800AH, 12v or 24v?

[CluelessDIY]

I am new and bad with math and conversions! Please be patient. I believe I want a 600 to 800 AH LifePo4 battery system for "vanlife" part-time/potential to full-time. I possibly want a 5,000 watt pure sine wave inverter- but I'm not sure if that is overkill for my goals or will fit in the other parts of the system. I am open to all constructive criticism. I think I can use 12v appliances, but I am not sure exactly what limitations that holds yet. I am open to a 24v system. I am confused on how to fit the solar panels and related accessories into the equation from there.

Which might be better?

Should I do 2 smaller systems? (I am considering one solar system just to run a small AC full-time for pets since I plan on staying in some hot places)

What should I do if I want to upgrade later?

Thank you in advance!

 

[robbob2112]

General rule of thumb

12v - up to 3000w
24v - 1000w to 5000w
48v - 3000w and up

There is overlap because 24v is less common these days. Most small systems are 12v and large systems are 48v. Sometimes 24v still comes up if there is a deal on equipment or other special circumstances.

You can buy multi-voltage equipment so if/when you upgrade you can keep using it.

Start with what you want to use and for how long. This will suggest a voltage and from there the rest follows.

 

[740GLE]

Also be aware that AH isn’t the best thing to focus on when looking at 12v vs 24v.

600ah at 12v is the same as 300ah at 24v.

You can use KWHr for storage sizing until you sort out your native system voltage. I’m guessing you’re looking for about 6-8kwhr of storage.

That’s a single 280ah 24v battery at about 100-120lbs.

IMO 24 is the way to go.

 

[Rednecktek]

So van life throws in a fairly unique set of hurdles. Do you have any 12v stuff already installed? Do you really NEED a 5000w inverter? What kind of loads are you looking at that will physically fit in a van?

As an example, we had a member on here a while back trying to design a tiny home system. He grabbed the Power Audit form from the Resources section and filled it out a few times (do this first!!!) and kept coming up with nearly 10,000w of inverter. I pointed out that if he promised NOT to run the espresso machine, the frother, the microwave, the blender, AND the hair dryer at the same time, he was well covered with a 3000w unit. Thinking about the loads is critical, but so is how you're going to be USING the loads is also vital.

I have yet to see anyones build for a van on here exceed a 3kw system. That's still enough power to run a hot plate AND a mini-split at the same time.

The size of inverter you need is going to determine a LOT about the rest of the system. Physics is also a major factor because while 800ah of batteries and 4000w of solar panels sounds great, I doubt you have that much room to work with.

The other big concern is budget. How much can you realistically spend on just the power system after getting the engine tuned, new tires, furniture, bed, appliances, etc. There are some places you can shave costs (inverters, batteries, panels, etc) and some places you can't (converters, fuses, wire, breaker, etc) that all have to be balanced.

Another big hurdle is heat. When it comes to making anything hot (water, food, the living space, etc) the general concensus is "Anything But Solar" because heating things takes a lot of energy both in wattage for the elements, and capacity to keep pumping that wattage over time. Spaghettie-O's aren't as tasty in the dark. A recommendation for that (because I'm a whore) is a diesel parking heater. Yes, it may be another fuel you have to have, but a 5kw unit on low will cook you out of a van in nothing flat, runs on 12v power, and sips fuel. I've seen over 10 days on low out of some of mine on a single 5gal jug of diesel. Just a thought. As for cooling, a mini-split is WWAAYY more energy efficient than any of the roof mount RV styles unless you spend $$tupid money on one. If you can find a little 6kw somewhere that will likely be plenty, especially if you've insulated your walls & ceiling. A little complicated to mount some times, but works great!

Just a few thoughts off the top of my head.

 

[Stircrazy]

it depends on how you set up the rest of the electrical, if you staying with 12V apliances and thats it then stay 12V and cut out equipment you don't need, if you are setting up 120 stuff in adition to the 12V and have an inverter then as long as it is under a 3000watt inverter I would still stay 12V for storage. I personaly don't see an advantage to going 24 or 48V in a rv, UNLESS you for some reason need over 3000watts in the inverter and or you can't put your inverter close to the batteries. then the advantage of going 24V or 48V is only in being able to use smaller wires and save a bit of money with out as much line loss.

 

[CluelessDIY]

Also be aware that AH isn’t the best thing to focus on when looking at 12v vs 24v.

600ah at 12v is the same as 300ah at 24v.

You can use KWHr for storage sizing until you sort out your native system voltage. I’m guessing you’re looking for about 6-8kwhr of storage.

That’s a single 280ah 24v battery at about 100-120lbs.

IMO 24 is the way to go.

That's one of my confusing parts. I am planning on using 12v appliances with a step down on a 24v system if I go that way, would that effect it?

 

[CluelessDIY]

General rule of thumb

12v - up to 3000w
24v - 1000w to 5000w
48v - 3000w and up

There is overlap because 24v is less common these days. Most small systems are 12v and large systems are 48v. Sometimes 24v still comes up if there is a deal on equipment or other special circumstances.

You can buy multi-voltage equipment so if/when you upgrade you can keep using it.

Start with what you want to use and for how long. This will suggest a voltage and from there the rest follows.

Awesome! Thanks!

 

[CluelessDIY]

So van life throws in a fairly unique set of hurdles. Do you have any 12v stuff already installed? Do you really NEED a 5000w inverter? What kind of loads are you looking at that will physically fit in a van?

As an example, we had a member on here a while back trying to design a tiny home system. He grabbed the Power Audit form from the Resources section and filled it out a few times (do this first!!!) and kept coming up with nearly 10,000w of inverter. I pointed out that if he promised NOT to run the espresso machine, the frother, the microwave, the blender, AND the hair dryer at the same time, he was well covered with a 3000w unit. Thinking about the loads is critical, but so is how you're going to be USING the loads is also vital.

I have yet to see anyones build for a van on here exceed a 3kw system. That's still enough power to run a hot plate AND a mini-split at the same time.

The size of inverter you need is going to determine a LOT about the rest of the system. Physics is also a major factor because while 800ah of batteries and 4000w of solar panels sounds great, I doubt you have that much room to work with.

The other big concern is budget. How much can you realistically spend on just the power system after getting the engine tuned, new tires, furniture, bed, appliances, etc. There are some places you can shave costs (inverters, batteries, panels, etc) and some places you can't (converters, fuses, wire, breaker, etc) that all have to be balanced.

Another big hurdle is heat. When it comes to making anything hot (water, food, the living space, etc) the general concensus is "Anything But Solar" because heating things takes a lot of energy both in wattage for the elements, and capacity to keep pumping that wattage over time. Spaghettie-O's aren't as tasty in the dark. A recommendation for that (because I'm a whore) is a diesel parking heater. Yes, it may be another fuel you have to have, but a 5kw unit on low will cook you out of a van in nothing flat, runs on 12v power, and sips fuel. I've seen over 10 days on low out of some of mine on a single 5gal jug of diesel. Just a thought. As for cooling, a mini-split is WWAAYY more energy efficient than any of the roof mount RV styles unless you spend $$tupid money on one. If you can find a little 6kw somewhere that will likely be plenty, especially if you've insulated your walls & ceiling. A little complicated to mount some times, but works great!

Just a few thoughts off the top of my head.

I love this response! Thank you!

My ultimate goal is to use this system for now, and then add on to it in a permanent "home base" which will have more space (I'm hoping a few acres). One of the interesting things I'm looking at is using a dehumidifier to have some small source of water where it's humid. I am lucky that I don't cook much. I definitely was looking at a 12v minisplit for AC.

One of my quirks is i need hot water- i was looking at a submersible water heater- but I'm not sure if I can run the AC (about 1800 watts) and a hot water heater (about 2000 watts) at the same time as a dehumidifier (variable). So many things so consider, like you said! I'm afraid I'll fry something if I absentmindedly turn on a water heater, plus the AC or something. I guess that's what fuses are for!

I was considering towing behind like a power station setup on a trailer lol that would give more designated space for everything.

I appreciate your reply!

 

[Rocketman]

Let me give you my perspective- I full-time in a 36’ diesel pusher MotorHome (so “slightly bigger than a van).

My house battery is 544ah of Lithium 12v battery- I have a Victron Multiplus 12/3000 inverter and 1500w of solar.

I can run any one large item (microwave, hairdryer, air conditioner, toaster, electric water heater, electric heater), plus as many small items as are running ( Starlink, residential refrigerator, phone chargers, computers, etc.) at the same time.

One issue is I can only run the large items (air conditioner) for about an hour until the battery gets low enough that I need to either shut it off - so I can make it through the night or turn on the generator.

I have a large solar array of 1500w - you will not be able to fit that much on a van. During the summer that’s plenty of power - usually full by 2pm. During spring & fall - we are usually good. During winter in Arizona, I have to tilt my panels and then it is usually just enough. Any bad weather (clouds) or trees and we either need the generator or plug into the grid. I have propane for water heater, heater, and cooking.

Hopefully that gives you some thoughts on how to use and size your system.

 

[Rednecktek]

That's one of my confusing parts. I am planning on using 12v appliances with a step down on a 24v system if I go that way, would that effect it?

That can be done, but be aware that when a converter says 360w, it DOESN'T mean 362w. They have jack squat for surge so anything with a motor is going to nead a large converter(read: expen$ive) to handle that startup surge.

One of my quirks is i need hot water- i was looking at a submersible water heater- but I'm not sure if I can run the AC (about 1800 watts) and a hot water heater (about 2000 watts) at the same time as a dehumidifier (variable). So many things so consider, like you said! I'm afraid I'll fry something if I absentmindedly turn on a water heater, plus the AC or something. I guess that's what fuses are for!

Look into RV propane water heaters. Heating a tank with electricity takes a LOT of juice or a LOT of time. A little 7-10gal propane water heater will drop your solar requirements a significant amount.

It's the same with dehumidifiers. Those are horribly inefficient for making water and you still have to filter & sterilize after that. Condensate looks good but it's not good drinking as any gunk in the air (smog, pollen, exhaust fumes, Spagetti-O farts, etc) is condensed with the water and ends up in the tank.

1800w of mini-split is WWAAAYYY more than you need for a van, that's like a 24k BTU mini-split. A 9k keeps my cabin livable and it's about 4x as big as a van.

 

[Koyaanisqatsi]

Pretty much anything that generates a lot of heat needs to run on dinosaur juice. Just for a sense of scale, those absorption refrigerators that switch between electrical and propane need something like 300W when they run on electrical. But they use a tiny little pilot flame when running on propane and can last many days on a single tank. All cooking should use propane (or briquettes!). Electric hotplates look fun and convenient until you realize how much it kills your battery to run it. This leaves you with HVAC, microwave, coffee maker, hair dryer?, toaster?, maybe some other things that will need electricity to run.

And a tidbit of math to sort of give you some sense of the scope: Something that draws 1000W will drain a 12V/460Ah LiFePo4 battery in under 6 hours. 2000W in under 3hrs. And 3000W in under 2hrs.

 

[CluelessDIY]

That can be done, but be aware that when a converter says 360w, it DOESN'T mean 362w. They have jack squat for surge so anything with a motor is going to nead a large converter(read: expen$ive) to handle that startup surge.




Look into RV propane water heaters. Heating a tank with electricity takes a LOT of juice or a LOT of time. A little 7-10gal propane water heater will drop your solar requirements a significant amount.

It's the same with dehumidifiers. Those are horribly inefficient for making water and you still have to filter & sterilize after that. Condensate looks good but it's not good drinking as any gunk in the air (smog, pollen, exhaust fumes, Spagetti-O farts, etc) is condensed with the water and ends up in the tank.

1800w of mini-split is WWAAAYYY more than you need for a van, that's like a 24k BTU mini-split. A 9k keeps my cabin livable and it's about 4x as big as a van.

Awesome info! Thank you! I'm always worried I'm overestimating! For the AC, it regularly gets over 100 degrees outside, so I was trying to make the "easier" on the AC, if that makes sense? Would it even work that way, like in a house? The dehumidifier ideally would help with "washing" water. I really only drink from bottles/filtered would the dehumidifier help, or do you think "stealing" from a spigot/store would be better/more efficient?

 

[CluelessDIY]

Pretty much anything that generates a lot of heat needs to run on dinosaur juice. Just for a sense of scale, those absorption refrigerators that switch between electrical and propane need something like 300W when they run on electrical. But they use a tiny little pilot flame when running on propane and can last many days on a single tank. All cooking should use propane (or briquettes!). Electric hotplates look fun and convenient until you realize how much it kills your battery to run it. This leaves you with HVAC, microwave, coffee maker, hair dryer?, toaster?, maybe some other things that will need electricity to run.

And a tidbit of math to sort of give you some sense of the scope: Something that draws 1000W will drain a 12V/460Ah LiFePo4 battery in under 6 hours. 2000W in under 3hrs. And 3000W in under 2hrs.

I see! I'm trying to be minimal with electronics as much as possible like using manual coffee methods etc. Honestly, I could probably live without a fridge for the most part (debating on having a small one for guests). If I were to run an appropriate sized AC full time in the summer, how much power would that need alone? I tried watching YouTube videos but I can't seem to get that down in my head and add it to my other needs in a usable way.

 

[Rednecktek]

Awesome info! Thank you! I'm always worried I'm overestimating! For the AC, it regularly gets over 100 degrees outside, so I was trying to make the "easier" on the AC, if that makes sense? Would it even work that way, like in a house? The dehumidifier ideally would help with "washing" water. I really only drink from bottles/filtered would the dehumidifier help, or do you think "stealing" from a spigot/store would be better/more efficient?

Spigot and a larger holding tank is the way to go, or a 12v submersable pump and a clean creek. Running a dehumidifier eats a LOT of power, and dumps a LOT of heat into the van, so now you need a LOT of aircon to cool the place down which needs a LOT of energy.

Easy answer though, the process of coolingvthe air is what causes condensation, so just put the drain line from your mini-split to a tank and use the dehumidifying effect you already have. No sense dumping condensate out the drain and running a condensing air cooler (AKA Dehumidifier) and having to size that big.

Insulation is going to be the biggest thing. It's more cost effective to keep a space cool than it is to build a system that has to run all the time. I would look for a 6k -9k BTU inverter based AC mini-split heat pump so you can cool and heat from the same unit. More expensive up front but smaller power requirements and smaller space footprint needed to accomplish both goals (cooling AND heating).

I see! I'm trying to be minimal with electronics as much as possible like using manual coffee methods etc.

Still gotta heat the water, an electric kettle is 1500w. Propane and proper ventilation are a more functional cost-effective option.

Honestly, I could probably live without a fridge for the most part (debating on having a small one for guests).

Get a fridge, you'll use it. DC fridges are expensive and small but don't require AC power. AC fridges are cheaper and larger and since you are putting AC in anyways, might as well have a real fridge.

If I were to run an appropriate sized AC full time in the summer, how much power would that need alone? I tried watching YouTube videos but I can't seem to get that down in my head and add it to my other needs in a usable way.

It depends on factors like outside air temp, insulation, window space, etc. As small as a van is, anything over about 9k BTU (and maybe even then) may short cycle on and off a lot which beats up on the hardware (compressors, fans, inverters, etc). Inverter based is the way to go. They ramp up slowly so there isn't a huge surge starting everything up and if they only need to run at 17% (napkin math example number) then the compressor can slow down to 17% rather than ON AT 100% and off... and ON AT 100% and off..

 

[Koyaanisqatsi]

Inverter based is the way to go. They ramp up slowly so there isn't a huge surge starting everything up and if they only need to run at 17% (napkin math example number) then the compressor can slow down to 17% rather than ON AT 100% and off... and ON AT 100% and off..

I whole-heartedly agree with this. We have inverter-type heat-pump mini-splits (that's a mouthful!) in our house and they do sip power. The 18K BTU/hr unit upstairs keeps the room at 78degF when it's over 100 outside without breaking above 2kW. For a van, I'd say something like a 2.5K or 5K. But the smallest I can seem to find in a quick search is 9K and a few 6K units.

 

[Stircrazy]

I love this response! Thank you!

My ultimate goal is to use this system for now, and then add on to it in a permanent "home base" which will have more space (I'm hoping a few acres). One of the interesting things I'm looking at is using a dehumidifier to have some small source of water where it's humid. I am lucky that I don't cook much. I definitely was looking at a 12v minisplit for AC.

One of my quirks is i need hot water- i was looking at a submersible water heater- but I'm not sure if I can run the AC (about 1800 watts) and a hot water heater (about 2000 watts) at the same time as a dehumidifier (variable). So many things so consider, like you said! I'm afraid I'll fry something if I absentmindedly turn on a water heater, plus the AC or something. I guess that's what fuses are for!

I was considering towing behind like a power station setup on a trailer lol that would give more designated space for everything.

I appreciate your reply!

the problem your going to have is your not going to be able to install enough solar for what you want to do in a van. propane powered apliances will make your goals more realistic. just for the AC it will take a lot of battery and a lot of solare to make it able to run for a meaningfull amount of time. if you put in say a propane fridge and water heater, used a diesel heater for the heat that significantly lowers the amount of panels your going to need and prevents you having to tow a trailer of deployable panels. even then you still might want that trailer if you are going to run that ac for more than a couple hours if you think about it, and the ac is realy 1800 watts, then that 150AH per hour of running (aproximatly) so 600 - 800AH, if you run nothing else electrical, will give you 4 to 5 hours of AC (asuming a 30% duity cycle). But, you'll need to be able to produce up to 1.5x to 2x that with solar to replenish what you could use at night and run it during the day so you'll need a lot. this is why AC is usaly not a option for solar in RV's but some do it, you can do anything, how much do you want to spend.

 

[CluelessDIY]

the problem your going to have is your not going to be able to install enough solar for what you want to do in a van. propane powered apliances will make your goals more realistic. just for the AC it will take a lot of battery and a lot of solare to make it able to run for a meaningfull amount of time. if you put in say a propane fridge and water heater, used a diesel heater for the heat that significantly lowers the amount of panels your going to need and prevents you having to tow a trailer of deployable panels. even then you still might want that trailer if you are going to run that ac for more than a couple hours if you think about it, and the ac is realy 1800 watts, then that 150AH per hour of running (aproximatly) so 600 - 800AH, if you run nothing else electrical, will give you 4 to 5 hours of AC (asuming a 30% duity cycle). But, you'll need to be able to produce up to 1.5x to 2x that with solar to replenish what you could use at night and run it during the day so you'll need a lot. this is why AC is usaly not a option for solar in RV's but some do it, you can do anything, how much do you want to spend.

Thank you! That does make more sense. I'm not the best with math/conversions, so this does help! I'll definitely look into more propane things (luckily my dad has a 20 gal bottle I can have!)

 

[hardtop]

I'm an overlander and that is a lot like a vanlifer and find that a regular wall outlet amount of power in an apartment is all I need and that is 15A at 120V. I created a 12V 304AH battery with a 1kw Victron inverter. So realistically I couldn't do even 15A from the inverter (but can get 15A from generator). I bought the biggest Victron Phoenix inverter and its less than 15A for whatever reason. My BMS is 200A so I could upgrade if I wanted to run like a space heater (but I use a diesel heater).

 

[Frank Blue]

I second that.
We live on a 7m rv 6month a year (1kW continous power inverter and just 100Ah 12V lfp without desiring more, not kidding).
Going to 24V is such a pain that I would never do that.
Cables are short so is better to have 12V with double the amperes from batt to inverter than having a 24V battery and downstep all the rest to 12V.

 

[Dooug]

That can be done, but be aware that when a converter says 360w, it DOESN'T mean 362w. They have jack squat for surge so anything with a motor is going to nead a large converter(read: expen$ive) to handle that startup surge.




Look into RV propane water heaters. Heating a tank with electricity takes a LOT of juice or a LOT of time. A little 7-10gal propane water heater will drop your solar requirements a significant amount.

It's the same with dehumidifiers. Those are horribly inefficient for making water and you still have to filter & sterilize after that. Condensate looks good but it's not good drinking as any gunk in the air (smog, pollen, exhaust fumes, Spagetti-O farts, etc) is condensed with the water and ends up in the tank.

1800w of mini-split is WWAAAYYY more than you need for a van, that's like a 24k BTU mini-split. A 9k keeps my cabin livable and it's about 4x as big as a van.

I have no issues with the Victron 24/12/70 converter running my 4 camper jacks at the same time. Not unusual to have 450 watts steady, not counting start up current. The jacks LOVE the stable, 14.5v output of the adjustable converter. Most small RV jack systems will run off of a single 24/12/70. The larger 5th wheels likely need a pair of them. The cost of the 24/12/70 is very reasonable. The smaller units will run almost every normal small 12v loads in a RV. i have a 24/12/25 running the rest of my 12v system, it was $75 dollars. The big one was $155.

Totally agree on the propane water heater (and heater if needed). Takes a lot of watts to heat with electricity, more than are readily available to the RV world. I do keep a small space heater in my camper for cool days when hooked to shore power, otherwise it stays hidden away.




24v solar just needs to have enough panel voltage to start charger the batteries, often 5 volts more the the battery voltage. Not a big hurdle

Most lithium conversions use a DC to DC charger so a 12/24 charger is simple. There are limits to how big these get, easier to get bigger 12/12 converters at this time. Victron claims to be working on a 24/12/50 orion XS but no sign of it yet. Not sure if you had plans for DC charging.

If you plan on running Air conditioning for long periods of times, the 24v system will run cooler and be happier. If you end up with a small system, small inverter then 12v is the way to go.

Lots of great chat about inverter style variable speed compressor air conditioners. Limited options in the smaller units at this time, but small minisplits do exist. Recently came across a comment about how oversized units can have less dehumidifying effect as they have the cycle down more often. Havent done much digging into that, but it seems plausible. I am in the process of swapping my 14kbtu inverter window ac unit in my bedroom with the same unit in the 10k btu size and am very curious to see the performance differences. Might not find out until next year with the temperature starting to drop in baja. .

I'm going to reach out to furrion and ask about the teased 8k btu variable speed compressor air conditioner they teased last year. Its exactly what I need in my truck camper and would serve van lifers well too. They have the 18k btu model installed on new units only and it has great reviews so far. Really need some roof mount mini split style AC units to be developed.

 

[Frank Blue]

Hi Dooug,
why the system would be cooler, only the cables between batt and inverter will have double the amps (make them double and will be the same joule effect). The single cell will experience the same current (4s2p o 8s its the same, using 2 4s bms will be identical also from that point of view).
I am into this debate myself because also my home is mainly 12V and I am just about to assemble the battery system.
Up to know I decided that 24V battery is only an added problem (1-3kW inverter@12V is enough for my home).
I am open to change ideas if someone finds a scientific reason to do that.

 

[Stircrazy]

Thank you! That does make more sense. I'm not the best with math/conversions, so this does help! I'll definitely look into more propane things (luckily my dad has a 20 gal bottle I can have!)

20 gall bottles are fairly cheep at Costco for a new one anyways. you could even buy a small quiet generator for the days to help with the power when you run the AC. there are lots of ways to do it, you just have to figure out what works for you.

 

[Stircrazy]

Hi Dooug,
why the system would be cooler, only the cables between batt and inverter will have double the amps (make them double and will be the same joule effect). The single cell will experience the same current (4s2p o 8s its the same, using 2 4s bms will be identical also from that point of view).
I am into this debate myself because also my home is mainly 12V and I am just about to assemble the battery system.
Up to know I decided that 24V battery is only an added problem (1-3kW inverter@12V is enough for my home).
I am open to change ideas if someone finds a scientific reason to do that.

by going to a higher voltage, for you the only difference is it might be a little less line loss between the batteries and inverter. Myself I would be tempted to keep it 12V like you only for the 2 x 4s setup which will give you redundancy if one BMS dies. you will have less amps available but will still have power until you get the bms fixed

 

[Frank Blue]

I think we all agree on 8s vs 4s2p difference now. one is redoundant the other no, on eneed double wires batt ot inv the other no, one don't fail for a single cell fail the other does.

I noticed lots of verbs with future in it from the thread starter..
Best advice in vanlife world: start with the minimum to survive and build up as you understand your needs. People will only help you into building THEIR perfect van.
Don't spend money in ideas before, invest in your needs after you know them.

 

[wpns]

That's one of my confusing parts. I am planning on using 12v appliances with a step down on a 24v system if I go that way, would that effect it?

Consider that 24->12 converter to be just another inverter putting out a different voltage.

I’d personally go with 120v appliances.