Battery Tenders might fry your battery - happened to me and here is some info

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A few years ago I had a brand new tender (full size unit).
Left battery plugged into bike in the garage.
I checked on it a few times and noticed the battery was really warm.

Anyways, come time to use it and dead battery.
I no longer do that. I simply recharge once a month for 6 hours (until charged) then disconnect the charger.

I came across a post here:
http://www.motorcycle-superstore.com/28180/i/yuasa-maintenance-free-battery


Great brand as always. People! Never keep any battery hooked up to a tender all the time. It will boil out the acid in a year or less because they never shut down and monitor. Tenders take the voltage up too high and never shut down like a normal charger. A good normal charger brings up the voltage to where is is supposed to be and shuts of until it needs a little bump back up. A good charger will have a % charge meter and in most cases it has a yellow light on when charging and when it is fully charged a green light comes on. When is goes green it monitors the voltage and especially with a new battery or if down in the low 12 volt range the light will go off a few seconds or more and come back on. When you watch for several minutes and it never turns off it is holding up to the correct voltage and holding a good charge. You can make a tender connector with a small set of alligator clips and some number 16 wire ( good to use black and red wires to hook to the larger clamps on a standard charger and connect to your bike side just make sure you take a volt meter and check the ends of the tender for which is positive and negative and mark the bike connector and wires if all you have it the same color. Now your battery if a good brand will last at least 3 years or in my case I have 3 power sports batteries and some has lasted 5 to 6 years. Once a month I take my volt meter and connect to the tender cable on the bike and if it is 12.5 volts or more check again next month. Meanwhile find a trash can and through the tender away. ( you may want to cut the tender cable off and put some clips on the ends to hook to a standard charger. Just be sure to check the polarity and mark the small clips + and -)

Alan Greene - January 30, 2017
 
I've been preaching that since 2005. Now I don't offer free advice
 
For the record, a trickle charger and a tender are not the same thing. A lot of people mistake them as such and hook up a trickle charger to their battery which will indeed overcharge (and eventually boil dry) the battery.

A proper tender does shut (completely) off and then sit back and monitor the voltage, only turning back on when it detects the battery has fallen below a 100% SOC, and then again it only stays on long enough to top off the battery before again flipping off and back into monitoring mode.
 
PrivatePilot said:
For the record, a trickle charger and a tender are not the same thing. A lot of people mistake them as such and hook up a trickle charger to their battery which will indeed overcharge (and eventually boil dry) the battery.

A proper tender does shut (completely) off and then sit back and monitor the voltage, only turning back on when it detects the battery has fallen below a 100% SOC, and then again it only stays on long enough to top off the battery before again flipping off and back into monitoring mode.
Click to expand...

Concur. OP is getting trickle charger and battery tender confused. Tender only monitors battery and maintains a minimal charge. Any tender that doesn't do that is malfunctioning.
 
I used to do the same...charge it for about 2 hours every month...did not need to be charged any longer...Bike would fire up every spring with no issues...
 
Completely false in my experience , i even used a battery tender jr. on my shorai lifo battery for years .
battery tender brand will charge to max voltage and trickle charge or float until required when operating correctly.

BMW provides a similar style charger now under warranty to keep battery (undersized) on my S1000r and RR from premature failure and recommendation is to keep bike plugged in constantly or no warranty on battery.

BB
 
bought a tiny 250mA (1/4 amp) charger for ~ $6 ten years ago. put it on about once a month (for about 10-16 hours)...simple. cheap.

I think it is possible to overcharge an older weaker battery that will only hold to 12.6v-12.7v The tender at this voltage thinks the battery still needs charging and stays on; looking for the battery to hold 12.9-13.2 volts.
 
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boyoboy said:
bought a tiny 250mA (1/4 amp) charger for ~ $6 ten years ago. put it on about once a month (for about 10-16 hours)...simple. cheap.
Click to expand...

Yep, using a trickle charger occasionally during the winter months does indeed work fine so long as it's not left on longer than necessary to bring the battery back to full charge. That's the mistake people make though - they hookup a 1 or 2 amp (and even 250ma will overcharge eventually) charger thinking it's a "tender", when in reality it's not - it's a charger. It just keeps outputting it's rated voltage until it's unplugged and most do not monitor the battery voltage whatsoever so it soon passes into overcharge territory which can be just as damaging as undercharged during storage.

Some of the newer smart chargers do monitor battery voltage when on trickle (or even faster) charge levels and will at least turn themselves off when they detect the battery is full, but they will not come back on again a few days (or weeks) later when the battery needs to be topped up again to maintain their health, so they are not automatic. Some other intelligent chargers have trickle modes that turn off automatically, and some others yet do indeed have a maintenance/tender mode in addition.

For example, I have one of these:

chargeur.jpg


It had all three modes - trickle (which is typically defined as 2A or under, with auto-off), fast charge (also with auto off), and a true tender mode which monitors the battery and cycles on and off as required to keep the battery at 100%. I used it on my wifes bike all winter in maintenance mode and it worked perfectly, whereas I used a Honda tender (That I won in a contest) to maintain my VTX. Both accomplished the same thing.

The key is knowing WHAT type of charger you own. If it looks anything like this, well, it's not a tender, it's a charger.

maxresdefault.jpg
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