Mysterious Battery Test

[Justinkent83]

Here's a scenario for you guys. It's got me a bit stumped.

I've got two Optima Blue Top 27M (D27M) batteries. I was suspicious they may be bad, so I tested them. Using a digital tester, I tested each battery separately outside the boat. These batteries have the lugs AND the screw down posts. When I test each battery by connecting the tester to the lugs, they test 100% health over 1000CCA all good. When I test them across the screw down terminals, the report is awful. Under 200CCA, 13% Healthy, red flags all over the place.

My question is this... is it normal for a battery to fail a test across the screw down terminals, yet pass across the lugs? It seems like the output of the battery should be the same regardless. Both batteries tested out this way, good across the lugs, bad across the screw down terminals.

Have any of you ever seen anything like this? I haven't installed my new starter yet, but now I'm wondering if I even needed one...

Thanks,

Justin

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[chpthril]

One of the suspect terminals good have suffered a near physical separation inside the case. Have you measured voltage between each par of terminals and compared? Have you done a continuity test between each + and then between each -?

[Justinkent83]

One of the suspect terminals good have suffered a near physical separation inside the case. Have you measured voltage between each par of terminals and compared? Have you done a continuity test between each + and then between each -?

Hi Chpthril, thanks for chiming in. I haven't done a continuity test between like terminals, although that's a good idea, I'll try that tomorrow and post the results.

I did measure voltage across each pair, the voltage was good. Mid 12v on each battery, across each pair. I did see that the internal resistance across the screw posts was a bit higher than it was across the lugs.

Here are two test results. The battery is the same. The good test is across the main + and - posts. The bad test is across the threaded posts on the same battery.

I get pretty much the same results on the other battery, except the other batter shows 100% charge when using the main posts.

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[Justinkent83]

Update: I ended up not doing the continuity test, and here's why.

On the way home from my office, I called Optima customer support. After explaining the situation, I was told that it is normal behavior for a battery to fail a load test on the stainless threaded posts because the post itself is not the primary point of contact. The threaded post is there as a mechanism to compress your leads to the lead base as the bottom of the threaded stainless post. When I inspected the batteries, sure enough, the posts really do have a lead base under them. That information seemed logical, so I'm chalking the failed tests across those threaded posts as "normal behavior".

The temp was in the 50s today. I left the office early to get a head start on installing my new starter. Removing the rear bench and exposing the trans/motor was much simpler than I realized. Changing the starter was pretty quick and painless. Once I finished and reinstalled the batteries, she fired up with serious authority! The starting issue is resolved.

While putting my batteries back in, I was reminded of something I meant to ask you guys. I found a lead that isn't connected to anything. It has a ring terminal on it and appears to be running through the factory harness. I didn't have time to test it to see if it's a ground or supposed to be hot. I thought I had a pic, but I must not have taken it. I'll get a picture tomorrow and see if anyone recognizes it as factory. I haven't found anything on the boat that doesn't work as a result... yet.

Thanks everyone!

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[chpthril]

Just another reason why I do not like Optima. They do things and a build batteries like no one else and I dont mean that as a compliment! They come up with some of the strangest explanations for their weird battery issues. Optima is not the only manufacture using dual terminals with a threaded stainless post potted in lead that common with the other terminal style.

Yes, it is the ideal concept to compress the cable terminals to the lead base and the stainless post and nut are the mechanical means to accomplish this. However, I have never seen a battery pass a test when using the lead pinch-post and fail when using the stainless threaded post.

[Justinkent83]

Admittedly, I thought it was pretty weird too. I guess we'll see if any issues arise from the batteries this season. The Optima batteries were already in the boat when I bought it, for better or worse.

Luckily when I installed the new starter, she fired up like a champ! One less thing to worry about.

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