Battery at 12V, but low voltage throughout system.

Norton7d

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So I assumed it was my battery which was responsible for dim lights, no E start, etc when not running...Ive always run a battery tender but I assumed due to lack of riding her, the battery faded even though 1 month ago, she started just fine.
Started to diagnose if I had a draw then I said, why dont I check the battery voltage first....sure enough, with it inplugged from everything, its right around 12.
So the good news is the battery seems fine, or no?
But if so, why the low power for all the systems, The voltage meter I added which runs off brown wire in headlight shows below 8 and it drops quickly if I hit the lights or the starter.
Once running after kick started, the meter shows around 14, as expected.
Ita a 2 year old gel battery that just ran past warranty but once again, I dont think its the battery.
So whats the usual culprit, positive and or negative cable is poor, poor connection(s) somewhere?
I guess I need to start testing various spots to see where it goes from 12 to less than 10 and below, correct?

Thank you.
 
Get a volt meter ON the battery, then turn on iggy, accessories, hit the starter, see what happens.
Dunno but the failure rate on gel type batteries still seems awful high...
I'm guessing a weak cell in the battery is going to be the issue. Battery failure is frequently one cell that craps out, battery looks good til a load is applied then that bad cell drops out and a 12 volt becomes a 10 volt in a heart beat.
And yes a full on electrical maintenance is always a wise start to trouble shooting; cables, connectors, grounds all are "need to be checked, cleaned" items over time.
 
First of all a 12.0 V measured on a battery with no load on it, and using a digital meter, means the battery is totally discharged. Possibly dead.
A healthy, fully charged battery should measure 12.6 volts. This may seem like a small voltage difference, but it is not. 12.0V is nothing, 12.6V is 100%.
Correct charging voltage is usually between 14.0 and 14.5V. So when measuring the battery voltage, it needs to be disconnected from the charger for a while, and maybe "loaded" a little bit before measuring, using a small bulb or something similar, to ensure a good voltage reading.

Here is just some battery voltage rambling: Due to the internal resistance of the battery, the voltage across the battery poles drops when a load is connected. On a car, cranking the starter may pull the voltage down several volts, due to the starter drawing 100 Amps or more. Which is why some automotive coils used to have a ballast resistor wired in series with the primary winding. When cranking the starter, the resistor was bypassed, to ensure a strong spark even when the battery voltage was temporarily 10V or less. When running normally, the primary current was going through the resistor, as the voltage then would be around 14V.
 
Thanks Gary.
I checked again, the V is at 12.6ish at the battery but the moment the key is turned on, it drops doen to the 7's and keeps falling into the 6's.
Time for a new battery, so be it. Anybody running lithium?
I will do a search.....thanks again.
 
As I see it it can be two things
a short
a battery that is gone
On a regular battery these can be tested at a gas / service station ..or a shop somewhere it is a less than 2 minutes test
if the proper tool is there
Finding a short is a lot more difficult.
So Perhaps charging the battery and then take it to a testing point and go from there..
If a new battery is installed some check of the charging physics would be next.
 
Thanks Idaho Mike...good idea although I dont have any other MC batteries to perform the test. Other than a 6 V for my XT500. i assume a car 12V is not advisable.
 
Well I hadd the battery tested, no good and couldnt handle any load but to the bigger issue, the battery tender had went to crap as well.
At this point, both parts replaced and lesson learned regarding the BT...I should have thought something was up when the red light was on way too much, thus the BT was struggling to keep up even for maintenance, and was never going to fully charge a declining battery.
Lesson #2, Ride it more and this wouldn't happen!
 
12 volts is 12 volts, a car battery would work just fine.
Not at all. A small, partly or totally discharged motorcycle battery will draw a huge current from a car battery. Which is not a good thing at all. And I have actually tried that, when I was young and ignorant. There is a reason for that old "10 percent rule of thumb" Which means that the recommended maximum charging current is 10 percent of the battery capacity. So a 14 Ah battery really should not be charged with a current over 1.4A. Hooking up a healthy car battery will easily give 20A or more......
 
A fully charged car battery will show 12.7 volts , well below the threshold to do much, if any, charging, unless there are some shorted cells the bike battery wont see enough current to cause a problem, the juice stops flowing when the voltage is equal in both batteries. it will only draw enough current to satisfy the needs of the bike electricals being switched on. However, if you start the car and the car alternator starts charging, then you would have a problem.
 
A "safety" jump uses a light bulb as a current limiter but wouldn't be enough to run the starter. Works for a "too big" charger also. a turnsignal bulb will limit charging to about 2amps.
 
Is it something I don't understand here in today's heat ...climate
two batteries A --- MC + B --- Car
Why not just disconnect the A put it away in a corner and Insert B at the Ground - and + Connection ..at 12 V upstream from fuses
If a short wont the fuse save the day and if no short the test is performed ... A battery is defect
 
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