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some examples show lithium batteries being charged directly from alternator. others show lithium battery being charged via DC-DC converter. Which is the correct/ preferred method? I was under the impression Lithium batteries required specific charging profiles?
DC-DC unless you want to destroy both alternator and battery. Victron has a video somewhere on their blog you might want to look at.
Is there no requirement for a DC-DC here?
How can an arrangement like this include a method to connect LIthium Battery to Starter battery for emergency start?
How can starter battery be charged by solar in a system with Smart BMS?
If you are wanting to ensure the starter battery is kept topped up by the Solar, then yes a DC-DC with source on the lithium and destination on the starter would do that.
As a point of design, I would configure a relay into the ignition switch of the DC-DC. This would mean that when the engine is running the DC-DC is disabled. If the relay is NC and feeding a positive signal into the ignition switch of the DC-DC, when the engine ignition is on, the relay will open and the DC-DC will shut down.
OK, I get that we need to limit current/ protect alternator. My confusion is in the actual charging of the battery. I have read that Lithium batteries need carefully configured charging profiles (absorbtion, float etc). It seems that with either the DC-DC solution or BMS 12/200 or Smart BMS 12/100 the lithium battery is just connected straight to whatever voltage the alternator is churning out. What am I missing here?
Also, what is the point of the Smart Solar controller charging via set profiles when the alternator is just punching our say 14.8 constantly at the same time?
