The International Cessna 170 Association

Thanks again to all the responses! Finally got back on the ground to read the thread! The ammeter was, indeed, showing a positive deflection of 30-55 amps during the flight. Sorry if my term "draw" caused confusion. I can see where it might. I did "jump" the airplane (maybe should have said used a Chevrolet 2500 external start unit! ) with the master switch on, and the ammeter showed an immediate positive indication.

So far, since returning home from the avionics shop, I have been able to charge the battery to what appears to be a full charge. Sometime next week I should be able to check if the charge remains after sitting for a while and go from there on deciding how to proceed. I'll post more when I know more!

Thanks again,
Joe

Gene's description of the charging system was pretty good. This isn't intuitive, and not all aircraft work this way, so take some time to think about it. (This goes for all of us.)

I would be very, very careful with that battery. Someone else commented that 2 years on a Gill is par for the course, and I'd second that. 55 amps into a battery is a lot, and for any amount of time that would make me nervous. Over the years I've had one battery flat our explode, and another bubble over and spew massive amounts of toxic fumes. Fortunately both happened in cars, not in planes. Had either happened in a plane, you could definitely be a bad situation. I'm not one for throwing money at things, but in the grand scheme of things $175 for a battery is not a big expense compared to the consequences. Especially since yours is effectively at the end of it's service life anyway.

DEM

Bruce Fenstermacher wrote:Why would you try to turn something electrical on, increasing the load, in reaction to a high electrical load?

Bruce, I wondered about this as well but if I suspected I had a run away alternator or generator wouldn't turning on every electrical load (except the radios which I'd turn off) help to save the battery?

Gary, sitting in my Monday morning pilot seat, I did not suspect a run away alternator. I was focused on why a load would increase with no change but decrease when a load is added.

You know, sometimes George's explanations of things are so in depth, I read in amazement. My emotions go from 'how the hell does he know this" or how the hell does he remember this" to wait a minute this has got to be BS, I need to fact check this and shoot holes in it. Then finally resignation, he is right again. Feeling stupid I didn't remember something I knew.

In fact I've seen exactly what George described many times. Difference was the amperage was lower thus less concerning. Many times, and several with airplane batteries , I've attempted to bring a dead lead acid back to life using a battery charger. Initially the charger will show no amp draw. But left long enough the draw on the charger might increase. In this case being a less capable charger the levels are in the 2 -12 amp range. The charge rate would increase until it finally decreases as the battery charge increases and the charging regulator circuit cuts back the charge.

The tricky thing as previously noted is the amp meter is showing the load on the battery. With power being supplied to the battery a load would show on the negative side. Lets say you turn on your landing light drawing 15 amps and the engine is not running, the amp meter would show -15. You start your engine and like most of us a 30 amp generator. Because of the draw of the start and the draw from the lights the regulator calls for the generator to put out it's full rated 30 amps. Your amp meter would only show +15, a 30 amp positive spread from the -15. We would think nothing of it. However if we turned off our landing light and the generator regulator remained high, the amp meter would jump to +30 until the battery is charged then drop. Most of us would think nothing about this. We may not even notice.

Bruce Fenstermacher wrote:... You know, sometimes George's explanations of things are so in depth, I read in amazement. My emotions go from 'how the hell does he know this" or how the hell does he remember this" to wait a minute this has got to be BS, I need to fact check this and shoot holes in it. Then finally resignation, he is right again. Feeling stupid I didn't remember something I knew. ...

I know the feeling exactly! I exhibit Christmas colors perennially; green with envy at the erudite entries I read or red with embarrassment at the numbskull post I typed.

Your problem Bruce is that you have too much experience. Your reasoning here may be getting "influenced" by your helicopter electrical system which I bet has the ammeter or load meter between the bus and the starter/generator circuit rather than the battery and the bus.

One thing George has yet to explain is how switching the strobes on and off changes the draw by 25 amps. Whelen strobes draw around 7 to 12 amps depending on the type of power supply.

n2582d wrote:

Bruce Fenstermacher wrote:... You know, sometimes George's explanations of things are so in depth, I read in amazement. My emotions go from 'how the hell does he know this" or how the hell does he remember this" to wait a minute this has got to be BS, I need to fact check this and shoot holes in it. Then finally resignation, he is right again. Feeling stupid I didn't remember something I knew. ...

I know the feeling exactly! I exhibit Christmas colors perennially; green with envy at the erudite entries I read or red with embarrassment at the numbskull post I typed.

Your problem Bruce is that you have too much experience. Your reasoning here may be getting "influenced" by your helicopter electrical system which I bet has the ammeter or load meter between the bus and the starter/generator circuit rather than the battery and the bus.

One thing George has yet to explain is how switching the strobes on and off changes the draw by 25 amps. Whelen strobes draw around 7 to 12 amps depending on the type of power supply.

I saw that as well, Gary,...but the major question in the thread was about the "charge rate" (misidentified as "load") and I didn't want to misdirect the thread topic onto lesser subjects or divert the thread.
The answer to your query is likely found in the electrical schematic of the particular serial-number airplane coupled with the electrical-load analysis of the airplane. I.E., how do you know that pulling his "Strobe" switch to the ON position...only energized his strobe system? How do you know that it did not also/simultaneously energize an old rotating-beacon drawing another 10 amps?

Bruce Fenstermacher wrote:....wait a minute this has got to be BS,.....

As usual, Bruce is also correct. It's BS. ( Battery Stuff.)

BTW, Folks,... I've had a battery "over-charge" in flight. It was back in 2002 on the way to the Las Vegas Convention, and I wrote an article for the 170 News about it, largely about how not to change out a generator.
The scenario was created by a friend (another Assoc'n Member actually, who will remain blameless/nameless in the story) who works in the electronics field as a knowledgeable professional in a highly-technical area of electronics. As the result of his superior knowledge about such things I willingly accepted some advice he gave regarding a condenser/capacitor filter to be installed on the old vibrating-points style of regulator installed in our airplanes.
Now, to be truthful, I knew about this already, it is an old trick applied in the late '50's/'60's automobiles before the changeover to alternators, and it involves installing in parallel to the armature a condenser/capacitor to provide an electrical "shock-absorber" to the vibrating points to reduce arcing and burning, thereby extending the life of the regulator while simultaneously reducing electrical "noise" in the AM radio-sets of that period. (Those of you familiar with the old "points ignition" circuits of those automobiles already know that a capacitor/condenser was in parallel to those ignition points, the purpose being the same...to prevent premature "burnout" of the points. The condenser acts as a "shock absorber" by absorbing the excess-current at the moment of points-opening and thereby preventing sparking/arcing of those points.)

The friend advised me to install one onto my regulator field to reduce electrical noise and thereby improve reception in the 100 Hz range of my KLN88 LORAN (which was my sole navigation radio in the airplane at that time.) Without questioning him I did so, because I recalled the history of this matter. (Notice that he advised the installation onto the field terminal of the regulator. (If installed at all, it should have been installed on the ARMature terminal of the regulator.) That is what I should have questioned but did not. In effect, this did not protect the vibrating points as much as it provided a direct Short-to-Ground for the field-windings of the generator, which makes the regulator invisible to the generator. In fact, if you wish to test whether or not a generator is failed versus the regulator being failed...this is exactly what you do...ground out the generator field and see if it generates. If it does, the generator is good, it's the failed regulator that you have electrically isolated from the system.)
Well, Cleo and Louise Bickford in a borrowed 170 and Jamie and I in N146YS left our ranch strip early to make a lunch stop at Midland, and it was after about 2 hours enroute that Jamie mentioned "What is that sulfur-smell?"
I glanced over at the ammeter and saw it was solid on the 35A range, so I quickly pulled the C.B. on the Gen and the ammeter went to Zero. We landed a few minutes later and while Jamie and Louise set the picnic table, I pulled the cowl and removed that condenser, and using a water hose, flushed out the battery box and washed down the firewall. I topped the battery with water and put it all together again.
We ate lunch and took off and after about 20 minutes noticed the ammeter was still stuck on 35A, so again I pulled the Gen C.B. and completed the flight to our first overnight in Ruidoso, N.M. where I ordered a new generator. (The generator field was burned-up/permanently grounded.)

This how you discover an overcharge condition in flight: Watch your ammeter and after a few minutes the battery should be sufficiently recharged from the engine start that it should be at or near "zero". Remember, an ammeter indicates battery charge-rate or DIScharge-rate.
(If you want to know "load"...then you must pull the C.B/Fuse on the gen/alt and see what the ammeter shows (which should be a discharge indication.) This is NOT a procedure to be used ordinarily, but is only a simple method to do so. Pulling your gen/alt CB/Fuse in-flight is not ordinarily done unless the unit has failed, because doing-so can produce other failures in some circumstances too intricate to discuss in this thread.)

Meanwhile, I hope you all have developed "electrical load analysis" on your airplanes. Use the published load figures shown in your appliance manuals...NOT the CB/Fuse sizes to determine this matter, as those do not reflect appliance load but only reflect wiring capacities.

Hope this helps.

George, how long did that battery last after topping it off with Midland tap water full of salt, Flouride, Arsenic, and Selenium?

It was replaced after the return home because of my distrust. (I am a believer that batteries are not meant to start engines. They are an emergency source of electrical power in the event of failure of generated-electric-power sources. My idea of skimping on batteries is to buy the common types such as flooded cell (usually on land-equipment) or AGM to avoid acid spills in my expensive battery box.)

WhooHoo! Merry Christmas to me!! Went to the airport today and flew with totally normal electrical indications! Apparently all she needed was about 2 hours on a charger (1 week ago) to come back to life. Thanks again for all the advice! I'll tuck this event away for the future and hopefully won't need it again.

I hope each of you have a Merry Christmas and are looking forward to a great New Year!!

Joe

Aryana wrote:

gahorn wrote:Remember, an ammeter indicates battery charge-rate or DIScharge-rate.

This is where everyone went off into the weeds initially on this thread. Nice write ups from everyone and have I ever told you guys how much I hate dealing with electrical concepts? I suck!

I am a graduate of a course in the Smoke Theory of Electronic Devices below I also do a "Groundhog Test" after any electrical work on my 170. Look away from your work, reconnect the power...if you see your shadow, then you have some more work to do.

Smoke Theory of Electronic Devices

Introduction

From the basic concept of transmission of electrical energy in the form of smoke, a better understanding of the mysteries of electrical components, especially those manufactured by Lucas, a British manufacturer, is provided.

Theory of Smoke

Smoke is the thing that makes electrical circuits work; we know this to be true because every time one lets the smoke out of an electrical system, it stops working. This has been verified repeatedly through empirical testing by countless EE212 students.
When, for example, the smoke escapes from an electrical component (i.e., say, a Lucas voltage regulator or a 741 Op Amp), it will be observed that the component stops working. The function of the wire harness is to carry the smoke from one device to another; when the wire harness "springs a leak", it lets all the smoke out of the system. Once this happens, nothing works afterwards. For example, starter motors were frowned upon in British automobiles for many years, largely because they consume large quantities of smoke, requiring very large wires.

Conclusion

It has been noted that Lucas components are possibly more prone to electrical leakage than either Bosch or generic Japanese electrics. Experts point out that this is because Lucas is British and all things British leak. British engines leak oil, shock absorbers, hydraulic forks and disk brakes leak fluid, British tyres leak air, and the British defense establishment leaks secrets ... so, naturally, British electrics leak smoke.

Not everybody went off into the weeds on this thread. Everybody didnt read what was posted! D