Author Topic: cb350f parasitic drain on battery  (Read 147 times)

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Offline daveybaker

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cb350f parasitic drain on battery
« on: September 15, 2019, 03:47:46 pm »
New battery will die if bike sits for a few days. I did this test with the multimeter: removed neg cable, attached one probe to battery and other to free neg cable. Multimeter shows draw of about 2.5. All I've read suggests pulling fuses to locate the cause, but this bike only has one fuse and when I pull it the multimeter still shows a draw. What can I do next?
Thanks!

Offline scottly

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Re: cb350f parasitic drain on battery
« Reply #1 on: September 15, 2019, 06:28:36 pm »
Multimeter shows 2.5 what? Volts? Amps? Is the wiring stock, or have there been additions? Is this something that just started?
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Offline Spanner 1

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Re: cb350f parasitic drain on battery
« Reply #2 on: September 15, 2019, 08:36:58 pm »
Yes, 2.5 what ? However any reading on  a meter as described with stock wiring and the ignition switch 'off' would suggest a bad rectifier. The rectifier is connected to the battery 24/7once the battery is installed, ignition on or off doesn't matter. So it's the only thing that can drain the battery just sitting. If it takes time to drain then one of the six diodes in the rect. is shorted out. The common cause of that is either a charger attached to the battery ( installed ) with the + and - reversed  or,  a car type charger applied to the battery ( installed ) which allows a too high voltage to be applied to the little bike battery and fries the stock rectifier :( You can easily test the rectifier for correct function with a digital meter with 'diode setting beeper '. Do a search on this forum for the procedure. Good luck.
« Last Edit: September 15, 2019, 08:43:00 pm by Spanner 1 »
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Offline Bodi

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Re: cb350f parasitic drain on battery
« Reply #3 on: September 15, 2019, 08:46:04 pm »
It can't be 2.5 amps, stock batttery is 14AH and would be flat dead in well under a day... plus whatever was drawing 2.5A would be very hot and rather obvious (smoking or on fire).
The likeliest culprit is the rectifier. The diodes can fail leaky. Otherwise... corrosion on the keyswitch, few other components have unswitched power and could leak it to ground.

Offline PeWe

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Re: cb350f parasitic drain on battery
« Reply #4 on: September 17, 2019, 03:24:29 am »
Rectifier issue?
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Offline daveybaker

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Re: cb350f parasitic drain on battery
« Reply #5 on: September 19, 2019, 02:28:27 pm »
Thanks all pointing me in the right direction. Turns out I don't how to read a multimeter (no surprise haha). Decided to replace the regulator/rectifier with a 2 in unit from 4into1, and found out that my battery, though only a few months old, had a bad cell. Shop replaced it for free so now I'm good to go plus have a new charging system.

 

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