Some measurements on 12V battery

If you're nervous about your battery, get one of the various battery jumper packs and carry it along. Here's an example:
http://www.amazon.com/dp/product/B000XQ9MGE?tag=priuschatcom-20 Prius startup currents are very light compared to other cars since the battery just boots the computers etc. and doesn't have to turn over the engine, the smaller jumper packs will easily do the job.

 

The original equipment battery is supposed to be AGM. If your battery had fuzzy white mats separating the lead plates, it is AGM. Otherwise it is of traditional design.

If the battery is AGM, a few ounces of distilled water in each cell might provide a temporary rejuvenating effect. If of traditional design, then of course it is necessary to keep the plates covered using distilled water.

 

My experience of these batteries is similar to that of David Beale - and thanks David for your interesting and informative posts.
My car is nearly four years old (mine for the last 18 months), and I had read that the 12 volt battery was perceived to be a weak point in the Prius. I decided to take the battery out of the car for charging, where I could set my smart charger to a higher maximum voltage than that used by the Prius system.

Apart from the warning labels on the top, there are no other labels on my battery and I couldn't find any indication of manufacturer.
At this point I decided to have a look inside. I found that two of the inner cells had electrolyte above the plates, the remaining cells appeared very low, and I could see the matting between cells. The plates are spaced further apart than in any 'cranking' starter batteries that I have seen, and there are fewer plates per cell. I made the decision to add water to the low cells before charging, after which the battery was replaced in the car and is performing well. I don't have a 'drop tester' so I couldn't measure the capacity before and after.

In retrospect I don't know whether adding this much water (to cover the plates) was the best action. The cells with electrolyte above the plates may have been overfilled at the factory - this seems most unlikely, but there was no evidence of the battery having been opened up before.

If I were to do this again perhaps it would be better to add water to just below the top of the mats. This would minimise any accidental spillage which is an advantage of the AGM construction.

I would be interested to hear other users' views about this.

Clive

 

The dark brown colour of the plates is a good sign as the Lead Dioxide aka Plumbic Oxide from my high scool chemistry classes, is what is needed on the grid plates for the Lead Acid battery to work.

If they were greyish Lead Sulphate the battery would definately be on its last electrons or positron....plates.

 

A reasonable conclusion.

The New Car Features manual makes a point that the 12V battery is AGM and that a battery of traditional design should not be used.

Who knows why Yuasa GS shipped AGM and non-AGM batteries that had the same exterior appearance...

I opened up the original equipment battery on my 2001 and it had the white fluffy mats separating the plates and no free liquid inside. Although I did not open up the original equipment batteries on my 2004 and 2007 when replacing them, I did shake them and did not hear any liquid inside.

 

The water portion of the sulpuric acid electrolyte that is used could have been removed by electrolysis (maybe at some impurity points on the plates) hence the need for vent tube. This leaves much stronger acid now only partially covering the plates hence the drop off of capacity.
The electrolysis products of Hydrogen and Oxygen are not safe to have around especially in closed spaces with arcing relays.........BOOM. A company I used to work for lost a $100,000 system to such an event, thankfully no one was around when the 100lb doors were tossed 50ft.

From a practice standpoint you are supposed to add water to bring the SG up to a recomended spec. Alternatively you could remove all the used acid and add fresh acid of the rquisite Specific Gravity being carefull not to blind yourself or burn off you fingers and toes.

Wanting to keep my body parts a little longer as I am still kicking I would be inclined to to buy a battery from Toyota, look around you should be able to get one for around $150USD.

 

I just was able to remove and work on my battery thanks to you! W/some help, we removed the battery, and it took 2 cups (!) total distilled water. So far so good. Muchimas gracias!
We found a few things different on my 07 prius.. the vent tube wouldn't come away from the side of the car, but we held it up to get the battery out.

 

Clive, since you are in England, you may be interested to know that Optima sells a drop-in replacement in Europe, YTS 2.7J. It is a true deep cycle AGM battery -- it can go flat and be recharged many times, as opposed to whichever OEM battery is in your car right now.

http://priuschat.com/forums/gen-ii-...placement-optima-battery-available-in-uk.html

 

I have been suspecting the 12V battery on my car being weak ever since I bought the car new. I tried BatteryMinder a few months ago without much effect. Today I finally got some time to take the battery out to look and add water. I was thinking of doing it in situ but it just looked very difficult if not impossible. It helps to have the experience of taking apart the carpeted panels from last time when I did the mouse proofing of the vents.

I found it easier to disconnect the three connectors on the positive side and then disconnect the negative cable from the body. I didn't have to touch the nuts on the battery posts until after the battery was taken out of the car. In other words the battery is lifted out of the car with the negative cable and positive connection block (including the battery hold down bar) still firmly connected. The 12V vent tube on my car is tight and does not pull out easily. I used a taped flat blade screw driver to pry and push from the end of the tube to push it out. I left the battery hold down bar in place and just rotate the entire positive connection block 90 degrees once the battery is out of the car.

The big surprise for me was that once the label is removed there was liquid oozing out of the edge of the transparent plastic cover. Once the cover is pried open it was also wet inside. The rubber caps were not tight at all. I suppose some acid does spill out of the vent holes? Two out of the six vent holes gave gas venting sound when the rubber cap was removed.

I bought eye droppers with the distilled water in local drug store. The eye dropper is a little bit too small and it got somewhat tedious going back and forth between the water jug and the battery.

Wish I had such a machine.

I used a 12V lantern battery (http://www.amazon.com/Rayovac-926-Lantern-Battery-General/dp/B000ROFZFE) as backup. It started out at 12.8V with nothing connected. Connecting to the car it dropped down to 11 something. Right before reconnecting the 12V battery back it was merely 8 something. I thought it was $12 wasted but found at least the radio stations are still remembered. I haven't tried to start the car yet. Now the lantern battery reads 11 something with nothing connected.

Mine says 4.2 A.

I had one cell that had liquid above the mats. All others had mats sticking out in the air. I decided to add distilled water to just cover up the mats - it's really hard to see where the plates end.

Without sophisticated equipment I just put the battery back in and hooked up the BatteryMinder and hope for the best.

I had one cell that had liquid level above the mats. The other 5 cells all had the mats sticking out in the air.

The top of the plate was hard to see (maybe I didn't know what to look for). I ended up adding water to just cover the mats - the level was still a bit lower than the one cell that had liquid level above the mats originally. I also had the same thought that what if the factory fill level was uneven to start with?

The color of the plate above the liquid is silver-gray. It's hard to see what color it is below the liquid level since the mat is in the way.

I will look at the BatteryMinder voltage and update here.

Update: The charging voltage from the BatteryMinder went from 12 something to 13 something. I only looked at the voltage once in a while so I don't know if it ever reached 14V or not. About 6 or 8 hours later the green LED started flashing - signaling the "patented pulsing" maintenance mode. The voltage shows 13.3 something and gradually moved up to 13.4 something overnight. If a door is opened then the voltage would drop back down to 12 something and it will take some minutes to go back to maintenance mode.

 

After adding water and running BatteryMinder for 4 days, I did a battery check with a Fluke DMM, ScanGaugeII, and PriiDash (IG-ON only). The final maintenance voltage was 13.49 (from DMM). Disconnecting the BatteryMinder brought the voltage down to 12.9V. Unlocking and opening the door brought it down further. The following data were taken when I was sitting in the car:

	12V battery check
1	IG	DMM	SGII	PriiDash
2	OFF	12.50	12.4	---
3	OFF	12.48	12.3	---
4	OFF	12.54	12.4	---
5	ACC	12.22	12.0	---
6	ACC	12.20	12.1	---
7	ON	11.89	11.7	11.74
8	Head Light	11.57	11.4	11.43
9	Rear Def + Head Light	11.13	10.8	11.00

A few minutes after turning everything off, and while still sitting in the car, I saw the voltage climbed back up to 12.60V on the DMM.

It looks like the SGII and PriiDash read about 0.1 ~ 0.2V lower than the DMM, except when under heavy load the SGII read 0.3V lower. The DMM was connected to the jump points under the hood. (Earlier before adding water I measured at the battery posts and the jump points and they read identical 12.12V with no load.) PriiDash got the voltage from OBD query. SGII is probably using a internal A/D converter since it works even when the car is off.

These numbers are not very different from what I measured before adding water. It is thus inconclusive at best whether adding water has any effect in this case.

 

Me filling the battery doesn't warrant an own thread, but I'll add some pics that might be useful:

Battery voltage (double check, the display also gave 12.1 - 12.2).


This is what my (presumably original, less than 3 year old) battery looks like after peeling off the sticker saying you should NOT fill the battery. Please note the water next to the battery is from rinsing it off with (demineralised) water to remove sand/dust. Also note the safety glasses: use them. You're going to squirt water into quite concentrated sulphuric acid!!!



One flooded cell and one not quite flooded cell, try to figure out which is which. Whether this is AGM or not, I'll leave to the experts.



Best way I could think off to match the waterlevels: a flashlight behind the battery and looking at the other side. I matched them all to the highest one by adding demineralised water. Only had 150 ml or so before having to open a new bottle, but managed all cells with this amount, so it wasn't that much that I added.






EDIT: maybe I should have just left well enough alone... Wife just called she couldn't open the Prius and during me explaining the key sliding out the remote-control, she said: ooh, s***, I left the lights on (she usually takes the Volvo with lights that are on as long as the key's in the ON position... so you never think about lights in the Volvo.)
Guess the battery will have taken a severe beating once again... Also per phone explained how to hook up the starting-cables (she couldn't get the boot open to get at the cables and my tiny 14.4V emergency lithium battery didn't cut it). Still to hear if she succeeded.

 

Did you actually take the entire top cover off to wash it? My 12V battery doesn't have translucent container. It's all black.

 

No, I washed it as it is in the pic (before removing the strip of acrylic (?) plastic that's next to it on the right).
So your battery is black??? Production year difference? EU vs USA difference? My battery not original? I have no explanation...