while i have the HV battery out of my gen1

EV_Cor thanks for the information. The US bulbs are higher rated somewhat higher than the UK/European bulbs and the OP did not make it clear that he was using double filament bulbs just say tail lamp. Being a retired EE I do understand that as filament temperatures drop so does the resistance. Just trying to make sure the OP is not chasing his tail with with wrong figures.

John (Britprius)

 

Hi John, he confirmed that he used both filaments in an earlier post. That is why I added the power together.
Nevertheless, whether 2 or 3 Amps, during a 10 min discharge he is only taking max 1/2 Ah from the module. If the module drops below 7.2V in that time, it is bad because it has less than 8% of original capacity (6.5Ah). I still need to go through my old pack (159k miles) to see how low the capacity of those modules are.

 

I agree but rebuilding the battery without doing a full re balance of the models as you know will likely give this sort of result as it only takes one cell in a module to be out of balance for the voltage to fall away quickly on the whole module.
I am doing some test on an old gen2 battery to see if it is reasonable or possible to balance the complete battery as one unit giving capacity gains without being dissembled.

John (Britprius)

 

I find that at low enough current, there is no problem to continuously charge NiMH for some time after it is "full", which will re-balance the pack. In fact, that is what the Prius does when it first detects modules out of balance - running the engine continuously and charging to 100% for several hours until it considers the pack balanced again. Using a lightbulb that automatically lowers the charging current as voltage rises, I have charged at low current (0.1 or 0.2 Amp) for many hours in an attempt to balance a pack and get modules back in line. At such low power levels the pack barely warms up, which also means that it will not gas out the electrolyte, so there is no harm done to the NiMH.
I have not so much experience with NiMH, but for sealed lead-acid the rule of thumb was always no more than 3% of the capacity as long term equalization charge, so for our 6.5Ah modules that works out to 0.2A max as continuous charge for some time (no more than 2 days, since then you have put back 100% after they were full, so if they are not balanced with this 200% charge, then nothing will...

 

Answer 219 Mah. Try to pair them so that all the pair voltages are as close as possible.

John (Britprius)

 

All your modules are fine. Looks great to me.

 

As John already reported, on average each module received 8110/37 = 219mAh.
However, one thing does not add up: The taillight is supposed to draw 2.27A, so a 10 min test removes approx 2270/6 = 378mAh. You reported that the modules bounced back to about 7.5V after disconnecting the taillight load.
How can the modules end up at higher voltage than start, when they were charged with an average 219mAh and then you removed 378mAh? I would expect that the in-rest voltage would be lower after this test than before.
Either your charger did not correctly report the total charge put into the modules (did you maybe charge in two sessions and the charger only tells about the last session?) or the taillights did not remove the amount of charge that we calculated, either because they are lower current (Wattage) or were connected shorter than 10 mins?
Just guessing a few common possibilities, but the before and after voltage measurements do not add up with the expected charge/discharge level. Just something to check.
I agree with the conclusion that these modules should do fine in a Prius, even though you do not know the exact capacity at this moment, they appear relatively well balanced.

 

Hi Scotman,
Capacity can be checked using a discharge-charge cycle.
In essence, you discharge until the module is empty and then you charge it to full. During discharge as well as during charge you can measure the Ah (current and time). It seems that with your modules, you already get a pretty good voltage swing with less than 0.4Ah so it seems that there is not much capacity left in those modules, although you did not try to discharge until they drop (under load) to 6V which indicates that the smallest capacity cell is empty, then charge them again till full.

 

See if you can get a refund.

I'll put three of my best modules in the mail with a tracking number and we can work out the details.

Bob Wilson

 

Hi Scotman,
Please call me Cor.
You can discharge the entire pack in parallel to get a quick-and-easy guesstimate of the average capacity by dividing the total Ah by the nr of modules.
If you want to match specific modules then you can either measure time while discharging them at a fixed current (but please make sure that your meter is actually showing the current to verify the draw of the lightbulb you use) or you can rely on the charger to tell you how much current he put back into each module.
I understood that Bob is sending you the best of his modules anyway, so that should give you a good shot at building back a working pack.

 

Hi Scotman,
It looks like the charger you use knows, since you reported earlier that it charged the modules to 8.8V, which is just over the 1.45V per cell that I also see for a fully charged pack (and before it warms up and the voltage drops a little).
If you want to know the individula module capacity then indeed you need to either discharge or charge them individually.
If you do not want to spend too much time then you might discharge them (using your charger?) in parallel until they hit empty (no lower than 6.6 unloaded) and then charge them again individually, so your charger can tell you how much he puts in each. Or use a discharge lightbulb and measure time - your choice.