PWM85 Solar Charge Controller

Name: PWM85 Solar Charge Controller
SKU: 23218
Price: 20.00 USD
Availability: OutOfStock
Rating: 4.81 (4 reviews)

(4 Reviews)

A simple PWM solar charge controller using the Atmel ATTiny85

Designed by AdamWelch in United Kingdom

$20.00

Out of Stock

Sold out since Oct 21, 2021

A simple PWM solar charge controller using the Atmel ATTiny85

What is it? This is a simple PWM solar charge controller using the Atmel ATTiny85 at it's core. This solar charge controller is suitable for twelve volt lead acid batteries but you can adjust the cod…

What is it?

This is a simple PWM solar charge controller using the Atmel ATTiny85 at it's core. This solar charge controller is suitable for twelve volt lead acid batteries but you can adjust the code and flash it to be suitable with other chemistries. It will arrive fully assembled, calibrated and tested.

It is suitable for 36 cell solar panels (with open circuit voltage of 21-22 volts) up to 100 watts and will regulate your battery to 13.5 volts.

The code is open source, available on Github and you can flash it with a suitable ISP programmer or an arduino. You can easily adjust the regulation voltage and the onboard status LED if you want to adapt the code.

Why did you make it?

I wanted to adapt Julian Iletts PWM5 design for use with Atmel microcontrollers. The biggest challenge was to make this version as efficient as Julian's original - and I think it's just about there!

What makes it special?

This solar charge controller is super low current - less than 1mA when the LED is not active (and it isn't as long as your battery is under the target voltage). That's it, it doesn't sing, dance or save your solar stats to the cloud.

What other amazing things do I need to know?

Hold on to your hats - each PWM85 is delivered in a recycled antistatic bag (which component bag will you get?) and comes with a free 3d printed bracket in a random colour.

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Review Breakdown

Average Ratings

Product: (5.00)

Documentation: (4.75)

Shipping: (4.50)

Communication: (5.00)

Phil | March 11, 2022

An excellent item

I have this unit keeping a battery charged on an electric fence, it has been in service for a year now and the battery is still in good condition the unit has been through some extreme temperatures 50deg C "West Australian desert" and did not faulter, it's so good I'm ordering more. :)

Paul | Sept. 13, 2021

Does its job with aplomb.

Bought two of these a while ago as a key part of a solar powered wood-drying kiln project (never buy one of any hardware, am I right?).

It forms part of a circuit where another uController decides when to cut off the load when the 12v car battery is getting too low to survive the next fan cycle.

Essentially, if light levels are OK, and temperature is above a threshold, turn on 3 fans for x seconds. Stop y seconds, reassess readings. When temp is above 2nd or 3rd thresholds turn on fans for x+x seconds - and so on till its dark. No fans turn on if battery is dangerously low (set to 12.5v atm).

The surrounding air got to 75 C at one point two weeks ago, no bother.

This has been in situ and working for about two months, impeccable. My particular use-case actually needs to keep polling the battery to asses what to do next, so that'd be a nice addition, plus as I say the essential task of deciding if battery is too low. Cutting the load when battery is too low is not something I would want, the uController still needs to sip juice all night and check for light levels to re-emerge, see.

This unit manages the replenishment of a 12v battery from a solar panel and was easy to integrate into my final hack-ish solution. Plenty of burps and farts on the way, but never from this unit.

Ivar | May 21, 2021

Works very well

Tested it with a 20w solar panel and a 7Ah lead acid battery. Float charge was 13.46V as advertised.
Really liked the mounting bracket .Thanks

Response from AdamWelch | May 24, 2021

Thanks for taking the time to post a review. I'm glad it is working for you as expected.
Cheers

Tobias | May 4, 2021

Immediate customer support after delay in shipping process

Although not caused by supplier, I've got immediate and appropriate response after delay in shipping process. Product is well documented and working as described.