Hybrid battery balancing

The discharge limit got me as well on the first charger I got- turns out that the specs are for a maximum number of WATTS that it can dissipate. So it can do 3 amps at a low voltage so long as it doesn't exceed 7 watts (typical for the cheaper chargers) . As voltage goes up then amps go down.

Posted via the PriusChat mobile app.

 

I hope DSC to 7.0v (you wrote) is a typo. I think that's too high a low cutoff value. In your work, did the battery health return? I'd suggest 6.0, which is what most of the others used. Some went below, but recall that you're pulling down 6 x 1.2v cells and stress occurs below about 1.0v per cell, I've read somewhere.

 

And don't forget, the charger setpoints use the voltage at the charger, not the voltage at the module terminals. During a 1.4ish amp discharge, my terminal voltages are about 0.2 volts higher than at the charger. My low is 5.8 volts (as sensed at the hobby charger) I use 16ga speaker wire, so your results may vary.

 

Whenever charging or discharging, this is very important. Know the voltagedrop in your cables.
When I bought a new 12V battery for the Prius, it tested fine but when I loaded down the battery with a single 12V bulb (some 4A draw) and it dropped to 6V, I was about to pick up the phone and start yelling at the seller.
Turned out the cheap crocodile-to-banana plug ready made cables I used had coaxial microhone cable instead of normal ~16AWG cable... Teaches me to buy the cheapest Chinese crap... (Works out to about 34AWG, they only had the inner wire connected, nog also the shielding-strands)

But I still haven't learned: Also check your charger's measurement accuracy!!! I just bought a new charger that displays a normal value but actually would charge my LiIons to 4.3xV instead of 4.20V. NiMH are more forgiving, but LiIons could burst into flames because of this.
Decent chargers will have less of an issue or even decent calibration procedures to adjust this. My Chinese knock-off doesn't.

 

Couple of questions:
Can someone please elaborate on what TMR-JWAP may mean in his CQ3 charger settings list in post #76 by
"Capacity Cut-off......7200 (I vary this anywhere from 5000 to 8200 depending on the modules)"
what does "depending on the modules" mean / how do you choose the appropriate capacity cutoff ?

When you are testing to identify faulty modules when they
aren't connected together any more, the "load test" is often mentioned (connecting a light globe)
how does one actually do this test to stress the battery enough to identify weakness without
damaging it/over stressing it ? Is timing/a certain period really a valid way to do it ?
Can the same be achieved via a charger - would the module be first charged or directly discharged
and what settings should be used and what should be logged ?

 

I suppose I can help!

Older modules typically have less capacity. Once the modules is at the limit of its 'charge', the remaining energy put into the module is merely converted to heat. Sometimes I will limit the initial charge portion of the cycle to 5000 instead of 8200 until I can get a rough determination of where the module starts that 'heat generation'. No need to charge to 8200 if it's already converting everything to heat at 4500. As the modules improve, I will raise the charge limit. On newer modules, they're typically able to absorb a lot more charge initially, so I'll start higher.

So for example, if I have a Gen 1 battery, I may start my cycles with a 5000 limit. This lets me get an idea of the actual module condition.
For a Gen 3 or 4, I would likely just start at max.

The delta peak auto cutoff most chargers use seems pretty glitchy and inconsistent on the chargers I've used, so I don't rely on it. A low setpoint on that and you're guaranteed to have a bunch of charges stop early

 

Can you please clarify - do you measure actual temperature of module or just consider age of module/start with lower limit and if it succeeds with lower value without too much heating, proceed with another cycle with higher limit ?

Maybe you have some good info on my other question about identifying the bad module ?

 

The quality of the test module cannot be distinguished by only measuring the no-load voltage. Even if the capacity of many modules is reduced to 1ah, its no-load voltage is still above 7.5v. So it is best to have an obd interface detection device to monitor the voltage of the battery in real time, and it is best to have a trip record for later viewing, the voltage of the battery during high current charging or discharging, and the highest value of the charging voltage at high SOC, and low SOC The lowest voltage during discharge, the battery ecu judges the battery status based on these, this method is closer to the computer detection standard, and can relatively accurately find out which group of modules is weak.

 

Thanks James! For my P0A80 situation (separate thread) it's clear to me that OC voltage doesn't tell me
much but unfortunately due to combined reasons of there being so much info to wade through to find out
what to do, delta SOC being around 40%/Dr prius battery test not being able to be performed and general
lack of knowledge , I've already taken the battery out and disconnected the modules and would now like to
be sure I am doing the least destructive testing to identify faulty module(s) and proper cycling to
bring modules to best state (besides all this, it's my daughter's car, so I don't want to stuff something
up ).

I was thinking of doing either the load test with light bulb - although from all the reading I'm nor clear on how
many amps I should really be stressing the module with and how to ensure I'm not doing more damage to
good modules by over discharging them. Alternatively as per my question(s) to TMR-JWAP above,
I thought I could identify the bad module and charge the good ones via charge/discharge but would like to
nail the whole process before starting. I've bought the CQ3 charger and have asked the shop about
the adapter which allows pc monitoring so that I can log each module - not sure whether anyone else
has this adapter/where it can be purchased.

I don't want to hijack this thread, but if my example helps others better to define how to identify
the faulty module(s), you can look at my other thread where I have some OBD info:
2013 Yaris hybrid 1.5l 178k km P0A80 fault | PriusChat

There module #10 seems to be the weak module but how do I now prove that and check
all the others in the best/most non-destructive way ?

 

Have you removed the battery now? If the battery is outside the car, you can try to use that charger to charge and discharge the test, charging can be 2-6a, 10a discharge (depending on the allowable discharge current value of your charger), choose the corresponding current according to your time, but if For high-current charging, it is best to use a temperature probe to monitor the battery temperature to ensure that the battery does not rise a lot of temperature, and then you can get the battery capacity data to determine the weaker module.
If the battery is still in the car, like the test described in my last post.
good luck

 

I've only worked on about 5000 modules specifically using the EVPeak "CQ3" chargers. I've posted all my CQ3 settings in a couple different threads to help give others a reasonable starting point with these chargers, but I probably have no idea what I'm talking about.....I can throw in one more thing though... ALWAYS perform a discharge first to determine how much energy remains stored in each module in the 'as removed from the car" condition. This information alone is usually enough to determine which modules need to be tossed in the recycle bucket.

 

TMR-JWAP, I am not sure whose comment you seem to
dislike - hope it wasn't mine because I've picked up a lot from your posts but you know what it's like, it's
one thing to describe something when you know all the details and another to understand it.
I'll take your advice about discharging first as I wasn't sure about that and will hopefully get a better
feel for the capacity cutoff when I start charging. I see in your settings that you don't specify
temperature as cutoff, but do you use temperature sensors on the charger and the adapter/software
to log CQ3 ?

 

Is there anything wrong with my logic of using slightly lower values to try not to stress
the modules ?

NiMH CHARGE CURRENT 1.6A,
NiMH DISCHARGE 1.3A 6.6V (my thinking is that 6.6V makes it safer for unbalanced cells to catchup
without going into reverse voltage)
NiMH sensitivity D. Peak 15mv/cell

Is the max. fully charged module voltage 9V ? I ask because as
I am writing one module is at 8.72V (not moving up - just slightly stepping
down and back to 8.72/8.73) and I don't want to blow it up or destroy it if it gets above 9.00V.

Is the charging current of 1.6A too low (from reading various sources, I saw C/2 to C/3
being good for peak detection) causing charger not to stop on time due to slightly
different behavior at the lower current ?

Just checked that module and it is still at 8.73V (can see drop to 8.62 for split second)
and charger is still charging- it's only at around 3600mAh now.

UPDATE:
I was a bit worried about the voltage during charging and thought it would be
good to not stress the modules in first cycle and wait for feedback before
proceeding, so I manually ended charging on all modules at 4400mAh:
Module 20 discharge 2688mAh, charge 4400mAh 8.66V
Module 18 discharge 2665mAh, charge 4400mAh 8.49V
Module 16 discharge 2038mAh, charge 4400mAh 8.70V
Module 14 discharge 1740mAh, charge 4400mAh 8.74V

 

In my opinion, outside the 40% to 80% state of charge (SoC) range, 1.6 A is too high. The recommended charge current above 80% is 0.05C or 325 mA. However, this low current does mean delta/V is unreliable. This should not matter as you will be doing this last part of the charge on a time basis.

It would not be ideal, but ambient and module temperature does affect the voltages you can achieve. I would be concerned and any module going over 8.7 V. Ideally you would want to control ambient temp to 20ºC and be using active cooling of the module. When the ambient temp is getting toward 40ºC and above the max voltage can get very high.

You can pretty much ignore the charge mAh, what you are interested in is the discharge mAh. Even though these are low (new is 6500 mAh) you can still make a usable battery, albeit a low capacity one. To make the battery viable you will need the capacity of all modules to be in the same ballpark. Maybe a few more cycles will improve them. Some of the more experienced people on here can comment on what mAh target would be reasonable to provide a better idea of what mAh target would not be wasting your time.

 

As I couldn't get the battery blower to work (maybe it's dead/will test with OBDII/mini vci
once battery is back in car), so I rigged up the best cooling I could (picture attached).

How are you estimating the SOC in my case - via the voltage ?
What am I doing wrong / how to proceed ?- the delta V is set to 15mV but charger is not cutting out - I
stopped the charging manually at 4400mAh

Voltage on modules which have gone through 1 discharge/charge cycle after sitting over night:
module 20: 8.1V
module 18: 8.1V
module 16: 8.11V
module 14: 8.11V
How can I tell whether the recharged modules are OK?

 

Fully understanding module based reconditioning is a long slow process. The more modules are tested the easier it is to start understanding what works and what doesn't work.

@dolj SOC reference of between 20% - 80% is for the whole pack and you have to do some math to figure out what voltage range that would be for 1 module. The 350mA charge rate Dolj mentions above is also referencing whole pack reconditioning and is a much higher voltage charge than module reconditioning so again crunching the volts / amps / watts equations is needed and not easy,
Whole pack reconditioning is typically easier and less time consuming, but still takes several days for complete 3 full charge/discharge cycles, less difficult to understand, but still confusing for a beginner.

The idea is to cycle several times and log the differences you see between the first cycle and the next cycle using the same charger settings in all cycles. Than repeat the process and look for changes between the second and third cycle.
Than if you suspect a weak module you can try cycling that / those modules for a 4th of 5th cycle and see if the extra cycling will benefit the module. If you change charger settings from on cycle to the next the logged results are less accurately definable.

Good start, now before changing the charger settings so another cycle and compare the what you find from the second cycle to those you already posted.

There should be differences in the results from the second cycle which will help you grasp how the charge / discharge cycling is supposed to work.

I would pay more attention to TMR-JWAP and rjparkers descriptions than others (including mine) for best practices for module reconditioning, in my opinion !

 

Thanks for the reply.
Yes, I was especially trying to follow TMR-JWAP because I trust in his settings/methods/experience
from what I've been reading (his settings are not on the high side) but my gut was still telling me
to go carefully as I'm new to this and it is my daughter's car, so I lowered the charge/discharge
a little more than TMR-JWAP settings. I didn't discharge to 6.0V but rather 6.6V
as I thought the charge left over between 1.1 and 1.0 would not matter so much
and would give less chance of voltage reversal on any cells which were not balanced.

I would really appreciate if someone could tell me whether the "high" charging voltages
I was seeing (8.49V - 8.74V) are normal i.e. whether I should continue the cycles with
settings I have maybe adding specific automatic capacity cutoff levels
for each cycle (during cycle 1 I was worried that the modules would be overcharged)
or whether I should change my settings ?.

Here are the differences between my and TMR-JWAP settings
TMR-JWAP (MY SETTINGS)
On the PROGRAM SELECT---USER SET menu:
Precharge Time ----OFF
Wait Time---CHG>DCHG----20min
NiMH sensitivity D. Peak 20mv/cell 15mv/cell
NiCD sensitivity D. Peak Default
Temp Cutoff......OFF
Safety Timer......OFF
Capacity Cut-off......7200 (I vary this anywhere from 5000 to 8200 depending on the modules)
(6000 but I cutoff manually at 4400 for cycle 1 due to "high voltages")
Input Power low Cutoff.....11.0v
Key Beep....ON
Buzzer.....ON
Back Light.....50%
Battery end volt LiPo...4.2v/c

Then PROGRAM SELECT----NiMH Battery
NiMH CHARGE Man
CURRENT 2.0A 1.6A (charger showed 1.5A)
NiMH CHARGE Aut
CURRENT 2.0A 1.6A (charger showed 1.5A)
NiMH DISCHARGE 1.5A 5.8V 1.3A 6.6V
NiMH CYCLE D->C
C=2.0A D=1.5A 1 C=1.6A D=1.3A 1

 

40% - 80% is the same per module or the whole pack. Of course, the voltage of a module is ~1/28 of the pack voltage.

The modules are wired in serial to make a pack so the current over a module is the same as over the pack. Again the voltage of a module would be 1/28 of the pack voltage.

Yes, they seem normal for the 'high' voltage.

 

@vjekobalas I think you are grasping TMR-JWAP procedures very well for your current understanding of how to cycle modules. I'm no expert put I have some experience with pack level reconditioning.

It's hard to determine a weak modules health from one cycle. It starts to show up after the second and third cycles as long as you keep the same or similar charger settings.

Again, I don't know the specs for your 2013 Yaris pack, but I suspect it's got fewer modules and a lower voltage then the prius packs.
which is why I didn't bother trying to convert volts amps and watts for your particular pack to the module level.

Reminding everyone reading your questions about module reconditioning that you have a Yaris and possibly give the specs of your pack ie: number of modules in the pack and the packs nominal voltage will help others to respond better for your particular case. And not confuse you and me even more than we are already.

 

Ok the Yaris bit of info was missed by me, but doesn't materially change anything as the modules are all the same and working with them at the module level is the same regardles of whether it is Prius or Yaris.

This, of course, would be 'The modules are wired in serial to make a pack so the current over a module is the same as over the pack. Again the voltage of a module would be 1/20 of the pack voltage.'

This as well is the same answer whether Yaris or Prius, yes, they seem normal for the 'high' voltage.