(G) Battery/starting question

Hi, so my uno has been struggling to start of late (cold weather me thinks) - tho sometimes it can take as many as 5 attempts to fire up.
Anyhow, I tested the battery (which I believe is about 10 months old), and found that it is kicking out about 12.85V (which is ok), but that the CCA is only 189 - when it should be 380 (the battery is a yuasa 063 type).
I have not had the battery light come on (I presume this is triggered by a low volt reading).
I tried to charge the battery this morning, but I stopped immediately when I heard the battery bubbling.
Does it sounds like my battery is dead, and could this be the cause of my starting woes?
Btw, I have a mk1 903cc formula 45 (so nothing fancy!)
Oh and one other thing, sometimes when I start up, if my stereo is on, the stereo turns off (and its not connected to the ignition, just wired into the always on 12V supply.

Cheers,

Marko

Try checking your grounding points to the bodywork under the battery. It may be corroded causing a bad circuit... In which case your stereo would turn off if drawing enough current. (had the same problem )

Also, check your battery has enough fluid in it. If its bubbling during charging, it could either be low or you're putting too much through it. If you do get your engine started, leave it running at about 2.5k revs (just use choke to hold it there), that will also charge your battery providing your alternator is ok

But the cca being low does suggest a slighly duff battery, although it only being 10 months old it shouldnt be. And if that value is low, that will cause problems for your car to start as it needs alot of amps to turn the starter motor or starting. if its not supplying enough power it doesnt turn quick enough, meaning the car wont start

As it only happens occasionally, whilst trying to start the engine, I think it is probably more likely a battery issue for me
The battery is a maintenance free type, so in theory it shouldn't need topping up, but...

I think this probably is the main problem - as the battery was installed for the previous owner, I think I might just go and buy myself a new battery with a 3 year warranty - at least then if it fails again, I can get a new one and then investigate my alternator...

Thanks for the help and advice Luke!

Probably a good thing to do first would be to clean the battery clamps and terminals (both contact faces) with a wire brush or sandpaper. I've had cases of 'invisible corrision' that caused a mysterious voltage drop!

I wouldn't worry about the CCA. Firstly, testing it must have been interesting... that's a lot of amps for a tester to draw! Surely it is just an estimate?

Secondly, the 903cc starter motor is only 0.8kW. Do the maths: that's 800W / 12V = 67 amps, assuming complete efficiency. Add on a 10% or so 'fudge factor' and get about 75A maximum draw - so well within your 189 reading.

Bubbling - personally, I regard this as a good sign that charging is taking place! Provided the battery is not a completely-sealed type (they are never supposed to bubble!), the bubbling shows that the cell is nearing a full charge. I tend to leave the battery bubbling away for about six hours, hoping by then that any sulphation has cleared from the plates. Perhaps others will disagree. I don't see any harm occurring, as long as the level is correct (get some distilled water if not, don't use tap water!)

The worst thing that happens to batteries is not over-charging, but when they sit in a partly-charged condition for one or two months. If this has ever happened to yours, be prepared to kiss it goodbye Lead sulphate builds up on the plates as a battery discharges - and the electrolyte goes from H2SO4 to H2O. The process should be reversible, but after a time the lead sulphate 'cakes' on the plates and cannot be broken down by recharging. Thus, the electrolyte is weaker (and so raises the cell's 'resistance') and the 'active lead' of the plates is masked by the lead sulphate. A 'vigorous' recharging from an external charger is all you can try, really... though I have read that a long, slow charge (say, 1A or less for 15 hours) is best. Maybe try that first, and up the current if there's still no progress!

Thirdly, when you say 'struggling to start', what is happening exactly? Is the engine cranking over sluggishly? If so, check what is happening to the voltage while cranking. It sounds like it must be dropping to cause the stereo to cut off: trouble is, different stereos will be sensitive to varying degrees, and as Luke says, you should check the earth (also try running the earth wire from the stereo to one of the heater mounting nuts...)

Before you buy a new battery, try a battery from another car. If there is little difference, perhaps your starter motor needs a clean/brush replacement. If the starter is sick, it will draw more amps than necessary...

If the engine is turning over normally, I think you should check and probably replace the points first, then the spark plugs (or adjust the gap downwards a little). Finally, experiment with pumping the accelerator a couple of times first - perhaps the engine is not getting enough fuel to start in the colder temperatures. But my bet is that the ignition system is weak!

BTW, as a quick check for your alternator, check the battery voltage with the engine off - ideally 12.3V. Then with the engine running, check the voltage again - ideally 14.2V but anyway at least 13V. Switch on high-beam headlights, rear window heater, heater fan, etc. and check battery voltage again with engine still running. The voltage should still be over the reading it was with the engine off - if not, then clearly the alternator is not keeping pace! (Sorry this sounds so elementary, it's just that modern-car voltage rules don't really apply to the Uno, so you need to go back to the basics!)



-Alex

Hi All,

Markoibook, do you know if your new battery has been allowed to go completely flat? Perhaps it’s a a poor alternator output?

I have recently changed my battery for (a larger one). I let it old one go flat once and forgot to recharge it fully. Every morning was 50 50 on whether she would start.

The stereo will automatically shut down when its supply falls below a given voltage – even when wired directly to the battery. When the starter motor is turning, it takes so much current that the overall supply voltage (as across the battery) drops below the stereo’s shutoff threshold.

Ah Alex just posted – Hi Alex. Don’t forget the condenser when changing the points. When condenser goes down (on 903) she will drive like a Kangaroo intermittently.

Any way, the bigger battery turns the starter motor nicly lol. It was baught in error, but works fine lol.

Regards All,