Modern Vespa

My battery tender has been acting a bit odd, it seems, lately, which has me wondering how they fail. I initially never gave failure a thought, but it's been mentioned here, and, well, nothing is forever.

I connected one of my scooters (with a new battery last year) to the tender last week after a couple of weeks sitting, light turned green in an hour or two. The second scooter (with a battery of unknown age) stayed on red and I left it a couple of days when it finally turned green when I checked on it. I assumed that battery may be bad (bought that one used and not sure if it was ever replaced), but today connected the scooter with the new battery, and it never went to green. Hmm.

Anyway, sorry if that's confusing, but bottom line is, how do I know when I have an issue with the tender vs. the battery?

How long did you wait for the reconnected battery to go green?
Even though it had been connected a few days earlier, it could take a while for the light to turn solid from the parasitic drain on the battery.

Battery tenders can fail in a variety of ways. It usually results in 1) the battery not being charged, or 2) the battery being over charged. Not charging is annoying. Over charging can ruin a good battery ... even more annoying!

I've personally had one battery tender failure. It was type #2 and cost me an almost brand new battery.

Just want to add, I think you can speculate but can't make a definitive conclusion without first verifying that the batteries are in good health, especially the unknown one.

Batteries in poor health will make your battery tender act all kinds of weird, so you can't expect normal results from batteries that may not be in normal good health.

First thing I would do, get a battery load tester. They're like $40. It will tell you GOOD, OK, or BAD. I'd make sure your batteries are in fact GOOD. If it's OK or less, it could be the reason your battery tender appears to be acting wonky.

... or maybe it is in fact acting wonky, totally possible too, but I'd buy the load tester and make sure my batteries aren't the problem

PS: For context, I run a motorcycle winter storage program, have about 25+ battery tenders going all winter, every year, haven't had one fail me yet... Kind of afraid to mention that in case I just jinxed myself haha

Another answer version: It depends on what brand. I've seen a newish pricey deep cell bass boat battery ruined by a runaway tender which was a Sears DieHard brand.
Battery Tender-the brand- I've had many of them and still use whats left. I've had several of their waterproof bigger ones overheat electrically and sort of burn up, melting the black waterproofing material which oozed out. I've had several that just stopped working at all. I've had several that were bought new with me thinking they were warrantable to learn they had older shelf dates and no coverage left.
I've moved on to other brands with more versatility as my Battery Tender brands fail, CTEK has many choices with features galore and I have a Marinco thats OK so far.

They all fail internally with a circuit board death I suppose.

Best advice so far above is to own a good battery tester.

I have found that the battery tender brand seems to be the most reliable in the US at least. I've only had one fail and that was the battery tender Jr. after a few years.
I prefer the battery charger / maintainer over just a maintainer.

Thanks. This is the battery load tester I use/recommend for those who might be interested in buying one: https://amzn.to/3mT4618

If you can connect two clamps and press one button, you can use it because it's that simple. Just make sure you fully charge the battery first, then connect the clamps, then hold the button for up to 10 seconds. If you don't fully charge it first you'll likely get a false negative.

PS: I wonder if your Del-Tran Battery Tender's failed because they were the waterproof models. Maybe they're toooo well sealed and overheated or something? I've had 20+ of the non-sealed Del-Tran Battery Tender Jr's, some are the newer thinner more efficient ones, some are the original fattery heavier ones from 15 years ago, zero issues for now...

My only battery tender failure was with a "Battery Tender Jr" (the newer lighter style). I suspect it was a heat related failure. This happened when I lived in Arizona and my garage stayed >100F for 4-5 months at a stretch. Electronics are funny that way. You can have a great product w/ solid design, but failures can still occur.

I had the same "heat thought" on the waterproof BT's as the board inside is totally filled with black asphaltic or plastic goop. I've owned big BT';s both ways and several JR's as well.
On mt Cub Cadet ride mower I have a JR that light acts weird even with a newish wet cell typical mower battery. I honestly don't know what's the reason but given the reality it always starts for the two years I've owned it & with the battery it came with and I just use it.
I bought the DieHard when Kmarts were all selling out thinking they'd be OK. Cost me a pricey battery! When my BT JR in 6 volts failed I bought the Marinco on Amazon as it had a 6 or 12v feature. It's been on my RV most of the time since then and tells me info I don't get with a BT brand-plus a great price point.

Can't recall for sure, but scooters are in my mom's barn, and I get down there every week or two....typically I'll plug in the tender and it's a couple of hours for the tender to cycle red/blinking/green, sometimes longer. Pretty sure they sat for a week this time. Last time the LX with the new battery took less than an hour, the BV with questionable was the one I had to leave on. This time the BV took a couple of hours, and the LX went from red to blinking green and back to red. However, I'm wondering if the connection with the extension cord was loose...but then it shouldn't be blinking green, either. I dunno, do gremlin bells work when parked? Besides, I only have one to share between the two scooters.

To add to the mystery, I have my GTS at home, kept topped up on the same schedule, brought the tender home and plugged it in....normally it's an hour or two to top up, today, after being plugged in overnight, it's still flashing green.

It would make sense to just buy another tender with my current arrangement. It would be interesting to see how the two would compare.

That load tester seems like a pretty handy thing to have around. I didn't know they were so inexpensive.

I really need to resist the urge to buy special purpose tools like that. Is there a 12-step program for tools?

Yes....1st step, buy a specialized tool to inventory all of your tools

I've been using Battery Tender Jr (BT Jr) for more than a decade. I have one on my small tractor (Yeasu battery), 1100cc BMW motorcycle (Yeasu battery) and car 250 Ah battery. I also had a 2009 GTV 250 with a Motobatt battery.

Years ago one of the BT Jr LED wouldn't turn green when connected to my a Yeasu battery after 24 hours, which was not typical. To determine if it was it the BT Jr or the battery failing, I swapped out the BT Jr for one of the others I had. After a few hours, the BT Jr charging light turned green, implying my other BT Jr had failed.

I did some I'net searching to see if anyone had been able to determine what failed. Turns out an electrolytic capacitor commonly fails. I have an electronics background and a well stocked electronics store close by so disassembled the filed BT Jr and replaced the capacitor. The BT Jr lasted another 6 months and then failed again. I chose to recycle the failed BT Jr and purchased a new one.

My practice is to leave my battery's on the BT Jr whenever I'm not using the machine, be it my tractor, MC or car. I did the same thing with my 2009 GTV with a Motobatt battery. I've never had a machine fail to start and the starters turn with "gusto". My machines are kept in a garage with temps ranging from 50℉-70℉s.

Surprisingly enough the BT Jr has charged my car 250 Ah battery from flat when we left a light on overnight (didn't close the trunk lid properly). The BT Jr likely didn't fully charge the battery overnight but it was charged enough to start the car the next day!

Miguel

Finally unboxed my daughter's Xmas present yesterday and hooked it up to my other scooter. Now I don't have to keep swapping back and forth.
Especially want to keep an eye on that miserable little 6Ah Piaggio fitted in my Liberty.....and no room for a more powerful battery.
Replaced my Kymco's stock 8AH with a 14Ah Yuasa. Which was only 5mm taller.

O.S.

When you buy Battery Tender units it matters to know the mfg date! Buy fresh ones only. Even though their warranty is long it begins then, not when you bought it new! Your invoice date is not what they go by.
I learned that one the hard way. I too have had very mixed lengths of service time from them.

I've been using battery tenders for more than 20 years. I currently have seven bikes, and some of them don't get ridden that often. I've never knowingly had a battery damaged by one. I started out using Deltran Battery Tender Jrs. I had one fail after more than 15 years. No lights at all. I ordered another one to replace it with. It was nothing like the other one. It was thinner, very lightweight, had a cheap flimsy feel. It failed within a few months. The light stayed red. I put one of the older ones on that battery, and it quickly turned green. I gave up on the Deltran brand, and went with one of these https://www.autozone.com/test-scan-and-specialty-tools/battery-charger/p/duralast-2-amp-6-12-volt-battery-maintainer/613874_0_0?searchText=DL-2D over 4 years and it still works fine. I've heard that starting/running the engine with a battery tender connected can damage it.

Sooo, was it the tender or the battery? Did you get the tester? What happened in the end?

Tester and new tender arriving early this week. Should be able to get things sorted Tuesday.....

Didn't take time to do the battery testing, but hooked up the new tender, which went from flashing green to steady green within the hour on all three, which is what I'd expect on recently topped up batteries. Plugged in the old one and notice it went from steady red to flashing on irregular intervals and back to steady.

So yeah, the old tender is wonky....