Thursday, October 07, 2010

Lithium Update


With about 3,500 miles on the Lithium batteries, that's about 80 charge cycles, everything is working well. We make the climb up the long hill with ease now, even with groceries and a passenger. Driving the car is more enjoyable now so I find that I drive her more often. I think I'll even put in a nice CD player.

I occasionally need to top-off a few of the Lithium cells individually because my charger doesn't step down it's output until it reaches about 176 volts. The BMS shuts off the charger when any cell reaches 3.79 volts, which often happens before the charger reaches that step down point. With such high output the balancer can't shunt off enough to keep voltages under the limit, so it shuts off the charger. I should just re-program the charger to step down from the high output at around 168 volts, then the balancing system would work automatically.

When the BMS gets up to where it is balancing (shunting?) about 35 to 40 cells and it's over about 85 degrees outside the BMS unit gets too warm and shuts off. This is with the trunk open, parked in the shade, with good airflow. I can still charge the pack by turning off the balancing function. This over-temp shut off didn't happen when it was 60 or 70 degrees outside.

If I converted another Force I would seriously consider using 50 of the 100Ah cells. Mine settle to about 3.4 or 3.5 volts soon after the charging stops so the pack voltage would be within the controller limits. I'd also consider using individual chargers set-up on a timer ($500 ~ 600). That way all the cells would always get fully charged without using a balancing system ($900) and a high voltage charger ($1,000).

Tuesday, April 20, 2010

Ellie Climbs the Hill


The lithium batteries (48 of the TS 100Ah) appear to be working fine on my 17 mile hill climb coming home from work. I climb 2600 feet, the last half at a 6% grade. With the lead pack the trip used about 37~38 Ah's and the car now uses 32~33 Ah's with 500 lbs. less in battery weight. She rides about an inch higher now. I leave the power selector in Normal mode with my foot a bit less than half way down on the pedal. This shows from 110 to 150 amps being drawn to maintain normal speed on the very winding mountain road.

It's funny to start with it showing 162 volts and get home showing 157 volts, after allowing a minute for the pack to settle. With AGM's it went from 170v down to around 145v and didn't recover much after settling. This killed the PowerSonic AGM's in less than 70 cycles. A better brand of AGM's would have lasted longer, I just didn't think that repeatedly drawing only 38 Ah's would be that hard on them.

I'm using a Hardy BMS and the 48 cells are staying fairly even on the three trips I've made up the hill so far, lowest reading was 2.877V with the highest cell at 3.062V at the same moment. My hope is that they'll stay that way if I don't discharge them below 2.8 volts, I use less than 40 Ah's between recharges, and I'm not drawing more than 150 amps.

Sunday, March 21, 2010

BMS Display


I mounted the display/control unit on the stock cup holder where I can easily see it. A couple of screws to lock the cup holder in place and some sticky back Velcro did the trick (yes, it was crooked when I took the picture).
With everything hooked up it was time to see how it all worked. First I charged the pack for 10 minutes and monitored the voltages as they crept up to about 3.5V each. Then it was time to turn the key. I only drove it around the parking lot because the cells have not been brought up to full charge yet, but everything works fine. The car does feel lighter with 500 pounds less in batteries.

All Hooked Up


It's been a while since my last post. Two driving trips to L.A. this month and being way over loaded at work has meant no time to tinker with the battery swap. But yesterday I took a day off and finished hooking everything up. I had a local expert check everything before I made the final connection. I still need to zip-tie lots of wires, put better covers on a few adjacent terminals, and tidy up the wire groups, but I figured I'd wait until I was sure everything worked before adding those final touches.

Saturday, March 20, 2010

The Front Box


This was the simplest layout I found for the front battery box. I wanted to keep the higher voltage connections separated but always seemed to wind up with them closer than I wanted. I even tried reversing the cell orientation in two of the 4-packs but it didn't help. I'll just have to be extra careful to cover the terminals and not drop a wrench :-). The main negative cable hooks to cell #1 in the upper left area. I still need to neatly zip-tie the little wires and shield the big ones with plastic insulation, but you get the idea what it will look like when it's done.

Tuesday, February 16, 2010

Mounting the Charger



I made a mount for the NG3 charger using two of the original rubber mounts. I'll put another rubber pad under the third leg. The fourth attach point is to the structural support on the inside of the trunk side wall. There is room to get behind it and put a nylock nut on the backside. A thick piece of rubber between the mounting bracket arm and the trunk beam will have to be enough vibration dampening.




The charger has good airflow and the cables are well clear of the moving trunk hinge. It's 3/4" away from the BMS case so heat should not be a problem, the BMS has an internal cooling fan on the side. **Note: I always pop the trunk open while charging. If I ever needed to charge while away from home I'd lean the back seat forward to allow more cooling air.** The Zivan comes with a 6' long power cord (grey). I only need 6" to reach the orange plug from the BMS so I'm thinking about shortening the cord to 1 foot. I'd still be able to plug into an extension cord if the BMS ever quit.

Connecting BMS Wires



I put the front 20 rainbow wires for the BMS (tinned first) into their respective connectors before attaching the ring terminals to the front cells. I wouldn't want to hook them to the cells and then work on the live rear ends :-o. Then I crimped and soldered the ring terminals to the 20 rainbow wires in the front battery box. The positive wire for cell #1 (brown) starts in slot # 5 of the green connector on the left. These are only the 20 front wires. I use a rubber mat over the cells in case I drop a tool, no shorts allowed :-).

Saturday, January 30, 2010

BMS Wires To The Front


I decided to run the 20 BMS wires up to the front box via the "tunnel" using nine feet of non-metallic 3/4" flexible conduit. There are rubber plugged holes behind the rear seat and in the front battery box that perfectly fit the water-tight connectors. The conduit has plenty of anchor points where the exhaust system would have been in the tunnel. The conduit is 3" to 4" higher than the power cables you see running under the driver's side floorpan.


I used the lower gearbox mount to attach a loose guide/clamp to keep the conduit away from the driveshaft and steering bootie. With everything exposed this was a good time to change the gearbox fluid.

Thursday, January 28, 2010

Where To Mount The Charger?

I'm looking at building a diagonal mount for the Zivan NG3 charger. The manual says vertical mounting is preferred but the unit is too tall. I had it mounted horizontally last year but now the BMS needs to sit somewhere nearby so going diagonally looks like the best option. The wires will easily miss the trunk hinge and the fans/vent openings can be clear of obstructions this way.


The Hardy BMS-48 has mounting tabs on it's outer casing that exactly line up with the two stock rubber mounts from the Solectria charger. I think that's a sign telling me to use the existing rubber mounts.

Filling The Front Battery Box


I thought I'd follow Reed's advice and see how much weight I could shift to the front battery box. At this stage it's easy to try new arrangements. It turns out that 24 of these 100Ah cells will fit snugly into the stock steel front box. It was tight enough that I had to wiggle two of the packs back and forth a few times to get the last one to settle in, no pounding required. This is without any foam on the ends so there's no insulation there from the chilly winter roads or from vibration.

** Note: The arrangement in this picture is not a good arrangement because it positions two terminals right next to each other that have a fairly high voltage between them (where the big negative cable attaches). Even with insulated wrenches (mine are just wrapped with layers of electrical tape) it's best to orient things to avoid having high voltages this close together. You can guess what would happen if I accidentally dropped one of the copper connecting bars! Once I start hooking up connectors I'm planning to use a thin rubber mat over the cells I'm not working on. **

The front battery box in this configuration has 154 lbs. less than it did with the 5 big lead batteries. I wound up moving one of these 4-packs into the rear box and you can see the layout in later pictures.

Monday, January 25, 2010

Fitting the Puzzle Pieces




With all the cells in their compression plates I had to re-arrange things a little. I tried several different arrangements and this one looks like the best. The positive cable connects to the upper left, the negative connects mid-way on the left so the stock cables in the Force easily reach the terminals. The Solectria fused cable will make the jump from the middle five sets to the rear two sets. The stock battery box lid fits nicely. I'm making this lead-to-lithium switch as simple as possible.





The warming pad is under the front batteries and the little black box with the temperature control is next to the cells. I like the idea of having a fuse in the front compartment so I'm using the stock Solectria fused cable to jump between these two packs instead of using the copper bar. I reversed the orientation of the four cells on the passenger side. The pink foam sheet is easy to work with if you use a new knife blade. My local hardware stores don't stock 2" thick sheets anymore so I used 1" foam.

Saturday, January 16, 2010

Learn Something New

I just learned that the prismatic LiFePO4 cells need to stay banded together with the compression plates on the ends so that they won't swell in the middle. Swelling can shorten their life expectancy. Thanks to the guys on the Solectria Drivers list I just avoided a costly mistake. So tomorrow I get to re-band some cells back into their handy 4-pack arrangements.

This means that I'll need to use that front battery box after all. Oh well, at least it's clean already :-).

Friday, January 15, 2010

Empty The Front Battery Box



Since the new lithium batteries all fit in the rear box this front box can now be empty.

With everything unplugged it's easy to remove the controller and set the A/C pump gently on the towel that protects the fender. I'm careful not to move the vacuum lines for the brake system when I set the pump assembly down on the reservoir.



BIG CAUTION HERE! - I always unhook the short wires between battery #1 and #2 first. The same thing on battery #4 and #5, remove the short wire FIRST! If you don't and instead you try to take the bolt out of the opposite end first, be ready for sparks, fire, and/or expensive replacements. The same concern applies in the rear battery box in several places.



The last picture shows that the stock cables are long enough to make a solid connection in the middle of the newly emptied front box. I coated the cable ends and bolt parts with anti-corrosive, then heat-shrink wrapped the connection. Then to make sure the connection never touches anything metal I taped and zip tied two layers of flexible foam padding around the connection. I should not need to open this front box ever again.

With 340 pounds of old lead removed the front end now sits 3/4" higher.

Thursday, January 14, 2010

Let's See If They Fit


Just for fun I unhooked everything and removed the eight old lead batteries from the rear compartment. Then I placed the new 4-packs into the empty compartment. I was pleasantly surprised to find that by unstrapping three of the 4-packs I could fit all 48 of the new Thundersky 100Ah lithium cells into the rear compartment. There's even room for one or two more cells! I had expected to need to place some of the new cells in the front battery box. This all took about 30 minutes from start to finish.

I notice that Ellie's rear end now sits about an inch higher than it did with all the lead back there. When I get the five front batteries (340 pounds) removed I'll post a note of how the front height changes.

The Lithium Arrives



The crates arrived and I couldn't wait to put them into the car. I noticed that the shipping weight was about 40 lbs. more than I expected. That was partially because the new cells came strapped in stainless steel and aluminum "4-packs".

In The Beginning




I started out in 2007 with a 1997 Solectria Force that had a dying AGM (lead/acid) battery pack. I replaced the thirteen 12 volt AGM's with thirteen new AGM batteries. The new batteries only lasted two years because I was using about 50% of their available energy to climb a 2,700' high, 16 mile long hill to get home. The leisurely 16 mile uphill drive took about 30 minutes. This was apparently too hard on the lead/acid batteries, even with a full charge.

In January of 2010 I removed the 884 pound lead battery pack and replaced it with a 350 pound LiFePO4 pack that has more available energy.