Walmart W46B24R battery

FYI

Bought a new 12V for the Prius yesterday from Walmart. Model number is W46B24R and it was the only Prius battery on the shelf. A few observations that might be of interest.

First, the battery shown on the website as I write this:

Free Shipping! EverStart Platinum AGM Automotive Battery, Group Size S46B24R, 12 Volt, 410 CCA - Walmart.com

is not what they had in this SoCal store. The one on the web site looks like the OEM battery in my car, black everywhere and with a grid pattern on the ends. The battery in the store is marked "W46B24R", which isn't on their website, and the sticker says "410 CCA Res. Cap 75". It does not have an Ah rating on the battery anywhere. The top is black but the rest is grey, and the sides are smooth, without the grid pattern on the ends. It is still made in Korea. Serial number starts with "HAN". I will post a picture soon.

The website price is $189 "when purchased online" (or not, because the one online is not the same battery), but $195 in the store. Plus of course the various fees and taxes which brought the total to $230.95. $12 back if/when I bring the old OEM one in.

There is a vent hole of the expected size in the expected place in the edge of the black lid near the positive post. However, looking through that hole it appears to dead end against the side of the lower case. Perhaps that is some sort of film there that the vent adapter will penetrate, but it sure looks like a wall of plastic. So at this point I would give 10:1 odds for it not being ventilated.

The weight was 14360 g, nearly 4 kg more than the current weight (10638 g) of the 4 year old one in our Prius. That OEM battery may be dried out, but it isn't 4 kg dried out. There must be a lot more lead in the Walmart model. Also that is 31.7 pounds, but the Walmart website says 26 pounds.

Manufacturing date was 7/25 and voltage was 12.43V.

Spent most of yesterday charging it fully, before the planned 2 hour discharge (to estimate capacity). Started at 13:30 and gave up at 23:30. The BatteryMinder 1500 charger was stuck at 1.5A from 13:30 to 20:30, then it was in absorption phase until I gave up at 23:30. Garage was getting cold, I didn't want to do the initial charge too far from 20C-25C, and it was down to 19.1C.

This morning used the HF "Viking" tester in CCA mode and it read:

SOH 100% SOC 100% CCA 717 13.00V 4.18 mOhm

Since it wasn't really 100% charged, wanted to top it off. The BM1500 has a tendency to do a long 1.5A charge even when it starts on a nearly fully charged battery, so this morning charging was finished with a BatteryTender Jr. That only took 4 minutes at around .7A to get up to 14.38V where it switched to absorption while the current fell rapidly until it hit float mode 16 minutes later.

Tomorrow hopefully I can do a 2 hour 2.5A discharge test to get a rough estimate of the capacity, charge it up again (which should only take around 4 hours with the BM1500) and then into the car it goes. My gut feeling is that this battery is more than 45Ah, more like 50 or 55 Ah. We will see.

 

Here are the pictures. The battery is of course 90 degrees at each corner, the trapezoidal shape is a camera distortion.



The vent hole dead ends into something but it probably isn't the grey plastic of the lower case. It looked that way with my flashlight but with my son's cell phone light it is closer to white, and has a texture like a very tightly packed furnace filter. So we think that is more or less what it is, a dense plastic fiber mesh. Note that this material can be seen around the port hole in the upper left and upper right corners of the square that holds that circular bit.

Did the 2 hour discharge yesterday on the fully charged battery (12.94V, so a little surface charge still on it), exactly 5Ah out, and after 2 hours VOC was 12.70V (and had been flat for an hour). Capacity? Good question. Many AGM SOC tables put 12.70V at 100%, others have it between 90% (12.75V) and 80% (12.50V). We can't use 100%, as that would give infinite capacity. Assume a line between those points and it comes out to:

SOC = 40*V - 420 ; {12.5<= V <= 12.75}

Plug in 12.7 to get SOC=88%. Total capacity would be 5Ah * 100/12 = 42 Ah. Very approximately. Probably yet another 45 Ah battery. Makes sense, the plate geometry does not have a lot of wiggle room given the case geometry, at least if the long axis of the battery is perpendicular to the plane of each plate, and the capacity is proportional to the plate area.

The battery does test bizarrely high though with the HF "Viking" tester. After this discharge,recharge, and sitting overnight it read:

SOH 100%, SOC 100%, Ah 100, 13.01 V, 4.12 mOhms (more than twice the Ah of any other S46B24R)
SOH 100%, SOC 100%, CCA 728, 13.01 V, 4.12 mOhms (in CCA mode, 75% higher than the sticker)

The new battery recovers much faster than the old one. Will plot the discharge/recovery curve and post it later.

Technical note. While it is "quick" to discharge 5Ah at 2.5A in 2 hours, recharging takes considerably longer. The BatteryMinder 1500 puts out a maximum current of 1.5A, so one might think, "5/1.5, it will take 3.3 hours". Nope. The bulk charging phase is relatively quick and that took 2.5 hours, but the absorption phase was only down to .37A after 6 hours and had not completed (as far as the charger was concerned). I didn't want to stay up any longer (it was 23:30) at that point and unplugged it, but I estimate it was going to finish at 6.5 or 7 hours. Oddly, charging faster during bulk doesn't necessarily decrease the total time significantly. See the two traces for .2C and .4C about 80% of the way down the page here:

How Fast Can an AGM Battery be Charged? - Marine How To