Ghetto battery tender

I'm going to leave a lead acid battery for 2 or 3 months doing nothing. I already had a battery charger which will automatically stop when the battery is full, and I bought a christmas light timer so I can have it on for 30 minutes of the day when I know my roommate will be home.

Do you guys think this is a good idea? Letting lead acid batteries hate deep cycling and I'd like to avoid that with this new battery.


I'll have the battery in a large metal bucket should the worst happen.

 

Lead acid’s like to sit at full charge to the best of my knowledge so I’d say hook up the charger and skip the lightbulb.

 

There's no current draw on the battery (which wouldn't be the case if the battery was installed in a parked car). I'd say 30 minutes each month as opposed to each day is enough.

 

For storage of a couple months, just make sure to fully charge the battery and store it in a cool place. Thats not likely long enough to need anything.

A ghetto tender could actually be counterproductive if it tries to bulk charge every day and tbh the name brand battery tender isn’t what it’s cracked up to be either.. it’s just a dumb trickle charger that will overcharge if used long term.

The best way to long term store and avoid sulfation is to use a true float charger that just holds the battery at 13.2v, but most of the units that properly do that are expensive 4stage chargers meant for off grid solar storage systems.

It isn’t actively updated anymore but the batteryfaq web is the definitive reading on this subject:

https://alshain.a-centauri.com/batteryfaq/carfaq13.htm

https://alshain.a-centauri.com/batteryfaq/carfaq9.htm

 

Use proper equipment for anything related to batteries and charging.

I seasonally store multiple cars, I typically disconnect and leave the battery in the car. I have done it for years, and it does not appear to reduce battery life. More so, fully charged healthy battery that sat disconnected in the car in a climate controlled storage for 6+ months retains enough charge to start the car. I also have battery trickle charger (ctek) that I connect in cases where I have parasitic battery draw and I don't feel like disconnecting battery.

That is for lead-acid batteries. My understanding that EVs and Lithium-Ion batteries are more finicky. I have no first-hand experience with these.

 

https://no.co/genius2

 

Your instincts are on the right track.

Lead Acid batteries degrade by sulfation of the lead plates whenever they are less than 100% charged. The best way to avoid this is hold them at full charge by “floating” at a slightly elevated voltage that’s high enough to prevent discharge but low enough not to start boiling off- typically 13-13.4v depending on chemistry.

Only off grid storage charging systems do this perfectly but for commercial car battery management NOCO and CTEK get close enough.

Lithium Ion batteries degrade through more complex mechanisms that I don’t completely understand including lithium plating and crystal formation on the electrodes. Unlike lead that simply likes to be full, lithium damage happens at both low charge states AND high charge states so the best longevity comes from keeping them as close to half charged as possible at all times. EVs manage this with complex charge algorithms that often use only 60-70 of the true capacity by stopping the charge at 80% full and reporting empty at 20%. Power tools do the same by only charging to 80-90%. For other consumer devices like phones and drone batteries if you can try to put them in storage at half you will get the best life.
https://batteryuniversity.com/article/bu-808-how-to-prolong-lithium-based-batteries
https://batteryuniversity.com/article/bu-808b-what-causes-li-ion-to-die
https://www.sciencedirect.com/science/article/abs/pii/S2590116819300050