Alternator Questions

[Wes Polsley]

For those with an alternator, which one are you using, and what load are you typically showing in flight?

We recently had an issue where the batteries were dead after a night flight (nav, strobes, and landing light as needed). Most of the flight was landing practice so the average rpms were lower than normal, but should not have been enough to drain 2 new 12V batteries. We tested the alternator, voltage regulator, and wiring for grounding and resistance. Everything checks out. I’m wondering if we have paracitic draw from something we haven’t found yet. If that’s not the case, I’m concerned about the output of the alternator, a Jasco (now Hartzell) 24V/70A model. We recently replaced the alternator and voltage regulator and both have been tested so I don’t believe those parts are failed. During normal cruise we are only seeing about +2A on the meter.

Ay suggestions or commentary? Normal flights at higher rpms seem to do okay maintaining the batteries, but that’s day vfr, so no 15-20A landing light use.

[Wes Polsley]

It had the batteries when we got it. I had the same question (1×24 vs 2×12). Not sure why it was setup that way. This was not a 24V -E model originally (as far as I know). My dad was the one flying, so I don’t have an answer re the landing light, but it’s possible.

[JAMES GRAY]

p.s. the only 24 volt factory-built planes were the L-5G models. Post war, circa 1947-1951, the Navy and Air Force converted most of their earlier L-5’s to the 24 volt standard they adopted for all of their aircraft. It appears that 03971 was converted at Cherry Point in 1948 and the record card was changed to reflect the OY-2 conversion in 1949.

JG.

• This reply was modified 4 years, 10 months ago by JAMES GRAY.

[Wes Polsley]

Do you have the record for our aircraft? 03977? I would be interested in seeing anything you have.

 

Wes

[admin]

Wes, I have digitized copies of the USAAF and Navy records for ALL 3,590 L-5’s delivered during WWII. Having looked at every single one of them multiple times I’m also very good at interpreting the acronyms and numerical codes on them. JG

[Sam Taber]

Hi Wes,

 

I sent this On 6/15 but it did not go through to the forum.  Just saw it was not posted.

ST

Typical 24VT systems ( on older planes) has a current draw of about 2-3 amps for just  the master(battery) relay.  Once the battery is recharged — Master relay -2-3 Amps, Radios 1-3 Amps depending on what type and how much you transmit.   Nav lights will draw 2-4 Amps.  Strobes 1-3 Amps in pulse load. Interior lighting 1-2 amps.   So 7- 15 Amps  night load without landing light on.   That would be a normal load range with battery fully recharged after start up.(20 – 30 min after Takeoff).

Sam Taber

[Author]

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