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Designing car system for road tripping/camping - 12V or 24V?

Thanks for all of the information and feedback so far. Here's what I'm learning:
  • I have a power consumption problem.
    • I need more accurate estimates for anticipated loads. Ideally actual data.
    • I need to reduce consumption. Ideally below 1 kWh/day.
  • I have a charging problem.
    • Going to need shore, solar, and alternator charging if I plan to use 1.7-2.1 kWh/day.
    • Need to find 300+ watts for the roof, and another 300+ watts for ground deployment when stationary.
    • If I can get my consumption below 1 kWh/day, I think the situation is less challenging.
  • My inverter loads are driving everything else.
    • I knew this, but it was helpful to see the inverter characterized as an OPTION, not a DEFAULT.
  • I should stick with 12V if I can, because it's simpler.
  • I should try to solve the BMS sustained current problem with a better BMS/battery, not higher voltage.
  • If I go 24V, that's fine, but zero reason to go past that. I should still try to stick with 12V.
  • Given my expected AC loads, a 1800-2000W inverter would be best.
  • I should try to eliminate the need for the inverter. That also solves the BMS problem.
    • I should investigate 12V kettles and hair dryers and see if consumption is lower.
    • Even if consumption is the same or a bit higher, eliminating the inverter may still make that worthwhile.
    • If I can't eliminate the inverter, maybe I can greatly reduce the inverter size.
    • I should just punt on the kettle and use the propane stove we will already have to heat water.
Some other ideas:

I could make use of a smaller system (like the 640 Wh one I built) to charge phones and laptops and lights and such, leaving the big system to serve the fridge, kettle, and hair dryer. That smaller 640 Wh system would easily charge from 200W of solar most of the time. I'm just not sure if it makes sense to have two systems.

I could charge phones and lights off of a small USB power bank, and make use of a small folding panel to recharge that. When we're driving, they'll charge off the car anyway, and so could the USB bank.
 
A tiny backpacking stove will boil water very quickly... under 4 minutes per quart of water and would save a lot of energy usage. The fuel cartridges are pretty cheap, too, and last a long time. Generally, cooking and heating use a lot of power and are really best served by some other type of fuel.

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A Yeti cooler works as well as a refrigerator if you'll be somewhere with ice available once a week. It's a little more fuss but would cut way down on power consumption.
 
camelCase said:
A Yeti cooler works as well as a refrigerator if you'll be somewhere with ice available once a week. It's a little more fuss but would cut way down on power consumption.
Click to expand...
The Dometic has been a total game changer for road trips, and I'll never go back to a cooler with ice if I can avoid it. It's really really nice.

I agree on the stove. I'd done a brief calculation on what it would take to run an induction cooker on battery and noped out of that instantly. Was hoping the kettle would be viable, mostly due to convenience, but it is becoming clear that that isn't really feasible with my present constraints.
 
My brother has Kong coolers and swore by them. I said try a Dometic fridge and he too has been hooked ever since and bought 2!

24V has the advantage of smaller, more flexible wires which you’ll appreciate when it comes time to do the install.

I also noticed there are compact 0.5-1L 24V kettles available which may meet your needs. They take longer than 120V and gas but you don’t have the wind issues like some stoves have.
 
Atom Tan said:
I can probably reduce the laptop figures a bit. Say, 60 Wh/hr per laptop over 3 hours for 360 Wh/day vs 600. Similarly, I think I could reduce the USB QC figures a bit to say, 200 Wh/day. That would get "important" loads down to 900 Wh/day for a total of 1764 Wh/day.
Click to expand...
You are still using way too pessimistic fiqures or way too power-hungry equipment.

Typical 14" laptop battery today is 60Wh, charching it at 80% efficiency is 75 Wh per laptop per full charge. Yet again typical modern 14" laptop runs 8 to 10 hours per charge so unless you sit on laptop 24/7 one charge per day is probably (more) than enough

Same with cell phones. Iphone 8 for example has 7Wh battery, Ipad 33Wh. You don't have enough hours in a day to use phone, ipad and laptop battery flat. :p

Note: use 12/24v chargers for laptops and phones, inverter+phone charger is extremely inefficient combo.
 
Since the only load you absolutely have to use on inverter is the hairdryer you migh be able to get by with modified sine wave inverter.
Saves quite a bit of space, weight and money.

Too bad they don't make propane powered hair dryers :ROFLMAO:
 
MattiFin said:
You are still using way too pessimistic fiqures or way too power-hungry equipment.

Typical 14" laptop battery today is 60Wh, charching it at 80% efficiency is 75 Wh per laptop per full charge. Yet again typical modern 14" laptop runs 8 to 10 hours per charge so unless you sit on laptop 24/7 one charge per day is probably (more) than enough

Same with cell phones. Iphone 8 for example has 7Wh battery, Ipad 33Wh. You don't have enough hours in a day to use phone, ipad and laptop battery flat. :p

Note: use 12/24v chargers for laptops and phones, inverter+phone charger is extremely inefficient combo.
Click to expand...
I am definitely planning on 12/24V chargers.

I now see your and @kenryan's point about the inaccuracy of my estimates for phones and laptops more clearly. I will have to spend some time getting more realistic with those estimates.
 
MattiFin said:
Since the only load you absolutely have to use on inverter is the hairdryer you migh be able to get by with modified sine wave inverter.
Saves quite a bit of space, weight and money.

Too bad they don't make propane powered hair dryers :ROFLMAO:
Click to expand...
I mean, they DO. But you only need them once or twice!
 
Agree about the laptop power figures. I have a beefy Lenovo business class laptop that only draws about 20 watts while running in battery saver mode (fully charged), even though the adapter is rated at 60 watts.
 
Does your travel companion really expect to wash her hair very often where there isn't a bathroom? They do make cordless hair dryers, though they only blow warm air, not hot.
 
camelCase said:
Does your travel companion really expect to wash her hair very often where there isn't a bathroom? They do make cordless hair dryers, though they only blow warm air, not hot.
Click to expand...
A good point that I had not considered. Probably safe to assume an every other day use. For that matter, it's probably safe enough to assume that many places with a shower will have an outlet available for use. If we boondock and do jerry can showers, which we will, we can use the inverter in those cases. Maybe that gets us to twice a week as a pessimistic case.
 
camelCase said:
Agree about the laptop power figures. I have a beefy Lenovo business class laptop that only draws about 20 watts while running in battery saver mode (fully charged), even though the adapter is rated at 60 watts.
Click to expand...
Another comparision point:
14" Dell 7490 uses 4 watts to surf on diysolarforums and 6 watts playing Will's youtube videos. And this is something like 4 year old laptop already.
 
You are way over in your power estimation.
Stay with a 12v system.
Need a 1200 watt inverter, suggest Victron Phoenix Compact 12/1200.
AC charger, Victron IC 65 compact.
Engine charging, need a DC to DC charger, suggest Victron Orion 12 12 30.
Battery minimum 100Ah lithium with a 100A BMS, better, two off in parallel.
Don't worry about 3 days off battery alone. If low power stop inverter use, if battery low start engine.
Solar, whatever you can fit on the roof with a MPPT controller.

Mike
 
As a tip, you could change or add a second alternator.
If you run the engine while you use the blow-dryer, it would not use as much of your batteries...
 
Bergum said:
As a tip, you could change or add a second alternator.
If you run the engine while you use the blow-dryer, it would not use as much of your batteries...
Click to expand...
Adding alternators is a huge headache on a modern car where every inch of space under the hood is crammed full and the ECU controls everything.

For questions about that kind of stuff car audio forums are the place to inquire.
 
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