redbaron1982 Posted February 11 Report Posted February 11 Can the battery minder be connected to the APU port without having to turn on Master? My batter charger / minder has a procedure that indicates that master has to be on. It's a paint to have to open up the tail cone access door, remove tha bettery cover, etc, to connect the minder directly to the battery terminals.
DonMuncy Posted February 11 Report Posted February 11 The easiest way is to run wires from the battery itself to a convenient spot that is accessible without having to open the tail cone door. Some people have run it up to the hat rack area. 1 1
PT20J Posted February 11 Report Posted February 11 I'm not sure why you would need to turn the master switch on to connect a battery minder. The master switch just connects the battery to the ships electrical system which will have some drain on the battery. With a battery minder you are trying to float charge the battery and draining it at the same time is counterproductive. In order to use the aux power receptacle, you need to apply a voltage to the third pin to cause the relay to close to connect the receptacle to the battery. Now your battery minder is splitting it's output between this relay (assuming it can supply enough current to close the relay) and the battery which isn't optimum. Don's suggestion is better. That's what I did. 1
dkkim73 Posted February 11 Report Posted February 11 If you have a TKS door, that is very convenient. Otherwise I think hat rack area is good. You do have to leave the baggage door open in that case.
Bolter Posted February 11 Report Posted February 11 11 hours ago, redbaron1982 said: Can the battery minder be connected to the APU port without having to turn on Master? My batter charger / minder has a procedure that indicates that master has to be on. It's a paint to have to open up the tail cone access door, remove tha bettery cover, etc, to connect the minder directly to the battery terminals. The Battery Minder will switch on and off (I think it was @wishboneash who documented this) so at some point the power to the relay will drop out and then the Battery Minder can no longer sense or charge the battery. Essentially useless. I modified a generic "Cessna" APU connection that has the 3rd +12V leg for holding the relay closed. (example: https://www.aircraftspruce.com/catalog/elpages/jumperplug.php) I connected the battery minder to the + and - 12 V as you would expect, and a very low power 12 VDC (12V and 0.5 A) power supply from amazon on the 3rd leg, sharing the ground with the battery minder. The little power supply kept the relay closed so the Battery Minder could do its thing. I needed 2 things plugged into house power at once (battery minder and the power supply), but it worked. The benefit of this over wiring in something permanent is that it is not permanent. Permanent is better, but there are reasons you may not want to do that. 1
1980Mooney Posted February 11 Report Posted February 11 (edited) 13 hours ago, redbaron1982 said: Can the battery minder be connected to the APU port without having to turn on Master? My batter charger / minder has a procedure that indicates that master has to be on. It's a paint to have to open up the tail cone access door, remove tha bettery cover, etc, to connect the minder directly to the battery terminals. 12 hours ago, PT20J said: I'm not sure why you would need to turn the master switch on to connect a battery minder. The master switch just connects the battery to the ships electrical system which will have some drain on the battery. With a battery minder you are trying to float charge the battery and draining it at the same time is counterproductive. In order to use the aux power receptacle, you need to apply a voltage to the third pin to cause the relay to close to connect the receptacle to the battery. Now your battery minder is splitting it's output between this relay (assuming it can supply enough current to close the relay) and the battery which isn't optimum. Don's suggestion is better. That's what I did. A Battery Minder or any smart charger will not open the solenoid on the APU. The Battery Minder or smart charger needs to sense at least 3 volts before it will allow current to flow. You need a standard power supply with continuous current. Edited February 11 by 1980Mooney 1 1
PT20J Posted February 11 Report Posted February 11 11 minutes ago, 1980Mooney said: A Battery Minder or any smart charger will not open the solenoid on the APU. The Battery Minder or smart charger needs to sense at least 3 volts before it will allow current to flow. You need a standard power supply with continuous current. Good point. I know from experience that the BatteryMinder brand will not turn on to charge a very discharged battery. And, it has to see some voltage for the polarity sensing function. The 12V version will put out a maximum of about 8A and the 24V version about 4A. I looked up the relay and the coil current is less than half an amp so that's probably not much of an issue, but as you point out, getting it started is the problem. Also, if it does pulse on and off as @Bolter pointed out, then it would likely drop out even if you got it connected somehow unless you supply current from another source to hold the relay closed. 1
dkkim73 Posted February 12 Report Posted February 12 Only pic I had handy, a bit blurry, but shows the "approved" connectors from the permanent install kit (to each battery). Takes up a bit more space that the little split plugs. 2
McMooney Posted February 12 Report Posted February 12 (edited) mines ran to the luggage area by the rear hatch. thinking about rerouting to come near the step Edited February 12 by McMooney
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