Some measurements on 12V battery

OK maybe it is the angle of the camera that gave me the illusion that it was only the top cover (as opposed to the entire battery) that's showing in the picture.

 

OK, now I see what you're getting at. It's the angle of the camera: it's the entire battery with the rubber caps still on (and sucked a little vacuum).

 

Did you find all of the caps maintained vacuum? I found my caps quite loose and only two of them held vacuum.

 

The GS Yuasa translucent case battery has a smaller capacity as compared to the black case battery. The latter is used on Smart Entry / Smart Start-equipped vehicles.

 

Which mine doesn't have, so that makes sense

As for the caps being vacuum: depending on state of charge the chambers within a battery can have an over or underpressure. Or at least I remember reading something like this somewhere. In other words: don't worry. If really going deep into the matter, their bulging or dipping might give a hint as to what state one cell is compared to the other, but mine were all 'vacuum' regardless of the fact some had a 'water'-level under and some over the plates.

 

When I pulled the caps off my battery a few days ago some of the cells felt like they had a bit of a vacuum and some didn't. The clear plastic plate that fits over the caps is fairly snug to the top of the caps, so it should prevent any caps popping off if there is a slight over pressure.

BTW. My battery was fully opaque black despite my Prius being non SKS. That may be a regional difference though (Australian model).

 

Just updated the battery test data in this earlier post:
http://priuschat.com/forums/gen-ii-...e-measurements-12v-battery-4.html#post1444163

It would be nice if more data is posted so we can compare.

 

Thank for the info David. I was wondering where the vent pipe connected to. I just had it (the battery) out a few days ago but didn't look closely enough to notice that.

 

My guess is that if there was a significant amount of dried out mat to begin with, then adding water could have improved things by decreasing the battery's internal resistance. If however there wasn't any dried out mat then adding water would just dilute the acid and could slightly reduce the batteries performance.

A slight dilution of the acid is not necessarily a problem. When electrolyte is lost from a battery it's usually through bubbling off of hydrogen and oxygen gas, so really only water is lost and the acid gets more concentrated. When you add back the water it's ideally just bringing the acid back to it's original concentration. If you added back too much water (like perhaps I did) then you could end up with a lower concentration than the original specifications. This could slightly decrease the battery's performance, but I doubt it would be very significant.

 

I solved the battery drain problem by disconnecting the door and hatch light, I do not use the courtesy light at all. ie: no more 12 V problems. :

 

I can confirm this really works. I recently bought a 2007 with a battery that couldn't keep a charge. Car has 283,000 kms and it might be the original battery for all I know. Did exactly what OP said to do with battery and the Prius has been starting fine when before it needed a boost anytime it had been sitting for I think half a day or more. When I opened up the 6 tubes, I could see no evidence of water. Pretty amazing that it seems to have been fully restored by 97 cents for a bottle of distilled water!

 

I have a 2005 prius and I have replaced the battery with 4 6 volt NIMH modules from a Ford escape hybrid.
I configured the battery as 2parallel and 2 serial. Each module is 5 NIMH D cells at 5.5AH. So I have a 12 Volt 11AH NIMH battery.
I had to extend the wires and place the battery in the tire well area.
If I start the car regularly it all works fine. If it sits for a while, I have to charge the battery before driving.
This is mainly due to the self discharge of the NIMH and some load from the Prius.
If I was to put a .5 amp trickle charger on it I would not need to worry about sitting for a while(still on the list to do).
I try to not use lead acid technology if I can.
Oh and the NIMH cells are from a 2005 ford escape. Still providing a full 5.5 AH each.