DonDakin
Posts: 387
Joined: Wed Aug 15, 2012 7:10 pm
Location: Montreal Quebec.....

Re: Future battery replacement

Tue Apr 01, 2014 2:36 pm

That is very interesting malm. Thank you for the video.

You may have hit 2.75 when demanding power and then rebounded back up to 3.25 with no current demand.

So that means that you can turtle around for 10.5 % of the battery. If driving very slowly that's about 15 km on a new imiev. Not bad for a reserve. I'm surprised that they let it go that low.

Maybe the turtle means "drive slow or you will soon have to push" more like a reminder then a lower power mode....


Thanks again for the video...

Don....

Malm
Posts: 449
Joined: Mon Jul 22, 2013 12:16 pm
Location: Tábua - Portugal

Re: Future battery replacement

Tue Apr 01, 2014 2:58 pm

No , I don't think so. How many times I went to turtle in one year, but only in march, 1, the day of his birthday, recalibration happened.
Riding an i-Miev since 4/2011 in Portugal, 100.000 kms.

DonDakin
Posts: 387
Joined: Wed Aug 15, 2012 7:10 pm
Location: Montreal Quebec.....

Re: Future battery replacement

Tue Apr 01, 2014 3:13 pm

Hey pv1

It would be nice if the bms recallibrated. I seem to recall that mitsubishi recommends to drain the battery to 2 bars or below and then fully charge every 2 months. This kind of implies that the bms can learn capacity by counting ah and looking at voltage. I wonder if it would freak out if it saw a growing battery.

I think malms battery charges to 100 % even thought it has lost capacity. But I'm not sure about that. If this did happen then the gauge would always read 100 % when full and you would not loose bars. But to tell the truth that would be a mixed blessing. You could always estimate capacity loss by looking at the RR but driving habit comes into play there.

I don't think anyone on this forum has "lost a bar" yet as the leafs do. But I think Dave's car lost lots of them when his battery was failing so I guess the capacity is hardcoded in the bms. It would require hacking to get the gauge to be true.

This sounds like an experiment for a crashed imiev that still has a decent battery. I just wish I has more time to play with something like this.....

Don......

Malm
Posts: 449
Joined: Mon Jul 22, 2013 12:16 pm
Location: Tábua - Portugal

Re: Future battery replacement

Tue Apr 01, 2014 3:14 pm

DonDakin wrote:That is very interesting malm. Thank you for the video.

You may have hit 2.75 when demanding power and then rebounded back up to 3.25 with no current demand.

So that means that you can turtle around for 10.5 % of the battery. If driving very slowly that's about 15 km on a new imiev. Not bad for a reserve. I'm surprised that they let it go that low.

Maybe the turtle means "drive slow or you will soon have to push" more like a reminder then a lower power mode....


Thanks again for the video...

Don....


Wrong. Never gone below 3,25 V. Allways looking by Canion. NEVER below 3,25 V. I'm sure, Stops because the 12,75 kWh are consumed and now that is 100% of SoC. It stops because it went to 0,0% of SoC. Remember, it is no more of 16 kWh, is of 12,75 kWh and he knows that (finally). But for me, it calculated its capacity wrong, maybe 14 kWh should be correct. Now i will have to wait one year for it to recalculate it again. Maybe with 12,75 kWh in two years it would get it right.

Wrong again. Turtle means stop. When an i-MiEV lost 8% of capacity, they will be lost on the turtle, and you will be able to do only 4 km with turtle, maximum. NONE of you will be able to drive 10 km with turtle if you have it for some time (1 year).

I think i will remove the video, because i don´t want to be responsable for anyone to stop away from home.
Riding an i-Miev since 4/2011 in Portugal, 100.000 kms.

Malm
Posts: 449
Joined: Mon Jul 22, 2013 12:16 pm
Location: Tábua - Portugal

Re: Future battery replacement

Tue Apr 01, 2014 3:24 pm

My i-MiEV in february stoped at 14,5% of SoC. Stopped with one bar on the gauge. So, its like I losed one or two bars. As simple as that. You don´t have to use your imagination, you just have to read what I say. If you drive nonstop from 100%, 16 bars, to turtle, you will find your degradation, as simple as that. Just read and believe me.
Riding an i-Miev since 4/2011 in Portugal, 100.000 kms.

PV1
Site Moderator
Posts: 3014
Joined: Fri Apr 27, 2012 4:22 pm
Location: Pittsburgh, PA

Re: Future battery replacement

Tue Apr 01, 2014 6:21 pm

Don, I think with a failing battery, one of the cells hits HVC (high voltage cutoff) before the rest of the pack gets near full. When that happens, the car stops charging at whatever SoC it was at. It'll try to bring it inline via balancing, but as the cell suffers more damage from its defect, it loses even more capacity, further reducing possible SoC. So bars get lost for a sudden decrease in capacity, but not a gradual loss, since no cell hits HVC before being close to full.

That's why I think starting with a new pack discharged and the i-MiEV's computer at a low SoC, you might be able to retrain the car for a bigger battery. My car hits 100% when charging and keeps going for a while. I've noticed now, 5 months later, it spends less time charging at 100%. So at the top, it appears to be voltage-based while balancing. This may be the key to a larger battery.
"Bear" - 2012 Diamond White Pearl ES with QC - 2/21/2013
"Koorz" - 2012 Cool Silver Metallic ES with QC - 1/5/2015
"Photon" - 2017 Bolt EV LT in Orange with QC - 7/31/2017

Solar-powered since 10/10/2013

DonDakin
Posts: 387
Joined: Wed Aug 15, 2012 7:10 pm
Location: Montreal Quebec.....

Re: Future battery replacement

Thu Apr 03, 2014 4:48 pm

Hey PV1,

Thanks for the info. I have played around with 18650 cells for an electric bike and Your right as the capacity goes down the voltage goes up quicker on charge. That's inline with your explanation.

I wonder if if would be possible to charge and put an unsensed load on the traction pack during charging. If you could bleed off some of the current then you could perhaps see if the charger would keep going until it top balanced all the cells. You would need to bleed the battery without the ah counter knowing. I guess if you could get access to the battery during charge it may be possible to try this. It's more of a bench test idea then something you could practically do on the car.

As an aside I was wondering if it would be possible to charge faster with the built in 3.3 KW charger if you injected power into the 12 volt system ? From looking at Canion it seems to me that all 12 V loads (computer/pump/EV gizmo #12) take away from the energy going into the battery. Sooooo if you were to make those loads lighter by say adding an isolated 12 V power source that's just above the dc-dc converter voltage during charge would you get a faster charge to the traction pack ? I'm thinking you might get another 400 Watts in there dropping charge time ~10%.

What do you think ?

Don....

PV1
Site Moderator
Posts: 3014
Joined: Fri Apr 27, 2012 4:22 pm
Location: Pittsburgh, PA

Re: Future battery replacement

Thu Apr 03, 2014 7:07 pm

Checking with OVMS, 12 volt system voltage while charging is 14.4 volts, so if you get about 14.6 volts into the system, that should take the load off of the DC-DC converter.

Putting an unmeasured load on the battery while charging would require removing the battery from the car and working inside the pack while having it hooked to the car. The battery current is measured inside the pack before heading back to the drive inverter.

Interesting idea, though.
"Bear" - 2012 Diamond White Pearl ES with QC - 2/21/2013
"Koorz" - 2012 Cool Silver Metallic ES with QC - 1/5/2015
"Photon" - 2017 Bolt EV LT in Orange with QC - 7/31/2017

Solar-powered since 10/10/2013

siai47
Posts: 363
Joined: Fri Jun 14, 2013 5:54 pm

Re: Future battery replacement

Fri Apr 04, 2014 6:50 am

The key to a lot of this stuff is how the BMS gets information about the status of the pack. As was pointed out in the last post, the BMS can only detect what is happening with the vehicle mounted pack. If you add an external pack and put it in parallel with the vehicle pack, the BMS still only sees the internal pack. The SOC reports only the internal pack condition as it is not seeing the external power being supplied to the vehicle during operation, nor is it seeing charging current going to the external pack during regeneration (or normal charging). What it is seeing is a I-MiEV that is hyper-mileing like crazy by using half the expected energy. This seems to affect the RR meter as it keeps increasing over time. However, the BMS also has hard coded into it the new capacity of the pack along with a time and mileage calculation for assumed degradation over time. I guess the point is, if you increase the capacity of the "battery" by added external power to it, the RR may be way off but the SOC tick marks on the dash still will give you a accurate representation of the remaining power in the vehicle.

As far as battery health is concerned, anyone who owns a I-MiEV needs to have the CANION app. It is hard to believe how long it takes to balance a pack that is even slightly out of balance. Without CANION you have no clue. Unless you charge to 100% on a normal basis for an extended period of time, you will not get the pack in balance. When I put a different pack in my I-MiEV, the replacement pack was out of balance on three cells. Watching the charging process shows that no balancing takes place until the charger tapers off it's output. This starts to occur around 98% SOC. However, when the first cell hits 4.11 volts, charge current is really dropped and balance process continues for a short period of time before the charging stops. It took almost a thousand miles of driving and many, many charges from a fairly high SOC to 100% to bring those three cells back in balance. Now that the pack is in balance, the RR is consistently higher then it was when I started. I know it is supposed to be "bad" for the battery to go to a high state of charge. However, the real fact is it is bad to store it at a high state of charge, therefore driving after completing the charge shouldn't cause a problem. I think it is much worse to have a pack that is out of balance. Once it gets back in balance, the internal balancers do a pretty good job as long as you go to 100% charge once in awhile.

kiwimiev
Posts: 4
Joined: Sun Feb 09, 2014 9:48 pm
Location: Auckland New Zealand

Re: Future battery replacement

Tue Sep 16, 2014 2:44 am

The CAM80 from EVTV looks like it may replace the LEV50 making a 25kW battery pack.
Has anyone tried to fit them?

http://store.evtv.me/proddetail.php?prod=CAM80FI

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