Cheap Solar Charge Controller

[Carv]

Thanks to Mike90250, Wrybread, and little Harbor my original trailer solar powered fridge system has 3 years of flawless operation!

https://www.solarpaneltalk.com/forum/off-grid-solar/12v-solar-for-rv-or-camping-etc/349707-advice-on-rv-set-up-wiring

So I'm looking at semi duplicating this system to run a mini fridge in the bed of my truck for an overland rig set up:

Knowns:
1) Fridge runs about 210W at start up and settles down to about 100W after a minute or so of operation.
2) I'm going to run 2 Costco Interstate -6V GC batteries in the bed so I'll have about 230Ah of battery storage.
3) I'm going to make a direct run off the trucks alternator with a relay (auto or switched) to charge the GC batteries when the truck is running so they should be full a lot because I'll be driving a good amount of the time.
4) looking at getting about a 200W flexiable solar panel off Amazon to charge the batteries when camped.

Questions:
1) looking for recommendations for a cheap 20A solar charge controler with USB plugs on it from either eBay or Amazon (not sure if I need MPPT or PMVwill work)?

2) looking for recommendations on a Switched or Automatic relay for the battery charging system off the alternator.

3) looking for recommendations on cheap sub $200 flexiable solar panel.

4) I want to put the flexiable panel on a 20ft to 25ft teather with a plug at the batteries and just plug the panel in when camped to charge the batteries and unplug and store the panel when driving. What's the formula/chart wire diameter required for this run using something like this panel?

https://www.amazon.com/Monocrystalli...exible+solar+p anel+200w&qid=1597701040&sr=8-67


If you have any other recommendations I'm all ears.

Thanks

[Mike90250]

Rethink the flexible panel. They often have a short lifetime because of their construction and the solar element is not as robust as rigid panels. And then, you have to worry ( I would worry) about the attachment method, and if it will last . Many glues are rated for hot roof exposure, but will they last under a dark, hot PV panel ?

[sdold]

That panel looks like it is nowhere near 200W. The specs are very confusing, I can't even find the dimensions.

[SunEagle]

That panel looks like it is nowhere near 200W. The specs are very confusing, I can't even find the dimensions.

I agree with sdold. While the title of that add states 200W it later states only 30W. And based on the number of cells (10) along with the specs 5.5V and 3amps I would say the entire add is giving false info. IMO I would not consider this panel or any flexible panel based on their short life span.

It also looks like this panel may only provide 5.5V based on the USB cable that connects to it.

Again do so research but stay away from this item because it will not charge a 12V battery system.

[secessus]

> looking for recommendations for a cheap 20A solar charge controler with USB plugs on it from either eBay or Amazon

The cheap controllers like that are on/off controllers, not MPPT or even PWM in the normal sense. They are all roughly the same inside, have a single charging setpoint, etc. They do work, I'm not knocking them.

I would not spend money on MPPT for this arrangement, as the long wiring run will eat up the excess voltage MPPT requires. There's not a lot of excess voltage available on 12v panels to start with.


> recommendations on a Switched or Automatic relay for the battery charging system off the alternator.

A plain constant duty solenoid switched from the ignition circuit is cheapest and will have fewer gotchas in combination with solar charging. A voltage-sensing type costs more and can backfeed power to the starter bat after the ignition is turned off, but can open up the possibilty of self-jumpstarting.

I'd normally mention something like the CTEK D250-series 20A (or Renogy 30/50A equivalents) for someone not comfortable with choosing their own components. That type of device will both charge from alternator and solar (built-in mppt controller for 12v panels), but the remote panel wiring run negates that. If you change your mind and mount framed panels on the roof then something like a CTEK becomes a simple way to do both types of charging.

Like the others I advise against flex panels in general that that flex panel in particular.

[Carv]

Sorry Mike hard panels are not an option. Nothing will be mounted to the roof, they'll be stored in the camper shell which is also my bed when not in use, and hooked up when I'm camped/stopped.

Do you have any recommendations for 200W flexiable panels?



Secessus, that CTEK is $450, waaaaay more than I'm looking to spend. I can find recommendations on the triggered relay, thank you for the info on that. Something like this:

https://www.amazon.com/FOSHIO-Charge-Switch-Terminals-Connection/dp/B071YNCX5R

Let's talk Umbical length.
Based on short circuit current of less than 9A and sun Kings post #120 in my original thread I should be able to make a 25ft run with 12AWG and be more than safe...no?
https://www.solarpaneltalk.com/forum...ge8#post355344

On the Charge Controller, with this set up what would be the differences between the MPPT or the PMV Does anybody have any actual experience with any particular one they can recomend/ post up a link?

Thanks

[littleharbor]

[QUOTE=Carv;

On the Charge Controller, with this set up what would be the differences between the MPPT or the PMV Does anybody have any actual experience with any particular one they can recomend/ post up a link?

Thanks[/QUOTE]




Hey Carv, been a while. I'm living in Baja these days. Out of the solar biz. Living a very comfortable life for very little $$

If you're planning on running a 12 volt panel then an MPPT controller would be of no benefit. A basic PWM controller is all you need. the cheap imports with USB outputs are ok but If it were me I'd keep a 2nd back up on hand

[Carv]

Anybody have any recommendations on any of the equipment I'm looking for (within my budget of cheap?

[SunEagle]

Anybody have any recommendations on any of the equipment I'm looking for (within my budget of cheap?

When it comes to solar "cheap" usually means either fake or very low quality.

You can try out something on eBay but expect it to either not perform or die quickly.

[Carv]

Ok since you guys are the smartest people I know when dealing with 12V electric.

On the run from the 136A rated alternator to the AUX batteries in the bed, some I'll have 2 sets of batteries pulling (if it makes a difference), how big of a fuse and how many amps should I wire for considering it's a 25ft run?

[SunEagle]

Ok since you guys are the smartest people I know when dealing with 12V electric.

On the run from the 136A rated alternator to the AUX batteries in the bed, some I'll have 2 sets of batteries pulling (if it makes a difference), how big of a fuse and how many amps should I wire for considering it's a 25ft run?

I have similar sized coach batteries in my RV connected to an alternator through a device that will send power first to the starter battery and then the coach batteries. I am unsure of the fuse size but the cables look like they are at least a #1 or #1/0 battery type cable which will carry at least 150 amps.

Based on the location of the coach batteries I would say about 25 feet to the alternator.

[Carv]

Thank you Sun Eagle.

Is there a formula that will dictate or limit how many amps the rear/house/coach batteries will pull?

Wire size will not dictate how much draw the batteries will pull, it will only heat up if undersized for the draw load, if under sized, correct?

[Carv]

If I did a 200W flexiable panel, what about running a Morningstar Prostar PS-15?

200W /12 = 16.67A, would that Prostar 15A handle it?

[SunEagle]

Thank you Sun Eagle.

Is there a formula that will dictate or limit how many amps the rear/house/coach batteries will pull?

Wire size will not dictate how much draw the batteries will pull, it will only heat up if undersized for the draw load, if under sized, correct?

Surprisingly there really isn't a formula concerning the amps coming from an alternator to the coach batteries.

Wire size does not dictate how many amps the batteries will pull which is why you go as big as what can be delivered and then fuse appropriately. If you go too small the wires can heat up and in worst case burn up. unless there is a fuse that will open at or below the wire amp rating.

[SunEagle]

If I did a 200W flexiable panel, what about running a Morningstar Prostar PS-15?

200W /12 = 16.67A, would that Prostar 15A handle it?

Technically yes. The output from a panel is less then the stated value which is based on the wattage divided by the Vmp not the battery voltage so I expect the panel will output less then 16.67a. The 100% output value is usually the Imp rating.

A quality CC can handle a little more than then it's amp rating but usually they state how many watts you can connect to the input.