This page is not yet finalized, and more discussions are still to happen.
...
Aux Batteries Used in MSXII (and spare)
| Battery Image | Chemistry | Capacity (rated) | Weight | Link | Note |
|---|---|---|---|---|---|
| SLA-AGM | 7.2Ah | 2462g | Standard battery - canadian tire, amazon, etc | Spare battery used to 'jump start' the car |
| NiMH 10S1P | 5Ah | 743g | https://hobbyking.com/en_us/turnigy-sub-c-1-2v-5000mah-high-power-series-nimh-single-cell.html?___store=en_us |
| Battery installed just before FSGP2019 | ||||
 | NiMH 10S 1P | 2.1Ah | 271g | https://www.embeddedarm.com/documentation/third-party/ts-bat3_panasonic_hhr210aab.pdf |
| Battery used for FSGP2018 (not the exact one pictured) |
The page will go over the use case for our AUX battery, and go over the different battery types that we can use.
...
This is now an older chemistry and is no longer relevant. From my research, NiMH has surpassed it in every category.
Li-Ion
No Li-ion Lithium based secondary batteries are allowed per regs.
LiFEPO4
No Li-ion Lithium based secondary batteries are allowed per regs. I'm really hoping that ASC changes their minds on this, as the main issue with Lithium batteries is thermal runaway, and LiFEPO4 batteries are not susceptible to thermal runaway. For now, this may be out of the question.
Other Strategies to eliminate AUX issues
There are several other approaches we are also taking analyzing to avoid all the AUX issues we have been having as well.
- Properly analyze the minimum voltage for switchover on the DC-DC power path IC. Choose the resistor divider accordingly.
- Add a time delay filter on the voltage measurement circuit if it does not impact any other switchover time characteristics significantly.
- Use thicker wires and nickel strips in the construction of the AUX battery (not the cause of the issue, can but it can certainly help).
- Shorter wires for the AUX current path (don't go from battery to driver AUX Switch then back to battery - too much resistance and voltage drop).
Final Decision
We are going to be using the NiMH 10S 1P battery made from Turnigy cells bought from Hobbyking.
This AUX battery will sit inside the battery box.
We will also be using a similar auxiliary battery to power the horn and driver ventilation fans, possibly with increased capacity.