Battery pack jump starters

I don't know that specific car but... other hybrid vehicles I've used that have the 12V conventional lead acid battery buried under the floors of trunks (US...) and hatchbacks, also...

... also have cable post "appearances" under the main (front) engine hood specifically to make jump starting easier.

You might want to see if that's the case with yours.

Good luck.

Apparently, there is a jumpstart terminal under the bonnet. Perhaps RTM?

Sods law it will have lost charge because you haven't had it out to top-up charge it every 3 to 6 months.

I've only used mine once on a neighbours' car where the battery had been run totally flat. I was surprised how well it worked. Connected up my box, waited a few minutes and the car started immediately on the first turn of the key. The lights were still on!

BigClive and his youtube videos is the way to go.......

On a neighbours car (not hybrid) the battery was not easily accessible being under a cover under the passenger seat but there was a jumpstart terminal under the bonnet to accept the positive lead. The terminal had a removable plastic cover. The negative lead had to be connected to the engine or conductive part of the chassis, Just make sure before that you have to use a jump-start box in anger that the short leads that come with it can reach a negative connection on the engine or chassis.

The red box - youtube video tear-down

If the car is in vaguely regular use then it is extremely unlikely that the 12v computer battery will ever go really flat until it is really old (think ten years). That battery gets charged from the hybrid battery.

Our Outlander Hybrid has that arrangement- 12V battery in boot, 'jump start' point under bonnet. I've not needed to use it.

On the Outlander, the jump start is just to power electronics, it doesn't power a starter motor, so the current required is quite small.

If the car isn't driven for 24hrs (I think), the car automatically tops up the 12V battery at 2pm each day from the drive battery. Having left our car parked, not on charge but charged, for a month, the main battery still showed full charge and it powered up no problem. (Nearly a year old at the time.)

There is a jump start point under the bonnet, in the fuse box on the right as you look in the bonnet, there is a flip up red plastic lid marked with a plus sign, negative can go to any convenient metal bit.

And: if the boot battery is flat, the tailgate release won't work.

The 12V battery in an RX450h isn't used for starting the car. The HV battery does that.

You do need the 12v battery to power up the car's electronics, but I doubt that needs much current.

No actual usefulness in this post, but: I thought that the easy way out was to connect the powerpack to the cigarette lighter. This is quick and easy to get to, but limits the current to what the fuse (20A?) will allow, time considered. So the powerpacks get connected to the CL jack, and left there for ten minutes, and this boosts the 12 V battery so the it can start the car (100s of amps, at least on conventional engines).

The AAA man has a different powerpack, with small batteries that can deliver

100s of amps, and that might burn out the fuse if attached to the CL rather than the battery poles. These packs contain individual lead-acid cells, I think.

Thomas Prufer

It's a diode pack to prevent the alternator (possibly) overcharging the battery pack when the engine starts.

Described by Big Clive in

They are standard connectors, I have bought a few (there is also a smaller version, usually blue) to make up dedicated connections for convenience.

I *guess* the red box could be a fuse, or possibly a thermal cutout. Probably *not* a diode to protect against reverse connection (but I could be wrong)

One thing to watch, the car manual will probably tell you not to try to jump start it (my Honda Jazz hybrid says the same). However I have done it once, but it did upset the alarm system. Can't quite remember the details, IIRC I had to leave the engine running for a bit either with the door open or the door closed, otherwise the alarm would sound. It sorted itself out after a few minutes.

What I'd expect if the battery is inaccessible. BWM have had jump start terminals under the bonnet for years.

Thanks for your replies folks, much appreciated.

I just wanted to say that I did already know that there's a dedicated 'jump start terminal' in the engine bay fusebox but when you lift the bonnet there is almost nothing to see because there are big plastic covers fitted. I would have to take out six or more tiny plastic clips, which I would no doubt break or drop, never to be seen again, to remove the cover to get at the fusebox. On a cold, wet, windy night, that's not much better than going directly to the battery in the boot. My idea is to have a plug and socket arrangement somewhere unobtrusive in the cabin so that I can stay dry.

Thomas Prufer's idea of using the cigarette lighter is a good one but unfortunately not on a Lexus. The lighter is only live when the ignition is on so there's no direct 12V path back to the battery from there.

I'm also aware that, like others have stated, in a hybrid car the 12V battery only powers up the entry/exit system and boots up the computers to bring the car to the READY state. Once ready, a DC/DC converter takes the 288V traction battery voltage and outputs about 13-14V to charge the small 12V battery, which also means that there's no need to leave the jumper pack on for a few minutes as you maybe would in a conventional car. Unlike a 'normal' starter motor that draws a current of 300A or more, if you look here

you'll see that my meter is showing a draw of just 15.32A to get the hybrid system up and running.

Thanks again folks, Pete

Is there not another "Hot" access point for clipping onto under the bonnet? Worth checking the user manual before making any alterations.

it doesn't but people do cause them to get low, once below a certain voltage the relays drop out and nothing works.

many cigar lighters are inoperative with the ignition off, and a flat battery means that the protection relays drop out and nothing goes anywhere.

Except that it is usually a PITA to find a way through the bulkhead. In the interest of easy, short runs I think I would tap in to the jump start terminal and have the socket there, and put up with the risk of having to get out and under the bonnet on rare occasions.