Due to travel and other reasons there may be times where my IS 500 could go two or three weeks without use. I’m thinking I should probably connect a battery maintainer. Have any of you done this? If so which one do you use? Is it permanently installed? Do you have to leave the trunk open to plug it in and if so do you disconnect the trunk light?
I appreciate your insights!

 

I used this when I had my IS500 in storage for 3 months in the winter. Works great. There are cheaper products but this product is one of the better ones IMO.

I have gone 3 weeks with mine not used, it started right up. Assuming you have a newish battery, I doubt you need a tender but it can't hurt. If you have convenient access to AC power, you might as well.

https://www.ctek.com/us/battery-char...tARs4jQXQ5KZFq

 

OP - For 2 to 3 weeks, you should be fine. I put mine away from late November to early April and during that period, I will put mine on battery tender once a month to bring the battery to the "full charge" status. I use the CTEK brand and have always been happy with it, but while I know I can leave it plugged the whole time, once the light shows "green", I just unplug it and redo the process a month later.

I am not sure why you mentioned the trunk as the battery is under the hood. In my case, I can easy put the wire in a position where I can shut the hood without negatively pinching the cable

EDIT - Flying and I are obviously alike, must be a northeast thing (lol)

 

This is the one I use:

https://no.co/genius2

A great product. Search their website if you want one that mounts permanently to the firewall and battery. All you have to do with that one is plug it in. I have to move mine between my IS and Tacoma.

 

Buy an OBDII to cigarette plug adaptor from Amazon and plug it in under the dash. You can close the door on the cord with no harm.

 

I am a big fan of the Battery Tender brand. I have many, many years of hands on experience in the motorcycle world with Battery Tender on several different bikes and types.
Located right in Deland, Florida…about 40 minutes west of Daytona Int’l Speedway

https://www.batterytender.com/pages/automotive

 

Battery tender is still the best i have found

 

Different experience....I had a Battery Tender, just sitting there doing its float thing, short out, smoke and trip the wall circuit breaker. Never bought another one. I swear by CTEK.

 

Agreed, 2-3 weeks you'll be fine. I went on vacation for 18 days, so about 19 or 20 days without driving and my 2025 started up right away, no issues.

 

Since my cars sit occassionally for 2 or 3 weeks, I have a NOCO portable booster as a backup in the event that my battery dies. I charge it up on occasion but it really holds it's charge for a long time.

 

Originally for aircraft batteries, these guys expanded to automotive uses -- have used for over 10 years now

https://www.batteryminders.com/

 

I'll echo the comments here that for 2-3 weeks you should be fine without the battery maintainer. I had mine sit for a month once (might have been almost 5 weeks actually), and the car started up fine. The key, however, was to then drive the car for more than an hour to fully re-charge the battery. Just starting up the car for a few minutes at a time is actually worse on the battery due to the high current draw needed for the starter motor. During the winter, I also go through 2-3 week periods where the car sits, but then when I take it out I usually drive it for more than 30 minutes, minimum, to fully re-charge.

 

I'm no electrician, but I would argue that a few days is fine, but our cars have a fairly high amount of computing going on, and the car never really goes to sleep. That's why I chose the NOCO GENIUS2. It only charges at like 2 amps, to keep it topped off. I believe letting the battery discharge hevily then recharge is worse for it than keeping the charge level high all the time. The NOCO is better for battery longevity. Any longer than a week, and I plug mine in.

 

The properties of lead acid batteries are pretty simple: for maximum life, they want to be fully charged. The more you drawn down this type of battery the more its life is shortened. All modern cars have continuous drain and, although there may be enough capacity to start after 2-3 weeks, the battery capacity/life will be reduced. How much? Doesn't matter to most people because they don't keep the car long enough to matter and/or they never need full capacity for starting because the car doesn't live in a sub-zero environment. I have always been OCD about my batteries. When I had a garage, I kept a trickle charge on the the battery if I wasn't driving the car every day. Now that I live in an apartment, I keep a 20w solar panel plugged in when I am not driving the car.

 

Basically all my cars/bikes/even my mower have a permanently installed DC port.
Gonna sit more than a week? Gets plugged in. I have a couple of 10w and 20w solar panels with suction cups that I've been known to just toss up on the windshield if it's away from a plug. Alternatively get a panel with a obd2 plug and put it between the windshield and sunshade. Not to mention Battery tenders are cheap compared to cost of batteries. Doesn't matter what brand, just that you use one. Spend according to how fancy you want it to be. Make it easy to plug in, and let it float. Modern stuff have so many electronics that even parasitic losses will pull down a battery in time. And lead doesn't like existing at anything but full. Usually get 5+ years out of a battery, despite Florida heat.