The technical term for "memory effect".

 

Oh…

I have seen nothing on that for NiMH battereies. I recall that it took awhile (nearly a decade) after NiCads came out big for the pernicious effects of their memory effect to be brought out.

One can only hope that Ford looked into that.

Recall that there was a real snit on these postings awhile ago on what 40% meant in terms of capacity. I was trying to make the point then that battery capacity, as a function of chemistry, degrades with time, but didn’t explain it very well and so took some shots…

I posted a graph a few posts ago. I believe it applies to typical & repetitive depth of discharge, not a one time, or once in awhile, depth of discharge.

 

That's it! It seems but I don't if a FEH once in awhile does a deeper than normal discharge??

 

I’m inferring from my experience with Pb-Acid batteries. If you infrequently, but repetitively, discharge the battery to a low limit, I believe that the graphed lower cycle life will apply.

 

If you repeatedly charge a Ni-MH cell/pack to the same level it can suffer from voltage depression. Ni-CD were very prone to this but Ni-MH are much better but it can still happen. A Ni-CD will take repeated discharge/charge cycles to recover but a Ni-MH needs just one cycle. These Hybrid packs don't charge fully or discharge fully, this application doesn't really appear in Ni-MH usage, so I really don't know if voltage depression even applies here! Just wondering if the FEH did something like a deeper discharge once in a while????

 

Yes, several people have noticed a single deep charge / discharge cycle periodically. I haven't noticed one on my 2008 yet, but I only have 17K.

 

Thanks!

There also no provision to deal with a unbalanced pack which can easily happen. Normally a 1/10C charge for 16 hrs. which would be .550A for your 5.5Ah pack to balance the cells.

 

I suspect that we’re going to have to wait for experience to answer that question. The specific kind of usage & cycling also has much to do with the memory effect. I have voiced a concern about the very narrow band çhosen by Ford for this NiMH battery for that very reason.

I have about 55k on my FEH, but I have not observed any deep cycling as part of Ford’s programming. Admittedly my wife does far more of the FEH driving than I do.

 

You can, by your own choice, do a deeper than usual discharge on the car whenever you want. ( IE put the key to run without starting the car, and drain the battery..... )

As far as for a super charge UP.... that is a little harder, but doable if you have mountains nearby... I've gotten my pack up to 80% SOC by regen in the Rockies. ( I suppose you could always tow your car and do regen while someone else tows you if that tickles your fancy.... )

HOWEVER... there is no documentation of this, but from my personal experience, and the experiences of others, the FEH by itself will do a super charge UP... on it's own, to the 80% to 90% SOC range once every 10,000 miles. Unless you watch closely with s SG, this process is normally invisible to the owner / driver. After the 90% super charge, the FEH will quickly discharge back to the nominal 53%. Many persons, incl. myself have witnessed 25 MPG at 65 MPH while the car gently super-charges... to be followed by 50 MPG at 65 MPH while the car dis-charges.

I've witnessed this 3 times at roughly 10,000 mile intervals. Since I have 87,000 miles on the car, I infer it has occured more, without my knowledge.
It's easy to spot on cruise control. Would be nearly imperceptible in stop & go conditions.

There is mention of this process in the owner's manual, but no mention of interval.

HTH,
-John

 

NOTE: The 3 times I've seen at 10k intervals, may have been by chance.

The FEH also montiors battery module delta voltage.
The FEH has 50 sticks of batteries with 5 cells in each.
Not positive, but I think each stick of five cells is a module.

My FEH has all modules within 0.06v of each other.
If the delta voltage exceeds value 0.xx this may be the trigger for a battery recalibraion / rebalance act.

I little off the topic for this thread though.....