Motorcycle Forum banner

1 - 11 of 11 Posts

·
Shaper Of All Things Metal
Joined
·
2,802 Posts
Discussion Starter #1
I've got a Schumacher Battery Tender/ Maintainer. It has the three indicator lights... green- for fully charged, red- for charging, and yellow for a defective battery.

Last winter I left it hooked up all winter only to find a weak battery this Spring. Did some checking and found a blown in-line fuse in the bike's charging pigtail.

But, in checking for problems I used my multi-meter to see what the charger output was. Couldn't get a reading. Since it has proven by use to be working, apparently the charger needs to sense a load to start charging?

How does one go about testing a battery charger/tender?
 

·
Shaper Of All Things Metal
Joined
·
2,802 Posts
Discussion Starter #5
Well sure... battery doesn't charge, tender no good (unless the battery is bad). Indicator lights no worky... tender probably no good. Throw it away and get a new one. Simple enough.

Thing is, idiot lights in vehicles have never proven to be 100% trustworthy and I imagine the lights on the tenders might not be 100%. Maybe all the lights on the tender are functioning but the output is weak. I was just wondering if there was an easy way to test the tender.

Some googling brought up ways to hook up resistors to simulate a battery load and trigger the tender. So there is a method but it isn't quick and easy enough to make it practical IMO.
 

·
Pale Rider
Joined
·
528 Posts
Testing a battery tender is easy: hook it up to a known good battery, connect a voltmeter across the battery before, and during the tender's connection to the battery: measure the battery's voltage without, then with the tender. The battery, if known good, should read around 12.6-12.8 Volts, without the tender connected. With the tender connected, and in a charge mode (check its lights to see what it is doing), the battery's voltage should increase to above 13 Volts, over a period of 5-10 minutes, as this indicates it is being charged by the tender, similar to what the alternator does in the bike, running down the road. If the battery's voltage never changes with the modes of the tender, then it is not working properly.

In short, measure the voltage across the battery without the tender connected, then measure the voltage across the battery in the different modes of the tender: charging should show a voltage above 13 Volts; near full charge, the voltage may be lower, but it will still be above 12.8 Volts, and in monitor mode, it should be 12.6 Volts, flooded battery, or 12.8 Volts, AGM battery. Cheers!
:coffee:
 

·
Shaper Of All Things Metal
Joined
·
2,802 Posts
Discussion Starter #7
THANK YOU Sgt! Exactly the info I was hoping for. When the bike goes back into winter hibernation, it'll be nice to know there's a way to make sure the tender is doing its job.

I use several battery maintainers on my tractors, mowers and utility vehicles throughout the winter and have had the indicator lights not be dependable on two occasions over the years.
 

·
Greatest Member Ever
Joined
·
662 Posts
SgtSlag is correct in theory... BUT... One must also point out that some of today's more "smart" chargers would fail that test. Even the cheapy tenders have some smarts to 'em... The best way to test a tender (or charger for that matter), is to use a known good battery, and stress it using a load checker... then read the output of the battery, then connect the charger and read the output of the battery. A fully charged battery will not draw power from a tender. A stressed battery will.

Jack
 

·
Aging & Worn
Joined
·
4,517 Posts
................ A fully charged battery will not draw power from a tender. A stressed battery will..........Jack
In fact, that's the way the Deltran Battery Tender Jr. is designed. To NOT attempt to trickle-charge if the Battery indicates "full charge." It falls back into a monitoring mode.


-Soupy
 

·
Pale Rider
Joined
·
528 Posts
Well, OneEyedJack, I was actually speaking from personal experiences. I've had three different brands of smart trickle chargers over the past nine years. The first three models I used, were all Battery Tender Jr.'s. I sold two with their bikes, but they worked flawlessly. The third was replaced when I ran it over with the car. It's replacement was a model from Wal-Mart (half the price of the BT Jr.). It started over-voltaging the bike after two years of use, 15.5+ Volts (AGM battery, which should never have more than 15 Volts applied...), so I bought another model from Harbor Freight, to try.

All three models behave the same, per the Voltmeter on the bikes: regardless of the battery's voltage on connection, they go into charge mode, applying 13-14 Volts, initially, for around 5 miniutes to a few hours (depending upon the actual charge level), before switching to topping off mode (<14 Volts), followed by monitoring mode (12.6-12.8 Volts). The first two bikes had switched, automotive Voltmeters installed, which I only checked occasionally, to monitor the health of the battery, and the charging system -- switched so they would not drain the batteries over a few weeks' time. My current bike has a 'smart' battery monitor, with an LCD display, which takes even less current to operate (would take a couple of months to drain the battery, all by itself).

Smart trickle chargers are computer controlled, but the computer takes an average voltage reading, over time, to determine the charge state of the battery. Some batteries will show a good level, initially, then fail when a load is applied. Some will show a good voltage at first, when the bike is shut off (fully charged by the alternator while riding), then drain to a lower voltage reading after resting a couple of hours. Voltage readings, over time, are the only way to be certain of a battery's charge level, so the smart chargers monitor it over time, assuming that the battery needs charging upon initial connection. They do not, however, perform any type of load-testing. Some of the newer types will even try to de-sulfate the battery, with a high-frequency AC signal on top of the charging current. Almost impossible to tell if they work, but they're out there -- for lead-acid batteries only, though.

My 'smart' battery monitor (mine is similar, but made for motorcycles -- no longer available) reads the voltage drop during starting, to gauge the life left in the battery, to warn me when it gets tired -- this is basically load testing the battery, under real starting conditions. It doesn't seem to be terribly accurate, as it dropped my brand new AGM from 100%, down to 68% life left in it, after just two start-up's; now, after two years of use, it is down to around 62%, so it is declining very slowly, as I would expect. Still, it is better than a straight-up Voltmeter. Cheers!
:coffee:
 
1 - 11 of 11 Posts
Top