This post is to replace the one in the tech folder that has a broken link.
Sometimes it is not obvious that you have a battery problem. Because of this, I own a load tester. It is a GREAT tool to have. If you do not have one, the auto parts stores will be glad to test your batteries.
Once you have identified that you have battery issues, it is usually advisable to replace both batteries. Since the batteries are connected in parallel, if one battery has been bad for awhile it most likely has resulted in the other battery carrying a bigger load and shortening its life. If you only replace one battery at a time, you can get into a vicious cycle of frequently replacing a battery and may even get stranded.
Not sure if different year models have any slight differences (bolt size, battery cover, etc), but here is the procedure for my 2006. BTW - I just bought two new BXT 65 850's (Motorcraft Maxx). The OEM is a BXT 65 750. I really like the upgrade to the 850's!
Wear old clothes, gloves, and probably even safety glasses. The sulfuric acid electrolyte may spill or spatter if the battery is cracked and it is good to be protected from it.
The batteries are hooked in parallel, but there still is a designation of primary and secondary. The "primary" battery is considered the passenger side due to the fact that it is directly connected to the alternator input and both starter and glow plug output. The "secondary" battery is considered the driver's side since its only connection with the rest of the system is delivered through the primary. The primary is subject to higher load stresses and voltage fluctuations than the first.
Terminal bolt nuts are 8mm (5/16” will work also). If you use a ratchet, you will need a deep socket. The battery hold down bolt is also an 8mm size (some vehicles MAY use a 10mm nut or bolt for the hold down)
Do not store tools on top of the battery while working. It is very easy to accidentally knock them against the posts setting off a spark shower.
Always remove the black, negative (ground) cable first. Then remove the red, positive cable.
If you are removing both batteries at the same time, always remove BOTH the black, negative (ground) cables first. Then remove the red, positive cables.
If you are removing both batteries at the same time AND have purchased a “battery backup” device, then follow manufacturers instructions and plug into the cigarette lighter port.
If you change one battery at a time, be sure to insulate the red, positive cable terminal end so it does not accidentally contact a ground and short out. You can use large rubber sleeves (or section of an old coolant hose split lengthwise) when changing batteries one at a time.
The driver’s side battery has a plastic cover over it to keep the PCM and cables dry and protected from battery corrosion. After disconnecting the battery, remove the battery cable support plug from the “tab” on the battery cover. The battery cover is held in with plastic “snaps” on each side. It is straight forward to unsnap it and lift it out.
If your battery has carrying straps, inspect them before depending on them to support the weight of the battery. I have known some folks who have some dents that resulted from the strap slipping out of the slot at the wrong time.
For the battery tray (if it is metal), wire brush areas that show corrosion or traces of rust. Then wash it with soap and water to neutralize any traces of acids left. Let it dry thoroughly then treat bare metal and rust with rubbing alcohol. Alcohol has good anti-rust properties. When it has dried paint the holder or carriage with a good primer paint with acid resistant properties. If the battery hold down bracket is metal, clean and treat it the same way as the carriage
Always clean (wire brush) the terminal posts and the terminal wire connectors before installing the new batteries. I also like to make sure that the top of the battery is clean (should be if the replacement batteries are new).
One good idea I have heard is to put a 1/4 inch rubber mat where the battery would rest on the carriage. This will help cushion the battery and protect the battery base from direct contact with the metal carriage.
Install the batteries, and install the hold down components.
If you are replacing the drivers side battery, replace the plastic cover.
Connect and tighten the teminals just enough so the battery does not move. Over tightening could crack the battery case.
Proper procedure for un-hooking dual batteries (both at the same time) is:
1) Disconnect the black, ground cable at Secondary Battery (LH).
2) Disconnect the black, ground cable at Primary Battery (RH).
3 Disconnect the red, positive cable at Primary Battery (RH) – then wrap insulation material around it.
4) Disconnect the red, positive cable at Secondary Battery (LH).
5) Remove old batteries and replace with new ones.
6) Reverse this procedure for hook up.
Proper procedure for un-hooking dual batteries (one at a time) is:
1) Disconnect the black, ground cable at Battery.
2) Disconnect the red, positive cable at Battery – then wrap insulation material around it.
4) Remove old battery and replace with new one/
5) Reverse this procedure for hook up.
Also (from what I have read):
If you ever have something happen that drains batteries like leaving lights on, keeping key on listening to radio for more than 4 hours, or having a failed alternator, you MUST charge them with a charger to get them back to full charge a nd restore their potential for full lifespan. The "I'm gonna drive to the store to charge up the battery" deal DOES NOT WORK!!! Alternators do not keep voltage high enough to bring back a weakened battery. Alternators can not have increased voltage level without also having increased amperage. High voltage and high amperage would dry out the electrolyte and cause failures for that reason. A battery charger on a lower level for 24 hours or more will do a great job of restoring battery as it has the higher voltage needed for restoration but with limited amperage.
Do this AND clean your terminals twice per year as a PM practice and you'll spend a lot less on batteries.
I just had to replace my batteries. I bought the Die Hard Platinum AGM batteries. Each is 930 CCA, full replacement for 4 years, prorated after that for another 5 years. They are Mil Spec but on the expensive side.
__________________ 2011 F250 6.7 PSD 4X4 3.55 ELD CC SB Moon Roof Chrome Package NAV Lariat
April 2011 Build, ARE TW Cap, Recon LED Cab Lights, Air Lift Loadlifter 5000,
WeatherTech - Mats, Bug Shield, Mud Flaps; Bed Rug, McGard Tailgate Lock,
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