Performance is WAY UP!

I haven't finished installing everything in the Gizmo yet. I still have a little wiring to do on the BMS warning system, I don't have an emeter type device yet, I don't have a latching relay to kill the AC to the charger if something goes wrong, and I don't have the charger installed yet since I'm still fiddling with the finish voltage trim pot. It is finishing at about 71V right now so it isn't going too high for the BMS modules on a balanced pack. [(7-25-2010) see comments below about this ending voltage.] I have 18 "cells" and the BMS modules have a HVT (High Voltage Trip) of 4.00V. When I get things finished, or nearly so, I'll go weigh it at the Airport. A friend of mine is an A&P mechanic. He has some scales he uses to calculate the weight & balance on airplanes. I will post the data along with my CG calculations for the 6V pack and the new pack. Suffice it to say, the Gizmo is much lighter than it was with the lead acid pack.

Each pack of 10 cells with connecting straps & bolts weighs 80lbs I have a total of 36 cells. With the mounting hardware I used I figure this pack weighs about 300lbs. The Interstate Batteries U2200UTL are 62lbs each so 8 of them were 496lbs and this is without the connecting cables. It looks like I was able to reduce the weight buy about 200lbs. This is lighter than with the original Trojan T-875 batteries. They are 63 lbs each so a total of 378lbs.

The 18 "cells" I went to raised the voltage I see to about 61V nominal. After a short run to drain off the top 1% of charge or so the pack sits about 61V. After a several mile run it sits at about 60V. I find that while cruising along at about 125A or so the voltage sags to about 56-57V. A 200A load (this is 1C since I'm using buddy pairs) lowers this to about 55V. This is with the batteries at 45-50°F. Maybe when things warm up they won't sag as much. Even with this, it is much better than with the lead acid batteries.

My top speed on level roads with no wind is about 42 mph. Just after I installed the pack it appeared to be about 45-48mph so maybe the batteries were still warm from being in my shop. With the higher voltage I'm seeing current readings a little lower than before. This is to be expected. When climbing my hill I now only slow to 33mph where before I slowed to 24mph on a fully charged pack. I attribute the climbing performance to a higher voltage and being 200lbs lighter.

After installing the pack I didn't get a chance to back off on the spring tension on my coil-over shocks. I definitely sat higher and it seemed that I could feel every pebble on the road. I think I only had a 1/4" travel before the rear shock was at its maximum extension. I have since reduced the tension a couple of notches but I still ride a little higher and it is still a little stiff. I'm going to reroute the wires going to the motor so that I have more travel before the motor bottoms out against the tub of the Gizmo and the lower the tension in the spring to see how that feels.

Acceleration is much better than before. I have to watch my speed-o-meter to make sure I don't get a speeding ticket now. I can easily out accelerate the other cars on the road now. I'm not drag racing them but just comparing to what the typical driver does when a light turns green. When accelerating with the lead acid pack I almost never saw 400A from the batteries. Now I can pull 400A on every acceleration if I want. I tried bumping up the maximum amperage to the armature to 500A and noticed significant increase in acceleration. I didn't leave it there, however, since I want to stay below 2C on these batteries. I need them to last several years longer than the lead acid batteries did to recoup my investment.

In short. I love having a Lithium Ion battery pack!