Portable solar panel and lifepo4 battery: would I need a solar charge controller too?

[das784]

Hello, I've been lurking around youtube and this forum for a couple of years studying solar, and am finally thinking about my first solar purchase, very much a "starter" system. I live in an apartment with a small balcony, so space is a huge limitation.

I'm looking at a "Topsolar 100W Foldable Portable Solar Panel", which seems to have some sort of charge controller built into it. At least it has several outputs: 19V DC, 14.4V DC, and USB A and C ports. Would that indicate a built-in controller of some sort, or a voltage regulator of some sort, or what?

I'd like to get a small 12V 20AH lifepo4 battery to go with it, just a really cheap $60 battery. Since the panel has those multiple outputs, could I just connect directly from the 14.4V output to the battery to charge it, without a separate controller?

Eventually I want a larger battery and an MPPT controller. But that's not in the budget yet. Don't want to waste money on a cheap PWM unit if I don't have to. TIA!

 

[MisterSandals]

which seems to have some sort of charge controller built into it

You need a solar charge controller but never one feeding another. What charger is in your panel? Any pics or links?

 

[das784]

This is the link to the panel: https://www.amazon.com/gp/product/B07ZZ8VY2V
There doesn't seem to be much technical description/explanation given, but the below image seems to be the best for showing the outputs...

In the Q/A section the manufacturer (I think) gives this answer to a question:

Q: Can I plug this into a charge controller?
A: YES! This solar panel comes with a 14.5V charging box, it is designed for charging 12V battery. If you want to charge the battery through the DC 19V port, you can connect the solar panel to the controller first, and then connect the controller to the battery, it can charge the battery safely.
By TP-Solar Team in the United States on March 25, 2020

By "charging box" maybe they mean controller? My interpretation is that the 19V port is the raw panel output, and the USB and 14V ports are the output of some sort of built-in controller...but that's a guess from a complete solar newbie.

 

[MisterSandals]

By "charging box" maybe they mean controller? My interpretation is that the 19V port is the raw panel output, and the USB and 14V ports are the output of some sort of built-in controller...but that's a guess from a complete solar newbie.

Mostly marketing speak but it looks like its just DC output and not a charger. For USB, the charger is always built into the device (phone, tablet,...) that accepts 5V.

Back to your original questions:

I'd like to get a small 12V 20AH lifepo4 battery to go with it, just a really cheap $60 battery.

What do you intend to power with this battery? Its just 250Wh.

Don't want to waste money on a cheap PWM unit if I don't have to

I have a few of these and they work surprisingly well. You wouldn't need MPPT unless your array was a lot higher than battery voltage or what a PWM would accept.

https://www.amazon.com/Controller-Intelligent-Regulator-Paremeter-Adjustable/dp/B08NFSCZ4V/

 

[MisterSandals]

and am finally thinking about my first solar purchase, very much a "starter" system.

If i were building a first fun system, i'd get a real panel for cheap, like this: (quite a few near Kentucky!)

SOLAR Panels $50 each! - electronics - by owner - sale - craigslist

Got a couple hundred+ just deinstalled working, Schuco 220 watt solar panels available in east Tennessee for $50 each (3 panels MINIMUM) or buy a full pallet of 25 panels for $1120, = $45 each in...

lexington.craigslist.org

 

[das784]

Thanks, this has been very helpful. I'll plan on getting the PWM controller for now.

What do you intend to power with this battery? Its just 250Wh.

That battery would just be for powering laptop, phone and a couple of other USB things, in case of power outage. I've measured my usage and 250WH should be enough for 3 to 5 days usage. And I already have a 12V USB-C adapter that can power both phone and laptop.

Eventually I'm planning to get a 100WH battery, and probably a 1.5 or 2 KW inverter, but that's not in the budget for several more months probably.

If i were building a first fun system, i'd get a real panel for cheap, like this: (quite a few near Kentucky!)

I've been thinking seriously about that, but leaning toward portable/folding because of very limited space in apartment and on balcony, and also because I'd like to be able to take the panel with me in my car when travelling. If experiments go well and I think I could fit a second panel on the balcony (while staying stealthy), I'd definitely look at a real panel like you're describing.

 

[efficientPV]

with a 14.4V output, it already has an internal buck converter. Just connect it to the battery. The BMS in the battery will take care of the charging. I'm getting a similar panel in a couple days for a 12AH battery.