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Underseat Battey rack

gdafoe

FRIEND
Castle Well Airpark SE of Wickenburg AZ
It looks like there are two STC'd light weight under the front seat battery racks one form Dan's and one from Atlee Dodge. Which one is best or is there much difference except for the price? I think Dan's is like $375 w/o battey and Atlee's is like $150 w/o battery. Do they both use the same battey?

Also, somebody refered to a good place to buy the gel batteries at lower cost but now I can't seem to find the thread.

Anybody out there that can help I'd like to move my battery and loose some weight.
Gerald
 
Go to ebay.com and do a search for pc680 battery. Theres an outfit selling them for $69.00.
 
Differences

The Atlee Dodge bracket clamps in place, requiring no welding or removal of the seat base. Dan's STC removes the seat base and TIG welds a battery tray in place between the supports. I have a Dan's conversion and got it when it was first approved some years ago. Crash
 
WIflyer, that's a pretty good deal. They look to be a reasonablly safe place to deal with. Soooo, this morning I ordered one. $69 plus $10 shipping is not bad. I let you all know how long it takes to get here.

Gerald
 
Batteries

Gerald I purchased one from them and there service was very good. Happy Cubbing.

Si
 
pc680 battery

I have used pc680 and the gell cell in a "under the rear seat installation". I find I only get about 6-7 volts at the starter. Does everyone get that kind of drop ? Lightweight starter has trouble cranking engine during cold weather or when the engine has just been shut down. Seriously considering the original battery installation (too much weight) or hand propping. Any advice ?
 
Battery

My 4 year old underseat battery in the PA-18 cranks it over so fast you could taxi on the starter alone. Did you install #2 starter cable or go smaller? Some guys tried #4 and have a hard time cranking. My PA-14 has the same setup and cranks just as good. Crash
 
Cable

It was set up when I purchased the plane two years ago. I'll check the size tonight. Thanks for the feedback.
 
I'm curious.............I've never seen one of the under the seat batteries. This is under the front seat?? There's enough room with the master cylinders and parking brakes?? Also...........how do you run the cables (wires) with the floor boards in place.......I assume you run them up the side similar to the original, but how do you get it from under the seat to the side with the floor boards in place? Also........where do you bolt the ground cable........and last......how much weight does this save..........whops......one last question...........on the smaller battery you're installing......how does it compare to cranking power?? This looks and sounds like it might be a good mod. Thanks for the info
Brian
 
I have a XT16 battery under the front seat, # 4 wire, B&C starter. Starts no problem down to 20F with no preheat. Picture page 8 of super cub pics of install.
 
Voltage drop

I must be overlooking something. B&C starter sent back for inspection. They say it is good. All wire is #2. PC680 battery. 13.5 volts at battery. Still only get 7 volts at starter when cranking. Any ideas would be appreciated.
 
Hook one lead from an amp meter to the positive lead on the battery and one to the starter post. Hit the starter botton and see how many amps go thru the amp meter. Should be very little. The power should take the path of least resistance via the larger cable. The lead goes from the battery to the relay, thru the relay on to the starter. I would check all connections. Also, is the engine grounded to the engine mount. Your engine is hanging on rubber bushings and you should have a braided strap from the engine mount to the engine. I have seen engines without the ground strap work fine and others not. You need a ground path from the starter back to the battery.

Steve
 
Selenoid

One thing I have done in the past when setting up the selenoids is to run the battery (#2 size wire) hot lead to the starter selenoid post first then jump from it to the master seloniod with a short peice of #8 size wire. This eliminates the stress of the starter draw on your master selenoid contacts, making it last longer. The master only then has to provid power to the instruments, lights and throw the contactor in the starter selenoid. Cessna has done it this way forever. Crash
 
Crash, by removing the master solenoid from the circuit you also remove important safety feature. If the starter solenoid shorts, there is no easy way to disconnect the starter. This is of course a remote possibility but...

Stan, check the voltage at every connection of the + circuit (battery, battery box, solenoids, starter) while you are starting. Use the neg terminal on battery for ground reference (-).
If this doesn't give you a definite voltage drop, then do the same for the minus circuit. Use positive terminal on battery as a plus reference. Check voltage at battery box, fuselage ground tab, engine mount, engine and starter while starting.

Look for corrosion at all connections.

By doing this step by step, you should be able to locate where the voltage drop occurs.

Vidir
 
Seleniod

Iceman: The selenoid I have had go bad in the past is the constant on master selenoid (hooked up the Piper way). Haven't lost a starter one yet. I hear what you're saying, but just prefer the Cessna way of connecting the selenoids up as taking the starter "power hit" off the master, just one less set of contacts to fry. Crash
 
Underseat battery

After chasing my poor starting problem for sometime, I replaced the PC680 battery (less than a year old) with Hawker's new SBS J16 which looks identical and some distributors claim it is identical. The new battery spins the 150 hp nicely, just as the PC680 did when it was new. I took the PC680 to an automotive electrical shop and had it load tested along with the new SBS J16. The new battery passed the 200 amp draw for 45 second test. The year old PC680 would not hold 100 amp for 15 seconds. Even though both showed 12.8 volts, the proof was in the amps drawn. My charging system is puting 14.8 volts at the battery which I'm led to believe is normal. Just curious if anyone else has experienced short battery life with the underseat installation.
 
:wink: With a 5-volt drop in the starter circuit, something should be getting very hot. If the starter is drawing 100 amperes, that's 500 watts. Crank for about 15 seconds and then feel all of the connections (carefully). I think you'll find the problem. ...Clyde
 
underseat battery

My last post may have been confusing. I found no major voltage drop in the starter system. Batteries ( Sealed Lead Acid and PC680 ) just don't seem to have much more than a six month life. Failure to hold cranking amps was discovered during a bench test of all three batteries. New battery passed the 200 amp for 45 second test. Six month old batteries would only hold 100 amp for 15 seconds. Am I extra hard on batteries ? Help !!
 
Often over charging the battery consistantly will ruin a battery like that. Sounds like your alt is putting out ok, but the regulator is not shutting down. in a vented battery, you can tell if the fluid levels are consistanly down, but a sealed battery is hard to tell, and those small batteries cann't absorb power spikes like a larger battery.
My underseat sealed battery has held up for 18months now.
Carl
 
supercub said:
I'm curious.............I've never seen one of the under the seat batteries. This is under the front seat?? There's enough room with the master cylinders and parking brakes?? Also...........how do you run the cables (wires) with the floor boards in place.......I assume you run them up the side similar to the original, but how do you get it from under the seat to the side with the floor boards in place? Also........where do you bolt the ground cable........and last......how much weight does this save..........whops......one last question...........on the smaller battery you're installing......how does it compare to cranking power?? This looks and sounds like it might be a good mod. Thanks for the info
Brian

Mine is under the back seat and the field approval includes a big tool box. It does require raising the back seat about 2" with some saddle brackets.

Unless someone knows something I don't, the Odessy battery is not STC'ed or approved in any way by the FAA. I have never ever heard of a Field approval on it.

I do run the Odessy in the summer but replace it with the big 35 amp aircraft battery in the winter.
 
Cubdriver, Here is a pic of the under front seat battery mod I just did using the STC from Dan's A/C w/FAA/PMA Hawker battery and the tool box I installed under field approval. I got it from CC but found out Stoddards has it cheaper.

battery.jpg


toolbox.jpg
 
Steve Pierce:
Nice looking install... I've heard that Dan's battery mod does and does not require welding; which is it? Your pic looks like everything is screws and bolts.
 
I've put in the Dan's kit that Steve has pictured, I don't remember using the welder. I remember it being a good kit, with STC. The only possible drawback I could see was that it replaced the seat bottom springs with a piece of flat stock, but if you have a good seat cushion, it shouldn't be to hard on your hind quarters.
 
Great kit, no welding, drill and screw it down. Comes with everything except the wire terminals. I hate kits that you get started and relize you need this or that to finish.
 
My PA-12 has the battery relocated to between the rudder pedals adjacent to the firewall. I don't have the records with me to see whether it was done with an STC or a 337, but I'll check next week.
 
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