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So a month ago I replaced my Odyssey PC680 with another one (3 years old and was not holding charge more than a couple days).

New one worked great, driven with it a few times and drove the car around for 40 min last weekend to keep it charged. Normally I should be able to sit around 2 weeks with a PC680.

Anyways I go out to drive today and the battery is totally dead, never had that before. I've had power to stereo, and HID lights, but it wouldn't have enough juice to crank. BUT this time, it was totally dead, turned key and nothing.

Then I noticed a little while later my immobilizer light is very faint red (solid, not blinking). I jiggled the battery cables, everything seems fine. Turned key and nothing. Faint red light went away.

Could this be a fuse? Bad alternator? I guess I'll go buy a battery tender tomorrow and hook it up. I don't think the new battery should be dying in a weeks time which makes me think it could be something else?

Thanks in advance. I tried searching, but not really sure what keywords to try and didn't get any hits earlier.
 

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the battery will recover slightly after a while so thats why it came back to life the immobiliser doesn't need much to run it, it either comes from the alarm/immo or the alternator, either one is saying not enough juice, attempting to crank it takes away that residual build up and the voltage is too low to light anything.
 

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Discussion Starter #3
thanks charlie for the help. so shouldn't be a bad alternator? the engine would still turn with a bad alt, right?
 

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The red red light, is in it's "alternator" mode, & probably indicates that the battery voltage as low as it was, was greater than the alternator voltage, which was non-existent. You need to get that battery charged and then checked.http://www.lotustalk.com/forums/f129/battery-choices-information-64071/
So a month ago I replaced my Odyssey PC680 with another one (3 years old and was not holding charge more than a couple days).

New one worked great, driven with it a few times and drove the car around for 40 min last weekend to keep it charged. Normally I should be able to sit around 2 weeks with a PC680.

Anyways I go out to drive today and the battery is totally dead, never had that before. I've had power to stereo, and HID lights, but it wouldn't have enough juice to crank. BUT this time, it was totally dead, turned key and nothing.

Then I noticed a little while later my immobilizer light is very faint red (solid, not blinking). I jiggled the battery cables, everything seems fine. Turned key and nothing. Faint red light went away.

Could this be a fuse? Bad alternator? I guess I'll go buy a battery tender tomorrow and hook it up. I don't think the new battery should be dying in a weeks time which makes me think it could be something else?

Thanks in advance. I tried searching, but not really sure what keywords to try and didn't get any hits earlier.
 

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Discussion Starter #5
Ahh that explains the solid red light

Thanks for the help guys.
 

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Its probably the alternator. New battery dying after just a few weeks? It wasn't charged by the alternator and the car was running on battery power only. You finally exhausted that, so battery is now dead. Your old battery may have been ok...
 

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Since the red light is coming on when the key is off, its not going to be the alternator thats doing the flicker, its the immobiliser half booting up, everything freaks out when the voltage is low.

the battery is likely flat thats all.


its always possible the alternator is bad and not charging the battery, but its equally as likely the battery is just flat or there is a loose cable.
 

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Disingenuous Minion
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20mA immobilizer draw on a fully charged, new, 17Ah battery should last at least a month. Sounds like a charging problem which would point to alternator or bad connection, etc.
 

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doesn't matter how many mA the immobiliser draws if the battery isn't putting out enough voltage, either being from being discharged, bad or loose connection.

there isn't enough info to determine what the fault is, but the alternator is not whats causing the red light if the key is off.

i doubt a pc680 lasts that long, my stock battery will die out after a week or so of sitting around.
 

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Disingenuous Minion
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But the point is, why would a brand new 17Ah battery, with 20mA draw, charged 7 days ago have low voltage? It was a replacement for another battery only 3 years old, which suggests the previous battery was possibly not actually bad. The problem is probably caused by some other problem: likely charging.
 

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like i said my stock battery often doesn't last 7 days so i wouldn't imagine a pc680 would either.

its a bad battery, charging fault or loose connection :) but the red light only flickers off the alternator regulator check when the engines running which still only means the same faults could be present, if the key is off the residual potential in the battery gets the immobiliser into an undefined state where things float and it causes the light to come on, i run into it all the time on my car since it spends a lot of time on the bench.

so if the engine is started, and the red light flickers its a problem with the alternator,charging or battery ;) if it doesn't then its probably a bad battery or somehow the charging isn't working but the alternator is
 

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Disingenuous Minion
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I dissagree with your "wrestling with a pig in the mud" theory. I'm an engineer and I hate arguing. :)
 

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Then you'll know the car draws more than 20mA offline, that batteries discharge even when they're not being used and no draw and it changes with temperature, and that its illogical for the alternator regulator to be flashing the light with the key off, that we don't know how well charged the battery was previously, there's no indication of that, a 40 minute drive might not be enough to fully recharge it, but enough to keep it starting for a while.

;)
 

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Disingenuous Minion
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How much does the car draw off-line? 20mA is the debated value in the battery thread.

San Diego is pretty cold right now, possibly as low as 50 degrees F, but that won't affect the performance of this battery. And a month old battery shouldn't be losing capacity due to age.

I am not familiar with the fault indications/codes on this car, I know that you are. Just seems very strange that two otherwise good batteries in the same situation would be bad.

Like I said, engaging in arguments is just horrible, I hate it. My instinct is to agree with everyone all the time.
 

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no argument, since i don't think we're disagreeing.

the most common fault is loose connection, the second is that the batteries just don't seem to sit for long without a tender, the alternator regulator does get fried but its less of an issue, and easier to test since if the light doesn't flicker when the car is on max load at around 5000RPM or so, it's not the alternator.

i haven't been driving my car much, and without a tender it'll go flat in less than a week, but i'm not fully charging it either, i don't think 40 minutes is enough to replenish an almost dead battery though.

i'll measure the draw current tomorrow, its easy to find out what its doing while off.
 

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Lotus state that the total car parasitic draw is 20ma (Lotus service notes) with the alarm on, or 15ma with only the immobilizer on (does not include radio).
Cobra state 13ma with alarm armed, 9ma disarmed
Conclusion that Lotus seem to agree with is that the ECU take 7ma (20 - 13), Charlie maybe you can confirm.
PC 680 has a rating of 17AH
The calculation of how long it would last until it got down to the 10.5V threshold standard is 14 days. However at 10.5V the starter would not operate.
In a nutshell it is almost impossible to calculate how long a particular battery will last, still being able to start the car as there are too many unknown variables. Even two identical batteries will last different times.
AGM batteries such as the PC680 have a very low "natural drain" of about 1 - 3% per month.
Flooded cell batteries drain about 1% per day.
Michael
 

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Disingenuous Minion
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no argument, since i don't think we're disagreeing.

the most common fault is loose connection, the second is that the batteries just don't seem to sit for long without a tender, the alternator regulator does get fried but its less of an issue, and easier to test since if the light doesn't flicker when the car is on max load at around 5000RPM or so, it's not the alternator.

i haven't been driving my car much, and without a tender it'll go flat in less than a week, but i'm not fully charging it either, i don't think 40 minutes is enough to replenish an almost dead battery though.

i'll measure the draw current tomorrow, its easy to find out what its doing while off.
I will measure Monday also so we can compare notes.
 

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I'll check the ecu i have one on the bench connected to a bench supply so easy to check , the radio is always in standby mode so it'll draw something too.
be nice to figure it out once and for all.

I'm pretty sure though my stock battery will not last 14 days though, and of course that requires it was fully charged and has the same capacity as when it was made.

Also if the battery was deep discharged before, it may not have fully recovered without a long recharge cycle.
 

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The weird thing about the radio was the readings I got placing my ammeter across fuse F15 - reading of 650ma for a few seconds, it then went down to 0ma, pausing at 3ma Repeated test many times with the same result.
 
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