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first things first, i have a Shorai LFX18A1-BS12 http://www.shoraipower.com/p-155-lfx18a1-bs12.aspx. I also have a Scorpio alarm.

3 days ago i drove into the city around 8pm and everything was fine. around 2am i was going to go home, but when i turned my key, the dash was dim. i tried starting it and it turned over a couple times, but to no avail. i took my battery home, threw it on a charger and the next day i put it back in and everything was fine. it was reading 13.2 charge according to my alarm remote. i drove it all day yesterday and around 12am i drove somewhere and then again, around 2am, the battery just didn't have enough juice to start it up. could this be my r/r's fault? the alternator? how do i test these things? it's been infuriating...

thanks guys
 

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Use a meter to do some testing. Measure the charged resting voltage of the battery, like the above 13.2 reading. Turn on the key and observe the voltage, should very slowly start to drop. Then crank the engine and observe the voltage if you can and see how low it goes. Let the motor start and idle and warm up. Observe the voltage at idle and again at 5Krpm. At the higher rpm, the meter reading should be ~13-15VDC. At rest you should see 12.5-13V and at least 13V while idling. You can also check the battery leakage at rest by removing the neg cable off the battery and hooking the neg probe of the meter to the neg terminal of the battery and the pos probe to the neg cable end. Set the meter to read amps in the 20mA range. The leakage should not be more than 1mA. The motor is off when doing this test.
 

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When testing for a draw using an ammeter, always start hi (10A or 20A - most cheap multimeters only do 10A). If you have a large draw, setting the meter too low can pop the fuse in it. If the meter is not auto-ranging, work your way down until you get a good reading.

After hooking the meter up initially, you may need to let it rest for a few minutes for the electrics to calm down to their at-rest state. Less than ~50mA (.050A) is ideal for most vehicles, motorcycles should be much less w/o aftermarket accessories like alarms. If your reading is higher, disconnect the alarm and take another reading. If the draw is causing your problem, I would expect to see readings over 1A.

An old/bad battery can also not take a charge properly, causing this symptom.
 
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