Question re: 12-volt battery, please?

Yes.

Actually, since the Optima website recommends charging current up to 10A, if you are in a hurry you can select the 6A setting.

It sounds like you already know how to open the lid of the main relay/fuse box. If not: the trick is to press hard on the latch at the front of the lid, then pivot the lid up and remove it.

The dedicated positive jumpstart terminal is hiding under the red plastic cover. The cover is hinged and has a latch that can be released, then the red cover can swing open.

 

Yes, a nut that secures the front left strut mount is the perfect spot and happens to be the one I use.

 

Not much room under the hood, but it is worth a try anyway. Are you worried about your charger being lifted. Leave the charger inside the garage and fish the cables under the door to the connection points. Good luck, H

 

A couple of hours may not be sufficient, but you'll see what is needed. If you are attaching the charger cables to bare metal then you should be good.

If you can't trust the charger to know whether it is connected to the battery, how can you trust its indications regarding % charge?

If you don't like that charger, perhaps you can return it?

 

Ok those readings seem very similar to what dhanson was getting immediately after charging his new Optima. You have to take into account that the MFD readings you get when it's installed in the car are lower than what you would get if the battery was completely disconnected. There's a small but constant current drain once it's installed in the car, and there's a few amps being drawn even when you're only in accessory mode.

When I had my (old OEM) battery out for service last year it was 12.5 volts on the bench, but only measured 12.2 (acc mode) the moment I put it back in the vehicle.

In the data dhanson provided, his optima was 12.9 volts (on the bench) after charging but only 12.5 (acc mode measured) after he installed it.

My guess is that after you're had the battery in there for a couple of weeks of (your) normal driving it will be back down to to something like 12.3(acc) 12.0(ig).

 

If you want to compare your battery against this spec, you need to disconnect the negative battery cable where it bolts to the body, so that the Prius electronics are not loading down the battery. Then fully charge the battery.

After the battery has charged, leave it alone for an 8 hour period to allow surface charge to dissipate. Then measure the battery voltage and compare to the 13.0V-13.2V spec.

 

I just pulled my old 12 volt out of the prius put my meter on it and it is less than 10 volts, shows 9.87 on digital and on my analog meter shows just above the 10 vold dc scale, glad i ordered a new battery it is due in today

 

Interesting. Can you tell us if your Prius had been misbehaving with the voltage so low, I would have thought so. One member here who monitored his declining battery said that there was no particular problems until it fell well below 11 volts (I think it was somewhere about 10.5 volts that really anomalous behavior developed).

 

mileage has dropped to 39.5 mpg but I figured it was because of the heat and the ac on all the time, then the red triangle would come up then go away just as fast as it was on. Noticed the hybrid battery discharging faster than normal, but then again blamed it on the heat and having ac on always, then just the otherday had the wipers on went to start up the car they went really slow and the red triangle came back on and stayed on till I pressed the power button then retried starting and everything was good. and the thing that was happening first but had no idea was the alarm tone would come on after we shut thw car off and then go away when the door was closed, so maybe since the door was open and the lights were on it was saying ...hey I am too low on current shut the damn door lol thats about it, I have the old out waiting for the new to arrive today

 

wipers were going slow and red triangle came up | PriusChat

Ok, to answer my own question I just looked up you other posts. So the battery dropped right down to 10V (probably lower when it was in the car) and all you got was "slow wipers" and a warning light. You didn't even get stranded or need a jump. Wow, pretty lucky.

It does confirm my previous position on Julia's case that she could have just given her existing battery a charge and keep using it. Probably for another year or more, particularly now she knew how to monitor it.

 

Sorry I replied before I read this. Ok so you did notice some MPG drop, that's the main thing I was wondering about. Thanks for the info.

BTW. You'll have to let us all know if the MPG improves now that you've got the new battery.

 

Just for grins, reconnect your battery charger, set it at 4 amps and let it charge for 24 hours. Then let it sit for 8 hours. After that check the voltage at the connection under the hood with your multimeter. If you do not read 12.6 volts or higher, then the battery is probably sulfated and probably should be replaced under warranty.

FWIW, I recharged my 3+ year old OEM battery with the Battery Mender/Desulfator and after 24 hours, I found voltage's considerably higher than what you are reporting. I too connected my charger like you did, using the jump terminal under the hood for the positive side and the strut nut for the negative side.

12.2 (ACC) and 11.9 (Ig-On) is telling me without a doubt either your battery is still not completely charged OR your battery is defective. You won't know for sure without a 24 hour charge. That type of charge should be more than sufficient to fully charge your battery unless it is sulfated.

The only other thing it could be to cause your battery to discharge quickly is a short somewhere in the system that would be pulling down the voltage or something left on inside the Prius (light, etc.). The Prius does have parasitic voltage draw when it is sitting idle, however the battery should not discharge down to 60 - 70 % in just a few hours. At 12.2 Volts, your battery is between 60 and 70 % charged.

One last thing, if you truly think your battery is bad, bench test it by charging it out of the car for the time I stated and then test the voltage again. If it reads low, then the battery is definitely defective. If it reads good, then the problem is definitely not the battery. It could be something simple like a bad connection (dirty post's or something similar).

I am basing this post with the assumption (bad to assume) that your charger is working properly and is a "smart" charger. I do not want to knock your charger or the choice thereof, but all things need to be considered at this point.

I am sorry to hear you are having bad luck. I had hoped to hear your problems were solved.

 

Not sure about 2nd gen 12 volt battery layout, but regarding the negative connection, that can be any bare metal of the body or engine. Don't pick some extremely flimsy bracket which may or may not be properly grounded, but other than that, most any bare metal will do. Basically, the car body is part of the circuit.