More solar. Less battery.

[user 423]

This past summer I've been using a 100w panel (on the roof) and an 80w portable to charge my batteries.

I have 2 different types (and ages) of batteries, so my system is set up so only 1 battery is being used or charged at a time. There were only a couple of times over 4 mos. when I needed to use my generator to charge.

I didn't have any charging from the van's alternator.

Anyway, I'm wondering if it's a good idea to get rid of the 105ah FLA battery and use only the 100ah AGM.

Less capacity but 180 watts on the roof and I'll be upgrading the controller from a PWM to MPPT. And I will finally install
a solenoid or smart isolator so I'll get charging from the alternator.

I'm wanting to ditch the generator and LP tank (and the FLA) to save weight.

Is anyone doing OK with just a single battery and about 200 watts of solar?

PS: Power use will mainly be a 45w 50L Alpicool fridge but also 2 LED lites, AA battery chargers, 2 PC fans and occasional laptop use.

 

[chris84]

That would be pretty marginal. A fridge in an RV or van that runs on a compressor consumers about 30-50 amp hours per day (my experience in a variety of above freezing places)

Solar varies a lot between summer and winter, but I use an average of 25 amp hours per day on sunny days per 100W panel.

200watts of solar would be 50 amp hours on sunny days (less in winter, more in summer, almost nothing on cloudy, rainy days, but that would be the case no matter how large the system is, my 16,000W system on my house produced just 7620 watt hours today which would be 635 amp hours at 12 volts, or less than 4 AH per 100W of capacity, that is the nature of solar on a cloudy winter day) That just doesn't leave much margin, but it doesn't have to. If you are ok with needing to run the engine on some days a marginal system is just fine!

You don't have to plan for the worst case scenario. Some people do (4-5 days of battery capacity with twice the normal usage in solar) but it doesn't have to be the plan.

in the same way that I chose my fridge to cover my average use (not the worst case that I am away from civilization for 10 days). I can use an ice chest with ice to supplement my fridge for those times when I need more cold food rather than choosing a huge refrigerator that can hold 10 days foot. I chose one that can store 3-4 days food and can supplement when needed.

Based on what you said a 100AH battery bank and 200W of solar will work for you. If I was designing the system for a customer I would probably spec a 200 AH battery bank and 300W of solar to build in a little more margin. But if you accept the limitations of your system and commit to just finding another way to charge when needed, it should work.

So that is a long answer to saw 100AH of battery and 200W of solar is marginal but ok. I would try it and then add more if you don't like the results.

 

[user 423]

That just doesn't leave much margin, but it doesn't have to. If you are ok with needing to run the engine on some days a marginal system is just fine! 

A 100AH battery bank and 200W of solar will work for you. If I was designing the system for a customer I would probably spec a 200 AH battery bank and 300W of solar to build in a little more margin. But if you accept the limitations of your system and commit to just finding another way to charge when needed, it should work.

So that is a long answer to saw 100AH of battery and 200W of solar is marginal but ok. I would try it and then add more if you don't like the results.

Thanks for your reply. I'm a seasonal traveller and usually do a lot of driving from May-Oct, so while I will generally have good sun, the temps are higher,too. Adding alt. charging should help quite a bit.

Besides wanting to reduce weight, I'm re-thinking my floor plan to make better use of the limited space. I guess I should leave space for another AGM just in case I need it later.

 

[maki2]

I have a 150 watt panel and a 160ah deep cycle marine AGM. The trick is to use the computer during the peak solar hours so thsat you have a nearly full battery in the evening so that you have fridge and lights. In the evening mt i ternet time is done with my phone or 8" tablet which I do have plugged in to a 12v usb outlet.

I can also turn on my small, electrically effiecint diesel heater for a few hours at bedtime and early morning.

So I do have a little more solar snd battery than you but not a substantially larger amount.

Of courseI cant keep it all going on a string of days with poor solar input. I cant do a lot of hours laptop computer time on cloudy days. My goal is to have my battery still at 65% by morning but you get used to telling yourrself it is time to cut back on power use and remembering to get all your USB devices charging by 9 in the morning in winter.

 

[Camper]

Sure wish I could find a low power laptop.... my Dell will use 25-watts plugged in and not charging the battery but that adds up in 18-hours a day use. I do have LED lights and no fridge though.

 

[Uncle Todo]

I just got a Lenovo Legion a couple months back, it's more a gaming laptop but not higher end.
It came with a 170w adapter but hardly pulls any watts during low activity like web stuff.
I'm going to try a 90w 12v adapter and see how it does.
If it works well enough, great, then if I need to I can break out the 110 and use the inverter.

I sold off my gaming desktop to buy a laptop for vanning it, in retrospect maybe I should have gone with something a tad milder...

 

[Psyckosama]

Do not downgrade a laptop power supply. It'll still try and draw that 170w at full load and burn the thing out and possibly damage your system.

As for the 170w, it does not draw 170w constant, only when at full load.

 

[Uncle Todo]

That's just it though, when I had a power meter monitoring usage with the 170w adapter it was only pulling a fraction of that.
I forget how many now exactly and I didn't make a note of it, but it was less than 90w which the 12 volt charger was rated at.
Granted that's measuring from the AC side so no idea how that would correlate to the DC side.

 

[highdesertranger]

watts are watts, same for 120v and 12v. in other word if it draws 150 watts at 120v it will draw 150 watts at 12v. however the amps will be significantly more.

highdesertranger

 

[chris84]

I just got a Lenovo Legion a couple months back, it's more a gaming laptop but not higher end.
It came with a 170w adapter but hardly pulls any watts during low activity like web stuff.
I'm going to try a 90w 12v adapter and see how it does.
If it works well enough, great, then if I need to I can break out the 110 and use the inverter.

I sold off my gaming desktop to buy a laptop for vanning it, in retrospect maybe I should have gone with something a tad milder...

Don't use a smaller power supply. It will not reduce the power used. It might burn up during those few times when more power is needed.

 

[Freelander]

My MacMini and 43" TV only use aound 50 watts running on the invertor.

 

[Uncle Todo]

Thanks HDR

Chris, that's what I'm getting at, light use, and the laptop right now is only pulling 26-28 watts with two Chrome windows open with several tabs in each and Outlook.
It's not pulling anywhere near the what the brick is rated for, even charging a 50% battery while gaming pulls less than 100 watts.

On 12v I would not be trying to do GPU or CPU intensive activities but instead would use inverter.
I don't even really watch video on it, usually on my tablet.

And if I kill it, it's only $30 bucks and maybe it'll die soon enough to just return to Amazon.
Actually I've been looking around for a plugin DC 12v power supply to test it, and as well a couple other things I'll be running as well.

 

[Psyckosama]

It's also likely to be more poorly made and has a non-zero chance of damaging your equipment.

DO. NOT. DO. IT.

 

[Uncle Todo]

The poorly made bit I concur, the chance of damaging my equipment may be non-zero, but I don't see being all that high.
But high enough to see some point in it, plus typically I'm a hard proponent of using OE chargers due to having seen so many aftermarket ones fail or get really hot during use.
Warnings heeded.
I'll keep an eye out for something cheap, i3 or Pentium powered. Had even crossed my mind to use a NUC and a 12v monitor.
I'd like to add a 24"ish TV/monitor on an arm anyway, and I believe the Pentium powered NUCs can run off 12v.
Thanks guys!

 

[Freelander]

Can you even buy Pentiums anymore?

Nevermind I see you can.

 

[Uncle Todo]

Oh how the mighty have fallen!
A desktop I built about 3 years ago I built with a Pentium Gold processor, really not too bad at all.

Another computer for having something on-board, or in vehicle would be a LattePanda.
Not the cheapest solution, but very small and still needs a screen.
https://www.dfrobot.com/product-1727.html

And something like this for a TV/monitor
https://www.amazon.com/Supersonic-SC-2211-22-Inch-Widescreen-Compatible/dp/B0066AE4M8

 

[user 423]

Off topic since post #5....

 

[user 423]

I have a 150 watt panel and a 160ah deep cycle marine AGM. The trick is to use the computer during the peak solar hours so thsat you have a nearly full battery in the evening so that you have fridge and lights. In the evening my
 internet time is done with my phone or 8" tablet which I do have plugged in to a 12v usb outlet.

I looked up the specs on a generic 160 ah AGM and found that it's 105 lbs.  That would save some weight over 2 batteries and would be a good compromise. My laptop really isn't used that much and I use a tablet most of the time.
 
Do you need to run your generator very often with your setup?

I'm wanting to go from a 20 liter Alpicool fridge to a 50 liter but strangely enough they are both rated at 45 watts.

 

[jonyjoe303]

how much room do you have on the roof?

My situation this last summer was trying to run my 26L fridge (set to 26 degrees) and also my swampcooler and roof vent from a 220ah lifepo4 and using a 240 watt solar panel to charge everything. It was barely keeping up. The fridge even though it was using anywhere from 18 to 24 ah per day will slow deplete any battery if it doesnt get a good charge everyday.
Once winter started up and I was getting less sun, my 220ah lifepo4 was limping along at 30 percent most of the time, the 240 watt panel was just topping off what I use the previous day. It was maxing out at 9 to 10 amps of charging power. I was also using a laptop/lights/fans charging cellphone. I almost bought a generator to try and charge my battery.

Instead I bought a 365 watt solar panel, that fix my problem. In december I was getting up to 15 amps of charge power, in january I have seen up to 17 amps of charging power. My lifepo4 has been at 100 percent since the first week I installed the 365 watt panel. I also added another battery bank of 312ah of li-ion batteries and that one is also at 70 percent (I keep it between 50 and 90 percent). In the past 2 months even with overcast days and rain, my batterybank has been charge back up to 100 percent every single day.

If you can fit a 365 watt panel on your roof, do it, you won't need a generator or the alternator even in winter. I have a small astrovan and I easily got it to fit on my roof. I'm very impress with the power I'm getting out of that panel. I paid 250 for the panel, less then what a generator would have cost me. I have no place to store a generator that I would have rarely used. I was struggling with 240 watts of solar to run my fridge and other devices, I wouldn't recommend 200 watts or less. It could be done but you might have to stop running certain devices while charging the battery.

As for as fridges, depending on how will they are insulated and how low the temp you want is what will determine the power usage. A 43 liter fridge I had used about 26ah per 24 hours when set to 40 degrees, the 26 liter I have now uses about 18ah per 24 hours when set to 26 degrees. When set to 12 degrees it was using about 30ah per 24 hours. At 12 degrees I could keep frozen foods except ice cream.



after I painted it

 

[user 423]

The roof is big enough but it is a fiberglass mid-high version and I don't want to have to drill into it. If I mount the 80W up there I will still have the DC plug-in that is installed at the rear of the van. If later I find that I need more solar, I can buy another panel to use as a portable. With another 100W panel, that would be 280W total. But then I really don't want to mess with a portable again. Actually, I'm thinking about mounting the 80W on the side of the van where it can be adjusted for angle. I'm just in a redo planning phase at this time.

Since I mainly use the rig only from May to Oct I will 'usually' have pretty good sun. Although where I was at in 2019 there were several long periods when it rained a lot. At that time I did use my gen. some but also was able to plug into shore power several times over the summer.

The fridge I will be getting is 2.5 times larger than what I have now and even though the max rating of 45W is the same, I'm sure it will use more power on average.

I'll be interested to see how much difference the MPPT will make. Along with the juice from the alt. I'm hoping to be OK.