Just Another HV Battery Thread and Experiments

This is another example of how the words "rebuilt", "refurbished", etc are being misused when describing used batteries.

Unfortunately there is not a standard when using these words.

 

Thanks for the continuing updates and documentation, TMR-JWAP!

I wonder if that battery "A" from the "rebuilder" was sitting out in the rain in a junkyard for a few months before it was "refurbished".

At what discharge rate did you test the capacity of the individual modules? I see a couple more very weak modules were revealed which were paired with stronger modules.

Electrically, the charger harness connection is big enough for the current, but I agree, mechanically, it should be better matched to the others. What about that smaller screw next to it; would that be a suitable place to connect the harness?

 

Please after the grid charging, isn't there a need to equalise(paralleling them)the voltages across all the modules, or that isn't needed?

 

According to Hybrid Automotive, the grid charger rebalances the cells.

A Prolong Battery Charger is an HEV power grid charger that very slowly charges the pack above its actual physical maximum capacity (i.e. above 100%). It is like a trickle charger for the hybrid battery. The slow rate of charge is intentional, so the battery pack is not damaged while using the charger. When each individual cell reaches its maximum capacity, the extra energy delivered by the charger is converted by the cells into heat. Cells that are not yet full continue to charge, until all cells reach their peak physical capacity. This forcing of all cells to their maximum capacity slowly and carefully re-balances the entire battery pack.

From Prolong® Battery Systems FAQ - Hybrid Automotive

 

Did you connect the charger with the battery ECU connectors still in place, or you removed them? Just wondering if the ECU won't have problems.


Dxta

 

This is ridiculous. From a rebuilt pack? Y won't the pack ha e lots of issues? High resistance, blablabla.
Nice one though.

 

That's the point. The pack was very poorly rebuilt and had problems. @TMR-JWAP is documenting the battery condition and how it behaves when properly repaired.

 

Problem is, there isn't a set standard for HV battery rebuilt.

 

It has been well established now, that this so called "equalisation" serves no useful purpose and is therefore just a waste of time and energy. It is not needed. Some are confusing this equalisation process with balancing, but it couldn't be further from balancing.

Go back and re-read Prodigyplace's quote from the HA website, in post #86, this describes correctly what balancing (more correctly top balancing) is.

 

The reason I asked is this: Let's assumed there isn't a Prolong charger, and you'd want to grid charge the pack on the bench. Would you connect it just the way you've done near those contactor's or there'd be other ways you'd have done that, without the battery ECU in place?


Dxta

 

Contractors is easiest.

 

I

I do ubderst what balancing is. What I meant is equalising of the voltages of individual modules, and not the capacity, as you might think.

 

It is helpful to have voltage similar.
But if you do a full pack a few charge/discharge/charge sessions thus should be a moot point.

 

Someone who doesn't read out the block voltages might stop here and call it good enough. If they are lucky, they might get by for a while with periodic top-ups. But obviously this battery needs cycling to refresh the better modules, and to weed out the bad ones for replacement.

I think what we really want to equalise is the state of charge. Since we cannot measure SOC directly, we estimate it using voltage, current, and history. If we pump more Amp hours through all the cells in all the modules than they can possibly store (top balancing), then we know that they are all equalised at 100% SOC.

If we equalize the voltage of the modules without first top balancing, then the individual cells within the modules are not necessarily equalised.

 

"It's helpful to have voltage similar". That was what I meant.

 

Yes, the stud appears to be designed to withstand repeated removal and installation of the cables. In contrast, it looks to me like the threaded holes in the relay case are directly in the backside of the copper relay contacts. In which case, they might be easily stripped after a couple retorqueings. So it may be better not to touch those screws.