MiniBMS Boards

The MiniBMS boards arrived and all of them are installed with a green led on. The boards went on pretty easy, except I had to remount the controller and the heat gauge sender to leave some room for the boards.

Notice, the one board could be pushed sideways to make room for a cable, nice.

Twenty boards on the trunk pack.

Heat gauge sender mounted on a copper tube strap.

Elcon Charger... finally

Surprise, it works! It turns out that the Elcon PFC 1500 didn't support 115v AC input so I ordered a PFC 2000+, (from EVolve Electrics) which provides 9A output for 115v input and won't go over the 15A limit on a household plug. While this is underpowered, I was going for versatility. It fits well between the cells under the hood. The MiniBMS should be here Monday. I'll get it connected next week, just in time for the nice weather.

Time to wrap things up

Well now that the weather is warming I'm making a move to get the del Sol finished up. I'm going to use Dimitri's MiniBMS and an Elcon PFC 2000+ Charger. The Elcon web site has the output for the PFC 1500 listed as 8A for 115V input but I was told that is for 230v input so the actual is half that, 3-4A. But, the PFC 2000+ has an output of 144v/10A at 115v AC input and is only $130 more.




I've also had to replace the PB-6. It was the cause of my jerky startup. Notice this is a genuine "Curtis" product from KTA. "Beware of imitations".

Charger

In September I ordered a Chinoz 144v/8a charger for LFP from evcomponents.com. After it didn't arrive for a couple weeks Dave Kois sent me a loaner Manzanita charger. I've been using that since but still wanted an onboard charger. Finally last week a charger arrived. On the evcomponents.com website the charger I bought was listed as 10.2"x10"x5" and the one that showed up was and Elcon 144v/8a with the dimensions 14"x7"x5.5". So, it wouldn't fit in the bracket I had built for it a few months ago.

So I hunted around for a place to put the charger and found one in the battery rack. When the charger was finally hooked up to the pack I got a "Battery Disconnected" error from the charger. Dave Kois said the charger wasn't programmed for my cells and he eventually sent me another manual with instructions shown below. When I pushed in on the LED/button, it went into the case of the charger and didn't effect the programming. So this one's going back to whence it came.


Choice of Charging Curve (curve 1~10)
1.The LED will flash red several times when AC is first connected, then the LED will flash green once. The number of red flashes denotes the present curve. E.g. If the red flashes three times, it means the present curve is curve 3.
2.To choose another curve, please cut off the power supply first, then unpeel the label, pressing the button while connecting the power. If you want to choose curve 3, release the button after the 3rd LED Flash. Now the selected curve (e.g. curve 3) will be recorded in memory. If you want the charger to work with the selected curve (e.g. curve 3), cut off the power and reconnect it.
3. Factory customizes 10 charging curves before delivery according to customer demand. These are 10 combinations of voltage and battery size for the same battery type.

New controller & Kill A Watt

The Kelly KDH14800D finally arrived. It is larger than the B model and uses a 0-5k ohm throttle. So, I had to cut out the 5v input to the PB-6 because it was causing a ton of interferance with the potentiometer. The controller has great pick-up from a stop and could even accelerate from 30 mph pretty well. It topped out at 73 mph.

I drove 10.4 miles and recharged the pack. With a kill a watt meter it registered 4.47 KwH. So, 429 wh/mile. Hmmm, room for improvement? The brakes might be rubbing a bit, the tires need inflating, I was pushing the car to see what it could do and the Kill A Watt is measuring from the wall so it takes into account any loss in the charger.

New controller & single cell charger

Kelly Controls sent a new KDH15600B, which is 11" long compared to the 7" KDH14401A. It fits into the same spot as the smaller model with only one new cable needed. Notice the paktrakr resting there. I'm waiting for an extension cable to run from the last remote in the trunk. Then I'll strap the remotes and display in a permanent location.



Single Cell Charger
After the initial charge to the TS cells and they rested the voltages were all between 3.32V and 3.36, which is pretty good. I bought a single cell LiFePo4 6A charger to manually balance the cells in the interim before I can find an inexpensive and adequate BMS. The single charger has a 3.8V cut-off and each cell charged for 1-2 hours then after rest the cells are all at 3.50V. The weather was a little colder the past few days, -5F and the garage was cold too and each cell appeared to dip a little to 3.48V. I expect when they warm up they might come back to 3.5V.

According to the ThunderSky charging curve 3.8V is 75% charged and the remaining part of the charge curve is at 4.2V with a tapering current for about 30-90 minutes. So, I'm not sure that shunt style BMS that limits part of the current to 3.8V is appropriate unless it can "release" all the cells once they are balanced to finish the charging cycle.

Activating Thundersky LFP

Thundersky LFP cells require an "activation" charge cycle before discharging. James from evcomponents said "The max is 4.25 V Although you should only do that the first time for activation. After that 3.8 V should be the max. ".

The Thundersky "quality certificate" says:

"The electricity is half loaded when the batery produced, the battery cannot be discharged directly under any condition, and must be charged before first use. Please check and if the voltage is 4.2v means the battery is fully charged. If the battery is used in series there must be professional technicians to handle and required charger and BMS must be attached in use."

Then in a separate print out it says:

"Warning
Before first discharge the battery, please charge it to 4.2V with the constant current of 0.1CA~0.5CA and stop until the charging current falls to 1% of the original."

So, I have the Manzanita Charger set to 191V as the cutoff for 45 cells at 4.25 each. Below is a graph of the paktrakr data from the charging cycle for 8+ hours. The amps are X10 to fit on the same scale as volts. The small blip before the "hockey stick" is when I turned off the charger to go to bed and restarted it in the morning. The charger started tapering the amps at 191V and then the voltage dropped. I set the amps to 10A manually and then adjusted again at the end to 1A.