Ground Power

My partners and I are considering building a small, external battery unit (EPU) to supply battery power to our soon-to-be-born SR22. The idea is to put together 2 12v small car batteries in series with an attached battery charger, contained in a vented, wheeleable container. This would be prewired so as to avoided any confusion about attaching cables to the EPU. Aircraft Spruce and Specialty has a plug for $35 which should fit a standard aircraft external connection (correct me if I’m wrong).

I know there are electrical guru’s out there and would appreciate any advice on such a system.

I understand that electrical consumption while “tinkering” with avionics etc., not to mention an EPU engine start, is high and that battery capacity is limited. We are basing at a new (can you believe it!) uncontrolled airport outside RDU that has limited capability to provide a jump if needed.

Chris N122CG

We are basing at a new (can you believe it!) uncontrolled airport outside RDU that has limited capability to provide a jump if needed.

Chris N122CG

Would this be the Sanford-Lee Airport?

I know there are electrical guru’s out there and would appreciate any advice on such a system.

The guru you want to talk to is Mike - aka N84MR - mikerad@nerc.com, as I am almost sure he put together a ground power system that is exactly what you’re looking for. There were some gotchas as I recall that he had discovered and solved. I think he even posted his solution on his web site but I can’t find the URL

Gordon

My partners and I are considering building a small, external battery unit (EPU) to supply battery power to our soon-to-be-born SR22. The idea is to put together 2 12v small car batteries in series with an attached battery charger, contained in a vented, wheeleable container. This would be prewired so as to avoided any confusion about attaching cables to the EPU. Aircraft Spruce and Specialty has a plug for $35 which should fit a standard aircraft external connection (correct me if I’m wrong).

I know there are electrical guru’s out there and would appreciate any advice on such a system.

I understand that electrical consumption while “tinkering” with avionics etc., not to mention an EPU engine start, is high and that battery capacity is limited. We are basing at a new (can you believe it!) uncontrolled airport outside RDU that has limited capability to provide a jump if needed.

Chris N122CG

Chris,

I purchased two jump start units from SAM’s Club. They are normally used to jump start a car but they have chargers build into them so that you can plug them in to charge when they are not being used.

They have batteries built into them and you will wire them in series using the cables that are normally used to jump start the car. You will cut one cable and put a ring terminal on the end and attach it to the other unit.

You will also use the plug that you referred to above.

This assembley works out for me better because they are smaller than seperate batteries and they have the chargers built in.

If you want more details or a picture let me know and I will send it to you.

Mark Jeffries

We are basing at a new (can you believe it!) uncontrolled airport outside RDU that has limited capability to provide a jump if needed.

Chris N122CG

Would this be the Sanford-Lee Airport?

Actually, you might be refering to the new Lee County Regional Airport. Sanford-Lee was closed.

For a battery charger I suggest a Guest marine charger. Guest has waterproof 24v chargers and they are 3 stage. I own a 12 volt portable waterproof charger and use it to charge my car batteries (10A) as well as leave it on my convertable all winter to keep the battery full. Since it’s a three stage charger it will give you a full recharge (overcharge mode) and then drop down to a float charge (that won’t boil away the battery)

They work on both SLA and wet.

-Eric

http://www.guestco.com/Chargepro/waterproof.html

For a battery charger I suggest a Guest marine charger. Guest has waterproof 24v chargers and they are 3 stage. I own a 12 volt portable waterproof charger and use it to charge my car batteries (10A) as well as leave it on my convertable all winter to keep the battery full. Since it’s a three stage charger it will give you a full recharge (overcharge mode) and then drop down to a float charge (that won’t boil away the battery)

They work on both SLA and wet.

-Eric

http://www.guestco.com/Chargepro/waterproof.html

For the absolute comfort get the Razor scooter, which has a 24 volt battery with a charger. Scoot out to your plane, add a plane connector and have the best mobile GPU.

For a battery charger I suggest a Guest marine charger. Guest has waterproof 24v chargers and they are 3 stage. I own a 12 volt portable waterproof charger and use it to charge my car batteries (10A) as well as leave it on my convertable all winter to keep the battery full. Since it’s a three stage charger it will give you a full recharge (overcharge mode) and then drop down to a float charge (that won’t boil away the battery)

They work on both SLA and wet.

-Eric

http://www.guestco.com/Chargepro/waterproof.html

For the absolute comfort get the Razor scooter, which has a 24 volt battery with a charger. Scoot out to your plane, add a plane connector and have the best mobile GPU.

Hey Mike, but will it tow a 3000lb Cirrus?!

Chris N122CG

I know there are electrical guru’s out there and would appreciate any advice on such a system.

The guru you want to talk to is Mike - aka N84MR - mikerad@nerc.com, as I am almost sure he put together a ground power system that is exactly what you’re looking for. There were some gotchas as I recall that he had discovered and solved. I think he even posted his solution on his web site but I can’t find the URL

Gordon

Hey, thanks for the tips. Hopefully, this should be an easy project

Chris

For the budgeted minded person:

Go to a Maintenance facility, one that works on Turbo-props or jets, bring a large combo pizza.

Ask to speak to the guy in charge and tell him you would like to swap the box on your hand for a 24 volt battery.

Then buy a 24 volt batter charger for about $60 bucks. Now you have a perfectly good 24 volts GPU.

Hint: The bigger airplanes get their new battery even if they don’t need one, just because it is important enough for it never to go bad before you replace it. I am still using mine that I removed from a Cheyenne two years ago, and it works like a new one. Much easier and safer to have the right (24V) equipment. Some things is better to spend a little more and go first class. Have a great Cirrus safe day.

Woor

I know there are electrical guru’s out there and would appreciate any advice on such a system.

The guru you want to talk to is Mike - aka N84MR - mikerad@nerc.com, as I am almost sure he put together a ground power system that is exactly what you’re looking for. There were some gotchas as I recall that he had discovered and solved. I think he even posted his solution on his web site but I can’t find the URL

Gordon

Hey, thanks for the tips. Hopefully, this should be an easy project

Chris

For the budgeted minded person:

Go to a Maintenance facility, one that works on Turbo-props or jets, bring a large combo pizza.

Ask to speak to the guy in charge and tell him you would like to swap the box on your hand for a 24 volt battery.

Then buy a 24 volt batter charger for about $60 bucks. Now you have a perfectly good 24 volts GPU.

Hint: The bigger airplanes get their new battery even if they don’t need one, just because it is important enough for it never to go bad before you replace it. I am still using mine that I removed from a Cheyenne two years ago, and it works like a new one. Much easier and safer to have the right (24V) equipment. Some things is better to spend a little more and go first class. Have a great Cirrus safe day.

Woor

I like your idea. Where can you find a 24v charger for $60. I believe new 24v batteries go for over $200. Expensive little suckers!

Could you use a 12v charger to charge 2 12v old car batteries connected in series to produce 24v?

Chris

I know there are electrical guru’s out there and would appreciate any advice on such a system.

The guru you want to talk to is Mike - aka N84MR - mikerad@nerc.com, as I am almost sure he put together a ground power system that is exactly what you’re looking for. There were some gotchas as I recall that he had discovered and solved. I think he even posted his solution on his web site but I can’t find the URL

Gordon

Hey, thanks for the tips. Hopefully, this should be an easy project

Chris

I like your idea. Where can you find a 24v charger for $60. I believe new 24v batteries go for over $200. Expensive little suckers!
Could you use a 12v charger to charge 2 12v old car batteries connected in series to produce 24v?
Chris
Chris,
Just jumping in here… no, a 12v charger can’t be used to charge 2 12v batteries that are connected in series - that’s electrically untenable. However, you could (maybe) charge the 2 batteries if they were in parallel; not recommended, though, unless it’s a pretty dumb charger (one that doesn’t try to “know” how close to fully charged it’s battery is, and adjust the charging current accordingly).
It would certainly be fine to use a 12v charger to charge two batteries one at a time. Whichever way you charge the two 12v batteries, they WILL have to be in series when you use them for the airplane.
However, you asked…
Could you use a 12v charger to charge 2 12v old car batteries connected in series to produce 24v?
Of course, that depends on how old!

Bottom line - the best solution is a 24v charger charging a 24v battery, or at worst 2 12v batteries connected in series; other solutions might work, but you’d be less than satisfied.

  • Mike.

I guess I need to start selling them. How many do you want for $109.00?

Cheers,

Woor

For the budgeted minded person:

Go to a Maintenance facility, one that works on Turbo-props or jets, bring a large combo pizza.

Ask to speak to the guy in charge and tell him you would like to swap the box on your hand for a 24 volt battery.

Then buy a 24 volt batter charger for about $60 bucks. Now you have a perfectly good 24 volts GPU.

Hint: The bigger airplanes get their new battery even if they don’t need one, just because it is important enough for it never to go bad before you replace it. I am still using mine that I removed from a Cheyenne two years ago, and it works like a new one. Much easier and safer to have the right (24V) equipment. Some things is better to spend a little more and go first class. Have a great Cirrus safe day.

Woor

I like your idea. Where can you find a 24v charger for $60. I believe new 24v batteries go for over $200. Expensive little suckers!

Could you use a 12v charger to charge 2 12v old car batteries connected in series to produce 24v?

Chris

I know there are electrical guru’s out there and would appreciate any advice on such a system.

The guru you want to talk to is Mike - aka N84MR - mikerad@nerc.com, as I am almost sure he put together a ground power system that is exactly what you’re looking for. There were some gotchas as I recall that he had discovered and solved. I think he even posted his solution on his web site but I can’t find the URL

Gordon

Hey, thanks for the tips. Hopefully, this should be an easy project

Chris

I like your idea. Where can you find a 24v charger for $60. I believe new 24v batteries go for over $200. Expensive little suckers!
Could you use a 12v charger to charge 2 12v old car batteries connected in series to produce 24v?

Chris

Chris,

Just jumping in here… no, a 12v charger can’t be used to charge 2 12v batteries that are connected in series - that’s electrically untenable. However, you could (maybe) charge the 2 batteries if they were in parallel; not recommended, though, unless it’s a pretty dumb charger (one that doesn’t try to “know” how close to fully charged it’s battery is, and adjust the charging current accordingly).

It would certainly be fine to use a 12v charger to charge two batteries one at a time. Whichever way you charge the two 12v batteries, they WILL have to be in series when you use them for the airplane.

However, you asked…

Could you use a 12v charger to charge 2 12v old car batteries connected in series to produce 24v?

Of course, that depends on how old!

Bottom line - the best solution is a 24v charger charging a 24v battery, or at worst 2 12v batteries connected in series; other solutions might work, but you’d be less than satisfied.

  • Mike.

Well, since the batteries were inexpensive and my gismo built, I’ll pound these keys and search the net for an inexpensive 24v charger. Thanks

Chris N122CG

Well, since the batteries were inexpensive and my gismo built, I’ll pound these keys and search the net for an inexpensive 24v charger. Thanks

Chris N122CG

Chris: Look at Aircraft Spruce & Specialty Company. They list their part number EPS-2404 24 volt 4 amp. at $71 and their part number EPS-2407 24 volt 7 amp. at $98.75. Both are described as automatic chargers made in Australia for “harsh conditions”. They appear to be appropriate to mount on a flat surface. I would attach it to a wheeled cart or hand truck above the battery.

If anyone knows of a source for a wheeled cart to hold the battery, charger and cables like are seen in auto repair shops, I would appreciate seeing any sources for this item.

Well, since the batteries were inexpensive and my gismo built, I’ll pound these keys and search the net for an inexpensive 24v charger. Thanks

Chris N122CG

Chris: Look at Aircraft Spruce & Specialty Company. They list their part number EPS-2404 24 volt 4 amp. at $71 and their part number EPS-2407 24 volt 7 amp. at $98.75. Both are described as automatic chargers made in Australia for “harsh conditions”. They appear to be appropriate to mount on a flat surface. I would attach it to a wheeled cart or hand truck above the battery.

If anyone knows of a source for a wheeled cart to hold the battery, charger and cables like are seen in auto repair shops, I would appreciate seeing any sources for this item.

Stephen,

I just ordered the charger from Aircraft Spruce & Specialty. Thanks! Misson completed. This forum is fantastic and is much easier to use than ASK JEEVES.

BTW, American Flyer makes a great little red wagon for your battery cart :slight_smile: Found one at a yard sale…very high tech!
Now if I could just figure out how to make a power tow…

Chris N122CG

how about purchasing 1 ‘24’ volt battery, the cable and plug you mentioned and let it rip. Put the seperate charger on an electrical plug-in timer and set it to charge 1 hour each day. Or, buy a charger with ‘auto on//off’. all this was about $200.

don

My partners and I are considering building a small, external battery unit (EPU) to supply battery power to our soon-to-be-born SR22. The idea is to put together 2 12v small car batteries in series with an attached battery charger, contained in a vented, wheeleable container. This would be prewired so as to avoided any confusion about attaching cables to the EPU. Aircraft Spruce and Specialty has a plug for $35 which should fit a standard aircraft external connection (correct me if I’m wrong).

I know there are electrical guru’s out there and would appreciate any advice on such a system.

I understand that electrical consumption while “tinkering” with avionics etc., not to mention an EPU engine start, is high and that battery capacity is limited. We are basing at a new (can you believe it!) uncontrolled airport outside RDU that has limited capability to provide a jump if needed.

Chris N122CG

Chris,

I purchased two jump start units from SAM’s Club. They are normally used to jump start a car but they have chargers build into them so that you can plug them in to charge when they are not being used.

They have batteries built into them and you will wire them in series using the cables that are normally used to jump start the car. You will cut one cable and put a ring terminal on the end and attach it to the other unit.

You will also use the plug that you referred to above.

This assembley works out for me better because they are smaller than seperate batteries and they have the chargers built in.

If you want more details or a picture let me know and I will send it to you.

Mark Jeffries