12 V Battery, Capacity Rating

[JohnD2]

Hi. Prius T-Spirit. DoR Mar 2008. (Gen 3?). Could someone point me to a trustworthy link to establish the ampere/hour capacity of the special 12 v Battery? please. J

[Grumpy Cabbie]

The gen3 in the UK ran from about June 2009 onwards.

What do you want to know the capacity for? I'm sure someone will find that for you and it will be rather small as it doesnt need to crank the engine ever - it just boots up some computers which then command the big HV Battery to start the engine and/or power the car.

If you're wanting to run things off the 12v you're best leaving the car in the Ready mode as this will take the strain off the 12v. When I used my car as a taxi I used to run a taxi meter, 5 watt 2 way radio, despatch computer, sat nav and mobile phone off the car and used to leave it in Ready mode 99% of the time.

[JohnD2]

GC, 1. Thanks for correction/update on Gen. 2. The reason I want to know the capacity is because I'm thinking of buying a Battery charger and the manufacturers have models appropriate to the capacity. 3. I'm assuming that I also run in Ready mode, I'm not sure of what other modes you have in mind. J.

[Grumpy Cabbie]

The capacity is probably the lowet end of the range, almost on a par with motorcycle batteries.

A lot of people leave the car in Acc mode (engine never runs) so that they can listen to the radio. This is what they would have previously done in a traditional car to save petrol. Trouble is with a Prius/Auris hsd is that the 12v is weak and they can run it down after 60 mins of radio and there is no real need to leave the Prius in Acc as you just leave it in Ready and listen to the radio and the engine will barely come on - if at all an dont run the risk of a flat 12v.

[timberwolf]

How are you planning to charge the 12V Battery, with the Battery still connected in the car, or are you disconnecting and charging it in a well ventilated garage?

You need to ensure that the charger that you buy is a good quality one. I was looking for a charger/conditioner/trickle (maintenance) charger that would be safe to use with the 12V Battery still connected in the car (i.e. I didn't want to damage any of the sensitive ECU computers on the Prius). It must charge the 12V battery at no more than 4 Amps.

The link below is the model of Ctek charger that I bought for my Prius a couple of years ago. I seem to recall that Porsche supplied Ctek (branded with Porsche obviously) for customers to use on their Porsche cars.

http://www.amazon.co.uk/Ctek-CTE-XS3600-Battery-Charger-Functional/dp/B000RHWCNY

There are other makes of conditioner/charger available, but I liked the reviews of the Ctek.

Happy shopping.

[Sagitar]

The Toyota main dealer from whom I bought the car recommended this one:- http://www.amazon.co.uk/OptiMate-4-Battery-charger-conditioner/dp/B000R5936U

It comes with a two-pin plug and socket that attaches permanently to the Battery and enables a connection inside the boot with the charger on the garage wall.

[timberwolf]

Ah yes, now you mention it I have heard of the OptiMate. The 22V worried me though, but I found the pdf manual that makes it clear that the charger senses whether the Battery is still connected to the car and doesn't try to raise the voltage that high.

The CTEK charger will only go as higher as 14.4V (14.7V if set to Winter charge mode).

[valmiki]

Every few months the local LIDL sells full-auto chargers that look *very* similar to the CTEK 3600, for about £12 each. They feel very well built, I bought 3 last year and passed then out to the family, to use over the winter months. Work fantastic :-) Every time they come on sale, the car forums get buzzing, lol. There's a photo of them:

[timberwolf]

A new car £22000 vs £12 on an unknown make of charger, what is the risk compared with spending another £32 for one from a manufacturer with a good reputation?

[valmiki]

A new car £22000 vs £12 on an unknown make of charger, what is the risk compared with spending another £32 for one from a manufacturer with a good reputation?

I understand your reluctance, to some LIDL = cheap and nasty, thankfully there's plenty of reviews of the charger that beg to differ, so why pay more than necessary? Why not spend £200 on a Porsche-branded one?

Each to their own, I've been more than happy with the ones that I've bought.

[timberwolf]

I don't believe you are comparing like for like. The CTEK vs Porsche branded version is as I understand it still a CTEK design, although I've no way of knowing if Porsche had any changes made to their version designed for them by CTEK.

The Ultimate Speed is of unknown origin to me. Is it an exact copy of the CTEK design? Is it a close approximation of the design? Does Ultimate Speed charger actually work the same way as the CTEK? If Ultimate Speed is a copy then did the company understand what they were stealing, for example do they understand the design well enough to correctly substitute components and still keep the charger working as it was meant to?

BTW From what I've read the CTEK and OptiMate chargers work a bit differently, at least on whether they'll attempt to revive a dead Battery.

BTW if I owned an expensive sports car, knowing me, I'd probably be spending significantly more money on Professional detailing per year, dust covers, a spotless tiled garage to keep it in, etc, so the over-priced branding of a charger wouldn't be problem, now all I need to do is win the lottery, LOL.

[Grumpy Cabbie]

I'm not entirely sure why anyone needs a Battery charger these days unless you intend on storing the vehicle for months at a time?

My 12v must have had a load of hammer compared to many, yet seems ok and the car barely gets used once or twice a week now and only for shorter runs. I think they have a useful life of 4-5 years and/or 80,000 miles, so mine is due for replacement soon.

[timberwolf]

I'm anyone:-) I've found having a charger very useful, restored/revived a bit more life in my 12V Battery a number of times now.

[Sagitar]

I'm not entirely sure why anyone needs a battery charger these days unless you intend on storing the vehicle for months at a time?

My 12v must have had a load of hammer compared to many, yet seems ok and the car barely gets used once or twice a week now and only for shorter runs. I think they have a useful life of 4-5 years and/or 80,000 miles, so mine is due for replacement soon.

Haven't been without a charger in the garage for over fifty years. We have several devices with lead acid batteries that tend to be used only during the summer. The cheap plug-in chargers supplied with them are generally inadequate. A good modern charger looks after batteries very well and can extend their life significantly.

It's not difficult to find several instances of a cell failure in the Prius 12v Battery at relatively low mileages. Mine failed with only 9,777 miles on the clock and was changed under warranty. Up to that point, it had never struck me that it might help to give it an external charge, but I do it regularly now.

[JohnD2]

Apologies re delay, been away. Thanks for all contributions. I've spent some long time on the 'net. The only mention I could find was on a US site (Priuschat?). A contributor stated the 12 Battery to be 36 aH, which would feel about right. Assuming it is, the ctek 3.6 model would seem to be a close match. The whole problem started with a return after 3 weeks to find the Battery almost completely flat. Pressing Ready gave no response. I used my normal Battery charger, but the 'switch on' surge current ( c 15 amps ) was sufficient to trip the over current circuit. I'd rather not say how I got the car running!! but it seems ok now. Does anyone have any info or opinions as to whether the ctek 3.6 model can cope with the situation I've described?

[timberwolf]

Apologies re delay, been away. Thanks for all contributions. I've spent some long time on the 'net. The only mention I could find was on a US site (Priuschat?). A contributor stated the 12 battery to be 36 aH, which would feel about right. Assuming it is, the ctek 3.6 model would seem to be a close match. The whole problem started with a return after 3 weeks to find the battery almost completely flat. Pressing Ready gave no response. I used my normal battery charger, but the 'switch on' surge current ( c 15 amps ) was sufficient to trip the over current circuit. I'd rather not say how I got the car running!! but it seems ok now. Does anyone have any info or opinions as to whether the ctek 3.6 model can cope with the situation I've described?

I found your post a little difficult to understand, and I apologies if I have made an error when interpreting what you've said.

There is a difference between charging in A (Amps) and the capacity of a Battery in Ah (Amp hours). For example, Toyota recommend not charging the 12V Battery at more than 4 A. The Ah is how long the Battery will last, for a 36 Ah battery, it could supply 1 Amp for 36 hours, or 2 Amps for 18 hours, 72 Amps for 30 minutes.

Anyway onto chargers, if you look at the specification, you should see that the CTEK charge is good for batteries rated up to 75 Ah. See the following site for the specification and link to download the user manual.

http://www.theultimatefinish.co.uk/ctek/multi-mxs-3-6-12v-battery-charger-and-conditioner.aspx

(I know I've bought some car stuff from this company, it may even have been the older model of CTEK battery charger...)

Your switch on current comment has me a bit puzzled, I hope you were not trying to use the battery charger to jump start the car? Battery chargers are not designed to jump start cars, they are designed to charge the 12V battery.

[JohnD2]

My fault for not being clear: I'm trying to keep it short. I wanted to understand why my usual charger wasn't working. So I put an ammeter in series with its output before switching on. When I did switch on, the reading peaked quickly at around 15 amps, then just as quickly back to almost zero. Roughly one second. I'm assuming that the protection circuitry in the charger is coming into operation. (Remember that the Battery was probably almost empty). What I want to be sure of, is that if I buy a new charger, can it cope with such a situation. Thanks for the link, I will examine.

[ticktockmac]

I had a flat 12V several times 18 months ago because the 'boot' hatch didn't fully close and the light stayed on. I now carry at all times an RAC 400amp Rechargeable Jump Start System. It's small, stays charged for months and has short built-in heavy duty leads and can start my Prius within 20 seconds of lifting the bonnet. It's case is plastic, so I rest it on top of the Battery while I start the car and the leads are just right for that. The leads even clip into the case of the unit for storage. It also has 12V outlets that take cigarette lighter style plugs to run other equipment too, such as tyre pumps or lights. I wouldn't be without it. I paid around £25 for mine but my local branch of Roibert Dyas has had them on offer recently for £19.99.

[ticktockmac]

I considered replacing my 12 Battery just over a year ago thinking it was faulty. Two dealers and Toyota HQ quoted a crazy price of around £300. After much protesting they admitted there was a mistake on their system and it should have been £80 or £90 - a huge difference, but still exorbitant for such a tiny Battery. Make sure you don't get ripped off if you get a new Battery. I believe that alternatives don't all have a special breather tube or some such feature of the official part.