I'm new to Corvettes, we have a C4 and a C5. I bought two NAPA battery tenders, Model 85-201, for the Corvettes since we use these on our 65 GTO and 65 LeMans top post batteries in the winter and they work great (although the GTO and LeMans batteries are disconnected on the negative side). I hooked up the battery tenders, without disconnecting the batteries, and the darned tenders cycle back and forth from charging to charged about every 5 seconds! I don't think this is normal. I have heard (maybe incorrectly) that I don't want to disconnect the negative side of the battery because all the electrical stuff will lose memory. I need some help on the best way to set the batteries up for the winter. We have pretty cold winters here in northern Nevada and I know cold is not good on batteries and they don't last as long without battery tenders. Thank you!!

 

Thank you for the reply. I did contact NAPA and they didn't know the answer. I will call the toll free number on Monday (office was closed for the holiday weekend).

 

Stupid question but do you have a door open or hood up & light on? I have a small green tender (I think its called Tender? )you can buy them at pep boys or auto zone and no problems. G/L

 

My guess is that everything's fine. I use a Sears automatic charger and leave the battery connected also, in my case the charger cycles between "charge" mode and "float" mode every 60-120 seconds all winter long. I think the ECUs, alternator diodes, and various other current draws that are present in the vehicle discharge the battery which is why the charger needs to go to "charge" mode periodically. I've done this every winter for 10 years and all is well. (2000 Hardtop)

 

Your OWNERS MANUAL recommends disconnecting the battery for prolong storage. How hard is it to reprogram MEM-1 & MEM-2 if they go away??? Its NOT! Disconnecting the battery for prolong periods of time does NO harm to your car. All your critical tune information is written to NON VOLATILE MEMORY and will not be effected. There are idle and LTFT tables that will default to factory settings but driving normally for a short trip will relearn all that info normally.

Your PCM/BCM constantly draws 20-25 milliamps from the battery when the car is in the sleep/security mode. If your battery is not fully charged your battery charger may be reacting to that condition. Fully charging the battery and leaving it disconnected for a few months in the cold does NOT damage the battery.
I purchased a new WALMART battery for my 97 F-150 because the 11+ year old battery that was in the truck BUGGED the hell out of my wife. The new battery was a STAND BY just in case my OEM battery bit the big one. One year later, I sold the truck "with the 12 year old battery still in it". That spare NEW battery sat fully charged in my covered portable garage on the concrete for another year. Just recently, the battery in my beater Jeep, went bad. So,,, I grabbed that new spare battery, connected it to the jeep and it cranked the jeep WITHOUT ANY PROBLEMS. Yes, it needed to be charged and I did put it on the charger after it was in the jeep BUT, sitting out in the hot and COLD for two years, did not kill the battery.

My recommendation would be to fully charge your battery and disconnect it for the few months that your not using the car.

Bill