Bilque

After not driving the car for over a week, the battery was dead and I discovered that I had not fully shut the trunk. I hooked up a charger/maintainer with the battery still installed in the car and it has been on for 48+ hours and it still shows as charging. I have several of the chargers and use them on other cars/motorcycles where they work as expected. I've never had one take this long to indicate charged.

I'm sure others are using maintainers and wondering if it is normal that the charger does not indicate full charge. Voltage with charger running is ~14.7 and ~13.7 unhooked. I believe it is a 4a charger.

What is normal voltage when fully charged and what is minimum voltage to crank starter?

Should have measured the voltage before hooking up the charger to know low it was......

FLYCT

@13.7v unhooked the battery is fully charged.

I use both a battery tender jr and a battery tender. The jr outputs 3/4 amp. The battery tender outputs 1.25 amps. I've used the on the cars and my motorcycles.

Our batteries have about 70 amp hour capacity so you can do the math to see how long it takes to fully charge. My battery tender takes about 3 days to fully charge a completely dead battery if I leave the trunk unlatched.

Your 4 amp charger should be able to fully charge a completely dead battery in one day.

About a year ago I posted voltage readings and charge currents i measured at different times. I'll see if I can find it and post a link. It showed what voltage the battery tender jr switched from charge to float mode.

LexBrett

I thought we had a 16v battery? My battery varies between 12.5 and 14.3. I have changed the battery at least 3 times in 6 years. These batteries seem to die quickly, perhaps due to some parasitic drain?? Now I use a battery tender, and hooked it up with the permanent mounting software..

FLYCT

I found my old posting. Mind you, this relates to my Battery TenderJR 3/4 amp charger and the 100 amp/hr battery in my LS460.

Read all the postings on this thread.

https://www.clublexus.com/forums/ls4...charger-2.html

To summarize my readings,
Initially the JR was in constant current mode (solid red light) pumping almost 3/4 amp current into the battery.
The battery voltage slowly crept up from 12.x volts and eventually after several days finally reached 14.2v.
Once it reached 14.2v the JR switched to constant voltage mode (flashing green light)
Once the current required to maintain the 14.2v dropped where the battery was fully charged the charger switched to float mode (solid green light) and maintained current output to keep battery at a safe 13.04v.

FLYCT

Here's a good "State of Charge" table. Measure the rested battery after being off charge for several hours and based on temperature you can find % of charge.
http://jgdarden.com/batteryfaq/SoC.xls

Based on the chart, at 80 degrees a fully charged maintenance free battery should read 12.8v..

If it reads 12.0 volts it's only 25% charged.

Bilque

FLYCT - thanks for the link and info. Exactly what I needed.

mandyfig

Harbor Freight has some good battery charger/starter. I have 2 sets. Use it in winter months all the time.