I have a 79 F150. I'm not sure what battery group I should buy. The battery in the truck is much smaller than the battery tray. Any help is appreciated.

 

The tray should hold a Group 27F,

 

That's correct. but the 24F is the most common replacement.

The F means the posts are reversed from a standard , today rather than F most batteries are marked R , or if you get one with the posts centered on both ends it doesn't matter.

 

Thank you both.

 

All my other Fords except the Mustang use Group 65s, so I put a carefully cut piece of 3/8 plywood treated with a 1000 year preservative black paint in my tray to raise the battery to clear the tray sides, have a lip on the front of wood too, made a new top hold down, new J bolts, put a group 65-2 in my '77 too, but I did previously get over 13 years out of a NAPA Legend 75 group 24f battery., it was down to measuring under 450 CCA on our store tester thing. I think a 27F is about same CCA as the 65-2 I put in.

 

And....make sure you do not get the + - confused come connection time. Use a white paint marker on the raised + , - on the battery body.

Make sure you use shorter red cable on the +. And a longer black cable on the -.

If you make a habit to always put the battery in with the + to the back (closest to the starter solenoid) only the red short cable will reach.

Always connect the RED + POSITIVE cable 1st. When installing the battery.

The red bearing grease on the connections helps prevent corrosion way better than those red/green felt washers.

I am NOT a fan of the battery connection where the lead end has the cable molded into it. I have had elec connection problems in the past due to a bad internal connection, and it was a PITA to locate the issue. I always use a clamp down wire style or at least a quality one like below.

Connector
Ends
Crimp tool

“When disconnecting the cables from the old battery, disconnect the negative first, then the positive.
Connect the new battery in the reverse order, positive then negative.”

 

Ground side gets disconnected first if removing a battery ... but gets connected last if installing a battery. That way if a wrench slips and hits something grounded or if the ground lead flops over onto the other post, no sudden welding light show happens.

Connect the ground first, then start wrenching on the bolt to tighten the hot side, swing that wrench far enough to touch any ground while it's on that nut, suddenly it's gonna be a "hot time in the old town tonight".

Until that ground is connected to the battery, all is safe unless you lay the wrench across both posts at once.
Best bet is to just cover that hot side with a shop towel or other insulator before even messing with the ground.

 

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I feel this is a great time to post a link to this thread. https://www.ford-trucks.com/forums/1...sa-to-all.html
And I will just copy and past the good stuff here.

"Folks, NEVER touch a tool to either end of the positive battery cable while the negative battery cable is connected. If you must change a battery, disconnect the negative battery cable first and reconnect the negative battery cable last.

If you fail to follow this order and make one wrong move with the wrench, it will cut through your hand like butter when it fuses in two, and impale anyone who happens to be standing in just the right place. Even worse, the spark created from this event may ignite fumes around the battery, causing it to explode and blind you.

In fact, this order is required for any hot-at-all-times load. Starter solenoids, back of the alternator, headlight switch, un-switched fuses (brake lights, cigar lighter, etc): disconnect the negative battery cable first, get in there to do what you need to do, then reconnect the negative battery cable last.

If you perform a "parasitic draw" test with a series-connected test light or ammeter, use the negative battery cable. Battery cut-off switches go on the negative post. These trucks are negative-earth vehicles. Do not ignore the negative battery cable. There is in fact such a thing as a positive-earth vehicle, in which case the procedures I've described are backwards - but that is not the case with these trucks and most other vehicles you and I interact with on a daily basis.

Do not deviate from this advice for any reason, no matter how much you're in a hurry, where the vehicle happens to be stranded, what your dad has always done, whether you think I'm full of it, nothing. Pass this on to your kids. There are too many blown fusible links and burnt up wiring harnesses because of people being careless. I have seen some bad dash fires and they are almost always caused by stupid people.

And, no matter how silly you think it looks, always wear goggles when working near a battery. Never underestimate the power and sheer strength of a lead-acid battery. Treat batteries with the same care and common sense that you do with your firearms. They are just as dangerous in the hands of a careless individual."

 

I went with a group 24F Everstart from Walmart. I've had really good luck with them over the years.
With the truck not having any accessories I saw no need to go with a group 27.

I had to replace the battery tray, + cable, bolts and hold down.

 

[QUOTE=tbear853;20672212]All my other Fords except the Mustang use Group 65s,
I cant even get the 65S anymore in the Las Vegas area. I found that out about an hour ago. They only carry the 65 and 65N now which seems stupid since this is a hot climate. How do these two compare to the 65S?

 

[QUOTE=1browski;20673747] Don't know about 65S as a number, I ment "group sixty five"s like multiples. Even when I said a 65-2, the -2 was added by the manufacturer, but it's just a better 65 than a cheapest 65 we sold. Seems the 65-2 is rated 850 CCA. I have two spares in the basement, in a wheeled cart. One is the OEM Motocraft battery out of our 2001 Mercury Grand Marquis that I replaced before vacation in 2006, we did Rt 66 whole way. I tender it, it's served a couple stints in police cars and a Thunderbird, it's a great battery.