How do you know if your (12V) battery is on its last legs?
#31
Re: How do you know if your (12V) battery is on its last legs?
I took a bench power supply I have and clipped it to the old battery. Then I lowered the voltage until the current was zero (matching the old battery voltage). Since the car was in use all morning (charging the battery), the then resting voltage was 12.1. I unclamped the terminals from the battery, with the power supply clips still on the car cables (and the power supply current jumped to around 100 ma). Then I attached the cables to the new battery. Not sure exactly when, but before I had both cables on the new battery, one of the power supply leads fell off! Oh, well.
-- Alan
-- Alan
#32
Re: How do you know if your (12V) battery is on its last legs?
Yesterday evening I went to start the car and the battery was pretty low. The car tried to come on, but after a point the info display in the gauge cluster start going on and off and saying to check the VSC system when it would come on. Some of the other lights flashed too.
I put it on low power charge on the charger for a couple of hours and the car started after that, then I drove the car to let the car's onboard system charge the 12 volt some more.
I'm replacing it with an Optima tomorrow. I'll report back how it goes. I don't anticipate too much difficulty.
#33
Re: How do you know if your (12V) battery is on its last legs?
I forget if the 12 volt battery in the trunk has side or top terminals. I was thinking cleaning the terminals might help the low voltage if they are on top. Another way to read if the battery is low, is to turn on the headlights for 10 to 15 minutes (engine off), then measure the dc voltage across the battery while they are still on.
The new Optima will sure cure your battery problems.
The new Optima will sure cure your battery problems.
Last edited by rburt07; 05-27-2012 at 11:46 PM.
#34
Re: How do you know if your (12V) battery is on its last legs?
FYI, from dealnews.com:
For in-store pickup only and with limited availability, Advance Auto Parts offers the Optima YellowTop 12-volt AGM Car Battery for Toyota Prius, model no. DS46B24R, for $124.99 via the directions below. That's $1 under our mention from six weeks ago (which included free shipping) and the lowest total price we could find by $40. Sales tax is added where applicable. Rebate expires May 31. To get this deal:
Add the Optima YellowTop AGM Car Battery to your cart for $199.99
apply coupon code "VISA" to cut it to $149.99
redeem this $25 rebate for a net price of $124.99
Brand: Optima
Model Number: DS46B24R
For in-store pickup only and with limited availability, Advance Auto Parts offers the Optima YellowTop 12-volt AGM Car Battery for Toyota Prius, model no. DS46B24R, for $124.99 via the directions below. That's $1 under our mention from six weeks ago (which included free shipping) and the lowest total price we could find by $40. Sales tax is added where applicable. Rebate expires May 31. To get this deal:
Add the Optima YellowTop AGM Car Battery to your cart for $199.99
apply coupon code "VISA" to cut it to $149.99
redeem this $25 rebate for a net price of $124.99
Brand: Optima
Model Number: DS46B24R
#35
Re: How do you know if your (12V) battery is on its last legs?
I'll admit I haven't read all the threads on the 12V battery, nor really understand much about what it does, but, in a regular car, you can tell when your battery is going as the starter is sluggish, etc. You usually can tell (depending on the weather) when you're within a week or two of when it will die.
In the hybrid, (again, I'm not sure what the 12V battery does) are there any tell tale signs that the battery is dying? Does it have the same expected life as a regular car's battery (or is it longer as it doesn't need to turn over the engine to start)?
Thanks!
In the hybrid, (again, I'm not sure what the 12V battery does) are there any tell tale signs that the battery is dying? Does it have the same expected life as a regular car's battery (or is it longer as it doesn't need to turn over the engine to start)?
Thanks!
12.6 -12.8 V Fully charged
12.2 -12.4 V Half charged
11.8 -12.0 V Discharged
(*: Voltage checked 20 minutes after the engine and all the lights are turned off, at 68 deg. F)
It would seem to me if you were consistently getting Half Charged range when you test with a multimeter, I would start to get concerned. If you then check voltage when the car is running and hopefully charging, I would expect it to be up around 14-14.5 volts. If it does not come up to that, then you can suspect the charging system.
Another way to evaluate the state of a lead acid battery if it has removable cell caps is to measure the specific gravity with a battery hydrometer. They are relatively cheap. If you have a suspect battery, you can confirm it by testing each cell to see how uniform they are. Often you will find one cell is lower than the rest. The only trick of this test is making sure you don't get any acid on your car, hands, or clothes!
On buying a replacement, cranking amps or CCA is irrelevant as this battery is not used for starting. Buying a deep cycle seems to make a bit of sense as there does seem to be a drain on these batteries when the car is not running. Generally you can tell the capacity of a battery for deep cycle by the amp-hour rating, or the reserve minutes. More is better.
Consumer Reports I recall used to test Optima and recommend them, but in the latest tests they do not seem to be included. DieHard Gold and Platinum seems to test near the top in most sizes.
Does the original battery have a vent connection? Venting of the hydrogen and oxygen would seem to be a bit of a concern as it is located in the trunk rather than under the hood where there is lots of ventilation.
Last edited by Ron AKA; 06-03-2012 at 11:42 AM.
#36
Re: How do you know if your (12V) battery is on its last legs?
I'll admit I haven't read all the threads on the 12V battery, nor really understand much about what it does, but, in a regular car, you can tell when your battery is going as the starter is sluggish, etc. You usually can tell (depending on the weather) when you're within a week or two of when it will die.
In the hybrid, (again, I'm not sure what the 12V battery does) are there any tell tale signs that the battery is dying? Does it have the same expected life as a regular car's battery (or is it longer as it doesn't need to turn over the engine to start)?
Thanks!
In the hybrid, (again, I'm not sure what the 12V battery does) are there any tell tale signs that the battery is dying? Does it have the same expected life as a regular car's battery (or is it longer as it doesn't need to turn over the engine to start)?
Thanks!
Expected life of a gel type should be good, unless it has been overcharged. They are more sensitive to charging voltage. That is probably why Toyota recommends no more than 5 amps for charging.
#37
Re: How do you know if your (12V) battery is on its last legs?
The 12 volt battery is the power source for everything in the car that uses 12 volts. Most important for starting would be that it powers the ECU. The ECU in turn connects the traction battery to start the engine, sometimes rolling the car to do so, only if you put it in drive or reverse quick enough.
Batteries are usually not usable if they are 10% below their rated voltage. That would be 10.8 volts for a 12 volt battery. If you can't get your car to start due to low illuminated instrument panel. Make sure everything is off, including closing the doors so the dome and map lights don't come on. Let the car sit for 3 to 5 minutes. Sometimes this makes enough difference to get the car started.
I think it was haroldo that long time back said, be sure the clock is black or not illuminated when you get out of the car. To turn if off, press the power button till the clock goes dark. I do this with my '12 TCH but also sometimes see the mid reminding me to turn the power off.
I understand the deep cycle 12 volt battery in the trunk is vented down and outside the trunk.
Batteries are usually not usable if they are 10% below their rated voltage. That would be 10.8 volts for a 12 volt battery. If you can't get your car to start due to low illuminated instrument panel. Make sure everything is off, including closing the doors so the dome and map lights don't come on. Let the car sit for 3 to 5 minutes. Sometimes this makes enough difference to get the car started.
I think it was haroldo that long time back said, be sure the clock is black or not illuminated when you get out of the car. To turn if off, press the power button till the clock goes dark. I do this with my '12 TCH but also sometimes see the mid reminding me to turn the power off.
I understand the deep cycle 12 volt battery in the trunk is vented down and outside the trunk.
#38
Re: How do you know if your (12V) battery is on its last legs?
I took a bench power supply I have and clipped it to the old battery. Then I lowered the voltage until the current was zero (matching the old battery voltage). Since the car was in use all morning (charging the battery), the then resting voltage was 12.1. I unclamped the terminals from the battery, with the power supply clips still on the car cables (and the power supply current jumped to around 100 ma). Then I attached the cables to the new battery. Not sure exactly when, but before I had both cables on the new battery, one of the power supply leads fell off! Oh, well.
-- Alan
-- Alan
#39
Re: How do you know if your (12V) battery is on its last legs?
Sorry to be waking this thread up, but I have been thinking I could connect the backup power cables to the points under the hood before changing out the battery. Does any one have any concerns with this approach, aside from having to be careful with the positive cable end in the trunk not touching any conducting material in between the battery change?
#40
Re: How do you know if your (12V) battery is on its last legs?
-- Alan