2007 battery and jumping issue

Hi there everyone. I know this stuff gets posted all the time, so sorry for the repetitiveness.
Long story short I have a 2007 Prius that needs to be jumpstarted every time it is driven, but there are no other warning signs that something is wrong. What should I do?

Read on for lots of details… I have a 2007 Prius that I have owned for 11 of those years. It has 169,000 miles. If you look at previous posts, you’ll see that I’ve had battery issues on and off for several years. The 12 V battery was most recently replaced in late 2019 I believe. Throughout the pandemic it has been driven on and off, after suggestions hear that it needed to be driven more often. For the majority of the time it needed frequent jumpstart it’s from a portable jump starter that I kept on hand. This spring I was able to purchase a new car, and handed down the old Prius gal to my sister who is now living with me. She drives the car daily, however The Prius now needs to be jumpstarted every time it is driven. This can go on for several weeks/months, and we have it needed to call roadside assistance on three occasions to have them use a higher power jump starter to get it going. I have now learned that perhaps these roadside assistance pals are not so smart, as the most recent visit they informed us that the alternator needed to be replaced. I now know that prices do not have alternators. However, I don’t know what else might be causing this ongoing issue. In the car drives well when it is on, gets high gas mileage, all interior lights and dash work fine. There are no warning or other bad signs up on the dash.

I am at a loss… Is it just another 12 V battery replacement that needs to happen? I will admit that I am not a car guru, so in replacing the 12 V battery twice now I may have made mistakes along the way, so from reading posts and I might need it to check out the tightness level at the different posts. Does everyone have any other suggestions that may help me? We are looking to spend as little money as possible on this stage, due to its age and our financial situation.

 

Is this another name for a trickle charger? i bought one yesterday, arriving tomorrow, and hoping it helps the issue.
Last night we tightened the loose-ish positive terminal on the 12v, and then jumped it VERY carefully from the back battery to a good working car. After 6 minutes connected, the prius turned on and the diagnostic screen when flicked to it showed 13.8v.
This morning, dead battery as we predicted. portable jump starter didn't work. jump started from back battery again.
repeated this all day (have to work, no option otherwise to get to and from).
Anything i need to know about a trickle charger in order to get it to work on the prius?

i'm hoping to jump it one last time tonight and take it to autozone to get them to do a "load test" on the battery? i'm assuming i just ask them for that?

 

Thanks all! I don’t want to be one of those post and disappear folks.
We bought a 3amp charger from oreillys. Took about 24 hours to fully charge. After that it’s been working well for 2 days. No need for any jumps so far.
Tomorrow we’ll have a chance to test the charge and make a plan to take the battery in if needed.