DIY Electric Car Forums banner

[EVDL] LiFePO4 one cell sagged/balancing, general/universal charging

615 Views 3 Replies 1 Participant Last post by  EVDL List
Hi Folk's,

On my www.evalbum.com/2749 E-Cat I noticed after two boating seasons (about 50 cycles last year and another 50 this year) that battery (buddy pair cell) number 15 out of 16 wasn't coming up to the 3.8V clamp voltage, stuck at 3.4V with the final 1 amp charge taper. I put a 8 amp individual charger across that one for an hour and that propped it up. I'm not sure why one cell would drift low when they're all clamped (with shunt balancers) to 3.8V on the final two hours of charge dv/dt=0 stop.

Also I've been using the same charger algorthm on floodees, STM5-180's Ni-Cads (40k miles - 1300 cycles), NiMH batteries and now LiFePO4 Thundersky 3.3V 200ah (actually 100ah buddy pairs). The algorithm recommended previously by Trojan's Jim Drizos for a GE charger patent 6,218,812 I did simply looks at each hour and compares one hour to the next and when the voltage is < than .01V per cell per hour rise (the voltage stops rising or may fall slightly on NiMH) the charger stops. It's served me well over the years, no fancy temp compensation and seams to work well for all battery types.

BTW, on www.evalbum.com/1273 last night my auxilary 12V motorcycle 12AA battery had dendrites across the plates (stuck at 11V) I tried charging with an 8amp charger but it got hot, 120F so replaced and noticed a ghost load of 11ma from the radio (which killed it while sitting in the garage over time - been driving my 70mpg Honda Insight to night windpower teaching classes at www.dslcc.edu). So I pulled the radio and the ghost load dropped to 1.6ma, pulled all the fuses, still there, probably back-feed into dc-dc conv. Do folk's put a switch on the aux battery to elliminate ghost loads while parked for awhile? Or leave the dc-dc converter on, probably reliability converter problems though? Maybe a 13.8V trickle charger plugged in all the time?

Have a renewable energy day,
Mark
www.reevadiy.org solar home tour tomorrow Oct 9th www.nationalsolartour.org my place EV rides
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.sjsu.edu/mailman/private/ev/attachments/20101008/610caaa3/attachment.html
_______________________________________________
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| OPTIONS: http://lists.sjsu.edu/mailman/listinfo/ev
See less See more
1 - 4 of 4 Posts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See less See more
Mark Hanson wrote:
> Do folk's put a switch on the aux battery to elliminate ghost loads while=
parked for awhile?

I have a smart 12v trickle charger that is powered up any time my car
is plugged in. When I get home, I plug in to charge the traction pack.
After charging I leave the cord connected so the 12v charger stays on.
When driving I have a dc-dc (power supply) augmenting my 12v house
battery.The dc-dc is not powered unless the car is running. I don't
know if the dc-dc has any parasitic affect, but the trickle charger
handles it.

Dave Cover

On Fri, Oct 8, 2010 at 8:43 AM, Mark Hanson <[email protected]> wrot=
e:
>
> Hi Folk's,
>
> On my www.evalbum.com/2749 E-Cat I noticed after two boating seasons (abo=
ut 50 cycles last year and another 50 this year) that battery (buddy pair c=
ell) number 15 out of 16 wasn't coming up to the 3.8V clamp voltage, stuck =
at 3.4V with the final 1 amp charge taper. I put a 8 amp individual char=
ger across that one for an hour and that propped it up. I'm not sure why=
one cell would drift low when they're all clamped (with shunt balancers) t=
o 3.8V on the final two hours of charge dv/dt=3D0 stop.
>
> Also I've been using the same charger algorthm on floodees, STM5-180's Ni=
-Cads (40k miles - 1300 cycles), NiMH batteries and now LiFePO4 Thundersky =
3.3V 200ah (actually 100ah buddy pairs). The algorithm recommended previ=
ously by Trojan's Jim Drizos for a GE charger patent 6,218,812 I did simply=
looks at each hour and compares one hour to the next and when the voltage =
is < than .01V per cell per hour rise (the voltage stops rising or may fall=
slightly on NiMH) the charger stops. It's served me well over the years=
, no fancy temp compensation and seams to work well for all battery types.
>
> BTW, on www.evalbum.com/1273 last night my auxilary 12V motorcycle 12AA b=
attery had dendrites across the plates (stuck at 11V) I tried charging with=
an 8amp charger but it got hot, 120F so replaced and noticed a ghost load =
of 11ma from the radio (which killed it while sitting in the garage over ti=
me - been driving my 70mpg Honda Insight to night windpower teaching classe=
s at www.dslcc.edu). So I pulled the radio and the ghost load dropped to=
1.6ma, pulled all the fuses, still there, probably back-feed into dc-dc co=
nv. Do folk's put a switch on the aux battery to elliminate ghost loads =
while parked for awhile? Or leave the dc-dc converter on, probably relia=
bility converter problems though? Maybe a 13.8V trickle charger plugged =
in all the time?
>
> Have a renewable energy day,
> Mark
> www.reevadiy.org solar home tour tomorrow Oct 9th www.nationalsolartour.o=
rg my place EV rides
> -------------- next part --------------
> An HTML attachment was scrubbed...
> URL: http://lists.sjsu.edu/mailman/private/ev/attachments/20101008/610caa=
a3/attachment.html
> _______________________________________________
> | REPLYING: address your message to [email protected] only.
> | Multiple-address or CCed messages may be rejected.
> | UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> | OTHER HELP: http://evdl.org/help/
> | OPTIONS: http://lists.sjsu.edu/mailman/listinfo/ev
>



-- =

http://www.evalbum.com/2149

_______________________________________________
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| OPTIONS: http://lists.sjsu.edu/mailman/listinfo/ev
Mark Hanson wrote:
> On my www.evalbum.com/2749 E-Cat I noticed after two boating seasons (about 50 cycles last year and another 50 this year) that battery (buddy pair cell) number 15 out of 16 wasn't coming up to the 3.8V clamp voltage, stuck at 3.4V with the final 1 amp charge taper. I put a 8 amp individual charger across that one for an hour and that propped it up. I'm not sure why one cell would drift low when they're all clamped (with shunt balancers) to 3.8V on the final two hours of charge dv/dt=0 stop.
>
What's the holding voltage (for the 1A taper) and how precise is it?
If it is 3.8V*16 = 60.8V, then let's see what happens is that voltage
goes 0.65% low to 60.4V

Cells 1-14 & 16 are at 3.8V => total of 57.0V
Cell 15 is still charging at 3.4V => added to 57.0V makes 60.4V => so no
current flows.

Or run the math on those clamp voltages, what is their precision? Maybe
they are all 1% high? 0.6V is enough to cause the above problem.

This is why my BMS has a separate full-charge signal, so you know every
single cell has reached full.

Thanks,
Cory

http://pacificev.com/products.html

_______________________________________________
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| OPTIONS: http://lists.sjsu.edu/mailman/listinfo/ev
1 - 4 of 4 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top