Using a dead battery

[7ender 10+ year member]

First off, i'm definetely no expert when it comes to electrical.

I have a spare battery i'd like to run in my trunk, but it's resting at only 7.7 volts. It's a small Odyssey 18ah dry cell, and iv'e already got another (good) one in the trunk as well.

Can someone explain exactly how this would work? From my understanding, these trunk batteries kind of act like giant capacitors, soaking up any big draws from my system. So, if I add a dead battery into my mix, how would it's low voltage affect things? When i'm driving my car, wouldn't the battery be charged and act the same as the good battery?

But, when I turn the car off/let it sit, will the dead battery draw from the good ones and kill them?

Yeah, I could use some educating //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Thanks

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[audioatg 10+ year member]

Well first, Before you do anything. Charge that dead battery and see If its even going to hold a charge. Use a charger not your alt. Test that let it sit for a night and come back see what the voltage is. If it stays up you know your good if not new battery time. You dont want to put a dead battery in your vehicle with a good battery the dead one will sooner or later take out the good one. And you alt will strain to keep the dead batt alive.

 

[justin smith 10+ year member]

how long has it been sitting....put it on a charger bring it up to 12-13v then see how long it takes to drain on its own, if it stays there for a couple days i think it should be fine. but i dont really know?

 

[audioatg 10+ year member]

Another thing. Charge the dead batt. See if you have like a autozone or pepboys and take it to them and test the battery as well.

 

[bhsdriller 10+ year member]

^Yeah you should have someone test it to see if it's even good still before you do anything

 

[7ender 10+ year member]

Iv'e already tested it...it goes back to ~7.6 volts in about a day.

 

[7ender 10+ year member]

anyonez?

 

[alvitae 10+ year member]

I don't think it will work like you are planning. A freind was dropping to 9 volts, He went to the shop, Diagnosise? A bad battery.

 

[smoka 10+ year member]

Sometimes you can 'refurb' older batts by desulfating them. This usually only works to slightly improve the old batt and will generally not revive a 'dead' batt.

There are sites for homemade electric cars and many people refurb older batts to save money.

Here is some info:

 

[cj407]

yea a dead battery wont do anything for your system..it will only add strain on the alt if your system is draining both batteries below 11.8. at that point you are running your system and car off your alt. not a good thing.

 

[thegreatestpenn 5,000+ posts]

ditch the dead batt, it'll just kill your other batts.

besides 18Ah batts can be found on egay for $40 shipped all day everyday

 

[93dakota 10+ year member]

Sometimes you can 'refurb' older batts by desulfating them. This usually only works to slightly improve the old batt and will generally not revive a 'dead' batt.
There are sites for homemade electric cars and many people refurb older batts to save money.

Here is some info:

I have never heard of desulfating. Is this a legit thing to do?

 

[smoka 10+ year member]

I have never heard of desulfating. Is this a legit thing to do?

Never tried it, but in theory it should at least help an aging batt.

There is a whole worklog on this project but this is the only link I could find atm.

http://revived-battery-truck.blogspot.com/

 

[JimJ 5,000+ posts]

Surprised you don't have cells that have reversed polarity yet.

 

[7ender 10+ year member]

Guess I wont' be using it then!

Got a better idea...tomorrow I'm goin to try and install a second battery under the hood. It's a regular starting batt, and i'm going to put it where my intake resonator used to be...which has already been removed.