Thinking of skipping solar and upping the lithium bank.

[Wrinkledpants]

Hello all. First post here.

Been reading a lot of the threads on lithium and am pretty excited that folks are having great results with it. We're in the planning stages of a high-roof Sprinter 4x4 being built by Sportsmobile (aug 2017 build date). Our usage will be weekend trips to the mountains (Denver) and a few longer trips throughout the year. The van will mostly be our basecamp as we climb, ski, and bike. With our 144WB length sprinter, a shower/bathroom, and a width-wise dinette at the rear to maintain the ability to walk-through, interior space is going to be a premium. It's rare that we'll be in a campground with a plugin. Lithium has an appeal in that we'll need 48 hours of battery capacity to maintain heat in the van during high-alpine trips in the winter (we'll have water tanks mounted inside). Between the induction stove, heater, fridge, and typical laptop use, it would be extremely difficult to do with AGM's given that many of these weekends will involve fresh snow covering the solar panels and temps below zero. We simply won't have the available payload for a larger AGM bank and can't run a generator if we want to stealth camp. This isn't a problem with fast charging lithiums mounted internally.

We'll have roof AC and a fantastic fan with the roof rack containing openings for them. Since we're going to be utilizing the roof for a lot of our outdoor gear and recovery gear (maxtraxs, come-along, axe, shovel, etc), we're going to need every bit of space we can get up there. We don't want a bumper-mounted box of any kind so we can swing the doors to the magnetic stops.

Given the amps that people are getting out of the 2nd alternator, the only time we could see needing solar are those long climbing trips where we're gone for 7-10 days but still want the fridge to run. A single panel could make that happen.

However, going with a 400 AH battery should get us a week of fridge use in hot weather. I don't know too much about what options are available for an auto generator start that would start the vehicle and let it idle, but even an hour of idling with a 300 AH lithium battery would get us 10 days running the fridge.

We don't mind idling the van periodically to recharge the batteries. And in reality, it's rare that we'll be sitting for more than 1 or 2 days as our camp locations are often different than the trail heads we need to get to. Driving somewhere for 10 minutes from our camp spot is pretty common.

For those of you that remain fairly mobil during your trips and have lithium, could you also see a point where solar may not be necessary? It's hard for me to wrap my head around the fact that a 100W panel will produce 30 AH a day in ideal conditions. That's 12 minutes at idle with a dual alternator setup with lithium. The money spent getting a solar option could be put towards more AH or saved for when the AGS systems are more plug and play. Without solar, we have a less complicated electrical system, more roof space, and one less controller to make room for inside. It seems like it makes sense to me, but given the fact that the rest of the class B community is so focused on solar, I feel like i'm overlooking something. The biggest panel we can fit is a single 160W panel. Two panels isn't an option.

Thanks, all!

[booster]

Solar doesn't make a lot of sense for you, as you will using a bit of power. 30ah is the high end and needs good sun, which you won't normally have if there is snow on the ground due to snow, sun angle, etc. Depending on how it is setup, lithium seems to be best with 10% unused capacity on both the top and bottom of the charge cycle, so you would net at 320 usable.

I don't think anyone has yet been able to tie and generator auto start type thing into a Sprinter to run the engine for unattended recharging. If you do the standard generator start setup, make sure you have the biggest shore charger you can fit, at least 100 amps, so you minimize the generator run time.

We assume propane or diesel heat?

Sounds like the cooktop would be your biggest load, probably by large amount.

[Wrinkledpants]

Thanks, Booster.

No propane. Heat will be either be a D5 (water and heat) or a D4 + 110V tankless water heater. We're leaning towards the D4 for simplicity, though. We won't have a generator at all. The isotherm 130 fridge has a fairly intelligent ASU that should help extend the battery charge during extended times away from the van.

Even if we have to wait a few years for someone to get the AGS tied to the motor, we would be willing to wait. Seems with more and more people going to a 2nd alternator, so I'm hoping that means more companies will explore the idea of an AGS using the engine.

[markopolo]

You might get some autostart ideas here: http://www.classbforum.com/forums/f5...tart-3913.html

Might as well save money there & start the van yourself when it is appropriate. If relying on an autostart for extended absences like the 7 to 10 days you mentioned then I guess one risk would be an empty fuel tank upon return if power consumption was somehow way more than anticipated.

There are car starters not in the list above that will start a car based on low voltage at the chassis battery and also temperature. The preset voltages are low imo - but it would be worth a call to a rep to discuss whether they can be customized.

[Marley]

Keeping the fridge running for 7-10 days while on a hike seems a waste of battery power. I would be more inclined to plan a trip to the closest store and restock (you will probably need to anyway for other supplies).

[Wrinkledpants]

Originally Posted by Marley

Keeping the fridge running for 7-10 days while on a hike seems a waste of battery power. I would be more inclined to plan a trip to the closest store and restock (you will probably need to anyway for other supplies).

That's always a possibility, but many of our trips will require another day or two just to get back to civilization. Some of the desert tower climbing trips will take a day of driving down forest roads, followed by several hours to the nearest grocery store (assuming it's open). The van will allow us to return from a trip, but not head home right away. It's true we could just pack non-perishable food, but the idea of burgers and cold beer waiting for us at the van is something that is important enough to us that we'd like to explore all the options that can make that happen.

[Wrinkledpants]

Originally Posted by markopolo

You might get some autostart ideas here: http://www.classbforum.com/forums/f5...tart-3913.html

Might as well save money there & start the van yourself when it is appropriate. If relying on an autostart for extended absences like the 7 to 10 days you mentioned then I guess one risk would be an empty fuel tank upon return if power consumption was somehow way more than anticipated.

There are car starters not in the list above that will start a car based on low voltage at the chassis battery and also temperature. The preset voltages are low imo - but it would be worth a call to a rep to discuss whether they can be customized.

Thanks for that link! There are some good ideas in there that should get us started. I would have never thought about looking towards the commercial trucking industry for this solution, but it makes sense that many of those companies have a more pressing need for this type of setup than the RV world.

[BBQ]

.

If you are thinking about extended boondocking (over 1 week),
you must ditch the Dometic and go for either an ARB Fridge Freezer or a Whynter Fridge Freezer. They do not draw much power, and are specially insulated for extended off-grid use.

[Wrinkledpants]

Originally Posted by BBQ

.

If you are thinking about extended boondocking (over 1 week),
you must ditch the Dometic and go for either an ARB Fridge Freezer or a Whynter Fridge Freezer. They do not draw much power, and are specially insulated for extended off-grid use.

I guess I would disagree. The ARB fridges are great and have used them many times. But, they simply do not have the volume for extended trips. We'll be getting an Isotherm 130 with their new ASU, and from the folks that have it, they report around 35 AH a day in summer temps. To go from 3-days of boondocking to 10 days seems more like a battery capacity issue, or finding a way to recharge them during that time. Lithiums can easily cover that power consumption if you have the space and cash for the batteries. Or, a single 160W solar panel will do it.

If we go with 3 Victron 160AH batteries, that will give us 11 days at 85% depth of discharge. The 2nd alternator will recharge that in 2 hours of driving.

This forum seems to have more experience with lithiums than other forums, so maybe I'm missing something? Our battery system will either be from Lithionics or Victron.

[hbn7hj]

Just an opinion but either go with a propane refrigerator or add solar. Go with max solar and max lithium.

Personally I'd go with propane and solar. It is a pain to keep the refrigerator level but it will do what you want to do. Planning to draw down a battery to 15% is a fools errand. Again, just an opinion.

[booster]

I would have to agree that if the van is going to sit that long with the frig running, counting on the batteries would not be my first choice, and at that point solar would be a good choice.

The power use of the frig can vary a large amount depending on the weather and how it is vented, so picking a single number for calculating run time can be very inaccurate sometimes. Our 3.0 Isotherm uses between 17 and 40ah per day in our use, so you will use more than that, I think. Your van will also be closed up, so if the frig is internally vented, like most OEM installs are and Isotherms like, you could have quite high temps in the van. The frig will add to this heat and be using it for cooling the condenser and compressor. All of this stuff will increase power use.

A 100 watt panel will give about 30ah per day in very good sun conditions, but can easily be under 1/3 of that in clouds and/or low sun. For that reason, don't use the recovery numbers, like the 30ah per 100 watts, that you are often given unless you live in the desert. Modify it with the anticipated conditions in the types of places you plan to go to. Often it is just best to go with the max that will fit on the roof of a B, as it doesn't cost much to increase it at the initial installation.

Propane is another possibility, but it would be my second choice, after a bunch of solar.