It seems fair to explain how i come to the current project of Ampera range extender.
I got idea couple of years back when we bought a family car Opel Ampera an EV with 1.4l genset.
I later got quite intimate with its inverter, DCDC, charger and battery. That battery configuration got me thinking… How could i fool the car and add more battery in the back. Because lets be honest, 50km range hybrid is not enough, not for to AND from work.
So i now decided on next items:
1x VW passat 9kW battery
1x Ampera contactor
1x Simp BMS
10m length 25mm2 welding cable, cable ends, ties, shrink wrap etc…
What i did was take Ampera to a friend with a car lift. From there it is only a mile to Opel service point.
We followed the procedure from Volt/Ampera manual
1. Disconnect 12V battery GND cable
2. Pull out service disconnect fuse. By that HV is disabled and so inherently safe.
3. Then we took down the covers and shields under the car.
4. We disconnected control cables and coolant hoses for the battery, Here i needed to be carefull. My plan was to bleed as little as possible of the coolant from the battery. I made plugs and hose ends so that we plugged up the coolant hoses before much coolant could leave. Funny thing is i only had to plug the first two hose – socket pair. Inside other one vacuum held the fluid back for me to plugged them up.
5. Next we stacked a bunch of pallets under the car with some heavy timber to take the load of the battery
6. We lowered the whole car to that carrier and preloaded it.
7. We untorqued the carrier M10 bolts and then unbolted them.
8. When we raised the car i also slowly unlatched the HV cables and took them out. They have more play and i could pull battery halfh way out of the channel.
9. Then we lifted the car up and took out the remaining M6 bolts on top. We took the cover off and inspected the battery.
10. I decided on how to rout my additional 25mm2 cables. I connected one cable from the first positive contact all the way back to the right side of the T section. There was enough space to fit grommets there and still move the battery cover around. I decided 25mm2 cable would be ideal, because it would be small enough and it can carry up to 250A current from my add on battery. I routed the cable under the original orange conduit.
11. I connected the negative cable on the left side of T section and routed cable from the back. There is plenty of space there.
12. I left the cable some slack under cover so moving the cover wouldnt cause any load on the cable. Then i drilled the holes in cover on the right side and put two metal grommets there. Yes metal because they can be thinnest and have low profile.
13. We put the cover on and put the remaining cables inside orange tubes so they are marked as HV cablec to first responders!
14. I routed both cables inside just on the side of DCDC converter cables. There is enough space there under the plastic air channel. Finally i put Anderson 175A pins on both cables and put them in one grey connector. I am confident 175A continuous will be enough in paralell.
15. We put everything back in reverse order with minimal loss of coolant. After everything i returned fuse back to its place and put GND back to battery. As a precaution i took out the WOT sensor and taped it to the side of the coolant container. This way the dreaded “service HV charging system” couldnt happen since car wouldnt know if the tank is empty. Then i needed to fill up the tank and hope everything would deair through normal process.
Official procedure is to connect to the car and run some service procedure, but i dont yet have equipment to command the car and deair the system. I saw they command the 4 way valve to swing througl some service procedure and that takes care of every eventuality… Well see.
Now that i have live 360Vdc in the trunk i can play with it. First i will connect my Mazda charger and command some 10kW charging while car will be ON! This will confirm i can use connector normally and car will think it is in regen at the time.
I went on testing with my direct connection to Ampera battery.
1. i connected an extension cable from my Mazda directly to Ampera battery connector. Then i turned on charger and commanded slow increments of 5A untill i stopped at 25A which is 10kW and what my household can sustain.
2. I observed what is happening with SOC calculation in Ampera.
DOH! Here i found my first obstacle. Obviously Ampera doesnt calculate SOC from the current sensor inside the battery. Rather it uses charger reports to integrate SOC. Now that i fed current into the battery and charger wouldnt report anything SOC wouldnt raise.
3. I also connected original charger and here i immediately got the dreaded “service HV system” error. I managed to erase the error with my Torque pro.
4. Then i continued to charge with car OFF. When i decided that battery is full at 392Vdc i started the car….!!!! Car wouldnt throw a definite error at me, but it did set the SOC at 0% and limit engine throttle so i could drive only up to 50km/h. I tried to erase errors, but i couldnt since there was not any to be found!!! Well in the end i just connected the charging cable and let the car sit on the EVSE for some minutes. In the end car returned 100% SOC and when i tried to drive off it offered up to 80km range from the start.
That was good news for my next planned experiment. To add a 9kW battery direct in paralell to first one and see what happens.
1. I conditioned both batteries to the same voltage of 390Vdc.
2. I made a wooden cradle for individual VW cell modules. Those are wedged between wooden supports such that battery cant fly off in case of sudden stop.
3. I installed the 9kW battery in the trunk and connected it via 300A fuse to HV connector in the trunk. Everything is still for testing…
4. Since batteries were full we went for a drive. We managed to drive for a 78km of mixed driving untill genset turned on. Driving included like 75% of highway driving at 110km/h. I observed increased SOC in the beginning of drive since car thought it was still at 55km.
5. I let both batteries charge through original 3kW charger which even now looks like it would last for 6H. Tomorrow we will again test range if the car can work out more range… I am sure easier driving would show even more range.
Later on i intended to make a box from Alu sheet metal and make a new trunk bottom where i will fit the new cells in the back. I will leave an option to fit a 10Kw 3 phase charger if i will be successful with simulating charger CAN bus reports.
Notice 8.8kW consumed! This shows that car actually uses internal current sensor for driving. But for charging something else is used.
leafdriveblog 