Prius Jump Start

[Joncon]

Hi

The first nine months after buying my Prius it was fine, then the 12v Battery started playing up. Checked doors closed, key not left in, no lights on, etc., but still after three or four days without driving the voltage started dropping. Local main dealers could find nothing wrong with the Battery or the car; now they have taken it in for a longer term examination, so we''ll have to see if they come up with anything.

Meanwhile, just to hedge my bets, can anyone recommend a suitable 12v rechargeable Battery pack I could buy, to jump start it if necessary?

[timberwolf]

I haven't got any recommendations for a particular model.

What I would say is avoid the ones that work inside the car via the cigarette socket/power outlet because on the Prius it is disconnected when the power is off.

Most of the 12v Battery starters/jump starters will boast how much power they have, which is going to be much more than is ever going to be needed to start the Prius, so I think the lowest crank amp rated one would be fine.

I am a little paranoid about the Aux 12v Battery, so I'm always interested in details that can help further my knowledge. If you don't mind could you explain in more detail what you mean by how it started playing up and how you determined that voltage had dropped?

[Joncon]

I haven't got any recommendations for a particular model.

What I would say is avoid the ones that work inside the car via the cigarette socket/power outlet because on the Prius it is disconnected when the power is off.

Most of the 12v battery starters/jump starters will boast how much power they have, which is going to be much more than is ever going to be needed to start the Prius, so I think the lowest crank amp rated one would be fine.

I am a little paranoid about the Aux 12v battery, so I'm always interested in details that can help further my knowledge. If you don't mind could you explain in more detail what you mean by how it started playing up and how you determined that voltage had dropped?

I had the car for about 9 months without any problems, then one morning after I hadn't driven it for a week or so it wouldn't start. I got the RAC (via Club Toyota) and the engineer checked the auxiliary Battery voltage; it was 7.5v. He jump started it with his Battery pack, and I drove for about 30 minutes to charge up.

After that I often found, if I hadn't driven for more than 4/5 days, that when I tried to start, I felt some kickback on the brake pedal, and the red triangular warning light appeared for a couple of seconds. Once when this had happened I checked the Battery voltage and found it was 10.5v.

Since then I always charged the battery using a trickle charger connected directly to the battery in the boot the day before I wanted to use the car.

After a few weeks of this I decided to check to see how the voltage varied without me charging it, so I started checking using a Fluke multimeter connected to the battery terminals. The results were as follows:

Drove 150 miles in 2 days, and started checking after 2 more days: 12.29v.

Daily voltages after that were 12.30, 12.27, 12.23, 12.21, 12.19, 12.14, 11.40, 7.77.

That was when I wrote a rather critical letter to my local main dealer, and they took the car in for a longterm test. I have just heard from them, to say that after 2 days the voltage had dropped from 12.3v to 12.0v, and they have replaced the battery. They are now going to see what happens over the weekend, and ring me again next Monday (22 June).

Will keep you informed!

[timberwolf]

I had the car for about 9 months without any problems, then one morning after I hadn't driven it for a week or so it wouldn't start. I got the RAC (via Club Toyota) and the engineer checked the auxiliary battery voltage; it was 7.5v. He jump started it with his battery pack, and I drove for about 30 minutes to charge up.

After that I often found, if I hadn't driven for more than 4/5 days, that when I tried to start, I felt some kickback on the brake pedal, and the red triangular warning light appeared for a couple of seconds. Once when this had happened I checked the battery voltage and found it was 10.5v.

Since then I always charged the battery using a trickle charger connected directly to the battery in the boot the day before I wanted to use the car.

After a few weeks of this I decided to check to see how the voltage varied without me charging it, so I started checking using a Fluke multimeter connected to the battery terminals. The results were as follows:

Drove 150 miles in 2 days, and started checking after 2 more days: 12.29v.

Daily voltages after that were 12.30, 12.27, 12.23, 12.21, 12.19, 12.14, 11.40, 7.77.

That was when I wrote a rather critical letter to my local main dealer, and they took the car in for a longterm test. I have just heard from them, to say that after 2 days the voltage had dropped from 12.3v to 12.0v, and they have replaced the battery. They are now going to see what happens over the weekend, and ring me again next Monday (22 June).

Will keep you informed!

Thanks, very interesting.

I haven't got a multimeter yet, the Fluke (and Avo) are the only quality brands that I am aware of, but they are expensive.

From what I understand, 30 minutes driving will probably not really do that much charging on a Prius, as the car's charging voltage is a constant voltage somewhere in the range 13.8 to 14.1v, and the constant voltage apparently isn't a good way to charge a 12v Battery to its full capacity.

Using the service menus on the MFD, my 12v Battery has measured 12.1v from new but that is under a load as you have to be in at least ACC mode to operate the MFD. I did charge it up with an intelligent charger two weekends ago, and that took approx 7 hours for the charger to switch to trickle/maintenance mode.

[Joncon]

I had the car for about 9 months without any problems, then one morning after I hadn't driven it for a week or so it wouldn't start. I got the RAC (via Club Toyota) and the engineer checked the auxiliary battery voltage; it was 7.5v. He jump started it with his battery pack, and I drove for about 30 minutes to charge up.

After that I often found, if I hadn't driven for more than 4/5 days, that when I tried to start, I felt some kickback on the brake pedal, and the red triangular warning light appeared for a couple of seconds. Once when this had happened I checked the battery voltage and found it was 10.5v.

Since then I always charged the battery using a trickle charger connected directly to the battery in the boot the day before I wanted to use the car.

After a few weeks of this I decided to check to see how the voltage varied without me charging it, so I started checking using a Fluke multimeter connected to the battery terminals. The results were as follows:

Drove 150 miles in 2 days, and started checking after 2 more days: 12.29v.

Daily voltages after that were 12.30, 12.27, 12.23, 12.21, 12.19, 12.14, 11.40, 7.77.

That was when I wrote a rather critical letter to my local main dealer, and they took the car in for a longterm test. I have just heard from them, to say that after 2 days the voltage had dropped from 12.3v to 12.0v, and they have replaced the battery. They are now going to see what happens over the weekend, and ring me again next Monday (22 June).

Will keep you informed!

Thanks, very interesting.

I haven't got a multimeter yet, the Fluke (and Avo) are the only quality brands that I am aware of, but they are expensive.

From what I understand, 30 minutes driving will probably not really do that much charging on a Prius, as the car's charging voltage is a constant voltage somewhere in the range 13.8 to 14.1v, and the constant voltage apparently isn't a good way to charge a 12v Battery to its full capacity.

Using the service menus on the MFD, my 12v Battery has measured 12.1v from new but that is under a load as you have to be in at least ACC mode to operate the MFD. I did charge it up with an intelligent charger two weekends ago, and that took approx 7 hours for the charger to switch to trickle/maintenance mode.

When you charged your Battery, did you remove it from the car, or disconnect the ground lead, or do neither of these things?

[timberwolf]

I bought a CTEK charger because they specifically claimed that it was okay to charge the 12v Battery whilst the Battery remains connected to a car.

I don't switch the car on or open the doors whilst charging - e.g. opening and closing the driver's door will after a small delay cause the Prius' brake pump to operate. I've only done the one full charge in 6 months.

A pdf version of the charger manual.

http://www.ctek.com/Manuals/new_XS3600_EN.pdf

Where I bought mine from they have download link for an earlier version of pdf manual which looks like the paper copy.

http://www.theultimatefinish.co.uk/Store/P...x?ProductId=104

I do the MFD service menu 12v displayinging with the following instructions (about half way down the page)

http://www.elearnaid.com/12vo1topraub.html

Mine alternates between 12.1v and 11.9v in ACC mode and has done since new. After I charged it up, I think about 10 minutes after I had removed the charger, when I did the MFD magic it was reading 12.5v and a week later without driving it was back to 12.1v. I do wonder if 12.1v is 80% capacity for the standard Toyota Battery?

[Chris Dance]

timberwolf. Please can you explain the MFD magic you refer to.

I have a normal Halfords Battery charger which has to be connected to a mains supply. It does have trickle and normal charge modes. I have never used it on the Prius but if I did connect it to the Prius 12v Battery I would have to have the boot open for the mains lead. Are there problems with charging with boot open? For instance you say with drivers door being open the brake pump operates.

If I did need to remove the Battery for charging what problems would there be after refitting it? Any advise or help much appreciated.

I am also nervous about the 12v battery going down: so much in fact that my Prius had not been driven for 4 days so this morning I took it a few miles drive on the motorway.

[Joncon]

timberwolf. Please can you explain the MFD magic you refer to.

I have a normal Halfords battery charger which has to be connected to a mains supply. It does have trickle and normal charge modes. I have never used it on the Prius but if I did connect it to the Prius 12v battery I would have to have the boot open for the mains lead. Are there problems with charging with boot open? For instance you say with drivers door being open the brake pump operates.

If I did need to remove the battery for charging what problems would there be after refitting it? Any advise or help much appreciated.

I am also nervous about the 12v battery going down: so much in fact that my Prius had not been driven for 4 days so this morning I took it a few miles drive on the motorway.

Chris

I think what Timberwolf is referring to is the page he quotes which is http://www.elearnaid.com/12vo1topraub.html. About three quarters down this page is a heading "Prius Battery test procedure for 2004 to 2009 Prius Cars", which gives all the details for checking the Battery voltage on the display screen.

I have charged my 12v Battery with a standard trickle charger connected direct to the battery terminals, yes, with the boot lid open, but you can also connect the charger to the jump start terminals which are in the fuse box under the bonnet.

Timberwolf: going back to my previous query about a jump start battery, I agree you don't need anything like as much current as you need to crank an ordinary car, and I found a battery which might do at http://www.thesafetycentre.co.uk/store/sea...CFd4B4wodsQK7pw. The first one they list is the Energys Genesis NP 1.2 Ah sealed lead acid battery, but if you look at the datasheet (right at the bottom) it appears that the maximum charging current is 0.3A, while all the chargers I have found seem to have an output of either 3A or 0.8A. Do you know of a charger which I could use for this battery?

[timberwolf]

Timberwolf: going back to my previous query about a jump start battery, I agree you don't need anything like as much current as you need to crank an ordinary car, and I found a battery which might do at http://www.thesafetycentre.co.uk/store/sea...CFd4B4wodsQK7pw. The first one they list is the Energys Genesis NP 1.2 Ah sealed lead acid battery, but if you look at the datasheet (right at the bottom) it appears that the maximum charging current is 0.3A, while all the chargers I have found seem to have an output of either 3A or 0.8A. Do you know of a charger which I could use for this battery?

These chargers would seem to be suitable for the Battery that you mention.

http://cpc.farnell.com/yuasa/cm03a12t/char...0mah/dp/BT02048

http://www.rapidonline.com/Electrical-Powe...ogleps#techspec

[monj]

Hello matey unfortunately the priuses do seem to have troubles with that Battery,toyota say that as standard if you are going to leave the prius for more than 2 weeks you should remove that Battery because it will go flat,it doesnt seem right that its going flat in just one week though.there are a few things that will flatten the Battery if you leave the car running in the neutral position it cannot charge either battery,and if you sit in the car with just the ignition on it will flatten the battery quite quickly.although i have known a couple that flattened the battery in a week and that was due to a drain that was caused by an ecu fault.there is a jump start terminal under the bonnet in the fuse box behind the n/s/f headlamp that you might be able to connect a trickle charger to to keep it topped up if the garage cant find any fault.

[timberwolf]

timberwolf. Please can you explain the MFD magic you refer to.

As Joncon says, the magic invocation/procedure was in the elearn web link that I provided. It turns your Prius costing 20,000 GBP into a voltmeter and it can only read its own Aux 12v Battery when the Battery has enough charge to power on in ACC mode. Don't be tempted to play with the other service menus! A quality Digital Multimeter would be a much nicer piece of kit to own and use.

I have a normal Halfords battery charger which has to be connected to a mains supply. It does have trickle and normal charge modes. I have never used it on the Prius but if I did connect it to the Prius 12v battery I would have to have the boot open for the mains lead. Are there problems with charging with boot open? For instance you say with drivers door being open the brake pump operates.

Check the instructions that came with your Battery charger. Just because your battery charger says it has a trickle mode, doesn't mean it is a trickle charger suitable for permanent connection to a vehicle. Your car has lots of expensive electronics, personally I wouldn't connect a charger that didn't say it could be, but then I am paranoid! :)

No problem with the boot hatch being open as far as I know. The brake pump is mentioned in the Owner's manual, open your driver's door, sit inside and close the door, and now don't do anything, in a short while you'll hear the pump activate. The brake pump draws a reasonable current from the 12v battery. The courtesy light in the boot uses very little, although you can switch the light off, I have just because if I leave the hatch open by accident there would be a little more current drawn and long term that will drain the battery more.

If I did need to remove the battery for charging what problems would there be after refitting it? Any advise or help much appreciated.

I am also nervous about the 12v battery going down: so much in fact that my Prius had not been driven for 4 days so this morning I took it a few miles drive on the motorway.

If you disconnect the 12v battery, the driver's auto window will need to be initialised (easy procedure), you may also lose radio settings, gps nav settings/saved destinations, the clock, your average MPG, etc. There is a small risk that removing and reconnecting the 12v battery can cause damage to any of the sensitive electronics and a big repair bill!

Okay, I'll try to ease your nerves a little. I usually only drive my car at the weekends, and occasionally a quick errand during the week, so most of the time my car isn't being driven for 5 days at a time. In the last 6 months, on the odd occasion that I've checked the voltage using the MFD service menu, it has always shown the same 12.1v (alternating with 11.9v) that it did on the very first weekend that I brought my Prius home. In the longer term, I am only guessing that my usage will not favour a long life for my 12v battery! Such is life.

By the way, what is the cost of a new Prius Aux 12v battery?

[Chris Dance]

Thank you for the information. I suppose if we get a high tech car we can get high tech problems. Never heard of some many problems with regard to a 12v Battery. I think Mr T all the RAC will be called if I get trouble. My car will be well used this Summer so with luck the Battery should keep charged. It goes for the second service in Sept so I will question the dealer about these issues.

Happy Motoring.

Chris.

[timberwolf]

Timberwolf: going back to my previous query about a jump start battery, I agree you don't need anything like as much current as you need to crank an ordinary car, and I found a battery which might do at http://www.thesafetycentre.co.uk/store/sea...CFd4B4wodsQK7pw. The first one they list is the Energys Genesis NP 1.2 Ah sealed lead acid battery, but if you look at the datasheet (right at the bottom) it appears that the maximum charging current is 0.3A, while all the chargers I have found seem to have an output of either 3A or 0.8A. Do you know of a charger which I could use for this battery?

These chargers would seem to be suitable for the Battery that you mention.

http://cpc.farnell.com/yuasa/cm03a12t/char...0mah/dp/BT02048

http://www.rapidonline.com/Electrical-Powe...ogleps#techspec

Joncon,

I happened to notice that one of my work colleagues has a 12v 5.7Ah Battery on his desk, which I think he used to use with lights on his mountain bike. As the Battery on his desk seems quite small, I hadn't realised just how small the physical dimensions must be of that 1.2Ah battery you posted about.

[Joncon]

97mm x 48mm x 51mm. Quite small!