HomeMade Solar Systems
william chan
Posts: 1,326
I always thought that commercial solar charge controllers are too expensive. ( depending on power capabilities )
Anybody thought of making their own charge controllers?
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www.fd.com.my
www.mercedes.com.my
Anybody thought of making their own charge controllers?
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www.fd.com.my
www.mercedes.com.my
Comments
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- Stephen
Is it true?
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www.fd.com.my
www.mercedes.com.my
Leon
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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle
I've used this trick in collage when I didn't have the cash to buy a new battery and the old one didn't seem to want to hold a charge.
Are you saying that newer car batteries would not short out due to sediment accumulation?
I am very interested to weigh the disadvantages and benefits of a periodic overcharge to "equalize" the cells, b'cos it may contribute to particle ejection.
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www.fd.com.my
www.mercedes.com.my
Regarding the lead acid battery, The original lead acid battery separators were wood slats, but now plastic has taken over the role. Additionally, we know a lot more about how to build battery geometry to extend the useful life and get more utility when in sub-zero situations.
The real dilemma that is central to all batteries is that they are chemically active devices that use electricity to charge in one direction and discharge in another. Because they are chemically active, they will degrade when just sitting on a shelf unused in about 3 years. You may have noticed that they don't put the acid in until you buy the battery.
Through cycles of use, there is sometimes 'fallout' to the bottom of the battery, but I suspect that a smarter charger can minimize this. In an auto, the charging rate is not moderated to save the battery. It is a very harsh use.
It is possible that pulsing the charge might give the battery more time to deposit lead ions in the right places rather than a straight, continuous high charge. That might mean less fallout to the bottom of the cell and shorting out the battery. As you can see this is mostly about chemistry, or to be more specific - electro-chemistry.
The usual route is to lower the charge rate in order to preserve the useful life of the battery. Pulsing the duty cycle is similar in results.
But what is interesting about pulse charging is if you have a bank of multiple batteries and a sudden temporary excess of electricity. You might be able to multiplex your charge and distribute a slower rate to many batteries rather than dump the excess electricity as heat. That seems like a good thing with unpredictable solar availability.
It does lead to designing a rather complex charging network to properly reach each battery and to monitor which needs what. And of course, a microcontroller would have to do all that juggling. The pulse width could change both according to the amount of sun and the conditions of all the batteries.
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PLEASE CONSIDER the following:
Do you want a quickly operational black box solution or the knowledge included therein?······
I agree that there are some hobbyist circuits for solar charge controllers, but these are very small systems.
It seems that no hobbyist has ever attempted a 1KWatt and above charge controller before.
For serious solar homes, 1KW is considered the minimum.
Also, synchronized inverters that can work in step with utility supply seems to be out of range for hobbyists.
I am not sure why....
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www.fd.com.my
www.mercedes.com.my
They need 'rather more' testing and certification than normal inverters found in UPSes, inverters used in cars and such.
If a UPS(or similar) fails, whatever on the output goes down...
If a synchronized inverter goes down, it could potentially black out the neighbourhood...
Even if it just goes 'a little out of step' with the phaze on the line it could in theory make a big mess.
I'd rather suggest using a relay, and switch certain types of equipment over on the 'Solar circuit' when there's excess capacity, then back on the grid when batteries runs down.
Fridges and freezers, possibly floor-heating in bathrooms, these are all the kind of equipment which shouldn't mind the transition...
Big water-heaters may be a bit more iffy...
(Mine draws 2KW... Not a nice thing to do to a limited-supply grid)
One thing you will have to consider is switching off the inverter whenever there's nothing active on the solar grid. This is because an inverter is 'not very efficient', and the best car/boat-use inverters I've seen offers no better than 80% efficiency under load, and often quotes a draw of 2 - 3 Amps 'unloaded'....
'Noisy' inverters which doesn't create 'clean' sine-curve AC may be a bit more efficient, but they're not something you'd hook a laptop to...
If you ask me, going for 12V or 24V DC equipment is the best solution.
You get 'in car' chargers for cell-phones, laptops, many smaller TVs, and so on.
And in boating-equipment stores, you can pick up DC lighting, small fridges, and lots of other neat(and expensive) stuff.
I'd love to have a decent solar panel myself, but with short winter days(just a couple of hundred Km from the polar circle), loads of close neighbours and all that...
Maybe a small one to 'supply the toys' later...
Instead I've had to focus on saving electricity wherever I can.
I moved into a new 65sqare meters apartment in November, and then I registered a daily average of 22KWh. I'm now down to about 14KWh, with peaks of up to 17KWh on very cold days.
The most expensive addition to make it possible was a portable 'watt-meter' you connect between an appliance and the socket to read out the usage, and a bucket of timer-switches.
(The one for my bathroom floor was the most expensive at 200NOK, or about $50 at todays ridiculous rates, as it's a model to be built into the wall. I'll still earn it back in a year...)
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Don't visit my new website...
Using DC appliances are what I am doing now after my 800 watt China inverter smoked out when the pond water pump jammed up.
The question now is, should we go 12v or 24v?
I am using 12v now on my half kilowatt panel, but the large current flows causing significant voltage drop is a big problem.
For example, when using 20 amps (only 240 watt), a 0.2 ohm resistance between the battery and load would cause a 4 volt drop which would be unacceptable.
This means that if you plan you wire up your whole house with 12v wiring for 12v appliances, expect to use less than 100w at any one time. This is stupid.
However, if you use 24 volts, then the current is halved, meaning the voltage drop is much more acceptable, you can use up to 480 watts at any one time.
The problem with 24 volts is..... you cant find any 24v DC appliances !!.
Unless you fabricate you own LED lights....
Energy Independence is much more difficult than initially thought.....
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www.fd.com.my
www.mercedes.com.my
(I believe)
What gauge wiring are you using?
One way of getting past the problem with power-loss in long wires might be to use a higher voltage (24, 36 or even higher) at the solar charger/batteries, and at the points of use, put in a good DC-DC step-down converter...
(Add a switch at the outlet to switch it on or off when needed)
If you install a few extra wires you can also add sensors and control to save a bit extra.
(lights switching off automatically as it gets lighter, small fans switching on and off to circulate the air if there's a big difference in temperature. Probably more useful in cold climates... )
I wouldn't use a step-up converter from 12V to a higher 'transfer voltage' though, as having two converters will reduce efficiency.
Gas fridges...
For one reason or another, using gas in a home scares me silly...
There was a major accident in a town near here recently. A big piece of a mountainside came loose and smashed into the side of a six-story apartmentbuilding. The building was moved several meters off the foundations and the first floor was completely flattened.
The fire department was onside a few minutes afterwards, and rescued most of the inhabitants, except 5...
Those in the first floor we can assume died instantly, but I believe one or two were on the partially collapsed second floor...
Why weren't they rescued?
Because the building had an almost full 2000Gallon propane tank in the basement, and it had caught fire. It took days before it had burnt out and the danger of exploding had gone down.
(It is assumed that any survivors had suffocated within the first 6 -12 hours... )
Firefighters are tough folks, and will brave almost anything, but tell them there's a propane tank on fire, or near the flames, and nothing you say will get them to approach the flames. Basement installations in particular as the gas is heavy and will collect in low places, just waiting for a spark...
It was one thing I made damn certain off beforee I signed the contract; that none of the others in my apartmentbuilding was going to use gas for anything.
(Well, except for maybe a barbecue)
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Don't visit my new website...
William, I believe that there are most solar systems are 24V or some even 48V for exactly the reasons you suggest so there may actually be more things available than you think. Also some marine stuff is 24V as well.