Custom Enginer 5kW 800 miles tank

I have a custom Enginer system that I bought from Jack over a year ago. After three bad 3kW converters, I think the system is now finally stable. At one point I was SO FRUSTRATED with the poor component quality that I placed it up F/S on PC, luckily no one purchase it.

My current PHEV spec consist of the following at the moment.
- Enginer Enclosure, breaker, dash switch and mounting
- Enginer 5kW 48V-240 DC-DC Inverters
- 90Ah Thundersky LYP90AHA batteries (16x)
- Modified ePowerCity 1000 Watt LiFePO4 charger (modified cutoff at 56.5V cutoff)
- Cellog 8M (4x) configured for <2.8V & >3.8V alarm
- Absolutely NO BMS
:boom:

Standard Prius Eco-Range Accessories
- Scanguage
- Coastal EV Switch
- Grill block (100% upper / 50% lower)



My typical daily commute is ~ 16 miles each way in Silicon Valley. 40% City & 60% Highway.
Fuel economy can change as much as 10% based on the time of day due to traffic and driving style.

=== W/o Kit performance ===
Summer 50-55 mpg with 87 octane
Winter 43-49 mpg with 87 octane w/o grill block

=== 5kW Kit ON 1st tank performance ===
Winter 52 mpg with 87 octane w/o grill block

I received two "upgrade" 5kW converter from Jack that were pickup thru 3Prong (Berkley, CA). The first unit was not able to charge my TB pass 56% SOC :mad2:, while the second was only able to charge up to 60% SOC. I believed this was done on purpose to minimize the failure rate of the component as the original 3kW unit was able to charge pass 70% SOC. Unfortunately this also dampen the purpose of PHEV :doh:. With so little headroom the Enginer kit only improved my mpg by a measly 3 mpg. I was PISSED!

After bugging Jack for the pot functionality for a week, I finally got the instruction. I adjusted my voltage cutoff to 243V and was able to charge up to 70-75 SOC.

Finally I was able to achieved part of the promissed of PHEV :amen:



=== 5kW Kit ON performance ===
Winter 82 mpg with 87 octane with grill block
Best 100 miles performance is 120 mpg

Average speed:
Scanguage 22 mph
City speed target 33mph and 41mph.
Non traffic highway speed is target of 65 mph
Light traffic highway speed target of 33mph and 41mph
Heavy traffic highway speed is < 32mph

By changing when I go to work by 1 hour, my fuel economy changes shot up to 99.9+ mpg. My driving style have also been adjusted to maximize my mpg. This is what I did.

0. Charge up the traction battery to 70-73% before any trip. Since the area is pretty flat I won't don't have the risk of the Triangle of Death.
1. Maximize EV mode AMAP with speed <34 mph. I try to maintain 33 mph with < 15A draw.
2. If traffic speed is too quick, then I would step it up a not and maintain 41 mph with pulse and glide.
3. Light traffic highway speed I would try to maintain Warp Stealth at 50-52 mph

Using my Coastal EV and Scanguage with constant monitoring, I'm always force EV immmediately when speed drop < 34mph & upcoming traffic congestion ahead.



I'm happy with the current setup. It's fun trying to fillup once every 3 week. Especially with my work subsidizing for daily 4kWh charge (~ $0.80/day)

With that said, I can not recommend this to ... say my wife for daily commute. There are just too many factors to monitor to make things goes smoothly, assuming no component failure.

In term of financial investment by making it PHEV and 100% of the electricity is being subsized by my employer, I'm saving $8/week. My kit costs me $3700 (w/o tax credit) so it will take about 9 years to recoupe the cost at $3.25/gal Is it worth it? Financially probably not, but being able to drive 100 mpg and smirk at SUV, now that's $PRICELESS$ Don't feel too sorry for my mpg as my weekend drive only gets 15 mpg on it's 2900 lbs chasis.

 

Many of us would love to have Toyota's 2012 PHEV Prius, PIC, or Hymotion PHEV system.
Unfortunately they are cost prohibitive so that's why we bought the Enginer System.


I will use this post to document my system modification, modification logic, and instructional guide of how to make the best of what we have without spending the big $$$ that we're saving for a Tesla Roadster.

The Enginer's system is a very simple yet brilliant idea concocted by Jack Chen. This basically uses an external battery pack and a DC/DC charger to maintain the stock battery pack at "optimum" state of charge. With such a simple system, it amazed me that "no one in the 10 yrs history of Prius have done it before". Like all things the devil is in the details, I guess!


=== Section #1 - DC/DC Converter ===
This is the heart and soul of the entire system. A DC/DC converter basically changes the 48VDC voltage to 240VDC to charge your traction battery. Ideally this should have feedback from the CAN bus to monitor the SOC of the battery, and should be stage charger. However that would add significant cost to this cost effective system.

Couple things you need to know:
1. This unit is not that much different from your household switching power supply. It stores power in the magnetic field. Adjustment to the duty cycle basically regulate the amout of power output.
2. The MOSFET switch like other semicondutor device are sensitive to HEAT and ultimately the amount of POWER delivered. To maintain long term reliability these need to be thermally controlled thru temperature switch & fans.
3. (My Theory) Because these are switching power supply, they are suseptible to noise and inrush current/voltage spike from the Prius MG or your second Enginer DC/DC converter. If not well protected they can go *PooF*.


As you can see I choose NOT to install my DC/DC in the Enginer enclosure, due to the fear of confined space and heat buildup. The DC/DC converter is mounted on two aluminum bar which are bolt onto the sheetmetal. I was too lazy to make a nice base like base like what adric did. I also removed the two drained plug when it's not raining to bring in some cool air during driving. It's easy to reinstall them from the bottom side when it's wet out.


Here's the layout of all the components inside. Pretty standard stuff.


This is my procedure for adjusting the voltage and current with the system installed.
You need Scanguage II to monitor the BTA, BTV, and SOC to accurately perform this adjustment.

Keep in mind that the max voltage and current varies from system to system and car to car.
These potentiometer are standard 50 turn pots, however we don't don't know exactly where they are from the factory, so take your time adjusting no more than 1/2 turn per iteration.

You can adjust the Current and Operation Voltage w/o openning your converter as long as the drilled access hole line up. Use a flashlight to survey this before opening your converter.

a) Start off with 60% SOC.
- If your SOC is too high drive around to drop it.
- If it's too low use your Enginer kit to charge it up to that level.

b) Current Adjustment first.
- Park your car monitor the BTA consumed. It should be somewhere between 0.9A - 2.6A (mine is 1.4A) depending on what you have on. Wait couple minutes until it stable and record that.
- Turn on your Enginer kit and see the updated BTA. It should now be a negative (-) value.
- Adjust the "MAX Current Adj" pot so that the delta is ~13-14A.

Many of you want to get the MAXIMUM current possible (+16A) to maximize your EV. However, I caution against this. Remember heat KILLS! I would target for 13-14A delivered max.

c) Voltage Adjustment
The problem of our Enginer system lies mainly in this portion. The Prius have a Ah counter that monitor the total amount of electrons flowing into and out of the battery to determine the battery State of Charge (SOC). However, our DC/DC converter doesn't know anything about SOC, all it knows is the 240V output and how much current it need to push to achieve that voltage. Unfortunately sometime the SOC and 240V doesn't line up properly and the DC/DC stop charging at a less than optimum SOC. My case it was only 56%. So we need to increase the DC/DC voltage so that it continues to charge up to the 70% SOC.

- Turn on the Enginer kit let it charge your traction battery. Until the BTA is between -2.0A to 1.4A (your baseline consumption in current adjustment).
- If the SOC < 70%, make 1/2 turn CW to the "Operating Voltage Adj" and see if BTA current increase (in negative direction). If it doesn't adjust the "Max Voltage Adj".
- Repeat above step until you achieve 70% SOC with 0A BTA. At the end take a look at the BTV value, it should be somewhere between 240-245V. Mine was at 241V, which is PERFECT!

You can be aggressively adjust the voltage to a high value to increase SOC > 70% but that increase your chances of getting the Triangle of Death AND increase heat load to your component and their long term reliability. I believe the original 3kW converter died mostly because of this problem.



As you know by now, I'm SUPER paranoid about heat in the system. The DC/DC converter have alot of cooling vaines on the outside and everything perfectly smooth in the inside. The fan is located inside with plenty of air flow. So to further improve cooling I installed couple of chipset cooler to chill the MOSFET bank.


=== Section #2 - Batteries ===

=== Section #3 - BMS (or lack off) ===

=== Section #4 - Charger ===

=== Section #5 - Misc Components ===

 

Gen2 Prius basically have 168 NiMh cells. Toyota plays it ultra conservative and limit the charge to < 80% SOC, for long term durability. I read somewhere that base on maintaining 40-80% the extrapolated data for battery reliability is something like 12 yrs. I don't blame them for being so conservative.

That means ideally the peak charge voltage / cell should be somewhere between 1.40V to 1.55V, when you charge beyond this there increase risk that if you have imbalance a bad cell or two can cause over charge of other cells and cascade the failure rate.

Similarly if you discharge your cells pass the 40% SOC you risk reverse bias the cell so that's why the ICE kicks in.

Now for PHEV, I try to maintain between 50-70% to allow enough buffer for the "what iff"

 

mrbigh, thank you for the very thorough explanation and guidance. With high cell count the balancing act become extremely tough. I guess that's why Toyota doesn't bother to do so and just run 40-70% SOC and call it good. You are absolutely correct that if we try to operate at the knee, it's dangerous ground.

Without financial limitation the best way to extend Prius EV is to put more packs in parallel like you have done. Unfortunately that will not suite my need.
1. $$$
2. Space multi pack takes up
3. Low power usage due to ultra conservative Toyota theory. 30% / 1.3kWh each pack
- even with 6 packs you still only get to use 2.34 kW. You can do the rest of the math regarding miles, payoff, etc.

Again I completely agree with your assessment of the danger that's why I only charge my traction battery up to 70-73% SOC (that 7bar for those w/o scanguage) and try to sustain the SOC throughout the drive between 60-70 SOC if I can help it.

With my own Thundersky LiFePO4 batteries, I operate them between 30-80%. I have alarm for < 2.8V (under 1C load) and high voltage cutoff at 3.8V. That should be plenty safe to get me my 3000 cycle life (8-11 years).

 

pbui, I'm relying on the two drain holes to provide circulation and cooling. I'll probably design a plenum that can provide a more efficient Venturi effect on cooling.

If you guys noticed that when the large 48V fan of the Engineer kit kicks in the current rate drop down to a trickle during idle. You can monitor this with Scanguage BTV, BTA, SOC configured. Once my fan kicks in and my BTV is > 233 (~65% SOC) my charge current drops from 13A to 3A almost immediately.

Note the charging is not affected under load. The BTV drops to < 210V when my MG is running and thus with a low enough voltage delta the Enginer DC/DC converter is capable of providing 13A charge. It's quite annoying because at you want to maximize your charge at red light because during traffic the 13A charge is shy of the 15-20A normal commute need.