Something is short on my van, but what?

[dicky96]

Bit of an outside chance this, as it is auto electrics rather than electronics

But could anyone suggest how to diagnose this problem?

I have a Nissan Vanette Cargo 2.3D built 1999. One of the great things about living in a climate where is almost never rains and the night minimum temperature never goes below 12C, is that vehicles don't rot away. In fact the version of an MOT here they don't even check for corrosion from what I have seen (or for other non-essential accessories like windscreen wipers or fog lights lol)

Anyway. Thursday afternoon all was fine with the van. On Friday morning I found the battery was completely absolutely totally flat, though nothing had been left switched on (lights). The battery is six months old.

The battery read 0.05V on the van and 4V once removed. I left it standing and after 30 mins it came back up to about 6V by itself. I then used a my bench power supply with constant current/constant voltage modes to gradually coax the battery back up to charge, never going over 4A charging current and mostly under 2A – it now reads 13V without the charger, after standing a while. Fully charged should read 12.9V apparently. I am not sure the battery is any good now though as the integrated green ‘charged' LED in the battery is not illuminated.

I thought I may as well try it anyway, but before fitting it, I measured the resistance from the big heavy +'ve battery cable on the van to chassis. It reads almost short circuit, around 0.3 ohms. So that probably explains what caused the battery to totally discharge.

I would have expected that sort of fault to blow a fuse somewhere, rather than draining the battery but obviously it hasn't as the short is still there according to my DMM.

I could prove that short further, and whether the battery really does have some charge in it, if I go get a 12V bulb and connect it between battery +'ve and the big battery connector cable, though that would mean me walking 45 mins round trip to the workshop and back to go get a bulb and a bit of wire.



Any suggestions?

[Curious.George]

Re: Something is short on my van, but what?

Bit of an outside chance this, as it is auto electrics rather than electronics

But could anyone suggest how to diagnose this problem?

It's possible that you have a short (to chassis) upstream from the fuse block.

BUT... in the event that the fault lies DOWNstream from the fuse block, it (the fuseblock) gives you an easy way to sever loads from the battery.

Pull all of the fuses, one at a time, while watching to see when/if the short clears. You should start with the larger fuses as 12V/0.3ohm = ~30A... if there IS a partial short (i.e., a 0.3 ohm load) on one of the circuits, then you can imagine it will likely NOT be on a circuit that is fused for less than 30A (else the fuse would have opened and "cleared" the short!)

[Actually, a fuse may resist opening at it's rated current for a very long time so I'd guess any fused circuits smaller than ~20A would be above suspicion]

With a wiring diagram (google will likely find one for you as many individuals publish stuff for cars that they've "acquired" by whatever means), you can see where all of the connection points are in the vehicle. I.e., how you can open CONNECTORS to isolate the wiring upstream from the fuseblock (if you were unable to find the problem by pulling fuses).

Note that the starter isn't typically fused but is isolated from the battery by the starter relay (which drives the bendix which drives the actual starter).

You might also find something like a shorted winding or diode bridge INSIDE the alternator.

[petehall347]

Re: Something is short on my van, but what?

looks like maybe shorted diodes in the alternator .. remove thick wire off back of it and check ohms again across battery wires .

[dicky96]

Re: Something is short on my van, but what?

OK
So the fuse box is right next to the battery

I pulled out most of the fuses one by one apart from the two little 15A ones

They didnt' want to come out without a fight, but the last blue one which says Engine main 100A refuses to come out, all I managed to do was break up the plastic body of the fuse though the connector bit in the middle is still intact (see pics) I think if I try any more to get this out I wil just break the ceramic fuse link in the middle.

Anyway removing any of those, I still have a short from the +ve battery lead to chassis. There are two smaller wires that also go to the positive terminal but I disconnected those and they read high resistance to chassis so the problem is not those

The alternator connector I'll have a look in the morning.

Whatever went wrong happened after I parked up the van on Thursday afternoon - it drove home just fine and I didn't have any flat battery problems before. Nor was the ignition light on when i was driving. I am puzzled how something like this could happen when the van was just sitting there.

[stj]

Re: Something is short on my van, but what?

alternator is always the first suspect.
followed by the stereo and ecu because both are across the power - but alternater failure is very common.

[sam_sam_sam]

Re: Something is short on my van, but what?

Also one possible is that your engine starting switch might not be turning off completely I have seen this a few times

So do not rule this out

I have also seen alternator ( diodes or voltage regulator failure) are very common

I have stereos have issues but not as common

Brake light switch failure is more common

The interior light timing controller failure is also common problem
Glove compartment light switch failure is also common

This is very rare but I have heard of it engine computer failure

Head light timer controller failure head light not turning off in certain amount of time

One note do you have a bench power supply that you can hook up instead of the battery
Only do this if you can adjust the current see what current you have

If you do not have a bench power supply do you have a DC current clamp on meter you use the car battery but depends on how much of an arc you get when you put the terminal to the battery to weather or not you can do this

I hope this helps

[stj]

Re: Something is short on my van, but what?

This is very rare but I have heard of it engine computer failure

not rare in 90's honda's
there is a cap that always leaks in the OBD1 ecu's

[dicky96]

Re: Something is short on my van, but what?

Sorted - it's surprising how a mystery disappears once you have all the evidence

As Sam suggested, I put my bench supply on the battery leads, set to 12.5V 1A, ignition off.

The current limiter kicked in so I decided to wind up the current to see how much of a short I really had. At 3.5A it sent to constant voltage

I had a look around and the brake lights were stuck on. 12.5Vx3.5A = 43W - I imagine they are two 21W bulbs so that makes sense. And the DMM reading the bulbs as short when cold also makes some sense.

I couldn't find the fuse (even googled to see where it is) but I did find a pic of a brake light switch and there it was just above the brake peddle. I disconnected the switch and I now have 0.05A

So that explains why the battery went flat. Just need to fix it now.

[sam_sam_sam]

Re: Something is short on my van, but what?

I am glad you found out what the reason for your dead battery is
Good work

[dicky96]

Re: Something is short on my van, but what?

Hey Sam, I just figured out if I was to go due West from my new house in Playa del Ingles, Gran Canaria I would next make land just a bit south of your house

I think I would come out somewhere around Vero Beach almost 4000 miles away. That is near to you?


Probably there is no coincidence we both put 'sunny' in our locations

27.7606° N, 15.5860° W Playa del Ingles Gran canaria
27.6386° N, 80.3973° W Vero Beach Florida

[dicky96]

Re: Something is short on my van, but what?

Just to finalize this thread

I removed the brake light switch and there was nothing wrong with it. It is NC, and open when pushed. I got my torch and had a good look, and basically the brake pedal, when in the resting position has a little metal tab that holds the switch pushed in (open) and when you put your foot on the pedal the switch goes to the NC position. or at least it should, in my case there is supposed to be a plastic insert/stud in a hole in the metal tab on the brake pedal, and mine had disintegrated. Therefore the switch went NC and drained the battery. I know this because I found some suspicious looking bits of plastic in the foot well.

I fixed this by putting a nut and bolt through the hole in the pedal tab where the plastic thingy should be, then adjusted the vertical position of the switch so it activated properly. Job done.

Now what puzzles me a bit. The sealed lead/acid battery was reading 0V on load and 6V off load (was 4V at first but it recovered a bit after 30 mins).

After a lot of coaxing in CC/CV modes (and about 48 hours) with my bench PSU I got it up to 13.1V but the integrated 'charged' LED did not illuminate. I let it standing for 3 days and gradually the voltage dropped to 12.93V and the embedded LED came on green.

When I put the battery on the van it started fist touch, and did so 4 times as I had stop at few local places- I then took the van for a good 30km round trip run and it has started 3 more times on first touch since so I guess it is OK. But what happened over those 3 days of standing to cause the battery LED to go green? I can only assume some chemical reaction was going on in there. Can someone explain that?

[Curious.George]

Re: Something is short on my van, but what?

After a lot of coaxing in CC/CV modes (and about 48 hours) with my bench PSU I got it up to 13.1V but the integrated 'charged' LED did not illuminate. I let it standing for 3 days and gradually the voltage dropped to 12.93V and the embedded LED came on green.

It's not an LED (unless there have been significant changes to VRLA technology that have eluded me!).

Rather, it's a hygrometer. It is providing a visual indication of the specific gravity in ONE cell of the battery. When it is black, the electrolyte is "closer to water" in terms of SG. "Green" indicates it is closer to the nominal 1.265 for a "charged" battery.

Let it sit, indefinitely, and it will turn black, again!

[eccerr0r]

Re: Something is short on my van, but what?

Are you sure it's sealed? or just maintenance free?

Flooded batteries typical of cars can be maintenance free, but cannot be sealed as they can generate gases while being used. Flooded cells can have "green/black/white" hygrometers which detect the density of the liquid electrolyte - if it's charged, the liquid would be mostly acid which is denser than water, which is what the electrolyte would be when the battery is discharged.

Green means high density electrolyte = acid = charged.
Black means low density electolyte = water = discharged.
White means no electrolyte = air = you had a leak or you spilled the electrolyte from the not-sealed battery.

If it's really a sealed leakproof AGM battery, possibly cylindrical cell, I suppose it could be a fancy unit with its own selftester but I've yet to ever see one. Since there's no free electrolyte in an AGM or gel cell, these density/specific gravity measurements won't work and you have to depend on voltage to determine state of charge.

Incidentally the hygrometers able to detect electrolyte loss is very helpful and you can only guess whether you lost too much electrolyte in an AGM cell, usually due to evaporation or overcharging.

[petehall347]

Re: Something is short on my van, but what?

built in hygrometers always seem to be on the wrong cell as its always an end cell dies first .like it can be green and the battery has a shorted cell ..i can never remember which end cell dies first . only real test is fully charge it then let it sit a day or 2 then do a voltage drop test whilst observing the cells for boiling .
saying the battery supplier i use has a tester that does not put a great load on the battery and will tell you its exact status .

[CapLeaker]

Re: Something is short on my van, but what?

My flooded lead batteries fail to 95% on the outside positive cell. Doesn't matter brand or size or where it sits in. Desulfating batteries that have a bulge seem to die either during desulfation or very shortly after.
The other 5% both outside cells had a bulge and failed to desulfate. So I quit looking at bulged batteries.

[eccerr0r]

Re: Something is short on my van, but what?

I would think that it's fairly equal chance for any particular cell to fail, depends on the welds and plate stabilization. However subject to random vibration I would have to agree the end cells would probably take the most stress, though marginally. The positive electrode also tends to be chemically weaker one I'd suspect, but the mechanical stress is the larger issue.

But yeah the built in hygrometer ends up on cell 2... ideally it should be on cell one near the positive terminal. And thus having the positive terminal closer to the center of the car would extend battery life ever so slightly...

[stj]

Re: Something is short on my van, but what?

outside cells are more exposed to temperature swing

[dicky96]

Re: Something is short on my van, but what?

Sorry guys it is my wrong terminology that caused the confusion. The battery will be maintenance free then - I just called it sealed as it does not have the little screw in covers where you can add distilled water

The green thing jut looked like a faint LED at the bottom of a narrow hole to me. It does indicate green/white/black. Clearly I have now been educated otherwise

I don't think temperature stress will have much of an effect on the battery - it's under the bonnet but the van has a central mounted engine (under the front seats). Out temperature is always between 35C (95F) summer day and 16C (61F) winter night, all year unless we get a summer Calima when it can hit 45C/113F, or an exceptionally cold winter night when it can get as low as 12C/54F.

OK still I wonder - the battery charged to 13.1V but the hygrometer was black. Then after a couple days of leaving the battery standing with nothing attached to it, the hygrometer went very faintly green and the voltage dropped to 13.0V

Then after another day it went green and the voltage was 12.93V

So quite obviously, something was going on inside the battery while it was standing for three days connected to neither load nor charger - and that is what's puzzling me.

The van started again this morning first touch so it looks like the battery survived the abuse.

[Curious.George]

Re: Something is short on my van, but what?

I don't think temperature stress will have much of an effect on the battery - it's under the bonnet but the van has a central mounted engine (under the front seats). Out temperature is always between 35C (95F) summer day and 16C (61F) winter night, all year unless we get a summer Calima when it can hit 45C/113F, or an exceptionally cold winter night when it can get as low as 12C/54F.

Here (AZ, USA) the heat EATS batteries. After about *3* years, encountering ANY starting problems means: "replace battery". Suppliers don't even bother to TEST the battery as they know this to be the case.

As most batteries have prorated warranties (age determines how much of the batteries cost you are credited with), the 36 month number is significant: one usually gets 100% of the battery's price refunded in this period.

OK still I wonder - the battery charged to 13.1V but the hygrometer was black. Then after a couple days of leaving the battery standing with nothing attached to it, the hygrometer went very faintly green and the voltage dropped to 13.0V

The voltage you are reading is the SUM of the 6 cells voltages. So, the cell in which the "magic eye" is placed might have a poor state of charge (low cell voltage) while the others may have a GOOD (even HIGH!) state of charge. The net result is what you see as the "battery voltage".

It's chemistry. You're making a "solution". There's nothing to "stir" the contents of the battery (electrolyte) so you have to wait for the concentration (of "acid") to come to an equilibrium throughout the battery before the "magic eye" will "see" the increased specific gravity. As the cells are physically isolated (electrolyte from one cell can't mix with that of another cell), you are waiting for electrons to migrate between cells to "distribute" the charge (which manifests as specific gravity).

Then after another day it went green and the voltage was 12.93V

Remember, voltage is only an approximate indication of "state of charge". The specific gravity is more indicative of the battery's health.

I only purchase "fillable" batteries and assume the responsibility for keeping them topped off (lots of evaporative losses, here). In return, I can look at the specific gravity of each individual cell (with a real hygrometer). I record these in my cars' log books so I can see if I'm having a problem with a particular cell BEFORE it affects the battery as a whole.

[eccerr0r]

Re: Something is short on my van, but what?

I should have tested my batteries individual cells as a I replaced them. Not sure if my climate has "extreme" temperature changes but it goes from -20C to +38C around here over the year with some outliers. The highs are not as high as some places in the world, but it does get somewhat chilly. However I do tend to get my 7 years on my car starting batteries, and it's been fairly consistent.

Also note that underhood temperatures get quite hot, though unsure if it's a straight temperature over ambient or not. Though cold is still cold for reaction speed (cold cranking amps), high temperature is bad - for electrolyte loss. Then also the other problem is vibration causing sloshing and spilling of electrolyte as well as microcracks in the plastic near the terminals causing small bits of electrolyte to leak out and cause corrosion... Make sure your battery tiedowns are tight to extend the life of your batteries!