DIY 12v lithium battery for Prius - step by step with pictures

Good writeup. I am not sure about Gen 1 but the Gen 4 battery is now located under the hood. The same idea could work with a different box size if needed.

I am interested in comments from our battery expert @2k1Toaster .

 

Great post.
Thank you.

 

Why?

 

Indeed.
Except for the "hobby" value.

 

Too risky for me. So much easier, less time consuming just to put the correct battery in.
But, in America, you can spend your time and money on whatever you want too!

 

Curious to know if anyone has measured how hot temps get for 12v battery in engine compartment for Gen3 ?

 

jack, you are the man!

 

Another awesome creation from Jack!

Posted via the PriusChat mobile app.

 

I literally was googling a replacement battery for my 2011 Prius and this thread came up! I am very thankful for Jack's informative thread and for sharing his 12v Lithium battery DIY! Why? Take a look at the price of a 12v battery from your local auto parts store. I found stock replacement batteries by Interstate etc at a price of $200.00 starting! This Lithium DIY is not only going to cost less, the longevity and performance is far better than that of an AGM, Wet or Gel cell. I am going to build one of these for sure! Jack is right in that if you are not confident in what you are doing, don't try this!

Thanks Jack for sharing and look forward to all your great posts and sharing your knowledge!
Also, GREAT Dr. Prius APP! Love it and works great! Saved me a ton of $$$ without having to go to the auto mechanic!

 

Nice ! I've dabbled a bit making my own 12v from stainless steel shell D cell NIMH for my motorcycle. But I soldered and all the vibration broke one ot two joints fairly quickly. I've seen a bunch of youtubes of home made spot welders, even simpler than the one you use. All the instructions sound good except I missed the heat sink info, I'll reread again.

One question I was thinking about as I read was the low temp charge/discharge temp spec. I know I should follow the link and check it out myself, but I thought I'd ask here anyways in case you already know offhand.
edit found the specs

Charge Low Temperature Protection: -7℃

Charge High Temperature Protection: 55℃

Discharge Low Temperature Protection: 75℃

Module Size：62mm x 62mm x 8mm
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Thanks Jack really nice DIY post.

edit: Oh, the heat sink. I thought there was an extra one besides the one on the BMS.

Have you seen the method tesla uses to fuse the bus between cells? At least the one they were using last year... anyways. It's a thin spot in the bus plate for every cell in the pack that acts as a fuse if any single cell has internal issues.

 

To make Ohmmu folks lower their Toyota-battery price a bit
( seriously Ohmmu, keep that steep pricetags for the Tesla model; Prius version need to be more 'efficient', or it will *motivate* us to DIY lol )

Joking aside, I think the advantages of accomplishing this:
1. Significantly reduce weight << main benefit for us because less weight = more mpg.
2. More capacity (if we can fill the entire ammobox).
3. Stable power drop (for those who connect the battery to inverter, which most of do).
4. Serviceable cells (compared to non-serviceable AGM).

Thank you for sharing your experience Jack!

 

Make sure to pay attention to the warnings at the kWeld – Next level battery spot welder &#8211; keenlab site Jack linked above concerning Lithium Polymer Batteries. It's just above the specs of the spot welder.

 

OH POO!! A few pounds is nothing.
Plus, the "welds" seem weak, and if they come apart, and start bouncing back and forth,
the risk of an electrical fire goes up.
If you are really worried about weight, get rid of the spare tire, jack, and the plastic covering it.
Get rid of the glove box, radio, antenna, sun visors, back seat........

 

Some people miss the point completely but hey you can also talk, think or text less and it will be less wasteful.

Posted via the PriusChat mobile app.

 

OH double POO!

 

I have a feeling they might have their own agenda.
Like I said, as long as the price is right, people will choose to buy instead of DIY anyway (for convenience).

Just because of some low-effort replies, to make the thread more informative, here's an even more detailed VIDEO how to make this on your own. Cleaner, tighter, and neatly packed:

And here's the reward for your success:

 

So I removed the back seats & bench, spare tire panel + tonneau covers and everything, and I got poo poo'ed on saying it won't make a difference even though it being 74 lbs of lesser total weight. This new and cool drop in battery modification comes along and no one says nothing about this lighter battery that weights only a few lbs less won't even make a MPG increase dent.

 

Great all around tutorial. I did a similar project to that which I wired (4) Lifepo4 3.2v cells in series with a BMS controller (4S), connected to a MPPT controller, powered by the prius built in solar roof panel, to run a subwoofer amp.