I live in Michigan and winter in Arizona and for the winter of 2018/2019 we kept the 2005 RX330 garaged in Michigan with a batterytender connected directly to the battery, positive to positive negative to negative. On return 4 months later the battery was dead. Therefore, this past winter, thinking that I may have had a defective batterytender last time, I purchased a new one. On return again on May (5 months away) the battery was again dead. Would anyone here know what may be causing this problem? I have used battery tenders many times on different motorcycles stored for the winter and never had a problem. Also, when attaching the batterytender, both times, I get a green okay light showing all is good. Could there be something with the computer system that does not allow a long term battery tender? When I have returned from Arizona i have used a regular battery charger to get the battery back to life and that works.

The 2005 RX330 is my wife's car that we bought new with now less than 70,000 mikes on it.

Thank you,
Larry

 

How old is the battery itself?

 

One year. Bought a new battery after last years dead battery . I figured since the battery lost its full charge from last year the below freezing temperatures ruined it.

 

Interesting, I'm stumped myself. I don't have much experience with BatteryTender but BMW always tried to sell me one on my old bimmers. I have used CTek with no issues and highly recommend if you are considering switching.

 

Have you left batterytender ON for all that 4 and 5 months? If Yes then you just killed both your batteries. I would recommend to charge battery only ONCE a year (before winter driving) and to do this (re-charging) in accordance with batterytender manual (it shouldn't ON be more than 24 hrs).

 

iMSQ,

I did not use a regular battery charger which would cause the problem you stated. While chargers merely charge a battery, a Battery Tender uses microprocessor technology that goes beyond merely charging your vehicle, and is designed to keep the battery powered throughout long periods of hibernation, essentially prolonging its life. What I used is what is proper for long term non-use care.

 

Battery Tenders nowadays and smart. Never had issues with them destroying the battery. I do not keep them connected all the time, I have 2 cars that I swap them with (daily swap). And if I use the car, I pass on charging until the following week. And yes I use the smart tender. I have dumped all my previous charges, ones that were heavy and bulky and hums when you are charging...I have 2 sitting in the storage. Use current technology, it helps.

 

So, I think that there is something wrong with your Tender - it looks like it's using the energy from the battery and not charge it.
PS: If the battery died within several months than there is a "leak" of energy in car's electric system.

 

I have had a love, hate relationships with battery tenders. Not all tenders are equal. Some dont actually tend the battery but charge it one time and then stops. Others will cycle regularly to keep the battery tended. The Battery Tender brand is good and actually tends the battery but I had one go bad on a stored car and it destroyed a new battery. If you are storing for 5 months why dont you disconnect the battery. Your car has electronics that will draw on the battery and if the tender is not strong enough it will not be able to keep up.
good luck

 

Your suggestion seems like the best way to proceed. It was just surprising that I had the same result with two different battery tenders and batteries on the same car.

Larry

 

+1
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Why not disconnect the battery as thats what I've done when I had a couple vehicles stored in the corner of my brothers warehouse yrs ago.

 

That can be done, but then one must remember that the battery should then be removed from the vehicle and moved to a warm location so as to be away from Michigan cold weather. Of course a heated garage would be perfect.

 

Yea it'd be great to have the vehicle in the garage, but at least its easy to remove the battery, to store the it in the house safely.......Possibly, I'd just leave it in the vehicle disconnected & get a low amp charger to charge it when you guys get back....Last winter, I Just disconnected the terminals w/ the car in the garage & it was in the low 40's or so which it sat for about 4 months thru the winter, till I sold it & it fired right off.