Yes you are understanding me correctly. Once you introduce a lithium battery into your system whether it’s the start or house battery, the DVSR power source ( red wire in the back) needs to be off while at rest / floating or the DVSR will close the switch paralleling your house and start batteries. The 100% charged resting voltage of my battle born batteries is 13.6 volts, the DVSR will close the switch if it sees 13.2 volts on either the start or house battery. Currently (see what I did there?) I have mine connected to a rocker switch on the dash, I wait until the start battery voltage is above the house battery voltage before I power up the DVSR, usually a few minutes after starting. This assures that the LiFePO battery does start trying to charge the AGM battery…and all charging current is going into the start and the house battery.
You do not need to make any changes to the oem charging system. We have PMG (permanent magnet generator) type of charging system, which means our charging systems are always at full output. The rectifier / regulator changes the 3 phase AC voltage from the generator to DC via diodes, then the regulator shunts excess DC voltage / current to ground to “regulate” charging voltage and current. This type of system is well suited to maximum charging / output since it’s always at full output.
An automotive style alternator on the other hand varies the “magnet” if you will to regulate the voltage / current coming out of the alternator, and the diodes convert the AC to DC voltage / current. The advantage to this type of alternator is much greater output as the magnetic field (flux density) can be greatly increased as opposed to a PMG type whos flux density is fixed. The disadvantage to this type of system is that it needs voltage to supply the field, as opposed to a PMG type that will always generate as it always has its field. The automotive type of alternator is not at full output all the time, most of these types of alternators will not with stand full output for an extended period of time and will fail. When I talked to Yamaha about the switch to lithium batteries the tech told me about their outboards having alternator failures with the early lithium batteries for this reason. Lithium batteries have very little internal resistance when compared to lead acid batteries, this is why they charge so much faster than lead acid batteries. This resistance is why you typically see an automotive alternator start backing off on its charging rate when its charging a lead acid battery even though there is a long ways to go to charge to full, with a lithium battery the charge rate will remain high until the battery is almost charged. The newer lithium batteries BMS and internal design has taken care of most of this by limiting charge current. This is why it’s so important to do your research on lithium batteries….thanks
@mrcleanr6
You do not need a DC to DC charger, and according to MinnKota their DC to DC charger will not work with our boats as there is not enough charging current. I was looking at this as a way to put some charge into my trolling motor batteries. That’s a whole other story.
Dakota lithium recently came out with a group 24 size 135 Ah start / deep cycle battery which may lend a drop in solution for your desire to change out both your start and house batteries. I watched a very good side by side test of the battle born batteries, AGM and flooded lead acid batteries. In this test it was noted that lead acid batteries are very good at dumping large amounts of current over short periods of time and that makes them better for starting batteries. I ended up putting an Interstate AGM start battery with the Battle Born 100Ah house battery.
It looks like you may have read my linked thread on converting to LiFePO batteries…it was quite a journey. I will say based on my research the only LiFePO batteries I would recommend to anyone is either ReLion or Battle Born, with my best recommendation being Battle Born. I know I mentioned Dakota lithium above, some folks have used them with no dramas, but it was my experience that I could never talk to a tech or get timely responses to my questions, if the only person I can talk to is sales then I’m not going to deal with them, Dakota lithium also misrepresented themselves, they elude to being in Gran Rapids North Dakota, try and find them there.
Sorry I took a bit to answer your questions I just stumbled across your post this morning. Hope I answered your questions. Feel free to ask any others you may have.
