Aerowhatt
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Re: Traction battery going bad or something else?

Wed Dec 06, 2017 8:11 am

RobbW wrote:Anyone know if replacing the main battery pack resets the warranty on the battery? Or do you only get the remaining life of the warranty?


As with most warranty replacements, or repairs you only get the remainder of your original warranty on the new traction battery.

Aerowhatt
2014 cool silver ES, acquired new 4/2015
2014 Labrador Black Pearl ES, acquired new 3/2016

Aerowhatt
Posts: 340
Joined: Wed Jan 28, 2015 1:52 pm
Location: Albuquerque NM

Re: Traction battery going bad or something else?

Wed Dec 06, 2017 9:14 am

kiev wrote: The i909 from icarsoft will do everything except programming also, and it is much less expensive--but i don't need another data-reader, i want all the functions so i can do cell smoothing on my own time...


Cell smoothing may also include charging to a higher voltage. But certainly it's main function is to enhance the balancing function. As you stated previously the balancer function has a very small power "bypass" making the amount of balancing per full charge pretty small. That's part of why I advocate frequent charges to 100% SOC (but that's another conversation).

You can increase the balancing function time per full charge without much in the way of equipment. What ends the charge while balancing is the highest cell(s) tripping whatever the high voltage limit on the BMS is. That's why a full charge to 100% on 8 amps of 120 volt AC will give you a longer more effective balance than a faster charge at higher power. The balancer bypass on the high cells is a larger percentage of the total amperage fed to the pack. So it takes longer to trip the end of charge and lower cells catch up more.

Taken a step further. With Canion you can see just what is going on with a charge cycle. So using it, you can use the power used by accessory drains to pull down the charge current to the main traction pack. Thereby significantly holding off the end of charge signal from the highest cells. The charger in the car can only produce a fixed amount of power based on what is supplied to it. By sending the right amount of this power to the DC converter to run lights and cabin fan etc. A single end of charge balancing cycle can be drastically extended by only providing to the traction pack for charging approximately what the balancers can bypass. This will provide a similar activity to whatever the voltage smoothing cycle is that the dealer can do with their programing equipment.

Aerowhatt
2014 cool silver ES, acquired new 4/2015
2014 Labrador Black Pearl ES, acquired new 3/2016

kiev
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Re: Traction battery going bad or something else?

Wed Dec 06, 2017 8:22 pm

The only way i can see for smoothing to be effective is to turn on all the balancers except for the lowest cell and try to bleed them down to the target value. This could be done at any SOC while the car is stationary and not charging.

If there were any charging currents greater than 0.1 Amps, then the cells would continue to be charged even with bleeders on.
kiev = kenny's innovative electric vehicle

adam
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Joined: Tue Apr 19, 2016 5:53 pm

Re: Traction battery going bad or something else?

Mon Dec 11, 2017 12:28 pm

RobbW wrote:Anyone know if replacing the main battery pack resets the warranty on the battery? Or do you only get the remaining life of the warranty?


I called today and the dealer don't know if the new battery pack is brand new or refurbished. He confirmed that the warranty period is not reset though.

phb10186
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Location: North London suburbs, UK

Re: Traction battery going bad or something else?

Mon Dec 11, 2017 1:51 pm

adam wrote:
RobbW wrote:Anyone know if replacing the main battery pack resets the warranty on the battery? Or do you only get the remaining life of the warranty?


I called today and the dealer don't know if the new battery pack is brand new or refurbished. He confirmed that the warranty period is not reset though.


This question has come up before, and essentially, no warranty would be reset by a replacement part/ product, it's effective from the purchase date of the vehicle (all warranty terms are somewhat different, but it's almost always from the date of purchase/ delivery).

RE: whether the packs use recycled cells or not, that's also been debated, but who knows. It would certainly make sense on cost and environmental grounds to not dump the entire pack for one or two bad cells... They are going to need a couple of packs at the ready for dispatch at all times to cover failures in-warranty, but who knows what processes are happening behind the scenes, RE cell reuse to the point packs are made for dispatch. Seeing as there is no common source of used cells for our cars, I would assume some that pass specific test marks are reused, and those that are not are destroyed, but there would be no way to know that. It's as probable that they are all new, as it is that some are re-used... i'd like to know the answer to that question though.

Does the ah/h quoted on the recently replaced new pack on the other post equate to 88 brand new cells... anyone?

Lastly, does anyone know if there have been any other pack replacements for items other than bad cells - i.e. circuitry - I've always thought that one of the balancing boards could fairly easily get a dry joint and pack up...
2012 I-MIEV Keiko Silver 11K
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Don
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Re: Traction battery going bad or something else?

Mon Dec 11, 2017 2:00 pm

It's only been a short time that we end users have had a way to measure capacity. I think most who have measured replacement packs are reporting 44 or 45 Ah - Who knows what the supposed 50 Ah packs actually measured when they were brand new?

I would *assume* that replacement packs are put together using used cells - Why would they even consider using brand new ones when more than half of the warranty is already expired and they only need the replacements to last another 4 years or so . . . . ???

One could even make the argument I think that a replacement made up of well tested cells with 10 or 15K miles on them might actually be less likely to fail than a brand new pack

Don
2012 iMiEV SE Premium, White
2012 iMiEV SE, White
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kiev
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Re: Traction battery going bad or something else?

Mon Dec 11, 2017 9:37 pm

i remember reading in the service manual that the old battery pack is flooded in a bath of salty water before being sent back--a safety measure for shipping. So i don't believe that any are remanufactured.

To get 50 A-Hrs from a new cell requires discharging to 2.75 volts after charging to 4.1. Mitsubishi doesn't let them discharge that low, so nobody will ever see a value that high.
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Aerowhatt
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Location: Albuquerque NM

Re: Traction battery going bad or something else?

Tue Dec 12, 2017 1:10 pm

kiev wrote:The only way i can see for smoothing to be effective is to turn on all the balancers except for the lowest cell and try to bleed them down to the target value. This could be done at any SOC while the car is stationary and not charging.

If there were any charging currents greater than 0.1 Amps, then the cells would continue to be charged even with bleeders on.


My "guess" is that the balancers "bleeders" are locally controlled by the module BMS board based on individual cell voltage values. I've never seen a BMS system that works any other way. It's significantly more complicated to centralize it more than that. In smaller applications, I've dealt with, dissected, studied, and learned to trick BMS circuits of many stripes over the last 12 -13 years. By reducing the charging amperage we could always get the "bleeders" to run 3 to 20 times longer before a BMS initiated charger disconnect.

Newer BMS systems can also include a minimum amperage charge rate to continue charging, which complicates the process of "voltage smoothing" by this lowest possible charge rate method.

Mitsu installed a very low amperage Balancing circuit in their battery BMS. Or perhaps better stated, Yuasa did. They also did not include the ability to set the car to stop charging at less than 100%. The implication is that that frequent 100% SOC charges are best for maintaining cell balance. My own experience with the cars battery packs, supports this assumption. The older a pack is, the faster it will drift out of balance. Individual cells age differently, so cell efficiencies diverge over time resulting in greater variations over time and cycles. The least efficient cells are less efficient on both discharge and charge cycles, further exacerbating any disparity.

If there is evidence that the Yuasa BMS works differently than others, I would love to see it! A floating target, or bleeder initializing voltage would be a huge improvement. I suspect that Tesla may have this built into their BMS.

Aerowhatt
2014 cool silver ES, acquired new 4/2015
2014 Labrador Black Pearl ES, acquired new 3/2016

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