Alan

Oh and Dr Bob - I was thinking about AC - but I wanted it piped directly to my seat...not the battery ... priorities priorities...

Alan

Alan

Ok folks - so here is where I am at with this.

In prep for this I already have done some reconfiguring of the paseenger side fender ahead of the wheel. I have a trickle charger in there - fortunately mounted quite high up and also a HID control units - but this is well forward.

Here I've already moved the horns upward & outboard a little - using the mounting points for the trickle charger.

I removed the horn carrier and plan to use the existing threaded mounts for that and the spoiler to bolt the battery carrier to the front frame member. I've measured it all out and tried a dry fit - it seems it will work and the battery will be lower than the midpoint of the wheel.

I have an aluminum mouting sleeve for the battery but without a flat surface to attach it to - it needs some kind of carrier - here it will be hung down from the rail so I'm looking at building a strong aluminum cradle for this..

Alan

a4sfed928

Why not just replace your battery with the built in reserve type?

Alan

I have seen the patents and announcements for built in reserve batteries - but thats all... I am unaware of any shipping products of this type...? anyone know of any?

Its clear the big battery companies aren't pursuing this - and since its not exactly rocket science....why?

I think its an economic issue - on the face of it it has major challenges - since batteries can't be repaired - if either part dies - you have to throw away one good part with the bad part (and probably the charger electronics & switch too). Sure it buys you security that you can get home... but if the replacement cost is higher than with 2 seperate batteries its just a trade off... and of course if they are not widely available everywhere you'd possibly have to setlle for something else in an emergency anyway - then no backup...

It will also be a huge challenge to fit the standard & reserve in the same physical space - so its likely that such batteries will be physically larger. in a truck thats often OK (or for new OEM use) but in our battery box not very doable...

(BTW - I suppose a true "reserve battery" would have an undeployed electrolyte ready to go - but I don't think thats what the patents were about - they sounded more like a built in seperate backup battery... a traditional chemical reserve battery would only buy you a very short amount of time if it were not lead acid rechargeable)

I also have some other motivations for reconfiguration that would not be possible that way - assuming these dual batteries have a built in charging system (voltage controlled charging for instance) and a battery mounted combine/changeover switch.

Alan

Alan

Dr Bob - here is that previous thread

https://rennlist.com/forums/showthre...eferrerid=6055

Looks like those batteries were something other than an Odyssey gel types - they are smaller than the smallest of the Odyssey types (PC 310 @8Ah). With a pair of PC 310's in parallel back there they would come close to being equivalent to a PC680 battery. A switch & charging system could probably fit at the back too. The wiring would probably be 5-6 feet to the battery connections but pretty doable and you could use it for accessory / Audio power as Dave demonstrated.

Except of course this wouldn't work so well for if (like me) you have a full set of tools & jack/lug wrench there already. But it could be a viable options for those that don't. It has a little lower max cranking & Ah but also weighs a few Lbs less... Unfortunately one single PC310 seems to cost more than a PC680.. not so good.

Based on the pricing Dave mentioned - I'd assume the ones he used were significantly less expensive - so I'd assume probably not starting capable batteries.

Alan

Alan

OK - not sure if anyones really much interested in this one - it is a bit of a unique idea.

Anyway I have been busy with more fabrication. Its not in the car yet - since I'm working around some other issues with the whole scheme. Ultimately this will include new alternator and wiring to/from starter to CE panel including some new fusing and relocation & upgrading of some of the main power supplies etc. Since I want to be driving the car daily this will require some care in partial installations. The next step will be to put the battery & charging system in the car.

Here is where I am at. I have built the battery hanger mount and the charger relay & diode mount/heatsink. I've soldered up the lug ends of the main connection cables in 4 AWG (charging) & 2 AWG (starting).

I've also started construction of the battery isolator/changeover/run/combiner switch, voltage monitor, CE mega fuse & a new front jump post and a new distribution fuse panel set-up. So far I'm fairly pleased with how its coming along - several big parts of installation to come: Battery/Charger System, Control/Fuse Panel, fender feed throughs, main wiring to Starter/Alternator and new fuse implementation on the cooling fans & ECU's.

Progress so far:

Alan.

ew928

I REALLY like the instructions taped onto the battery.
Nothing like brain fade a few weeks after installation.

Can't wait till the "test" when the main battery is taken out of the circuit to try the power of the aux cell. Or is the aux cell not enough to damp any voltage spikes that the main battery would have eaten.

Alan

Ernest - yes in anticipation of forgetting it all.. And actually its not immediatly obvious how to remove it looking at it - but I did plan for easy disassembly & removal..

It is quite capable of acting as the only battery - and many use it as such for racing. It does not have the reserve capacity of the main battery - its less than a quarter the total Ah - but can supply well over a 1000A for a few seconds for starting. It could be used for running indefinitely - but then in case of alternator loss - you be running for maybe 20-30 minutes max - so not ideal...

Alan

RicerSchnitzzle

Nice work. Looks like a very clean installation. Lots of info on this stuff on the 4X4 boards. On the location, seems like you could have gone with a smaller main battery and put the second battery setup in the battery tray in front of it. Again, nice work, you have obviously done your homework.

This should work well to help with your back up battery plans due to the heat. Don't think it will help in a high output audio / electronics set up. Better to use a cap or spiral battery set up since the recharge rate is faster. Dual batteries with audio is great for about 1 minute, untill it's deleted the batteries. Even a yellow top only likes to see 3-5 amps of charging rate. A couple bass notes can kill the battery faster than it can recharge. Most heavy audio systems use larger caps, spiral cell batteries (Kenetic) or multiple alternators. You normaly only see multiple battery set ups in db Drag race where they have tons of batteries powering a system for 30 seconds only. Now in a moderate system with a single 12 and a small 4-500W amp, this would work well.

BTW I thought Sears Diehard had the reserve battery? I know I have seen the commercials for it. "Lady parks in long term parking at the airport..battery dead, she flips switch on top of the battery, starts car, switches back and drives off."

Alan

Yes I looked at lots of 4x4 dual battery info. I didn't like many of the automatic systems they use because they are so huge. In the end I like the ability to use small standard parts and I wanted direct switch control of the battery configuration.

The main battery supplies the audio via an unusual diode fed audio cap system. I don't expect to use the audio extensively without the engine running - and I plan an upgraded alternator for general running power and recharge capability (even at idle).

My system maxes out at just below 500W - possibly a little conservative - but its not huge - quite adequate for me (I know you like much bigger!).

I am not familiar with any dual battery with (charger/switch over) available - they may be there but I was not able to locate any... looked quickly for a Sears Die-Hard version - didn't find it...?

Alan

michaelathome

Alan,

Take a look here. http://www.killacycle.com/photos/12-...acing-battery/

Michael

Alan

Interesting - very small - but 240A is very low for a 928. The stock battery is 650A. It may work some of the time but probably not reliably cold.

The Odyssey I have can support >650A although not for anything like as long as the stock battery can - it should start the car under any conditions

Alan

the flyin' scotsman

Alan..............sorry I'm a little late in seeing this thread.

My telecom career involved many batteries to the point where we were using batts from a manufacturer more akin to producing product for submarines. These folks were in Manchester, Engalnd and I got to know the DM well.

Perhaps there's a solution there.

Alan

Well I have been working away at this project methodically... mainly on the controls side. But I did decide to pop the battery in and see how the car rides with it there (not connected to anything yet...).

Well the installation was initially a pain - the fit was just too tight - the fender curves in too much. I decided to reconfigure a little and moved the 200A relay to the back of the cradle - still a similar position and the wiring is only just slightly longer to the diode pack. I did need to remake the lexan covers again...

Still for an investment of about 2 hours it went in and now fits well - it hangs perfectly at the height I had planned and its center of gravity is well inside the center-line of the wheel and just below the axle level. With the carrier frame it could not be any snugger of a fit - however the battery is still actually quite easily removable with the frame bolted in - convenient (of course you still have to take off the wheel, liner & splash shield first...). It is as solid as a rock mounted there. Impressions of driving are that it didn't make much noticeable difference. It actually probably balances the car slightly better if you are driving alone - and slightly worse with a passenger in place...

On to the next phase - replacing the main supply wiring to the jump post/CE panel & cooling fans - its hard to implement changes like these when you want to still be driving the car basically every day...

I don't expect anyone else to be interested in implementing this idea. But it is interesting that Cayenne's have an auxilliary battery (at least early ones did).

Here are the mods I had to do to the carrier frame - moving the big charging relay - and a picture of it installed in the front passenger fender. Finally: status as of now of the battery switching panel with DVM/switch, CE fuse and new jump post and fuse panel for a new feeder to the cooling fans/ECU's/Clock etc This will go basically where the jump post is now (also a tight fit).

Alan