GPU vs. Battery Charger

Corefile

Corefile

Active Member
Joined
Nov 18, 2019
Messages
123
When you are updating your Skyview, or doing any other maintenance or testing of your avionics that you want to make sure you don’t drain your battery. Do you use a ground power unit (not cheap) or do you put a battery charger on your battery. Basically can I get away with using a battery charger on my battery and put the money into fuel instead of a gpu?
 
Last edited:
Yes, you can. Don't use a high amperage setting on a car charger designed to start cars with dead batteries. Use a lower amperage setting. You can use a trickle charger too. Your avionics will actually run off the battery, but a trickle charger should keep the battery from getting too low, unless you're running a whole lot of stuff. Make sure whatever charger you use is compatible with whatever aircraft battery you might have. Some battery manufacturers are picky about what kind of charger you use. Some pilots keep a spare automotive battery in their hangar that they keep charged for just such occasions.
 
Some of the more sophisticated battery chargers have built in power supply modes. The NOCO Genius charger I use has modes to charge traditional 12 volt wet cell, gel cell, AGM, an even Lithium batteries. It also has a power supply mode that provides 13.6 volts @ 5 amps, which is plenty for doing data base updates and practicing avionics buttonology in the hangar. It is just a simple constant 13.6 volts instead of whatever varying voltage profiles programmers chose to charge the various battery chemistries. Likely most similar smart battery chargers cost a lot less than a plug in GPU.

Ken
 
That sounds like a decent option. Personally, I'd try to stay at 10 amps or less if possible, and most NOCOs fit that bill. I use a Battery Tender trickle (float) charger, which generally costs less, but it doesn't have the full power supply mode that CanardMulti mentions. The cheapest NOCO model doesn't have that either. It's just a trickle charger. But like I said, a trickle charger works fine for me, as long as it's compatible with the battery.
 
I recommend you never run electronics on any battery charger. Use a real regulated power supply for your hangar flying (and it will charge you battery(s) at the same time).

This is is a nice, compact 30 amp unit with adjustable output voltage. It will run your plane just like your alternator. A year ago you could get it for $99…..
www.dxengineering.com

MFJ MFJ-4230MV MFJ 4230MV MightyLite 30 Amp Switching Power Supplies | DX Engineering

Free Shipping - MFJ 4230MV MightyLite 30 Amp Switching Power Supplies with qualifying orders of $99. Shop Power Supplies at DX Engineering.
www.dxengineering.com www.dxengineering.com

Carl
 
Rhino said:
That sounds like a decent option. Personally, I'd try to stay at 10 amps or less if possible, and most NOCOs fit that bill. I use a Battery Tender trickle (float) charger, which generally costs less, but it doesn't have the full power supply mode that CanardMulti mentions. The cheapest NOCO model doesn't have that either. It's just a trickle charger. But like I said, a trickle charger works fine for me, as long as it's compatible with the battery.
Click to expand...
I have a batteryminder trickle charger, it has a max output of 8 amps. It’s the model that is specific for my battery (Odyssey SBS-J16) - I even installed their quick connect kit.
www.batteryminders.com

BatteryMINDer® Model 128CEC2-AA-S3: 12V 8 AMP HAWKER-ODYSSEY® Aviation Battery Charger-Maintainer-Desulfator

BatteryMINDers' desulfating battery charger maintainers fully charge without ever overcharging, no matter how long they are left connected. Visit our website to browse our available products.
www.batteryminders.com www.batteryminders.com
 
That model apparently doesn't have a full power mode (they don't publish the specs), but it should work. If the battery drains too fast with it, you could consider getting something better. You won't know until you try. I have several switching power supplies like the one Carl mentioned, and they're great equipment. But I never hook them to an aircraft because, as I said earler, I don't personally use high power stuff over 10 watts for continually powering all avionics in an aircraft. That particular model is designed to produce power for high wattage ham radios, which is more than you'd typically need for a small plane. I'm not aware of any official warnings prohibiting their use on installed avionics in aircraft. It's just a personal preference. I have used them on the bench though, where the potential for electrons flowing somewhere I didn't intend is much lower. Your mileage may vary.
 
The output capacity of the power supply has nothing to do with use - other than you want one big enough to handle the loads you are putting on it.

What I do:
- Connect the power supply to the battery buss.
- Turn down the power supply output voltage to ~12vdc (typically there is a detent around 13.8vdc). This means when the power supply is turned on it will be below battery voltage - so it will not provide any current.
- Turn on the power supply. Increase voltage watching current come up as it picks up load. At 10 amps or so (in my plane) it has all the avionics load. As you increase the voltage to normal alternator output voltage (14.1-14.2vdc) current exceeding the base load (for me 10 amps) is going to charge the battery. This is a very good way to verify the health of your battery(s). As the battery(s) charge comes up, you can monitor the power supply current coming down. When it gets down to just your avionics load you know the battery(s) are fully charged.

Again, never run electronics with a battery charger connected to your battery (this is also specifically prohibited in the pMag install manual). Your battery is a DC animal, any AC trash coming out of your battery charger will ride on top of the DC voltage. I know some high end battery chargers are better than others, but a simple power supply does everything you need.

Side note. I run two PC-625 batteries in all three of my RV builds. Over 20 years none have ever been connected to a trickle charger, battery tender, battery minder, etc. I replace one battery every three years (so neither is more than six years old) to have confidence in my battery reserve. The pulled batteries go on to a second life in the neighbors’ John Deer or lawn tractors.

Carl
 
Carl_Froehlich said:
The output capacity of the power supply has nothing to do with use - other than you want one big enough to handle the loads you are putting on it.
Click to expand...
I guess that should explain that better. Yes, the capacity is tied to use. And under normal operations, it will only use what it needs to. But after 20 years working avionics in the Air Force, I learned the hard way that the entire capacity of a power supply will instantaneously be used if you get an accidental short somewhere. Damage from such an event is far easier to fix on a bench than in an aircraft. Now admittedly, such an event is very rare, but it does happen. Amateur builders wiring their own unique aircraft, with equipment and system architectures they are often utilizing for the first time in their lives, tend to increase the possibility of such events. Using a lower capacity doesn't eliminate the possibility of damage either, but I like to take what steps I can to hopefully reduce that possibility, and using a lower capacity power supply is an easy and inexpensive way to do that. You can also get spurious signals from a power supply just as you can from a charger. But all else being equal, I'd prefer a power supply as well, because, as you indicated, those chances are lower. Again, as I said before, this is a personal choice I make for myself, and I offer it only for consideration. I wasn't attempting to offer it as an argument. You and any other builder are free to do whatever you want to do, and free to completely disregard what I said if you want.
 
Reading the installation manual on using the Dynon screens during aircraft construction it states that a battery charger should be connected to the battery and states what amperage you will require. Page 9-4 and 9-5.
 
Carl_Froehlich said:
I recommend you never run electronics on any battery charger. Use a real regulated power supply for your hangar flying (and it will charge you battery(s) at the same time).

This is is a nice, compact 30 amp unit with adjustable output voltage. It will run your plane just like your alternator. A year ago you could get it for $99…..
www.dxengineering.com

MFJ MFJ-4230MV MFJ 4230MV MightyLite 30 Amp Switching Power Supplies | DX Engineering

Free Shipping - MFJ 4230MV MightyLite 30 Amp Switching Power Supplies with qualifying orders of $99. Shop Power Supplies at DX Engineering.
www.dxengineering.com www.dxengineering.com

Carl
Click to expand...
Agree 100%. A real regulated power supply is best.

FWIW; you are better off running on your airplane battery for updates than using most battery "chargers" or "maintainers". Most of these have poor AC ripple filtering which can damage non MilSpec avionics. You can always recharge the battery once your avionics are not connected.
 
Dynon equipment is well protected from stray voltage variations, by the way. Other stuff....... it depends.
 
I have been using a US made Genius charger when working on my screens on the ground- works fine.
On another subject I have problems with a resistive fuel gauge sender. Was surprised to find severe corrosion on the Vans supplied unit in the right wing. This after only 4 hours flight testing in my newly finished RV9.I seem to have messed up swapping the wiring R to L on the EMS pins20 & 21. Now I can't get the new sender to connect with the EMS. I get error message "position source 1 fail " I can't find that in the installation manual-Any offers to explain would be welcome
 
Carl_Froehlich said:
I recommend you never run electronics on any battery charger. Use a real regulated power supply for your hangar flying (and it will charge you battery(s) at the same time).

This is is a nice, compact 30 amp unit with adjustable output voltage. It will run your plane just like your alternator. A year ago you could get it for $99…..
www.dxengineering.com

MFJ MFJ-4230MV MFJ 4230MV MightyLite 30 Amp Switching Power Supplies | DX Engineering

Free Shipping - MFJ 4230MV MightyLite 30 Amp Switching Power Supplies with qualifying orders of $99. Shop Power Supplies at DX Engineering.
www.dxengineering.com www.dxengineering.com

Carl
Click to expand...
I was getting ready to post a couple of links about this. Looks like you beat me to it.

Battery, and voltage regulator work together to provide nice DC conditioning for your avionics bus during normal operation. Make sure you've got equal quality of DC when using bench power!
 
If you don't need the variable voltage adjust or metering, these 2 items together would be almost half the cost of the MFJ unit:


Note the power supply's output is 13.8V DC, is regulated with a 30 amp capacity, an internal cooling fan and is short-circuit protected.

I have used this power supply for a couple of years now and it works well. I monitor the voltage and current feeding the avionics power buss using the plane's volt and ammeter.
 
andresmith76 said:
If you don't need the variable voltage adjust or metering, these 2 items together would be almost half the cost of the MFJ unit:


Note the power supply's output is 13.8V DC, is regulated with a 30 amp capacity, an internal cooling fan and is short-circuit protected.

I have used this power supply for a couple of years now and it works well. I monitor the voltage and current feeding the avionics power buss using the plane's volt and ammeter.
Click to expand...

That's great!

Have you ever looked for AC in the output when that powersupply loads up? A couple of displays turned on with backup batteries charging ought to give it enough of a work out to put a Fluke with a couple of decent quality leads across the output just to look for any ripple. Its not an accurate test. For that you'd need a properly set up O-scope. But, it'd be interesting just to see.
 
wilkersk said:
That's great!

Have you ever looked for AC in the output when that powersupply loads up? A couple of displays turned on with backup batteries charging ought to give it enough of a work out to put a Fluke with a couple of decent quality leads across the output just to look for any ripple. Its not an accurate test. For that you'd need a properly set up O-scope. But, it'd be interesting just to see.
Click to expand...
I haven't measured the AC ripple on this unit's output. I've attached the owner's manual - on the last page it's states 150 mv RMS. The next time I'm at the hangar, I'll do some measuring. I keep my plane's battery on a trickle charger, so I won't be able to measure while drawing close to the max rated current. But with all avionics, lights and electrical systems on, I can get a good idea with a moderate load.
 

Attachments

andresmith76 said:
I haven't measured the AC ripple on this unit's output. I've attached the owner's manual - on the last page it's states 150 mv RMS. The next time I'm at the hangar, I'll do some measuring. I keep my plane's battery on a trickle charger, so I won't be able to measure while drawing close to the max rated current. But with all avionics, lights and electrical systems on, I can get a good idea with a moderate load.
Click to expand...

If I'm not mistaken, the MFJ 4230 has less than 50mV(RMS). The manufacturer's claim is less than 100mV(Peak-to-Peak), so that's approximate.

But, that's pretty much the reason why I like just using a motorcycle battery for bench checking my avionics install. I just put the battery on a charger when I'm done. Don't have to worry about ripple.
 
I understand and can appreciate your perspective. I'm not too concerned with either 100 or even 200mv AC on top of 13.8V DC powering my plane's electrical system. I find doing so while the plane in the hangar is a great way to play, learn and update the avionics without running the battery down before flying.
 
I'd be interested in analyzing what's on the charger line in comparison to the onboard systems. Aircraft electrical systems are notorious for noise and power fluctuations from stuff like alternators, servos, strobes, lights and equipment going on and off, landing gears, etc. It would be interesting to see how that onboard bus signal compares to one from a modern smart charger. Unfortunately, watching an oscilloscope inflight would probably detract from things like, oh, flying the plane. I suspect the output from the charger wouldn't be any noisier or dirtier than aircraft power itself. That's why Dynon systems have such robust protection built in for that kind of stuff. I imagine all modern avionics do. How would they survive otherwise? Plus, you could also add a shunt capacitor to the output of the charger if such a concern is that worrisome. 50 microfarads or so should do a decent job.
 
Last edited:
You must log in or register to reply here.
Back
Top