This page is not yet finalized, and more discussions are still to happen.
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The NiMH battery packs (both styles) seemed to be giving us lots of issues with draining too quickly (since we often powered the car from the battery during troubleshooting), and seemed to cut out while attempting to close the relays too early (at 12.9V or 1.29V/cell) with still a lot of capacity and useable energy left. Not all of that is due to the cells, but we can definitely improve it.
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.
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No Li-ion batteries are allowed per regs.
LiFEPO4
No Li-ion batteries are allowed per regs.
Other Strategies to eliminate AUX issues
There are several other approaches we are also taking 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 it can certainly help).