Out of Spec Kyle explains how voltage and amperage work together to slow down charging cars with higher voltage batteries / architecture

jgillmer said:

What would be the specs on the 98 kW MME battery pack and system?

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Todd said:

Former hardware engineer here: I've created battery chargers for li-ion batteries at the very small scale as well as NH batteries.

At least for the small batteries, charging is usually a constant current source and stopped when the voltage gets to a certain point (or when the calculated current exceeds some threshold, or heat gets to high, etc.)

The battery spec sheets list a 'charging current', or a current curve to maintain when charging (and also, discharging, btw)

So if packet batteries are anything like their hard packaged counterparts, it really doesn't matter the voltage of the battery pack as long as the charger can match the necessary current requirements of the battery - and of course, the voltage of the charger will always have to be significantly higher than that of the battery pack in order to generate the required current.

Anyhow, point is, some electronic devices are 'driven' by voltage, an audio source, for example, and some devices are driven by a current source, such as LEDs, for example.

Having said all of that, higher total voltage battery packs allow for smaller wires to generate the same power... up to a point where super high voltages would cause other issues.

BTW, an interesting spec on ALL battery data sheets is the amount of 'cycles' (full charge/discharge) a battery can take to maintain their guaranteed charge... also known as battery degradation which is very real.

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Auto Motive said:

Interesting read. What would be your choice for a 12v battery. I was hedging on Optima since I used them in my vette.

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