Friday, September 27, 2019

battery testing 2

Using the small automatic tester to check car sized batteries takes much longer but gives useful sorting information.

Continuing with the theme of battery testing but on a different scale, I have changed the loading of the battery tester to draw more current. The three large resistors are in series across the load terminals of the tester. The resistors are the three rectangles with my handwriting on them.

[click any pic to enlarge]

The handwriting is the measured resistance in ohms. Since the resistors are in series, the three total 15.7 ohms. Each are rated at 22 watts so the three theoretically could dissipate over 60 watts. With only 12 watts used in this test, the resistors get very hot, too hot to touch, hot enough to boil water. The metal screen helps to cool them.

I would first charge the battery fully with a separate charger and let it rest overnight. A good battery would measure in the range of 12.4 to 12.8 volts. The tester was then set to discharge the battery to 11 volts and the test started.

The tester checks the battery voltage and offers to start with a default of 10.5 volts but I did not want to discharge the batteries that low.

With a freshly charged battery the current drawn at the start of the test is about 850 milliamps (0.85 amp), or about 12 watts. This is a modest rate for a car battery. The tester is specd at a maximum current of 3 amps so this is well within its range. A load of 12 watts might simulate one charging cell phone for example or a bright LED light.

The test takes some time. I managed to check four batteries in the past couple weeks including an almost dead battery that was then returned for recycling.

I expected this battery to test weak. It had been removed from my car three years ago. It would start the car ok in the summer but was not reliable in the winter. This particular battery had continued in service here in a small solar UPS in the shop and true to form, it would last only one night in the dead of winter powering a 12 watt LED overnight. If it was cloudy the next day, the LED would not last till morning.

This battery took almost 14 hours to discharge to 11 volts and gave a result of 10.3 amp hours. I charged it again, repeated the discharge test and got 10.7. So there was some indication of repeatability to the test.

The new battery I purchased (the one in the first picture) is now installed in my car. As expected, the factory fresh battery scored well at 54.5 amp hours. It took three days to discharge!

So I now had a range for good to bad.

Continuing with three other lead acid batteries, I managed to get clear, unambiguous ratings of the battery capacities, all at the same rate.

The "old" battery that I just just removed from my car will now go to the UPS. It tested 37.2 AH.

Video is here.

Thanks for your interest.

George Plhak
Lions Head, Ontario, Canada

[update Oct 6] Great comment from Len Warner:
This is very sensible testing but one should not deep discharge automotive batteries unless there is a real need to know. However, all this seems valid: new battery tested to establish a reference; replaced car battery tested to qualify it for ups; and old ups battery tested to confirm it's ready to scrap. But the other two tests have cost you a cycle life.
Another test you haven't done is charge retention: ancient automotive batteries tend to have lost plate material, which accumulates at the bottom of each cell and shorts it out so the battery won't hold its charge long-term. It also tends to affect cells unequally, leading to cell imbalance and overcharging.
Traction batteries and leisure batteries should be more resistant to deep-cycling because of stronger plates and sumps for debris.

Tuesday, September 24, 2019

visitors

Hello!

I am humbled and grateful for your interest. And for your comments!

Each day is different. This chart is today. Usually I have more visitors from Canada.


The data is page views by country over the past 24 hours.

[click pics to enlarge]

Most often Google brings you here or you've clicked a web link. You stay to read, on average, for almost two and a half minutes!

The "bounce rate" for this site is very low, which is good. This shows that my readers stick around to read more.

Please know that I appreciate your visit!



Thank you for your interest.

George Plhak
Lions Head, Ontario, Canada

Tuesday, September 17, 2019

diy lamp update

Some learning from five years outside. I have taken down my lamps to make changes. Let's see how they are weathering.

My concept was to build simple safe cheap reliable rugged outdoor lamps using common materials: wood, found glass, cheap LED chips and "wall wart" power supplies, all re-used if possible.

It was important to me that my lamps give efficient light without drawing attention to themselves.


This one (Model upside down L) is shown attached to a corner of my deck under the railing. I mounted it low, about knee height off the ground. The light shone downward on the path and was limited upward to the horizon by the top of the lamp. There was no glare from these lamps as you walked toward them, just illumination of the path. Would the design be classed as "full cutoff"?

I am pleased with the result. They were bright! Each used only 2 watts at 9 volts from an old printer power supply. The cost was about $5 each for new and reused materials.

[click any pic to enlarge]

A gray connector box is barely visible on the other side of the post. The wire carrying low voltage DC to the lamp passes through a hole in the post to the connector box. I tried to hide the wires and plug entrances for rain and bugs. Not very well it turned out.

I liked using old glass telegraph insulators for the lamp lens although I tried all sorts of glass. Some, like the insulator, were difficult to mount, especially for outdoor year round use.

The idea was that the glass object would protect the LED chip from the elements yet pass the light in a pleasing and interesting yet effective dark sky kind of way.

A common material I used was 2x4 lumber, usually without any protective coating so that the wood weathered natural grey. I avoided cracking of the wood by selecting evenly grained sections with no knots or visible cracks. I pre-drilled all the screw holes. Cracks did form over the years but they were minor.

I had intended for the lamps to look rustic in a modern way if that is possible?

These lamps were not connected this past winter but had illuminated the pathway perfectly for the four years before that, five years total. I didn't know if they still worked.

On the bench connected to a power supply!

Perhaps I shouldn't sound surprised?

Let's have a look inside. To do that, I have to destroy them.

One of the lamps has been a bug home for a while, the other is clean, apparently a better seal.

The bug is alive. No bugs were harmed in this research!

The seal was a bead of silicone around the skirt of the insulator where it touched the aluminum sheet. I had trouble getting the silicone around where the wires went through the sheet.

The thin aluminum sheet is a piece of natural finish roof flashing. It serves as reflector, heat sink and support for the bale wire. The glass hangs from the bale wire so that the silicone has backup. The glass insulators are relatively heavy. The aluminum sheet with it's attachments form a sub-assembly that gets screwed to the wood frame enclosing the electrical part from the weather. There is a cavity in the wood to fit.

It was crudely done.

The back view before removing the bale wires and peeling the aluminum sheet away from the glass. I can see that I used both steel bale wire (the thinner rusty wire) and aluminum wire (thicker and shiny). I recall that the aluminum was easier to bend to the required shape. The steel, although thinner was more stiff.

The smaller rectangles are pieces of aluminum bar to improve heat transfer to the thin sheet. The LED chip is mounted on the other side with two screws. There is thermal compound between the chip and the bar and between the bar and the sheet.

They don't look the same because I tried a couple of variations. The one of the left was a later model. Notice that the silicone fills the holes for the bail wires but not the electrical wires!

I'll bet that's the bug entrance!

In this pic, the bug house LED is the bottom one. Surprisingly clean.

The top one has suffered some rusty corrosion to one of the two bolts but not the other.

Both LED's still work as I showed with the bench power supply. I wouldn't count on the top one lasting much longer just by appearance. There seems to be some darkening at the top corners of the COB array potting.

This LED is from the dark sky shielded lamp. As you can see, it did not do well at all. The LED no longer works.

I had used a small glass jar as a lens for this lamp. I found that it almost immediately showed signs of moisture inside the glass. None of the screws I used were rust resistant and the lid of the jar rusted badly.

The connector boxes were ok although 2 of 4 became bug houses. Corrosion of the cover screws was a problem. The screw used is an unusual fine metric thread (M4x0.5 15mm long) so finding a suitable replacement is difficult. I like these boxes otherwise for outdoor use. The one has been in direct sun and rain for five years.








This autopsy of my lamps after their "life test" shows what needs improvement. My projects are never perfect the first time!

Your comments are welcome. Please browse the other articles in the series.

Thank you for over 55,000 pageviews of this DIY Lamp series so far!



George Plhak
Lions Head, Ontario, Canada

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making a lamp from a 2x4
best light at least cost - about testing bright diy leds at home
diy testing of led lamps
diy 1 watt led update
diy garden lamp progress
a shielded low power diy garden lamp
diy lamp update - this article


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