OT - Charging circuit on small gas engines

No doubt they did.

One can only hope that they minimised noise of various kinds, virtually eliminated coloration of the data by their test set and did a few sanity checks before publishing data.

The good news is that they *could* use various capacitors and inductors as transfer standards, measured with a calibrated bridge to get an idea of where inaccuracies might lay.

--Winston

Reply to
Winston
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From what I've been able to find/determine about some of the newer hand-held battery analyzers (approx $300 price range), this method of applying a small load and then pulsing the battery is how the displayed results are calculated.. allowing a thorough test to be performed by a small instrument.

I've had capacitor ESR meters for years, but they're generally not reliable for battery testing, and some designs just won't tolerate an input voltage at the test input. Many cap ESR testers' operating frequencies range from 1k to 100k (single frequency, not variable or selectable) possibly with the majority of testers utilizing 1k to 10kHz.

I bought an inexpensive dedicated (1kHz) digital battery impedance meter a while ago, speculating that it's measurement capabilities would (be useful) help determine the matching/reliability? of individual rechargeable cells.. and possibly the condition of health of lead/acid batteries, but I haven't investigated the meter's practicality as far as LA/car batteries after seeing that the meter's readings were essentially only comparison readings.

From what I think I understand about similar testers (capacitance value, ESR, current leakage etc) they're essentially AC voltmeters, and the lower cost/non-microprocessor types generally use an IC for dual slope integration? to establish a reading from an internal/predetermined sample/component. It seems that the meter's usefullness would mostly be of use for comparing readings of nearly identical cell/battery types, but otherwise just a tool to gather readings which could be useful for statistical data (which may or may not be useful after many entries).

Reply to
Wild_Bill

It might be good if you buy second-hand batteries replaced on a schedule. To test and accept/reject new ones you'd need the battery manufacturer's spec sheet.

I measure a battery's remaining capacity as how long it will run this laptop. When the screen brightness changes the inverter has just shut down.

jsw

Reply to
Jim Wilkins

They didn't even bother to draw a Kelvin connection for the voltmeter. In my experience engineers who know they need one make sure to show it.

jsw

Reply to
Jim Wilkins

Yep.. and the issue of buying used batteries (for rejuvenation by desulphator) for off-grid power was where I first encountered the use of "testing battery internal resistance", years ago.

One example I forgot to mention which may prove worthwhile for using a battery impedance meter, would be routinely checking SLA batteries for large UPS batteries, if the batteries are of similar capacities/models, and most from the same manufacturer. Fleet vehicle maintenance personnel may also find these meters helpful when used periodically.

Specific battery specs are becoming more readily available more recently.. perhaps just to appease potential buyers, moreso than actually being factual.

I feel the way you do about battery *packs*.. their worthiness will become evident in real-world use. I generally put stickers on rechargeable packs for noting dates and charging durations. I thought that one good use for the battery impedance meter would be to help match cells for pack building.. and maybe it would be after some rather extensive testing experience (hundreds of cells).

Although I have several battery load testers (and hydrometers) for large LA batteries.. load testing can be very useful, but not very scientific without a precise timer and/or other means of plotting the battery's output during the test (also temperature). Overall, I'd say load testing is a reliable good/bad test (no large grey area) when checking high capacity (automotive sized) batteries.

Reply to
Wild_Bill

(...)

I suspect that is a documentation problem rather than an engineering problem. Their data are strewn with sub-milliohm impedance readings that would be just about impossible to get without a Kelvin connection.

Communication can be challenging.

Perhaps you have experienced the frustration of seeing the final product of your efforts irreparably damaged because someone higher in the food chain couldn't keep their grubby hands off your source code?

--Winston

Reply to
Winston

I could, but the owners manual says not to run the generator without a battery connected. I don't know if the previous owner damaged the system by doing that. I suspect that it didn't or I wouldn't be seeing any voltage being sent to the battery to charge it.

RWL

Reply to
GeoLane at PTD dot NET

It's feeding 16V to the battery when it's running and the battery is connected.

How many amps might I anticipate being sent to the battery? I didn't have much success measuring the amps last evening, but I may have time to try that again over the weekend. I don't want to fry my VOM. I had tried on the 10A setting and didn't get a reading. I dropped to the next lowest range - 500 mA, but still didn't get a reading.

RWL

Reply to
GeoLane at PTD dot NET

With current that low, you can put a 1, 10, or 100 ohm resistor in series to measure voltage drop, and calculate current. For example, if you measure 0.5 volts across a 100 ohm resistor, I = E/R = .5/100 = 5 mA.

If you are measuring 16V DC across a 12V lead-acid battery at low current, something is wrong with the measurement or the battery. Do you have an oscilloscope? Maybe your voltmeter is measuring peak voltage of spikes, although that's not something I would expect if you are actually using a mechanical-meter-movement VOM rather than a DVM, and are measuring on a DC volts range.

Reply to
James Waldby

You've piqued my curiosity. Since when has there been a Harbor Freight in NH?

Reply to
Steve Ackman

(...)

(...)

Taking those two symptoms at face value, I'd say that at least one of the cells in your battery has opened up and the battery is no longer 'fit for service'.

I wonder what voltage reading you would get with a 'tested good' car battery?

--Winston

Reply to
Winston

n

e:

It opened in December. It's on Rt 101A in Amherst between Nashua and Milford, across from Lowe's near the Wal-Mart.

You know where Circuit City used to be? (Traditional NH directions to snag unwelcome refugees from MA)

One clerk told me they stock only about 30% of what's in the catalog, but it's a big store with a good selection.

jsw

Reply to
Jim Wilkins

You mean that with the engine running you measure the voltage across the battery and it reads 16 volts?

I would be very leery of checking amperage with a multimeter. they usually have almost insignificant ranges for cars n stuff.

But you don't really need to know the amperage as the voltage will tell you all you need to know. Your maximum charging voltage should be about 14.1 - 14.2 for a 12 volt battery. If you hold the voltage to that level the amperage will be safe.

Reply to
john B.

Too late, that's a symptom of one or more bad cells. Sometimes they can be partly restored by forcing current through them at a higher voltage like 18 - 20V if you have a lab power supply or home-made adjustable charger.

The battery that came with my Sears garden tractor was dead (like much of the machine) but took a few milliamps at ~18V, then the current slowly increased until after a day it charged normally. I got 4 more years from it until the 12V winch ruined it, then I put in a WalMart battery that died irreversibly in one year. Now it has one from BatteriesPlus that has survived two winters at least.

jsw

Reply to
Jim Wilkins

You might try taking a current measurement with a small lamp of a known operating current (the current can easily be looked up online, by the lamp number).

This way, you can determine that the meter will give a reading in the appropriate ranges, of close-to published specs.

Reply to
Wild_Bill

Or put the lamp across the battery without touching the charging leads and see if the current increases, proving all your connections are good.

jsw

Reply to
Jim Wilkins

I suspect your battery is "pooched"? (or fully charged - either will draw no current and allow high voltage) Most are 1.5 to 3 amp.

Reply to
clare

And if the battery is no good, the voltage WILL go higher on a resistance regulated system (which is basically what he has)

Reply to
clare

...

And ... do you know that there is now another one in MA? In Danvers, on Rt 1. I've been meaning to visit, but haven't yet. Bob

Reply to
Bob Engelhardt

Ah... a part of the state I never went to even when I lived there.

No. I don't even know where Nashua, NH used to be. I think it's officially part of North Massachussetts now, isn't it?

Well... we still own the house in Lisbon. I think we'll test the market this spring though and see if we can get rid of it without taking too much of a bath. Anyway, even if we still lived there, fuel would still cost way more than shipping on a typical order. I *might* do it for something big, like a milling machine, lathe, etc. just to get eyes-on before opening the wallet.

Reply to
Steve Ackman

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