Number of battery cells finally discovered....

michael · Oct 27, 2014

A posting by the service manage of a Ford dealer mentions that there are 88 cells in the FFE battery pack. There had been speculations about that from time to time, and as best I recall nobody knew the number. There it is!

Since a fully charged battery has about 360 V, this represents 4.1 V/cell

WattsUp · Oct 27, 2014

Intersting.

There are two actual packs in the FFE, below and behind the rear seat. Was it clear if he was talking about one physical pack, or the total cells in both combined?

jmueller065 · Oct 27, 2014

That post is here:
http://www.myfocuselectric.com/forum/viewtopic.php?f=8&t=2352#p15467

BOLT said:
The cells are 4V each, and there are 88 of them.

I think he means the total # of cells. No breakdown of how many in each.

jachady · Oct 27, 2014

And we only replaced the upper battery.

WattsUp · Oct 27, 2014

jachady said:
And we only replaced the upper battery.

Can you confirm that 88 is the total number of calls across both battery packs?

If so.. curious, are they evenly split? (44 in one and 44 in the other)

jachady · Oct 27, 2014

I just talked with Brian (our Service Manager) and he will check tomorrow. He believes it was 88 total, but doesn't remember if that was the one pack or both.

GladeStorm · Oct 28, 2014

Hmmm, not nitpicking but I would have bet on 86 cells. I have a transcript from the assistance hotline specifying a cell voltage of 4.07 V and confirming OBD data.

H_BATT_CHAR 90.16%
BAT_TO_EMPTY_ESTIM 20028 watts
BAT_PACK_VOLT 350.27 volts
HEV_BAT_MIN_V 4.07 volts
HEV_BAT_VAR_V 0.01 volts
NEG_BAT_PACK_V 187.03 volts
POS_BAT_PACK_V 162.50 volts
(http://www.myfocuselectric.com/forum/viewtopic.php?f=7&t=2178&start=10#p13746)

On the subject of distribution:
If we assume that the POS/NEG readings come from the upper and lower packs, that implies a distribution of 46/40 (or maybe around 47/41). This distribution also accounts for most of the pricing difference between the upper and lower packs (and the size difference as seen in the videos.

michael · Oct 28, 2014

That's not nitpicking...I (and I think others) are interested to know the exact number.

BOLT · Nov 24, 2014

Hi Guys. I am the service manager that you are referring to. While doing some diagnostics, we found redings for 88 battery cells. I would assume that means that there are 88 battery cells total. We were reading information from the BECM about state of charge on the battery cells. There was a 'rebalancing' procedure that was referred to that automatically begins when the vehicle is left charging for any length of time, past when it is 'fully' charged. The maximum difference allowed between cells is .020V after rebalancing. Since ours was .317V, we ended up replacing the battery packs-both of them. I was told that they are 4V cells, but I don't recall seeing the actual state-of-charge for any individual cell. I know that 12V battery cells are supposed to be 2.1V when fully charged (there are 6 of them), and that makes 12.6V the normal full charge level of a 12V battery. Therefore, in our beloved FFE's, a fully charged battery would come pretty close to 360V. In Gladestorms' recording, the packs were 90% charged, so it's difficult to make accurate assumptions. I believe 88 is the correct number.

GladeStorm · Nov 25, 2014

Just to clarify- my numbers were from a battery charged to "100%" on the MultiFunction Touchscreen display. H_BATT_CHAR is the PID which appears to correspond to the 0-23kWh capability and ranges roughly from 8%to 90%. BAT_CHA_DISPL (which seems to be the PID driving the MFT) was reading 100% at the time.

The only point that I was making was that if all the cells were within 10mV of 4.07V and the total pack voltage reading was about 350V, then, .... -It's entirely possible that there is a 'loss/unaccounted difference' between the cell measurement and the pack measurement so that 88 is the actual number.

BOLT · Dec 4, 2014

Gladestorm,

Sure, ok. But, just so you know, the MFT display might read 100% charged while the H_BATT_CHAR pid reads the actual level of the HV battery charge. It has been my experience, so far, that the vehicle will indicate 100% charged when the pid is reading somewhere over 90%. Also, when the batteries are '100%' charged, they may actually need rebalancing. This can be determined by the HEV_BAT_VAR_V pid. It should read less than .020V. The way to rebalance the cells is to leave the car plugged in to a 240V charge station for at least 24 hours. I leave mine plugged in anytime it is at home, so rebalancing is never an issue. The onboard charger will determine if/when/how much to charge the batteries; it's nothing like leaving your laptop plugged in and ruining the batteries. I hope this helps.

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