is the battery the culprit ?

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cacaolat
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is the battery the culprit ?

Post by cacaolat » Sat May 09, 2015 2:00 pm

I have a newish battery in my BX.
recently I noticed the red battery warning light flickering on occasions.
Then one day the starter motor made a clicking noise instead of turning.
I noticed that the earth strap at the base of the battery was loose and I tightened it up.
A friend gave me a jump lead start.
To charge the battery I drove around for at least half an hour but every time I operated a window the dashboard light went off.
After half an hour I parked but the starter was just clicking again.
Today I checked Voltage of battery and it was only 11.4V.

Question: Do I buy a new battery because this one may be damaged ? or could there be another reason why the battery did not charge ?
former BX 16 TGS Meteor Auto owner. No space or time to do own repairs. My BX is now owned by another member of this forum.

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Re: is the battery the culprit ?

Post by Way2go » Sat May 09, 2015 2:48 pm

It sounds more likely to be the alternator or its wiring at fault.

Measure the voltage across the battery with the engine running. It should be about 14v to provide a successful charge.
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Re: is the battery the culprit ?

Post by kernowtim » Sun May 10, 2015 9:15 am

Unlikely to be battery fault, check battery terminals clamp up tight, they are made from soft metal and stretch over time,battery voltage should be about 12.5v with no load rising to around 14v with engine running, check voltage with engine running and heated rear window and lights on, should still be 14 volts ,of not suspect alternator (is belt tight) or possible poor connection as above post.May be worth charging battery off car first

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Re: is the battery the culprit ?

Post by Defender110 » Mon May 11, 2015 12:12 pm

As above.
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Re: is the battery the culprit ?

Post by Kitch » Mon May 11, 2015 2:06 pm

Sounds like the diode in the alternator's gone to me. Doesn't make sense about light/window behaviour though.

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Re: is the battery the culprit ?

Post by Tinkley » Thu May 14, 2015 5:17 am

Agree with above - alternator suspect. It also ,on a petrol gives poor fuel consumption.

Exchange units (Valeo) are I believe still available, but test first. Also a whack with a mallet may remove carbon build up from the brushes and give it a bit more life. Trouble is you don't know when it will fail in future... :wink: Get the right alternator, there are several different ones - 4 V and 6 V belt options etc depending on AC or lack of.

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Re: is the battery the culprit ?

Post by Kitch » Thu May 14, 2015 1:58 pm

Tinkley wrote:It also ,on a petrol gives poor fuel consumption.
Go on then, I'll bite. :lol:

Erm.....what?!

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Re: is the battery the culprit ?

Post by cacaolat » Wed May 20, 2015 8:33 am

Thanks for all the advice. The alternator has now been replaced under warranty, as it was only put n 3 months ago.
All fine now.
Not sure if it was faulty or it got damaged by the loose earth strap.
former BX 16 TGS Meteor Auto owner. No space or time to do own repairs. My BX is now owned by another member of this forum.

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Re: is the battery the culprit ?

Post by Thread Bear » Wed May 20, 2015 9:43 am

Time was an alternator that could not dump its charge into the battery, or void it off, it would knock out the Wheatstone Bridge. This meant inserting another. Long gone are those old designs. The alternators are sealed units now. No idea if they still pop if the generated current cannot flow, though. They seem to last pretty will in the BX age group, noticable that its often the first part to sell in the breakers yard, nonetheless. Certainly a dodgy alternator can cause carnage to a modern computerized crate, knocking out all sorts of things.
So it was fun to see the look of wonder on young faces when I repaired a dynomo for a mate in a car park. The simplicity and shear audacity to do this, rather than blub to the AA was something beyond their thinking. But most prefer the surety of charging, and with all the gadgets folk feel they need these days a dynomo is not going to cut the mustard. Good fun, though.
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Re: is the battery the culprit ?

Post by Tinkley » Thu May 28, 2015 9:07 am

Kitch wrote: Go on then, I'll bite. :lol:

Erm.....what?!
OK Kitch, here's why I think it does affect fuel consumption. The BX petrol carb versions are not fully electronic ignition systems independent of the battery ie self exciting from a dedicated coil. Some motorcycle and outboard engines are, maybe some newer cars, it means you can run the engine with no battery - hence kick start (m/cycle) or pull start for an outboard. These make a lot of sense, and maybe genuinely lifesaving especially at sea.
Using the battery with not enough charge from the alternator does not allow the BX part electronic ignition system to have as big a spark as it should and hence poor fuel consumption. It certainly made quite a difference on mine prior to the alternator failing. Once I had the replacement alternator and the battery charged up correctly, the fuel consumption improved dramatically. As no other component had been changed such as dizzy cap etc the only culprit had to be the 'spark power'. The battery did a further two years before dying from old age.

So poor fuel consumption can actually be down to a slowly failing alternator giving insufficient charge to the battery!. As it is a quick test with the meter to check charging voltage it is worth bearing in mind IF you are tracking such a fault on a system where the battery is in the ignition loop.