Bad 12V battery

I have a 2007 Prius. Came out from work the other day and the car wouldn't start, at first some of the dash lights came on, but wouldn't power up. A fellow co-worker who is a mechanic looked at the battery and said it was low on voltage (7v), we did a youtube search and found out how to safely jump start the car using the positive terminal in the fuse box under the hood and the strut support nearby as instructed. Car started up and was able to drive to the nearest auto parts store. I had them check the battery and they said it was now holding a good volt charge (12v) but the cranking amps were low, don't remember what the reading was. Replacement battery is about $200 which is more than I have the moment. The auto parts store was able to jump start the car using a portable jump start pack the same way we before and the car started just as it should. I purchased a portable jump start pack because it was all I could afford, have had it plugged in in charging. I am currently unable to jump the car using this method now. Is there something I am doing wrong (other than replacing the defective 12v battery)? Would it be more practical to try and jump start using the positive and negative cables in the rear of the car on the battery? Also I have read on here that a simple lawn mower battery has enough power to start the car, is this true? I need a simple solution to keep my car running long enough for me to get to work and make enough $$ to replace the battery.

 

Ok, try using the jump pack from the terminal under the hood or directly at the battery?

 

I didn't know if one would be better than the other was my only reason for asking. I will try it and see what happens.

 

Oh yes I found out what a pain in the *** it is to open the hatch with a dead battery. Finally figured it out, but you would have thought they could have made it easier with a release handle like there is in a car trunk.

 

Okay, tried disconnecting the neg side of the battery and using the jump pack but still nothing. I am begining to wonder if the jump pack isn't strong enough to do it for some reason. They were able to start it using a portable pack at the auto parts store. It doesn't do anything different with the pack hooked up to the car than when not.

 

Disconnected the positive side as well, still won't power on. Headlights and dome lights will come on when hooked up the the jump pack so I know its doing something but not enough. It has 120v 600 amp, and according to the lights it is charged.

 

Well yeah I guess i just don't know what from this point. I mean it started fine before when it was jumped off of the vehicle and the jump pack at the auto parts store, but with this one it won't. Will a cheap lawn mower battery do it although not the correct battery for this type of use? I am thinking that for some reason the jump pack just won't put out the needed power but I have no idea why....

 

No red to the positive and the black to a ground as we did before, nothing different than the jump pack. Tried connecting at the battery terminals and nothing there as well. Only thing on the dash that comes up is the open door light, the car symbol with a wrench, and the headlight symbol if I turn them on.