Sanyo 3000s and low temperature false peak
This sequence of graphs will show that low temperature is a problem when using peak detect to charge Sanyo 3000s.

Graph 1 shows fallback in pack volts halfway through the charge when the ambient temperature is 9`C.

Graph 2 shows that with an ambient temperature of 14`C pack fallback could still be a problem.

Graph 3 shows that if the pack is warmed to 40`C the charge voltage is progressively increasing
and fallback is not a problem even though the ambient temperature is still 10`C.


Increasing the fallback delta to overcome this problem is not recommended as the temperature of
the pack at the end of charge could be damaging to the cells.

Tests
All packs linear charged from flat at 5A, fallback set at 0.04

Graph 1
This is a pack of Sanyo 3000s charged when the ambient was 9`C
Note fallback of approximaely 0.10 volts in the middle of charge.
This is why it is difficult to peak charge Sanyo 3000s when ambient temperature is < 14`C
  Key

Orange line is the pack voltage

The lines at the bottom
of the graph are 4
temperature probes.

Under Volts is the
temperature at the end of charge

    Volts
Cell 1 = Probe 1   36`C
Cell 2 = Probe 2   38`C
Cell 3 = Probe 3   37`C
Cell 4 = Probe 4   37`C

Read 8.00 on the graph as 0`C
8.20 is 20`C
8.40 is 40`C

At the beginning
of charge the
temperature is
9`C

Temperature at
the end of charge
is 38`C

      

 

Graph 2
This is a pack of Sanyo 3000s charged when the ambient was at 18`C
Note there is a small fallback of about 0.02 at the beginning of charge.
     


We have overcome this
problem of low temperature
false peak by ignoring the
fallback until the pack
has a certain (programmable)
capacity.This is only applied
when you select discharge
before charge.

This charge profile has allowed
us to peak charge the pack
shown in graph 1 with a fallback
delta of only 0.04

 

Graph 3
Pack warmed to 40`C before charging
Note no fallback until the end of charge
     

Pro-Trak does have temperature
detect cut-off as well which
works fine.

We have also noticed that if a
Sanyo pack is left charged over
night then discharged, the voltage
of the pack increases slightly halfway
through the discharge?

Could this be caused by the
increase in temperature during
discharge?
Does this mean that the pack
works better when at a higher
temperature?