bluenose1940

Probably Another Stupid Question!

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Does the IS300h have a 12v battery under the bonnet the same as an ordinary car?

Or, is all of the cars electrics dealt with by the battery/ies in the boot.

If you find yourself in a 'Flat battery' situation, is it dealt with by way of a 'normal' battery charger and, if there is a battery under the bonnet where you would normally connect said charger, does this charge get fed through to the battery/ies in the boot or, are they two entirely seperate entities?

Wipe that grin off your face!!! I know it may sound stupid but I really don't know the answer!

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If it's like the RX there is a normal car battery under the bonnet that just starts up all the electronics. If that goes flat you can just connect a charger to it. The hybrid batteries you don't ever need to touch.

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There is a normal but slightly smaller 12v battery in the boot to power the electronics in addition to the main traction battery.

It can be jump started using a special terminal in the fusebox under the bonnet and I presume charged like any other car battery.

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From a painful experience the 12V battery is in the boot (left hand side behind a removable panel) and if it comes disconnected everything stops working, the AA jump started it via a connection in the fuse box under the bonnet therefore I assume you can charge or trickle charge from this point as well.

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Does the IS300h have a 12v battery under the bonnet the same as an ordinary car?

Or, is all of the cars electrics dealt with by the battery/ies in the boot.

If you find yourself in a 'Flat battery' situation, is it dealt with by way of a 'normal' battery charger and, if there is a battery under the bonnet where you would normally connect said charger, does this charge get fed through to the battery/ies in the boot or, are they two entirely seperate entities?

Wipe that grin off your face!!! I know it may sound stupid but I really don't know the answer!

I have to admit despite having mine since Sept '13 I couldn't answer the question :blush:

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I haven't got around to 'digging' about under the car but from initial inspection and reading the makers info it appears that a small conventional battery is located in the left hand side of the boot. Logical I guess as hybrid system operates on far higher voltage than 12v of normal car battery - and what happens if hybrid cells are depleted - you wouldn't be able to start the engine.

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Probably the most important point is to use a trickle charger! Otherwise you'll fry the hybrid battery out as well!

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Probably the most important point is to use a trickle charger! Otherwise you'll fry the hybrid battery out as well!

PMSL !! A 12v charger is going to fry a 300v battery? Really?

The two circuits will be isolated anyway.

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Does the IS300h have a 12v battery under the bonnet the same as an ordinary car?

Or, is all of the cars electrics dealt with by the battery/ies in the boot.

If you find yourself in a 'Flat battery' situation, is it dealt with by way of a 'normal' battery charger and, if there is a battery under the bonnet where you would normally connect said charger, does this charge get fed through to the battery/ies in the boot or, are they two entirely seperate entities?

It does have a 12v battery (known as the auxiliary battery), but it is actually located in the boot rather than in the engine bay. There is a special jump start terminal in the engine bay fuse box for emergency starting because if the battery is dead you cannot easily get into the boot.

Due to the fact that the 12v battery doesn't actually start the engine, very little current is actually required to 'jump start' the vehicle. The jump start terminal and wiring is therefore low current and should only be used to jump the IS300h, you cannot jump another vehicle using it - you would have to connect jump leads directly to the battery in the boot to do this.

Whilst you can charge the battery using the jump terminal the normal manufacturer advise for any vehicle is to disconnect the battery from the vehicle before charging and therefore you would 'jump' the vehicle to get it going for a few minutes, open the boot, switch off, disconnect the battery and then charge.

The hybrid battery is completely separate to this. You should never be in a situation where that goes flat, even when it appear flat from the battery status indicator there is still a lot of charge remaining to maintain battery health and to turn over the petrol engine to start it. If it was flat then you would get an error when turning on the vehicle and it would have to be towed to a dealer to charge it up - I could only see this happening if you used EV mode to discharge the battery as much as possible and then turned it off and left the vehicle for 6+ months.

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Well, it turns out not to have been such a stupid question after all eh!

Thank you all for your input, with special thanks to ColinBarber for the usual comprehensive input.

I have my fingers crossed that I will be doing my own IS300h in-car investigations before January is out!

Keep your eyes peeled!!

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Probably the most important point is to use a trickle charger! Otherwise you'll fry the hybrid battery out as well!

PMSL !! A 12v charger is going to fry a 300v battery? Really?

The two circuits will be isolated anyway.

Blame the service guy, must be feeding me wrong information!

So you can just use any conventional car battery charger? Pretty sure the manual said "use trickle charger or it may damage the hybrid system"

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