Lithium AGM parallel questions?

[bloodman]

For you believers in paralleling the AGM starter/house with a lithium battery. Would you just parallel directly so both batteries are cranking the engine and feeding house loads OR would you add the lithium for just the house loads and connect the two batteries together just for charging the lithium from the motor via an acr or combiner type device?

I would have in parallel through a battery 1, 1+2, 2, off switch. Have isolator or combiner provide charge to both while running and separate chargers.
Have them in parallel, position 1+2, while running and off at home.
Even though mine are running parallel, all power comes out of the lithium due to voltage differences. The AGM stays at full charge. The only time I would yse any power from the AGM is when the lithium battery drops to 12.8 volts.
The AGM is only acting as a buffer in this system.

[chrisgatti]

I would have in parallel through a battery 1, 1+2, 2, off switch. Have isolator or combiner provide charge to both while running and separate chargers.
Have them in parallel, position 1+2, while running and off at home.
Even though mine are running parallel, all power comes out of the lithium due to voltage differences. The AGM stays at full charge. The only time I would yse any power from the AGM is when the lithium battery drops to 12.8 volts.
The AGM is only acting as a buffer in this system.

what does your voltage drop to when starting the motor? Wouldn't some juice come from the AGM during starts? OR are you using a high CCA type lithium? I plan on using a small deep cycle only lithium for my electronics, so feel like I need to isolate it during motor starts, and if I depend on a manual switch to do so, am probably asking for trouble.

[bloodman]

what does your voltage drop to when starting the motor? Wouldn't some juice come from the AGM during starts? OR are you using a high CCA type lithium? I plan on using a small deep cycle only lithium for my electronics, so feel like I need to isolate it during motor starts, and if I depend on a manual switch to do so, am probably asking for trouble.

The problem is there is no way of knowing what the AGM is doing. I suppose you could put a shunt on it to find out but I haven't.
Small lithium would have no part in my system. I run a Ionic 125 and at times, think I might need more. I would not parallel a non starting lithium in the system.
If you do plan on a non starter then have them separate. Jmo

[chrisgatti]

The problem is there is no way of knowing what the AGM is doing. I suppose you could put a shunt on it to find out but I haven't.
Small lithium would have no part in my system. I run a Ionic 125 and at times, think I might need more. I would not parallel a non starting lithium in the system.
If you do plan on a non starter then have them separate. Jmo

Yea that was my thought as well. That is why I plan on connecting them through the blue sea ACR with the start interuption circuit so the small lithium won't see the outboard when the outboard is starting.

[H-D Dad]

I have agm and lithium since 2020. I prefer battery switches the combinations of how I use each battery is endless. They play very well together

[bloodman]

I have agm and lithium since 2020. I prefer battery switches the combinations of how I use each battery is endless. They play very well together

Yup...the problem is that the AGM does nothing other than being a buffer for your big motor. It also will assist when temps are below freezing with a charge receiver.
Little did I know about batteries until lithium bluetooth came around. Only then did I realize how bad lead acid is.

[yam911]

The problem is there is no way of knowing what the AGM is doing. I suppose you could put a shunt on it to find out but I haven't.
Small lithium would have no part in my system. I run a Ionic 125 and at times, think I might need more. I would not parallel a non starting lithium in the system.
If you do plan on a non starter then have them separate. Jmo

Digital ammeters on each battery would give an indication of what they are doing and when.