Aux battery specs NHW11 post-TSB

mecram1 posted back in October that the upgraded NHW11 aux battery supplied by Toyota in connection with a TSB is a Panasonic S55D23L. I can confirm this, as I've just had the one out of my NHW11 to look at it. (Therefore, mine's had the upgrade done some time in the past.)

The dimensions I measured for the Panasonic battery are 8 1/2" long by 6 5/8" deep by 8" tall (not including posts). It has the negative post on the left and the positive on the right (as you face the battery with the posts nearest you). The vent hose attaches to the other corner on the negative-post side. The posts are the conventional diameters found on batteries in the US. I keep reading about the original NHW11 battery having odd-size posts, so clearly the dealer upgrade included new clamps the size of common US posts, as well as the new tray.

By Googling S55D23L I found a lot of pages in languages I don't read, but I also found English-language hits from ACDelco, which also sells an S55D23L. The specs on the ACDelco version are 232 x 173 x 205 mm and 60 amp-hours (measured at the 20 hour rate). These dimesions are slightly larger than the inch measurements I took of the Panasonic, so I'm not sure the Delco would quite fit: the Panasonic is a *very* snug fit between the wheel well and the HV battery vent duct. (With a heat gun it might be possible to re-shape the vent duct a tiny bit.

ACDelco also makes an S70D23L in the same dimensions and 8% more amp-hour capacity.

If the Panasonic specs are close to the Delco ones, then the dealer upgrade was a big improvement over the original (if the 28 and 31 Ah figures I keep reading for the original and the Miata replacement are accurate).

I'm not considering cold-cranking-amps here because the aux battery is never used to crank (and CCA figures around 400 or 500 A are sort of moot when there's this, you know, 120 A fuse built into the + cable terminal). If I understand right, CCA is maximized by increasing plate surface area, usually meaning lots of very thin plates, exactly what you *don't* want for durability and cycle depth, so an aux battery with a large Ah capacity and modest CCA would be good in a Prius.

None of the Delco literature I found had pictures or any more details on their S55D23L, so I don't know whether it is also designed for a vent tube and otherwise comparable to the Panasonic. From the similarity of numbers I would like to think so, but it would be nice to know for sure.

-Chap

 

Cool! So it's a 48 AH battery. Not 60, but still a nice upgrade over the original 28 or
the Miata 31.

-Chap