BFL13 wrote:
otrfun wrote:
Finally got around to looking at the lithium charge options on our Renogy 40a dc to dc charger we have mounted in our truck camper. Bad news, the lithium mode is single-stage just like the PD, no float. However, the good news, in lithium mode you have 7 voltages to select from: 12.6v, 12.8v, 13.0v, 14.0v, 14.2v, 14.4v, and 14.6v. In lead acid/AGM/GEL mode it becomes a 2-stage charger (absorption and float). 3 absorptions choices: 14.1v, 14.4v or 14.7v. 3 float choices: 13.2v, 13.5v, and 13.8v.
Interesting that both Renogy and Progressive Dynamic (and no-doubt others) use single-stage lithium chargers. Got to wonder whether these manufacturers saw no harm in floating a LifePo4 indefinitely at higher voltages (let the BMS do the dirty work??), or they just assumed the end-user would simply disconnect/turn-off the charger for long-term storage (based on LifePo4's very low parasitics).
BB says you can leave it at 14.x for a week or two. Your DC-DC shuts off when you shut off the ignition, so no need for a float option. A converter stays on for as long as you are plugged in.
DC-DC is buck/boost so maintains 14.x whether alternator regulation has it above or below the chosen 14.x.
Yes, in an *typical* alternator application I agree there's very little to worry about. However, that's making an assumption on how the dc to dc charger will be used. It may or may not be turned off after a period of time depending on application. Bottom line, Renogy or PD did not qualify or restrict the use of the lithium mode in their dc to dc charger or converter in their user's manual.
Renogy and PD offer 2-3 stage charging (with float) for lead acid/AGM/GEL. The question is *why* not a float for lithium? I honestly believe they left out this option on purpose, for what they felt was a good technical reason to do so. It wouldn't have cost them a penny more to have simply added a float for lithium if they felt the need existed. Definitely more to this story than they simply forgot. Curious minds want to know why--lol!
