Jumper Cables alongside of the road?

[fredsparkle]

Since my pack is simple to reconfigure to a 12 volt configuration, I thought I would try a little experiment with a fully discharged pack at 11.1 volts.

I simply hooked it up to my truck battery with jumper cables.

With the truck turned off it showed a 10 Amp charge rate.
With the truck running it showed an 18 to 20 Amp charge rate.

Revving the truck showed a peak of 30 Amps.

This was with a 3S36P configuration and no BMS. Maybe a little prior planning would be to have a series of battery isolation diodes for voltage drop; that you bypass to control the charge rate.

I wonder how far you could go, holding up jumper cables and maybe a sign reading “Electric Bike Need a Jump!”

 

[cal3thousand]

Nice experiment!

Glad you didn't see any sparkles, fred.

 

[Punx0r]

Interesting idea

3 x 4.2v is only 12.6V, though. Are you not over-charging the cells by running the engine?

Slightly related, I have wondered if a 4S 5Ah nanotech pack would work to jump start a vehicle (and fit easily in the glovebox).

 

[ZOMGVTEK]

Slightly related, I have wondered if a 4S 5Ah nanotech pack would work to jump start a vehicle (and fit easily in the glovebox).

I would say that would work quite well, and likely crank the car faster than a well charged 6 cell PB.

http://www.youtube.com/watch?v=RsGo-MZ1HU0

Cheapo Turnigy 20C 3S does it fine.

 

[fredsparkle]

Nice experiment!

Glad you didn't see any sparkles, fred.

Full disclosure; I do have one group bad of the four bad now, durring a ride imediately there after (big hills near my house).

But I think it mostly occured imediately prior to this; as I had an extream fade after pulling 900+ watts for more then fiftheen minutes on a big hill.

Which could be definately related to using the orginal wiring for laptop batterys that comprise my pack (which is where I think the problem is).

These were recycled batterys which don't have a high charge C rate to begin with. You can see their history in the Homemade Battery Packs thread.

http://endless-sphere.com/forums/viewtopic.php?f=3&t=26383&start=405

Will investigate this sub pack failure more in the near future and report back. But it is still something to keep in mind as you build your packs and again why I suggest shorting isolation diodes to control charge rate via voltage drop.

 

[Punx0r]

I would say that would work quite well, and likely crank the car faster than a well charged 6 cell PB.

http://www.youtube.com/watch?v=RsGo-MZ1HU0

Cheapo Turnigy 20C 3S does it fine.

Well, that answers that question :lol:

 

[The fingers]

Just try standing out there with a sign that says "Will ride for jump". :lol:

 

[fredsparkle]

Nice experiment!

Glad you didn't see any sparkles, fred.

Full disclosure; I do have one group bad of the four bad now, durring a ride imediately there after (big hills near my house).

Will investigate this sub pack failure more in the near future and report back. But it is still something to keep in mind as you build your packs and again why I suggest shorting isolation diodes to control charge rate via voltage drop.

Ok I actually had a short that took out one of the parallel group of cells in the sub pack in question, which look to be total toast now.

The actual test configuration was for 3S 60P of 2200mah cells so 30amps of charge via the jumper cable would have been 0.22C; though since I am only getting partial capacity out of my batteries it might be 0.44C.

So to reiterate!

Emergency jumper cable charge might be an option if:

• 
  You can reconfigure your pack for parallel charge close to the 12 volt voltage level
  In this pack configuration it has enough C charge rating to not over stress the cells at potentionally high amperage level
  You have a voltage/watt meter to monitor rate and total inflow
  You are not looking to fully charge your pack, just return some capacity to make it further down the road