@Asmyldof Looking into a different segment is not being a bastard. And the two example panels probably come with different quality, nothing wrong with that.

@jippie :-P You can make your own for about €0.7/Wp

just need some glue and something to stick the cells onto

bonus: you can decide the current & voltage

Physical things aren't my best

Ah, the great thing about solar is, worst thing that can happen is it doesn't work

no fire or such

I beg to differ

It wouldn't be your first solar panel that catches fire

I have not had any fires that weren't intended... see my discussion with @PlasmaHH

:-P

too much scrolling back :-p

The silicon won't burn. It may glow

Did you see the solar power cycle path?

not the dutch one

but the

japanese or taiwanese or so?

the one where you cycle under the panels

the one with the panels in a roof over the path along a main road?

yeah

I want that in my garden to sit in the shade :-p

some day when I'm rich

Don't have to be rich anymore

Full installation should be possibly at € 2/Wp

I first have to weed through my garden to get to the spot where I want to sit down.

lol

Just have to buy the right stuff at the right place

I need a contractor to remove the forest from my back yard

Or a flame thrower

@crasic sounds interesting. Two or three years ago I would have loved to see the progress or help. These days I use Eagle for stuff from others or for others and all the libraries they then have, etc, would probably add more overhead through your system.

hmmm, now there is an idea

How will you make Eagle load them, by the way?

I'll look for the black smoke and eventually burning house to see where you used to live

@Asmyldof I wish I owned my roof :-/

@jippie you could have them mounted on a rack that folds over it from both sides

:-P

@Asmyldof I bet the neighbours wont mind

Of course not

Anyway, have to go. Have to return the bike in veldhoven after refueling :(

Had I not invested in new Rigols I might have asked them if I could keep it for €18k

enjoy

(And then made the Belastingdienst pay for half of it Jan 2016)

:-|

good morning

They wanted 21k for it.

Too much

Can get it with <10km for that

@Asmyldof you're probably right about the "shopping comment"

@Christoph it gets outdated so quickly

A chemistry and its behaviours is a valid topic, it'll be around for years

But beyond that

What you want, probably, is a simple $ 0.5 (bulk) chip that controls 2 internal or external MOSTs

my original thought was that knowing why a part works would benefit others, but you're right

Or a board, if you aren't designing in quantity that costs $1 or less for the chip, the board, the MOSTs and the capacitors and resistors

yes, I think the BQ29700 is more what you had in mind

That's exactly the line I'm thinking along

I hoped to be able to create a PCB for the solar buck, the battery protection, and maybe a small MSP430

If you can CC/CV the buck regulator for highest charging efficiency, that chip is all you need, set at the right voltages of course

It is up to you

But I'd be lying if I said I hadn't just used a PCB in the middle of my own PCB before

:-)

Chinese Guy makes 100000 PCBs, sells me 10, I solder those in my design: done

No seeking MOSTs

is it safe to say that the smarter the buck regulator, the harder it will be to control it with a uC?

I hooked up a PWM output to an opamp to a buck regulator's FB input in LTspice, and that seemed to work, but real life will surely be different

@Christoph Not absolutely

It can very well be that you can force a regulator into low and high power peak behaviour, but how to best do that is always down to specific topologies

And some are harder than others, but it's not always just down to internal complexity

Your idea of FB manipulation is one that is not unheard of in the first "Digital Bench Top Powersupplies"

Or, "Switching Digital ..."

Saw one design with a pre-stage that was controlled by the chip with a capacitor barrier, PWM and op-amp smoothing, allowing the chip to regulate the incoming voltage to about 4V above linear output and then regulate the output linearly

pre-stage was a simple TDA type Flyback chip

Not the neatest solution, but it worked okay, if you accept some extra 15 ~ 50kHz noise levels

I think I have to accept that if I want to mess around in the regulator's feedback path

If you want a robust solution you need to know about poles and zeroes and control theory and know what happens in bode plots when you do X or Y, so you can prove that your system will always work. If you're just designing something as a one-off or several-off, you can use a lot of common sense and a little insight about feedback loops to give yourself a better-than-90%-guarantee

is 90% pre- or post-simulation?

Post sim, pre-week(s)-of-testing

sounds good

simulations cannot give 100% ever, without re-doing some maths yourself

simulations are very good these days, but there's a reason many critical devices get tested in Autoclaves and damp-heat chambers, etc

I think in most DIY cases 90% is the best you're getting post-sim for any design

But, anyway, it should be possible, for a first try to use some Op-Amp sense applied to feedback and current sense loops on an out-of-the-box controller

If you have one with a current limit and a voltage limit, set by external resistors there's a much better than 50/50 shot you can control both domains with some evil trickery

Depending on the values of those resistors the trickery may take more or less tuning of components, but that will all be revealed once you know your requirements

As long as you have the patience to wait here you can always link some stuff here for me to look at, but if you have selected a device, thought of an idea and want to know if it would work and possibly how, you can always ask another question to get some more perspectives on that

(question as in on the ee.se site itself)

more specific questions is what I'm heading for, because now that I have an idea about the overall topology of the thing I can break it down into smaller domains and think about them (and I hope I don't forget about your argument about overall vs. local efficiency from yesterday)

BTW, for the fun of it, I looked at the BQ29700 series datasheet again, the BQ29706 seems to be geared for LiFePO4 fixed current fast charge

It is a very important one. Never start optimising at the beginning, progress further and then forget to look back

It's okay to optimise locally, but always look around the schematic if what you are doing actually makes sense for it all

the bq29706 because of the 3.85 overvoltage level? IIRC the recommended maximum voltage for LiFePos is around 3.65 volt, so that looks ok

Many pre-produced boards actually specify 3.9V

LiFePO4 is a little more forgiving, as long as you don't keep it at that level for prolongued times

So, in fact, your system efficiency can benefit from you making the buck regulator 3.9V/3.5V settable. You could use PWM, but those two would be enough to keep the battery full but in shape

Or maybe 4V

Another thing, best safety is of course to have your BQ297##-type protector to be as close to the actual cell as possible in all regards

I'm currently building a simulation for PWM-controlled switchable CC/CV.

I'd advise you in the final product to keep the system's long-term float voltage below 3.6V because of the flat plateau, keeping the cell at 3.5V or 3.55V won't cost you much of the capacity, but gives you some margin for error in your settings

Especially with thermal differences some set points may turn out to be very different in the real real-world.

If only for thermal gradients of the resistors used

CC controlling a buck regulator with unknown-if-suitable OpAmps and the knowledge of a mechanical engineer is a pita. I'll go for something simpler like you suggested!

switching the buck regulator between 3.5/3.9V is a lot easier with a selectable voltage divider, which I can do with a simple transistor

:-)

Always go for solutions no more than 2 steps ahead of your knowledge, unless you have no other option

Next time you'll probably be more at ease using 3V to 4V ranging

3.5V will not be charging, it will let your cell dictate untill it is discharged to 95% and keep it there until the cell gets really used

If you set it at 4V highest, your controller will see the "release" of the protection with a bigger margin

it will flop up to 4V at 3.85V

so to speak

Assuming you charge up to the flopping point, your battery will be "fuller" than the 3.5V

But it's "risky" to try and keep it at full, since both the battery's full and your circuit's settings will be somewhat temperature dependant

So it's better to relax to 3.5V

It'll also keep the cell healthier for longer, most likely

But, probably at 10mA drain the "fuller" part may only be minutes

95% is just a number that tumbled out of my behind

thank you, I'll ask again when I have a schematic (when I'm sufficiently confident that I got it right I'll ask another question on the main site)

Feel free :-) Good luck

I am plorb

is that edible?

bite

No

@Asmyldof, gotta design something with MOSTFETs now.

@ThePhoton It's Metal Oxide Silicon Transistor, it's completely valid

That we conveniently leave out the field effect is nobody's business but our own

@Asmyldof That stupid automotive networking thing was the stupidest project I ever worked on in my life.

....

I looked at the page for 5 seconds before deciding I was not going to invest serious life-seconds to further read text

Is that bad?

@Asmyldof Not unless you want to sell fiber optic transceivers to German auto companies.

I don't, because they won't buy from me anyway

@Asmyldof Your fab is probably not big enough.

@ThePhoton My fab can be as large as need be if I have potential customers

No issues there

Also I'm pretty sure the environmental testing documentation has to weigh more than 1 year's production of parts to get a part qualified for the automotive market.

I have good contacts and my credit rating is platinum-plus-AAAA-triple-A-gold-plus

Testing can also be arranged.

With people who probably already know that document

@Asmyldof Unless your real name is actually Philips, I'm pretty sure you'd actually have trouble getting enough credit to build a fab.

As I said, I have contacts

I don't need to build a fab

And if my name was Philips I'd have jumped of the roof of the Strijp S tower

@Asmyldof Then you'll have a lot harder time making money at it.

You don't need to make money on the first 10000

Making it harder to get funding.

You need to make name

@Asmyldof Nobody in the automotive business wants to buy just 10,000 of something.

Before they'll even talk to you they want you to show how many million per year you're prepared to supply.

Good reason to not talk to them then

I'll stick to motorcycle-tive industry then

frown most. annoying. project. ever.

Now that I have ordered nearly all components, the customer decides they'd rather not use batteries and stuff

Guess I'm going to be building a LiFePO4-equipped motorcycle sooner than I thought.

e-motorcycle*

@Asmyldof Iiiiii ... don't want a pickle....

?

...just wanna ride on my motor sickle

?

No sound at the moment

Have been Dave-less for days

twitch

Anyway-ay-ay-ay, I'm going home, might clickit there

zZzZzZz though

@Asmyldof libs are just xml files, and snippets are stored permanently in every schematic. this is true starting version 6 or so. When you "refresh" the library it just reloads those nodes from the latest store on disk

instead of pointing to a file, that file is an api hook into the module database

morning

@Asmyldof saw your last weeks mail just now ;o)

how do you call this package? talonix.com/images/rf/MRF837.jpg