Dead 2009 Prius 12 volt battery followup question

Nice try,but it's toast.

steve

 

Did the battery die from having a light left on inside the interior? If that is the case, you may still be able to recover that battery by charging it. The numbers you posted don't look too bad, just seems you need to charge it longer. Charge it for another day using the same method and see if the numbers are better. Keep in mind the numbers you see on the MFD screen may not be that accurate, showing lower than it actually is. The most accurate way to get a proper reading is at the battery terminals.

 

The 2009 battery shouldn't be in tip top condition, it is about 5 years old. You could play it safe by replacing it. But as you said you don't want to replace it just yet, so charge it for another day and use it as is. I think it should be fine after you charge it again.

Although the MFD reading is not totally accurate, it's better than not having anything. Most people would use that as their indicator, taking a reading at the battery terminal is just an extra step to get a more accurate reading.

 

You can get a digital multimeter and measure it at the battery terminals. You don't have to disconnect anything.

 

Can you just use the "jump point" and a ground under the hood, instead of the actual terminals....?

Or is that not as accurate?

 

IIRC, when I compared measurements taken at the jump point with that at the terminals, they matched. The ScanGauge II shows about 0.2V less than that at the terminals on my Gen3.

 

I would turn off the Smart key (under the steering wheel) and alternate the battery tender. That should be sufficient.

 

Disconnecting the negative terminal and placing them on a battery tender for AGM batteries alternately, should leave them in good condition. The issue with leaving the negative terminal connected is that the car will continue to drain particularly if it has got the Smart Key System (SKS). You would want to leave the positive connected.

 

There are actually more than one way to approach this.

The easiest way would be to simply turn off the SKS on the car or cars that is NOT being driven.
Use the battery tender on each car that is NOT being driven every day, alternating between the vehicles.

If you had the money, the smart thing to do would be to invest in a BatteryMinder 12248 or a good ctek charger. You really should be using a charger that is designed for AGM type batteries.

I do realize you are trying NOT to replace your batteries at this time, however you need to understand that your battery or batteries will not last forever. In reference to the one you described in post #1, more than likely that battery is sulfated and will probably be very difficult to get it to fully recharge. It could possibly be desulfated, but it would take a lot of time and a lot of charging to break up all the sulfate that is on the plates.

Depending on your climate, you may find that the battery you described in post #1 will fail (need a jump start) very soon or possibly several months from now. I would not expect this particular battery to make it through a cold winter without the need of a jump start at some point unless you are charging the battery on a regular basis.

In reference to the 05 that is NOT insured and NOT being driven. If you are not going to drive the car, it would be a good idea to air up all four tires to maximum inflation and raise all four wheels off of the ground and place the car on jackstands. This will eliminate any chance of your tires getting flat spots on them. I would make sure the traction battery (big battery) is charged to at least 6 bars before putting the car up on the jackstands. I would also recommend that you change the oil in the engine along with the filter before putting the car up on the jackstands. I would also include the rotation of the battery tender on this vehicle along with the rest as describe above. I would not store the car in this condition for longer than 90 days before I put the car back on the road and drove it.

The Prius is one of those cars that really likes to be driven and not sit for long periods of time. Normally the dealers will disconnect the 12 volt battery and then charge the battery before delivery. Most of the time when they are sitting on the lots, the 12 volt will be disconnected.

Remember, there are more than one solution to your situation. I described one way. I have no doubt other's will say different things.

I hope this clears up any confusion and gives you an idea of how to work with your situation. Best of luck to you!

 

Without knowing the details of the particular charger you mention, I would say that if the tender is designed to maintain a 12v battery, then it should be safe to leave attached. However, you should consult the user manual (try to find online if you can't find it -google is your friend) and it should become clear how you should use the tender.

 

You would be better off if you had a charger for each car, but it will not hurt anything to move the tender from one car to another on a rotating basis. The idea is to keep the batteries charged as much as possible. A battery tender like what you have is not going to over charge or cook the battery. If anything, it won't be enough juice, but should be enough to keep a fairly healthy battery going. A weak or dying battery, then a 2 amp tender might not be strong enough. IIRC, Patrick Wong mentioned that to you in another string.

IMO, you really need a good AGM type battery charger that will charge and maintain with a 4 amp setting. That is ideal for the Prius. But if you are on a budget, you work with what you have until you can afford better.