martinss

I know that there are lots of options as to how to make a quick connect for a trickle charger. My choice was to connect the plug-able harness from the charger (I added an inline fuse):



to the battery post under the hood and the ground point behind it:



and feed the harness out under the rear edge of the hood to connect to the charger:



It tucks away above the firewall when not in use. I taped it in red and added a label to remind my old self what it is for...

Alan

Trickle chargers/battery maintainers often won't charge a severely depleted battery... if the voltage is too low they just don't turn on.. check? the sooner you recharge it the better - if its been sitting fully discharged it will never fully recover, the longer the worse it is.

Alan

dr bob

Adding to Alan's suggestions, a six year old battery is well beyond statistical end-of-life in 928 service. While you might be able to get it tos how OK terminal voltage after a long charge, it will be short on capacity. You can test the specific gravity of the electrolyte with a simple/cheap floating-ball tester, available at parts places for under $2. Charge the battery as completely as you can. Then just draw a fluid sample from each cell with the tester, and the number of floating ***** will give you pass/fail/marginal indication. If any cell is weak or fails after an extended charge, it's time to replace the battery.

19psi

I think the last time I saw a non maintenance free car battery was in my dad's Corvair. He taught me how to use the gravity tester with the little ***** in it. I must have been 4 or 5 at the time. When it eventually got replaced (mid '70s) he bought a maintenance free with the little glass eye that changed colors.

Outside of the cheapie Walmart motorcycle batteries, is there really a company still making non maintenance free car batteries? Maybe common in countries outside the US?

I recently replaced the batteries in two of my cars. One made it 15 years and was still ok, just didn't trust it and the other puked at 12 years.
I sold a truck to my friend a few years ago and it still has the new battery I put in it back in 1995.

Why does a 928 eat batteries? It's in a perfect environment...not a brutally hot engine compartment subject to extreme temperature changes and vibration.

Alan

Many 928 batteries (in the specified types) are wet cells with cell access ports...

So still out there - can still test specific gravity directly - and top up...

Many folks have adopted gell cell batteries - not all of which fit optimally.

Starting a big V8 is quite a stress on a battery, and it can still get quite warm there - when it is self-heating the enclosed box is not so ideal. If your alternator is marginal then the battery can be negatively impacted by what would otherwise be an acceptable drain - especially on rarely driven cars and under summer (hot) conditions.

Alan

Randy V

If the cells became dry, chances are they have oxidized and the battery is now toast.

MainePorsche

+1
Time for a new battery.

dr bob

Amen--

The reason the cells go dry is that sulfates are bridging the plates. It's kind of chicken or egg, since one increases the chances of the other in a precipitous (sorry...) fashion.

I've watched battery "rebuilders" stick a high-current charger on such batteries, and boil/dissolve enough of the sulfate bridges out to make it look like it's OK for a very short while. I've grown tired of wrestling with the problems of trying to reanimate an otherwise battery corpse, and then rediscovering the thing dead too soon afterward. Besides, tired batteries take a huge toll on alternators. So if I charge it and it still fails the specific-gravity test after sitting an hour, it's off to the battery store for a new one.