Need Help With Starting Problem

[Paulporsche]

I have a 2 yr old Odyssey AGM battery. Because of lockdowns, etc it has hardly seen any use and has been hooked up to my 30 year old Sears battery maintainer. Although the tender had been on the battery for some time, I'm not sure the "Charged" light was on when I unhooked it.

When I recently tried starting the car, the starter turned very slowly and subsequent cranks were even slower. It definitely had the sound of a drained battery. I measured the voltage, however, and it registered 12.6V. The starter is the high torque version.

I checked and changed the fuel pump relay to no avail.

I then put an auxiliary jump battery pack on the car battery and the engine fired right up.

Is it possible my 30 YO tender is kaput? The battery still read 12.6, which I would have thought would be enough for a start, but apparently not.

If I connect the charger to the battery and measure the voltage, should it go higher, say to 14.2?

I haven't checked grounds, but could that be the problem? Remember the engine started right up with the auxiliary battery.

Since the car is a 77, the only draw should be the clock.

Does anyone have any other ideas?

[proporsche]

for this problem would be the best to see what is the AMPs on your battery.Basically put it on load and see if it is holding...
something like this one will tell you the strength of you battery
https://www.toolsource.com/images/prod_medium/OTC3180_1200Wx1200H.jpg

[boyt911sc]

Paul,

Voltage is not the only criteria you need to know about your battery. There are another things people commonly ignore. And these are the age and CCA (cold cranking amperage) of the battery. Have your battery tested by your local auto shop usually free. The test will tell you the strength and condition of your battery. I recently replaced the battery of my ‘78 Targa that had 12+ volts reading after recharging but could not make the motor start at all. It failed the battery test and replaced the old battery.

With the new battery, it starts immediately and effortless. How old is your battery? Good luck.

Tony

[proporsche]

with the tool i gave you the link to no need to go to the shop it is a very simple useful tool...i`ve been using it for 38 years never failed me;-)

As Tony said , how old is your battery..or was it ever drained totally?
Ivan

[boyt911sc]

Ivan,

I don’t have a working battery load tester. Our local auto supply stores offer FREE testing services over here. Similar to alternator testing. I actually have one but it is not working or non-operational. Probably an obsolete model (30 plus year old electronic box). That is a nice model you have attached. Thanks.

Tony

[Paulporsche]

Thanks pro and Tony.

I thought amperage might be the problem, since the voltage seemed OK. 12.6V should be fine for starting, right?

I may not have been clear. The battery is only 2 years old and has had extremely limited use due to Covid restrictions. I'm almost positive it was never fully drained and has always seemed extremely powerful based on the starts. The jumper was one of those compact battery packs used for jump starting or powering DC equipment.

Is it possible the tender can deliver the correct volts but insufficient amps?

I tried another test: I hooked up the charger to my multimeter. Even with the charger turned on, the meter only showed .51 volts. Is this an accurate way to do this or does the charger have to be put under some kind of load? If this figure is valid, then I think I found the problem: my 30 YO charger!

I don't have a load tester and I'm not sure I want to invest in one. CAA (same as AAA) does battery testing. I may call them. Otherwise I think I'll be checking for an auto supply store that can do a test.

[proporsche]

it could be one thing.You said you have high power starter.There is a talk on English forum.Ian who comes here is traveling in France.He has high power starter..but he cannot start the car with the ignition switch-key.. only by pushing the car it could start.it came to the conclusion the starter need more power and the power is drained automatically by turning the switch to engage .it turns out that there is only around 11V going to the power starter which needs more..
Check that out in your case..
Ivan

[Paulporsche]

Thanks Ivan. I'll have a look.

But first, I just went out and the charger indicator light signaled a charged condition. I measured across the terminals and got 13.2V. I'm going to measure tomorrow morning, go for a drive and remeasure. Then I'm going to let the battery sit for a while and see what reading I get.

It's possible there was a loose connection either within the charger or at the terminals and the battery was being drained rather than being charged.

[Paulporsche]

A further update.

Doing some research, it appears old school maintainer/chargers do not charge these batteries to the Odyssey recommended 14.7v. As I mentioned in the previous post, I'm seeing a "fully charged" light @ only 13.2v.

After my drive tomorrow, I'll see if my alternator brings that voltage up. If so, then I think it may be time for a more contemporary charger/maintainer that gives me a higher voltage.

I'm not sure why 12.6v wouldn't turn the starter. Perhaps the older maintainer can't deliver sufficient amps as well as volts.

[SCadaddle]

These threads about needing a new battery come up often. After all the searching and researching I've done here and elsewhere, the simple Autozone T6-DLG battery was my pick. Even made in Germany. Fits the stock 911SC mount position for the smaller of the 2 positions. The one I bought last was made in December 2015, didn't drive my car but twice during the pandemic, didn't have it on a battery tender but lately it has charged right up and done fine.

12.6V for a brand new battery off the shelf is fine. 12.68V off the shelf is really fine. And 12.6V should have no issues with turning your starter with authority. 13.2V no load is a really "hot" battery.

This is the charger I've been using a few years when I need it. I'm completely satisfied with it.

https://www.harborfreight.com/4-amp-fully-automatic-microprocessor-controlled-battery-chargermaintainer-63350.html

[proporsche]

Paul, with your ohm meter you cannot see the amps.as we have mentioned it does not matter how many volts the batter has..... alternator should give you up to 14,2 volts......

Ivan

[Paulporsche]

Thanks SCadaddle.

I've purchased a new "smart" charger/maintainer that has a setting for AGMs. It's a 10 amp model. I've got it charging now and will check it out later.

Ivan,

Yes. I know. I found that out when I went to check amps with my meter. I think that was the issue. We'll see what happens with the new charger.

I think that my old charger was doing a good enough job to start the engine right after the battery was charged, but not a few days later. If I started the engine and then drove the car, the alternator took over, as it should, but if I waited a few days before starting, then there was a problem.

[Paulporsche]

Turns out it appears to have been the maintainer.

My new one has a setting for AGMs and, after charging the battery and then leaving the charger disconnected for a week without use, the engine fired right up. I then reconnected the new maintainer and it only took 5 minutes to get the battery up to full charge.

Looks like the 35 year old Sears maintainer, while still charging, just wasn't up to the task of fully charging the new AGM battery.