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Old 03-26-2011, 09:44 AM   #11
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Re: Battery and alternator questions

With a little luck, I can EOC for nearly a mile in some locations.
The car doesn't DFCO without downshifting or starting at highway speeds. Both which means losing too much speed for a coast.
To keep costs down, starter battery plates are made of a foamed alloy to increase surface area. Which is fine for their intended job, but doesn't last once it starts getting used as a deep cycle. On top of that, this battery is probably the smallest one GM could get away with, and I likely didn't let it fully charge between EOCs at times.

I did get a chance to check the voltage between the battery posts with the car running after a drive. Voltage was below 13.8, so I won't worry about an AGM. Just got to fix up the wife's car first.
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Old 03-26-2011, 01:37 PM   #12
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Re: Battery and alternator questions

In my Buick, I run dual batteries. One is a regular starting battery, and one is a marine deep-cycle (27 series).

I have a high-amperage switch that connects them when I want, and disconnects them when I want to run some hi-amperage stuff off of the deep-cycle without affecting my primary battery. (Mostly the electric fans and nitrous bottle heater while I'm at the dragstrip between rounds).

A better option is a battery isolator. That would allow you to run most of your components on the deep-cycle (if you re-wire accordingly), without discharging your starting battery, but whenever system voltage is high enough it will recharge both batteries.

And BTW I have an extra isolator that I'd be happy to send you for the cost of shipping - NIB...

(The disadvantage to the isolator system is that you can't start the engine from the deep cycle, so if your primary battery dies then you have to get out some jumper cables. In my Buick, there are times when I need a WHOLE lot of amps to start the engine, so I frequently have to use both batteries as "starting" batteries, and the high-amperage switch allows me to do this. But if you install the system as I describe above, you should be fine.)

-Bob C.
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Old 03-26-2011, 09:43 PM   #13
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Re: Battery and alternator questions

You should have the battery back up to 14-14.25 volts before you shut it down or else get a 110 volt charger to top it off from the grid. What kills a battery fast is leaving it not fully charged. Also getting down to 10 volts is too low, 10.8 volts is a dead battery I.E. 100% discharged which will really shorten the battery life. Engine off coasting a mile is not a problem but not charging afterwards is a problem.
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Old 03-29-2011, 07:06 AM   #14
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Re: Battery and alternator questions

Quote:
A better option is a battery isolator. That would allow you to run most of your components on the deep-cycle (if you re-wire accordingly), without discharging your starting battery, but whenever system voltage is high enough it will recharge both batteries.
The battery isolator sounded like it could be the ideal solution. I figure the lights, fans, and radio are the main draws while off. Could I just wire the second battery into the main fuse panel? That seems to be the simplest way, but I haven't played around with automotive electrical systems. The main hold up was cost, but if you are willing to part with an isolator, I won't complain.

The battery was replaced within the first year. It's a 6yr battery coming on 5 years of age. So replacing it before winter would be prudent.

When I measured the voltage at posts the engine was running. The info I had said this was a measurement of the float charge on the battery, not the battery's voltage. This was after a 50 to 60 minute drive without EOCing, and the scangauge reported 14.5 volts at times, so the system did enter charge mode during the ride.
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