24V Lithium Solar Battery Build

Anyone have experience building a 24V solar pack using CALB LiFePO4 cells? I see there are kits available out there, but the only benefit I can see is the inclusion of copper busbars.

I am also curious about building some sort of enclosure to keep them warm, when ambient is freezing, and cool when hot.

Just looking for any suggestions, recommendations, etc.

TIA.

Dave

 

Why 24v?

Ive seen battery warmers or blankets, but they were all 120v. Im sure there are some out there that will run off a car battery and should last overnight with a deep cycle or lithium battery.

 

Posting to follow.

 

I don't know why, regarding 24V. I was just thinking to match solar array output to battery (24V). I guess using an MPPT solar controller/regulator is a solution.

 

I think I'm going to try to build a 12V pack first, then double it. Using this: https://www.dhgate.com/product/4pcs...MIwu_8_tCJ7QIVCQiICR367wY-EAQYAiABEgLQ4PD_BwE

 

What are you hooking up to it? Do you have 24v stuff? You can have more than 1 battery and still keep it at 12v depending on how you hook it up - series vs parallel. If you have 12v stuff, you half to step it down to be able to use anything. You can’t hook it up to your truck at 24v.

 

Timsp8 - this is travel trailer: hooking up AC unit, fridge, microwave, lights, tv,...... I was thinking that in general it was best to match solar panel, 350W 24V, to the battery. Thoughts?

 

The 24V panel has nothing to do with a 12V or 24V system. That 24V from the panel is the amount of power the panel is sending to the charge controller in full sun. Have you watched any of Will Prowse's channel?

https://www.youtube.com/watch?v=IRRKHYwB3Uo

 

will's awesome. i've learned a lot from him.

with regards to keeping the batteries warm, i'm waffling. i currently have a 170Ah lifepo battery in the bed. i haven't seen any drop in voltage yet but it's still been pretty warm during the day. i definitely didn't have any issues with overheating during the summer. there is a thermometer connected to my controller that helps regulate the trickle charge to the battery. if the panel aren't charging the house battery, they are trickle charging the starter batteries.

 

My setup powers deck lights, radio shack and man cave 50'' flat screen.

 

Wallygator - I have seen Will's videos....and they are good. My reference was this: https://www.loomsolar.com/blogs/collections/difference-between-12v-24v-solar-panels

 

I’d just say check those items and see if they are 12v or will work with 24v. Most stuff is 12v and will only work with 12v. Personally I’ve only seen 24v in the army and in tractors. My old rv was all 12v. There are lots of 12v solar systems that work.

From my research, it’s more about the battery ah if you want to run stuff a long time off grid. I think those lifepo4 batteries are 400 ah. 2 or 3 of those should run everything except ac and microwave due to start up voltage.

I also think solar is more about how many watts you can get to the batteries. It’ll probability take 300w+ to keep them charged, because a 100w panel won’t put out 100w to the battery if it’s cloudy.

You have to also match battery to the appliances.

 

I have three 100ah gel cell batteries, charged with three 100 watt panels fixed at 56o angle. It takes approx. 4 hours of direct sunlight per day to maintain batteries at 100%.

My current load per day and at 12 volts is:

Deck lights 40ah+
Radios 24ah+
Flat Scr TV 35ah+-
Total 100ah+-

I have no problem operating a 1200 watt microwave oven for short term cooking needs but it all depends on size and efficiency of your inverter. I use a pure sign wave inverter which enhances microwave use and for operating sensitive electronic devices.

I hope this helps.

Edit: My inverter is rated at 3000 watts

 

Thanks P-Factor for that info. My neighbor sells solar components and believe it to be 24V equipment as it is targeted a step above residential. That latter steering my strategy towards 24V and potential cost discounts. Re-thinking that, I would probably be better served to stick with 12V for all items: panels, charger/inverter, etc. All my needs are either 110 AC or 12V DC with biggest draw would be AC unit, when needed.

I am hoping that whatever I cobble together will give me unlimited off-grid capability - with mother natures cooperation.

 

12 or 24 volt systems is a simple battery parallel or series connection configuration. Most charger/controllers will operate and maintain your batteries with either voltage.

 

A decade ago I was really into flying RC planes, glow, gas, and electric. With electric (LiPo's) you had to treat the batteries with respect: don't discharge too quick, keep the temps down, don't discharge too deep, etc. I also noted during that time the performance of LiPo's in different temperatures where cold and hot ambient really impacted performance. I don't expect to have a rapid draw of Amps in my trailer, which I believe from my experience, to be the number one thing that destroys the life of Lithium based cells.

My purpose of this thread was two-fold - leaning on this community for some advice: 1) build a Lithium battery (12V). 2) build a battery case that maintained ambient temp near optimal without its own parasitic issues.

I have already started to mock up the case and it's already growing into one of those things I am famous for, analysis paralysis. I'll post some more on that tonight. I hate wasting time and perhaps I should not be too concerned about this ambient temp issue.

 

You are correct regarding the importance of charging correctly and not over discharging coupled with temperatures. A good charger/controller will take away most of your worries regarding these issues while charging according to type of battery and it will have a temperature probe for self adjusting charging voltage and impulse.

 

Equally important as well:
Solar Angle Calculator
http://www.solarelectricityhandbook.com/solar-angle-calculator.html

 

Prowse has a 12 volt vs 24 volt video that is pretty good. You can use a 24 v panel with a 12 V battery system and a quality charge controller

 

I have 2- 12v 100ah LiFePo4 in parallel, 4 -100w solar panels in parallel, 40amp charge controller with 1200/2400w inverter.

Solar panel is more inexpensive than batteries, so if you can top up quicker, the batter. But you still need the right amount of storage for evening and bad weather conditions.

The solar power calculator is a very good tool. It helped me a lot with my initial design. You just have to invest on reliable equipment for it to work properly. I discovered that my inexpensive 400w inverter running 3 wifi cameras consume more power than my 1200w.

There's a lot of off- grid you tube channels most of them are very usefully source of information. I take bits and pieces from them based on my needs and budget.

I will be using a 2" foam insulation with a 7.5 R value to incase my batteries or the whole compartment along with the charge controller, charger, transfer switch and inverter. I did not expect to move to a place when subzero temperature when I build my off-grid camper.

 

Sprinter - good info and thanks! Have you subjected your batteries to any extended subzero conditions, and if so, how did they perform?

 

19°F so far and was still holding charge. I'll remove it from my camper this weekend. I don't want it to get damage.

 

The BMS on the Battle Born batteries has protection built in for "too cold" (I believe it's 25 degrees or colder) conditions. The issue with it being too cold is you can damage the battery if you charge it during very cold conditions. Otherwise there should not be a problem with cold temps besides a slight decrease in capacity. I keep my Battle Born in the bed of the truck all year and do not ever plan to remove it because of the built in protection. I have spoken with Battle Born about this and they said it's ok. So whatever battery you choose if it has cold weather protection from charging it should be ok.