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Discussion Starter #21
Wow - - 229 AHs . . . you're a man after our heart!

At last a direct answer! Thank you sir!

On our last build we cooked with butane and had a smaller fridge. The only real difference going forward is the single burner 1800w induction cooktop, and the bigger (but only marginally increased draw of the) fridge. The cooktop will be used to boil a cup of water twice each morning, and to cook pasta or rice or maybe reheat a slice of pizza or maybe to cook burgers or something like that. High draw but very limited duration.

If I take your point, I shouldn't concern myself with substantial losses from the inverter while, um, inverting. My thought was that I would actually have it conveniently switched such that it would only have power when in use.

If the published numbers that I used are accurate, and if the calculator that I used is correct, we'll probably be closer to ~190AH's most days, with 229 being an absolute -- but reasonably achievable -- outlier.

Before asking a few follow up questions and thereby shifting the conversation, I'm going to just sit tight and listen to the reactions to what I've written above.

Thanks -- all -- for sharing your experience.
 

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Discussion Starter #23
Humor me another question?

I'm still kicking around having a PV panel to keep things topped up. Just thinking long term -- that (without solar) if my alternator dies, not only am I not driving anywhere, but my house batts will die while I wait for rescue...

So I'm still kicking around the idea of solar.

In the past I've run 2 x 100w panels. Ideally I'd have a single, larger panel on this new build, for many reasons. Something like a single 300w (or so) panel.

Like (for example) this: LG NeON2 R Prime LG355Q1K-V5 355w Mono Solar Panel

I've noted that many of the 300w+ panels I've found are listed as 24v instead of 12v.

What sort of practical drawbacks does a 24v panel introduce to the equation? Can any charge controller handle the increased input, or do you have to spend more $ for a more capable controller?

Any other drawbacks?

Thanks again.
 

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Most mppt charge controllers can easily handle a 24 volt panel (although the voltages on panels aren't really like the voltages on batteries). You will want a mppt controller anyway. I don't consider higher voltage a drawback. In low light the panel has to be capable of exceeding the battery voltage to even start charging, so higher voltage panels (compared to the battery) are an advantage if you ask me... and you asked, maybe not me specifically. But that's my answer.
 

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Discussion Starter #25
Most mppt charge controllers can easily handle a 24 volt panel (although the voltages on panels aren't really like the voltages on batteries). You will want a mppt controller anyway. I don't consider higher voltage a drawback. In low light the panel has to be capable of exceeding the battery voltage to even start charging, so higher voltage panels (compared to the battery) are an advantage if you ask me... and you asked, maybe not me specifically. But that's my answer.

OK -- good to know about the low light benefit. No downside on the other end -- bright sunny mid-summer days cannot send too much juice into the system? The MPPT can handle/adjust for those?
 

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Most mppt charge controllers can easily handle a 24 volt panel (although the voltages on panels aren't really like the voltages on batteries). You will want a mppt controller anyway. I don't consider higher voltage a drawback. In low light the panel has to be capable of exceeding the battery voltage to even start charging, so higher voltage panels (compared to the battery) are an advantage if you ask me... and you asked, maybe not me specifically. But that's my answer.
Makes sense to me.

The Electrician at the boat store I buy stuff at told me the same thing and the reason why they "series" up the panels to get higher voltage. I will probably be setting up a bigger system in my cabin this summer and I am considering the 24V & Victron bluetooth mppt.

This is not my area of expertise, so I have to acquire the science and vet the information I research.
 

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Makes sense to me.

The Electrician at the boat store I buy stuff at told me the same thing and the reason why they "series" up the panels to get higher voltage. I will probably be setting up a bigger system in my cabin this summer and I am considering the 24V & Victron bluetooth mppt.

This is not my area of expertise, so I have to acquire the science and vet the information I research.
I get my victron gear from a boat store too, mostly internet orders, but I did stop by Annapolis MD and bought some stuff at their actual stop in March. I use a Victron Smartsolar 100/50 and it is easy to configure and use with the victron app. I currently have a grid tied system at my house and will likely use victron gear to add battery backup when I get the money.

Sounds like you are getting solid advice, I have 4 panels and purposely ran them in 2 in series with 2 series in parallel for the reason they are stating. I have gotten a little charging when parked directly under a light in a parking garage at night! nothing to brag about, maybe 0.2 amps, but without the series wired panels they wouldn't have reached a higher than battery voltage.
 

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OK -- good to know about the low light benefit. No downside on the other end -- bright sunny mid-summer days cannot send too much juice into the system? The MPPT can handle/adjust for those?
You have to watch the voltage, surprisingly it isn't the summer days that are the problem, it is the bright sunny winter days, because the voltage/temperature coefficient is negative, voltage rises when temperature falls. A 100 volt maximum controller should not have too many cells in series if used at very cold temperatures, a single 24 volt panel or two 12 volt panels in series will never be a problem for most controllers, but you have to look at the controller specs.

My controller is a Victron Smartsolar 100/50 which can handle 100 volts and 50 amps, both maximums. What the controller can handle will be part of its specifications.
 

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We agree that voltage is 'your friend'. But we wouldn't put them in series. We have three Kyocera 270 watt panels in parallel . . . they are 60 cell panels with an open circuit voltage even higher, 38 volts. We ran 'illumination' testing and discovered that 'shading' a very small percentage of a panel virtually shut the panel down. Running panels in parallel minimizes the negative consequences of shading . . . if one panel gets shaded (when in parallel), the remaining panels will operate normally. If in series, if any of the series panels are shaded, the entire series string is effectively shut-down.
 

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There aren't really 12v or 24v panels. These are nominal classifications. Try to become familiar with the full specs of the panels/controller. This stuff for the one you linked
Electrical Data
Nominal Maximum Power (Pmax):355 Watts
MPP Voltage (Vmpp):36.4 Volts
MPP Current (Impp):9.76 Amps
Open Circuit Voltage (Voc):43.1 Volts
Short Circuit Voltage (Isc):10.44 Amps
Module Efficiency:20.6%

As long as your panels are under the maximums for the mppt, you should be set. Most quality controllers will 'discard' excess energy without problem (within reason). Another important piece of info (if you can find it) is how much efficiency they lose as they heat up. Also be aware that the rated wattage is a maximum under perfect testing conditions. The quality of panel and the temperature, as well as sunlight, will determine final output.

I agree with Winston that although the higher voltages are beneficial, parallel setups allow panels to function independently and will probably be more rewarding in the long run. A mixed setup like jracca described is also good and higher voltage will allow smaller wire. It's that eggs in baskets thing. Almost always better to have multiple baskets.
 

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For me, the practical challenge of dealing with a single 24 volt x 300 watt panel is getting them up there without scratching the paint. It takes only the slightest breeze to catch a panel like that and make handling it on a tall ladder a real challenge. If you have an indoor location where you can lower it down onto the van, that is different. For me, the small cost savings of using one larger panel don't make up for the difference in risk related to trying to goof around with a single large panel.

My customers like to leave the refrigerator on all of the time so that they can have it cold and ready to go no matter what, even if they dont't drive all week. Especially along the west coast, it can be overcast - a lot. January / February can be brutal. For this reason, I would like to suggest 300 - 400 watts of solar panels to help keep up with the low light levels.

If you decide to use nominal 12 volt / 18 Vmp type panels in parallel, consider strongly to use a bogart pwm controller instead of an mppt controller. The bogart's will turn on under lower light conditions, providing charging much earlier in the morning and later in the afternoon than an mppt controller in that situation.

In the summer, the panels do a nice job of keeping it cooler inside from the shade.

Your power usage numbers look reasonable. From a battery perspective, low draw appliances like a refrigerator are very different than a high draw device like an 1800 watt cook top. The battery that we use for van applications is a lifeline GPL-27 or 31XT to deal with this wide range of power draw. For a 2000 watt inverter, 4 of them would be appropriate. Trojan makes great batteries, but the classic deep discharge Trojan is designed to power your refrigerator, not your inverter.

The reason for 4 of them is that if you look at the discharge curves of these batteries, 500 watts / battery is a good place to operate them.

Avoid renogy and aims / similar products and you should be fine.
 

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We agree that voltage is 'your friend'. But we wouldn't put them in series. We have three Kyocera 270 watt panels in parallel . . . they are 60 cell panels with an open circuit voltage even higher, 38 volts. We ran 'illumination' testing and discovered that 'shading' a very small percentage of a panel virtually shut the panel down. Running panels in parallel minimizes the negative consequences of shading . . . if one panel gets shaded (when in parallel), the remaining panels will operate normally. If in series, if any of the series panels are shaded, the entire series string is effectively shut-down.
I would not recommend 60 cell panels in series in a van either.

You are correct (of course) about the shading, but like most things its a trade off. If you have higher voltage panels its not an issues, but for 12 volt panels it has worked well for me, I have 4 panels total (and it is easy for me to change them around) and I get better results with two in series and the series strings in parallel than I get with all 4 in parallel. A lot depends on orientation and how likely shading is to occur. If shading is a big concern then parallel will mitigate that a little. But you give up some charging time (on 12 volt panels) when the voltage is not high enough.
 

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Discussion Starter #34
Thanks for the thoughts, people -- keep 'em coming.

To be clear, I'm looking at having one ~300w panel. In a bit of searching before bed last night I discovered that some places will only sell 300 (or 320w) panels in pairs.

Won't pretend to understand that, but will listen if someone wants to 'splain.

Will also consider ideas shared on where to buy a 300/320/350w panel. Would/will much prefer a black frame, strictly for purposes of vanity.

And I get that it's tricky to install a single larger panel, but it only needs to be done once, and great care can be taken in so doing.
 

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Generally solar panels are pretty cheap, often cheaper than adding battery capacity, but you have to price out the rest of the items as well. Do you already have a rack? There is also the added wiring and the solar controller. Do you have the space for extra batteries? It also depends on your use. If you are really always driving or plugged into shore power, it may not be worth it.

In our last van, and in this van because we already had the parts, we opted for 540w of solar into 3 x 100Ah lithium. We also used a microwave and induction stove and the other necessities (fans, heater, fridge, lights, devices, the f*ing toaster my wife just had to have, but which was actually pretty nice to have). We did also have a b2b charger. We were full time in the winter, including Canada in March and Alaska in April. For us the solar has always been a critical part of the system and it would be weird to go without it. I prefer not having to burn oil all the time to recharge the batteries.

Coincidentally, we just got the solar for this van finished yesterday. I will fully admit there are a lot of parts when you consider the rack, the entry to the van, the wiring, etc., but "free" power is so nice to have!

IMG_4970.jpeg
 

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Discussion Starter #36
Generally
Nice looking setup.

We won't have a rack, and the build is just starting so it'll be easy to make space for the batts.

Won't have shore power. With solar + a relay we've never, ever had a need. Have never camped in a campground, don't have any plans to going forward.

I considered spending the $ on lithium for the longevity aspect alone, but we live in the mountains of Idaho and it gets cold here. And we use the van all winter for winter sports. Keeping the batteries from freezing is more or less impossible -- indeed the batts will likely be frozen for a few aggregate months of every year.
 

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.....cut....
If you decide to use nominal 12 volt / 18 Vmp type panels in parallel, consider strongly to use a bogart pwm controller instead of an mppt controller. The bogart's will turn on under lower light conditions, providing charging much earlier in the morning and later in the afternoon than an mppt controller in that situation.
.....cut.....
Harry, on your 48V (nominal) van builds, what solar and battery arrangements do you normally recommend? Do you use 48V panels in parallel or lower-voltage panels in series? What about PWM versus MPPT? Seems higher voltages should make PWM more efficient than at low voltages provided panels and batteries are matched correctly. Haven’t seen technical papers on this yet.

Lastly, what about batteries? Are you using 12V in series or have you used any 48V lithium batteries, either large ones alone or smaller in parallel?

Options for electrical system design are changing so quickly — almost daily — that it’s difficult to keep up with the latest.
 

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Discussion Starter #38
Harry, on your 48V (nominal) van builds, what solar and battery arrangements do you normally recommend? Do you use 48V panels in parallel or lower-voltage panels in series? What about PWM versus MPPT? Seems higher voltages should make PWM more efficient than at low voltages provided panels and batteries are matched correctly. Haven’t seen technical papers on this yet.

Lastly, what about batteries? Are you using 12V in series or have you used any 48V lithium batteries, either large ones alone or smaller in parallel?

Options for electrical system design are changing so quickly — almost daily — that it’s difficult to keep up with the latest.

These are all compelling questions, but they also seem worthy of their own, separate thread to keep from confusing/cluttering this one. Thanks.
 

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Nice looking setup.

We won't have a rack, and the build is just starting so it'll be easy to make space for the batts.

Won't have shore power. With solar + a relay we've never, ever had a need. Have never camped in a campground, don't have any plans to going forward.

I considered spending the $ on lithium for the longevity aspect alone, but we live in the mountains of Idaho and it gets cold here. And we use the van all winter for winter sports. Keeping the batteries from freezing is more or less impossible -- indeed the batts will likely be frozen for a few aggregate months of every year.
Where? We have property on McCall we will eventually settle on. One of our coldest nights last year was on top of Banner Pass but the van stayed toasty inside!

Our primary use in the last van was winter living in ski area and backcountry parking lots. The van wasn’t empty for long, but you would be surprised how warm the electrical box stays for a while even with the heat off. Unless you are just parking the van and leaving it sitting in the cold, the system will usually stay warm enough. Lithium just can’t charge when frozen. Just being cold isn’t an issue. Anyway, sounds like you’ve assessed your needs.

For us shore power was always just backup so we knew we could plug in and have immediate power if we ever needed given that electrical was our only power source. We have a charger/inverter so the additional wiring is negligible. Without shore power I would definitely want at least one alternative charging source.
 

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Personally, I'd just paint the frame black than limit my search and/or pay a premium. 2 cents ain't much. No charge.

The series/parallel isn't any concern for a single panel. Just make sure panel is within specs of controller or the other way around depending on which you have now or get first. As far as I've seen anything that large will be over 12v nominal
 
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