PSA - Don't use a Battery Tender Jr. on your Z

Vaughanabe13

Hello everyone. Just got off the phone with Deltran who makes the Battery Tender smart trickle chargers. These are the chargers I've seen recommended for people storing their car over the winter. I store my Z for about 3 months every winter and the last 2 years I have hooked up a Battery Tender Jr. to my battery. The first year after storage this way I went to start the car and it started very rough - like the battery barely had enough voltage. However I checked the battery later after driving it and it appeared fine so I just forgot about it.

Last year I again stored my Z with the Battery Tender Jr. connected. This time something odd happened. I store my car at a relative's house and asked him to check up on the tender every once in a while. He reported back that the Battery Tender Jr. was always flashing the green light. This indicates that the battery is >80% charged but not fully charged yet. All winter long it was flashing green and I didn't have access to the car so I didn't worry about it too much. When I went to pick up my Z in the spring, the battery was totally dead. Nothing. I had to jump charge it for a long time, probably about 30 minutes before it had enough charge to start up.

At this point I thought my battery was probably just old and nearing the end of its life (although that seems strange since it's only a 2009). I also tried searching the forums and google for anyone who had problems like this and I didn't come up with anything conclusive. Nor did I find any information from Deltran that said there would be an issue with a Battery Tender Jr. on a sports car. I had the battery tested after driving it for a while and sure enough the battery was fine and didn't need to be replaced, so I started to suspect the charger was at fault.

Fast forward to this winter and I just put my car into storage a couple weeks ago. The same thing is happening again. The charger is just blinking green again and never lights solid. I called up Deltran and told them the situation and they told me right away that the problem is that you can't use a Battery Tender Jr. on a sports car. They said cars like the Z have very high parasitic draw and this basically confuses the algorithm in the Tender Jr. and it can't keep up with all the electronics in the Z. They said I would need a Battery Tender Plus since it charges at a higher current. I had suspected as much, but until now I couldn't find any information confirming my suspicions.

TL;DR: Don't use a Battery Tender Jr. on your 370Z because it can't keep up with the high parasitic draw on the battery from the Z's electronics. It will make your battery die during winter storage and probably shorten the life of your battery over time. Spend the few extra dollars on the Tender Plus instead.

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2009 Nissan 370Z Touring, w/sport, 6MT, chicane yellow/black.