Solar controller question

Another line of thought... Generators, while handy, are high $ items with high target value for thieves, druggies, tweakers, and Pawn Shops. They develop legs. A set of solar panels... well, that's a hard sell in the new market, let alone the used market, the demand is not really there.

Think about where you'd rather put your money, and what it's worth and what the market is for solar, if stolen, versus a generator. A generator makes power 24/7, solar, only in day light, and it needs a battery pack for storage of energy. Not as practical, and nowhere near as liquid as a generator, as a power source. Someone might comment on what a nice big generator you have. Unlikely you'll ever get comments about how big your solar system is, unless it is obtuse or obese in size.

The probability of someone wanting your size solar panels used is slim to none, the probability of wanting your Honda, which only comes in 1000, 2000, or 3000 sizes in the quiet versions, is very high.

That said, I like having options, so I have both.

Just to put some numbers on it, our MW (wants 1550w input on shore power or PSW) only wants about 1100w on MSW so it draws 110amps when it is on.

We might use it ten minutes a day if that.

Ok so how many AH is ten minutes of 110 amps? 18AH. To me 18AH in a day is so trivial. If it is a big deal in your set-up then you can solve that in the obvious ways.

Almot's figures seem too pessimistic to me but it all depends on weather and your latitude and time of year and then whether the panels are flat, tilted, or tracking what AH you get a day.

I am fine with about 260w tilted (140AH a day) from mid-April to end September here on the Island at 49.3N for a 458AH battery bank. Rest of the year the (it is portable) solar stays in the garage at home when we go camping since it is not worth taking the solar and don't need it anyway for weekend type camping.

I agree you have to find out how much solar you need by trial and error. You can take a guess and go with that first. Any amount of solar will always be too much or too little depending on time of year. If you have enough for winter that will be too much for the summer. You can't fine tune it.

mena661 wrote:
... if I wanted to tent camp, I would've never started RVing in the first place. Makes no sense to spend 10s of 1000's on a RV just to turn everything in it off.

Like I said, they don't want to hear.
Getting an RV is exactly what many people do when they grow older and are getting tired of tent camping. And not necessarily "10s". Many trailers, and mine is no exception, are under 19K new - but this is again something useless to talk about, when the main argument is "the bigger and the louder - the better". In the same line of thinking is saying that cooking on gas stove, running a fridge less than 20 cu.ft, or watching a TV that is less than 48 inches and is on less than 8 hours a day, is a "tent camping".

mena661 wrote:
There are ways to reduce power consumption though. LEDs, low draw devices, not using SOME things, etc.

Really? :) But this would be a "tent camping", no?

Leaving aside air conditioner, of all the standard RV equipment the only "thing" that should better not be used if the goal is to minimize the generator time - what the poster asked about - is microwave. It requires bigger battery bank and significantly increases daily Ah draw and thus dependency on generator. If you bring more 120V "things" from home out into the wild because you can't feel comfortable without them - it's tough then.

With MW the minimum solar size that would allow not to run a generator on most days, goes from 160-200w to 300-350. Which 350W I do have (and more), so MW is something that I can run with my particular system. Doesn't mean that I have to run it, or run it often, because same tasks can be done on propane if you know how to do it. But you need to know how.

Edit - PS: one more thing.
When batteries need 40 Ah in the morning to make them full, this doesn't mean that I only use (and solar only collects) 40 Ah in 24 hours. It's probably more like 60-70 Ah, but I don't know and don't care how much more. Like BFL said - here I agree with him - solar is "all or nothing" deal. In a daytime when my batteries are nearing 100%, panels generate more current than batteries can take. So any loads that I run after 10.30-11.00 am, are "free" - batteries are sitting peacefully on Float - while I run vents, pumps, charging vacuum, laptop, power tools - yes, I have tools in my 26ft "tent" :) - etc.

So don't get upset, you'll figure it out when you start using solar.

smkettner wrote:

Horizon170 wrote:
Just curious as I don't have any solar-----will this 100 watt kit keep two gp 27 batteries topped off?

While not in use, YES.
Assumes most things turned off.

Will it significantly help when camped off grid, YES
But don't go crazy.

Running group 24's or Group 27's that are not true deep cycle batteries will drive you crazy. Running real deep cycle batteries won't.

Horizon170 wrote:
Just curious as I don't have any solar-----will this 100 watt kit keep two gp 27 batteries topped off?

While not in use, YES.
Assumes most things turned off.

Will it significantly help when camped off grid, YES
But don't go crazy.

BFL isn't the only one that objects. :) Sure, you can camp light but where do you draw the line and who's to say what is too much or too little. IMO, if I wanted to tent camp, I would've never started RVing in the first place. Makes no sense to spend 10s of 1000's on a RV just to turn everything in it off. LOL! Make your own decision on that one. There are ways to reduce power consumption though. LEDs, low draw devices, not using SOME things, etc.

Horizon170 wrote:
I now see that I need around 400 rather than 100. I am just trying to find a cheaper solution to running my Honda eu2000i. We usually have 120 volt shore power except when we go to QZ.

As usual, I will say (and as usual, BFL will vehemently object) that there is ALWAYS another way to skin this cat, other than increasing the solar size. Namely - reducing your power needs.

I am using so little energy in winter in Baja (a desert climate similar to QZ), that my solar only needs to put 30-50 Ah into batteries. And, since it's mostly sunny there - same as in QZ - a 200W solar would do. Since I have 490w, my batts are 97% full by 11 am on a good day, and 100% few hours later. On a very bad day they are 95-97% full by sunset. Trailer is warm, fridge is running, lights are up, laptop is charged. BUT... you can spend 130 Ah a day same well. Or 300 Ah a day.

People having got used to unlimited power supply don't realize and normally don't even want to hear, that spending over 50 Ah a day when no airconditioning is needed, is a choice, and not a necessity. Generator... what generator? :)

Horizon170 wrote:
Just curious as I don't have any solar-----will this 100 watt kit keep two gp 27 batteries topped off?

Usual comment to this (very common) question - what do you mean by "topped off"? :)

To prevent them from self-discharging in storage-like conditions, i.e. with everything or almost everything disconnected - yes. Even a 10w panel will do.

To bring them back to 100% full condition from, say, 50% discharged condition - no. 100w panel will harvest 30 Ah a day at best. 50% discharged pair of gr 27 need 115 Ah to be full again.

To bring them back from 85%-90% full condition, i.e. when only about 30 Ah need to be replaced - yes.

If you are running some loads while trying to charge your batteries from solar, those above numbers should be corrected of course.

Horizon170 wrote:
NinerBikes and BLF13, Thanks guys. I now see that I need around 400 rather than 100. I am just trying to find a cheaper solution to running my Honda eu2000i. We usually have 120 volt shore power except when we go to QZ.

Do you want really simple? Have a spare ladder you can lash these two panels together to to chase the sun, and a couple of hinges to pair them together and a scrap piece of carpet or astroturf to throw under them?

Solar Blvd 200 watt 2 panel kit.

Basic simple PWM charge controller.

basic 15 amp plug and play charge controller.


Little more advanced and programmable, with adjustable voltage. It is second generation version, ie v1.2, which is programmable for voltage in bulk mode. 14.4 +- .9v plus programmable for various battery chemistries, lead acid, gel, AGM, Li Ion Fe, etc.

programmable 20A charge controller.

Add some wires and some ring terminals or battery clamps, and you are OK for a while. Need more? buy a 3rd panel, bump you up to 300 watts and 16.5 amps instead of ll.

Short run from the PWM controller to the batteries, mount them close together, 5 feet or less, 10 or 8 gauge wire, and 12 gauge from the panels to the controller should give you efficient low losses charging.


Put it together, and you can save yourself some fair dinkum.

So you aren't ready to build your own system, and want plug and play? How about 160 watts of portable solar panel. But this, and just add carpet underneath the panels before setting it down.

9 amps at 7 hours in the winter will put a dent in your battery charging. 63 amp hours.

Plug and play foldable solar panel kit.


Don't forget to first change out all your lights for LED's that draw a lot less current.

NinerBikes and BLF13, Thanks guys. I now see that I need around 400 rather than 100. I am just trying to find a cheaper solution to running my Honda eu2000i. We usually have 120 volt shore power except when we go to QZ.