Bruce Fenstermacher wrote:When you say all your lights, you are including your 2 landing/taxi lights? And these incandescent or quarts?
If both answer are yes, this is your issue. If you have the 4509 bulbs , each of them pull nearly 8 amps from your system. That only leaves 4 amps for everything else. This is why you are seeing 12.8v and a discharge with this load. You can not continuously run your landing/taxi lights. Turn them off. You should see a positive amp charge and your voltage should go up to an acceptable range.
I have all LED lights on my airplane including 2 landing lights, nav, strobe, and tail positional. The big draws are the LED's but they should draw less than the original 4509 bulbs.
I think my solution moving forward is to be mindful of having my landing lights on. Even at full power, I'm getting a discharge. Perhaps the LED's are drawing too much (very bright AeroLEDs)
And, that voltage is measured at the battery, not downstream somewhere like the cigarette lighter, through an unknown number of wires and terminals, each with an unknown resistance.
I measured it downstream from the cigarette lighter, and even with all the loss from the wiring etc, I got 15V charge at full power with no lights/avionics on, and 12.8V full power with everything on. This should be sufficient—no?
reecewallace wrote:I measured it downstream from the cigarette lighter, and even with all the loss from the wiring etc, I got 15V charge at full power with no lights/avionics on, and 12.8V full power with everything on. This should be sufficient—no?
Do you fly around with "everything" on? If so no, it will not be sufficient. Overtime your battery will go dead. Your battery is only receiving a trickle of a charge for starters requiring a long long flight to recover just from the start not to mention those times you aren't at full power and not at 12.8v.
If on the other hand, you don't fly around most of the time with "everything" on and your voltage is 13.2v or greater, You will likely be OK.
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reecewallace wrote:I measured it downstream from the cigarette lighter, and even with all the loss from the wiring etc, I got 15V charge at full power with no lights/avionics on, and 12.8V full power with everything on. This should be sufficient—no?
Do you fly around with "everything" on? If so no, it will not be sufficient. Overtime your battery will go dead. Your battery is only receiving a trickle of a charge for starters requiring a long long flight to recover just from the start not to mention those times you aren't at full power and not at 12.8v.
If on the other hand, you don't fly around most of the time with "everything" on and your voltage is 13.2v or greater, You will likely be OK.
You're right, I don't fly around with everything on so it's usually not an issue. However, I do a lot of night flying so this requires all my lights—so I may have to dig a bit deeper into why I'm not getting enough power.
The fully charged battery cell voltage is 2.2v times 6 cells on your battery, that equals 13.2v fully charged with no load. The charging voltage needs to be above that. the 13.7v - 14.7v that dave's chart reflects is in line with That, The 14.25v value I gave is average temp value. Your battery is a "source" of electrical power when its voltage is greater than that of the generator like when you are on the ground with master on and engine not running. With your engine running and your generator generating 15v, it is the higher voltage and the 'source' and your battery is an electrical "load". The point I'm trying to make is that your battery cannot be discharging unless it has a higher output voltage than the generator and it isn't possible for your battery to be above 15v. your generator is either not putting out 15v in flight or your ammeter indication is in error.
I used one of these yesterday connected directly to the bus, and it was showing 12.8v while the generator was running with everything on, and 15V while the generator was running with nothing on. Albeit—not sure how this voltage translates to amps
Last edited by reecewallace on Sun Jan 17, 2021 11:55 pm, edited 2 times in total.
Reece, You should perform an “electrical load” analysis of your airplane. Take all of the loads (appliances) demands and add them up. If they exceed the 20A capability of your charging system (generator/regulator) then you will have a discharge of your battery. In that case you have a choice to make: Either reduce the load by turning off some equipment (such as landing/taxi lights) or increase the capacity of your charging system (by upgrading your generator/regulator to a higher-capacity system such as a 35A gen/reg set-up ($400) or convert to an alternator system. ($1500). (estimated materials cost, labor will be extra.)
Keep in mind that only FULL TIME loads are usually considered when conducting an electrical analysis. Landing and Taxi lights are “Intermittent” loads and not considered full time. It is commonly accepted that full-time loads should not exceed 80% of generating capacity. This means that your full-time appliances should not add up to more than 16 Amps with your current 20A system.
Good idea here. I'm going to dig into exactly how many amps each item is drawing and come up with at total. Keep ya posted. Cheers
I don’t know what the specification is, but a 2.2 volt drop under a 20 amp load sounds like a lot to me; that’s 0.11 ohms, or what you might expect from 110 feet of the 10awg wire that’s supposed to be there. I’d be surprised if there’s even 10 feet of wire there. Check the terminals at each end for looseness and corrosion.
Another possibility is that one or more of your electrical accessories is drawing more current than you think it is. With the engine and all accessories off, turn on the master switch. Then turn each accessory on by itself one at a time and the ammeter will indicate what that accessory is drawing by itself. If any one of them is drawing more that it’s manual says it should, and it seems to be working satisfactorily, check the wiring; there could be a high resistance short to ground somewhere.
Miles
“I envy no man that knows more than myself, but pity them that know less.”
— Thomas Browne
