Cheap solar battery charging

[jansman]

Latest addition....

I guess a question for Yorkshire Andy...
... You know how I buy everything you link to...?

Well, I bought one of these, no regrets, but with my newly bought multimeter, I sort of tested it.....

It looks like it throws 5V straight at the 1.5V batteries and maybe limits the current to about 110mA each(constant current?). The LED lights never go green or out. So I suspect they are brute force chargers. After a few hours the batteries were all warm. Does that tell me that the batteries might be getting over- charged?

I opened the battery charger up, as you do... And there doesn't seem to be any electronics in there at all. apart from the lamps.

Should we ever trust these to leave batteries on trickle charge. I'm leaning towards 'probably not'

I understand that rechargeables can take some abuse, but were these false economy?

I’ve got those. Leave ‘em on for a couple of hours and Boom! You have charged batteries. Don’t over think it. If it’s solar charging, give it five or six hours.

[jennyjj01]

I’ve got those. Leave ‘em on for a couple of hours and Boom! You have charged batteries. Don’t over think it. If it’s solar charging, give it five or six hours.

LOL. Yes. I do over think it. I can't let it go. It's like food waste!

There are so many inefficiencies in the solar charging process*, that it annoys and frustrates me. I'm trying to poop miracles out of the lowest budget gear, so even though the sunlight is free, I don't want to waste a drop.

My solar rig is to be as efficient as Tesla, but as cheap as Lada or I will have failed )

* 2/3 of the time the sun is not shining
most of the time, the panel is at a totally wrong angle to the sun. Wasting 30%?
1/4? of the time my controller sees fit to completely disconnect the panel.
And now my battery chargers expend energy making the batteries into hand warmers?

And the final insult: Those eneloop batteries will be bu66ered after 500 charge cycles?

I'll accept compromises, but I have the urge to know where they are.....

Back to these super cheap chargers..... There looks to be nothing much inside them, but there must be. Andy's volt ammeter gadget suggests there is something very discreetly hidden in there. Maybe molded into the plug or just too small to see when I opened it up?

[jansman]

I’ve got those. Leave ‘em on for a couple of hours and Boom! You have charged batteries. Don’t over think it. If it’s solar charging, give it five or six hours.

LOL. Yes. I do over think it. I can't let it go. It's like food waste!

There are so many inefficiencies in the solar charging process*, that it annoys and frustrates me. I'm trying to poop miracles out of the lowest budget gear, so even though the sunlight is free, I don't want to waste a drop.

My solar rig is to be as efficient as Tesla, but as cheap as Lada or I will have failed )

* 2/3 of the time the sun is not shining
most of the time, the panel is at a totally wrong angle to the sun. Wasting 30%?
1/4? of the time my controller sees fit to completely disconnect the panel.
And now my battery chargers expend energy making the batteries into hand warmers?

And the final insult: Those eneloop batteries will be bu66ered after 500 charge cycles?

I'll accept compromises, but I have the urge to know where they are.....

Back to these super cheap chargers..... There looks to be nothing much inside them, but there must be. Andy's volt ammeter gadget suggests there is something very discreetly hidden in there. Maybe molded into the plug or just too small to see when I opened it up?

Batteries, battery banks and the likes, last about 500 charge cycles. That’s how it is. They don’t last forever. A bit like humans. The bible states seven score years and ten. Nothing is forever.

[jennyjj01]

Batteries, battery banks and the likes, last about 500 charge cycles. That’s how it is. They don’t last forever. A bit like humans. The bible states seven score years and ten. Nothing is forever.

True.....
Thanks for reminding me I'm mortal....( though I'd settle for 150 years)
But with that attitude we would accept Electric cars with the range and speed of milk floats (remember those?)

I'm happy to compromise and use cheap stuff, but I'm trying to get a handle on which corners to cut and which to not cut.

[Yorkshire Andy]

[quote="Yorkshire Andy" post_id=213062

It looks like it throws 5V straight at the 1.5V batteries and maybe limits the current to about 110mA each(constant current?).

Did you measure the voltage with the battery in circuit?

You will see 2 sets of resistors on the board one set for the LEDs to protect them another for control of power to the batteries

The bonus with the basic simple usb charger running from a usb panel is no loss into control circuitry

[jennyjj01]

The bonus with the basic simple usb charger running from a usb panel is no loss into control circuitry

Andy,
No control circuitry, but these bu66ers burn off 70% of all energy input as heat from the charging resistors!

It looks like it throws 5V straight at the 1.5V batteries and maybe limits the current to about 110mA each(constant current?).

Did you measure the voltage with the battery in circuit?

You will see 2 sets of resistors on the board one set for the LEDs to protect them another for control of power to the batteries

I just had another look. They are literally just pushing USB 5 volts through a tiny resistor into each cell. And those resistors get burn your finger hot!

So, by my reckoning these chargers waste 3.5/5 = 70% of the energy going into the charger as heat. That's beside any heat from the cells themselves as they charge or over charge.

I know it's free solar energy, and each charge is trivial, but still. If the solar station is only used to charge AA cells via USB, that's 70% of all captured energy wasted! They could have saved half that wasted energy just by charging the cells in pairs, in series.

The LEDs seem pretty pointless, too

Wouldn't these be more or less a constant current charger? I=(5-1.5)/R

I suppose it has no reason to be more clever than that. Not going to quick charge at 100mA, but not going to cook the battery when it's full, either?
Being that simple, they do waste 70% of the energy available. I could get cross about that

The heat from those resistors could be an issue too?

[jansman]

And that energy wastage happens on our little domestic set ups,right up to great big wind farms; which is why the Net Zero goal is absolute fantasyland.

[jennyjj01]

And that energy wastage happens on our little domestic set ups,right up to great big wind farms; which is why the Net Zero goal is absolute fantasyland.

Very much so. The objective of the various 'green initiatives' is all about grants and backhanders and flavour of the month.
We can only achieve net zero with massive investment in nuclear, with all the pitfalls that entails.

I'm all for green, sustainable energy, but no matter how green it is, we should look to reduce waste first and last. Energy not wasted is energy we did not need to generate.

If amateurs like us can see where money and energy is wasted in our systems, then we can spot when we are being lied to by salesmen and politicians.

UK becomes first major economy to pass net zero emissions law.
New target will require the UK to bring all greenhouse gas emissions to net zero by 2050.

They'll probably just redefine 'Greenhouse gas' or redefine 'net zero'

[jansman]

Well the world is scrambling for fossils right now ‘cos of Ivan. If renewables were that good, then we would be bringing them in at a hell- for- leather speed!

[jennyjj01]

Latest addition....
...The usb output ones have been a bit hit and miss especially on their promises of power

Well, I bought one of these, no regrets, but with my newly bought multimeter, I sort of tested it.....
...
I opened the battery charger up, as you do... And there doesn't seem to be any electronics in there at all. apart from the lamps.

Super Geek mode. I've been picking the brains of my electrics expert and reading from the man on the internet. The former thinks I'm daft in the head! But that's by the by.

I really got a bee in my bonnet about eeking every ounce of energy from my tiny solar charging station to charge batteries, specifically AA's. I have it in my head to eliminate waste at the battery and charge controller and USB - AA chargers and to simplify it completely to keep my masses of AA cells charged quickly and efficiently. The Car battery and controller to be set aside for the next bigger solar project. I had been thinking of getting a (£20) multi USB adaptor and up to eight of those small, cheap( 8x£4) USB chargers. But now another idea is forming.

I wonder if Yorkshire Andy or any electronics wiz can sanity check my latest ideas..... About £100 cheaper and a damned site simpler. A mini-project.

My little 25W solar panel can generate about 18V at about 500mA in good sun. Estimating that if I pushed that STRAIGHT into AA cells in series, (12x 1.5V ?) with no other components at all, it would charge them in about eight hours of good sun. Call it one or two days.

That's best case scenario. Or to put it another way. Charge 6 - 12 AA cells per day. Pretty pathetic! That's without any waste.
(Does that sound right?)

Plan A: Solar panel -> PWM Charge controller -> Car Battery -> 2 x USB - AA chargers plugged into the crappy charge controller,
Plan B: Solar panel -> PWM Charge controller -> Car Battery ->12v - multi USB adaptor - > Multiple USB AA chargers

Flaw with Plan A. Massive energy waste at charge controller: Cost of car battery: Rubbish charging current. energy waste at AA chargers.
Flaw with Plan B. Massive energy waste at charge controller: Cost of car battery: Cost of adaptors and USB multi-way: Massive energy waste at AA chargers.

I'm now onto plan C

Rationale: The solar panel might struggle to recharge the car battery quickly enough, if I were trying to charge lots of AA batteries.

I know. I KNOW. It's free energy, but if we can eliminate some waste, there won't need to be as many panels or I can charge more AA cells faster.

Now. There's a thing on ebay called a DC-DC 'Buck' converter, on sale for about £3. These multi purpose things are built into all sorts of chargers. As I understand it, it steps down voltage and steps up current with very little waste. It gives a steady output voltage that can be limited and the current that can be limited too.
E.g from the solar panel, giving ~18V at ~500mA, it could give me 9V at (almost) up to 1A.

Here's Plan C:

Solar panel -> Buck converter -> Six AA cells in a simple battery box. Nothing else except a plastic box to put it in!

When the batteries are flat, they would be charging at up to one Amp, I.e quickly. When they are full, they trickle charge until I swap the AA cells out for the next depleted set. I'd have to experiment with the settings.

No need for a car battery. No need for a charge controller, Just a 3 quid 'Buck converter' and a battery holder for about a fiver, and ten minutes with a screwdriver.

Maximum electrical charging efficiency and minimum cost and simple enough to assemble?

The existing PWM controller and car battery to be used as another project or for times when I run out of AA cells to charge. E.g. as phone charger or irrigation power supply.

Here's the Buck controller, so called because they used to sell for a dollar.