Andrew

OK folks, here is an interesting tender issue. The C5 is always hooked to a battery tender. I actually have 4 of them scattered around on different toys, all of them are the Battery Tender Jr version. Anyway, noticed lately that the red light on the one hooked to the C5 would NEVER go off. So, I took one off a lawn mower, which had the solid green light illuminating and moved it to the C5 and took the red light tender and moved it to the lawn mower. After 8 hours on the C5, that light went from red to green and the light on the lawn mower is still red. 2 days later, the C5 is still green and the lawn mower is still red.

So, is this tender bad? Nothing in the instructions for troubleshooting the issue.

bc6152

Do you have a volt meter? Check to see if the tender is actually providing voltage to the attached battery. If the batteries on the various items are good, seems like no charge passing from the tender.

Vetteman Jack

Andrew - I would speculate that the Battery Tender Jr you have is not working properly. I'm not sure if they have the capability to check the tender, but you might try a place like Batteries Plus on the boulevard.

Phanni

You used a logical trouble shooting technique! It would be my guess, that the questionable tender, has a malfunction in the part that monitors the charge capacity. I suppose that could actually cause the battery to become either be 'overcharged' or burn up some of the electrodes if left on too long. I'm sure there is an expert or two here that has more experience with chargers.

Andrew

I did more troubleshooting last evening with a multimeter and not sure how to use it with the tender. First, checking continuity, OK on the tender wall plug, no continuity on the plugs to the battery. I did this same test this on a couple of the tenders with same results, some of them I know are working. Also checked Volts and 0 out of the plugs to the battery. So, it appears that it only shows continuity or volts when actually attached to the battery?? However, when attached to the battery, I get the reading of the battery, not the output of the tender. This sound correct??

I had an extra - new tender and placed it on the lawn mower. The defective tender showed a red light on it for over 24 hours. Placed the new one on it and within 10 minutes, it went from red, to flashing green to solid green.

So, only thing it could be is a defective tender. As cheap as they are, will probably just toss the old one.

Agree that a defective tender could cause problems by overcharging or not charging the battery. For those getting low voltage symptoms - error codes on the C5 and other electrical gremlins - and have a never ending red light on the tender, check the tender before troubleshooting the car or think you have a bad battery.

Phanni

It appears to me that the charger is charging, but not shutting off when the battery is charged.
(Turns on green light). I believe these unit are designed to charge at a slow rate, until the battery reaches a certain charge level, then it monitors the battery a applies a charge when the battery falls below a certain level. In a C-7 (and many other cars), there is a constant drain on a connected battery. The charger is designed to turn on and off the charge cycle as needed. Your unit seems to not shut off when battery has been charged. I say this because you don't indicate that the battery seems to lose it's charge , even though there is a drain on the battery from the car while it's simply setting there unused.

GCG

As you found out, the tenders only provide output after detecting the presence of a correctly connected battery. This is a protection against reverse hookups and also to avoid short circuits if the output leads accidentally touch each other.

Since this tender is not providing any output when connected to a battery, as you verified with your multimeter, that means it is probably malfunctioning or perhaps there's an open point somewhere along its output leads so the tender can't verify the presence of the battery and therefore it is not providing any output.

This second possibility can be easily tested by opening the tender and using your multimeter to verify if there's continuity from end to end in both output leads. Perhaps it's just a bad crimp/solder in one of the output cable ends, or simply a broken wire.

Rick Manning

I had similar issue this week. What I found out (and didn't know) is that trickle chargers come in several different configurations. I buzzed down to my local auto parts to get my Red Top Battery changed because I figured that's what it had to be. Well the guy checked the battery and told me it had a low charge and wasn't bad. He asked what charger I was using, I pointed it out to him on his shelf (1.5 amp)and was told that will not charge an AMG Battery (Red Top)? What I needed was a charger designed to charge the AMG Battery at a higher amp rating. Bought new trickle charger, 10 amp, and now all is well.