Small solar generator build questions

[Mike Jordan]

I am going to build a small power station/solar generator that uses Ryobi 18v batts. Why? Because I already have lots of them. I am mostly copying one that I found on this forum. He used a Victron MPPT controller, because the Ryobi chargers are all limited to 2-3amps. The Victron output is adjustable in the app.

I don't want to spend the $110 on a charge controller dedicated for this little power station. Are there any of the cheap controllers than I can limit output to 2-3 amps?

 

[snoobler]

No such thing as a cheap MPPT SCC, and that's what you need for an ideal solution.

Alternate:

Amazon.com: DC Buck Converter, DROK DC to DC Step Down Power Supply Module 10V-65V to 0-60V 0-12A Adjustable Voltage Regulator Transformer Board with LED Display for Volt Reducer: Home Audio & Theater

Amazon.com: DC Buck Converter, DROK DC to DC Step Down Power Supply Module 10V-65V to 0-60V 0-12A Adjustable Voltage Regulator Transformer Board with LED Display for Volt Reducer: Home Audio & Theater

www.amazon.com

2X 12V panels in series at the input (meets the 10-65V input limit)
output set to 21V (output 0-60V)
output set to 2-3A

The downside here is there's no means for cut-off. With the charge controller, once 21V is hit, it terminates charge and floats the battery. Your current will just drop to zero. Leaving the battery like this for an extended period would damage it. Since his float was 20.5? You could try setting it to that. Your charge will take a little longer, and you might only get to 90%, but there are prices to pay for compromise.

Since the little display can show current, that would be a good "full" indicator for you.

DROK Step Down Voltage Regulator
Product Parameters:
·Input Voltage Range: 10V-65V
·Adjustable Output Voltage Range: 0-60V
·Adjustable Output Current Range: 0-12A
·Output Power: 0-720W
·Output Voltage Setting Resolution: 10mV
·Output Current Setting Resolution: 10mA
·Typical Efficiency: 94% (input 54V, output 30V, current 5A)
·Voltage Display Error: ±1%+20mV
·Current Display Error: ±1%+20mA
·Response Time: ＜50ms
Product Features:
·The DROK DC-DC numerical control buck voltage converter is a programmable buck module with all-digital LED display which can display real-time voltage and current.
·Compared to the similar product, you will find that this buck module has a compact size and it works efficiently and stable.
·We applied advanced microprocessor control for this buck module. Voltage and current can be adjusted accurately by pressing the button, you can adjust it to output constant voltage and current.
·Package Includes: DROK DC-DC Buck Converter Module ×1

 

[Mike Jordan]

It would never sit on a solar charge for ever. It would just be one of those things where i am waiting for a watched pot to boil. I was also looking at buck converters. I found some no name china stuff. I have always liked my Drok meters. But that buck is going to take up a fair amount of space.

So unless someone has another idea, it might be no solar or bite the bullet

 

[pollenface]

How many of these 18v batteries do you have? I'd do a 36v system, just for fun

I found plugging buck converters directly into mppt charge controllers would kill the buck converters. The mppt must have loaded them for all they were worth. But maybe I just needed bigger heatsinks.

 

[chrisski]

IME, I designed one part of my system around a good deal, and I wish I had just spent the money on better panels. I saved a whopping $100 but cost me a weeks worth of extra work.

What is the goal of this solar generator? I’m trying to see what you want to power off a whole bunch of power tools batteries.

18 volts is an odd number and 36 volts is odd also. Not insurmountable, but parts are commonly available for 12 volt, 24 volt, and to some extent 48 volt systems. For example, my two Victron Charge Controlers are designed for 12 volt and 24 volt battery bank charging. I can adjust the float. Absorption, and equalization voltage, but the owners manual does not say the range, so I’m not sure it could be set in between for 18 volts.

To do odd software things, I’ve checked into different thing about programmable PC chips and also a Raspberry Pi, but that stuff is more than I’m willing to do for the projects I have in mind.

 

[Mike Jordan]

My goal is to be able to charge a laptop or phones on the go. Power a thing or do during a short term power outage. And solar charge away from the grid. But mostly I just like to tinker and make things out of non-traditional stuff.

I can overcome any strange voltage combination easily, on the discharge side. But I know less about the solar end than most anyone here. The guy I was going to copy (don't have his name handy) used solar panels in series with the Victron, and made it work. Sounds logical to me in my brain. That brain has extensive experience in 120v A/C, 12v DC, and combining the two. But solar... not so much

 

[williamsk913]

The charge controller you pick will depend on size of array, how you wire it, your budget, whether your bms has low temp charging cutoff (if using LiFePO4) and maybe even the ability to play nice with whatever inverter you pick. It sounds like you are planning a smaller system. Any idea of your battery bank and inverter size?

 

[Mike Jordan]

The charge controller you pick will depend on size of array, how you wire it, your budget, whether your bms has low temp charging cutoff (if using LiFePO4) and maybe even the ability to play nice with whatever inverter you pick. It sounds like you are planning a smaller system. Any idea of your battery bank and inverter size?

The battery bank I stated above is Ryobi 18v batts. But I'm about to give up on that idea. A reasonable SCC controller for the odd voltage is evasive

 

[Hedges]

The battery bank I stated above is Ryobi 18v batts. But I'm about to give up on that idea. A reasonable SCC controller for the odd voltage is evasive

"Elusive"

Signed,
The Grammar/Spelling/Homonym Police

 

[Supervstech]

The best way to use the ryobi batteries is to disassemble them, arrange the cells into a size of voltage readily controlled by a quality bms, and charging them with a scc designed for that voltage.

 

[Supervstech]

"Elusive"

Signed,
The Grammar/Spelling/Homonym Police

Heh... I was picturing the device running and hiding from search...

 

[Mike Jordan]

The best way to use the ryobi batteries is to disassemble them, arrange the cells into a size of voltage readily controlled by a quality bms, and charging them with a scc designed for that voltage.

problem becomes.... they don't work well in the tools after that

 

[Mike Jordan]

"Elusive"

Signed,
The Grammar/Spelling/Homonym Police

no faux pas committed

The SCC for the voltage rage is hiding from me as I am SURE its out there somewhere