GPU for 1995 M20J MSE

[Derek]

Is this the sort of device I need to plug into the auxillary port on the fuselage in order to run the avionics on the ground for testing/learning/configuring?

https://www.aircraftspruce.com/catalog/elpages/audioathgpu.php?clickkey=6344

It's the M20J MSE with the 28v electrical system.

[elimansour]

I think this one will work better (since I believe that you are not supposed to charge through the GPU port): https://www.aircraftspruce.com/catalog/elpages/portPowerCharger24ces.php?clickkey=6344

I bought it and use it regularly to run the avionics on the ground.

[Derek]

This product being 24 volt and not 28 isn't an issue?

I didn't realize that you're not supposed to charge through the auxillary port. Haven't seen details in the poh about it.

How are you supposed tocharge? Open the inspection panel and tap right into the battery with some other device?

I do have a trickle charger which my A&P put through a grommet into the cargo area so I can run a wire in through the cargo door to keep the battery topped off. But it's not enough flow to run the avionics for a while or do a faster charge in the event of a dead battery.

[ArtVandelay]

The only downside I can envision is if there is a voltage drop across the relay, the charging circuit won’t be able to properly charge the battery, overcharging it. If just topping off the battery or using it to play with your avionics I would not worry about it.
If connecting and leaving it overnight, then I would connect it directly.


Tom

[Derek]

What about the 24 volt thing?

If the system is 28 volts shouldn't I be using a supply which provides that exact voltage and not the 24 volt one suggested by @elimansour?

[EricJ]

Using a 28V plug-in should charge the battery the same as the alternator would, as a constant-voltage charge source.   It shouldn't hurt a battery that's in good condition (e.g., not dead or near dead).

I don't know how the relays are wired on the 28V systems, but on my 12V J model if the 14V GPU is plugged in and it will power things and charge the battery if needed.

[carusoam]

Things to consider...

The GPU plug has a safety protection to keep it from being reversed polarity wise...

28 and 24 volts are nominal and actual numbers for the same thing...

14 and 12 volts should be avoided on a 28/24V system... and verse visa...

The GPU plug is best left for brief Jump starts, on mildly discharged batteries...  using it for hours on end has a relay that is constantly activated... the life of that relay is pretty much an unknown... and sure to be expensive to replace in the field, at an unknown airport...

charging the battery is best accomplished by avoiding the GPU as well... Smart chargers are often confused by the safety polarity device.

Battery Minders easily get wired without using the GPU...

For other ideas regarding using a power supply for doing instrument work... there is a thread or two for that...

A search for power supplies probably will reveal what others are using... some MSers have some pretty strong EE skills...

realistically...  testing/learning/configuring?   If it takes a few minutes here and there... use a battery minder. It can charge the battery, and condition too...

Compare how many amps you are going to need, to how many the BM can produce...  avionics don’t use much electricity... old lights, motors, and heaters usually use the most...

Really important... check with your mechanic before any guessing occurs... don’t let the smoke out of any electronics... it is hard to put it back in... 

PP thoughts only, not a mechanic...

Best regards,

-a-

[carusoam]

Following eliman’s link above...

there is a pirep that may be believable...

Notice how much detail is used to explain what is being done... Know how many amps you need... stay within the limits...

only turn on the things you want powered up... pull circuit breakers or turn switches off if needed...

Best regards,

-a-

 

Just got this 2 weeks ago and it worked as advertised in my Cessna Caravan G1000. My G1000 draws 16 amps when both PFD and MFD are turned on so the 20 amp capacity is adequate. A lot easier than hauling out the very heavy GPU on wheels to the plane.

[Derek]

Thanks @carusoam. This has helped a lot.

 

[GeeBee]

22 hours ago, elimansour said:

I think this one will work better (since I believe that you are not supposed to charge through the GPU port): https://www.aircraftspruce.com/catalog/elpages/portPowerCharger24ces.php?clickkey=6344

I bought it and use it regularly to run the avionics on the ground.

I bought the same unit and I love it. It is more than enough power to run the G1000 and it is an intelligent charger. It comes with clips as well as a plug so I can charge the #2 battery if it needs it. Overall better value for the money unless you need starting capability.

 

[Danb]

I also have had this unit no issues it’s now 13 years old, when I haven’t  flown for a couple weeks I plug it in overnight and it always keeps my batteries strong. When avionics are used on ground I also never had any issues 

[EricJ]

33 minutes ago, Hyett6420 said:

A quick question i have never understood.  I assume if you are using a GPU to start your engine, if the battery is a little flat, that you plug the gpu device in. Turn on the master and crank?  This is on a J.  

Sorry for ever so slight thread creep.  

No, these GPUs generally don't produce enough current for starting.    They should be used for ground avionics power, etc., and constant-voltage charging only.

There are a few exceptions of units that can support starting, but starting requires a LOT of current.    If you need to jump it to start it, use either another fully charged battery or a battery cart.

 

[jaylw314]

1 hour ago, Hyett6420 said:

A quick question i have never understood.  I assume if you are using a GPU to start your engine, if the battery is a little flat, that you plug the gpu device in. Turn on the master and crank?  This is on a J.  

Sorry for ever so slight thread creep.  

A GPU or any constant current charger should be able to charge your battery enough to crank the motor in 5-10 minutes.  Heck, I recall a YouTube video I can't find anymore of someone just using 12 AA batteries to recharge their car battery enough to crank the motor after 15 minutes or so.

You're not supposed to run your alternator with a battery that's dead, so if your battery is so dead that a GPU can't charge it enough to crank within 15 minutes, it might not be a good idea anyway...

[KB4]

On 10/30/2019 at 10:49 AM, elimansour said:

I think this one will work better (since I believe that you are not supposed to charge through the GPU port): https://www.aircraftspruce.com/catalog/elpages/portPowerCharger24ces.php?clickkey=6344

I bought it and use it regularly to run the avionics on the ground.

The one above didn't work for me had to return it.  Guess depends on day of week was made at factory. 

Get 1 that doesn't charge battery only provides power supply.  I used this and it works fine. https://www.aircraftspruce.com/catalog/elpages/bycanps1450ae.php

 

[EricJ]

Tricky finding 50Hz power in the US, tho...