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How do I know when my battery is sh***ed


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I know was chilly this morning (-6 ish) but my battery did not stand a chance of starting the 7. Even though its always on tricle charge it never seems to be able to start the car. its a Hawker 680 so should have enough grunt to start the 2 litre duratec. so how can I tell if its past it?, its giving out 12 V and taking in 14 v

it seems to crank the car up to about 250 rpm but very briefly before it dies a death


also where is the cheapest place to get a new one, best price I have found is £95



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Its a gel battery, how low would you expect the cranking voltage to be on a good/ bad battery?

I have done all the usual wiring and earthing checks but not having a known 'good' battery to compare with its hard to check


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Right, a quick round up to know if you have a good battery:


With a multimeter and with everything switched off you want a minimum of 12v across the battery terminals and anything up to 13.7v is OK or to put it another way:


battery voltage............ % charge

12.6v or more.............. 100

12.4-12.6 .................... 75-100

12.2-12.4 .................... 50-75

11.7-12.0 .................... 0-25

< 11.7 ......................... it's fubarred


Turn the ignition on and try starting the car, if the battery voltage drops below 9vthen you either have a knackered battery or there is too much resistance so check connections/earths etc, if they are OK check the starter motor


The PC680 is sold by Powervamp Racing (Google or search this forum) and is now called the PVR25, ring them and speak to Ed Roller and tell him you belong to L7CGB and he'll sort you out free P&P although it will probably cost about the £95 you've got already...



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Simon, I’ve managed to coax badly discharged lead acid batteries back to life in the past by connecting another good battery in parallel during charging, but this doesn’t seem to work with these new fangled compact gel types – they hold their charge well but if you let the voltage drop too far, they’re scrap. I’ve no idea where the threshold is but I do know it’s an expensive mistake as I managed it myself on a Powervamp 680.


The good news, if you find that you need a new battery, is that we have a bulk buy arrangement with Rally Design for their RMD Racing 25 battery. This is an equivalent spec to the Varley Red Top 25, Odyssey 680, Powervamp 680 etc. RD give us a discount for orders of 6 or more. The battery is cheap to begin with at £49.50 but exceptional value after bulk discount at £29.50 (plus VAT and carriage). See this thread for more details.


The batteries can either be despatched direct from Rally Design or I can collect them as I work nearby. That's only really an advantage if you attend any of the Kent area meets or can twist SM25T's arm for a gonads delivery.




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  • 3 months later...

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