2010 Gen 3 Prius and 12V Battery Question

you should get a smart charger. the car isn't charging it up enough. a good battery will hold 2-3 weeks no problem.
if you charge it up, and it still won't hold while away, replace it. we go away every winter for 5-6 weeks with no issues.
all the best!

 

7 years is a good run for any 12v battery. personally, i would just replace it. but if you'd rather not, you can keep an eye on the voltage with a digital volt meter, checking under the hod every so often. as for a charger, i'll ask the expert, my good priuschat friend @Mendel Leisk he'll give you a link to a good one at a reasonable price.
a new battery should be fine on its own for a few weeks.

 

CTEK 3300 would be my pic. Or their 4.3, a bit more pricey. There's a lot of options, those are just two that have worked well for me. nothing wrong with the 3300, probably best cheaper charger.

 

I used the self diagnostic feature and this is what I got with engine off 11.3v but once I applied the brakes and tap the start button one more time to make the car ready I get 13.9v.
What u guys think?
2010 190k miles



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you need a new battery before it fails on you. it doesn't matter what it is when it's being charged, but 11.3 is practically dead. now, it might be a bit higher than that with a volt meter and everything off.

 

That signal check on the center display is handy, but it is several feet of skinny wire away from the battery itself, and on mine the reading is always a large fraction of a volt low compared to what the battery's got. That doesn't look dire to me.

-Chap

 

I get roughly the same readings at the jump point as directly at the battery. 11.3 volts at rest (if it is accurate, I don't really trust the car's reading, a digital volt meter would be better), is near dead, deceased, morte. It is an "ex" battery.

With thanks, from the "the 12 volt side of life":



The 12volt Side of Life (Part 1)

 

I will check using a multimeter in the morning
...I have noticed then when parked but in ready mode sometimes the car engine keeps running for ever even if the hybrid battery is full.... maybe related? Then it may be my impression but my headlights hid seems not as bright when driving at night and mpgs are down.

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That's the key. With your meter, at the jump point, you can measure voltage with no other loads (and your meter has an impedance probably in megohms, so it scarcely loads the circuit at all).

The only way to get a voltage reading at the dash display is to have it powered (ACC at least, which powers all the accessories, or even ON, which powers more). So that's not an 'at rest' reading. And that voltage measurement is made in the headunit itself, which is at the end of skinny wires from the fusebox, and a succession of at least two fuses between it and the battery. Fuses drop voltage unavoidably (they have to create heat in order to melt when they need to).

That said, the in-dash reading isn't so much unreliable, it just has a fairly consistent bias. If you've at least once measured the voltage right at the battery and noted the difference with the simultaneous dash reading (ideally in ACC, fewer other variables than ON), you can remember that and use it for quick checks.

-Chap

 

This morning from the jump point...all good then ?

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Not bad. I'll see 12.5 if the car's sat 3~4 days.

 

Not necessarily. Our 2011 had a battery that wouldn't start the car, or even power the SKS door locks.

Here's the reading after charging the old battery:



Even at 12.6v measured at the terminals, the battery wouldn't start the car.

Here's the Optima yellow top that was purchased to replace the bad battery:



So your battery measuring 12.x volts just tells you that there's no dead cells, but the battery could still be unable to provide the amps under load to take care of business.

As mentioned previously, the battery's inability to hold a charge over time also indicates that it is time to replace it.

Purchase a battery maintainer, AKA a trickle charger. It will help the new battery from getting discharged too low due to sitting and low mileage driving after multiple starts.

 

Low mileage isn't a problem as is used as a taxi...... is there a way charge the battery without disconnecting from the boot?
I guess there is no way to measure the amp while under load?
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Solar ba5 is what I use to measure cranking amps. They're about $60? Good tool to have.

There's no problem charging by connecting at the jump point. Owner's Manual says to take battery right out, but it's probably the lawyers behind that.

 

You can apply some load on the battery by turning on the headlights (lowbeam and highbeams) with all systems off. This will typically drop the voltage reading on the battery.

 

Look what I did find in my Wth this go box,it as the cranking test

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So ok on crank but week on voltage?

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It's not giving you numbers, but for what it is, seems to be saying: this battery is worth charging.