Help with my battery

First, you are not doing anything wrong. It's just that you've been roped into playing a game of whack a mole.

There are a few things happening. Most of which you won't have control over.
Simply replacing a module and not doing anything else has a pretty random chance of success.

You definitely could have bad or corroded wires that are causing the problem.

Is this a job you would consider tackling yourself?

You could buy some low-cost tools to monitor what's going on in real time. OBDII reader and a monitoring app.

I'd be happy to talk to you about this via phone if you give me a call.

 

welcome!
rebalancing will help the pack last longer between failures, but nothing can prevent them altogether. listen to eric, he's the expert. if you plan on keeping the car a long time, maybe just buy a new battery.

 

Whats rebalancing?

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a process of discharging and recharging the cells/modules/battery, to get individual voltages close enough in tolerance so the battery can function properly. you can't just plug in pieces and expect it to work for very long.
there are some good threads here on the process.

 

I have looked and saw a few ... however it doesnt make sense ... can you link one you trust ?

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@ericbecky and possibly @TMR-JWAP (both PC members) maybe able to supply you, but in any case Eric would be more than happy to talk to you and advise.

 

Think of the above drawing as storage tanks and 1 mah = 1 gallon of fluid. The bottom of the tank is 4 volts and the top is 8 volts.
When your HV battery is new, all 28 modules are relatively equal at 6500 mah capacity. As the battery ages, the capacity characteristics of the individual modules change and capacities diverge. Right now, "why and how" isn't important. Just believe it. Years go by, thousands of temperature cycles and charge/discharge cycles occur and potentially hundreds of thousands of miles accrue. Now the capacities have diverged quite a bit from the original 6500, but some modules are still 6000, some are 4000, some are 2000 and some probably even less. Again, 'why and how' are not important. It's fact. Now, while you're driving down the road any discharge or charge that occurs to the battery will always try to drain or add the same amount of mah (gallons) to each module (tank). As you can see from the drawing, draining 500 mah (gallons) from each tank will cause huge changes in voltage (level) on the left tank and smaller changes on the right tank. The battery modules are monitored by the HV system to check for this large divergence. When a large voltage divergence is detected....ta da!!!! Red Triangle!!

If it tries to drain more mah (gallons) than the module (tank) is holding, the module voltage will drop rapidly. If it tries to add more mah than that tank's current capacity, it's converted to heat instead.

Now a quick discussion of individual modules and capacities. Imagine we take two large steel poles to our back yard, mount them vertically 5 feet apart and make one of those tesla coil things where you have an electrical arc jumping between the metal poles. We turn it on for one minute every Friday night to watch the pretty electrical display. We have a rain shower every Sunday. The poles get a bit more rusty every week. The arc is a bit weaker every week. Ten years down the road the rust is crazy thick and the arc won't even light off anymore (like a Prius HID headlight ). I grab a chipping hammer, wire brush and sand blaster and head to the backyard to remove the rust layer and refurb the metal poles. Now, a significantly more clean, bare metal surface is exposed and OMG, the arc is beautiful again. Similar to this, a crystal layer forms in the battery module over time/usage and covers 'the metal poles' reducing available active surface area of the battery. Deep cycling/pulse cycling the module reduces/breaks up SOME of this crystal formation to expose more surface area. More surface area = more capacity = bigger tank.

The goal of discharging/charging/etc is to get all the modules to not only be bigger tanks, but also near equal tanks, where an addition or subtraction doesn't cause a large UNEQUAL level change. The system would work equally well if ALL 28 modules were small tanks or if ALL 28 modules were big tanks. (although big tanks = less engine run time = better mpg)

This is why swapping ONE (or 2 or 3 or 4....) awesome module(s) into your battery can still cause problems. You added a BIG tank to a bunch of medium/small tanks. The UNEQUAL level change may still be big enough to trigger the 'triangle'

Obviously, there's more to it in the details, but this is about the most simple way I can think of to describe the way it works.

If you're a Sheldon and about to get all technical on me, please refrain. Don't be a Dave.
Now my brain hurts................hope this helps

 

Question ... when you swap an awesome cell into not such awesome cells ... how would one equally charge and discharge them to make them all "equal"?

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a long and entertaining thread, not for the faint hearted: 'gen 2 prius individual battery module replacement' @ryousideways

 

Cycle/testing the modules in your battery can be either time consuming or expensive. Buy a one channel charger @ $50 and do one at a time=weeks. Buy a good 4 channel charger @$180 still = ~2 weeks. Buy multiple 4 channel chargers = $$$ but = days.

If you are unable to cycle/test your modules, the least expensive option is to obtain modules that are as close of a match as possible to the estimated average capacity of the ones in the pack that will be reused. It would be important to remove ANY that are suspect of being weak. Using only voltage checks can be limiting, but it can be done. Measure them all about a day after the pack is removed from the car. If any are below 7.2, they absolutely need to be replaced. Replace any others that are >.1 volt below the average voltage of the remaining modules. Although this is not an exact science, it will give you a very good chance of success.

 

I have the "other" full hybrid battery i got for $200 in my garage and a month ago all cells were 7.5 ... im having issues i think when my daughter drives my prius she has said it hit purple while driving. Never happens when i drive. Wed im off im going to test the cells in my car and see if any are ""off"" in voltage from the others.

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the color purple is okay. if it fluctuates up and down rapidly, you have a battery issue. make sure you load test the cells.

 

I sent you a private message (conversation).

 

For others that are reading this and still struggling with balancing, I'd suggest the products over at hybrid automotive.
Prolong Battery Systems. Extending the life of your hybrid. – Hybrid Automotive

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TMR-JWAP, that was a sweet explanation of module charging.

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