Battery Dead Overtime or Main Relay is Broken?

D

dancr22

Registered Member
Joined
24 January 2020
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13
Location
San Jose
All,

I have a 97 that I usually drive every two weeks or so. When it's more than two weeks, the car usually wouldn't start, and I think it's because the battery is dead. Not sure if it's a dead battery or the main relay switch. The status light indicator turns on when I switch the key to ON position. Once I twist the key to start, it cranks but becomes the noise becomes weaker and the status lights turns off. I think it's the battery.

If it's the battery, does anyone have this problem? After two weeks or so, the battery just dies. I'm wondering if there's something ya'll might know that could be draining the battery while off. My '00 ITR doesn't have this problem.
 
On a non Zanardi version, the original sized battery should allow the car to sit for two weeks and restart successfully. That assumes that the car is stock - no after market security system or stereo system. If the car has been fitted with a light weight battery it will likely not make it two weeks. How many times have you allowed the battery to discharge to the point that it will not start? Each time you deep cycle a battery you shorten its life. If you have deep cycled the battery four or five times the battery may be at the end of its useful life, particularly if the battery is already 4 - 5 years old.

If you can jump start the car with an external battery / booster pack, then the main relay is just fine.

The dash cluster has a voltmeter on it. Watch the voltmeter as you engage the starter motor to crank the engine. If it is dropping below 10 volts you have a battery that has exceeded its best before date or your battery post clamps have failed (or both). Loose battery post clamps are a not uncommon problem on the NSX caused by people overtightening the clamps and stretching them to the point that they no longer tightly grab the battery post.

Have your battery load tested. If it fails the load test, install a new full sized battery and check the condition of your battery post clamps. If the car will not restart after two weeks and you do not have any aftermarket stuff on the car, then you may have a high parasitic load due to an electrical problem in the car. However, that would be super rare.

My stock 2000 NSX with the original sized battery will restart just fine after sitting for two weeks
 
Thanks. My car is bone stock.

I can jump start the car with an external battery / booster pack, so the main relay is just fine.

I think with two weeks, the car usually can start, but if it's after two weeks then it tends to die. It's not all dead, but mostly dead (i.e. the clock is still good and engine lights are on, but not enough power to to turn the engine on). What's annoying is that when this happens, the O2S, CAT, and EVA data are reset, so it's a pain to get them back for the smog check.

Is more than two weeks expected? Does anyone use a trickle charger? Any recommendation for the brand.

My experience with trickle charger in the past is that it didn't work with my ITR.
 
A bone stock NSX has about a -0.5A drain when it is shut off and locked. This is mostly due to the security system, but there are also other modules like the ECU and radio that use battery power to keep their internal memory active. Two weeks on a healthy battery is usually not enough to drain it. That said, most NSX owners use a battery maintainer when they put their cars away for an extended period. It sounds like your battery is dead. I'd get a new one and keep it on a maintainer when it is going to sit for more than a couple weeks.
 
Honcho said:
A bone stock NSX has about a -0.5A drain when it is shut off and locked. This is mostly due to the security system, but there are also other modules like the ECU and radio that use battery power to keep their internal memory active. Two weeks on a healthy battery is usually not enough to drain it. That said, most NSX owners use a battery maintainer when they put their cars away for an extended period. It sounds like your battery is dead. I'd get a new one and keep it on a maintainer when it is going to sit for more than a couple weeks.
Click to expand...
Thanks. Any recommendation for the battery maintainer?
 
Honcho said:
A bone stock NSX has about a -0.5A drain when it is shut off and locked. This is mostly due to the security system, but there are also other modules like the ECU and radio that use battery power to keep their internal memory active..
Click to expand...

I think Honcho might have slipped a decimal point. About 4 -5 years ago the issue of dead batteries and parasitic current load came up on the forum. Out of curiosity, I went out and hooked my Fluke digital multimeter in series with the ground cable on the battery. On my 2000 with keyless entry the quiescent unlocked current was a around 0.05 amps . The surprise was that when I locked the car with the security system armed the quiescent current remained at 0.05 amps. Unlike building security systems that continuously circulate current through the perimeter contacts, the NSX system must rely on voltage supervision which has a lower load. So, storing the car armed or disarmed would not appear to materially alter battery drain.

When you first connect the battery there is a high parasitic current of about 0.150 - 0.200 A. This tapers to about the 0.05 A range in less than 1 minute. That is what I measured with my multimeter on my car.

Short answer, with a good battery on a stock car you should easily be able to go 2 weeks between restarts without a battery tender.

I think my Audi A4 is probably an all time winner for parasitic load currents. On initial shut down the parasitic load current can be around 8 amps because of things like the turbo after run coolant pump. It does taper off after a few minutes; but, still remains fairly high because of crap like the 4G module and other stuff. CTEK chargers are sold by and highly recommended Audi if you don't use your car extremely regularly.
 
dancr22 said:
I had it plugged its battery connected to the trickle charger, and the battery still went dead. Could be the brand of the trickle charger (or the battery).
Click to expand...
If you have deep cycled the battery on more than a few occasions sulfation occurs and the battery may no longer accept charge. Some battery chargers and maintainers have an anti sulfating function (my CTEK for my Audi A4 claims to have an anti sulphating cycle). I don't really now how well these work.

Short answer, if the battery has been deep cycled and has developed sulfation at the plates it may be a goner and no amount of time on a trickle charger may fix that problem. AGM batteries are said to be more tolerant of being deep cycled and more resistant to sulfation than conventional flooded cell batteries - that is internet wisdom so treat appropriately.
 
Old Guy said:
Loose battery post clamps are a not uncommon problem on the NSX caused by people overtightening the clamps and stretching them to the point that they no longer tightly grab the battery post.
Click to expand...
Is there an easy fix for the loose battery clamps? My battery post clamps sometimes slide off and the bolts cannot be tightened further.
 
dancr22 said:
All,

I have a 97 that I usually drive every two weeks or so. When it's more than two weeks, the car usually wouldn't start, and I think it's because the battery is dead. Not sure if it's a dead battery or the main relay switch. The status light indicator turns on when I switch the key to ON position. Once I twist the key to start, it cranks but becomes the noise becomes weaker and the status lights turns off. I think it's the battery.

If it's the battery, does anyone have this problem? After two weeks or so, the battery just dies. I'm wondering if there's something ya'll might know that could be draining the battery while off. My '00 ITR doesn't have this problem.
Click to expand...
My '91 is showing the same signs and symptoms. If I use the CTEK maintainer, it starts just fine and allows me to drive the car and get home without using a boost battery pack.
I checked my records. my battery is 11 years old. Time for a new one.

comments: when a maintenance free battery goes to zero or close to dead, it will never really be same, even after a reconditioning. It will have less capacity going forward. I use a 24F battery group size. (spec'd for the automatic NSX) It will give you more time between drives and weighs about the same as the standard battery group 35. (spec'd for the manual NSX)
 
AR1995 said:
Is there an easy fix for the loose battery clamps? My battery post clamps sometimes slide off and the bolts cannot be tightened further.
Click to expand...
What battery are you using? It's possible an aftermarket battery has smaller posts than the OEM Honda battery. If you're concerned you can get a shim to take up some space:


Might also be available at a local auto parts store. I think on cars pre-2000ish the battery posts were all the same size, and on newer batteries they often have a smaller negative post so people don't put them in wrong. Could be part of the issue using a newer battery.
 
AR1995 said:
Is there an easy fix for the loose battery clamps? My battery post clamps sometimes slide off and the bolts cannot be tightened further.
Click to expand...
Ranked in terms of low to high cost and low to high effort and durability the fixes are

1) easiest fix with lowest cost - I jammed a small finishing nail between the post and the clamp to tighten things up. Good enough to get me where I needed to go.
2) Battery post shim

General PDP Template

www.canadiantire.ca www.canadiantire.ca
3) Re terminate the battery cables with new clamps. This is not the easiest thing to do in part because the positive battery cable is very large (#1 or 1/0 - can't remember). The new terminals need to be crimped on to the wires which requires a big ass crimper working in a rather tight spot.
4) Replace the positive and negative cables. This is an option for the negative cable which is relatively short. I think Ben from Daisey was making a nice replacement for a reasonable price. The positive cable is really long and quite difficult to replace which makes for a high parts cost and high labor cost - default back to option #3.

The OEM battery cable clamps no longer clamp because they have been overtightened and have stretched. At some point the stretching results in tearing of the metal. I have a photo of mine someplace showing the tear before I re terminated them. Once they have reached that point they are history and will never grip the post tightly even with a nail / shim. I believe that Honda makes their battery post clamps from re cycled soup cans. My 2003 Pilot had the same clamps as my NSX. The clamps will last if you are not ham-fisted when it comes to tightening - the Pilot's clamps were still fine 18 years later when I sold it. However, once stretched the end is near. Post shims may work for a while; but, you should plan to put new clamps on the cables as the lowest cost permanent fix.
 
warrenw said:
My '91 is showing the same signs and symptoms. If I use the CTEK maintainer, it starts just fine and allows me to drive the car and get home without using a boost battery pack.
I checked my records. my battery is 11 years old. Time for a new one.

comments: when a maintenance free battery goes to zero or close to dead, it will never really be same, even after a reconditioning. It will have less capacity going forward. I use a 24F battery group size. (spec'd for the automatic NSX) It will give you more time between drives and weighs about the same as the standard battery group 35. (spec'd for the manual NSX)
Click to expand...
Warren

11 years - that battery does not owe you anything! I think that qualifies as death due to old age.

My previous battery was a 24F which I replaced at 10 years without ever using a battery maintainer on it. I replaced it with a group 35 AGM battery. Group 35 because now being an even Older Guy the 35 was slightly easier to replace being a nudge smaller and a nudge lighter (about 7 lb for the AGMs I was looking at). AGM because I went to some effort to clean up and repaint my scabby looking battery hold down and AGMs are sealed (at least until something goes wrong).
 
Old Guy said:
Warren

11 years - that battery does not owe you anything! I think that qualifies as death due to old age.

My previous battery was a 24F which I replaced at 10 years without ever using a battery maintainer on it. I replaced it with a group 35 AGM battery. Group 35 because now being an even Older Guy the 35 was slightly easier to replace being a nudge smaller and a nudge lighter (about 7 lb for the AGMs I was looking at). AGM because I went to some effort to clean up and repaint my scabby looking battery hold down and AGMs are sealed (at least until something goes wrong).
Click to expand...
I stay away from AGM batteries because AGM batteries are designed to require 14.6v – 14.8v when performing a full charge from a state of discharge, whereas standard lead acid batteries need 13.8v – 14.4v, hence this is what most onboard chargers (alternators) are designed to deliver – not the 14.6v – 14.8v that AGM requires.
my NC1 does charge at 14.7V, and it has an AGM in it.
 
warrenw said:
I stay away from AGM batteries because AGM batteries are designed to require 14.6v – 14.8v when performing a full charge from a state of discharge, whereas standard lead acid batteries need 13.8v – 14.4v, hence this is what most onboard chargers (alternators) are designed to deliver – not the 14.6v – 14.8v that AGM requires.
my NC1 does charge at 14.7V, and it has an AGM in it.
Click to expand...
Warren

You are correct about the AGM requiring higher voltages for charging. To fully charge a partially to fully discharged AGM battery you do need an AGM specific charger Full charge voltages are temperature dependent (14.3 volts at 40C to 15.3 volts at 0 C) and recommendations vary slightly with the battery manufacturer. Float voltages run about 13.4 - 14.4 volts for the same conditions. Most batteries are in light charge to float when the car is running so if you don't significantly discharge the battery during start-up typical charge voltages with a healthy system meant for a flooded cell will probably be OK.

The NSX service manual does not spec a typical operating voltage for the charging system. It does specify a max limit of 15.1 volts (higher than that means a defective regulator) and that with a load of 85 amps the voltage should be 12-13.5 volts. On my 2000, with the air conditioning running / blower on mid speed at idle the voltage measured at the jump start terminal is a nudge over 14.7 volts. Speed the engine up to around 1500 RPM and the voltage rises to 14.9 volts. I don't know what has to be switched on to draw 85 amps from the alternator; but, on my car I expect that 99% of the time I am running voltages high enough to provide full charge on a discharged battery. If my NSX was a winter driver the charging system voltage would be marginal to inadequate to achieve full charge on a discharged AGM battery when the temperature was below 10C.

If you have an AGM battery and you have dodgy battery post clamps that could be an invitation to a short battery life because of reduced charging voltage. A sunny weather driver with an electrical system in good condition and I expect that the AGM will be just fine.
 
centerpunch said:
While you guys are working on your batteries, check that the steel hold down bracket is mounted correctly- the illustrations in the service manuals are WRONG.
.View attachment 182054
Click to expand...
I had to refinish my battery bracket today when changing my battery.
I used paint on electrical tape and then sprayed it with truck bed liner. IMG_3447.jpeg
 

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