Battery behind firewall attachment

I want to put my battery (for instance Odyssey PC680 planned) in the originally foreseen location by Vans, i.e. behind the firewall, between the rudder pedals. For those who have that location for the battery: how have you attached the battery? Have you reinforced the floor, if the battery sits on it? The plans are not very specific on this.

I think that's a good place to put it and a good battery choice. That battery used to come in a steel box. What I did was, separate the battery from the box, mount the box to the side of the floor web and the floor.Then the battery would slide down into place. I made a little bracket to hold it down. It's hard to work in that space but it worked well for me.

Clouddancer said:

I want to put my battery (for instance Odyssey PC680 planned) in the originally foreseen location by Vans, i.e. behind the firewall, between the rudder pedals. For those who have that location for the battery: how have you attached the battery? Have you reinforced the floor, if the battery sits on it? The plans are not very specific on this.

Click to expand...

I'm not where I can check right now but my plans did show a holddown made from AL 'U-channel' on top of the battery and clip nuts on a shallow AL angle box on the fuse floor. The battery fit in the box and loooong bolts through the U-channel clamped it down by the clip nuts. I'll get a drawing number and maybe a photo of that part of the drawings in a few days.

Other than the additional stiffening provided by the AL box riveted to the floor there was no additional reinforcing.

Not much difference in CG by mounting the battery just behind the firewall vs. just in front of the firewall. Much easier wiring and safer to mount on the firewall in the engine compartment. Much more difficult to service the battery behind the firewall.

That is, unless you are replacing a battery already installed behind the firewall.....

Is this a new installation? What is your reasoning for mounting behind the firewall? Curiosity strikes again!!

Thanks for the replies!

Nauga, I would especially be interested in the box on the floor. I am just a bit concerned by just putting the battery weight on the floor without any other support.

PCHunt, it's a new installation. The previous builder has foreseen to put it there and has already made a forward attachment bracket to srew a bolt in and then stopped... But the main reason is, that the space forward of the firewall is pretty much stuffed by the Christen inverted oil system and it's hoses, heater valve, oil pressure & fuel pressure and flow sensor. Otherwise the decision on the location may have been different

My experience

I have my battery "per plans" in the tunnel between my feet. The plans install 4 angles riveted through the lower skin to hold the battery in place, and utilize a simple aluminum hold down. Its a good location, but a pain to get to. I also have a console installed from the instrument panel to the tunnel,in which my transponder and glovebox are in, along with the tunnel close-out, so the battery is really covered up. To get to my battery it takes removing the forward skin panel, pulling my transponder and removing the cover plate...not easy!. I did at least wire it with a battery tender plug that is inside my oil door in case I need to charge it. I am likely going to move mine on the fwd side of the firewall in the near future. If I didn't have the console, it wouldn't be as significant an issue, but its just not very easy to get to.

battery forward of firewall

Put my battery (the smaller Odessey 545) on the front of the fire wall. I can't twist into Gumby shapes that easy to access the proposed Van's location so the Van's location was not a choice. During different tweaks of my 4, I have disconnected the battery probably 8 or 9 times. I think ease of disconnection is big consideration.
You don't have a lot of room to play with on the firewall in a 4 (an understatement) so that is a negative for the forward firewall location. You might ask if I have ever had a problem starting with the smaller Odessey. Not at all even in winter. The Odessey charger plug is located near the Oil door for easy access and works well.
I am also installing a Piper external power receptacle under the panel and carry a set of Piper jumpers on long trips. There is an after market moounting bracket for the smaller Odessey that is well made and reasonably priced.

I moved my battery

I built my -4 with the original battery in the original location. As others have said, its a pain to get to.

So, along with some other moves to lighten the plane, I moved the odyssey into the right cheek. I made a battery box out of aluminum, and attache it to the engine mounts with adel clamps. Now I use the old battery location for forward baggage. It really helps with the CG on cross country flights with baggage and a passenger, so if you can swing it, I would put it up front.

battery in cowl cheek

Battery in cowl cheek is an innovative solution, if the firewall is already too crowded. N999BT, would you have a picture of your installation?

I see that the original location in the tunnel is difficult to access. If I have to go with that solution, I will have to pay attention to facilitate access as much as possible, altough I have a console down from the panel to the tunnel. A battery tender plug is planned.

in my -6A I have had the battery in it's original position, between the pedals, and then later moved it to the engine compartment. it is now back inside and will remain there. the original plans, circa 1997, had you build an AL box fastened down with piano hinge. I modified it to allow me to also hinge open the top corner of this box to give me easy access to the positive battery terminal. jumping a battery inside the cowl is hard and messy and dangerous. I added a chunk of foam as a spacer when I went to the half battery. the negative terminal has a brass "L" that bolts to a firewall ground stud and holds the battery secure inside the box. the space gained by moving the battery to the engine compartment is totally unused otherwise. similarly the center space between the battery and the spar is best used to hold maps, lunch, etc... because your feet never go there anyway.
on the same line I have had the throttle/mixture/carb heat cables on a vertical channel as originally designed by Van, and then changed it to an under panel mount that everyone seemed to be going to. after installing a center arm rest I moved all the cables back to the original design which allow the throttle to be the exact elevation to my hand resting on the arm rest [I fly with my left hand on the stick]. all my cables are run thru this channel. despite designing it to be easily removed for maintenance, I've discovered that it doesn't get in the way as one would have guessed. so, Van wins again!

Clouddancer said:

Battery in cowl cheek is an innovative solution, if the firewall is already too crowded. N999BT, would you have a picture of your installation?
.

Click to expand...

+1 I'd love to see that installation. It would be a fabulous use of the unused space. What would the impact of acro G's be on that installation?

I've got a Concorde RG25 in the tunnel. It would never fit FWF, and when I ran the W&B with a lighter /smaller PC680 on the firewall the CG moved forward approximately 0.1". It's a pain to service, but I prefer that to having to rework the battery mount and wiring, so I'm staying with the Concorde in the tunnel.

I built as per plans with the Odyssey 680 between the rudder pedals. I have a radio and transponder above the battery, mounted to a frame of angle on the left side with a piano hinga and supported on the right from an angle between firewall and panel. To remove the battery, I just unlatch the raio and transponder and flip them up to about 60 deg angle and can get at the battery terminals and starter solenoid. the fuel pump is lower down on the left and difficult to get at.

I have my pc680 just forward of the spar. Sits on a uhmw pad above the floor and held down by a simple bracket. Covered by the stick boot cover. Helps move the cg aft for O360 constant speed RV-4. Its a tight fit but works.

http://www.aircraftspruce.com/catalog/elpages/odysseydry9.php?clickkey=119690

This battery bracket for the Odyssey P680 is pretty nice. I'm in the process of mounting this in the RV-4 tunnel between the rudder panels. This will still allow some space for storage/food/maintenance gear etc.

I would love to mount firewall forward but it looks nearly impossible with the Air-Oil Separator on the firewall.

Clouddancer said:

Battery in cowl cheek is an innovative solution, if the firewall is already too crowded. N999BT, would you have a picture of your installation?

I see that the original location in the tunnel is difficult to access. If I have to go with that solution, I will have to pay attention to facilitate access as much as possible, altough I have a console down from the panel to the tunnel. A battery tender plug is planned.

Click to expand...

I have looked for a picture and don't seem to have one. I will take a picture next time the cowl is off and post to this thread. Essentially I built the box out of aluminum, 0.032 if I remember correctly. I used 4 adel clamps to clamp the battery box to the two engine mount struts just behind the oil dip stick. It is pretty convenient because the positive terminal is right at the back end of the oil door, so you can charge the battery using any charger or even jumper cables from a car. I used a 3/4 x 3/4 x 0.063 angle for the hold down on top, and used AN3 bolts to hold that down. I do aerobatics, but I limit myself to about 4 g's, and it has held up well.

The only downside is that it is difficult to get to the mag, especially if you use one of the ports on the mag to hook up a sensor for your razu flat panel. You will have to take out the battery box to get to it.

Pictures of Batter Box in Cheek

I was able to take some pictures of my box that I installed in the cheek. Here is a side view:


View from side showing construction. Box is from 0.032. I used a 3/4 x 3/4 x 1/16 angle for battery hold down. There is a nylon strap that I wrapped around the battery to give me something to hang on to when time to remove.



View from above:



Top view. Note that there is a flange on the back side that is immediately underneath the engine mount tube. The adel clamp on the right is one of the clamps that supports the box:



View from front looking up. Note two adel clamps holding box.



Back side. Sorry about the lighting. This view shows the location of the third adel clamp. The bolt for the clamp is down and to the right of the engine mount tube, so about a third of the way down the side of the box.

I have about 500 hours on this installation, no squawks.

Pictures of Batter Box in Cheek

I was able to take some pictures of my box that I installed in the cheek. Here is a side view:


View from side showing construction. Box is from 0.032. I used a 3/4 x 3/4 x 1/16 angle for battery hold down. There is a nylon strap that I wrapped around the battery to give me something to hang on to when time to remove.



View from above:



Top view. Note that there is a flange on the back side that is immediately underneath the engine mount tube. The adel clamp on the right is one of the clamps that supports the box:



View from front looking up. Note two adel clamps holding box.



Back side. Sorry about the lighting. This view shows the location of the third adel clamp. The bolt for the clamp is down and to the right of the engine mount tube, so about a third of the way down the side of the box.

I have about 500 hours on this installation, no squawks.

Thank you Brent for the detailed description and the pictures! In the meantime we decided to mount the battery in the original location in tunnel aft of the firewall - mostly because of the layout of our electrical system and space firewall forward: we have a inverted oil system as well that takes some space.

But I like your idea and might use some of it to attach some other equipment on the engine mount. On your pictures I see that you mounted some kind of heat shield or out-flowing air deflector in front of the lower firewall part. I thought about something similar. Would you have some details on that? How did you attach it? Do you have any experience about the difference it makes (airflow, temp behind engine baffles etc)?

Forward thinking....

Clouddancer said:

I want to put my battery (for instance Odyssey PC680 planned) in the originally foreseen location by Vans, i.e. behind the firewall, between the rudder pedals. For those who have that location for the battery: how have you attached the battery? Have you reinforced the floor, if the battery sits on it? The plans are not very specific on this.

Click to expand...

Andreas,
I flew my RV4 for nearly 1500 hours. The original Concorde (heavy) Aircraft battery was mounted per the plans in the center "tunnel". I used a 2" thick rubber pad between the battery and the .040 floor doubler and aluminum strap around the battery to the sides of the tunnel. After 500 hours I disliked this location due to poor access, difficulty in charging and removal. I began re-engineering several things for my 2000' Conditional Inspection/re-fit.

1. Forward firewall mounted Odyssey Battery.
2. Forward and rear additional baggage area.
3. Rear passenger foot-wells.

First, like you I discarded the standard aircraft battery in lieu of an Odyssey battery, a fairly new device when I originally did this in 2000. There are smaller, lighter Lithium batteries available now. Re-locating the battery helped two things, it moved my CG forward and shortened the electrical wires to my new Lexus starter, less resistance, weight and cost. I built a battery box for the Odyssey (now available from Vans) and attached it to right side of the "shelf" (rudder pedal well) and the firewall. The empty space between your legs formerly occupied by the battery could now be a forward baggage area, or "glove box". Install a forward hinge on the cover and voila': forward baggage!

My "Bandit's" flight qualities would now be delightful and I could carry my items up front yielding the entire rear baggage compartment to my wife. Charging, easier cold starting and utilizing jumper cables through the oil door were now a reality. Win win! FYI: I would reconsider the full Christen inverted system unless you plan extended negative G acro to save weight and complexity. I used an Ellison TBI and Air/Oil separator for many fun hours of "sportsman" aerobatics, the RV's forte'.

Here are photos of the completed installation. Good luck!
V/R
Smokey


Battery on "shelf"



Why put battery on firewall? One reason is the forward "baggage" area!

Baffle

Yes it is faster, the baffle was about 4 mph if I remember correctly. I've done some other stuff too, but like close off the cowl inlet holes about 20%. The engine cools fine, in fact most of the year it runs too cool.

I win most of the SARL races I enter, and the baffle was worth at least 3 knots. My plane flat out at 8500 feet will do 192 KT TAS. On a good day my race speeds are up around 224 mph, so the real number is probably greater than that.

Ditto what Smokey said. Shorter cables, forward baggage, CG moved forward. You can carry more in the back, everything is better.

Brent & Smokey

Thank you for your insights. The biggest driver for our layout was the inverted oil system, that eats up space firewall forward and adds complexity. I have to admit that. Whether it is worth the efforts? I don't know yet. I can probably tell in a few years. We just like the thought that the engine gets enough lubrication even with sustained negative g's. ..and we do that already with other aircrafts (aerobatic gliders, B?ckers etc.)

We have not planned to use a more modern battery than the PC680 yet. But this is still an option for the future, as it will be smaller and lighter.
We even consider to add a smaller glove box on top of the tunnel behind the firewall. But it should be removable rather quick bor battery maintenance.

We already have the rear seat footwells

Raven....

Clouddancer said:

Brent & Smokey

Thank you for your insights. The biggest driver for our layout was the inverted oil system, that eats up space firewall forward and adds complexity. I have to admit that. Whether it is worth the efforts? I don't know yet. I can probably tell in a few years. We just like the thought that the engine gets enough lubrication even with sustained negative g's. ..and we do that already with other aircrafts (aerobatic gliders, Bückers etc.)

We have not planned to use a more modern battery than the PC680 yet. But this is still an option for the future, as it will be smaller and lighter.
We even consider to add a smaller glove box on top of the tunnel behind the firewall. But it should be removable rather quick bor battery maintenance.

We already have the rear seat footwells

Click to expand...

Andreas;
UR welcome!
Consider the "Half" Raven inverted system. Similar to my M20 Air Oil Separator, smaller and less costly than a full Christen system and still very capable...
http://ronsrv7project.blogspot.com/2012/09/half-raven-hobbs-15160-hrs.html
V/R
Smokey

https://www.youtube.com/watch?v=LgrVhdZde5U
RVX Acro with M20