What's the cheapest way to replace/rebuild my hybrid battery?

So, the prolong site says to discharge to 4.8 volts per module? Are you sure that's what it says? I thought the prolong only measured the overall voltage of the HV battery, not individual module voltages?

 

They sure do. I have this one, for the 04-09 Prius and I've experimented with it, but now only use it to run the cooling fan on my test bench.

Prolong Deluxe Reconditioning Package - Hybrid Automotive

Many people buy it, few understand how it actually works.....let me help you become one of the few..

Inconsistent Hybrid battery readings | PriusChat

 

Yes... That's normal. If we had lab grade electronic gear and solid state variable resistors based on an optimum discharge algorithm that accurately and simultaneously displayed the discharge of each module on a graph so they could be compared, you'd be able to rebuild a battery pack that'd be good for 3 years in a few hours.

However, neither of us are going to invest in tens of thousands of dollars of equipment to do that with all 28 modules at the same time. But you'd be wise to buy your replacement modules from people who have that gear. My buddy Joe in Bend, Oregon has that gear... And he's spent big 3 times in the past dozen plus years to upgrade to the lastest build of the engineers who design this gear. He also teaches hybrid & EV technology at his local college and enjoys a good phone conversation with intelligent competent DIYers: https://2ndlifebattery.com/product-category/toyota/

As for the rest of us, we get the cruel tedious process of doing it with lightbulbs, which are faster than than the 5w to 10w discharge resistors in hobby chargers like iMAX B6 V2 Charger , which are my preferred units for a charging bank.

Problem is the amp load in a filament in a light bulb changes based on heat and remaining charge level. That amp load change with bulbs was explained to me before and sounds awful, but I'd love it if someone would explain it again because I don't know it well enough to explain it to you.

 

I'm no expert, but here goes.

An incandescent bulb is a resistive load. Increase the voltage and you increase the current- and total power. Thing is, as you increase the power, things heat up- causing resistance to increase.

Usually that isn't a (huge) concern, except that light bulb filaments are designed to get REALLY hot- several thousand degrees. So the resistance increases by 10 to 15 times what it was at room temperature.

The thing is, that increase in resistance isn't linear. It goes up very quickly until the bulb starts to glow (ie, reaches its design voltage). Then it increases more slowly as the bulb gets brighter.

So you if you put voltage vs amperage on a graph you'd have a "parabolic" curve. Something kinda like this.

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So does that mean that when the module gets down to the the 1v to 3v range and bulb barely glows that the resistance is way lower than when bulb is lit up normally?

If so that would explain why a pack I fell asleep on when discharging years ago wasn't damage because when the voltage is at zero the resistance / load on the module from the light bulb was very low? I remember soon as I woke up and unplugged all the bulbs the voltage shot up real quickly and the chargers boosted it further.