Finally replaced my 8.5 year old 12V battery! Non AGM???

I've been watching my 12V battery fairly closely over the past few months, trying to go for a record for how long the little oem battery could last. But alas it couldn't make it through (southern hemi) winter and started going down-hill really quickly over the last few days. It's was hitting as low as 10.5 volts in the ig-on test, and I actually saw it transiently dip as low as 9.6 volts during boot up. Yikes!

So yesterday I had to change it out pretty quickly as my wife needs it to be reliable for a trip next week. Didn't have time to order anything online so it was either the Toyota OEM (about $350 here) or take a punt with whatever the local battery place had that would fit. It turned out they had one for a third the price of the Toyota one, except it wasn't AGM! It is however fully sealed and maintenance free, it is a low self discharge calcium type, and it does have the attachment for vent tube. The guy there assured me that it meets all required standards for mounting inside the cabin space, so I decided to give it a try.

Here's a pic of my new el cheapo. The picture doesn't show any reference to see it, but it's tiny! Literally about half the weight if the OEM battery I removed. The rating is still 35AH and 330CCA, so it should do the job.

 

Hi Jimbo. This battery is well sealed and is supposedly designed for this application. It has the facility for the vent tube (which I have attached). It's a very lightweight battery and very firmly secured, so I think it will be ok.

 

Yeah that's the one Jimbo, the S40B20L. It's a tiny battery. Feels like it's only about 10kg, and it's got a built in hydrometer (sited though a little window in the top).

Yeah if it gets hit hard enough in the rear to split the battery case then the OEM battery would also split. But the acid in the OEM would leak more slowly.

 

Thanks Mike. Yeah the battery is very sturdy. Jimbo's point however is that if the AGM battery ruptures then the acid will leak relatively slowly compared with a traditional battery. In any case though, I think that any acid would be contained there in the wheel well.

I wasn't going to compromise on the vent though. I did have to very slightly modify the vent tube to accommodate this battery, which was easy enough, though I wasn't really expecting to have to do this given that the Acdelco catalogue listed it as a suitable replacement for the Prius.

For those interested in measured voltages, this battery measured 12.5 volts out of the proverbial box. I assumed that it might have been sitting for a while so I gave it a light charge and it settled to about 12.7 to 12.8 volts a few hours after charging.

Once installed in the car I got the following readings on the MFD using the "acc/ig-on/ready test" (each measurement taken after giving it about 10 seconds to stabilize) .

Access: 12.5 Volts
Ig-On: 12.2 Volts
Ready: 14.0 Volts

BTW. I repeated the test two consecutive days with identical results.

 

Yes jadziaman, it came with the small JIS terminals and was a perfect fit. I didn't measure it exactly, but it's about the same height and width as the OEM battery but is a lot shorter (in the terminal to terminal direction). The positive post lined up perfectly with the positive clamp assembly, and so the negative post had a bit of extra clearance from the rear of the hatch compared to the OEM part. However the pigtail (-ive strap wire) still reached easily. Also, the metal hold-down piece that goes over the top fitted nicely across, about at the centre of the battery, so physically it fits in very neatly.

The only thing that was a bit awkward was the vent hole. I didn't realize until I got it home, but it was ambidextrous, with a vent hole at each end of the battery. It's similar to the oem battery in that there's a rectangular cavity above the cell vents, fully sealed off in this one, except for a small vent hole at each end. The holes are baffled between the exterior and this internal cavity, presumably to prevent acid escaping through the vents. So I had to place a small plug in the vent hole at the negative end, which isn't used. (I just used a small bolt I had lying around, wrapped in plumbers tape to make it snug fit when threaded in).

 

Yeah there's a risk in everything. Actually there's a small safety advantage in this battery (and other light weight replacements), to offset that risk. Given the very light weight, for any given accident g-force it's much less likely to break free and become a projectile. It's almost half the weight of the OEM battery, lighter even than the optima yellow top.

 

Hi wintechsw. Not much to report at this stage except that everything is working perfectly.

I was going to update this thread with the voltage measurements after it's been in the car (in regular operation) for about two weeks. Since it had been on an external charger prior to the previous measurements the voltages may be a little bit different now that it's just in regular service.

So I'll update here with more info in a few days time, and if I get a chance I'll try to post a picture or two of how I had to modify the vent tube.

 

I thought I'd update this thread now that the new battery has been in a couple of months.

I redid the voltage measurements now that it's just been driven normally for about 8 weeks (with no external charging). Measurements taken after the Prius has been left overnight without driving.

1. Voltmeter measurement directly at the fuse box jump point: 12.50 volts.

2. Diagnostic mode MFD measurement, accessory mode: 12.3 volts.

3. Diagnostic mode MFD measurement, ignition-on mode: 12.1 volts.

4. Diagnostic mode MFD measurement, ready mode: 14.0 volts.

I know that some people will say that these voltages (particularly the mfd measured) are a bit low, but in my experience they are 100% normal. For the many years that my previous battery work perfectly (before it started to weaken) it always returned *exactly* the same voltage measurements as this.

 

I had to access the spare wheel on the weekend, so while I was there I decided to take a few photos of how then new battery fits.

1. The first photo shows the general fit. The height and width and terminal sizes are the same as the OEM, so you can see that it fits nicely. The new battery is a fair bit shorter than the OEM but that doesn't seem to hurt anything.

BTW. All that brown crap isn't corrosion. It's corrosion inhibitor that I sprayed in there a couple of years ago when I thought some acid might have gotten in there (trying to add water to the old battery).


2. Here I've annotated the minor modifications that were needed to connect the vent tube with this non-oem part.