Sparrow / NmG
My Sparrow Enerdel Lithium experience started in August 2013 and, as I write this in early January 2014, is still a work in progress.
In July 2013 I bought four EnerDel MP310-049 Power Modules. They are 43.8v (nominal) 31Ah packs (~1360Wh) with built-in cell voltage and temperature monitoring harness. They are Nickel Manganese Cobalt cathode chemistry. EnerDels were evidently recently successfully used in the now-defunct Think! and they were recently in the Pikes Peak Hill Climb record-setting Lightning motorcycle.
My needs are simple: five miles into town, five miles running around town, and five miles home. For anything further we have the Mitsubishi i-MiEV. I figured 20%-80%SOC would give me 0.6 x 1360Wh x 4 = 3264Wh and at a guestimated consumption of 6miles/kWh I should be good for about 20 miles.
I happily ripped the Optimas out of my blue Sparrow (which I had partially murdered a few months ago) and initially installed three EnerDels in the front (along with the Zivan) and one under the seat, the Big Red Button isolating the three in front from the one under the seat. Hey, wiring up four cells is a helluva lot faster than 13!
FRONT (UNDER HOOD) INSTALLATION
In front, one Enerdel upright (terminals up) on the lower shelf between the (what used to be) two metal upper Optima battery supports with blocks of wood wedging the EnerDel into place and a strap over the top tying it down by those metal supports. Forward of that I placed two EnerDels on center with a couple of 1/4" threaded rods on each side going back to those metal supports and a wooden plate between the two forward EnerDels and the aft one and a bar across the front clamping the whole works together. This still left room for the Zivan on its side in front of the EnerDels. Please ignore some of the ancillary wiring, left over from my Optima monitoring.
INITIAL UNDER-SEAT INSTALLATION
Under the seat I was able to cram one EnerDel on its side way forward on the port side, held in place with a block of wood screwed down using the port aft battery clamping threaded hole.
Not wishing to cut off the existing Sparrow wiring battery clamps I simply used some stud-terminal-with-threaded-stud adapters for the flat-terminal wires I added. Covered everything with shrink-wrap and bicycle tube and then self-amalgamating tape wrap, and made sure all the wires are secured using ty-wraps..
Some very nice detailed literature came with the EnerDels. Of especial usefulness are the SOC/DoD vs. voltage tables for both charging and discharging, allowing me to approximate SOC from the Sparrow's voltmeter and stay well out of trouble.
I first balanced all four EnerDels on the bench at around their 80% SOC point, ensuring they were all identical. What amazed me is that all individual cell voltages were (and are) within just a few millivolts of each other.
After installation, I charged the four packs to a total of 188v (just about 80%SOC) using the Zivan and hovering over everything like a mother hen, constantly checking pack and individual cell voltages - amazing, they tracked wonderfully.
Now, about the existing car and its controller: it has a factory-modified Curtis 1231C controller, supposed to handle the Sparrow's higher voltage. With this particular Curtis and regular Optimas, this Sparrow was a slingshot because there doesn't seem to be any ramp-up delay programmed into this Curtis. Both my wife and I had each snapped drive belts in this Sparrow with Optimas, and driving this Sparrow was always an exercise in featherfooting, but the power was instantly there when needed.
OK, so what happened when I first fired it up? Nothing! My Curtis controller evidently has overvoltage protection that kept the whole thing from working. Needless to say, I hadn't known that (there are no published specs on these modified Curtis controllers), but I suspected it so I bypassed one of the packs and tried it at around 140v and it worked fine. After re-balancing everything, I subsequently experimented and found out that the Curtis overvoltage protection kicks in at almost exactly 188v, so I limited my maximum charge to 187.5v.
What was the experience?
Before I tell you, think about weight (ignoring cables): the original Optimas were 13 x 43lbs = 559 lbs. The EnerDels are 4 x 33lbs = 132 lbs. Remember, this Sparrow was a slingshot WITH the Optimas.
OK, so what happened? All I can say is slingshot on steroids!
The good news is that the Sparrow is stable and corners very similarly to the Optima Sparrow (I live up a two-mile winding road), but the ride is rough and I still need to see if I can readjust the shocks/coils. I attribute the stability to the batteries and Zivan being way forward.
As Phil Salkie pointed out, it's amazing how little voltage sag there is when accelerating - on the order of only a couple of volts, but I really don't know as I'm too busy concentrating on driving when accelerating hard.
Well, I drove it for a few days, but accelerating hard from about 45mph would result in what I believe to be arcing in the motor across the brushes, which is a problem I've always had with this Sparrow - another reason for featherfooting it. Also, the Sparrow was barely manageable, as not only did it not have any power ramp-up, but any little bump would translate into a slight jerking of the right foot on the go-pedal, which would simply exacerbate the experience and I would often simply have to lift my foot off the go-pedal completely and then slowly apply power again.
Some correspondence with Ron Anderson led me to believe that a lower voltage would perhaps tame this beast, so I removed one of the EnerDel packs (the one under the seat), lowering the voltage to just under 145v. Sure enough, the controller worked far smoother and with less sensitivity to pedal position and I was able to nicely modulate the power application. And, she was still very fast!
As any astute hypermiler will tell you, range is simply a function of how you drive it. For myself and my usual 15-mile round trip the three-pack EnerDels worked just fine. For the few times I'd ventured outside this comfort zone I simply charged a little higher before leaving home (to 145v or around 90%SoC) and then slowed down and eased up further on the go-pedal and always managed to comfortably stay well above the 25%SoC voltage of 115vdc.
UNDER-SEAT INSTALLATION UPGRADE
Well, I was so pleased with the EnerDels that I ran out and bought two more and installed three EnerDels under the seat as a parallel string, but first VERY carefully balanced the three packs and then equalized the voltage of the two strings before connecting them.
For physically restraining the packs I first drilled a number of holes into the battery compartment floor and filled them with epoxy and then drilled again and installed and epoxied some 1/4x20 threaded inserts into place. Then I merely cut a bunch of wood blocks and held them in place with threaded eyes going through these blocks into the inserts. For now, I used some rope to hold things down until I decide if I like this mechanical configuration - I intend to eventually use some serious webbing straps to hold everything together - and that applies to the packs and the Zivan under the hood as well.
Now, there were/are four areas of concern:
1) The two strings are hard-wired together, but as an attempt to prevent catastrophic damage in case one of the strings shorts out I have put a 200A fuse in series with each string.
2) The Big Red Button no longer breaks the middle of a series battery string; instead, it is a manual voltage disconnect of the entire paralleled pack. I need to find the BRB specifications, as I'm concerned that this switch may be overstressed if trying to disconnect 145v with significant current flowing.
3) Vehicle Stability - whereas having three packs under the forward hood seems to retain its original handling characteristics, adding the three packs under the seat seems to have produced some skittishness. I plan on experimenting with both the suspension and tire pressures, but in the meantime am driving very conservatively at highway speeds.
4) Thermal. So far, I have done absolutely nothing about thermal management other than spot-checking casing temperatures with an infrared thermometer (admittedly, a poor way to do it) and have not detected any temperature rise either as a result of driving or charging. Access to the built-in thermocouples is another reason to get the Orion BMS hooked up. Short trips and the relatively light load of the Sparrow don't have me worried, but I would like my eventual final installation to incorporate some type of thermal management.
BATTERY MANAGEMENT SYSTEM
For a BMS, after a lot of agonizing, I selected a non-distributed BMS because the EnerDels provide a connector with pins accessing each cell and it's all handled with a single harness per pack. I selected the Orion BMS but haven't installed it yet. I would have preferred to use Davide's non-distributed elithion BMS, but, in addition to the EnerDels, I also have a number of other battery packs which I am using which are already configured for non-distributed BMS' and I had wanted to use this new BMS with those as well.
For charging, I am still living dangerously as I have not had the Zivans reprogrammed to limit their maximum voltage. I meticulously recorded my charging times and have made a detailed table showing time vs. voltage to reach three different charge levels for both my 120vac and 240vac Zivans. I bought a new 2-hour Intermatic mechanical timer and, to show you how paranoid I am, I'm currently charging through TWO timers in series, just in case one of them stops ticking. In addition, I bought a 200vdc 10A lab power supply which is not only programmable for voltage and current but also has a programmable upper voltage safety shutdown feature. Been using the Zivans and this power supply for four months now, and haven't yet installed the Orion BMS.
Each time I've measured the packs and their cells, irrespective of the SOC, all the packs and their individual cells have identical (matching) voltages. I'm not being lulled into complacency, and intend to hook up the BMS, but my present thinking is that I might only rig up a low-voltage alarm and maybe a shutdown circuit and then simply have the BMS integrated with the charger for use only at home. This is still a work-in-progress and I need to have the Zivans reprogrammed one of these days...
I normally keep the pack around 130vdc (~50%SoC) and before driving charge to an upper voltage of 140vdc (80%SoC) and keep the discharge well above 115vdc (25%SoC). For longer trips I've charged to a maximum of 145vdc (92.5%SoC). The furthest I've driven on a single charge so far has been close to 40 miles while operating well inside the voltage limits of these two parallel strings. One neat capability is that if I need a Quick Charge I simply hook up a bunch of Zivans in parallel (as well as the lab power supply) and can stuff as much current as I want into the pack quickly (without stressing it).
Having just spent four months driving my rejuvenated Sparrow on Lithiums, I don't think I'll ever go back to Optimas. I'm just about to buy more EnerDels for my red Sparrow, but my orange Sparrow still has very serviceable Optimas that refuse to die...