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Old 10-14-2014, 04:02 PM   #1
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Battery suggestions

I want to install a 2nd battery in my F150 tow vehicle. Purpose of this is to have extra 12v capability for "stuff" including a Ham radio rig in the truck, when not running.

I am thinking of putting in a 12v deep cycle battery, also, i would like to tie in the 2nd battery so that it charges automatically but does not allow the primary, starting battery to be run down.

I am curious to get suggestions on the specific battery to use and wiring suggestions.

Thanks
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-2009 Ford F-150, SuperCab w 8 ft bed
5.4L Screw, 3.73 rear, 8200 GVWR
-2011 Rockwood 2604, 2x6V Interstate U2200 batteries,Yamaha 2400 genny
-2011-23 nights
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Old 10-14-2014, 10:57 PM   #2
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Boats that anchor often or spend time under sail usually have a house battery and a starting battery - which is similar to what you are asking. But typically the house batteries are deep cycle battery banks recharged by a high capacity, separate alternator belted on the engine. The starting battery is reserved strictly for engine starting and has a normal alternator. While there is typically a manual switch to cross connect loads for emergencies, this would not be used in normal practice.

Allow me to rephrase the problem to be solved:

On the charging side, you want both batteries to charge automatically from the same alternator and regulator, even though the batteries are not matched and are isolated. Can't be done without at least adding a separate regulator for the 2nd battery. And then it depends on whether the regulators adjust the voltages and currents to the battery, or adjust the alternator to supply the correct voltage. Because unless the batteries are matched and kept in parallel (not isolated), the charging regimen and requirements for each will be slightly different - and you wanted the batteries isolated.

On the load side: when the engine is off, you want the starting battery isolated and the 2nd battery supplying the load. When the engine is on, you want the 2nd battery isolated (but charging) and the starting battery carrying the load. The load switching could be handled by a relay wired through your ignition switch.

The above are general principles. The specifics are going to depend on the details of your ignition switch, alternator, and regulator.

The simplest solution is to run the extra stuff off the 2nd battery only, and recharge as desired from the Yamaha.

Fred W
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Old 10-15-2014, 03:21 AM   #3
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Seems like this would do what you want... http://amzn.com/B001DKRF2M
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Old 10-15-2014, 12:05 PM   #4
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Quote:
Originally Posted by pgandw View Post
Boats that anchor often or spend time under sail usually have a house battery and a starting battery - which is similar to what you are asking. But typically the house batteries are deep cycle battery banks recharged by a high capacity, separate alternator belted on the engine. The starting battery is reserved strictly for engine starting and has a normal alternator. While there is typically a manual switch to cross connect loads for emergencies, this would not be used in normal practice.
............
Fred W
Fred,
you raise an interesting point....do deep cycle batteries need a "different" or separate alternator/regulator for charging them as opposed to regular batteries??
That obviously needs to be defined before anything else can be decided....

I do want the system to be fully run by the car engine, as I see this as an emergency set up, where I may not have my generator with me.
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-2009 Ford F-150, SuperCab w 8 ft bed
5.4L Screw, 3.73 rear, 8200 GVWR
-2011 Rockwood 2604, 2x6V Interstate U2200 batteries,Yamaha 2400 genny
-2011-23 nights
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Old 10-15-2014, 12:06 PM   #5
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Quote:
Originally Posted by castlemusic View Post
Seems like this would do what you want... http://amzn.com/B001DKRF2M
Looks interesting and might be exactly what I need as part of my set up. Have you used this???
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-2009 Ford F-150, SuperCab w 8 ft bed
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-2011 Rockwood 2604, 2x6V Interstate U2200 batteries,Yamaha 2400 genny
-2011-23 nights
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Old 10-15-2014, 03:07 PM   #6
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Originally Posted by toshu View Post
Looks interesting and might be exactly what I need as part of my set up. Have you used this???
I have not, but I remember growing up we had a slide in camper (remember those?) and my father installed one of these to feed a second battery off the factory alternator. Worked fine, as far as I can remember!
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Old 10-16-2014, 04:48 PM   #7
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Originally Posted by toshu View Post
Fred,
you raise an interesting point....do deep cycle batteries need a "different" or separate alternator/regulator for charging them as opposed to regular batteries??
That obviously needs to be defined before anything else can be decided....

I do want the system to be fully run by the car engine, as I see this as an emergency set up, where I may not have my generator with me.
You CAN charge them both off the same alternator/regulator. That's what happens with standard camper wiring - the camper battery(s) is/are put in parallel with the tow vehicle battery. The charging regimen is optimized for the tow vehicle battery, however sensing will be thrown off by the charge state of the camper battery if it is significantly different.

Bottom line is that recharging of a deep cycle camper battery by the standard tow vehicle setup will be much slower than if an optimized charge regimen was used (assumes a fairly discharged deep cycle battery in the camper).

Some truck tow packages have a cutoff relay that prevents the camper from taking power from the tow vehicle battery when the ignition is off - but certainly not most tow vehicles (mine don't have that relay). Without that relay, the camper can run the tow vehicle battery down to nothing during an overnight stop if the fridge is running on DC.

But the above is not what you originally asked. You specifically wanted the extra battery to be isolated and not be able to drain the starting battery when in use.

The simple way to power your ham radios is to wire the extra battery in parallel with an ignition-driven relay installed to disconnect the extra battery when the ignition is not on. The ham radio is wired only to the extra battery. You accept the slower charge rate (takes much longer to fully charge) of the extra battery as the cost of simplicity and automation. If the extra battery is drained, your ham radio is inop. If you leave the ignition switch on with the engine off, you will drain one battery into the other if they are at different charge states.

just my thoughts, yours may differ
Fred W
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