Alright guys, so I have a theory

Alright guys, so I have a theory.

I want to replace one of these HV hybrid battery cells for a cell made from 18650 batteries (they're the AA looking battery cells found in lap top batteries, Tesla batteries; they're slightly bigger than AAs).

I want to put the cell I build from smaller 18650s directly into the Prius battery compartment so the Prius thinks it's just another cell.

A Toyota Prius has 28 cells. Each cell is 7.2 volts and 6.5ah. (So in total 28 x 7.2v x 6.5a = 1.3 kwh for the total battery)

One of those little 18650 batteries holds 3.7v and 5000mah.

So in order to get the 7.2 volts, I'd connect half in parallel and half in series inside a cell. So that 3.7 + 3.7 = 7.4 (the charge module can handle the rest and leave it at 7.2 volts).

So now I'm confused as to how many ah the final battery will be.

If I can fit 24 of those 18650 batteries into one cell, but I connect half in parallel, that means I can only add the ah of half of them up. so 12 x 5000 mah x 28 cells x 7.4 = 12.4kW hours

So did I really just upgrade my Prius battery from being 1.3kW/hours to 12.4kW/hours even though it's the same size?

One used cell goes for $50-80 depending on where you are, just buy one and avoid you car burning down.

Use the 18650's for the house.

Also, will that shit catch fire? Or do I need to implement some kind of cooling system for the individual cells? Or are those vent holes on the original Prius battery only for the toxic vapors it produces?

>The house
as in a Power wall to charge from solar panels?

I need to replace my entire HV battery, btw. I'm driving another car in the meantime. But before throwing down money on a new HV battery, I'd like to look into alternatives. I see a lot of YouTube videos of people playing around with 18650s.

Prius has NiMh batteries, it's different chemistry.

People do put li-ion packs in there but those are then connected directly to high voltage subsystem via inverter and then charged externally.

I've also heard you can put one more original pack into trunk for double capacity.

This is totally wrong place to ask such questions.

I repaired pack on high mileage Prius.

It's easy job, cells are cheaply obtainable on ebay.

Best thing would be getting some cheap charger/discharger like imax b6 and test each cell individually if you have time.

My pack had two dead cells. 2 years later it's still going strong.

>Prius has NiMH batteries.
Don't see why it would matter. NiMH is older technology. No harm in putting better Lithium Ion batteries in there that don't heat up as much and are more energy efficient.

>People do put li-ion packs in there but those are then connected directly to high voltage subsystem via inverter and then charged externally.

Are you sure you know what you're talking about? Because.... in a regular Prius from 2004-2009, the NiMH battery pack is also connected to an inverter. In fact, that's what allows for smooth acceleration.

Also, I would never plug my Prius in to charge it from the wall, it charges through the engine and braking system only.

>This is totally wrong place to ask such questions.
No, I think it's the perfect place to ask such questions. Where else would one ask that? /diy/? /o/?

> No harm in putting better Lithium Ion batteries in there that don't heat up as much and are more energy efficient.

LOL

if you find/make a good BMS, you should be golden

>Buy imx b6.
Will be doing that. Thanks.

I still haven't heard a good argument why I shouldn't try this Lithium Ion upgrade idea.

these 5000mah batteries are usually only 900-1200mah, google diy electric vehicle forums and post there if you actually do this project to help other people, thanks

Shit does not work like that. Can't charge liion with nimh charger.

As for plugging it in, what good would bigger battery be if you could only recharge through breaking, good only for driving down a mountain.

>18650 batteries holds 3.7v and 5000mah.
>5000mAh

yeah no, they're fake

even the top panasonic branded are like 3200-3400

What if my car catches fire and I explode?

Enjoy your unbalanced batteries

Ok... So even if it's just 2000mah

3.7volts x 12batteries x 2000mah x 28cells = 2.4kwh

That's still nearly twice as good as the original 1.3kwh battery.

im not saying to do it lol, i was trying convert a 260z datsun into electric but it got to complicated so i went back to my tendies

The Toyota Prius 2004-2009 has 28 cells, and inside each of those cells are 6 smaller cells. And they all seem to do okay next to each other without a module balancing them. There is only a module balancing the 28 cells, not the 6 sub-cells.

So as long as you have them fairly the same, it should be okay. If not, I can add some voltage regulators to each 18650 battery.

but the unit can't charge it correctly for starters as it's li-ion and then double the capacity would be a shitload of driving to keep topped up.

you can't just double your car battery size and expect it to be topped up everytime you drive to work

>smaller 18650s
What? 18650 refers to its size. A "smaller 18650" wouldn't be an 18650.

>will my car catch on fire
>battery says "ultra fire"

I never said smaller 18650s... I said they're similar to AA looking. The pic I posted basically shows their size.

The fuck is the matter with you?

>ultrafire
>5000mAh
haha, no they don't, they're complete shit
get some nice panasonic or samsung cells

There is no 5000mah 18650 in production, you bought Chinese scam batteries. The highest capacity cells available are Panasonic 3400mah and 3600mah, and they aren't cheap.

If you actually test those UltraFire batteries you'll find they discharge anywhere between 700 to 1100mah, they aren't even that consistent in capacity as there is virtually no QC for production.

You got scammed, hard, and you're likely going to kill yourself in a fire. Congrats on doing literally no research.

>I never said smaller 18650s.
Yeah you did, it's a direct quote from your post.

English is a tricky language, meaning is extremely sensitive to context.
When he wrote;
>I want to put the cell I build from smaller 18650s directly into the Prius battery compartment so the Prius thinks it's just another cell.
He's comparing the size of the 18650's with the Prius's original battery cell size, not other 18650's.

Re-reading the sentence, it's very confusing.
By "cells", he actually means batteries, yes?

yes, the two "cell" he wrote, he meant battery, this is given away as he says he's "building a cell from ... 18650's", you make a battery from cells, not cells from cells.

To really drive home how scummy the Chinese are
These UltraFire 18650s are lower capacity than some CR123As which are half the size.

Don't buy Chinese. They never sell you whats on the label. Theres always a corner cut somewhere, they always use cheaper materials, they always substitute some component for a cheaper one then pocket the difference. They can't be trusted. Literal insectoid merchant tier.

oh, that said, going off op's picture, i would imagine there's several of those bottom picture things in his car, judging from the size and shape
so that item as standard might itself be a cell, part of a set which makes up the whole battery
but his modification would turn a single unit into a battery, which he didn't consider

Prius's use those abominations because the ONLY reason base priuses have batteries is rapidly recapturing energy when braking, and using it when you start up again.
For example, the Prius C has a 0.9kW/h battery, and a 40kW motor. Meaning, you can go from fully charged to totally flat in one minute 21 seconds.
You try and discharge an 18650 in under two minutes, or charge it in the same time. Shit goes boom.

Now, that's the reason the Prius uses those massive heavy batteries that SEEM like they have shit capacity, it's coz they need batteries they can fucking thrash

You can actually discharge many 18650 in about two minutes, yup.

Not charge, though.

>One of those little 18650 batteries holds 3.7v and 5000mah.

No they don't. State of the art 18650's max out at like 4000mAh, normal ones are like 2000-3500mAh, and cheap garbage like UltraFire is like 1000mAh or less.