Lotus Elan

battery shot?

PostPost by: Lotus 50 » Sun Oct 14, 2018 7:58 pm

I took my Plus 2 for it's last drive before winter hibernation today and had to get jump started when I stopped for fuel.

12V (0-50V scale on my voltmeter) at the battery. 2 or 3V at the engine compartment. Nothing electrical works - interior lights, windows, radio, most important starter motor. Once jump started everything seems normal. After 2 jump starts I parked it for the winter. Fogged the cylinders and put the dubious battery in my basement.

I have 6 months to check the battery. Do you suppose I have a sudden battery failure?
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PostPost by: Grizzly » Sun Oct 14, 2018 8:32 pm

It screams bad ground tbh, but it could be a bad Alternator (assuming you have an Alternator) or as you say a bad battery....... did you check too see what voltage the battery was seeing when the car was running? if the Alternator/Dynamo has packed up you will get similar symptoms.

If you have removed the battery try trickle charging it for a couple of days so it's fully charged then leave it for a week and see where the voltage drops too, if a cell has gone it will be about 10v.
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PostPost by: elanfan1 » Sun Oct 14, 2018 10:40 pm

Take the battery to Kiki Fit or Hafrauds and get them to test it after you?ve charged it. I think they can tell from the drain it?s condition. Beware of them just selling you a new one though have a look at the test yourself.
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PostPost by: Andy8421 » Mon Oct 15, 2018 5:52 am

Lotus 50 wrote:I took my Plus 2 for it's last drive before winter hibernation today and had to get jump started when I stopped for fuel.

12V (0-50V scale on my voltmeter) at the battery. 2 or 3V at the engine compartment. Nothing electrical works - interior lights, windows, radio, most important starter motor. Once jump started everything seems normal. After 2 jump starts I parked it for the winter. Fogged the cylinders and put the dubious battery in my basement.

I have 6 months to check the battery. Do you suppose I have a sudden battery failure?


It is temperature dependent, but a fully charged lead acid battery has a resting voltage of approx 12.7V and a completely flat lead acid battery a resting voltage of 11.8V. Not sure how good your voltmeter is, but even a budget DVM should be good enough - a reading of 12V would put your battery in the the flat to 25% charge range. Your battery could do with a good charge, leave for a day or so then check the resting voltage again.

More worrying is the 2V to 3V in the engine compartment. Assuming that this was measured at the same time you were getting 12V at the battery, you have other problems - most likely corroded battery terminals or a dodgy earth somewhere. First place to check after cleaning the terminals and battery clamps would be the point that the battery cable earths to frame via a bolt in the boot. It rusts and / or can get loose and is often a cause of problems.
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PostPost by: stugilmour » Tue Oct 16, 2018 3:09 pm

Andy8421 wrote:... First place to check after cleaning the terminals and battery clamps would be the point that the battery cable earths to frame via a bolt in the boot. It rusts and / or can get loose and is often a cause of problems.


For sure check this problematic ground connection. Note it may test OK with an ohnmeter but produce significant voltage drop under load.

A common mod is to move this main battery ground connection to the right side body to tower bolt located behind the rear seat back. Besides moving the ground out of the road muck, this bolt is threaded directly into the frame so forms a much more secure connection. You may need a slightly longer generic cable to reach.

HTH

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PostPost by: Concrete-crusher » Tue Oct 16, 2018 3:59 pm

I have a little led voltage display that plugs into the cigar lighter , quite useful for seeing the voltage before starting and knowing the alternator is working properly

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PostPost by: bob_rich » Wed Oct 17, 2018 10:14 am

Hi

If you have 12V at the battery, as others have said. it is not totally dead. 2 to 3V in the engine compartment then you are looking for 9 to 10V being lost across something. I assume there was no smoke or anything nasty like that. Earth in boot is the really weak one. as you have a DVM try measuring the voltage from the battery earth to the earth point you used in the engine compartment. With a real bad earth even the current of a interior light could produce a resistance that would give you a 10V or so drop.

if it is not earth does your car have an ammeter? they can burn out and go high resistance and then nothing so check the leads to that are OK.

the suddenness of the problem also suggests a lead somewhere may have gone very loose and high resistance

hope this helps

best of luck

Bob
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PostPost by: Lotus 50 » Sat Oct 20, 2018 11:33 pm

Ammeter in car read normal. Battery terminals and vehicle connections look fine.

Interior lights were off, not engender dim - although it was sunny. My voltmeter scale is 0 to 50, not the best for this work.

I just bought a trickle charger so I can charge the battery and then get it tested.
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PostPost by: nmauduit » Sun Oct 21, 2018 9:00 am

Concrete-crusher wrote:I have a little led voltage display that plugs into the cigar lighter , quite useful for seeing the voltage before starting and knowing the alternator is working properly

Steve


unfortunately voltage alone does not guarantee everything is fine for starting : one system may have some terminal oxidation (e.g. battery ground strap to the chassis) that would let a small current flow so as to display the nominal battery voltage over 12V, but when attempting to crank the starter would call for a much larger current that would create a significant voltage drop at the resistive ground contact and not let enough voltage to torque the engine (or even actuate the starter solenoid).
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PostPost by: 69S4 » Mon Oct 22, 2018 7:51 am

It does sound like a connection issue but sudden battery failure is not impossible. I've had two gel type batteries on other vehicles fail 'instantly' in the last few years. One of them was working perfectly - cold started the engine at the house yet one mile later after a fuel stop was completely dead on restart. There was over 12v at the terminals but nothing under load.

The second one went from working perfectly to struggling to dead in three days with the same 12v+ to near zero characteristics. Neither vehicle had charging problems but both batteries had a few years on the clock. I've currently got an 8yr old Odyssey battery in the Elan which has been a great purchase but I'm now starting to wonder what its failure mode will be.
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PostPost by: The Veg » Wed Oct 24, 2018 11:50 am

+1 For Odyssey batteries. I've used them in several BMW boxer motorbikes, including late-model R1200s which can be notoriously resistant to cranking on cold mornings. Good batteries that will take a lot of abuse. Got one in the Plus 2 as well and can't wait to see how it does in the real world once the car becomes roadworthy.
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PostPost by: mbell » Wed Oct 24, 2018 8:01 pm

-2 on the odessy.

I have one in my +2 and despite the remote kill switch I have on it if left more that a day or two I have to jump start it. This may be a user error as I've flatten it a few times while dealing with starting issues and re charged with a normal recharger.

I'll likely replace it with another one as built a special battery holder for it but some care is needed with them.

My brother had the same battery on his mini and kept on a float charger. He had to get it flat bedded it to a photo shoot because of the failed battery and no ability to replace it locally. They declined to replace the battery for him. Again this might have been a user error in not using the right float charger or a not.
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PostPost by: Grizzly » Thu Oct 25, 2018 9:57 am

I have a few Odyssey and Powervamp batteries, they are great as long as you don't let them go completely flat and use the correct battery conditioner when the car is not in use, first time you drain one completely flat the battery will never be the same again.

In the past I've started a Jenson Interceptor 440 v8 with a Pc680 which frankly was a surprise, i have one on my race car and my boss uses one to start his high compression RS2000 so plenty of cranking power.

I have an Odyssey PC925 waiting to go on my 2 seater when i can get my act together.
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