Electrical Power Load

·         John Ruffe

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Hi Doug. My question relates to the charging capabilities of the current 3300 engines fitted to a J230 factory aircraft fitted with Dynon D10 EFIS, 2xVHF, transponder, Garmin 296 and standard analogue gauges along with an iPad running OZ Runways. The battery is near new. Can the iPad place undue demand on the system?? The reason for the question is that a flying buddy recently burnt out his stator and I am running a similar configuration. What else might contribute to his problem?

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John R.

·         Doug Smith

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Hi John,
The avionics typically don't draw too much - it's usually lights that are the power use culprits. However, some device chargers are electronically "dumb" and can use a fair bit of power AND make a lot of EM noise. When we did the Electrical Load Analysis for the aircraft we typically assume 1 constant 1 amp draw on the 12V socket so (depending on your other electrical equipment) if you're using more than that you might be working the system harder than ideal.

The big current draw just after engine start can also be a culprit - especially if the battery was a little low, then the engine is started and all the accessories are turned on straight away (at low RPM the alternator doesn't have the capacity it does when its up to speed, so high electrical loads at low RPM can stress the system). A trickle charger or similar can help there too, by keeping the battery topped up.

Generally, there are quite a few things that can act to overheat a stator (too many to go through here as my typing isn't that good!) so if you're worried, a call to Jabiru might be in order.

Regards,
Doug.

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·         Russ

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What is the safe maximum current draw in my 160 jab..........( running an engel fridge )

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·         Doug Smith

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Hi Russ,

Depends a little on the vintage and which alternator is fitted to your engine... most of the 160s have the 200W alternator which can produce about 17 amps continuous. Depending on other equipment in the plane you could have as much as 10 - 12 A available or as little as none! To give you an idea, most small GPS units use about an amp, as do radios and transponders. EMS / EFIS units vary between about 2 and 6A (though there are monsters out there that use more). Landing lights (50W) use a little over 4A. Strobes can be pretty hungry too.

Bear in mind that the "200W" figure is based on assumptions of either cruise or circuit operation: it's RPM based and if your RPM average too low you can be getting nothing at all.

Considering how good Engels are at draining the thumping great big batteries they put in diesel 4WDs you'll have to be careful to safely run it off your Jabiru! That said, from memory the Engel doesn't use a lot of current, so if you only have it unit turned on when you're travelling (not overnight) you'd probably be ok.

If you want a more exact answer let me know what equipment and systems your aircraft is running and the power draw of the fridge.

Regards,
Doug.

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·         Russ

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Ok...........2007 stock std 160C. ( all usual elecs )

running garmin 296.
engel draws 3.3 amps...approx

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·         Doug Smith

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Ok, by the sounds of it you'd have the capacity to run it in flight... You'll just have to be careful where and when - not on descent with the landing lights on etc. And the running time with the engine off should be kept minimal.
D.