Originally Posted by Jd1
Ok, I bite, what you suggest for setup parameters ?
The reason I was thinking about a dedicated lithium regulator is because the charging
is quite different. There is no float, there is no real absorption and even bulk charge is more along the line of 'cram it in as fast as possible and only reduce current towards the very last end stages'.
I would want bulk charge to be the highest alternator output current possible with a belt manager setting possibility and a alternator temperature cutback. I have not yet achieved this state with my settings (but then the lead acid battery causes problems with that so I have to wait until I am totally lithium)
So yes, some of the settings are similar to the mc-614 but there is enough difference to make a dedicated controller worthwhile IMHO....
Really looking forward to those parameters though !
AFAIK there is no such thing as a dedicated Lithium alternator regulator, but the MC614 can do pretty well.
Charging LiFePO4 batteries is both easier and harder than lead acid.
Easier because Lithiums do not need a lot of the charging regime voodoo which has been developed to address lead acid behavior. As described in the long LiFePo4 thread, for LiFePO4 set the absorption voltage to 13.8 or 13.9 V and float to 13.3 or even 13.2 V and you are good to go.
For "charging speed" it really does not matter if you set it to 13.9 V or any higher value, the charging current will max out in both cases for a half empty battery. The only difference with different voltages is that you will reach much higher (unnecessarily high) in the "top charge knee". You want to avoid that, hence 13.8/13.9 V.
No need for special chargers, just set the thresholds to these values and you are good. On the MC614 you can reduce maximum field excitation (belt manager), and you should do that (read Maine Sails
article). Using a temperature sensor on the alternator is a good idea as well.
Voltage difference between resting voltage and charging voltage in combination with the total resistance of wiring
and batteries will determine the maximum current that will flow during charging. Typically the current will be limited by charge sources capacity, not by the batteries and wiring
Effectively this means that a dedicated "bulk" stage is meaningless for Lithium. They are literally in bulk mode all the time. Bulk for lead acid means the charger
ramps up charging voltage to overcome internal resistance in order to max out charging current (that's the constant current phase of the charger). It's not applicable for LiFePO4 because they are already accepting max current at absorption voltage without the need to raise it further (nor would it be possible, voltage simply collapses to pack voltage plus a few fractions of a volt, just enough according to Ohm's law to allow maximum charging current the charging source can deliver).
Because of the extremely low internal resistance the batteries pretty much short your charging source - which makes charging harder than lead acid. When designing your system you will have to make sure that all your charging sources can withstand delivering maximum current continuously.
Finally, connecting LiFePO4 and lead acid to the same charge regulator (even separated by the battery isolator) is not a good idea. You will either undercharge the lead acid battery or overcharge the Lithium bank. Both is not good.
I suggest rip out the battery isolator, attach the alternator regulator and alternator only to the Lithium bank and configure it for LiFePo4 values. Get a DC-DC charger
(e. g. a Balmar
Digital Duo) and charge the lead acid bank via the DC-DC charger from the Lithium bank.
Cleanest solution, and not that expensive.