[jsomtiques]

I have a pretty nice 1988 burgundy Allante. Not a show car but a quite nice driver. We only drive it after the roads have been rained clean of salt and do enjoy the car. Maybe about 3000 miles a year for the past 6 years. There have been several issues mainly electrical but I am lucky to have an actual mechanic that likes the car. When it goes to him he keeps it and drives it like it is his own until the problem has been found and repaired. Since he likes to drive it he does not charge me near what he should. So. in the fall I disconnected the battery cable under the hood, gave it a good cleaning and waxing, patted it on the head and covered it up. This morning I uncovered it and called my insurance guy. I hooked up the battery and it was dead, dead, dead. I then put it on my trusty charger and the needle just jumped from 0 to 10 in rapid order. It has not done that before but I figured it would settle down and go to work. After about an hour I went back to it and I had lights, front and rear, blinking on and off, also control panel lights blinking and the door key chime going off. I unhooked the charger and came here. How much trouble am I in? I will get with my mechanic when he returns from his vacation next Monday but I would like to solve this myself.

 

[kiwigram]

In my experience, when the battery is completely dead, you need to disconnect the battery negative cable and charge the battery directly. Don't charge from the connection from under the hood.

 

[carnut]

When the battery is that dead, a charger might not be able to start the charging procedure. If the charger is trying to inject say 10 AMPS or more too quickly, it will try, cut off, and try again and again. That's why your needle is bouncing. Try a lower amperage charger like a motorcycle one, they start at about 3 AMPS. Because of the low voltage, your alarm is going off. Just put the key in the drivers door and turn it to disengage the alarm. If I were going to store it, I would put a trickle charger on the battery. How old is this battery? Once it restarts, the idle relearn procedure has to be done because the idle memory has been lost. AND the proper way to disconnect the battery is at the battery itself.

 

[Tn Kjun]

My advice is to go to Harbor Freight and get you a battery tender for winter storage to avoid any electrical problems. Every time the battery is disconnected the computer has to reset or you have to do it manually.
Not a good idea ! And also, a battery tender will add years of life to the battery.
BEEN THERE, DONE THAT !

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And for safety reasons of the electronics in the Allante, don't try to start the car with high output from the battery charger cause you could fry something .
I did and it cost me a CDM ! (Radio computer )

 

[jsomtiques]

Thanks for all of the help. So, what I did was crawl through the car, remove the cover, screw 9/16" bolts into the battery and hook up the charger. The charger started slowly, about 4 amps, and increased to near 10 amps. I checked on it about every 30 minutes or so for a couple of hours and it did just fine. It charged for about 6 hours and shut itself off. I hooked the battery back up to the car and let it reboot. I did not hurry this process, I let it lay for about an hour before I turned it on. Everything came to life and it seems just fine. We had two nice days and it is again waiting to go for a ride, maybe next week after all of the bad weather goes past. Also, the next time I do to Rockford, I will go to Harbor Freight and get a tender. HEY, thanks again for the response and help.

 

[kiwigram]

Good to hear that it worked out. Thanks for the feed back to let us know all is well. Did you reprogram the computer? Page 285 in the owners manual

 

[Submariner409]

A dead battery "looks like" a perfect short circuit to ground - to a battery charger. Thus the weird needle jumps.

Something to remember - a dead battery will freeze and burst: The "electrolyte" in a dead battery is almost pure distilled water - the sulfuric acid component is deposited on the plates as lead sulfate, which is normally a gooey gel. Left for a period of time the sulfate crystallizes and no amount of charging will fully recover the battery, no matter how new or old it is. A fully charged battery, disconnected from anything for a half hour, should measure 12.6 volts at the terminal studs.

Below 11.9 volts or so, few batteries will start a car engine. There is just no "woof" left in the charge.

A small 1.5 to 3 amp battery minder, connected to an almost fully charged battery, will charge the battery, then ramp down to a voltage of about 13.1 - 13.3 volts and a very low milliampere trickle - just enough to keep the battery fully charged and supply the car's residual electrical draw.