> the reason for that is the voltage differences between how to charge the lithium and the alternator on the outboard are very, very different A couple thoughts 1. the voltage output of most marine and automotive alternators is in the ballpark of what drop-in LiFePO4 batteries want for charging. 2. even if the alternator voltage were inappropriate the UTV-SBI-19L couldn't do anything about that. It is a *voltage sensing relay* that, when connected/closed, passes current at alternator voltage to the aux battery. There is no electrical difference at that point between a relay and a pair of jumper cables -- the two batteries are directly paralleled. Adjusting the charging voltage up/down would require a DC-DC charger. Adjusting it down slightly could be done with a diode-based isolator. > This little device really makes a world of difference out on the water! I'm sure it does, as would any other relay.
Great response! You are correct I should have been more clear in what I was trying to accomplish which was to charge the lithium battery off the starter battery. It's my understanding that a lithium specific isolator is needed for this setup to charge the aux battery at the correct voltage however you're correct it's not modifying the alternator's voltage.
@@mvboutdoors Thank you for the thoughtful reply. With this kind of device the "lithium specific" part is a higher voltage setpoint for disconnecting the batteries *after charging stops* . A traditional VSR might disconnect at ≤12.9v, since that is slightly above resting voltage for a lead-chemistry battery. (When it sees ≤12.9v it knows charging must have stopped and the batts should be disconnected from each other) But LiFePO4 rests at higher voltage so the voltage at which we disconnect needs to be higher or the batteries will get "stuck" together when charging has stopped. In effect the lithium batt would prop up the lead starter batt at >12.9v for a long, long time. So this device disconnects them when it sees ≤13.2v instead. That's a reasonable default that should disconnect appropriately. Carry on, good sir! I've enjoyed the conversation.
@@fratermus5502 Appreciate that explanation and its spot-on -- The voltage cutoff is about 13.2v when the isolator disconnects. Your explanation was very easy to understand! I'm going to pin this post for the great information.
It would depend on how everything is wired up, if you have the two batteries coming off the start battery tied together it should balance the charge so only 1 isolator would be needed.
I had the AGM and Lithium battery wired together so when one charged it also charged the other. The outboard kept everything topped up for the most part though.
> the reason for that is the voltage differences between how to charge the lithium and the alternator on the outboard are very, very different
A couple thoughts
1. the voltage output of most marine and automotive alternators is in the ballpark of what drop-in LiFePO4 batteries want for charging.
2. even if the alternator voltage were inappropriate the UTV-SBI-19L couldn't do anything about that. It is a *voltage sensing relay* that, when connected/closed, passes current at alternator voltage to the aux battery. There is no electrical difference at that point between a relay and a pair of jumper cables -- the two batteries are directly paralleled.
Adjusting the charging voltage up/down would require a DC-DC charger. Adjusting it down slightly could be done with a diode-based isolator.
> This little device really makes a world of difference out on the water!
I'm sure it does, as would any other relay.
Great response! You are correct I should have been more clear in what I was trying to accomplish which was to charge the lithium battery off the starter battery.
It's my understanding that a lithium specific isolator is needed for this setup to charge the aux battery at the correct voltage however you're correct it's not modifying the alternator's voltage.
@@mvboutdoors Thank you for the thoughtful reply. With this kind of device the "lithium specific" part is a higher voltage setpoint for disconnecting the batteries *after charging stops* .
A traditional VSR might disconnect at ≤12.9v, since that is slightly above resting voltage for a lead-chemistry battery. (When it sees ≤12.9v it knows charging must have stopped and the batts should be disconnected from each other)
But LiFePO4 rests at higher voltage so the voltage at which we disconnect needs to be higher or the batteries will get "stuck" together when charging has stopped. In effect the lithium batt would prop up the lead starter batt at >12.9v for a long, long time. So this device disconnects them when it sees ≤13.2v instead. That's a reasonable default that should disconnect appropriately.
Carry on, good sir! I've enjoyed the conversation.
@@fratermus5502 Appreciate that explanation and its spot-on -- The voltage cutoff is about 13.2v when the isolator disconnects. Your explanation was very easy to understand! I'm going to pin this post for the great information.
This little device really makes a world of difference out on the water!
Does the blue light ever go off. I bought the isolator the company recommended for use with alternator and the blue light never goes off
Have you had any issues with the isolator or alternator on you boat?
No issues, it worked out really well!
I'm sorry for asking a dumb question, my apologies, but why did you need two batteries? Did your outboard or trolling motor require 24v?
One is a starting battery for the outboard, the other is an accessory battery for the boat.
Hi any idea which regulator I need for my setup? Battery redodo 50ah outboard Yamaha 15hp.
Battery Isolator - amzn.to/3J55wO3
That's the same lithium battery I'm using
What about if i put 2 batteries do i need to get 2 isolators or how does it work thinking of getting 2 batteries together to prep before season
It would depend on how everything is wired up, if you have the two batteries coming off the start battery tied together it should balance the charge so only 1 isolator would be needed.
Do u ever have the plug in ur AGM battery to charge or does the outboard charge it fully
I had the AGM and Lithium battery wired together so when one charged it also charged the other. The outboard kept everything topped up for the most part though.
Does it matter if the outboard has a stator or an alternator? Will either work?
I would reach out to the manufacturer on that one, I can't say for sure.
@@mvboutdoors Thanks!