Lexus Owners Beware DON'T Jump Start Your Car Like This!

[@sometimesfirstsometimeslas4908]

Really glad you posted this video. I thought the ground was on the shock tower bolts. But I checked on the online 2022 NX350h manual and it does show the engine mount point. Wow! I was at risk. I thought the manual has shown the tower bolts. Thanks! Luckily, the only times I had to jump the battery, I just trickled charged the 1 v battery. The possible damage risk to the ECU seems odd just because you ground it close the the ECU. I poked around on some other Toyota hybrid forums and the only thing that some thought it might have something to do with DC-DC ground loop concerns- apparently a rare situation. This was totally new to me and most folks, since ground was a ground on a car- or so we thought. Apparently this has been know on the RAV4 Hybrid forums via a Toyota bulletin round 2022ish. Also, maybe not related, but I have a NOCO series X jump starter and it outputs at 16.4V- ouch. The older GB20/40 jump starters output around 14.4V. My old Anti-gravity jump start only outputs 12.5v. I think I might switch to the NOCO GB20 just be safe, since all we really need is just enough 12v current to power-up the hybrid system. And 14.4V is the typical max a 12 charging system will supply to even a low battery, so it should be very safe.

[@lsft]

Yes - it was provided in either documents on Toyota vehicles, but I assume some people did jump with those bolts and caused the board to burn. Wow 16.4V is a very high. The GB20 seems to be good enough with 14.4V. I think you have made a good choice on the jump starter.

[@sometimesfirstsometimeslas4908]

​@@lsft There sare several things that make the current crop of LI jump starters not the best option for a Toyota hybrid. 1) There seems apparently a jump starter race to see how fast can one crank a dead ICE battery. (per UT reviews). This is why they added the extra LI cell (3.7v) to get into the 16+V range. Of course, for a a hybrid it does not have this high current requirement, so much less demand on a high powered jump starter. Best case, we just overbuy a jump starter. Worst case, we subject the ECU/hybrid system to an unneeded high voltage. 2) It is likely for a dead ICE battery's low state of charge causes a large voltage drop in the jump starter, since the current demand is so high. Note: The jump starter probably drops into a safe ECU volage range almost immediately for ICE. (a hybrid probably has a voltage drop also, but likely not quite as large of a drop- i.e. possible more risk for the ECU?). 3) Highly likely any ECU damage for most cars is long-term damage vs immediate burning out the ECU do to too much voltage,,so most would not blame a premature ECU failure on the jump starter. And maybe the risk is really low or just not noticed immediately in most situations. Hybrid risk? TBD. So what does that mean for our hybrids? Someone should make a hybrid jump starter. LOL. The risk above may just be small even for a hybrid, but the failures of a Toyota hybrid ECU just jump starting the hybrid raises for me lot of concern. I plan to keep the max jump starter vole in the below 15v range or even lower until this risk it better understood- just to be safe.

[@koyamamoto5933]

Regarding 450H+: If the 12V battery is dead but the drive battery (high voltage) still has significant charge, then "jump starting" seems to be a bit of a misnomer. Aren't we just supplying enough power to the 12V system to allow the computer & other 12V subsystems to initialize & get to the "ready" state. At that point, wouldn't the DCC be fully functioning and providing power from the drive battery to the 12V systems? How can there be surges or other inductive effects that burn the control computer? In the case of fully ICE engines, then I suppose the 12V starter motor could cause some under/over-voltages that burns the control computer, but the hybrids & plug-in hybrid really don't have a 12V starter motor. Meanwhile, if the drive battery is discharged, can you even start the ICE with only a 12V battery? Perhaps Toyota is not fully disclosing what is actually going on here so hypothetical work arounds may not actually be safe. Personally, I like the idea of tying into the lead acid 12V battery for the "jump start". Maybe run leads from the 12V battery to a quick disconnect so we can either "jump start" or attach a battery maintainer?

[@mikebedford4362]

@@koyamamoto5933 Mmm… That’s deep! For me if the cars dead and in my case even the doors wouldn’t open (stupidly I’d left it on all night!). Mechanically opening them with the manual key, crawling in to the back seat and in to the trunk, removing the battery cover and connecting the leads and voila! A ready state, then turned the engine on to best charge the 12v battery. (There’s a shortcut battery connection under the bonnet but even with Lexus instructions over the phone it wouldn’t work) 3 days ago I returned from a 5 week trip away where the vehicle wasn’t started or touched and it started seamlessly first try!

[@lsft]

This is the 4th generation hybrid system which was not designed to power the DC to DC converter first. My understanding is the 5th generation changes it and will start the DC to DC before anything else so that the 12V need is less. They do need to find ways to charge the 12V from the traction battery to reduce the 12V dead battery issue. But they don't tell us much about what is happening unfortunately.

[@AbdulmajeedElshawa]

Hi and thank you for the heads up.. My question is how about using the portable power boosters directly on the 12V battery at the back of the car.. would that be ok? Thanks

[@wwdd83]

that's what i have been doing to my 2022 nx 450h+ and it works perfect

[@mikebedford4362]

I had to jumpstart my 450 a couple of months ago. The roadside service guy was in contact with Lexus and they said the safest way to jumpstart is to open the trunk and attach directly to the battery terminals in the battery under the floor. It started straight away.

[@tysonong5191]

@@wwdd83 i did this with my 2024 nx 450 and it worked as well

[@MrUKokot]

​@@mikebedford4362How do you open the trunk when the battery is dead?

[@lsft]

Yes that would be ok. That was what I did the first time.

[@ericdelrosario6779]

Can you also show how to jumpstart the Lexus GX460 using conventional battery-powered jumpstarters and the Autowit (battery-less) Supercapacitor? Thanks for your incisive video. Appreciate it. 🇨🇦

[@lsft]

The GX is very easy. The negative is just beside the 12V battery. You would notice that there is a metal piece that is bend 90 degrees between the engine and the battery. You clamp the negative there. s3.amazonaws.com/lexus.site.tci-prod/lexus/manuals/OM60R43U/OM60R43U.pdf Page 570 shows the place where you should clamp the negative.

[@kamcg1049]

If you were using the jump start units (like the NOCO in the video) would it not be easier to attach these to battery posts on the 12V battery in the trunk (in my case of RX350H) for example? Or am I missing something? Thank you for the video.

[@lsft]

You will need to open up the trunk or claw in to access it. it's easier to open up the hood to boost. But if you can do it from the trunk, that would work as well.

[@kamcg1049]

@@lsft Thank you.

[@lsft]

@kamcg1049 my pleasure

[@vincentcheng5709]

was the cable that comes with your NOCO sufficiently long to do the job under the hood ?

[@lsft]

If you follow the manual and clamp the engine, it won't be long enough

[@RickA-Z]

Is there anyway to get an extension cable for the Noco?

[@lsft]

@RickA-Z I have not found any extension for the booster. It comes with a 23" cable as part of the booster.

[@fwca1388]

If Noco just starter is turned off, then connect the cables to the battery terminals. Next, turn on the Noco, will there be a spark this way?

[@sometimesfirstsometimeslas4908]

Technically the current NOCO will not supply any volage/current unless all the connections are correct. This is a manual "override" boost mode, but that is only needed if the battery voltage is very low (in the 3-4 volts range). And even when you do use it , it is no more risk then using cables, since they demand corrections also. Bottom line- one should never have a spark in normal use without the "override" on a NOCO. And most LI jump starters have similar protections also. Note: while discussing hybrid jump starting. One should never use the Toyota hybrid to jump start another car, it can damage the hybrid system, since the hybrid system is not designed to supply the 12v high current to start most ICE 12v starter motors. I think the current hybrid amp output limit is in the 100 amp max ballpark range.

[@lsft]

Well said. Thanks for replying. Using Noco boosters they typically do not create any sparks.

[@thisduderockz]

Has Toyota/Lexus provided no solution or fix to the 12volt Battery issue? i really want to buy a Lexus NX Hybrid but not with this 12v Battery issue. and trickle charging it every night is not an option. This shouldnt be happening.

[@lsft]

@@thisduderockz You wouldn't need to trickle charge every night. Maybe once every 2-3 weeks would be ok. Plus if you drive a lot of longer distances it should be ok. I don't know if they have fixed the issue yet, but really need to see if other ppl report issues or not. I know that they have recently updated the mobile app to pull the car less and that definitely would help, but I don't have a definite answer to your question.

[@robb8773]

Why can't you clamp the jumper to the negative terminal of the battery?

[@lsft]

Depends on what model you own. If you have the NX250/350 the 12V battery is in the front. If you are driving a hybrid it's in the trunk. There is no harm to clam the negative if it's in the trunk, not for a hybrid under the hood you only have a positive and don't have a negative.