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In an earlier post (sometime in 2015) I had incorrectly blamed my Battery Tender Jr for the failure of my Odyssey battery. I had tried using another tender in hopes of possibly "healing" the battery's sulfated cell condition to no avail. Just changed it out last week with a new PC-680. In doing some research on the "right" tender according to Odyssey I was becoming increasingly dismayed when seeing the prices for the "right" tender. They ranged in price from a low of near $100 to near $200 just to keep the 680 healthy. The Battery Tender and Jr is not on Odyssey's "approved tender list". In reading the technical info on the 680 and their charging requirements the bottom line from where I stood was the necessity to keep the float voltage from 13.5 to 13.8 volts. I was thinking my BT jr would not do this and hence the early failure of the battery (3 yrs). So I wrote Deltran to find if they had a tender that would keep my 680 healthy and not break my wallet. Here is a letter from Deltran concerning the Battery Tender Jr. Sure settles my concerns...

Good Morning Mr. Bowyer,

For your specific battery we always recommend that you check with the battery manufacture directly. Since they are the ones that warranty your battery. Odyssey manufactures their own unit for their batteries. They want you to use their product on their batteries at a high cost. Our Battery Tender Junior $39.95 will be just fine for your specific application. The float voltage on the Battery Tender Junior is between 13.4 to 13.6 well within the needed float voltage recommended from the battery manufacture. If odyssey finds out you have used our product on their battery sometimes they won’t honor the batteries warranty. Please feel free to contact me with any of your Battery Tender needs.


Thank You

Tim Salzman
Customer Service & Support
Deltran USA


My old PC680 still starts the bike but a test shows a sulfated cell. I think the battery's early problems were just a coincidence.

Hey Towerworker, thanks for sharing that information. My PC-680 also just died after a couple of cold, mostly idle seasons hooked up to a Battery Tender Jr much of the time, but I figure after 6 years of service it doesn't owe me. Sorry to hear you only got 3 years from yours. Their reported longevity varies widely, but that may be related more to differences in climate and usage than quality control. Specs say that an automotive charging system (such as ours) charges at too high a voltage (14.4V) for AGM batteries, and yet they seem to work fine, so I'll put another one in my bike right after I change the antifreeze!

My pc680 battery was sulfated by a battery tender Jr. And it would not hold a charge. When I measured its trickle voltage it was only 13.1 volts. If you try a BT Jr. Measure the voltage after a day. If it's not in the high 13s I wouldn't use it. I believe CTEK makes a good charger for AGM.

Odyssey helped me fix the battery. I discharged it to 10.2 volts 5 times and recharged it to 12.84 volts each time. That was 3.5 years ago. It has been fine since.

Part of the problem is that the oil head alternator is about 0.8 volts too low for an AGM battery, which means the alternator buts out a trickle charge voltage, making the right charger important. I added a diode inside my alternator to boost the voltage 0.7 volts.

To try and keep everything in one thread I'm going to repost this advice here too.

If your pc680 battery is fully charged it can easily last a month. A full charge is about 12.84 volts and 50% charge is about 12.2 volts. So that's 12.8 mV per percent loss. So you're losing almost 2% per day. The pc680 is a 16 amp-hour battery so you are losing 0.32 aH per day. This means your leakage current is about 12-13 mA, which is nearly three times a stock bike (4.5 mA).

What else do you have connected to the battery: e.g. Do you have an alarm, extra lights, Kisan Signal Minder? A stock bike is about 2.5 mA leakage. A Kisan adds almost 5 mA, tripling the rate of leakage (it can be modified).

Whatever charger you use on the pc680 make sure the trickle voltage is in the high 13s, e.g. 13.7ish. That's what an AGM battery requires.

Once you find the source of the excess current, pulling fuses 3 and 5 will get the leakage down to about 0.5 mA. Then you can go 2-3 months without a charge.

Roger 04 rt wrote,"
Part of the problem is that the oil head alternator is about 0.8 volts too low for an AGM battery, which means the alternator buts out a trickle charge voltage, making the right charger important. I added a diode inside my alternator to boost the voltage 0.7 volts."

Could you elaborate? I thought most automotive alternators would charge at 14.4V, which is 0.7V too high for the AGM type batteries, and that adding a diode to an alternator would decrease it's output by a standard 0.6V NP junction drop?

AGM batteries want bulk charging at about 14.8V and trickle charging at 13.8 V. The Oilhead regulator is nominally 14.0V so it's about 0.8 V low.

The diode is added into the ground lead of the voltage regulator, inside the alternator. That has the effect of moving the ground lead up 0.7V, moving the output up by that much too.

Here is a link to what I did on mine, others have too. It's not an easy job. http://forums.bmwmoa.org/showthread.php ... post907139.

RB

Bought two of these from local robotics team after they moved from Odyssey batteries to LiPo or similar:

http://www.power-sonic.com/images/power ... Jan_18.pdf

Check the specs, AGM-friendly.

These chargers pop up on eBay, where there's one listed for $25 right now.

So... a Kisan Signal Minder adds 5mA leakage, but....can be modified. Any one know the nature of this modification ?

Reading all of the above, I'll stick to my Motobatt MB51814.
It's less expensive, it delivers 22 Ah instead of 16, it gives 260 CCA instead of 200 and it works well with my Optimate 4.
Just a happy user

Also....Roger, I believe, recommended pulling fuses 3 and 5 after finding the source of the leak. Just so I understand correctly: I have a Kisan Minder installed. ( FWIW It's a great mod. ) I should pull it also if I want to lower drainage ? Pulling fuses 3 and 5 - the way I see it - will not effect the leakage caused by the Kisan ?

I have the Kisan too and like it. But as a part time rider its current drain is rediculous. I modded mine to eliminate the key off draw but for storage just unplug it. Fuses 3 & 5 don't eliminate the Kisan leakage.