backchannel: bullshitting about LiFePO4

I am continually amazed that people confidently BS about things that are knowable. This is from a thread in /r/overlanding

If you buy two matched batteries you can just parallel them.

All the common banks we discuss in this sub can be combined while charging. They should be isolated when not charging, but the relay or DC-DC does that automatically anyhow.

And FWIW I run a simple 140A “smart” relay that cost about $40 from a reputable marine electrics place.

Same. My VSR charges the 280Ah LiFePO4 at current/voltage appropriate for the battery and at current appropriate for the alternator. Sample data linked below.

There’s plenty of people wanting to sell you $2000 BMS because they are making good money convincing the overland crowd they need all this stuff.

And there are plenty of people wanting to convince/browbeat others into believing things that aren’t true, or only partially true, or only true in certain circumstances.

I=V/R & empirical data > bold statements

Srsly, who makes/markets these $2000 BMS? I suppose it’s possible to spend that much on a bespoke BMS if you try really hard¹, but it’s not like that’s where the consumer market is.

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• data from 50 direct-charging runs
• analysis of data from 40+ installs (good, bad, and ugly)
• the effect of resistance on charging current in direct-charging setups
• myth: you must use DC-DC to charge LiFePO4
• myth: you can’t use a combiner to charge different chemistries

1. on an interplanetary probe for NASA, maybe? ↩