while i have the HV battery out of my gen1

I am not familiar with that charger but I would call that module dead.

Bob Wilson

 

thanks bob! can you explain how on your "module notes list" of d/c capacity readings you came to the conclusion that your 2nd cycle was the actual Ahr? for ex. module #27 is 3.670 Ahr and your notes list shows D2 is 3670, module #28 is 3.907 Ahr and on your list it shows D2 is 3907, and so on for the other module? i seem to be missing some basics here. my apologies.

 

3.670 Ahr = 3,670 mAhr (milliamp hour)

Bob Wilson

 

Hmm, my reading of the question was more like "why D2?".

Here's my stab at it: It looks as if Bob only did two cycles: D1, C1, D2, C2. D1 wouldn't tell you what you want to know about the full module capacity, because it would be starting from an unknown charge state. You wouldn't estimate capacity from the charge values because batteries have inherent losses - you'll always put more in than the capacity you'll be able to draw out. Since he didn't run more cycles, D2 is the only number left to measure the capacity available to discharge from a just-fully-charged module.

If he had run more than two cycles, there would be more of a question of which Dn to use ... or an average of the Dns, or an average of the last 3 Dns, or whatever. But in this case D2 is the only choice.

-Chap

 

yes chap! thank you, that was exactly my question and i now understand the reasoning. although i do see a line on his cards where below it looks like he ran another 2 cycles? ...trying to get into the minds of you electrical engineers is no easy task. lol

 

sorry folks! i actually missed the whole paragraph where bob explains his process and how he is being conservative by using his first cycle Ahr numbers. i now understand. thank you guys!

 

No problem . . . I didn't understand your last question. Chapman got right but let me add a few details.

I've found that there is no improvement after the first discharge/charge cycle. The second cycle is usually the last one where the metrics have any reproducibility. But as the number of cycles increases, the dV/dt trigger appears to become weaker and Ahr capacity shows no significant improvement. Thereafter I'm seeing variability and possibly a slight decrease in capacity. But in these tests the MRC 989 is really stressing the battery.

In normal operation, the 40-80% range keeps the NiMH batteries in a 'sweet spot' for long life. But in these automated, capacity discharge/charge cycles, the MRC 989 is going pretty much to the limits. The limits eat into the battery charge-discharge life.

So when I suggested staying in the 8.0-8.1 V charge range for balancing and well above the 6V/cell discharge limit . . . well there is a method to my madness.

Bob Wilson

 

Ok. With the 4 modules I have put through 3 cycles I am seeing discharge amp hour capacity numbers such as 00010. I was hoping I was doing something wrong but I think they are just completely dead modules. I will try a cycle with a known good module to be sure. Thanks fellas!

 

I would recommend sort by voltage:

• pair weakest and strongest - this will even out the 19 pairs voltages as much as possible
• put the weakest pairs on the ends where it is coolest and strongest pairs in the middle

One last balance charge to 8.0-8.1 and then assemble the pack. Be careful:

• at least one footer screw per module, CHECK the terminal module polarity!!
• long buss bar first, careful torque the terminal nuts correctly
• last sanity check of sense wires
• as the remaining buss bar pairs are installed, lethal voltages, ~150V DC, become available
• one last chance to check terminal nut torques, carefully

Bob Wilson

 

That looks good. Based upon what we see, the lowest and highest pairs:

• 15.49 - 15.30 = 0.19 V . . . 0.30 V is the difference that leads to a code

Assemble working with deliberate but careful speed. We are hoping the remaining, weak modules are not on the verge of failure but there are no guarantees!

Without any basis in fact, I am hoping that driving the car will help equalize the voltages around the mean.

Do you have a Prius aware scanner that can read out the 19 module pairs? This will make it much easier to track the health and progress as well as identify any problems that happen early.

You may want to take the remaining pair and using your charger, measure their Ahr capacity. Be sure and put them between clamped boards. Use small charging currents, say 0.15-0.25 A as they are likely to be weak. Consider these your 'on hand' replacements if one or more of the other weak modules 'gives up the ghost.'

Bob Wilson

 

Not sure, can you make that a link?

Consider putting in the 19 reads. The reason is after you do a sanity check, drive for a week monitoring the high/low pair and voltages:

• BEST - the low/high indices change between 2-3 different values and; high-low voltages seems constant < 0.20 V
• GOOD - the low changes between 2-3 different values and; high-low voltages stay < 0.30 V
• OWCH - the low value and high index are stuck on single values and; low/high voltages close to 0.30 V or higher
• CODE - and one module pair is 1.2V low . . . <gerrrr>

What we're looking for is the optimum, 'balance charge' voltage. Record the 19 module pair voltages as much as possible both at start and end of trip. My data suggests 8 V/module, close to 304 V total is a good place to start. But as you've seen, there is self-discharge overnight. So taking some metrics gives us a clue if the balance charge should be a little lower or higher.

"ev_Cor" has done full-pack charge using a high voltage supply and might have some insights to share.

Bob Wilson

 

hello folks! (and of course bob wilson our mentor)

here are 3 cycles worth of mili-amp hour readings i took from my supermate dc6 on a 2005 module:

D1 2922
C1 4705

D2 4552
C2 4828

D3 4638
C3 7249

is it correct to say that the amp hour capacity for this module is 4.552 Ahr and that this would be a good working module? i know 6.500 is the ideal capacity for a perfect module.

 

Perhaps it is less important to worry about the two 'spare' modules and concentrate on getting the traction battery in and the car up and running. Work with 'deliberate speed' . . . not haste, not rush, but deliberate speed.

Bob Wilson