Charging and starting issue

[C.Rogers]

It seems that for some reason my battery isn't holding a charge.

It seems that i have to plan about a day in advance before i take my fantastic car for a drive. The reason being i have to put the battery on charge because it won't start.

Once it has had a charge over night, it will start first time. If i leave it overnight or for a day or so, there isn't enough charge in the battery to fire her up again.

There is a click as if the starter is trying to turn the engine, but hasn't got the oomf to get her started.

I have a couple of thoughts...

1, the engine has only done 450 miles and may still be tight?

2, the alternator isn't up to the job - When running, the voltmeter is reading 14v

3, the battery isn't up to the job. - The size of battery is what i was recommended.

I bought the complete engine (turn key) from Fast Co in USA.

Any suggestions on how to solve this really annoying issue would be great. The weather (touch wood) is starting to improve and really don't want to have to charge or jump the car everytime i want to use it.

Thanks in advance.

Colin

[Andy302]

Id look at a few things.

1) Why did it go flat, do you have a current drain with the ign switched off? I dont know so much about Cobra electrics (a little way off yet) but in mass pro I wouldnt want to see more than 20mA with the systems shut down. Keeping in mind that tin tops have many ECU's which require backup power I would expect a Cobra to draw virtually nothing at rest.

Measure the current draw by inserting a multimeter set to measure amps on the 10A range in series with the negative lead. You should not read more than 0.020A say. (dont start the car or turn on any load over 10A or your meter fuse will pop!)

2) Has the battery gone totally flat and if so for how long was it sat? To be honest if its gone below 10V then its flat. If sat flat for more than 2 days then forget that battery, sulphation will have started and I dont know of any commercially available "home" style chargers that can successfully recover a sulphated battery. The charge profiles are specialised and tend to only be found in £200 plus professional chargers (Midtronics etc)

3) On the alternator side check its output with loads on, 14V at idle is one thing but if it drops off significantly when you put the headlights on then that could your problem area. Ideally you should measure current and voltage from the alternator but without a current clamp you wont do that at home.

4) Battery capacity is unlikely to be an issue as long as the car starts with a fully charged unit, once the engine is running the alternator should power the car and charge the battery back up.

Hope that helps.

[demus]

Hi Colin,

If the voltmeter is reading 14 volts, then I would think it is charging ok.

For a start it may be worth checking all of the connections, at the battery and on the starter motor, check any earth straps too.

How old is the battery, the symptoms do suggest the battery is a bit tired, but if its new then its more likely to be a bad connection.

[craggle]

Do you disconnect the battery when you leave the car?

If not there could be something in the car that is draining power constantly. You could try an ammeter on a multimeter between the battery and the positive cable to see how much power is being drained when everything is off.

If you do disconnect the battery overnight and it still ends up being flat then the battery is duff. I have a removable key battery cutoff in my car that disconnects the battery whenever I leave it. Good security measure too.

The click you can hear is the solenoid on the starter moving forward but then there isn't enough power to turn the engine. Sometimes this causes the solenoid to disengage again, then try again in rapid succession. Sounds like a machine gun under the bonnet!

Craig.

[wilf]

You need to check earth circuit, voltage at battery terminals with engine off and with it running (and ignition light out).

Ignore the reading on your voltmeter - these are so inaccurate that they pretty much only tell you if the battery is flat or not. Of course, the reading on your dash voltmeter should still go up between sitting with igntion on and engine not running, and engine running. If it doesn't, there is no charging going on.

[JonnyT]

If its the same battery that you've had while building the car its probably a bit knackered. Might be worth replacing it or borrowing from another vehicle. Easiest thing to check first.

Jon

[C.Rogers]

Thanks for all of the suggestions everyone. Some good ideas there and points to start.

The battery is new (i got it when we finished the build). Look slike an ammeter on the battery when everything is off is the best place to start.

My son went out in her today and after a brief charge earlier she started with no probs. After a half hour drive and then stood for a couple of hours she started again with no effort at all.

We did have a battery cut off switch but took that out. If it seems that something is draining the battery when everything is off, i might have to put it back

Thanks again.
Colin.

[C.Rogers]

Thanks again for the suggestions.

Last time i took the car out (last saturday) i disconnected the battery to see if that proved anything.

My Son popped round to mine yesterday and tried starting the car and she fired up on the button.

This means that there is some kind of power drain on the battery. There is an immobiliser on the car and the clock in the dash, but these shouldn't drain the battery so much that it doesn'e start a day later should it?

My Son has borrowed an analogue ammeter off of my dad (i do not know a huge amount about the electricity side of things) to try and trace it back. We did try a digital meter, but it wasn't accurate enough so thought we'de give a good old analogue meter a go.

I'll keep you posted.

[lutman]

Originally Posted by C.Rogers

Thanks again for the suggestions.

Last time i took the car out (last saturday) i disconnected the battery to see if that proved anything.

My Son popped round to mine yesterday and tried starting the car and she fired up on the button.

This means that there is some kind of power drain on the battery. There is an immobiliser on the car and the clock in the dash, but these shouldn't drain the battery so much that it doesn'e start a day later should it?

My Son has borrowed an analogue ammeter off of my dad (i do not know a huge amount about the electricity side of things) to try and trace it back. We did try a digital meter, but it wasn't accurate enough so thought we'de give a good old analogue meter a go.

I'll keep you posted.

Have to agree with the others in that the power drain is obviously causing the start problem.
Perhaps to put the cut out switch back in the battery circuit. Only problem then is that the clock will need adjusting every time and the immobiliser is inoperative.
Other way is similar to other threads in that leave all well alone but have a trickle charger plugged in whilst the car is parked up.

[Clive]

Originally Posted by lutman

Other way is similar to other threads in that leave all well alone but have a trickle charger plugged in whilst the car is parked up.

You will need to find the cause of the problem otherwise you will have problems if you are away from home for any length of time such as a weekend away. You will end up paranoid!
Try connecting an ammeter between the battery positive terminal and the lead, then if it is showing a discharge, disconnect each electrical componnent in turn until the ammeter reads zero and you have found the problem.
(It might not be a wiring fault, there might be a faulty component)