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Discussion Starter · #1 ·
This might sound stupid, but i'm not sure what exactly is wrong.

Yesterday, I checked up on the Lotus. I saw the battery Tender was showing red light (still charging), even though it's been plugged in for about a week. Anyways, I turn the ignition and tried to start the car. Nothing but clicks. I check the radio, wipers, headlights, high beams, and they all work.

I pull my other vehicle and attempted to jump start. Worked after first try. I figured I drive it around and try to charge the battery that way. I shut off the engine after about 30 min of driving and I could restart it again without needing to jump start. I plugged the battery tender back in and left it over night.

Today I checked and the battery tender showed green light (fully charged). I try to start car and hear the engine crank once...and then nothing but clicks afterwards. Pulled out a multimeter and it measured about 10.4 volts.

1. Is 10.4 Volts enough to start the car? I thought it would be
2. I thought as long as the battery tender is connected, a battery would always stay charged. Am I wrong? Could there something be wrong with the Battery Tender itself?
3. Should I replace the battery? I always assumed having a trickle charger would allow you to always keep a battery charged.
 

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1. Is 10.4 Volts enough to start the car? I thought it would be
Probably not.
2. I thought as long as the battery tender is connected, a battery would always stay charged. Am I wrong? Could there something be wrong with the Battery Tender itself?
The Battery Tender can't charge the batter if the battery is at too low a voltage - that was probably why you had the red light after it had been on for a while.
3. Should I replace the battery? I always assumed having a trickle charger would allow you to always keep a battery charged.
I suspect that there is something wrong with the battery, and it's not holding a charge. The fact that the Battery Tender was showing a green light indicating a full charge implies that the charger "thinks" it's working, but when you tried to turn it over it cranked once and then failed, indicates that the battery is not holding a sufficient charge.

Try hooking up the Battery Tender over night again, then check the voltage in the morning. If it's still at 12.5 to 13.5, the charger is charging the battery - it may just not be holding a charge (in which case the battery is toast).

How's the Battery Tender function when connected to another battery?

Oh, and for the record, a Battery Tender is a BATTERY MAINTAINER, not a TRICKLE CHARGER - trickle chargers constantly apply a charge to a battery and can destroy a battery if left connected for too long, a battery maintainer charges up a battery then stops charging until its charge drops off again (it MAINTAINS the battery charge).
 

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the battery likely is shot. it may have an internal crack or such. 10.4 volts says the battery is bad.
you DID check the voltage on the BATTERY terminals, not the connectors, right?
if you can borrow a temporary battery to check, that would further decide the problem. i suspect the battery must be replaced.
good luck, sam
 

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How old is your battery? Just replaced the BMW Varta battery in a friend's 530i, and it was doing the same thing... looked like it charged up, but was only enough power for one or two cranks before the starter would make the clicking noise.

Is your battery maintenance free? If not, did you top off with distilled water before charging it?

My Z3 coupe was only driven a few thousand miles a year, and my battery only lasted 2 and a half years before needing replacement.
 

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Your battery has a bad cell. Automotive lead acid batteries are made from six cells each around 2V. When one cell dies, you can still measure a voltage across the terminals, but there isn't enough enough juice to generate any significant amperage, so your car won't start. A completely discharged, healthy lead acid battery will be a little bit less than 12V, if the voltage is much lower than that, the battery is damaged.

I bet if you look at the battery, one of the six compartments is out of electrolyte or looks way different than the other five. Get a new battery.
 

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Discussion Starter · #9 ·
Ok odd. Just checked it again after putting battery tender on. I measured the voltage drop and it read 12.85. Tried to start it again and still no go. Is it possible for the voltage to read above 12 and still not start (assuming the issue is the battery itself).
 

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A battery, after charging will not give an accurate voltage reading. The surface charge has to be removed, see "Battery Testing";
http://www.lotustalk.com/forums/f129/battery-choices-information-64071/
Cheers,
Michael
Ok odd. Just checked it again after putting battery tender on. I measured the voltage drop and it read 12.85. Tried to start it again and still no go. Is it possible for the voltage to read above 12 and still not start (assuming the issue is the battery itself).
 

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turn on the headlights and test the voltage...i'll bet it's very low.
sam
 

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"It's dead, Jim!"

 

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Dammit Jim, its dead!!
 

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Thanks for the responses.



Probably around 2 years old.

Sounds about right, depending on frequency of use. My stock battery died a rather sudden death after only 2.5 years of mostly weekend driving. Also, not sure what maintainer you were using, but stay away from anything from Black & Decker. Far away.
 
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