Changing batteries in two battery vehicle

Joined
Mar 21, 2004
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29,553
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Near the beach in Delaware
I have two new group 65 batteries ready to install in my pickup. With two batteries in parallel I could change one then the other or do both at once. If I do one then the other the vehicle does not loose 12v power so all settings are retained but a helper needs to hold the positive cable away from anything while I get the battery in place and clamped in. If I just pushed the positive cable aside and it popped loose and touched ground then things would not be good.

Or the safer way, disconnect both negative cables then change batteries and last step is to connect both negative battery cables. Vehicle looses power.

I think I should go with the safer plan and do not think it's a big deal for the pickup to loose power.
 
I'm with ya on the safer route. Sometimes it is a good thing to have everything reset. On your F250 do you have the same 6R-80 as I have on my 15 F150? I'm thinking yes. If so, trans will relearn your driving habits as well.
 
I have a memory saver like this,

6180wmi3iqS._AC_SL1001_.jpg


plug one end into the OBD2 port and the other into a jump box or spare battery. They you can remove the positive cables and put a plastic bag or rubber glove over the ends and continue on.
 
Yeah just wrap the positive cable in something that is non-conductive. Not rocket science here.
 
I have a memory saver like this,

6180wmi3iqS._AC_SL1001_.jpg


plug one end into the OBD2 port and the other into a jump box or spare battery. They you can remove the positive cables and put a plastic bag or rubber glove over the ends and continue on.
They also sell a much cheaper one, it plugs into the 12V socket attached to a 9V battery. $5.
 
You get what you pay for. The $5 one won't tell you if the 12V socket is energized with the key off nor with it tell you if the 9V battery is good.
You should know if it's energized or not with the key off just by using a regular charger. And you can always use a meter on a 9v battery and not use it if it's dead.
 
You should know if it's energized or not with the key off just by using a regular charger. And you can always use a meter on a 9v battery and not use it if it's dead.
How would you know. I used to use a 12V extension cord with a jump box and would have no idea. If you want to grab a meter, if it's even with you, that's your choice. I prefer the convenience and safety of knowing if both sides are live right then and their. I mean, a screw driver is $5 but a cordless driver is $50. If you prefer driving screws manually when a more efficient tool is available, that's up to you.
 
How would you know. I used to use a 12V extension cord with a jump box and would have no idea. If you want to grab a meter, if it's even with you, that's your choice. I prefer the convenience and safety of knowing if both sides are live right then and their. I mean, a screw driver is $5 but a cordless driver is $50. If you prefer driving screws manually when a more efficient tool is available, that's up to you.
Well if it's your car, you just plug in a charger for your phone into the cigarette lighter. If your phone is getting charged with the key off, then you know it's powered when the car is off. You don't need a meter with you. You just check the 9v battery before you attach it.
 
Well if it's your car, you just plug in a charger for your phone into the cigarette lighter. If your phone is getting charged with the key off, then you know it's powered when the car is off. You don't need a meter with you. You just check the 9v battery before you attach it.
OK, I've never done that. Always charge my phone at home.
 
OK, I've never done that. Always charge my phone at home.
Well if you use your phone for the GPS, the GPS function tends to kill the battery quickly unless you have it plugged into a charger. I use it all the time just to know my ETA even when I know how to go. Sometimes I ignore it, but it usually knows the fastest way there as it's good with the traffic data.
 
I don't understand the issue. You charge up the existing batteries still in it. You charge up the new batteries ready to be put in.

You swap one old battery with new. You swap the other, old battery with new. Done.

If you want to skip charging them ahead of time, you just swap one battery then the other, then charge them both.

Why are you disconnecting them from the vehicle to charge? It is not necessary.

The only thing you really want to avoid with two in parallel, is if the old one is very discharged, don't connect a new in parallel with it at a much different voltage, but if it's a much different voltage, very low with the old batteries, then you probably already lost any volatile memory data you were hoping to retain.

There is an exception. I don't use very high current chargers, mine are 10 (maybe 12 I forget) amps or lower, so the charging voltage is not all that high to potentially damage anything. Besides it's not especially kind to batteries to charge much higher than that, ends up outgassing more than it's beneficial unless you're in a terrible life-or-death, hurry.
 
When I replaced the battery on the blue Camry, I just clipped the leads of the 5$ HF trickler on the cable bolts and went about my task. The charger has a red LED that lets you know it is hooked up correctly. I may have wrapped the + cable in a rag, I forget.
 
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