Batteries
General
- Most people running 2x 6S packs expect to burn 4000-6000mAh per pack in a 5 minute race.
- You will have <1hr to recharge between races. Typically 45 mins.
- Charging a pair of 6S batteries is typically easier than charging a 12S.
- Safe handing and charging processes must always be followed in the pits, including use of lipo bags.
Li-Po
- Hobbyking
- CNHL
Li-Ion
DIY pack for CYBR TRK
- Cells are reclaimed Samsung 21700 30T from NKON.
- Spot welded using an eBay China special PCB and handheld electrodes.
- PCB needed some solder reinforcement as pictured where tracks started to cook.
- Instructions called for ~80Ah battery. I ended up needing a 100Ah (1000cca) in parallel with slightly crusty 36Ah (330cca) being constantly topped off by a PSU to >14v for decent welds.
- Electrodes need to be regularly redressed. Not too blunt, not too pointy. Like a small ball point pen seems to work.
- Did try using rewound microwave oven transformer, pulsing a solid state relay. Seemed like not enough current for too much time. Electrodes would melt without welding the nickel at all.
- Initially planned to use 0.3mm nickel strip for high current handling but getting pure 0.15mm to weld was tough enough, so that's what I went with. It's in links of 3 parallel rungs which seems to stand up to the task.
- BMS - Cheap and supposedly rated for 40A continuous, 70A peak (rules stipulate 30A fuse at 12s). Performance in races was ok, but ran so hot it melted the battery wrap, then later burned out.
- Plan to try 100A DALY unit
DIY pack for Rule Zero
- BMS for "big packs": 12S/45A version of Aliexpress BMS
- Secondary BMS: Amazon 14s 40A Lithium Battery Protection Board
Used EV
...
VW GTE packs
source: https://zoomev.uk/products/vw-1-086kwh-battery-module-12s-48v
cad model: https://grabcad.com/library/vw-gte-hybrid-battery-module-1 (step file)
To "use" (discharge) them, you just connect your load to the terminals, they're always "on". To (non-balance) charge them, you just give them 50.4V and they accept current. We think the onboard BMS isn't like a standard hobby grade BMS, it won't disconnect the output if the voltage gets too low, the current gets too high or they're about to be overcharged. They may have the code to do that, but need to be connected to a suitable contactor to actually do the switching, there's no compoennts to do load switching on the PCB. There're a couple of ways you can charge them, which is best depends on your skills, budget and what you already have. the traditional way would be to rip out the pcb from the battery, solder in balance leads and use a standard lipo charger (e.g. a hota D6). Its rare to find 12S capable chargers, so you'd have to electrically split it into two packs, and charge as two 6S packs. The alternative route, and the way Brian Corteil and Mark Mellors are going, is to use a 50.4V power supply (e.g. https://www.aliexpress.com/item/32829834144.html or https://www.aliexpress.com/item/1005004586061770.html ) with an Arduino and a CAN transceiver. Brian has mostly figured it out but it still needs a laptop and a wiring mess to do the balance charging. We're hoping to get a batch of PCBs made at some point and put it all in a box.
useful links:
https://openinverter.org/wiki/VW_Hybrid_Battery_Packs
https://github.com/Tom-evnut/VW-bms
https://openinverter.org/wiki/VW_Hybrid_Battery_Packs
https://github.com/jomytec/Teensy-CAN-bus-controller-in-EV
Brian's balancing code: https://gist.github.com/Corteil/f83ee4708a0838859fcd7e00524226ac
balance connector:
TE 1-1670990-1
1355717-1
https://www.digikey.co.uk/en/products/detail/te-connectivity-amp-connectors/1355717-1/2187722
Chargers
- Turnigy Accucel / HTRC C150 - Runs directly from mains, only just charges packs between races at 1hr intervals
- HOTA D6 Pro - Pro runs directly from mains, little faster than C150, popular in the pits.
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