Flat battery

[MattS]

Haven't driven the NSX for about a week and it seems to have a flat battery now. (This happened a few weeks ago too and then I jump-started it from another car and drove it around for an hour or so to charge it).

Thought I would take the battery out to check its condition and either replace it or charge it fully using a charger. Problem is the alarm goes off when I disconnect both or either one of the battery terminals = upset neighbours! Needless to say, the battery is still in the car and uncharged.

Does anyone know how I can remove the battery without triggering the alarm system? The handbook strongly advises against charging the battery while still connected to the car.

Thanks,

Matt

[MattS]

Panic over... Amongst all my NSX stuff that I inherited from the last owner, there is a small key. Lo and behold, this fits a small unlabelled black box in the engine compartment (towards front,driver's side) and when turned anticlockwise turns the alarm off. The immobiliser system still seems to work.

The battery's now out for charging.

I might actually leave the alarm turned off (but the immobiliser on) to see if this prolongs the charge life..

Happy New Year to all,

Matt

[DamianW]

Check the thread "trickle charger for battery". I leave my NSX plugged into an Optimate charger and its yet to fry anything Saves a lot of grief with flat batteries if you don't use it much.

[mcibuk]

i still havn't got round to fitting my Accumate but hope to do so in next week or two.
Damian - with the Optimate can you keep your car "alarmed"? With Accumate on TVR the alarm had to be switched off as the trickle charge (change in voltage) would set off the alarm system.

[DamianW]

i still havn't got round to fitting my Accumate but hope to do so in next week or two.
Damian - with the Optimate can you keep your car "alarmed"? With Accumate on TVR the alarm had to be switched off as the trickle charge (change in voltage) would set off the alarm system.

Yep certainly do. I leave the bonnet on the catch so there's enough gap for the wire to go in and then I lock the car with the remote and it seems happy.

[mcibuk]

Yep certainly do. I leave the bonnet on the catch so there's enough gap for the wire to go in and then I lock the car with the remote and it seems happy.

I need to fit the Accumate and try it! Could be that it works differently than your "Optimate" or that voltage drop is different on NSX than it was on my TVR. Either way i need to know!
Thanks

[Bonners]

The battery's now out for charging.

Matt

Matt - is it just a case of removing the spare wheel bracket and then a few bolts to get the battery out? Looks a bit of faff so thought I might just get the car recovered - free anyway - and get my local dealer to charge/swap it out.

Mine appears to be totally dead, although only 1-2 years old, any chance it could be recovered? Foolishly used one of my motorbike trickle chargers and it clearly wasn't up to the job of keeping the battery charged.

[Kaz-kzukNA1]

Hope MattS won't mind my replying as OP was from Dec 2004, 17-18 years ago.


Don’t know the spec of your NSX but the basic is the same as above diagram unless you have the special model.


The manufacture warranty of the battery tends to be just 1 year.

However, the vendor or the Honda dealer would extend it to few years.

If you have the proof of the purchase, contact the seller and see whether it is still covered by the warranty or not.


If you are using the ordinary lead acid battery, then anything below 11V is less than 50% capacity left.

Anything below 8V while cranking, you won’t be able to start the engine as ECU has minimum required voltage.


If you are using intelligent battery conditioner such as CTEK, Optimate, etc, it has minimum voltage threshold of about 2.0 - 3.0V in order to trigger the conditioning sequences.

If your battery voltage is really low, try connecting another battery in PARALLEL to exceed the minimum voltage requirement to force the re-conditioning process.

If you can't even crank the engine, your battery may need de-sulphating phase but may never be able to recover the full capacity even if when fully charged.


If you know what you are doing, you could connect your battery conditioner at the jump start terminal at the Eng bay without taking the battery off the car.


Just make sure to keep the battery in healthy condition.

If jump start the car, you are forcing the altenator/ACG to work really hard to charge the flat battery while running the engine.

This could lead to new issue of alternator failure as the rectifier and other parts get so hot.


Kaz

[Bonners]

Thanks Kaz, hadn't realised the original post was so old. Mine is a Gen 1 from 94 (I think). No crank and not even any lights. I tried using leads at the weekend and that got power going to car, hazards came on etc. but still not enough to get the car to turn over. It was an Optimate 4 I was using, works fine on the motorbikes but good enough for a car battery?

I did think about towing her with my mower up a hill right beside my house (private road) but you're saying that could cause further problems right?

I'm not the most technical guy but 5 bolts I can manage so I'll take the battery out and see if I can get a local shop to rejuice it. Bigger issue is hoping the old back can bend enough to heave the battery out, doesn't look like the easiest thing to do. Thanks again.

[Old guy]

First off, check the battery cable clamps that connect to the battery posts. Honda clamps suffer abuse poorly and it is not uncommon for over tightening of the clamp to result in damage to the clamp which results in a connection failure and no start condition. After tightening, if you can twist the clamp on the post you are going to have to fix / replace the clamps.

Conventional lead acid batteries are damaged by deep cycling. If the battery has been repeatedly discharged to the point of being flat you have shortened its life and are likely in need of a replacement.

I tried using leads at the weekend and that got power going to car, hazards came on etc. but still not enough to get the car to turn over. It was an Optimate 4 I was using, works fine on the motorbikes but good enough for a car battery?

I am confused by that statement. Did you try to use the Optimate to start the car? That will never work. The Optimate has a current rating of 1 amp and the starter probably draws 80 - 100 amps when cranking a high compression engine like a C30 / C32. If you were just using the Optimate for maintaining the battery that should work fine. If 'using leads' meant using battery jumper cables to connect the battery in another car to the jump start terminals in the engine compartment that should spin the starter motor just fine. If the starter motor failed to spin using jumper cables then you have some other problem.