battery chargers, again

Regardless, any LA battery that is discharged to 1.8 volts is basically finished anyway. It may recharge, but I suspect it won't last long.

The fact that the Kragen chargers recognized the battery was too discharged to be considered serviceable (which is what they were thinking...) is one that the owner must decide. The flip side of that coin is that if your Kragen charger did charge the battery, then the battery failed shortly afterwards, you'd have thought the charger was at fault. They realized that (and that customers would be claiming that the charger 'ruined' their battery, and demanding new batteries) and instead built the system you bought.

OK, in the end: I use an *old* non-automatic charger. Doesn't care, doesn't measure, it just tosses volts to the battery (like your bench charger). I'm happy with it, and had good success with it charging batteries. Sometimes old technology is great.

John, you are skilled enough to build a charger! Just do it...

Or just get a nasty big iron Craftsman charger off eBay. Two transformer taps, rectifier, thermal cutout.

Cheers

Phil Hobbs

I've never had a battery come back from being that dead, and I've had numerous chances to try it (I'm stubborn that way). You'll be lucky to see 12V out of it with the charger disconnected, and I doubt that you'll see that after the first time you touch the key. If you _do_ get the car started it'll just be an opportunity for you daughter to get stranded some place.

One new battery is cheaper than one tow truck ride. Do the math.

Many of the the newer battery chargers seem to do this.. they refuse to charge if the battery is very dead. It's in the preferred algorithm description for NiMH batteries too-- I just had to modify a charging algorithm because people make mistakes and occasionally kill batteries below the minimum charge voltage per cell and you need to be able to override the (usually microcontroller-based) smart charger. And had the same problem recently with a commercial charger for a stacker (sort of a little fork lift). The deep discharge Marine duty battery was too dead for the dumbf*ck little LM339 circuit to turn the SCR on. At first we thought it had failed..

One of the problems with our software-intensive era is that the behaviour of ordinary objects has become arbitrary, like software, instead of merely ornery, like physics.

It's nice to warn people, but building something that refuses to do the job it's built for is poor engineering. (Of course our current plague of tort lawyers is partly responsible, but only partly.)

Cheers

Phil Hobbs

Disagree. I'be done that too many times.

I'm skilled enough to buy a B&K or whatever bench supply from Digikey, too.

John

And a hydrometer so you know what condition the battery is really in. ...Jim Thompson

OTOH, physics combined with real parts can get pretty ornery by itself; there are decision trees that would take a square foot of board to do with diodes and op-amps that can be done with an 8-pin PIC and a less than 256 words of program memory.

I can't agree with you more that building something that can't do it's job is poor engineering. I think much of the reason that software becomes a problem is when people with only software expertise are called on to write software to embody things like charge algorithms. Consequently one ends up with a whole bunch of guesses embodied in the software, rather than a bunch of (or a few) correct conclusions.

FWIW, I'd have gone to Sears first.

But a good lab supply with sufficient current, limited, and settable voltage will certainly work.

(I ised to work for an industrial battery charger mfr.)

Good Luck! Rich

It started OK after about 6 hours at 1.2 amps, started vigorously after charging all night. My wife's car was zero-volts dead a couple months ago, got rebooted from the DSL wall-wart, and it's fine. Lead-acids will sulphate and lose capacity if they sit dead for a long time.

Our insurance covers the truck ride.

John

Software-based products are also opportunities to add self-serving gotchas, like this battery charger thing maybe. Or products that read an encrypted code that allows only "genuine" ink refills or batteries or whatever, and tries to invoke DCMA to protect their monopoly.

I have an Agilent DVM that has a serious hardware problem that they obviously hid with firmware.

The charger has no warnings anywhere. The "charged" LED comes on. The implication to common folk is that a discharged battery can't be charged and has to be replaced. That's the only kind that Kragen seems to sell.

John

I think Phil's point (or the way I personally took it, anyway, as I really shouldn't attempt to speak for him) is that software allows behaviors that aren't at all similar to how nature itself operates. Nature is very, very consistent and once one learns it well, those lessons can be applied in new situations. When software is inserted into the mix, that can be quite a different story where no possible prior experience elsewhere may act to inform expectations.

Prior digital states matter in bizarre ways, sometimes.

Despite some possible advantages, I'll take an analog, physical connection between my steering column and the wheels over a digital, software controlled one almost every time. At least I know how to interpret some of the feedback I get that way based on other experiences in life.

What would be nice is if software people would know enough physics and mathematics to carefully design and thoroughly test algorithms that will behave more closely to their physical analogs found in nature -- or else develop new models that are "readily learnable" from natural experiences elsewhere, so that whatever the behavior happens to be it is close enough to what one might find at our macro scale of life to be considered congruent to natural laws. But that requires a solid knowledge of those laws in order to know which end is up.

Software people involved in embedded work that interacts with nature (as opposed to embedded work, for example, that is about iPods or cell phones, where the nature-part of the system may be limited to knowing the human eye and hand well), should know some electronics, physics, numerical methods, signal processing, and mathematics. In the end, it is the embedded software developer who is bringing everything together into a successful system (or one that isn't.) They must be able to interpret the work of physicists, electronics designers, and so on and be involved early so that issues related to software that others may not be as well informed about can be brought forward earlier and considered. This can include a wide spate, from numerical issuess few physicists may be aware of when they write things down to issues that others should have been aware of, but missed, such as z-space vs s-space. It's always good to have someone else similarly informed looking over the work to help catch things before they are baked into the system.

Of course, if it is a hand-held iPod, you might want someone versed in various media formats and play methods.

It boils down to having an embedded software engineer familiar with the application space, I suppose. And not merely "a programmer."

Indeed. When ignorant, a software programmer may not even realize they are making flawed assumptions on their own or implementing the flawed assumptions of others (such as a physicist's natural assumption that operations and constants are infinitely precise.)

Jon

It is not normal for a car battery to discharge so far over just a month, not in the climate zone your are living in. Unless the battery was shot to begin with or something in the car was left on.

Big mistake :-)

Electronics cars, IME not a good combination.

Why didn't you stop at Bob's place for a beer? He'd have given you a real charger, meaning a transformer, a rectifier, a power cord with plug (or maybe without plug), some old meter, probably all neatly assembled on a piece of plywood with some cinge marks on there. And it sure would have worked.

Until one fine day ... *FOOMP* ... and there goes the "Panazonc Special" output electrolytic.

It certainly was junk if it didn't even have any status display. A good charger must be able to start from zilch. Interestingly, I found out that many designers of SMPS do not have foldback limit, they just error. Maybe they don't know how to do that anymore these days.

But not if you get stuck umpteen miles north of Tonopah, the cell phone shows zero bars and the only thing you see is the bloated carcass of a dead cow. BT.

Anyhow, your car insurnace covers a tow? Ours (Farmers) doesn't AFAIK. Did you have to buy that extra?

John has not indicated how _long_ the "charge" remains on his battery.

Or take a hydrometer reading??

To me, 1.8V indicates a fully "sludged" battery. ...Jim Thompson

AAA.

Ok, but last time I checked they were quite a bit more expensive in insurance rates than Farmers.

But nice when you're back of the beyond with a car full of screaming kids and that cow is starting to look like dinner.

Problem is, back there we couldn't even have called AAA. Because there is no cell coverage anywhere. Luckily we had packed some tools and were able to fix it.

The same happened to me after dusk on the road from Durness to Inverness in Scotland. The old Ford Cortina just stopped, no more electric. Looked around, opened fuse box, the big one was gone. "Oh s..t!" ... no other cars traveling that road at this late hour. I did meet one horse though, alone, just wandering about (you see those a lot there). I seriously doubt it would have agreed to carry me to Inverness. So I slowly walked back and lucked out, found the fuse in the dirt. It had simply fallen out.