your situation.

Lead acids like to be stored at 100% charge, which is perfect for a weekend cabin. Lithiums start losing lifespan when stored above 60% for long periods. Most manufacturers recommend only charging to 80-90% if used daily, but to drop it down to 40-60% when not being used for more than a week. Basically, you are aging your lithiums while not even using them if keeping them charged while you are not there.

I'd build a little "doghouse" for the batteries right outside the cabin, in the sun. Maybe a foot off the ground to get it away from the cold ground. One of those little Rubbermaid garden boxes would probably work OK if you aren't a woodworker. As long as you don't live in Siberia the LA's should be fine. You can keep a spare charged battery inside the cabin for backup for unforeseen problems like theft.

Thanks Solar Rat. Propane heat should be good. I am looking into a cellular temp deal so I can monitor which others up that way use. If the batteries die from life happening our a heat outage after I do my best planning, I will consider it a lesson and get a couple more. Hopefully with the help here it will not happen form best planning.

Can I run a small fan or something to keep the LA's happy while away? I get the 100% deal as I drive a Tesla and same thing kind of applies. Or is this aging and my little use only slightly cutting the life of the battery? I would say 52 weeks a year is heavy, but I do spend lots of winter time there. Summer as well, but I'm usually outside and use much less power.

So you think LA's outside. I am very handy and could build a great insulated box. I was thinking of even a really good cooler with added rigid foam for Non- LA's. So if I do that with LA's does the charging and the sun keep them warm in average 15 degree temps? Great idea on a spare! I could use and old boat battery or something for that I assume.

 

[SolarRat]

15 degree temps is fine for lead acids, add a little sunlight heat and insulation and they should be very happy for a decade. LA's do temporarily lose a bit of capacity at real low temps but that can easily be made up by adding more in parallel. Some charge controllers, like Victrons, use a temp sensor to vary charge parameters to compensate for temperature, but LA's are very forgiving if your your CC doesn't have that feature. If you are going to be using power tools or drawing above 1000 watts I'd go with a 24v setup right off the bat.

 

[SolarRat]

Ya know, they should make "BMS's" with a sleep mode (i.e. when it hits a certain temp up or down it goes into sleep mode with no damage!

They do, but things don't always work as they should.

 

[PatBlack]

I recently installed an older model Nest thermostat that cost $169. It needs WiFi to work, and lets you control it from a phone app or a web browser. You could turn up the heat an hour before arrival, so if you have it at 50 normally, you just turn it up as warm as you want just before you start your drive to the cabin. It also has a "heat to this temp no matter what" setting in case you mess up on your programming, so nothing freezes. I have mine set for 45F. I don't think mine has an alert setting.

For alerts I use LaCrosse Alerts, really ancient technology that I wish they would update, but it works. You can set high and low alerts for temperature and humidity, and there's a model that also has leak/flood detection too. Super cheap solution you can find here. $46 to buy plus $1 a month for text and email alerts.

 

[PatBlack]

Lithium batteries do not vent. Sealed lead acid requires no maintenance and doesn't vent under any normal circumstances. Plain old LA requires some periodic maintenance to make sure there's enough fluid in them.

Here's a video on how one guy vented his batteries in his off grid cabin.

 

[salzbj01]

I recently installed an older model Nest thermostat that cost $169. It needs WiFi to work, and lets you control it from a phone app or a web browser. You could turn up the heat an hour before arrival, so if you have it at 50 normally, you just turn it up as warm as you want just before you start your drive to the cabin. It also has a "heat to this temp no matter what" setting in case you mess up on your programming, so nothing freezes. I have mine set for 45F. I don't think mine has an alert setting.

For alerts I use LaCrosse Alerts, really ancient technology that I wish they would update, but it works. You can set high and low alerts for temperature and humidity, and there's a model that also has leak/flood detection too. Super cheap solution you can find here. $46 to buy plus $1 a month for text and email alerts.

Thanks Pat. I am familiar with Nest and use it for my office and home. My problem is I do not have wi-fi and even a cell signal is rough. Looking at LaCross Alerts but it looks like this may need Wi-Fi as well. I dig deeper thank you!

 

[salzbj01]

15 degree temps is fine for lead acids, add a little sunlight heat and insulation and they should be very happy for a decade. LA's do temporarily lose a bit of capacity at real low temps but that can easily be made up by adding more in parallel. Some charge controllers, like Victrons, use a temp sensor to vary charge parameters to compensate for temperature, but LA's are very forgiving if your your CC doesn't have that feature. If you are going to be using power tools or drawing above 1000 watts I'd go with a 24v setup right off the bat.

I keep hearing about 24 volts. I'll need to look at Will's videos and see if I can find anything. I' a greenhorn at this and just began study over the holiday weekend. Now you have me thinking. I assume I can use the inverter, controler that i have ordered and simply use 2 batteries to go to 24? I need to study up, but appreciate your input!

 

[salzbj01]

I understand.

Maybe a separate compartment on the top whereby one could open it up, unplug the BMS and leave the batteries but take the BMS to a safer/warmer locale.

Or make them ROBUST!!!!

Yeah, I don't want to be lugging batteries. I'm an Army Airborne vet with a bad back and am sick of even carrying the Honda 1000 outside. I'm sure your idea would work for most!

 

[SolarRat]

I keep hearing about 24 volts. I'll need to look at Will's videos and see if I can find anything. I' a greenhorn at this and just began study over the holiday weekend. Now you have me thinking. I assume I can use the inverter, controler that i have ordered and simply use 2 batteries to go to 24? I need to study up, but appreciate your input!

The problem with 12v @ over 1000w is the amp draw, requiring much larger battery cables. 1000w at 12v is 83 amps, but it's only 42 amps at 24v. Your panels and charge controller will work with 24v, but not sure about your inverter, you better check that. Yes, you just wire two batteries in series. 2 12v 105ah lead acids would give you a 24v 105ah battery that holds about 2.5kwh.

 

[salzbj01]

The problem with 12v @ over 1000w is the amp draw, requiring much larger battery cables. 1000w at 12v is 83 amps, but it's only 42 amps at 24v. Your panels and charge controller will work with 24v, but not sure about your inverter, you better check that. Yes, you just wire two batteries in series. 2 12v 105ah lead acids would give you a 24v 105ah battery that holds about 2.5kwh.

Thanks SolarRat! I think I am going to shoot for a 24 volt system. I will study tonight! This stuff is so interesting. Sure wish they discussed solar back in my 1980 electric shop class. The basics are coming back to me on some of the lingo! Thanks for the info. I will follow up with plan B (24volt) soon.

 

[salzbj01]

Okay revising to 24 VOLT

I am will edit my initial post after I finish this post. I am going for the 24V system thanks to input I have received and some lunchtime research.

System Design:
-40 amp MPPT charge controller (Wills Favorite 40Amp)
-HQST 100 Watt 12 Volt Polycrystalline Solar Panel (I'm thinking 2 for now and may get two more if needed)
-2 Battle Born 100 Amp 12 Volts (wired in series)
-GIANDEL 2000W Pure Sine Wave Power Inverter DC 24V to AC120V with Dual AC Outlets with Remote Control 2.4A USB and LED Display
-Victron Energy Protect
-Bayite Display Meter

Question: Do I need a 24v>12V converter.

Thanks again and please let me know if I am missing anything. Do I need 4 panels? Again I can always fire up the old Honda 1000 if it rains all week etc. before I arrive. I can order the 4 panels if need be, I just don't want to have to build a big mount if unnecessary.

 

[PatBlack]

If you're doing 12v lighting or using other 12v appliances, yes, you will need a DC - DC step down converter and a 12v fuse block. I don't think those solar panels are going to work for your 24v system, but I'll leave that for the myriad of experts on this forum.

 

[Deleted member 783]

Just to stick some actual numbers to it, sealed lead acid batteries at 50% charge (or greater) can withstand temperature down to 5 degrees farenheit without issues. LiFePo4, as you know, cannot be charged below 32. If you get to your cabin and your LIs are at 31 degrees, you're screwed.

 

[salzbj01]

If you're doing 12v lighting or using other 12v appliances, yes, you will need a DC - DC step down converter and a 12v fuse block. I don't think those solar panels are going to work for your 24v system, but I'll leave that for the myriad of experts on this forum.

Currently do not use 12v anything. All 120ac. Thank you!

 

[salzbj01]

Just to stick some actual numbers to it, sealed lead acid batteries at 50% charge (or greater) can withstand temperature down to 5 degrees farenheit without issues. LiFePo4, as you know, cannot be charged below 32. If you get to your cabin and your LIs are at 31 degrees, you're screwed.

Thanks NM Will. I'm not worried about the freezing and will have heat.

 

[PatBlack]

from the battle born website:



Are there any temperature restrictions on your LiFePO4 batteries?

Yes, our batteries do have temperature restrictions. The batteries will no longer accept a charge once the temperature drops to 24 degrees F, but they will continue to discharge until the temperature reaches -4 degrees F. We do suggest insulated battery boxes, or heating blankets to help keep the temperature up on the batteries. As far as heat is concerned, the batteries will shut down once the temperature hits 135 degrees F.

 

[salzbj01]

from the battle born website:



Are there any temperature restrictions on your LiFePO4 batteries?

Yes, our batteries do have temperature restrictions. The batteries will no longer accept a charge once the temperature drops to 24 degrees F, but they will continue to discharge until the temperature reaches -4 degrees F. We do suggest insulated battery boxes, or heating blankets to help keep the temperature up on the batteries. As far as heat is concerned, the batteries will shut down once the temperature hits 135 degrees F.

PatBack, I read that as well. I think I will be good. I think making an insulated box makes a lot of sense to maybe save them should something happen. I like the heating blanket idea. I saw a video where Will was going to test a $39 version I think. Thanks for the feedback. I will keep the updates coming. I was hoping to start building the board this week, but now need to wait on 24V Inverter. I hope to be up and running within a few weeks.