Jump Starting another car from an NSX

[sassthathoopie]

I've had a curious and at times worrying morning.

Have been away from home for a week and returned to find the battery in the MX5 drained by the imobiliser system (hasn't been getting much use...)

NSX manual only mentions the car as a receiver not a donor. No negative terminal in the fuse box is mentioned in the manual.

Set up a jump direct from the NSX battery to the battery in the boot of the MX5. In the past I haven't been able to jump start the MX5 if I've attached the negative to the chassis - only if it's attached to the negative terminal on the receiving battery.

First try melted my admittedly not very manly jump leads in a matter of seconds. Repaired them and tried again on the chassis - no good. Assume they are toast.

Went to Halfrauds and bought 25mm leads "suitable for 5.0 litre engines".

Connected to NSX battery, -ve on the MX5 chassis. Still no luck starting and beefy jump leads rubber caught fire. Scary moment as I didn't realise. Sat in the NSX looking in the manual again and noticed flames under the 5's petrol tank :-0

So I'm now off to buy a battery charger and am committed to taking the battery out of the 5 and taking it up to my flat to charge.

Presumably I have an earthing problem - not sure how I'd solve it though.

Would be nice to know how to use the NSX for a jump start without blowing myself up! Any ideas?

[Hagasan]

I've had a curious and at times worrying morning.

Have been away from home for a week and returned to find the battery in the MX5 drained by the imobiliser system (hasn't been getting much use...)

NSX manual only mentions the car as a receiver not a donor. No negative terminal in the fuse box is mentioned in the manual.

Set up a jump direct from the NSX battery to the battery in the boot of the MX5. In the past I haven't been able to jump start the MX5 if I've attached the negative to the chassis - only if it's attached to the negative terminal on the receiving battery.

First try melted my admittedly not very manly jump leads in a matter of seconds. Repaired them and tried again on the chassis - no good. Assume they are toast.

Went to Halfrauds and bought 25mm leads "suitable for 5.0 litre engines".

Connected to NSX battery, -ve on the MX5 chassis. Still no luck starting and beefy jump leads rubber caught fire. Scary moment as I didn't realise. Sat in the NSX looking in the manual again and noticed flames under the 5's petrol tank :-0

So I'm now off to buy a battery charger and am committed to taking the battery out of the 5 and taking it up to my flat to charge.

Presumably I have an earthing problem - not sure how I'd solve it though.

Would be nice to know how to use the NSX for a jump start without blowing myself up! Any ideas?

Best way is to come straight off the battery on the NSX so remove the spare tyre to make it easier and to save accidentally shorting the +ve lead on the metal tyre holder. The NSX negative at the rear is the engine block I think. THe +ve is under a cover in the fuse box. I personally wouldn't draw full cranking current down through the car from the battery to the post in the fuse box.

Simply put your red lead on the +ve NSX battery terminal then the other end on the +ve terminal on the MX5. Then black onto the -ve terminal on the NSX and the other end on the -ve terminal of the MX5 battery.

You might want to start the NSX engine and if there are two of you get your helper to rev the NSX a little then try starting the MX5. Make sure you blip the immobiliser....

It's that easy ;)

[sassthathoopie]

Cheers

I have been working with the spare removed so no worries there. Will go and have a bash. Was just a little spooked after the earlier incident!

[Hagasan]

Cheers

I have been working with the spare removed so no worries there. Will go and have a bash. Was just a little spooked after the earlier incident!

Good luck...

Take a careful look at your leads. Sometimes they only have the metal conducting teeth on one side. Depending on how well they are clipped on it can sometimes be possible to not actually have metal contacting the terminal. When this happens your not connecting the battery across the other one so it "isn't there".

[sassthathoopie]

Well still no luck. Jump leads are contacting fine. I'm on my own so can't rev the NSX and start the MX5 at the same time. I think the 5s gel battery is completely dead. I seem to remember hearing that jump starting won't work with a completely dead battery.

[Hagasan]

Well still no luck. Jump leads are contacting fine. I'm on my own so can't rev the NSX and start the MX5 at the same time. I think the 5s gel battery is completely dead. I seem to remember hearing that jump starting won't work with a completely dead battery.

:( OK, if you have a multi-meter can you check the voltage across the MX5 terminals? With no jump leads connected and then with them connected. Make sure the probes are on the terminals, not the leads.

If the battery is completely flat then you may struggle. If you can connect the leads, then sit in the NSX for 5 mins with it running, leave it running then try starting the car.

With the jump leads connected are your interior lights nice & bright? If not the leads probably aren't making good contact...

[Kaz-kzukNA1]

Hi.
Just some advise for you before going out for the shopping.

Not sure what kind of battery you are using on your MX-5 but as you know, it is stored inside the boot. Therefore, Mazda and several battery manufactures designed a specific battery to avoid hydrogen to sit nicely inside your boot waiting to be triggered by the electric spark and so on :eek:.

By the way, how old is your battery? If it is more than 4 years old or so and it went flat after just a week of no-driving, then it would be better to replace it than recharging it.
It would be very difficult for an old battery that has been drained completely down to empty to recover its 100% performance by recharging it.
Back to the original discussion.


So I'm now off to buy a battery charger and am committed to taking the battery out of the 5 and taking it up to my flat to charge.

So, if you are using the gel type or similar battery, please select the battery charger which can handle this type of the battery. Otherwise, it won't work. A charger called 'Optimate' can handle this type of battery and I use it for my MX-5.

As I don't know the type of your battery, please only charge it outside and at well vented area. The battery can get warm/hot.

One very important thing about jump starting any cars.

Please, please, Do Not connect the GND (negative, -ve, the black cable, etc) jump cable to the battery Negative post of the receiver car.
It is dangerous!!

Always follow the following sequence.
1. Red jump cable on Posi terminal of receiver.
2. The other end of Red jump cable to the Posi terminal of donor.
3. Black jump cable on the Negative terminal of donor.
4. The other end of Black cable to the engine block or chassis frame of receiver.
5. Start the engine of donor car. This is to keep the generator running and avoid draining the current from the battery on donor car.
6. After the jump start, remove the cables in the reverse order.

For the case of NSX, the posi terminal is inside the fuse terminal box with big + mark bolt on it.
The negative terminal is at the throttle body where you can see the ' - ' logo on it.
If you are using NSX as the donor, as long as you are running the engine, you won't be draining too much current from the battery at the front. ACG will balance the direction of the current between the battery and the load.

On MX5, there is a thick black cable coming out of the negative post of the battery terminal. If you follow it, this cable is bolted to the vertical chassis frame. You can use this bolt as your good negative/GND point on MX5.

If you are working alone, then after connecting the jump cable, stay at the NSX and keep the rpm around 1,500 - 2,000rpm for about 5min to charge the battery on MX5. Then, keep running the engine of NSX (idle rpm is fine as you are alone) and move onto MX5 and try to start the engine. If you hear the click of the starter, you may have more chance by repeating above procedure. If you won't get any click, then you better measure the voltage at MX5 and if it is not being charged, then it would be best to replace your battery or you have other issues.


Regards,
Kaz

[Hagasan]

Sorry if I have mislead a little as my posts are very quick whilst at work!! I guess when I know what I'm doing I'm a bit short on out & out complete instructions like Kaz's?

I have never had any problem doing battery to battery direct . I'm guess the danger maybe due to any gasses from the battery potentially igniting but I see this is unlikely....All the same if Kaz says (and I don't have an MX5 to refer too) if there is a specific earth point on the car then yes use this. Are you sure all your connections are all clean etc for good conductivity?

[sassthathoopie]

Thanks very much for all the advice guys. I rang around to find a place that sold Optimates (Bike Dealers are best bet if you're looking).

Battery is now on charge on my balcony. Orange indicator suggests that it was pretty deeply discharged hence why the jump starting was tricky.

Thanks again

Gavin

[Silver Surfer]

My Friendly neighbourhood 'mechanic and engine re-con man' informs me that charging directly from -ve to -ve and +ve to +ve terminals of the battery of the 'donor' and 'receiver' cars can cause severe damage to the 'receiving' cars ECU permanently!!..... :eek:.
The 'receiving' cars' must have the -ve connection on the engine block as Kas has suggested!

SS

[AR]

Whatever you do wear safety glasses if possible, and as said by all others, to the receiver blck. jump leads in some other countries have this proocedure printed on them.

Cheers,

AR

[sassthathoopie]

Battery is currently going through the Optimate's testing cycle. 26 hours on charge - I guess it was pretty flat!

Thanks for all the advice guys

[markdas]

Is it introduction of the now commonplace ECU the problem then, cos jumping from/to battery post to post was always the accepted method. There are some exception, typically cars with digital dash boards (audi URQ, MG Maestro etc) cannot be jumped unless the dash is disconnected.

But, whilst no vehicle electrical expert, whats the difference? The recieveing car has no/little charge and the doner is giving it 12v and the starting current that is likely to see anyway?

Im sure there is a good reason, I just cant see it yet?

Thanks

Mark

[Hagasan]

Battery is currently going through the Optimate's testing cycle. 26 hours on charge - I guess it was pretty flat!

Thanks for all the advice guys

So, did it work? Was the battery ok?

[sassthathoopie]

Battery was fine, but somehow I managed to blow the main fuse. Still £6.21 from a local auto electrician for a new one didn't break the bank! Thanks to everyone for the various suggestions.

[kingsley]

Battery was fine, but somehow I managed to blow the main fuse. Still £6.21 from a local auto electrician for a new one didn't break the bank! Thanks to everyone for the various suggestions.

Just a thought you mentioned that you purchased your Optimate from a bike shop. I had bikes and had an Optimate and it was fantastic. When I sold my bikes I kept it. It would not work on my cars. The reason being the bike batteries had a lower amp hour. I sold it and purchased a CTEK MXS5.0 which works great . I swop it between the Z4 and NSX. May be an idea just to check the amp hour. It will confirm Charge and Conditioner a battery up to ie: 120AH or 225AH etc.

Kingsley

Kingsley