Battery test

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niclinn75
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Battery test

Post by niclinn75 » Sun Apr 15, 2018 7:30 pm

Hi Everyone

I ran some tests on my battery yesterday as I’ve had it 9 years now and was thinking of purchasing a new one.

It’s an Optima yellow top, although I’ll probably opt for the much cheaper Enduroline 049 from Tanya batteries if I get a new one.

I just wanted to know if people thought my results could be improved with a new battery. I’m still finding the majority of my driving is being done with the volt gauge in the red.

Please note the alternator is brand new (fitted last week)

SE6a automatic

Reading before engine starts - 12.3
Reading with engine idling - 14.4
Reading with fan running - 13.6
Reading with fan+headlights after 1 hours driving- 13.1

I don’t particularly want to charge up my current battery
Such a massive palaver taking it into my flat . I do it every couple of years and Girlfriemd hates it!

Thanks in advance for any advice

Nathan


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Battery test

Post by peter freeman » Sun Apr 15, 2018 8:17 pm

That's about the best battery you can buy for a car - I cannot afford one - or four for our four cars. One thing you should be very aware of is that the battery voltage seen on the gauge is no where near what is at the battery terminals. This is because the voltage is taken from the middle of the cable loom behind the instruments and a long way and resistance from the battery and alternator output. Our 6A when we had it would go into the red as soon as a normal load was put on the supply - rad fan, heater fans and lights - used to worry Glynis in the winter when in a traffic queue. I ended up connecting a wire from the battery +ve terminal via relay operated by "ignition on" to the meter +ve --- end of worry



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Battery test

Post by niclinn75 » Sun Apr 15, 2018 8:28 pm

Hi Peter

Thanks for that. yeah i had a feeling the gauge wasn't that reliable after doing my test.
I feel Glynis's pain! :lol: I might actually try wiring it straight to the battery like you did.

Yeah the Optima has been great but its been 9 years now so was thinking it might be time to replace . They say on their website they're supposed to last 8 or so years.

Do you think a new battery would up the voltage reading of 13.1 when driving with fans, lights , etc on? or is that a pretty decent reading?

Thanks

Nathan


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Battery test

Post by peter freeman » Sun Apr 15, 2018 8:31 pm

A lot higher than ours ever was. As long as the battery turns the engine over well enough to start the engine its ok.



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Battery test

Post by scimjim » Sun Apr 15, 2018 8:44 pm

Those readings are fine - your voltmeter needs calibrating IMO :D


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Post by peter freeman » Sun Apr 15, 2018 8:51 pm

Depends on how, where and with what the readings were taken Jim - its not specified.



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Battery test

Post by niclinn75 » Sun Apr 15, 2018 8:56 pm

readings taken with a digital multimeter. :)


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Battery test

Post by scimjim » Sun Apr 15, 2018 8:58 pm

I presumed it was taken across the battery terminals, where else would you take battery voltage from?


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Current: SE5 (8Ball), TI SS1 (snotty), 1600 SS1 (G97), 1600 SS1 (C686CCR), 2.5TD SE5a (diesel 5a), 6 x random other SS1s.
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Battery test

Post by niclinn75 » Sun Apr 15, 2018 9:14 pm

If theres anther way I don't know it!


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Post by peter freeman » Sun Apr 15, 2018 10:01 pm

scimjim wrote:
Sun Apr 15, 2018 8:58 pm
I presumed it was taken across the battery terminals, where else would you take battery voltage from?
from the gauge



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Battery test

Post by philhoward » Mon Apr 16, 2018 5:18 am

The dash gauge is an indication of system voltage (bus voltage as it would be called on a ship IIRC) - close, but no cigar.


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Post by peter freeman » Mon Apr 16, 2018 8:05 am

The simple way to check the dash gauge accuracy is to put a digital meter across it and compare the readings - not that getting to the rear of the gauge is that easy.



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Post by philhoward » Mon Apr 16, 2018 8:13 am

The dash gauge won't necessarily give an accurate indication of the actual voltage seen by the battery as it is reporting the voltage seen at the (end of the) Ignition Controlled supply (after its been through the relay and the fusebox) - if there's a voltage drop on either of those items (be it due to dirty contacts or a heavy draw on that circuit), then it won't necessarily give the actual battery voltage. It should be reasonably close, but I wouldn't rely on it as the actual voltage seen by the battery.

Ironically, one of those cheap eBay voltmeters you plug into the cigar lighter is probably a better indicator as little current is drawn on that circuit and there's only one fuse involved, hence less chance of volts drop.


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Battery test

Post by scimjim » Mon Apr 16, 2018 8:44 am

If you calibrate the voltmeter, it’ll tell you if there’s a problem with your wiring. As Phil says, it should be reasonably close to battery voltage so if it’s in the red all the time (and the battery and alternator seems to be fine), there’s a problem elsewhere.


Jim King

Current: SE5 (8Ball), TI SS1 (snotty), 1600 SS1 (G97), 1600 SS1 (C686CCR), 2.5TD SE5a (diesel 5a), 6 x random other SS1s.
Previous: SE5, 3 x SE5a, 2 x SE6a, 3 x SE6b, GTC, 2.9i GTC, 3 x 1600 SS1, 1300 SS1, Mk1 Ti Sabre, Mk1.5 CVH Sabre
Chief mechanic for: 1400 K series SS1 (Megan3), 1400 CVH EFi SS1 (Grawpy), Sabre/MX5 auto (The Flying Broomstick),
1300 SS1 (Number One) & Sarah's coupe.
CURE THE FAULT - NOT THE SYMPTOMS

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Battery test

Post by peter freeman » Mon Apr 16, 2018 8:56 am

There is a problem in that the meter gets its voltage from the middle of the loom - hence why I wired it directly to the battery terminal - via a "ignition on" relay - you can wire the relay to the "normal" gauge supply. Calibrating the meter for the full load situation will only make it read wrong ( high ) when the load ( no fans or lights etc ) is low.



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