Balance at the cell low voltage limit

Hello Everyone,
It has been another couple of weeks and the balance is still holding up. I still am not running the DB8s. The other day I got the red light at 45.5v as it should. The great thing is that this happened with the lowest cell at 2.8v because the balance at the bottom is working properly.

I still have U7 and U8 a little high becuase of the CellLog power issue before I fixed them. I am working to pull them down a little at a time.

Enjoy,
Dan

 

Hi Pb,
Yes, this sound normal. You will always have one cell go high first.

Do a discharge cycle and a charge cycle and then Email me that data in a pair of XLS files. I can tell more what is happening from that data.

What vintage is your system? Dec, Jan, Feb, Mar?

Did you balance at the bottom and capacity match your cells?

Are you plugged into balancers? If so Are they DB8s?

Thanks,
Dan Lander

 

Hi Pb,
Is cell 6 also going low when you get to full discharge? To be sure you are seeing full discharge you need to run the system till you get a red light or until you get your lowest cell down to 2.7v.

Knowing if cell 6 is going low is important for understanding capacity. If it is going low then this is a capacity issue. If cell 6 is not going low then you can drain about 1/2ah out of just cell 6 and see if that helps.

If you want to keep the benefit of Balance at the bottom. you do not want to plug in Balancers.

Thanks,
Dan Lander

 

Hi Pb,
When you take a little out of cell 6 you effect its whole range. You cannot take it out of cell 6 at the top with out it effecting cell 6 at the bottom.

If you have cell 6 going out at the top and cell 6 going out at the bottom you will not do any better with balancing. In this case cell 6 has low cappacity and balancing will not improve.

Thanks,
Dan

 

Hi Pb,
So we will always have some variation from cell to cell. The question is if you are getting good net performance from the entire pack.

My guess is that you are getting better than 95% of the available power out, compared to what you might get if you had also capacity paired your cells. To be honest that is really good considering to all the work involved to do capacity pairing.

Thanks,
Dan

 

Yes,
At this point it is very important to have the CellLog data.

Have you loaded the Software onto your computer? Remember to only plug in one USB to one CellLog at a time.

I will Email you some help on down loading.

Thanks,
Dan

 

Hello Everyone,
I have been running this system for quite some time now with no balancers. I have pulled a little more charge out of the cells that went high because of the CellLogs power draw. Now that I have fixed the CellLogs it is balanced very well. It is now never giving me any alarm. the converter is shutting down properly when the lowest cell is still above 2.8v. The charger is now ramping down properly with the highest cell hitting 3.6v.

In addition I have removed the balancers from my wifes car and started adding charge to the lowest cells and it is coming into balance very well.

Thanks,
Dan

 

Hi Pb,
My car is a 2005 with a January 4kwhr system. The converter was upgraded to a February converter which did give much better EV performance, but I have always run only one converter.

In late February I replaced 2 cells and balanced them at the bottom and capacity matched the buddy pairs.

All my mileage numbers are from the car computer. I have not kept the data to calculate mpg from a fill-up of the tank.

I get 30-35 miles on a charge.

Thanks,
Dan

 

I have never had a 5K converter. The Feb upgrade was to get the maximum out of the 3K converter. To be honest this 3K converter is almost as good as a 5K because the Prius can only accept about 14a before it starts throwing codes.

To get the new pair properly balanced at the bottom requires taking the whole pack apart and doing the process completely as described earlier in this thread.

To get close with a lot less work..
You can install CellLogs. Put the "power from all cells" mod into them. Attach them to loud alarms. And then balance manually.

To balance manually, Run the system to empty everyday and then do a full charge. Download the CellLogs. Then add some charge to the cells that were low at the bottom and remove a little charge from the cells that went high at the top. Do this a little at a time and after a couple of weeks of doing a little everyday, you will see that the system will come into balance.

Don't try shortcuts. You must follow the process completely for it to work.

Thanks,
Dan