Remove battery while truck is running?

[Chris.S.]

Can I take the battery out of my truck (just for a few minutes) while my truck is running?

Just wondering if I could do that without messing anything up?

We used to do it a lot in high school but we did lots of things then that I've learned now that shouldn't have been done.

Only reason I'm thinking about it so that I could recharge my boat battery off my alternator.

I've thought about a dual battery set-up (with the second battery postion being temporary so I could have the battery in or not) but I'm just confident enough in my electrical knowledge to pull that off.

 

[flyingbrick]

I was always told not to do it on FI engines, but in a pinch you can with the old-old carb engines that only power a coil as long as you have no other load on like lights, or a radio.

 

[shadetree]

Most will tell you not to do it as there is a remote possibility an electrical spike will damage the electronics in the vehicle.

I have removed the cables several times on computer controlled automobiles with no problems. I think as long as the charging system is working properly, there is little danger.

If you remove the negative cable first, and put it on last, the battery absorbs much of the spike reducing the danger.

In your case, you could change the batteries, then jumper the good battery to start the truck. Use your own judgement.shady

 

[Chris.S.]

In your case, you could change the batteries, then jumper the good battery to start the truck. Use your own judgement.shady

Damn! That's such a simple solution, I wish I'd thought of that.

Thanks for the idea!


Duh.

 

[Will]

If you remove the negative cable first, and put it on last, the battery absorbs much of the spike reducing the danger.

That's like when I told this guy that the reason he was going through so many lightbulbs was that he was snapping the switch on too fast.

Don't unhook the battery. If everything in the vehicle is turned off and the battery is fully charged then the alternator is not working very hard and probably there won't be much of a spike in voltage. But if the battery is discharged and the alternator is pumping 40 amps into it and you suddenly unhook it, the milliseconds of time it takes for the alternator to reduce output means the output flashes through every system that is drawing any current at all and it means upwards of 100V may flash through the system. The battery is a load and it's draw on the alternator reduces the system voltage which triggers the alternator to increase output trying to catch it back up. It's exactly like playing tug-o-war and one team suddenly letting go of their end. If nobody is pulling very hard, no big deal most likely. What's your tolerance for risk though?

 

[Chris.S.]

That's like when I told this guy that the reason he was going through so many lightbulbs was that he was snapping the switch on too fast.

Don't unhook the battery. If everything in the vehicle is turned off and the battery is fully charged then the alternator is not working very hard and probably there won't be much of a spike in voltage. But if the battery is discharged and the alternator is pumping 40 amps into it and you suddenly unhook it, the milliseconds of time it takes for the alternator to reduce output means the output flashes through every system that is drawing any current at all and it means upwards of 100V may flash through the system. The battery is a load and it's draw on the alternator reduces the system voltage which triggers the alternator to increase output trying to catch it back up. It's exactly like playing tug-o-war and one team suddenly letting go of their end. If nobody is pulling very hard, no big deal most likely. What's your tolerance for risk though?

Makes perfect sense. When I need to do this (won't be often, I have 2 boat batteries to use up before I need anything re-charged. I'd need to be out a long time to drain batts-this'll just be when I'm out on longer trips, 3-5 days or more) I'll just throw the dead battery in the truck and boost off the good one.

 

[Psychopete]

Could he use a battery isolator and hook up the boat battery as a "back-up" to get the desired result?

Pete

 

[Chris.S.]

Could he use a battery isolator and hook up the boat battery as a "back-up" to get the desired result?

Pete

Somebody had suggested tha but Isolators are way expensive, someone else suggested using a solenoid to run a second battery. That's beyond my skill/knowledge level though so I'll just do the swap/boost.

 

[ranger1911]

would hooking the batteries up in parallel work?
(positive to positive, negative to negative)

save voltage, just more amperes, the alternator would charge both batteries while running. that and you don't have to unhook battery cables and lift batteries in and out of your truck.

i always hook up positive first, then negative.

have fun on your boat

 

[RangerFabWorks]

would hooking the batteries up in parallel work?
(positive to positive, negative to negative)

save voltage, just more amperes, the alternator would charge both batteries while running. that and you don't have to unhook battery cables and lift batteries in and out of your truck.

i always hook up positive first, then negative.

have fun on your boat

yes, you would put the batteries side by side, go positive of one to positive of the other, negative of one to the other. than take positive off one battery, then negative off other to give you 12 volts but have 2 batteries. just make sure you dont run them in series, as in, positive out, negative to posive of other battery, then negative of other battery out. this will give you 24 volts and fry everything. good luck to ya