I agree with you, and yet I am installing 800 watts of solar and 540 amp hrs of battery. It all boils down to how much power you want to be able to put out, and how often (and how) you want to recharge.

In most situations, I expect that most mornings I will see my batteries at perhaps 85-95% charged (depending upon solar input) indicating an oversized system. But I did not size my system for "most" situations. I sized it to provide for air conditioning. Running an air conditioner radically changes how big your battery needs to be. If you operate in different environments where sometimes you need air conditioning and sometimes you don't, naturally the battery will be way oversized when you are not running air conditioning.

The other big determining factor is how often and for how long you drive (alternator charging). If you go from place to place every day, and have a decent alternator, you don't need any solar at all. If you tend to sit in one place for a long time without starting the engine, you need all the solar you can fit.

These are the two big factors: AC, yes or no? Alternator charging, how much and how often? Everything else pales in comparison.

 

These are the two big factors: AC, yes or no? Alternator charging, how much and how often? EVERYTHING ELSE PALES IN COMPARISON.

I think you are on to something...

Instead of one size fits all energy audit. Maybe there should be multiple options based upon these two factors.

 

If you were dying of thirst in a desert, how much would you pay for a gallon of water? Certainly a lot. How much would you pay for the second gallon of water? Not as much. And then how much for a third gallon of water? Maybe nothing,

Herein lies the problem of determining "How much solar or battery is NEEDED". For starters my van has 230 watts of solar and 300 amp hours of battery. I debated about upgrading to 600 amp hrs for a cost of around $3,000 and ultimately chose to hold off on the second battery.

On a two week trip back east through the southern / warm part of the US, my battery never got below 60% on an overnight basis, while boondocking. The major draws were an induction cooktop and a microwave. Never did I boondock for more than one night and was always back on the road with alternator replenishment through a 60 amp B2B charger. Most nights were spent in an RV park. Could I have used a second battery or 500 watts of solar? Yes, this would have given me more capability to run the air con. But other than running air con while boondocked, the extra solar or 2nd 300 amp hr battery would have gone unused. So I won't boondock in the desert during the summer, but I wasn't going to do that anyway.

Often on these forums I see a commitment to oversizing systems based up a black and white energy audit / worst case scenario. If you are living in your van, then maybe this strategy should be used. However, the "Law of Diminishing Marginal Returns" method should more likely be a method used for sizing electrical needs.

An analogy - "How valuable is 300hp and 400 ft lbs of torque in our vans?" I would say very valuable. Yet if we were to double this power rating to 600hp and 800 ft lbs of torque, would it make our vans any better? In my opinion not really and potentially worse. While I could use more battery power and solar, in my case, the 230 watts and 300 amp hrs has served 98% of my needs.

I raise this issue because I did stress quite a bit about my underpowered 230 watts of solar and my marginal 300 amp hours of battery, when the perceived standard is 600 amp hrs and 800 watts of solar. I don't stress anymore, even though some day I may upgrade to 600 amp hrs of battery. The solar I will probably leave as is.

300 ah? i assume this is a 12v system? you might want to include that or talk about kwh. i would agree that $3000 for 3.6 kwh is not great, for example you can get 5.1 kwh for $1500, however, while your advice is useful, each person's setup is different and your view points are best used in the context of ICE van conversions with propane. having multiple fuel sources will allow you to choose which power source will be the biggest pot. if you don't have an ICE or propane it will greatly change the calculations.

 

Although Lithium batteries are capable of being drawn down to 80% routinely, they may last only half as long as if they are drawn down to only 50% depth of discharge. This is from Victron's lithium battery data sheet:

Similarly a larger battery system can take more amps of charging without overheating or having other issues. And there is a similar longevity issue on the charging side.

So when a battery system is "oversized" from a draw-down perspective, it may be right sized from these other perspectives. For example, my batteries are rated to take 200 amps of charging continuously, and my Multiplus and solar together can deliver 165 amps of charging. So I'm slightly oversized, or you could say that I have a small safety margin on the charging side.

 

Although Lithium batteries are capable of being drawn down to 80% routinely, they may last only half as long as if they are drawn down to only 50% depth of discharge. This is from Victron's lithium battery data sheet:

View attachment 178212

It's worth noting that, as an example, if you use your van every single weekend for a year, that would be 52 X 2 = 104 cycles per year. Even at 3000 cycles, that would still be 28 years of use. AND, this chart does not represent the end of the "life" of the battery, but rather how long it will be capable of operating at 80% of its initial capacity. So even after 3000 cycles at 70% depth of discharge, the batteries could still retain 80% of their original capacity.

 

I do enjoy reading about the contest to build the largest electrical system ever installed in a van. A new winner every week.

As a reference I have a 255 amp-her 12 volt AGM battery and 300 watts from a single solar panel and have no need for more capacity. Seldom even need to charge from the vehicle using my backup method of charging if weather conditions force its use. Backup is a 1000 watt vehicle powered inverter that can power the shore power charger with engine running. I can be off grid for weeks.

I have a 85 liter refrigerator, "600" watt microwave (actual 950 watts), e-bike charging, electric shower water heater, 1/2 hp portable air compressor, 1000 watt vehicle powered inverter, 1000 watt house inverter. charger/transfer switch and the usual lights and device charging.

What I do not have is AC, induction cooktop, TV, music or a traditional cabin heater. I do not use the van in extreme weather conditions.

Typical day is getting to 100% SOC somewhere between 10 and noon. Overnight I use 5% of the battery capacity. 4% is the refrigerator and 1% is used by multiple electrical items that require power to operate.

There are two methods to determine the size of the electrical system required. One is to build a large system that covers any possible electrical use and the second is think about minimizing the amount of power required. A smaller system costs less, weighs less, requires less space, fewer connections to fail and is simpler to install.

Some of the things done to reduce the power required:

1. Only turn on the house inverter when I need 120 volt power. Why waste battery capacity when power not used?
2. Bought a Vitrifrigo refrigerator that uses 1/3 less power. Vitrifrigo has a radiator & fan condenser instead of a coil on back of the refrigerator.
3. Use a 12 volt heating pad to stay warm at night. No noise. Low power usage because refrigerator runs less in a cold van which offsets the pad power usage. Best to heat the person and not the van. Warm van in morning before getting out of bed by using remote start with dash heat and powering a 750 watt electric heater with vehicle powered inverter. Engine runs for 15 minutes.
4. Use a two burner portable propane cook stove.
5. Only turn on the light where I am located instead of lighting the whole van with multiple lights.
6. Added 2 1/2" of additional insulation around the refrigerator.
7. Only heat 2 1/2 gallons of water for a shower.
8. Do not store heated water.
9. Only heat the water to desired shower water temperature instead of high temperature water mixed with cold.
10. LED lighting. Limited the number of lights.
11. Use a high voltage solar panel with a MPPT controller to convert the high voltage/low amperage to charging voltage/higher amperage.
12. Add a floor hole for cool air intake and exhaust through open unpowered roof vent. Warm air rises.

Size of electrical system required depends on how it is used. Low power system may not fit every person's needs but can work well for many.

 

I do enjoy reading about the contest to build the largest electrical system ever installed in a van. A new winner every week.

As a reference I have a 255 amp-her AGM battery and 300 watts from a single solar panel and have no need for more capacity. Seldom even need to charge from the vehicle using my backup method of charging if weather conditions force its use. Backup is a 1000 watt vehicle powered inverter that can power the shore power charger with engine running. I can be off grid for weeks.

I have a 85 liter refrigerator, "600" watt microwave (actual 950 watts), e-bike charging, electric shower water heater, 1/2 hp portable air compressor, 1000 watt vehicle powered inverter, 1000 watt house inverter. charger/transfer switch and the usual lights and device charging.

What I do not have is AC, induction cooktop, TV, music or a traditional cabin heater. I do not use the van in extreme weather conditions.

Typical day is getting to 100% SOC somewhere between 10 and noon. Overnight I use 5% of the battery capacity. 4% is the refrigerator and 1% is used by multiple electrical items that require power to operate.

There are two methods to determine the size of the electrical system required. One is to build a large system that covers any possible electrical use and the second is think about minimizing the amount of power required. A smaller system costs less, weighs less, requires less space, fewer connections to fail and is simpler to install.

Some of the things done to reduce the power required:

1. Only turn on the house inverter when I need 120 volt power. Why waste battery capacity when power not used?
2. Bought a Vitrifrigo refrigerator that uses 1/3 less power. Vitrifrigo has a radiator & fan condenser instead of a coil on back of the refrigerator.
3. Use a 12 volt heating pad to stay warm at night. No noise. Low power usage because refrigerator runs less in a cold van which offsets the pad power usage. Best to heat the person and not the van. Warm van in morning before getting out of bed by using remote start with dash heat and powering a 750 watt electric heater with vehicle powered inverter. Engine runs for 15 minutes.
4. Use a two burner portable propane cook stove.
5. Only turn on the light where I am located instead of lighting the whole van with multiple lights.
6. Added 2 1/2" of additional insulation around the refrigerator.
7. Only heat 2 1/2 gallons of water for a shower.
8. Do not store heated water.
9. Only heat the water to desired shower water temperature instead of high temperature water mixed with cold.
10. LED lighting. Limited the number of lights.
11. Use a high voltage solar panel with a MPPT controller to convert the high voltage/low amperage to charging voltage/higher amperage.
12. Add a floor hole for cool air intake and exhaust through open unpowered roof vent. Warm air rises.

Size of electrical system required depends on how it is used. Low power system may not fit every person's needs but can work well for many.

again 255 ah at 12v? so 3 kwh?

as for the winner of largest battery, at the very least i expect to have a 110 khw system but i could go as large as 170 kwh possibility even above 200 kwh

 

I am going with 200w of solar and 2 206ah 12v batteries, along with a b2b charger. I was originally going to go without solar, but it was cheap enough to add and I figured it could come in handy if I want to sit in one place for a bit without driving. I have no air conditioning.

It definitely depends on your use cases, and I don't typically stay in one place while vacationing, so this works for me.

 

The region where you traveled and the season have a large impact on if a power system will work out for you or not.

In the southern US, there is rarely a shortage of sunlight in August for powering a refrigerator. Go a bit further north in the winter or hang out in an coastal area with morning overcast and see if you reach the same conclusion.

There is another aspect to this that is important so some, less to others. We have a fairly significant number of grid outages per year (fire season) so the power in the vehicle also serves to keep our home refrigerators running vs needing to buy a generator.

 

We can go 10 days on 12v/300ah. Charge via shore power and B2B only - no solar. (we're out in snow quite a bit) Propane stove and hot water shower. No induction cooker, microwave, AC or inverter. Light DC loads: fan, router, computers, espar heater, dometic fridge, LED lights, phone charger. Rarely used compressor runs off engine power. In winter we wear sweaters. Less gear -> easier maintenance, less clutter, lower costs.

 

You are just way to efficient.

 

"Law of Diminishing Marginal Returns"

Actually, diminishing marginal utility. , but yes ... point well made/taken.
Isn't the whole d@mn fancy camper van thing is an expensive lifestyle toy/choice for most/many?

As for me, I will be starting out with no A/C or heat and will chase moderate climates. Then upgrade, based on desire/benefit to add flexibility to travel area range and timing. Easier to "justify" marginal utility at that point. % incremental cost / % incremental use.

 

Ultimately, this would be the best way to design a system. Go out and use your van and then design / upgrade around your usage. Plus if you don't have the feature to use, you may find out you never really needed it in the first place.

 

If you were dying of thirst in a desert, how much would you pay for a gallon of water? Certainly a lot. How much would you pay for the second gallon of water? Not as much. And then how much for a third gallon of water? Maybe nothing,

Herein lies the problem of determining "How much solar or battery is NEEDED". For starters my van has 230 watts of solar and 300 amp hours of battery. I debated about upgrading to 600 amp hrs for a cost of around $3,000 and ultimately chose to hold off on the second battery.

On a two week trip back east through the southern / warm part of the US, my battery never got below 60% on an overnight basis, while boondocking. The major draws were an induction cooktop and a microwave. Never did I boondock for more than one night and was always back on the road with alternator replenishment through a 60 amp B2B charger. Most nights were spent in an RV park. Could I have used a second battery or 500 watts of solar? Yes, this would have given me more capability to run the air con. But other than running air con while boondocked, the extra solar or 2nd 300 amp hr battery would have gone unused. So I won't boondock in the desert during the summer, but I wasn't going to do that anyway.

Often on these forums I see a commitment to oversizing systems based up a black and white energy audit / worst case scenario. If you are living in your van, then maybe this strategy should be used. However, the "Law of Diminishing Marginal Returns" method should more likely be a method used for sizing electrical needs.

An analogy - "How valuable is 300hp and 400 ft lbs of torque in our vans?" I would say very valuable. Yet if we were to double this power rating to 600hp and 800 ft lbs of torque, would it make our vans any better? In my opinion not really and potentially worse. While I could use more battery power and solar, in my case, the 230 watts and 300 amp hrs has served 98% of my needs.

I raise this issue because I did stress quite a bit about my underpowered 230 watts of solar and my marginal 300 amp hours of battery, when the perceived standard is 600 amp hrs and 800 watts of solar. I don't stress anymore, even though some day I may upgrade to 600 amp hrs of battery. The solar I will probably leave as is.

One size doesn't fit all. Your size fits your needs. Mine fits mine.

You did say full time van lifers need more than weekenders, so I think we agree in principle.

But it's also a matter of geography, comfort, and convenience.

I like oceans and beaches, summer cliff jumping and pack rafting. I generally avoid cold places. But that comes at a price -- it's usually hot where I park.

I also like 24/7 climate control. But that comes at a price too -- even the most efficient a/c uses a lot of power.

A northern climate weekender who happens to travel a few times in a new rig when it's sunny enough for solar isn't going to have the same experience as a southwest climate multi-month traveler who sometimes has to park in the shade, or who experiences hot and overcast weeks during the monsoon period. Or even parked by the beach in Santa Monica next week:

I can have a wonderful time with the van parked on asphalt while I spend all morning playing in the ocean, and still come back to an ice box that afternoon and sleep like a babe at a chilly 68F in the van. That required a larger investment, but it was worth it to me because it's one of the many things in life that brings me joy.

There are benefits to a larger power system. It's not all hype or some false forum narrative.

Cheers.

 

Well stated.

I think the "energy audit" premise is frequently cited but should be focused more on the house environment, not as much van/RV. Yes, there should be a reasonable guess on usage - ideally backed by experience as in the last post... and even more-so based on actual data, not guesses.

The core questions should center on storage:

• how much energy usage per 24-hour period?
• how will that energy be restored?

Then that needs to be adapted to a year-round, likely-usage environment:

• will there be zero-sunshine periods?
• will there be zero-driving periods?
• will there be zero-shore-power periods?
• how long for each?

For fair-weather-only trips, lots of solar available. For winter-storm (or far north) trips, count on zero or near-zero solar.
Going to park without moving for a few days? Okay with running the engine for an hour or two or three? Or not? Or how much?

Last factor should be how much hassle does one want WRT energy usage?

• want it to be zero-interaction, just like at home - stuff always works and we ignore the system;
• willing to do whatever amount of interaction (turning functions on/off, etc) to preserve power.

We're sized for unlimited duration in good-sunshine travel.
We're sized for 4-5 days with low-to-mid sunshine with no engine.
2-3 days with no sunshine in the winter (need engine after that).

Our standard is, "leave everything on and don't think about it." But if we're in condition 2 or 3, those can both be extended by shutting things down at night, for example.

This will potentially change when we get the air-conditioning installed: possibly still unlimited best-case; dropping to 2-3 in the middle case; and the final remains the same because we'll never need the air-con in winter.

I've mentioned before... but our friend, Nick, is still just using a 60A DC-DC charger and a single 2.5kWh battery. He hasn't bothered with the solar because it has served fine so far. They're running a CFX95DZ fridge, propane oven, lights, computers, but not much else. No need for solar for them.

Focus on storage, not solar. How many days and how to restore the power used .

 

when we get the air-conditioning installed

Something to consider - 12V swamp cooler. Uses less power - essentially just a fan. Swamp coolers can work in dry/desert climates, but not in humid environments.

 

i might be wrong but i like to think my setup will not need much more than a "back of the envelope" estimate but that is a result of upper limits and my setup. i will be doing a 100% electric running only 120/240v and the 'house' battery will get all of its power from solar unless i'm "filling" up the van then i might get some shore power. in a pinch i could also draw power from the van's battery pack. while i know that solar is not always guaranteed, with a very large solar array i can still hit minimum goals even in cloudy weather. the size of the van's main battery will be anywhere from 100-200 kwh so i don't really need to go too crazy with the 'house' battery. i'm thinking 15 kwh might work but i might bump it to 20 kwh, however, much bigger starts to become a real size and weight issue. in short. i'm building the solar array large enough to charge the van in good weather which then translates to provide minimal life style power in bad weather. i'm looking at about 3000 watts of solar so even at 10% i can still run the AC/heater

 

Is this an EV van that will not use gasoline ?
This sounds very different from any other project. As a rough approximation, the max amount of watts that might go on a cargo van is around 1,000 watts. Will you have the panels stacked 3 layers deep and then slide out or unfold them like a giant butterfly ?

 

@davcenmt2 has or had a 1200w setup
Red Leader Build

 

@davcenmt2 has or had a 1200w setup
Red Leader Build
View attachment 178270

SO cool.

Here's @sYfte's 1600W:

 

You are just way to efficient.

Lots of backpacking experience. Vans are just steel tents.

 

The numbers I've seen for the full-size Transit Electric and the Lightning EV point to higher than 500 Wh/mi - up to 1 kWh/mi so would be on the right-hand-side of this graph. And the best MPG for an EcoBoost that I've seen here is 18 MPG, most are getting 12-14 loaded:

Ref:

https://avt.inl.gov/sites/default/files/pdf/fsev/costs.pdf

 

interesting graph, however, i don't see anything about transits or any particular EV in the article? and its not in watts/mile but i guess you could retro calculate it, but that seems like work that has already been done somewhere else?

 

another

 

An analogy - "How valuable is 300hp and 400 ft lbs of torque in our vans?" I would say very valuable. Yet if we were to double this power rating to 600hp and 800 ft lbs of torque, would it make our vans any better? In my opinion not really and potentially worse. While I could use more battery power and solar, in my case, the 230 watts and 300 amp hrs has served 98% of my needs.

I raise this issue because I did stress quite a bit about my underpowered 230 watts of solar and my marginal 300 amp hours of battery, when the perceived standard is 600 amp hrs and 800 watts of solar. I don't stress anymore, even though some day I may upgrade to 600 amp hrs of battery. The solar I will probably leave as is.

I went for a similarly 'small' system like yours (300Ah lithiums and 200W solar in a 12v system), despite the apparent race to much bigger systems.

I measured a typical days power usage at 80Ah - induction and instantPot cooking, plus kettle, laptop use, USB fans rather than AC, charging camera system etc...
So I figured 300Ah would allow about 3 days without relying on solar. My experience has shown how variable (disappointing) solar can be even in CA so I rely more on a 60A alternator charger.

It is pretty rare for me to be stationary more than 2 days as I tend to get curious about what is over the horizon. I also tend to follow cooler weather and park under trees (which is partly why my solar is made up of portable panels). After well over 100 nights in the vans 300Ah has worked well (100% ;-)) for me. I have only pulled out the panels twice for a top up, although wasn't actually necessary.

 

Diff'rent strokes for diff'rent folks.
People who have a lot of electricity demand and stay parked in one spot for a week or more at a time are obviously going to need a robust system. Some members have shared spreadsheets on how to determine use and needs to calculate ah and solar charging capacity. I think a lot of people are surprised to find they WAY over-estimated their needs. Designing systems for worst case scenarios rather than how it will be used 90% of the time is probably a money-waster. Yeah, on that one trip you might need 1000ah capacity, but just suck it up and face the inconvenience of charging your 300ah house system through the CCP once or twice instead of building a 1000ah, 1500w system.

I don't even HAVE solar modules

I drive my van nearly every day when out on camping adventures, so I just charge up with the alternator. And I don't have much energy draw; no microwave, water heater, oven, washer/dryer, independent HVAC, etc. just 12vdc fridge and sometimes a video monitor, and charging up devices and AA-AAA batteries.

 

People who have a lot of electricity demand and stay parked in one spot for a week or more at a time are obviously going to need a robust system. Some members have shared spreadsheets on how to determine use and needs to calculate ah and solar charging capacity. I think a lot of people are surprised to find they WAY over-estimated their needs. Designing systems for worst case scenarios rather than how it will be used 90% of the time is probably a money-waster. Yeah, on that one trip you might need 1000ah capacity, but just suck it up and face the inconvenience of charging your 300ah house system through the CCP once or twice instead of building a 1000ah, 1500w system.

I don't even HAVE solar modules

I drive my van nearly every day when out on camping adventures, so I just charge up with the alternator. And I don't have much energy draw; no microwave, water heater, oven, washer/dryer, independent HVAC, etc. just 12vdc fridge and sometimes a video monitor, and charging up devices and AA-AAA batteries.

What I read here about the size of electrical systems does not equate with what happens when I travel with my conversion. For some odd reason my use does not compare to others. I only have a single ancient design, heavy large 8D 255 amp-hr AGM battery and a single 300 watt solar panel with 15 amp MPPT controller.. No issues using van for as many days as I want without being concerned about running out of power.

I have paid attention to reducing power usage by making choices that require less power. Have not found those choices to cause any issues with using the van. My needs must be different than most others. I do have the luxury of living in a mild sunny climate so do not use the van much in poor weather conditions. Even overcast weather is not an issue.

What I do not have are: AC, induction cooktop, TV, Audio, outside lights, warm van at night, hair dryer, 120 volt power available full time, large number of lights all on, full time hot water, roof fan on, multiple solar panels for shade parking, etc.

What I have: ""600" watt microwave, 1000 watt house inverter, 85 liter refrigerator, propane for cooking, charge ebike, portable air compressor, 12 volt DC heating pad to stay warm in cold van, zero degree sleeping bag, backup bad weather charging from vehicle powered inverter, warm van in morning by running engine and electric heater, etc.

Normally in good weather I get back to 100% SOC each day so no limit on the number of days electrically.

 

Hi,
This is an interesting article that talks about some of the ways LiFePo4 batteries die.

One of the ways to decrease life is to store the batteries in a hot van fully charged. This chart from the article shows storing a battery at 90 to 100% SOC in a 100F van for 9 months
will permanently cut capacity by 10%. So, to me, it says parking the van in a hot driveway between trips in the summer could have you looking for new batteries in 6 or 8 years? I'm taking my batteries down to about 70% SOC between trips.

In the end, for typical RV service with so few cycles per year make the 5000 cycle kind of numbers meaningless - the batteries will die of something else long before you get anywhere near 5000 (or even 2000 cycles)?

Gary

 

exactly that is why i'm feverish about keeping my EV batteries from getting hot. i avoid 'fast charging', i avoid any charging if the EV is hot. i park in the shade, i have window shades and solar vents in the windows, etc... and my batteries last a lot longer than expected

 

Call me ignorant, a lot of people do, but is there a charge maintainer that stops the charging at a programmable level, like 80-90%? To maximize battery life?

 

Most charge profiles are still based on voltage as they have been for so long. In theory, one could use a very different profile for charging lithium really well - I'm pretty sure the EVs and even fancy phones with high-voltage charging use more than voltage - but most charging systems just use voltage. So... yes... sort-of. You've probably seen this before: the voltage numbers for lithium have a weird curve at the top.

So one could technically avoid the 14.6 or 29.2 rates that are often the recommendation for charging. For reference, Battle Born cites: Bulk/absorb = 14.2 – 14.6 V; Float = 13.6 V or lower. So... one /could/ use 13.4 as the charge rate... but from what I understand it will affect how the battery charges - won't actually reach the 90% SOC or something like that?

Maybe someone can explain it better... but what I've gathered, the gist is that charge curve makes it tough.