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Discussion Starter · #1 ·
For the voltage shown on the display unit to drop to 8.5 volts or thereabouts when starting the engine for the first time?

I've just bought a new Bosch battery for the CSE because the owners manual warns that a displayed voltage of 10 volts or less
on startup is indicative of a tired battery.
The thing is the new battery is showing a similar voltage drop, even after a 100mile drive which should have fully charged it.

Strangely , if the car is immediately re-started again, after the first attempt of the day, ( which it frequently is, thanks to the poxy immobiliser thingy which kills my ignition after the delay of the couple of minutes it takes to load my two weans 4yrs & 6yrs into the car , but hey that's a whole other gripe..) then the voltage only drops to 10 or 11 volts.

Is the display to be trusted?, Is this level of voltage drop normal? , does it matter?, Have I wasted 35 quid and the old battery was OK?
The car is an auto, so a good battery is essential ( no bump starting). The temperature around here has been -3 to +5 degrees celsius recently.

Can anyone tell me if their car shows a similar voltage on startup?
 

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I sometimes see readings as low as 7.2V on mine but it never fails to start. The battery is about a year old. I reckon that the EDU shows the lowest voltage which occurs whilst starting but that seems to include momentary dips which may only be of a millisecond or less. Ignore it. To be of any use it show the average cranking voltage. Well that's my opinion anyway.
 

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I often see relatively low figures whilst cranking, and then it displays a higher figure after starting as the "overall cranking" figure. However, these numbers entirely failed to predict my last battery failure.

I think that it might have been effective with old lead acid batteries, but the current silver oxide batteries seem to just die all of a sudden without much, if any warning.

Just carry jump leads.
 

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Discussion Starter · #7 ·
Thanks very much for your help folks,
That's reassuring in one sense ie don't worry about low voltages, however don't expect any warning of battery failure.( and I may have wasted my money, I bought the new battery from Costco, wonder if they'd take it back? , I could say it was the wrong colour)
I agree is seems to record lowest voltage, as the next start-up is always on a higher voltage.

PS: Sorry for delay in replying. My PC had a virus and then couldn't find it's modem after being re-formatted
 

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The manual statement, that voltage shouldn't drop below 10V on starting, is definately unrealistic.

I check battery cell conditions with Hydrometer (Like a basting syringe - measures relative density of electrolite). Typical life of Silver Oxide batteries is 3 to 5 years. If these ever run flat, then never properly recover, unlike the older lead acid type.

The second fire up will normally take less load (i.e. cause less voltage drop), as engine will be better lubricated after first short run - especially in cold/winter tempretures.

If you take new battery back and state your old one wasn't dead, the suppliers might well take it back, so long as not marked/damaged.
 

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I've found that decreasing starting voltages allied to low charging voltages (hardly ever reaching 14.0 volts, more usually 13.8v directly after starting - and dropping back to 13.5v or so after a few miles) are indicative of a dodgy connection between the battery and alternator.
I found out the hard way that changing the battery (even though all the tests said it was OK
) and the garage changing the alternator
(because they couldn't see the obvious{in hindsight} either!) didn't change the fact that the alternator just wasn't 'seeing' the battery as there was a slight 'high resistance' between the battery terminal and the cable. After changing this (battery terminal) alone the battery charged better than ever (14.2v or more dropping to 13.8v after a few miles), the door solenoids would operate far more swiftly as well on locking/unlocking the car.
Since some recent gearbox work, and on this I'm hypothesising, I reckon an earth strap might have been disconnected/ reconnected, improving matters further.
Give these things a go, it's an awful lot cheaper than a new battery, not to mention an alternator, grr...
Nick.

PS. On starting I get around 10.5 - 10.8 volts. (I know it's warmer down here )
 

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I might try that on the Carly then.

It's run 12.8-13.3 v for 3 years now....

the 1st 6 months it would either start or just click but had had 3 battery's, 2 starters amd 2 batteries in the previous 18 months.

A wollop with a big screwdriver handle on the +ve battery terminal sorted the clicking no start for good.

I will now check the earth strap and alternator leads.
 

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Absolutely Mark/Andrew, this is what I eventually found once the 'clicking of relays on starting' became a permenent fault rather than occouring just on the first turn of the key (If you get my meaning).
The factory joint between the positive battery terminal and the actual cable (as you say the short piece to the 'distribution block') seems to go High Resistance, but on starting the 200amps or so of current being drawn can change the resistance at this junction allowing the car to eventually start (often on the second turn of the key). When I say high resistance it would only be a fraction of an Ohm, you'll never measure it with the type of meters 99.9% of people have.
The best way to read it would be to 'stab' the cable with one prod of the meter (on volts) and clip the other to the terminal. If the meter has a fast reading Min/Max facility so much the better, put it on, if not then just keep an eye to it as you crank the car over. If you have over a volt you have a problem with the connection.
HTH
Nick.
PS. Other connections can be tested in the same manner.
 

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Originally posted by cdcarlsson:
[qb]If you have over a volt you have a problem with the connection.
[/qb][/b]
I take it you're referring to the voltage drop on cranking, Nick- I measured around 0.4V IIRC with headlights and rear window heater on.

Basically, under loads other than cranking, that cable should have less than 0.1V across it, or it's on it's way out.
 

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Originally posted by cdcarlsson:
[qb]...then just keep an eye to it  as you crank the car over . If you have over a volt you have a problem with the connection.
[/qb][/b]
Yes, absolutely, as I stated. It's the best way to find a weakness in the system, put it under the most load it's going to have to put up with.
Nick.
 
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