Planing CanView and BMS+ conversion with lithium

so low current would be a smart thing at low temp?

 

When using these A123 20ah pouch cells it may be unnecessary but you cannot be certain unless you have a full specifications sheet for these cells.

My RFE (RealForce Enterprises) Chinese Lifepo4 20 ah pouch cells for my Enginer kit have a spec sheet which shows a graph that at -20degC the cell will only discharge to 50% i.e.10ah. The BMS16D will shutdown charging if the battery temperature falls to a low temperature i.e. 0 degC.

http://www.enginer.us/f/index.php?action=dlattach;topic=1273.0;attach=12701

The RFE spec sheet also specifies the following operating temperatures:

Discharge: -20 to 60 degC

Charging: 0 to 45 degC

I am sure that the A123 20ah pouch cells are superior but how superior nobody really knows.

 

Inside temp is between 17 and 20°C now, in winter. My charging current is 2A only because I use a small power supply (500w). But I will use an 2500w Elcon charger too, because 8 hours charging can be to small.
I have canceled sometime charging process during day. I think 4 hours will be ok.
So yes, charging current control is very interesting.

We don't have full A123 20Ah datasheet.
Don't you think we can use some of the A123 2,3Ah cylindrical specif. ?

 

4 hours with a 2500?
the elcon 1500 would do that? 80% is about 3800 watt right? taking a 90% eff of the charger that would take 3 hours and 20 min
with the 2500 thats 2 hours and 10 min

 

Maybe. Depends on how similar they are. I do not know.

But I would setup your BMS to terminate charging if the cell temperature falls to 0 degC or below. I would reduce charging current between 10 and 0 degC.

 

the cylindric are a lot different
i dont think you can compare those

 

I will add more cells because I have also longer trip then 38-40km.
And I will test 72x2. So 9360Wh. Using 85% DOD = 8kWh. Elcon "2.5kW" send 9A, so average power send is a little over 2kW. Then 4 hours.

Why 72x2 cells ?

When you have 70 A123 20Ah voltage very rounded, with fully charged cells, is 235v +-10v. So 245v maximum with medium regen.
With 72 40Ah I think voltage will be 235+6.6v but +-5v not +-10v.
So maximum will be 246v. I will test and I suppose that engine won't go in compression mode like it does not actually with 70 20Ah A123.

Then 72x2 cells will be devided in 6 packs.

 

a so your doing the 72 cells like i will do ;-) ;-)

when do you think you are ready? with you mind blowing 144 cells of these powerfull A123's ;-)

 

Oooo i found 8 cells that got a bigger dent in them.
i did not get al the foil of yet until today.
see the pictures
i attached 1 of these cells to a charger and pressed with my finger on the dents when charging the voltage dropt from 3,5xx to 3,48x.....
still charging at the moment.

 

when you get the elcon2500 are you still planning on charging indoor?

 

Only when temp will be too cold. Cells will weight 80kg.
It will take more then a month to connect all new cells, make new boxes ...

 

you have 6 boxed so only 13 kilos ;-)

 

price for the A123 is dropping fast
EVTV Friday Show - February 10, 2012 - YouTube
less then 1 dollar per ah.

edit
also nice way of making cell housing...

 

sb50 and no problem at all........ so I did not have to get the sb175 that came in today...wow these are big and 2x the price ;-(

 

the charger arived
i hope to do a first bench charge after tomorrow

tomorrow i wil try to finisch the battery box to the point where i maybe able to do a bench charge 1 day later.

still have to make al the 73 wires for the 72 cell monitoring with the connected 72 bleeding boards ;-)

 

let's make that next week....to slow

 

cells compressed...bleeding and cellllog cabling temp. attached..
maybe this weekend I blow up my pack