Jump Starting a Hybrid

[Roker]

I cannot understand how it is possible to jump start a hybrid. If a good Battery is jumped to the car Battery, the electronics will see that the Battery is good an not start the engine because it will want the run the elect motor first

[Deemann]

If you connect a 12v Battery or a 12v powerbank it just supplies power to the car's computer. Once the computer is powered the hybrid Battery supplies power to the car's 12v Battery and you can disconnect external battery / powerbank. The the hybrid system then works as normal and starts the Internal combustion engine if required or the car will run on the Hybrid battery if not.

I owned an Ioniq previously and used my powerbank several times when the 12v lead/acid battery was discharged.

[Roy124]

No.  You are confusing the two batteries. 

34 minutes ago, Roker said:

the electronics will see that the battery is good

True.   It will then 'boot' the 12v system which will start and display READY mode.   In Ready mode the HV system will be energised and the car will be good to go.

You can then disconnect the Humber leads and the DC-DC converter will continue to supply 12v to recharge the 12v Battery.

The ICE will not necessarily start if the HV has a good charge and there are minimal 12v services,  aircon, lights, wipers etc running.   It will start as required.

Edit: Snap

[Roker]

I thought the 12v system was used to start the engine, so if it is only used for auxiliaries and will not pull any cranking amps  therefore a small Battery will do it

[Don Mac]

1 hour ago, Roker said:

I thought the 12v system was used to start the engine, so if it is only used for auxiliaries and will not pull any cranking amps  therefore a small battery will do it

Absolutely correct. Your also need to remember that, because it is not set up to crank a conventional ICE, you should not attempt to jump start an ICE car from a hybrid. The 12V Battery in the hybrid isn't designed for that.

[Cyker]

Yes! That is a good warning - Trying to start an engine can pull 400+ amps at 12 volts; The DC-DC system, which the hybrids have instead of an alternator to charge the 12v Battery and power the 12v electrics, is only rated for around 100A, so there's a good chance trying to jump-start a normal car with it will blow up something expensive!  

[Roy124]

10 minutes ago, Don Mac said:

Absolutely correct. Your also need to remember that, because it is not set up to crank a conventional ICE, you should not attempt to jump start an ICE car from a hybrid. The 12V battery in the hybrid isn't designed for that.

Not so much the small 12v Battery, though it certainly lacks the power of larger 12v batteries.  I think it is more that the DC-DC converter has nowhere near the output of an alternator. 

[AisinW]

The 12V Battery is purely charged by the DC to DC converter in the inverter unit above the transmission.  It does not matter whether the engine is on or off, the Inverter will charge the 12V Battery either from the HV Battery or directly from the generator MG1, spined by the gasoline engine.  The DC to DC converter can supply 12V battery as high as 15 Amps.  It is powerful and will charge the 12V battery to almost full safely within 30 minutes. The amperage is changing dynamically.

[Roy124]

24 minutes ago, AisinW said:

The DC to DC converter can supply 12V battery as high as 15 Amps.  It is powerful and will charge the 12V battery to almost full safely within 30 minutes.

Which contrasts with an alternator that Google suggests is 50 amps or even 140 amps depending Battery and alternator. 

[Derek.w]

Dont take the risk of jumpstarting any car from your hybrid except a hybrid.

The Dc/Dc converter is a bit of expensive kit.

Catch a bus to Halfords and buy a Portable Powerpack or use a 12volt 20 Ah Battery or a Battery booster power pack the latter always have blocking diodes to stop alternators charging the small lithium batterys.

[Cyker]

A friend of mine jump-started his Auris hybrid with his son's 14v remote control car Battery pack and some crocodile clips once so it doesn't take much!  

[AisinW]

6 hours ago, Roy124 said:

Which contrasts with an alternator that Google suggests is 50 amps or even 140 amps depending battery and alternator. 

Alternator im compact cars is much smaller than DC to DC converter in Corolla/Prius that can supply 100 Amps to power the 12V electronics continuously.

What the DC to DC converter cannot do is starting other engines that can load more than 100 Amps. Regular car use bigger 12V Battery that can supply up to 700 CCA cold crank Amps. Corolla 12V is now pretty big for the 1.8L one.  

So, if we need to jump starts regular car, we should not turn the car On/Ready mode. Therefore, it is the voltage from the 12V Battery that start other car engine, not DC to DC. 

Hybrid Corolla only need 60 Amps to turn the car to READY mode because it is mainly to power the computer and contactor.  That's why the Battery is relatively small compared to regular compact cars. 

So, we can buy a small but save jump starter as long as it can supply 100 Amps or more. It takes only about 3 seconds so 60A * 3/3600~0.05 Ah battery is theoretically sufficient. Size of the Ah in the battery doesn't matter, just check the maximum Amperage A only not total energy (Ah). 

[Roker]

All the above is assuming it is the 12v Battery, the cranking amps comes from the hybrid batteries, what happens it they are flat?

[Don Mac]

8 hours ago, Roker said:

All the above is assuming it is the 12v battery, the cranking amps comes from the hybrid batteries, what happens it they are flat?

If the hybrid Battery is flat the car won't start, end of story. The car will have to be taken to a dealership for attention.

The engine is started by a motor-generator (MG1) which is powered by / charges the hybrid Battery - it isn't directly connected to the 12V Battery and cannot be powered from it.

Since this is the case the engine management will not let the hybrid battery be fully discharged during use (even though you may have an indicator on the dash showing that). There is a possibility of this happening through self discharge if the car isn't run for a long time, but the 12V battery will go flat first due to the drain on it from keeping certain systems running. The hybrid battery doesn't supply anything when the engine is powered off.

[TonyHSD]

Indeed.
There are no cranking amps in hybrids because there is no cranking at all.  The electric motor instantly starts the engine. The power for which comes from the hybrid Battery. The 12v Battery is also called auxiliary Battery and powers all of the car electronics except traction motor and AC. 
Important to note that when you stop with your hybrid prior to park and leave the car if the engine kicks in and your battery is low Do not turn it off but let the engine running and recharge your battery, turn off itself and then you can switch off the car and leave it parked. 
Here is the latest videos of Toyota magic. This is actually the best invention to date in automobile, not the Tesla. 

 

[Cyker]

Yup - You never ever *ever* want the traction Battery to run out as you're up that creek that people talk about. Thankfully, the car will do it's hardest to not let that happen, and unless you do something to force it to (The 2 most likely ways are running out of fuel and leaving it for too long without refuelling, or leaving the car in N, which is why we all say never use N!!) it should never happen - You'd have to wilfully neglectful for it to even have a chance of happening.

Regarding 'cranking amps', MG1 is the closest thing to a starter motor the car has, and it runs at several hundred volts, so the current draw is a lot less than what a starter motor pulls at its measly 12 volts!!  

[yossarian247]

I have wondered just how long it would take the traction Battery on a hybrid to self-discharge to the point it wouldn't start the engine if you left the car laid up for a very long period? I'm guessing it would be years rather than months? I can see there being some 'interesting' Prius barn find videos around in 30 years time where people try to jump start the traction Battery from an EV! 

[AisinW]

On 7/30/2023 at 10:04 AM, yossarian247 said:

I have wondered just how long it would take the traction battery on a hybrid to self-discharge to the point it wouldn't start the engine if you left the car laid up for a very long period? I'm guessing it would be years rather than months? I can see there being some 'interesting' Prius barn find videos around in 30 years time where people try to jump start the traction battery from an EV! 

Per Toyota TSB, Actually we need to turn the car on for at least 30 minutes to Ready mode every 2 months if it is not driven at all.  Yes, it may takes months before it cannot start but it is not good to the health of the HV Battery.  if it drops below 20%, the cathode/anode got higher stress/strain from the interchelation of the ions.   So, it is 2 months interval to be exact. https://static.nhtsa.gov/odi/tsbs/2020/MC-10177586-9999.pdf

Some people experience this during COVID 19 pandemic and they have to tow the car to the Dealership who has the equipment. GRX-5100 HV rescuer.  https://static.nhtsa.gov/odi/tsbs/2022/MC-10213900-9999.pdf

The 12V infrastructures are all managed by DC to DC converter that is powered by both HV Battery and MG1. It contains a lot of power transistors and need to be cooled by coolant. 

 

[Roker]

It would be handy if someone could specify a small 12v Battery to jump start the system,  or alternatively a method of charging the 12v Battery from the main 200v batteries 

[Cyker]

Well, literally any commonly available jump-starter pack is enough to jump start the system; It doesn't take much, just enough to power the computer up so the car can be started.

As for charging the 12v Battery from the traction Battery, just starting the car will do that. The caveat being that you need at least some charge in the 12v Battery to engage the traction battery, so if the 12v is dead you'll need to jump start it...

 

[Roy124]

Dan, on your last point, I don't believed the HV batteries are 200v and as they are DC you can forget using them like a mains smart charger.

A 12v jumper pack however is easy and good insurance.  I have one like thus:

FLYSAIL Car Jump Starter,Portable Car Emergency Battery Booster Power Pack with Jump Leads, 400A Peak Car Battery Booster Jump Starter,Emergency 12V Car Starter Battery Pack Black https://amzn.eu/d/e8fXTnz

Mine holds a charge for months.  At first I checked it monthly, mow over 6 months but the  charge is over 75%.  Used once in anger.

[Roker]

What is the current drawn for the 12v to jump start, I was looking at a small 12v  7Ah for emergency.

The 12v is not cranking the engine and does not need a high current, this is done from the 200v batteries once the system is Ready

[Roker]

I previously had a :Ring: lithium jump starter and it lay in my boot not being used and when I eventually tried to charge it, it would not charge, so we have a similar problem

[TonyHSD]

3 hours ago, Roker said:

I previously had a :Ring: lithium jump starter and it lay in my boot not being used and when I eventually tried to charge it, it would not charge, so we have a similar problem

This is a Battery that needs to be charged sometimes to maintain enough charge for when needed. If left without use for too long it will die indeed. 

[AisinW]

15 hours ago, Roker said:

I previously had a :Ring: lithium jump starter and it lay in my boot not being used and when I eventually tried to charge it, it would not charge, so we have a similar problem

Lithium ion Battery ideally is stored between 40-85%. Too empty, the cathode will degrade, too full, the anode will degrade and pulverized.  So, for Jump starter, we should set the Battery max at about 80% and do not let it way too deep discharged < 5%.  The same thing with Cellphone, Laptop, and any device.  Fortunately, most of good brands have Battery management system that actually can set the charged states up to 85% like most newest Android OS.  Dell, HP, Lenovo also have this option either via BIOS or via their Apps.  I always set my XPS Dell to max 80% charged and only start charging after the battery states is below 50%.  My 2013 XPS 15 still holds more than 80% of the original battery capacity.   If you never set it that way, within 1 year most Laptop battery will degrade below 70% and in 2nd year they are often dead.   Toyota uses 40-80% range in most of their hybrid cars since 1998. When you see in the panel is full, the actual state is 80% never 100%.