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California98Civic · 09-17-2011, 04:53 PM

I have installed an onboard voltage meter so I can monitor it live while I drive. I have a new lightweight deep cycle battery that seems to work fine. I charge it at night and in between runs with a plug in on board 1.5amp maintainer. My goal is to install an alt disable switch for short runs, such as my 22 mile round trip commute. Some observations and questions:

While in EOC during daylight the charge will sit at 12.5 volts and when I bump start it instantly jumps to 14.3 or 14.4. Back to EOC it drops to about 13.0 or 13.1 and then starts to descend to 12.5, getting there inside a minute, maybe less. Then it will sit stable at 12.5 volts.

Question is: that is quite normal, no? But doesn't it indicate that my alternator is coming on immediately upon bump starting, every time? If so, doesn't that mean that I won't really get the benefit of the deep cycle battery until I can disable the alt?

09-17-2011, 04:53 PM	#1 (permalink)
California98Civic Cyborg ECU Join Date: Mar 2011 Location: Coastal Southern California Posts: 6,299 Black and Green - '98 Honda Civic DX Coupe Team Honda 90 day: 66.42 mpg (US) Black and Red - '00 Nashbar Custom built eBike 90 day: 3671.43 mpg (US) Thanks: 2,373 Thanked 2,172 Times in 1,469 Posts	Battery mod not working out? I have installed an onboard voltage meter so I can monitor it live while I drive. I have a new lightweight deep cycle battery that seems to work fine. I charge it at night and in between runs with a plug in on board 1.5amp maintainer. My goal is to install an alt disable switch for short runs, such as my 22 mile round trip commute. Some observations and questions: While in EOC during daylight the charge will sit at 12.5 volts and when I bump start it instantly jumps to 14.3 or 14.4. Back to EOC it drops to about 13.0 or 13.1 and then starts to descend to 12.5, getting there inside a minute, maybe less. Then it will sit stable at 12.5 volts. Question is: that is quite normal, no? But doesn't it indicate that my alternator is coming on immediately upon bump starting, every time? If so, doesn't that mean that I won't really get the benefit of the deep cycle battery until I can disable the alt? __________________ See my car's mod & maintenance thread and my electric bicycle's thread for ongoing projects. I will rebuild Black and Green over decades as parts die, until it becomes a different car of roughly the same shape and color. My minimum fuel economy goal is 55 mpg while averaging posted speed limits. I generally top 60 mpg. See also my Honda manual transmission specs thread.