Howdy!

This past week I sat in a parking lot with accessories on for almost an hour, and when it was time to leave my battery was too low to start the engine. I got a jump, but it looks like the original Panasonic 105D31L-MF battery that came with this 2005 4Runner SR5 is showing it's age.

I added distilled water to all six cell and gave it a charge, but after several hours of decreasing charge amperage (started at 5 and went down to about 2), I later discovered it began climbing again (back to just over 5 amps). I suspect the resistance is either an indicator the battery is not accepting more charge, or something else. It's been working fine for the rest of the week, but I think it might be time.

Still, thirteen years with the original battery seems extraordinary.

Thats absolutely astonishing. I think the most I have gotten out of a battery was 5 years when I was living in the Midwest. Here in AZ the heat kills them within 3 years.

I got 10 years out of mine. She would still hold a charge but I decided it was time.

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That's amazing! Probably the longest I've heard of any vehicle battery lasting. Mine started getting weak a few years ago (8 years old) so I replaced it with a Northstar AGM that has been good.

That's pretty amazing. I think I got 10 years out of mine, just had to replace mine last week.

Yup, I've heard about long-lived Panasonic batteries from other forum members, too. Amazing.
Three to 5 years is typical life.

Yep, those original Panasonic AGM are great. I got 9 years out of it. Pretty darn good for CO climate, outdoor parking.

They were very good batteries. I replaced my 2003 on 12/29/17. It was 14+ years old at that time. I have since purchased a Ctek battery charger and have brought back some long dead batteries with it's recovery mode. My Panasonic was long gone with a trade in but I would have liked to try it on the Ctek.

Pretty easy on batteries up here in Minnesota though. Most of mine last 9-10 years.

Yes it's time to replace it because of the way it is acting when you charge it even though it may crank the car perfectly. Our 2006 Sport V8 Panasonic battery lasted 8 years. Like yours I left the door open a long time and it ran the battery down. I put a quick charge on it for a few minutes and then it would crank the engine okay. As long as I didn't drain it setting still it would still crank the engine after that. Then I decided to put it on the charger one day and put a long slow charge on it. The charging current at 14 volts started out at 10 amps. I went back later to check it and it was still at 10 amps.You could charge it all day long and that battery still drew 10 amps at 14 volts. So I went and put a new battery in. I had noticed over the past several months that our gas mileage had gotten terrible. After putting in the new battery it returned to what it was before.That battery was putting such a load on the alternator that it was pulling our gas mileage down. Plus it wasn't helping the alternator none either. So just because a battery will crank a car doesn't always mean it's in good condition.

Since I really admired the long-lasting Panasonic 105D31L-MF battery that came with this 2005 SR5, I was hoping to find an exact replacement. Unfortunately, they aren't sold retail (or in the US, from what I can tell).

The Panasonic 105D31L-MF battery seems to be a 'cold climate' option, larger than most replacements. It's dimensions exactly match battery group size 27 here in the USA.

I plan to replace it with a group size 27 battery, which should have comparable CCA and reserve power, or at least match the 755 CCA and 165m reserve on the Panasonic 105D31L-MF. This 4Runner has roamed the mountains of northern Nevada for over 13 years with a sealed lead acid battery, so I see no reason to pay more for an AGM variant.

EDIT: I purchased a Duracell Ultra Gold SLI27FM battery with 710 CCA for $130.

Got 10 years outta mine in Chicago weather. I was so sad when I couldn’t get an exact replacement

My 2008 has the original Panasonic battery and it's currently still going strong after almost 9 years!

Cheers!