Gauging interest in making new alternator voltage regulators

BillGrissom said
I see talk of different batteries needing different charging controls, but no explanation. Add that people are beginning to use lighter Li 12 VDC batteries, the only hindrance being price (>$600). There are various Li types. When I replaced the lead-acid batteries in my daughter's razor scooter with LiFePO4 (LFP) type, I had to buy a different charger since they like ~17 VDC vs ~14 VDC for lead. But, the auto Li batteries may be designed more compatible. Not sure how the Vreg would better match the battery. You can't go higher on charging voltage, since that can damage other consumers, like burn out the headlamps. Do you mean controlling the output current instead?

I did consider a controlled current regulator, but it would add a lot to the price and make installation harder. It may happen later if there's demand for such a thing.

The different charging controls was a request from another board and I had to research it myself. Your standard battery (Flooded Lead Acid) is going to need extra voltage to charge when cold - some recommend cranking the voltage up to 15.8 at freezing, although as you noted this can take a toll on other electronics. If we clip that at 15 volts max, this curve would also work fine for AGM batteries (like Optima). And you back off the voltage a little at higher temperatures.

Gel cell batteries are not all that common, but they need to be treated gently and run around half a volt lower than a FLA or AGM battery. You really, really don't want to make these build up gas.

Lithium batteries, as 67Dart273 noted, have onboard management circuitry. They can also handle more voltage at higher temperatures. However, unless that onboard management circuitry includes a heater (Antigravity's battery line doesn't, for example, but some of the Dakota Lithium batteries do... but not all of them!), you want to shut off charging and drop the supply voltage to 12.8 volts when you hit freezing.

And there's also the possibility of letting the regulator support 16 volt race batteries.