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12v van-home battery bank?
#1
I'm a complete novice to everything electrical and was wondering if anyone could point me in the right direction as far as learning material for my project.

I'm currently building a camper/tinyhome van and I'm going to be using lead acid batts to start off. But what I'm wondering is, how reasonable is it to build a 200ah to 600ah lithium battery bank? Could it be as space efficient or more so? Would it require constant maintenance if it's homemade? I know this is asking a lot but if there's someone knowledgeable out there who can answer any of this id greatly appreciate it, even if it's simply to suggest I don't undertake this project.
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#2
Blunt response: did you even look at previous threads? This was literally discussed within the last couple weeks
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#3
Less blunt response - check the FAQ here and search for threads with similar getting started questions; you should be able to find the answers.

Personally I'd suggest spend a lot of time searching and learning so you can decide if it's the type of project for you. If you think it is, you might build a small 18650 pack while learning, but I'd go with batteries from electric cars for the main build. It'd be much less complicated / time consuming.
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#4
The other posters are right - this is covered many times on the forum. However, as someone who has gone down this EXACT road - don't do it.
Focus on your build - use 4 6v trojan batteries in series for a 24v system that is independant of your main 12v system (with the needed doodads to charge off your main alternator) and call it a day. At some point, it'll piss you off and you may go down the road of lithium - however it is honestly unlikely you'll get that angry at your lead acids. They are just soo much more foolproof and easy to get setup. There will be some sticker shock for the batteries but there are some things you can do: 1)Pay it and be happy, 2) Get recondidtioned batteries from your local reconditioner and waste a lot of time trying to figure out little issues all the time.

IF you ever get to the point where you feel like you need to spend way more money and go lithium (there are some advantages, but it's not worth it to start off with the most expensive and complicated system), get a 24v Tesla module pulled from a wrecked car and save yourself the insane headache that comes with going straight Lithium-ion.

I live in an RV fully off-grid and I have many friends who do as well. I cannot recommend going the lithium route at this moment because of the complexity that is involved. The benefits are weight/size as well as usable capacity. If you have 4KWH lead acid battery, you can ONLY use 1/2 of that because any more will damage your batteries. The same applies to lithium, but you can get more cycles out of them and you can do a couple other interesting things with them you can't do with Lead Acid. Start simple, deal with the bigger issues, and then you can pickup a hobby like a DIY lithium system later.

Also,

This isn't something for someone who is a novice. It's a PITA enough As-is to go the lead acid route, so definitely go that way first. You will learn a ton. Once you feel completely comfortable and you decide your power plant is the issue, then go the Lithium route first. Basically the lithium route has some advantages with the disadvantage of being much much more complicated and having the ability to explode in a fiery way, encasing you and your loved one in your tiny-home/campervan in a burning coffin.
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#5
It really does depend. You can get pre-built lithium packs with BMS - manufactured as drop in replacements for lead acid. However they are expensive. 600ah in lead acid is going to be big, bulky and heavy - however it is far cheaper and easier.

One advantage with lithium is it's cycle ability. Lead acid really doesn't like going below 50% depth of discharge.  Lithium can do 80%.

Check out the chart on page 7 of this white paper.

In short you should only pull 300ah out of a 600ah lead acid battery (50% depth of discharge). Where a 600ah lithium at 80% depth of discharge works out 480ah.

However that said - even though a lithium battery has 30% more usable power per cycle, they are usually more than twice the price!
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#6
It definitely has some advantages - but four 6v lead acids is plenty of power (I live on 2) , which is ~200ah at 24v, aka 4.8kwh (that's quite a bit). Lithium will weigh less, be more compact, and offer you higher cycle capability- but it's hardly worth it to start. 4 of those batteries isn't really that much weight or room, especially considering how important it is to your build-out. You can get premade solutions, but they are super expensive, especially since I can go down the road and get reconditioned 6v golf cart batteries for $60 a pop. If you invest in the 24v system now, which you absolutely should do, no matter how much you THINK you want a 12v system, - you don't need to throw anything away later to convert to lithium. I started with a 12v system for "simplicity" and now I have to replace almost $1000 worth of equipment to move to the 24v I should have started with because of all the little pain-in-the-butt issues that result from going 12v.
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#7
Mike, can you go into detail about the differences of the 12v and 24v system? And how it differs to install? I'm sorry if this is asking a lot but if you could explain it to me like I'm 5 that would be just amazing.

I've read about this stuff for hours and still don't feel like I understand any of it at all so hearing this stuff is super helpful
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#8
(02-08-2019, 05:06 AM)Manlycat Wrote: Mike, can you go into detail about the differences of the 12v and 24v system? And how it differs to install? I'm sorry if this is asking a lot but if you could explain it to me like I'm 5 that would be just amazing.

I've read about this stuff for hours and still don't feel like I understand any of it at all so hearing this stuff is super helpful

Put simply 24v has some huge advantages. If you are going to use an inverter it is a much better route. There is a much wider range of inverters at 24v or even 48v. The reason is the higher the voltage - the less current you need.

As has already been pointed out - it leaves options open for later on. If you start with lead acid at 24v, most 24v hardware is going to be compatible with lithium upgrades later on.

Unless you have the burning desire to uses existing 12v hardware - go 24v. However you can always use buck converters to run small 12v devices - such as LED lights - if you prefer to avoid the inefficiencies of using an inverter.

The only serious reason I can think of to go 12v, is if you have the desire to use a vehicles 12v charging system to charge your batteries.
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#9
Try to think through: are your devices all 12V?, could they be made to run on converters (as suggested above)?
What is your highest load going to be (wattage)?
What is your charging source going to be?

re Lithium, depends which Lithium chemistry you pick. LiFePo4 gives you nice 12V & nice 24V voltage matches but you don't find many 2nd hand.
If you want to use Li-ion LiCo, etc then 12V wouldn't be a good choice (poor voltage match), you'd go 24V from day one.
Maybe learn on lead acids, then jump into lithium.
With lead acid, make sure you ventilate the hydrogen & allow for water top-ups - or even a proper cell watering system.
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#10
For charging 24v off of a 12v system using a van's alternator:
https://www.amazon.com/dp/B07FCCLP83/ref...UTF8&psc=1
This should work at that current output, but it's still kinda iffy for continuous duty.

Be aware though that this should be going as an input into your charge controller - and a 50 amp charge controller is a big charge controller.

Most of it boils down to the efficiency, you can push way more power through smaller cables if you go with a higher voltage. 12v is really low voltage, and the amount of voltage sag you get over even modest runs is surprisingly high. With a 24v system, pumps etc run more efficiently, you can do everything with smaller and easier to route cabling etc.
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