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Prius II 12v Battery question.


cybervic
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Hi everyone, Prius Newbie here. I have just bought a Prius 2 last week, 2007 model, has FSH with Toyota and was last serviced Nov/2016 at 82500 miles. 

 
There is no record of any 12v Battery replacement and when I check out diagnosis menu, Battery voltage reads 9.3v (I assume accessory mode is when I power it on without foot brake?). In my previous cars, any Battery that reads below 10v would have all sort of problems so I’m rather confused if I am getting the right reading. The car drives well, no warning sign, goes to READY mode straight after hitting Power button. 
 
so my questions are:
 
1. is it possible for a 12v battery to last 10 years (currently 86000 miles)?
2. Can I measure the voltage on +ve and -ve terminal like any other car battery using multimeter?
3. I have turned off audio, light, aircon and dash cam, Is there any other things I should turned of to get a correct reading?
4. Is there any other warning sign I should look out for 12v battery failure?
 
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2 hours ago, cybervic said:
Hi everyone, Prius Newbie here. I have just bought a Prius 2 last week, 2007 model, has FSH with Toyota and was last serviced Nov/2016 at 82500 miles. 

  There is no record of any 12v battery replacement and when I check out diagnosis menu, Battery voltage reads 9.3v (I assume accessory mode is when I power it on without foot brake?). In my previous cars, any battery that reads below 10v would have all sort of problems so I’m rather confused if I am getting the right reading. The car drives well, no warning sign, goes to READY mode straight after hitting Power button.    so my questions are:   1. is it possible for a 12v battery to last 10 years (currently 86000 miles)? 2. Can I measure the voltage on +ve and -ve terminal like any other car battery using multimeter? 3. I have turned off audio, light, aircon and dash cam, Is there any other things I should turned of to get a correct reading? 4. Is there any other warning sign I should look out for 12v battery failure?  

 

These batteries could well last longer than normal. 9.3 volts is low, the Battery might just need a recharge via a Battery charger. As the charge rate is low and it would take too long to recharge it while driving.

 

I did accidentally drained my Battery, after using a battery charger, it hasn't given me any problems.

I connected a jump starter to the terminals while I removed the battery to avoid resetting anything.

 

 

Sent from my iPhone using Tapatalk

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Hi Vicky,

Before I recently bought my Gen4 Prius, I had a  Gen3 T-Spirit for the best part of 7 years. During that time I never changed the 12v Battery nor did I have any problem with it whatsoever. If I remember right you can't even top up the Battery with distilled water since it's sealed. Whether or not the garage check the Battery or even somehow top it up on service I've no idea but it never gave me any problems. As Anthony mentioned It might be worth charging it up using a battery charger. You could then  check it after a couple of weeks & if the voltage drops below 10volts have the car checked out in case there's a charging fault, otherwise consider a replacement if only for peace of mind. 

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As others have said, the Prius 12V Battery can last a long time if well looked after and not flattened much.  I had a 2002 Gen 1 Prius where the 12V lasted over 9 years and 160,000 miles.  However, there are also many reports of these batteries failing early.

Since in the Hybrid system the 12V Battery doesn't have to crank the engine (the HV Battery does that), it is not very strong, and can be easily flattened by a single light (boot, interior) being left on - doing this a few times, or leaving it very flat for several days will ensure early demise.

Obviously, if the 12V battery repeatedly drops to a low voltage, then unless there is an electrical fault (rare), it need replacing.  Other telltale signs are warning lights or messages about brake problems, or needing to park on level ground can point to 12V battery problems.  Otherwise, it's probably ok.

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Thank you all,

I have tested jump terminal directly and it reads 9.8v this morning (yesterday 9.3v). I've been looking out for warning signs at front Dash but still nothing. I do worry if it will just died suddenly. I'm thinking to buy a charger/jump starter, Any recommendation?

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Thank you all,

I have tested jump terminal directly and it reads 9.8v this morning (yesterday 9.3v). I've been looking out for warning signs at front Dash but still nothing. I do worry if it will just died suddenly. I'm thinking to buy a charger/jump starter, Any recommendation?

 

Most of the modern ones are intelligent ;-)

A 4 amp one will do the trick. I use a cheap one from Lidl, as recommended by a few people on here. Probably best getting one online, as the likes of Halfords will sell you one that's either too powerful or over priced.

 

I'm sure you can one for about 20 quid.

 

 

Sent from my iPhone using Tapatalk

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