diy solar

diy solar

I need help.

According to @Luthj 's chart, at 12.8V you started with the battery at 17% SoC, which of 4800Wh is 816Wh. You used 400Wh overnight with the heater (is your heater really only 50W? Nice.) So with 416Wh left in the battery, you tried running a 1000W kettle. In just over 15 minutes, you are completely out. Any chance you can add an AirX or other small turbine for winter? Or are you going to be moving around?
 
Luthj said:
From the LFP voltage thread. This is roughly the correlation between resting voltage and SOC. 12.8V is pretty low SOC.

View attachment 23670
Click to expand...


I've seen that chart several times before and only just noticed the jump from 40% to 70%. I wonder if a bolder line between the two would make that plateau pop out more.
 
Yep... it's that damn flat curve and the low reliability of OCV as an indicator of SoC.
 
If you drive some, you can get decent charging from the alternator. Most newer vehicles can supply 50-100A above typical engine loads. Measure your alternator voltage at a hot idle. If its between 13.8-14.2V, you can probably charge directly from the alternator. Basically you need a split charge relay (just a high current NO SPST relay/contactor). I recommend something with at least 150A rated capacity. Bond your house battery to the chassis with a suitable ground/negative strap, then run a suitable (and fused at both ends!) cable from the house positive to chassis positive (through the relay). Wire the relay to close when the alternators D+ signal is active (ignition running control is available on most vehicles). When the alternator starts charging the relay will close, and you will charge the house battery.

There is some risk doing this depending on the vehicle, as older alternator designs can overheat if pushed hard. Though this typically isn't an issue. My 200A alternator will charge my 560Ah bank at 100A at hot idle. More if I am driving. Its the only thing that gets me through the winter when I am on the road.

If you have access to shore power, you can easily pick up a power supply that can be adjusted to 13.X volts (meanwell makes a 30A unit that others have used). Wire it in, and plug in to the nearest 120V outlet. Its a poor mans charger, but with lithium you don't need anything special for topping them off. Obviously you would adjust it lower if you are leaving it connected all the time vs charging a few hours a day.
 
I have to wonder if he needs to series his panels to produce sufficient voltage to charge the batteries during the day.
If they're parallel 12-17v panels they're not going to develop enough voltage differential to drive current except maybe for an hour or two in the middle of the day - and not much at that.

What panels are you using and how are they hooked up and to what charge controller?
 
Another option if not shore power is a portable panel tilted. Makes a big difference at large latitudes.

Putting panels in series, if using an MPPT controller, can sometimes provide sufficient voltage to increase harvest slightly. But the reality is, that Alaska just doesn't get much sun in the winter, and the low angle kills flat panel output.

The OP may be able to keep his heater and lights running from his solar array, but heating water and other high consumption items, may need to be switched to alternatives. Propane/butane stoves for example.
 
I've been to Fairbanks in mid-October. It's like late afternoon AZ sun, but it's all day... sun is shockingly low on the southern horizon.

Wintertime Solar in AK is fleeting.
 
SolarQueen said:
Even at 80 degree tilt, he's still in Alaska in the winter.

View attachment 23696
Click to expand...

Reality check - solar panels require direct sunlight to produce photoelectric power to their specification

The irradiance table give a good indication of when that will be

How much power do you estimate you will need through the winter? Have you calculated this properly yet? If you haven’t I recommend you do as it will give you good information to make decisions. Without this info you will waste time and money plus probably not solve the problem.

In an Alaskan winter you are going to need an alternative to solar because the sun doesn’t shine.

If you are regularly driving for long periods the alternator will provide some. It’s not very efficient to just run the engine but it does work. It’s not a good idea to connect lithium directly to the vehicle battery system. It can over work the alternator and burn it out. A dc to dc charger configured for lithium is a much better and more reliable solution. To prevent alternator damage (on OEM alternators) I use a rule of thumb of 1/3 of alternator rating for house battery charging. This should give plenty of room for the other vehicle loads the alternator has to supply.

If you are not driving lots then you will need to consider other charging power sources.

The most reliable is probably an inverter generator. What size will depend on how much power you are planning to use on average daily.

Let folks here know the details of your power use age, how much driving on average a day you are likely to do and your alternator rating and they will come back with good recommendations on how to ensure you have enough power for your van
 
I looked at the renogy combined solar and alternator charger. I figured it not quite powerful enough for my needs with only 25A charging from either solar or alternator.

Renogy have a range of cost effective dc to dc chargers that can be configured for lithium

www.renogy.com

12V 20A DC to DC On-Board Battery Charger

The best 12v battery charger. Free shipping. The DC-DC Battery Chargers are the most effective method to charge your home batteries from the starter battery
www.renogy.com www.renogy.com

Because it’s a van you’ve probably got an alternator rated around the 150 to 180A mark so the 40A will be fine

40A x 12V = 480W per hour. In reality it’s more than this because alternators produce more than 12V but if you work on 500W per hour it makes the maths easy.
 
Stephen Shreds said:
Was that the one you posted earlier? Are there any videos on setting that up? Seems there are a few options for me. Just which one is the right one.
Click to expand...

It's pretty straight forward. Pick the one that gets you the charge current you need and then it's basically a man in the middle. Chassis battery to the in and house battery to the output.
 
I've lived in Anchorage for 5 years, and you're all discounting just how well solar actually does in the winter. It's cold, and BRIGHT when sun shines which is most days, all the snow is VERY reflective and it stays there all winter so there's a huge amount of indirect light that'll also strike the panels. His 900W array should be producing a good deal better than it is. That said he needs a DC-DC charger from the alternator, needs more than 400 watts though or the engine will be running all the time.

Here is the Renology 50A DC/DC charger, there are others but this is probably simplest to install.

Edit, and a 60A
 
Last edited:
Options Summary:
  1. Alternator charging with Renogy or Victron Orion charger.
  2. Generator for AC power.
  3. Powermax PM3-12LV AC-DC 45A converter for charging from 110VAC shore power or generator (if you just want it for shore power, they go up to 100A, but anything larger than 45A will overload that small generator)
  4. Additional panels mounted on SIDE of van facing South (only a little boost)
  5. Superdy-duper sleeping bag that can keep you warm in AK's bone shattering cold (make sure you get one for the battery too).
  6. Drive South!
 
snoobler said:
  1. Superdy-duper sleeping bag that can keep you warm in AK's bone shattering cold (make sure you get one for the battery too).
Click to expand...
Darn, I didn't even think of that, you can't charge lithium below 32F (0C), so be sure to insulate the heck out of that bank, and maybe put a heating pad in with it.
 
Maast said:
I've lived in Anchorage for 5 years, and you're all discounting just how well solar actually does in the winter. It's cold, and BRIGHT when sun shines which is most days, all the snow is VERY reflective and it stays there all winter so there's a huge amount of indirect light that'll also strike the panels.
Click to expand...

Can you characterize how your system performed in those conditions? The irradiance website factors in weather, but I doubt it counts "reflection" - though I doubt snow on the ground would reflect up on to a flat roof of a van.

SolarQueen said:
Darn, I didn't even think of that, you can't charge lithium below 32F (0C), so be sure to insulate the heck out of that bank, and maybe put a heating pad in with it.
Click to expand...

If he can get enough charge to run the heater at night as he desires, I'm expect the battery temp will be fine.
 
You really need an accurate consumption budget to asses what your charging needs will be. Then you can work backwards to alternator or solar.

If your consumption is below your expected solar harvest, you may have some other issue in your system preventing charging. I suggest monitoring your PV output through a typical day, and get a handle on what you have coming in.
 
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