idea for DIY low current and low temperature protection

[Lernfaehig]

Hello everyone. I've experienced that a lot of solar power stations have issues with solar panels when the sun is coming up or going down. 3 of the ppwer stations I've tested make clicking sounds every few seconds as the MMPT charge controller realizes voltage is coming in but then the amps are too low to charge the battery and it turns off again.
I've tried finding a commercial product that would read the current while the panel(s) are connected to a dump load and only connect the panel(s) to the charge controller once there is sufficient amperage vailable to start charging. As I didn't succeed to find something like this I've created a block diagram but unfortunately lack the electronics skills to verify my idea and create a custom pcb for it. Additionally it should be very easy to use this same setup to implement low-temperature charging protection for systems not originally supporting it.
I'm hoping somebody here with better electronics knowledge than me can verify my idea. If you think think this could make a viable product you're very welcome to "steal" my idea make it into a commercial product ;-)

 

[SeaGal]

I've experienced that a lot of solar power stations have issues with solar panels when the sun is coming up or going down. 3 of the ppwer stations I've tested make clicking sounds every few seconds as the MMPT charge controller realizes voltage is coming in but then the amps are too low to charge the battery and it turns off again.

You say "have issues", but I suspect you may be trying to fix something that is not a problem. That's just how some inverters work and happy to work like that for years and years.

 

[Lernfaehig]

Hello SeaGal, the issue is that some power stations have a mechanical relay for this function. When this relay switches it is a) very noisy and b) do these relays have a limited lifetime.
When solar panels are permanently connected you wouldn't want to have it close to you like e.g. in a van or caravan. The noise from the relays is definitely loud enough to wake you up.

 

[v_green57]

FWIW: none of the stand-alone alone CC's I have ever owned since 2004 have done this.

When you are saying "power station" are you referring to an AIO unit?

 

[Lernfaehig]

FWIW: none of the stand-alone alone CC's I have ever owned since 2004 have done this.

When you are saying "power station" are you referring to an AIO unit?

yes, I'm referring to All-in-one systems like the Fossibot F2400 or the Anker Powerhouse 757. Not all powerstations have this mechanical relay, for example the Bluetti AC200 doesn't but some do and they are very annoying.

 

[v_green57]

yes, I'm referring to All-in-one systems like the Fossibot F2400 or the Anker Powerhouse 757. Not all powerstations have this mechanical relay, for example the Bluetti AC200 doesn't but some do and they are very annoying.

Okay, then.

Find one that doesn't, buy it, and sell the clicking one.

 

[Andrewr05]

Okay, then.

Find one that doesn't, buy it, and sell the clicking one.

You can live your life that way if you want.

But matter of factly telling people to do that is silly.
Sure, you can just go buy something better, you can always just buy yourself out of any problem.

But some people like tinkering for the sake of tinkering (and out of necessity) and will go their whole life modifying every single thing that they own to suit them, before they will ever sell something off because of a small problem, discrepancy or inconvenience.
⠀

 

[Lernfaehig]

Okay, then.

Find one that doesn't, buy it, and sell the clicking one.

I do have 6 different ones (3 of which have the noisy relay). They are not in daily use and I don't use them in a van or camper. Nevertheless this is something not found in any manuals and in very little reviews of solar power stations. Jason from the Jasonoid Youtube chanel has included it into his reviews a test topic after I pointed it out to him. Apart from that I don't know any reviewers that have checked for this issue. In my and Jason's testing about 1/3 of units has this clicking noise so many people may buy something they regret afterwards.
This is my main motivation to find a solution for this issue. Unfortunately I lack the electronics skills to make this into a product myself.

 

[kommando]

The relays do have a finite life with specs calling for a minimum number of cycles before wearing out the relay contact points. However the most wear takes place when current is being passed, cycles with no current being passed cause little wear to the points. SMA made a set of inverters common to PV and Wind set by the firmware loaded, hardware is common to both including DC relays. The PV DC relays rarely fail but the Wind ones do fail as the Wind ones cycle a lot more in 24 hrs than a PV and do it when there are passing amps.

If you want to reduce the cycles then if you can increase the voltage needed for the DC to be turned on.

 

[Lernfaehig]

The relays do have a finite life with specs calling for a minimum number of cycles before wearing out the relay contact points. However the most wear takes place when current is being passed, cycles with no current being passed cause little wear to the points. SMA made a set of inverters common to PV and Wind set by the firmware loaded, hardware is common to both including DC relays. The PV DC relays rarely fail but the Wind ones do fail as the Wind ones cycle a lot more in 24 hrs than a PV and do it when there are passing amps.

If you want to reduce the cycles then if you can increase the voltage needed for the DC to be turned on.

Thanks for your reply. Unfortunately these All-in-One systems don't offer any settings regarding solar input, at least none of the brands/prodcuts I know of. Also the voltage is not a good decision factor as it will depend on which solar panel(s) you connect. This will be different for nearly every user.

 

[v_green57]

You can live your life that way if you want.

But matter of factly telling people to do that is silly.
Sure, you can just go buy something better, you can always just buy yourself out of any problem.

But some people like tinkering for the sake of tinkering (and out of necessity) and will go their whole life modifying every single thing that they own to suit them, before they will ever sell something off because of a small problem, discrepancy or inconvenience.
⠀

The OP said this:

"As I didn't succeed to find something like this I've created a block diagram but unfortunately lack the electronics skills to verify my idea and create a custom pcb for it. Additionally it should be very easy to use this same setup to implement low-temperature charging protection for systems not originally supporting it."

And then this regarding the noise of the relays:

"they are very annoying."

And then this:

"Unfortunately I lack the electronics skills to make this into a product myself."

Given that, different hardware is one very direct way to deal with the "annoyance" in this instance.

If the OP had the skills necessary, which to his credit he admits that he doesn't, of course modifying/improving existing hardware would be indicated. You always learn stuff that way and the satisfaction of wrangling someone else's engineering into something better is hugely gratifying.

If somebody else wants to figure it out, that is, of course, up to them. But that's a pretty big ask.

 

[v_green57]

Driving to a service call just now, I remembered this, mentioned in another post:

LoadMaster XP - A Smart PV MPPT Solar Hot Water Controller

A solid-state, low-cost, reliable solution for solar hot water from PV. Zero maintenance & CO2, connected, smart combi pre-heat control.

projecthub.arduino.cc

This guy seems to really, really understand MPPT. He might be very interested in this issue.

 

[Lernfaehig]

The OP said this:

"As I didn't succeed to find something like this I've created a block diagram but unfortunately lack the electronics skills to verify my idea and create a custom pcb for it. Additionally it should be very easy to use this same setup to implement low-temperature charging protection for systems not originally supporting it."

And then this regarding the noise of the relays:

"they are very annoying."

And then this:

"Unfortunately I lack the electronics skills to make this into a product myself."

Given that, different hardware is one very direct way to deal with the "annoyance" in this instance.

If the OP had the skills necessary, which to his credit he admits that he doesn't, of course modifying/improving existing hardware would be indicated. You always learn stuff that way and the satisfaction of wrangling someone else's engineering into something better is hugely gratifying.

If somebody else wants to figure it out, that is, of course, up to them. But that's a pretty big ask.

I totally agree to this being a big (t)ask. On the other hand it may be an easy thing for somebody experienced with such designs and therefore could also be seen as an opportunity to make money by selling this as a finished product.

 

[Steve T - IoW UK]

Sorry for a slow response...(Loadmaster is my 'baby')
As Seagal says the initial powering up of solar devices in a stable and controlled manner is surprisingly not so simple and many solar devices flicker on and off at dawn (i.e on cloudy mornings i could sometimes hear the relays in my old Solis inverter cycling on off ).
Some wanted my loadmaster project to all be powered from the PV (that proved quite a pain -it's primarily powered from a small 12v adapter). Many small AC-DC switching regulators will happily operate with say 80 to 300V DC from the PV but I still found I needed some some small hardware comparator circuit measuring PV volts (with a lot of hysteresis) to cleanly switch the power supplies output on/off to the micro processor. Even that benefited from generating some increased loading whilst the PV output was too low which then gets released as the comparator turns to supply to the main circuitry and microprocessor. Anyway...it was all a lot of faffing!

Thoughts..
1) yes, measuring virtually unloaded PV volts is a hopeless way to understand if there is sufficient power available to connect some load. ...that's the root of this problem...the PVs open circuit VOC voltage looks high...a relay connects a load and then that voltage instantly dies.

2) Could you add some resistive loading which then gets disconnected at the same time the controllers relay turns on? . Some added capacitance may also help at the point of switching.
3) MOSFETs .some FETs have REALLY low milli ohm ON resistances (look at small SMD FETs in a BMS switching 150+A!) Relays are old news ...in many but not all cases

3) it was small little problems like this that got me into Arduino..and eventually that lead to Loadmaster. (any professional coder looking at my self taught Loadmaster coding would no doubt laugh or cry?). Arduino has a huge online resource of simple examples......it's as simple as...' Set up one pin as an analog Input and another as an output, read the analog voltage on the input, IF it's under or over X volts, then set the Output pin High. Wire the output pin to a pre made relay PCB (or solid state relay? ).
Ok coding and electronics is not for everyone but after a few brain scratching days you will be please that you can create solutions to little problems like you mention

Go for it!