LiFe Battery Info

I spent a lot of time learning about Life batteries, packs, and chargers, and wanted to share it so that others can save some time.
I got four 20AH batteries from batteryspace.com due to potential sizing issues.
Typically like LIPO, you make a pack with 2 cells in series and should use a balancing tap to keep both cells at the same voltage after charging. This helps keep an equal charge and voltage on each cell allowing you to get a better charge and to get the most of the capacity of your cells.
I had two cells I had charged separately but had not balanced them ever (I just made the series adapter last night). The charge was taking a long time since it ran at 6.7 amps up to a point where the voltage difference was over .5 volts then it went into a balance/charge mode where it was charging at .5 amps and was working on balancing as well. I decided to stop the charge and just balance them first so that they could charge at the higher amp rate. It took 20 minutes to balance them (I think due to a first time balance), then I started charging them again.
I decided not to make a 'pack' since it would require a larger access hole in the ship but rather make a series adapter for the ship so that I can make changes to the packs if needed. One example is based on what I learned last night. I charged the two cells, after balancing, and there was growing voltage gap between the cells, leading me to believe that these cells may also discharge in a different curve as well. I have decided to mix and match all my cells around until I find the two cells with the closest charge and discharge curves. I will use the charger to evaluate all of this.
I will do more testing on that part and post it later, but for now I wanted to show the series adapter with balance tap, some of the charging pictures, and the cells. The balance tap is used by the charger and there are a few major types, one of which is the Hyperion standard which is why I just went ahead and got a Hyperion charger. I looked all over the net for a 2s balance tap (2 in series) until I found some documents at Hyperion that said to just buy the 7s balance taps so that you have any size pack covered. IF you need less then 7 cells just take out the extra black wires and move the red to the left, refer to pictures. You will need one per pack or in my case per charging adapter (I didn’t need the tap to be in the ship, its only used by the charger). The balance tap was easy to install, pair the red balance tap wire with the main red wire that connects to the pack, the first black wire to the main black wire that connects to the pack and the second black wire to the wire (second negative) that runs between the cells. The mfr specifically said to solder the second black wire it to the center of the battery bar connecting the batteries which does not always apply when using the prismatic yellow cells as I am not sure if there is a battery bar for them anyway. Then plug the balance tap into the balance boards 7s plug spot and start charging.
Wanting a charger that would support a 20AH charge rate (looking to the future)I got a very nice Hyperion charger with a computer interface. This usb connection allows me to start and stop charges from the computer but most importantly keeps a historical log of the charges. I can go back and look at the charges and see how much ah were dumped in or out at that time. During the charge I get a graph in real-time that lets me see how the charge is going and when charging a pack see what each cell is doing. WOW this is a toy for the hobbyist and the techie within me. When charging a Life pack it shows a line for each cell that shows its voltage. This is how I could see the growing voltage gap in the charge./p>
I made life receiver packs but didn’t try to match the cells (based on their charge/discharge curves) but will on the next batch. The cells were around 9 each so I may make up some more, who knows. Keep in mind there is a difference between balancing (equalizing the voltages between cells) and matching (grouping the cells by performance attributes).
I hope this helps out the guys looking to try out Life batteries.
Johnny
Below is my charging station (old computers can be useful..)

The series adapter below. I used a spacer to help prevent plugging an anderson into the middle of the 4 and shorting anything out. Notice the white plastic balance tap with 7 holes but only 3 wires coming out. 1 black for each cell and 1 red per pack. I used the blue wire for linking the packs to prevent problems while assembling the adapter.

This is a shot of the screen in balance mode. Notice the two lines in the graph and how far apart they are at the beginning of the graph. As the voltage gap gets smaller the distance between the lines gets smaller. Very cool.

This is the charging screen. The red all over the screen is for when the voltage gap is high. This was the first time to balance the packs and they had a big voltage gap. Notice the values in the yellow field. The graph is hard to read but you notice the light blue line developing a very large gap early on before it dropped the charge current from 6.7 amps to .3 while I believe it was also balancing.

 

Actually Dave R. in Florida pioneered their use but there were so many questions that were unanswered I thought I would put something together.

 

Dave might have been the first in MWC, but Ron Hunt started using LiFE batteries during the same exact timeframe in the IRC. Either way, LiFE cells are the way to go for the future.

 

Here is a little update.

It has taken a while to get them all charged and somewhat evaluated. One cool benefit of the software is being able to study the discharge curve of the cells. I found that at the 5amp discharge rate the cells did not drop below 6.0v until 17500 amp hours had been used. It was a fairly fast drop off from there.

I plan to discharge at the max 10 amps and see what it looks like then.

I am still getting a sizable cell voltage gap when charging and discharging and have roughly identified two cells with a higher ending voltage. I make new pairs and then charge/discharge again.