Checking water level in battery

Batteries have been maintenance free for a very very very long time now... Where have you been?!

 

Maintenance resistant is more like it. You can peel off the top sticker on the GS battery and you can add distilled water to it. It's not what the manufacturer intended, but the stock Gen 2 battery is famous for its early death.

To answer the OP's question, the original GS battery in the Prius is not an AGM, it's a flooded, maintenance-free lead-acid battery.

 

FWIW, both the OEM batteries in my 02 Nissan Maxima and 04 350Z required you to add water, if low.

Even the '11 Nissan Leaf's manual (on page 8-12) refers to adding fluid but I'm not clear if all of them ship w/ones w/removable vent caps and the ability to add water, as pictured in the manual. My Nissan Leaf Forum • View topic - Nissan Engineering Team Visit Dec. 3rd: Recap in the lower pic sure looks like it has removable caps, just like in the manual.

 

Right. If the water level is low, the battery will die and they'll get to sell you a new one.

It's not clear how high the level should be, but it would certainly be safe to add enough to bring them all up to the highest one. Maybe you'll get an extra year out of the battery by keeping the plates wet.

 

Hi Ernie,

It may have been my post you saw.

Yes, the label says never to add water, but as someone mentioned, it's more of an attempt to sell more batteries and to prevent liability issues. As long as you keep the battery upright and don't overfill it, it's pretty tough to get acid on yourself though.

Remove the intimidating warning label and place it upside down to reduce its intimidation factor (and keep the adhesive clean).

Then you'll see a transparent plastic strip covering the 6 cell fill caps. Carefully pry out the plastic strip with a flat-bladed screw driver or putty knife and set it aside. Then remove the small rubber caps but be careful not to lose them--they like to fly/roll.

The holes are pretty small, but with a flashlight, you should be able to see the whitish-colored plates inside. They were not submerged in the electrolyte when I had my battery out. Add enough distilled water to each cell to cover the plates inside (about 1/4" above the plates--don't fill the cells all the way!).

Then put the rubber cell plugs back on, press the clear strip back into place and replace the warning label. Put the battery on a slow, smart charger for a while if you can.

Adding water has really helped my original battery. I put it on a 1-amp smart charger for about 36 hours after I added water. Then the car sat for a week and then booted just fine the next time I drove it. No red-triangle light like I used to see. I think I can keep using the original battery a good while longer.

I used to leave "maintenance free" batteries alone and just replace them, but once you start pulling vent plugs, you never go back! I added water to the "maintenance free" deep cycle battery in the pop-up camper as well.

Eric

 

Hi Eric. Is it easy enough to check the water in the battery while it's in the car, do you have to remove it first?

 

uart--you can try it without removing it but I think it would be easier in the long run to remove it. You have to look practically straight down into the vent holes to see the water level and with the battery out, you don't need to worry about spilling water in the car interior. I would predict a sore back and neck from leaning over the trunk and trying to access and see into the vent holes.

 

Agree with Tanglefoot in all respects. I think the Engineers at Toyota decided that the 12V Bat would be the sacrificial lamb when it comes to conserving voltage from the main bat. It seems to be current limiting. I have never been able to charge the OEM battery to 14 Volts, either on the car or on the bench. Possibly if left on charger for months it may go up there. I think the term Flooded AGM may be more accurate. Anyway both car and battery are somewhat deficient when it comes to 12 Volts. I recommend a separate charge every 6 months

 

You would think so. But not in Porsches! I had an 03 Boxster where you had to add water to the battery, and the dealer replacement was the same. I said screw that, and bought a maintenance free replacement at
one of the chain stores.

 

Only if it turns into a capacitor :_> 14V is within the range of charging voltages for a lead-acid battery. If you measure 14V on a lead-acid battery that is not being charged there's something wrong with the measurement.

 

Just posted my water adding experience in this earlier thread:
http://priuschat.com/forums/gen-ii-...e-measurements-12v-battery-4.html#post1441570