PWM85 - Microampere PWM Solar Charge Controller

[@JulianIlett]

Congratulations, excellent result :)

[@AdamWelchUK]

Thank you very much Julian

[@sarkybugger5009]

@Julian Ilett Have you finished Muppet 2 yet? Asking for a friend...

[@pfeerick]

@@sarkybugger5009 Don't forget added incentive to work on it again... the sun is now out again (or so the last video reported)! :-P

[@NuttyforNissan]

Mine has been in and operating flawlessly now for over a month, Thanks Adam & Julian. Phil

[@AdamWelchUK]

That’s great to hear. Thank you for letting me know!

[@Lastaii]

Great job! Really like the fully opensource-ness of the project. That said, I have just bought one :)

[@AdamWelchUK]

Thank you

[@marcrives279]

My PWM85 is still working under my roof, with a 20W solar panel. By the way, this is a nice 3D printed card holder !

[@AdamWelchUK]

Great news. Thank you so much for you help and suggestion of the 3d printed holder! :)

[@johnnodge4327]

I'm glad the PWM85 is selling well Adam. I should have some of my kits built up for sale ready made, but for some reason, decided it was too complicated. Good to see it's working for you though. Keep it up.

[@AdamWelchUK]

Cheers John. Taken me a bit by surprise to be honest - need to restock!

[@SimpleElectronics]

Fantastic project! I love it!

[@jethrotull5847]

God bless you ! But I just made a comment on a 6 year old cheep PWM video you posted. Laziness took control and had no idea a “update” video was available . Sorry.. and…Thanks I’ll check it out !

[@ivorbiggen9599]

Very informative as ever. Thank you Adam

[@patrickmagee774]

Great project.

[@AdamWelchUK]

Glad you like it!

[@tl1024]

Thanks for the great build, just got 2 coming.

[@AdamWelchUK]

Great - thank you.

[@JackButlerVideos]

Looks so nice! Maybe the next challenge should be a 3d printed waterproof case ;)

[@AdamWelchUK]

Cheers Jack. I’ll give that some thought!

[@slybunda]

excellent i have 2 of these i bought from you to use in the car and you set them to 13.2v float for car battery which is awesome. are people able to get custom regulation voltage preset before shipping?

[@nickush7512]

Excellent work Dude.

[@cheetahkid]

OK, I managed to get it reprogrammed, to work with Li-ion via BMS. I set it on 12.6V. I thought running to reprogram at 3.3V (as ISP) with the 3.3V board, not to be, it is ok to reprogrammed using 5v as long it isn't plugged in with solar panel or the 12v battery. I will be testing right now for a few days (I try not to get it overcharged or it will degraded and again might lower the voltage to 80%), weather getting too warm. I also received the solar panel, it is 18V and 50Watts.

[@AdamWelchUK]

Good to hear you’re changing it for your needs. Yes, programming with 5v is fine, and it’s always best to program it when totally disconnected from other sources. Cheers

[@SmithyScotland]

Sold out already. Any plans to sell more?

[@AdamWelchUK]

Yeah that was faster than I thought! A second batch should be on the way soon.

[@objection_your_honor]

Why didn't you use a P-Mosfet and eliminate the silly high-side charge pump? Granted the P-mosfets had higher RDSon when Julian lifted the design from somewhere, but today's P-mosfets can have very low RDSon.

[@fredflintstone1]

nice video well done Adam :-)

[@lesliepieterse1072]

Good stuff, hope to be running one of these soon :)

[@piconano]

If I remember right, lead acid charge cut-off voltage is 13.85V not 13.5V. That shouldn't affect the cycle life sulfation, but I don't know.

[@AdamWelchUK]

Depends on the chemistry, but 13.5 should be safe for all, it is a gentle charge and it’s what the PWM5 was set to. It’s adjustable for anyone who wants to as well.

[@andymouse]

Nice work !...cheers.

[@AdamWelchUK]

Thanks!

[@chrispollard6568]

Just got mine in the US. Really nice 3Dprint - what printer was used?

[@AdamWelchUK]

Thanks for letting me know. I’ve an Ender 3 Pro.

[@dougle03]

Aren't PWM controllers now pretty much inefficient junk? I'm only fitting MPPT controllers, also why not bring the lead battery up to 14.4v for more capacity? 14.7v would be a bit aggressive, but 13.5v is very conservative...?

[@johnnodge4327]

Absolutely not inefficient at all, for small solar power systems. An MPPT might get a few extra Wh of energy from the panel, but then the more complex and power hungry circuit, simply burns up that extra power when the sun goes down. By contrast, a small and super efficient PWM charge controller, like the PWM85 or Julian's PWM5 consume almost nothing from the battery when the sun is down, so don't waist any energy. PWM is also cheaper than a decent MPPT, so the savings can be put towards another panel, which will increase solar power far above the small gains on an MPPT charge controller. An MPPT only really makes a difference, once you're past 3 or 400W of panels, otherwise it's simply better to spend your money elsewhere. ;) The PWM85 is programmable, so the termination voltage can be whatever you prefer. I prefer 13.8V myself, but 13.5 is still an acceptable voltage, as it's above the nominal standing voltage of a Pb battery.

[@pfeerick]

MPPT and PWM both have their use cases. MPPT is predominately for when you want high voltage strings, or can't physically put more panels in, thus are trying to increase the efficiency of obtaining that solar energy. This comes at an expense - they are more expensive, and complex than their PWM cousins. PWM solar charge controllers in comparison are cheap, and are much simpler, resulting in less things to go wrong. I did come across some research suggesting that PWM charging could also help prevent battery sulfation... but I don't know to what extent that was. And as a side not... did you know the Epever MPPT solar charge controllers go into PWM mode in the mornings, and in the evening? Once the panels are producing less than 15W, it goes into PWM mode as it is no longer efficient to run the MPPT charging system. Weird stuff!

[@Minipimmer]

a lot of emphasis is on the standby consumption of the circuit but every time you switch the mosfet you connect the battery in parallel with the parasitic capacitance of the panel. How do you prevent the current spike from breaking the mosfet? is there any filtering to make slow down the slope of the current of the panel?

[@Luke-san]

Wonder how it would behave using a supercapacitor as a battery. Some of the issues I've seen with cheap (semi) MPPT boards is that they are not super efficient with small panels and this seems ideal.

[@AdamWelchUK]

Seems like a good idea Luc.

[@clintoncoker6]

I have an idea. I'd like to power a car stereo from a 4s (or could use 5s) LiPo pack, but this exceeds the stereo's max supply voltage when fully charged. Do you think a PWM charge controller would work to PWM the lipo pack into the stereo (through a capacitor or small lead acid) to regulate the supply voltage to 13.5V?

[@slybunda]

are you able to program this to be a full on smart charger that will charge up to 14.4v then auto drop to float voltage?

[@AdamWelchUK]

It’s an ATTiny so you can program it to do pretty much anything. The PWM5 which I ported did exactly what you are after. The hardware is capable, only the code needs writing.

[@slybunda]

@@AdamWelchUK been using your 2 controllers for a while now for charge controlling solar panels in cars. excellent design the low self power consumption is ideal

[@thelwq]

Hi Adam, can it be used to act as a DCDC buck converter with Pb battery changer? I'm wondering if this could be used to charge my 12V Pb battery used by UPS from my 48V Li-ion batteries. Max voltage of 60V would require some changes in circuit am I correct? Thx.

[@AdamWelchUK]

I’m afraid not. Solar panels are fairly unique in their nature - there is no stored energy so when they connect to a battery their voltage drops to almost the same level (they pull down to just above the battery voltage - and that allows current to flow from the panel to the battery). A battery connected on the solar input would not pull down in the same way, and would pull the battery under charge up to high. As you’ve identified, you need a DC2DC buck converter to achieve what you want. Cheers

[@thelwq]

@@AdamWelchUK Thx for your answer. Yeah, I'm a bit off, as I'm used to MPPT solutions which would work OK, as the tracker would pull max power and convert it to voltage required to safely charge Pb battery. Something like this would be needed... libre.solar/devices/mppt-1210-hus/

[@slybunda]

how much wattage should the resistors be?

[@CarlRecktenwaldJr]

Is the new arduino sketch compatible with the previous 5 volt versions? To help reduce power.

[@AdamWelchUK]

Yes it works with both versions. You just need to adjust the regulatorV variable to 5.0 or to be more accurate set it to the exact voltage of your 5v regulator output.

[@alexxustube]

Hi Adam! Is there any chance you can modify the pwm85 to charge 24V batteries from a 24V solar panel?

[@Brian_Of_Melbourne]

How is the '3.3 Volt' version different? I see it has extra stages in the charge pump but the schematic still shows a 5 Volt rail rather than a 3.3 Volt one. Am I missing something?

[@barrygreengrass3379]

Adam - how are you getting on with the Super Cheap Spot Welder you bought?

[@cirdiam1800]

What does the circuit do? Does it ensure it’s pumping the most current it can into the battery until it is charged (and then keep it topped up)?

[@AdamWelchUK]

Exactly that, yes.

[@cirdiam1800]

@@AdamWelchUK Thanks. It would be interesting to see a comparison demo - ie how much current goes into the battery (when it needs charging) with and without the PWM85, under the same conditions. People talk about PWM vs MPPT - but really all I care about is that the current going into the battery (when it needs charging) is maximized - regardless of that being at the maximum power point or some other operating point of the solar panel characteristic curve.

[@pepethefrog7193]

I​t does intermittenly disconnect the panel from the battery so battery doesent overcharge. But it doesent transform excess volts into amps like mppt does.

[@jimthvac100]

Adam, Would a capacitor added to the input give higher amperage pulses during charging (When it is using pulse width charging). Or would the potential higher amperage input damage the controller?

[@slybunda]

this should work well, something like a 470uf cap on the input should be interesting. will need to test it.

[@widjis]

is it so difficult to modify it as MPPT charger?

[@spikeydapikey1483]

Noice.

[@PatricksDIY]

Those Sold out quick less than 3 hours lol.

[@AdamWelchUK]

Crazy. May be able to list a few more soon.

[@iantsears]

Ordered two.

[@AdamWelchUK]

Got your order. Thank you Ian. First customer points for you!

[@hairfritz2667]

The way you kept repeating the name of the product made this video sound like an advert, which is what it turned out to be. Some of your other videos have been much better adverts, without trying to be, I think.

[@mattivirta]

PWM destroy batterty solar user ,lot better have and longlive to battery have MPPT charger. lot batter,safe,lonlive,battery good.

[@AdamWelchUK]

I don’t agree, the two technologies use solar power in different ways, it doesn’t necessarily charge the battery any differently.

[@johnnodge4327]

How a battery is charged is irrelevant. PWM and MPPT both charge the battery in the same way. In reality, an PWM cycles the battery less, which will make it last longer, not less.

[@pepethefrog7193]

@@johnnodge4327 PWM pulses the battery with the full solar voltage. I would not recommend doing that to a lipo. Voltage measurement will be dependent on the mosfet state and jittery without smoothing. Except for power consumption pwm85 does a worse job than a 3A adjustable buck converter costng 70ct.