Van Electrical system

[chris_van]

I am looking for advise on this system. I have ordered a ram promaster, which i'm told has been built but not shipped yet. All my devices will be 12 volt other than the hot water heater....but it will rarely be used because it is heated by the engine coolant. I've switched my plan from 6 12V to 48V lifepower batteries because i was scared of the high amperage....but I'm not sure if this is the right direction. Please let me know what you think. I also still need to figure out where and what fuses, and also grounding. My plan is to add solar after this is all built. (I am a total beginner at all of this) Thanks!

 

[AnarchyJet]

If you need 2000w of inverter I would stay 12v. A Victron Multiplus 3000va would handle shore power in, battery charging and inverting in one package. A DC-DC from the van battery to house bank is much more efficient than trying to invert 12v to run a 48 volt charger. Is the plan to keep the storage capacity the same at 28kw with 6 12v 400a batteries? Even if they only had 100a BMS's you could supply 600a continuously. 250 for the inverter and 120 for the other 12v loads still leaves plenty of head room

 

[jcbarr23]

I have a van in the driveway, but electrical isn't ordered yet, so not sure I'm qualified to offer advice, but a couple of questions:
1) Is the alternator dedicated or the regular engine one? If additional, you may consider buying a 48V version and getting more juice that way.
2) What's your expected daily load? 30kwh of storage is HUGE, and the recharging capacity you show has to run for over 13 hours to refill it. If you're only drawing a fraction of that each day and want the storage for many days off-grid, perhaps that makes sense.

 

[MisterSandals]

I've switched my plan from 6 12V to 48V lifepower batteries because i was scared of the high amperage....

Do you realize that this switch is an increase of capacity by 4x?

Messing with numbers:
48V battery x 6 x 200Ah = 57600Wh

Guessing RTX 2000 uses 2000W to run:

57600Wh / 2000W = 28 hours runtime for A/C

Lets say you somehow get 800W of panels on your van:

57600Wh / 800W solar = 72h to recharge from empty

I help a friend who has a pair of 200Ah LiFePO4 batteries in a Sprinter. These are a considerable amount of space and weight. I cannot imagine having 12x this much in either weight or size.

What is your daily energy use in Wh and how many days w/o sun or alternator do you want your battery to last? This is the time to do the math to not end up with a poorly sized system.

 

[Cal]

That's a lot of work going to a 48V system- just because you're concerned with large currents in a 12V setup? What about getting shocked from 50V? Any reason using a 1000W inverter to convert alternator 12V to 120Vac and then to 48V? What kind of efficiency do you expect? You can get a dc/dc converter (12V to 48V) and eliminate the inverter and charger.

The shunt in your diagram is not measuring alternator, as well as shore power charging.

Better make sure your vehicle can handle all that weight! That's a limiting factor for many builds.

 

[MisterSandals]

That's a lot of work going to a 48V system- just because you're concerned with large currents in a 12V setup?

Agreed, its a poorly thought out system. I count 6 devices that convert voltage and/or current.

 

[chris_van]

I am looking to run air conditioner for 3 days on the batteries. 6 48V 100AMP vs. 6 12V 400AMP. Also, i could not find a dc to dc charger that did 12 to 48. Please point me in the right direction if you know of a device. I believe the 6 batteries (regardless of the option) should be about 600 pounds....but this florida....flat driving, the weight should be ok. I can't see getting a big fancy inverter when i will not be using AC power 95% of the time. The Inverter will only be turned out a couple of days a year when it is freezing in florida. It sounds like folks think it makes more sense to go with the 12V batteries.....which would be 2400 amps in the total bank.

 

[chris_van]

forgot to mention alternator is the vehicle one, but ordered the upgraded 220 amp.

 

[HarryN]

48 volt is a good place for stationary applications as there is a lot of infrastructure and components available.

For mobile, 24 volt is usually a better choice unless you have a lot of experience. The electrical infrastructure for mobile is also mostly available in 24 volt and is less available in 48 volt without a lot of looking.

Nearly every device that you will want to power is available in 24 volt. Pumps, refrigerator, heater, lights, etc.

Every interesting brand offers inverters, 120 vac chargers, 240 vac chargers, and solar chargers in 24 volt.

The related fuses and breakers for this are also readily available in 24 volt on line, but harder to obtain in 48 volt. ( not impossible but will take a lot more time to find research )

So you will be down to just a very small number of 12 volt items such as the exhaust fan and perhaps not even that if you are clever.

________________________

As far as battery powered air conditioning, that will consume approx 1 kW average continuous regardless of how you power it.

For projects like that, I always add an auxiliary alternator. The standard alternator is not going to keep up with a load like that.

There are starting to be enough EV charge stations that it is interesting to think about if you can use this to charge up your battery pack.

 

[AnarchyJet]

I've switched my plan from 6 12V to 48V lifepower batteries because i was scared of the high amperage

I'm confused, if your primary loads are max 120 amp 12v and will rarely use a 2000w inverter, what are the high amps that you are afraid of?

 

[chris_van]

I'm confused, if your primary loads are max 120 amp 12v and will rarely use a 2000w inverter, what are the high amps that you are afraid of?

Hey, i was just afraid that my battery bank would be a total of 2400A. It seems like i'm reading that I only need to prepare for amps that will be pulled from the bank. So, that should not be more than 400A if all devices were powered at same time. (A/C, two 100 amp DC distro boxes, 2000 watt inverter -- giving everything 100amps is probaby way overboard) I also read that that would be split among the 6 batteries...so at most the batteries should send out about 70 amps each. So, i'm now leaning towards the 6 12V 400 amp lifepower rack batteries. Then i will use two 12v 30 amp chargers when connected to shore......and use two DC to DC 30 amp orions for charging while driving. Let me know if this doesn't sound good!!!!! The goal is 3-4 hot days in florida off grid in summer time. I think this should do the trick. Still need to figure out where all the fuses go and where/what gets connected to ground/van chasis. I would like to add solar next year.....but that can wait.

 

[chris_van]

One of my concerns with the 2400 AMPS total is that the victron shunts didn't go that high. So i've got to figure out how to take care of that. I do not want to buy and deal with an inverter when i really will hardly ever use anything but DC power.

 

[MisterSandals]

Hey, i was just afraid that my battery bank would be a total of 2400A.

You're confusing amps (current) with capacity (amp hours).

 

[Cal]

The primary reason for a higher battery pack voltage is to reduce current. The lower the current, the smaller the cables and less load on switching fets. The advantage goes to a 24V system over 12V.

How much power does the AC and other high-power appliances require? Have you done an analysis of how long the AC can run on battery without recharging?

 

[HarryN]

Regardless of what voltage you pick, air conditioning a van in FL in the middle of summer is going to use about 1 kW (averaged ) to power it, so:

( 24 hrs / day ) x ( 1 kW ) ~ 24 kW-hrs.

This is a reasonable, tested, first order estimate number that you can use to get in the ball park to see if the rest of your design makes sense or not.

_______________

Just to put this into a physical perspective, it is 24 each, 12 volt, 100 amp-hr, LiFe batteries for 1 day of air conditioning.

It does not matter all that much if you wire these to feed a 12 volt, 24 volt, or via a 120 vac inverter fed air conditioner. Some yes, but it won't change it by 50%. If it is hotter or cooler, more humidity or less will change it a lot, but not so much the air conditioner voltage. If anything, higher voltage to the compressor motor will make it more efficient.

For most people, having this much battery capacity in a van, much less 3x this much - is not really practical.

I will admit that I really like air conditioning and if you are just taking the edge off, you will get longer run time.

____________

So a more practical approach is to have perhaps 8 hrs of air conditioning battery capacity on board, along with something like a honda or yamaha 3000 generator. Every 4 - 5 hrs, turn on the generator and run it for 2 hrs to keep the pack charged up, then try to go all night with it off.

 

[MisterSandals]

I will admit that I really like air conditioning and if you are just taking the edge off, you will get longer run time.

So a more practical approach is to have perhaps

A refreshing voice of reason!

 

[HarryN]

Coming back to the core design that you have drawn - in general it is the same as what I do.

What I add is a breaker in between each battery string or load and the (+) bus bar. There really isn't any difference between a load and a battery. This makes it much easier to isolate and work on it.

 

[rustythorn]

Do you realize that this switch is an increase of capacity by 4x?

Messing with numbers:
48V battery x 6 x 200Ah = 57600Wh

Guessing RTX 2000 uses 2000W to run:

57600Wh / 2000W = 28 hours runtime for A/C

Lets say you somehow get 800W of panels on your van:

maybe the initial diagram was updated but i only see 100 ah batteries? assuming 50 VDC nominal that is still 30 kwh, which is the same size my second leaf battery [older leafs only had 24 kwh]. either way that is a lot of power is there a good reason to have that much storage?

also 800 watts on the roof is easy, 1000 doable and 1200 mostly feasible

 

[MisterSandals]

maybe the initial diagram was updated but i only see 100 ah batteries?

Yep good catch.

that is a lot of power is there a good reason to have that much storage?

Thats the question!

also 800 watts on the roof is easy, 1000 doable and 1200 mostly feasible

Ram Promasters aren't that big, with any vents or things on the roof, the real estate i think is the limiting factor.

 

[CaptainUnderpants]

Holy Sh!t Storm - That is a ton of battery power. I have 12v 600 amp hr battery for my RV and I thought this was on the bigger end of things. Your proposed system would be 4 times my battery pack. My recommendation would be to start with two 24v batteries, maybe two of them with 8 cells each. Each one will weigh around 110lbs. Mount any vents and air con units under the vehicle to max out solar at around 800-1000. And if that isn't enough as HarryN said, use a generator to keep the batteries charged. You could then use a Victron Multiplus 24v inverter charger and depending upon your alternator power Sterling makes a 12v to 24v B2B with 120amps capability. However, I am not sure if these two products would keep pace with the level of charging you need. What you are trying to do is solve for continuous AC usage. Most peoples answer to that is shore power, not boondocking battery power.

The big question will be how many hours of driving will you be doing in between how many days of air con usage. It sounds like you are new to this type of situation. Often times it takes some real world usage to determine correct sizing. Hence the recommendation for a smaller, yet still quite large, system that could be scalable.