How reliable are car battery condition gauges?

[theorganist]

Hello,

 

I have got the Princess on the road finally and drove it to work today to give it a run. I have noticed the battery condition gauge seems to hover from a little inside the red mark to just inside the "normal" section, although mostly it is in the red?

 

I will try and get it tested over the next couple of days but was just wondering whether they were considered a reliable indicator?

 

As an aside to this the indicators don't actually flash just stay on constantly the hazards to flash however!

 

Hopefully I will get some picture of it over the weekend as I know many on here like some BL action!

 

Thanks,

Pete

[dollywobbler]

Sounds like a mild charging issue. Indicators sometimes have a separate relay to the hazards, but it might be that the lack of healthy electric power isn't enough to make the relay click. New brushes may do the trick. I need to do similar on the BX, as the battery light glows dimly when you load the electrics (ie HRW, heater, headlamps all at the same time)

[Mr_Bo11ox]

Just chuck a multimeter across the battery with the engine running, needs to be over 13.5 volts or thereabouts, if it is you can ignore the shonky BL instrument

[Mr_Bo11ox]

Your flashers are quite likely to be a shitty old BL flasher unit, theyre always going on the blink

[theorganist]

Sounds like a mild charging issue. Indicators sometimes have a separate relay to the hazards, but it might be that the lack of healthy electric power isn't enough to make the relay click. New brushes may do the trick. I need to do similar on the BX, as the battery light glows dimly when you load the electrics (ie HRW, heater, headlamps all at the same time)

Yes they are separate relays, there is a third for the seat belt warning light as well!

[theorganist]

Your flashers are quite likely to be a shitty old BL flasher unit, theyre always going on the blink

Yes haha Lucas electrics are great! 

 

 

Found a friend with a multi-meter so will check tonight.

[Squire_Dawson]

Yes, a charging problem. Batt. indicators are basically voltmeters, so very reliable.

 

If you switch the headlamps on, and rev up the engine, do they increase in brightness?

 

If the drive belt is tight enough, then either the alternator needs attention or the battery is packing up, but I'd leave it charging for a while first and check the electrolyte level, if you can.

 

It happens on my Allegro in traffic with various equipment in use, the indicators slow right down, but if I switch off the blower and headlamps, they speed up again.

[theorganist]

I will see if I can discover a particular habit when I go home tonight, the headlights seemed pretty bright when I tried them last night and I did not notice any difference, the fan seems to run at a constant speed and does not speed up or slow down, which I have had on cars before. This is the first day I have really driven it apart from a couple of very short journeys.

 

The battery was a £15 job from a scrapyard to be honest, I have had them before and they have lasted a long time.

[Inspector Morose]

I can wang down with the meter tonight if you want?

[Guest Breadvan72]

When I had a Murena Roy the Matra man advised me to ignore the battery gauge as it was always wrong.   The ones I have had on (non BL) Brit cars have all worked pretty well, and the one on my Lancia shows that the alternator is very keen and enthusiastic.

[theorganist]

I can wang down with the meter tonight if you want?

 

Thanks I have sent you a PM.

[Inspector Morose]

And replied.

[mat_the_cat]

Bear in mind that a dashboard voltmeter, even if completely accurate, is only telling the voltage across its own terminals. Which may or may not be a true reflection of battery voltage. I.e. if you have a high resistance in the circuit the meter and any ancillary is connected to, when you turn on something which draws significant current, there will be a voltage drop (i.e.lost) over that resistance, such as a corroded fuseholder or earth connection.

 

A multimeter in different places should show more...

[dome]

My local Unipart has a battery condition meter they'll plug in for free, Hellfrauds should have one too but whether anyone there knows how to work it is a different matter....

 

They're just a posh multimeter but worth a try-checks the battery and the alternator.

[theorganist]

Well I had it tested before I went home and the multi-meter showed it was charging below 13, confirmed by the fact that when I got home I had a flat battery!

[dome]

Ah bugger. If it's a Lucas alternator then step this way

 

http://www.jcrsupplies.co.uk/

 

These boys are good, sorted me out when the Jags alternator was gubbed. There are cheaper bits available via ebay but these boys were helpful with quick delivery so get my vote.

 

Brian

[theorganist]

Brian,

 

Thanks for that will check their site out.

 

Pete