doing a monthly start on my brothers jeep.. battery is dead (i think)

[EstoMax]

so my brother got a 97 jeep wrangler for his first car and he gets his license in february.. so he cant start it yet.. the car has been sitting about a month and i wanted to start it up to drive it around a bit and it turns out the battery has died.. i tried charging it with my car for about 4-5 minutes and it didnt seem to have made any difference.. then i took the volt meter to the battery and put 50vdc scale and it said about 7 volts.. then i put it on my car battery and it said about 30 volts... arent cars on the 12volt system? and why wouldn't my brothers car charge when i hooked the cables up

max

[Merkur]

battery probably had way too low of charge, and when the cold came it froze.

[FiveFreshFish]

Almost all cars today have a nominal 12-volt system. It will take several hours to recharge a battery that's reading only 7 volts, not merely minutes. You must have read the meter in error to see 30 volts on your car.

[EstoMax]

well i have the thing set to 50 VDC and i looked at the numbers that go form 0 - 50 and it showed about 7 on his and 30 on mine.. ill go try it again.. several hours to recharge that thing? god damn.. i aint wasting that much gas to idle there and charge that.. is there a quicker way? can i push it down my driveway (its a pretty steep slope) and jump start it? but i only get 1 chance that way..hhe


max

[EstoMax]

so i looked again.. his is like 9 now and mines still around 30(around 28 i looked closely) is the voltmeter wrong or wth..

max

[FiveFreshFish]

Originally posted by EstoMax
i aint wasting that much gas to idle there and charge that.. is there a quicker way? can i push it down my driveway (its a pretty steep slope) and jump start it? but i only get 1 chance that way..hhe

max

Oops. I didn't see that you were trying to charge it with your car and thought you were using a battery charger. My "several hours" comment above would only apply to a typical battery charger with a charging rate of 6 to 10 amps.

If you try to push-start it down the driveway, you'd better be sure it will start or how will you get it back up the driveway.

[EstoMax]

i c.. so how long would it take to charge with a car?

max

[FiveFreshFish]

You should only use your car to boost it. What you tried (4 to 5 minutes) should be enough and with your car still connected, there should be sufficient juice to get the Jeep to turn over.

[EstoMax]

hmm...yeah...but it wasnt... in dash theres only brake light slightly iluminated that i can see... when key is turned

max

edit: i checked the voltage readings on a 3v battery.. and with 10vdc mode it was 3v.. and with 50vdc i lookd closely it was about there as well.. so im kinda sure the readnig is accurate

[FiveFreshFish]

You probably need to put a battery charger on it to see if it will hold a charge.

Maybe at its original 7 volts, it's considerably lower than normal and or may have an internal problem that would prevent it from charging up completely.

[EstoMax]

ok i guess ill do the 2nd gear start with it.. just tested it with my car down the driveway and it worked like a charm. haha

max

[EstoMax]

ok one more Q... i charged it a bit more with my moms car and she says theres something else wrong because the starter isnt even clikcing or making any noise.. for push start do i even need the battery/starter? i mean the car should start with push start no matter what right

max

[Zero102]

You do not need a good battery or starter to push start a car. If you have done it in your car, then I will spare you the explanation of how to do it.

If you have 30VDC on your car, as soon as the headlights go on, they would burn out, your engine computer would fry in seconds, all your light bulbs would burn out, and motors would burn up. Try using another meter on yours.

As for charging the battery with your car, after 4-5 mins it should start on it's own if the battery is not frozen. However, with yours still connected, it definately should have started. It is possible you had a bad ground when you connected yours, did you use the engine or the battery for a ground?

[illeagle]

Is it frozen?

[EstoMax]

i c... so 2 questions. what does it mean that the battery is frozen ??

cause it did get sub0 here for like 2 days last week

and the ground i think was good.. the first time i tried i grounded it on a kind of rusty but big bolt on the engine.. the 2nd time i found a clean one... and then i tried with my moms car too :|

max

[Zero102]

What it means when the battery is frozen, is exactly that =)

See, as a battery discharges, the electrolyte slowly converts to water, (normally it has something suspended in it, I just can't remember what right now), so as it discharges, it's freezing point raises. Normally, for a fully charged battery, it should freeze at -50 or so, but as it discharges, it can freeze at as low as -5. Keep in mind, that is in celsius.

Grounding on the rusty bolt will almost definately not work, but if you have a good clean ground, it should. Check your voltage with somebody else's meter, same on the jeep, sounds like your meter is being a little funny.

Have you tried push starting it yet?

[EstoMax]

i tried push starting with my car down the driveway and it worked fine
but my mom wont let me try it with my brothers since she thinks that it wont work and that car will stay stuck on the cul de sac.. ill try it with my friends one day.

max

[Weapon_R]

Take out your battery, install it on your brothers Jeep, and see if that works. If it does, go out and buy a new battery, and wait til he comes back before installing it. If it doesn't work, you have bigger problems on hand. It doesn't seem to be the battery, as you should see some accessory power when you put your booster cables on his batter.

[EstoMax]

ok so the down the driveway start didnt work.. i dont know why.. the car cranked a bit but maybe i wasnt going fast enough.. so my friend with his 90 accord came over and pulled out these huge ass rusty jumper cables and i plugged those in and it sparked at first and my car alarm went off.. so i was like wtf and unhooked it
but hten i put it back and all the lights and stuff suddenly turned on.. and then i started the car and it started right away.. hella wierd.. its like i have junk cables or some shit

max

[Zero102]

Probably have a thin layer of corrosion, either on the battery terminals, or on the cables. It has messed me up before.

Good to know you got it sorted out, sounds like the battery may be fine, but you should have it checked.

It's too bad push starting it didn't work =(