Tuesday, October 18, 2011

Fun With Batteries, or, How to Load Test Your Battery In The Comfort of Your Garage.

Since the Triumph is currently on time out for being naughty and not charging it's battery like a good motorcycle, I thought I might ride the Vespa to work today.

Last night I went out the the garage to make sure the Vespa was still healthy and happy and likely to start come this morning.  Sadly, it was not.  The battery has caught a nasty case of "dead."

Incidentally, you can be certain that your battery is dead and not just very, very sleepy by doing an impromptu load test with your multimeter.  You have a multimeter, right?  If not, get one.  Especially if you like European bikes.  You can get a cheap one for practically free, and you will use it a lot once you realize how awesome it is.

Start with a fully charged battery.  If you battery isn't charged, attempt to charge it.  You have a battery charger, right?

Set the voltage test on your multimeter to 20 volts and turn it on.  With the fully charged battery in your bike, connect the red multimeter probe to the positive battery terminal, and the black probe to the negative terminal.  It should probably read somewhere over 12 volts.  If it's less than that, and you just charged the battery, that's bad. 

Anyway, turn on your ignition and see how much the voltage drops.  It might go down a little, but shouldn't go down more than maybe one volt.  Hit the starter button.  If the voltage drops dramatically, you've got yourself a dead battery.

Of course, if you don't have a multimeter, and for some reason you aren't willing to shell out $5 to get one, you could also do the following: Try to charge the battery, and when it's done charging, attempt to start your bike.  If the starter blows a raspberry at you, your battery is toast.

Now when you go to get your battery replaced because it's still under warranty, you can tell the helpful employee that you load-tested the battery and it is dead, so please make with the free replacement.


RichardM said...

Good write up. It seems like the newer AGM batteries don't like to be really run down all the way. They don't seem to recover all the time. The old style flooded lead acid batteries seem to recover without an problem. I've read on the Internet that the AGM batteries require some special charger to get them back to life from a complete discharge. And the jury seems to be still out on the lithium iron phosphate batteries.

Thank you!

bobskoot said...

RichardM, via Lucky:

Regular Automatic Chargers will not charge a AGM type battery because the amps are not maintained at a constant rate, it delines as the battery builds itself back up. I was told that a "pulse" type charger would work better, but I bought a charger with a constant charge rate and could charge AGM's with no problem.

As for Lucky's Vespa woes, he should really get a battery maintainer (tender) and keep it plugged in.

Riding the Wet Coast

Gary France said...

The best advice I can give in circumstances where you don't ride a bike for sometime and there is a danger of a battery going flat is to use a battery tender. The unit comes with two short leads that you connect to your battery and leave them there permanently. They stick out to somewhere where you can see the ends. Then every time you park your bike, connect the leads to the battery tender and plug it in. It is like a trickle charger that you leave plugged in every time your bike is in your garage. I use them on two cars and two bikes , then whenever I want to use up particular vehicle, the battery is always charged. Brilliant.

Lucky said...

Yeah, I guess I'll get myself a proper battery tender. My current battery charger was supposed to work as a tender as well, but... it didn't.

Charlie6 said...

Battery tenders, are less than $30 and are a must for motorcycles....

if I might add a few notes to your informative post: to test if your alternator is charging, you use your multimeter as described, but with engine running. It should read somewhere around 13.3 or more if your alternator is putting out power. Note, older bikes tend to not "charge" till rpm's reach a minimum level....my airhead for instance won't really out out amps till around 2000 rpm or higher.

12.0 volts, btw is really low.....my motorcycles tend to get balky below 12.2 volts.

batteries should also be measured "at rest", to get an accurate voltage reading....so, after a couple of hrs after riding for instance.

went through a lot of this research when I was "total loss system" when riding the Ural: LINK


Redleg's Rides

Colorado Motorcycle Travel Examiner

Anonymous said...

this is my 1st yr riding, so my motorcycle's 1st winter in the garage is coming. would you say battery trouble is more likely due to low ambient temps or long intervals between starts? I plan to run the bike whenever possible, weather, road conditions, and my tolerance for bone-chilling cold permitting. I certainly plan to start and warm the engine and fluidsd at least once a week. What else do tyou guys suggest?

Lucky said...

Charlie6 - Thanks, that's some good information!

NoName - I think long periods of not running are worse than cold temperatures. As everyone mentioned, keep the battery on a tender. If you're not going to ride for a long time, you might look into winterizing your bike.