I have an epoch 12V 172AH dual rated lifepo4 battery.
I want to change out our lead acid house battery in our boat to lithium, but still leave the starter battery lead acid.
I want the motor to charge the lifepo4 battery and starter while underway. (alternator on)
Right now it is two lead acid on a dual circuit ON/OFF/COMBINE switch, with an ACR that combines them when the motor is charging..
With the lifepo4 as the house, I would need a DCDC charger and to change things up and get rid of the ACR.
Can anyone look at my diagram here and see if anything looks off? Thanks!
NOTE: The 300A fuse on the starter battery is much larger than the cable, but is just for dead short protection. Same with the house 300A fuse, since it could be used to start the motor if the switch was in âcombineâ mode. As far as I know a starter battery on a boat doesnât even need a fuse, itâs more just an incase thing for a dead short.
Get yourself a fuse on the âinâ side and you are good to go.
Why do you want to limit the draw of the Orion? You can use the settings in the Orion to disconnect when the starting battery gets to a specified voltage to keep it from discharging.
Just scared it would somehow steal all the amps from the motor altenator and starve the starter battery (shrug). While underway I would want the starter motor to make sure itâs getting charged back up. We do a lot of âhoppingâ from place to place in the galveston bay. Maybe I am overthinking it.
Unless your starting battery is on the decline, starting then engine shouldnât require a lot of recharging. The Orion is a converter and will only use what is provided to it.
There are some great features within the Orion that will solve your concern. Engine shut down detection can be set to only turn the Orion on when the starting battery reaches your specified voltage. Assuming your starting battery resting voltage is around 12.9V you can set the Orion to only connect when the input voltage reaches 14.00V and disconnect when it reaches 13.2V. There is also input voltage lockout setting that is usually set at around 12.5V. If for some reason your starting battery is draining the Orion will disconnect from it at the set voltage.
And if all that doesnât work a simple switch between H and L terminals or V+ signal on H can be set up to force the Orion on and off.
The motor is on. outputting 14.4V. Its sending power back to the starter battery AND the orion XS.
Let say the altenator puts out 20 amps max.. Would 10 amps go to the starter battery and 10 to the Orion XS?
Or could the orion pull 19.9 amps because of less resistance to the lifepo4 and only .1 go to the starter batter (lead acid)
Again this is while the motor is on and outputting 14.4 volts (so engine shutdown setting wouldnât really matter).
Iâm not necessarily wanting to prioritize the power going to the starter battery, just wanting to make sure it gets evenly distributed.
Even if the starter battery is pretty drained, when the motor is on it would be outputting 14.4V and thats what the orion would see right?
I see your concern. Hereâs my understanding and I will try to limit it to what I actually know. The charging voltage will be conditional on the resistance within the battery. If the battery is low the charging voltage will be low and climb as the battery reaches capacity. If your starting battery is low it will have lower resistance and receive a charge accordingly. The alternator will not just blast out 14.4V. It will start at the voltage the battery requires and build as the battery reaches capacity. Like many things in physics the current will take the path of least resistance. It may be better, with this in mind, to wire the input of the Orion directly to the battery positive. It will take someone with more technical knowledge to explain why but the Orion works with this and will not just let the starting battery starve. And we have reached the limit of my knowledge.
Perhaps a better solution than limiting the draw of the Orion would be to put a switch on it as I mentioned above. In any situation you notice the starting batteries need all the alternators attention you can just hit the button and not worry about it. Then when you are confident your battery is topped off flip the switch and charge you house batteries at the full available amperage.
Hey, @pwfarnell. Want to chime in here? You seem to have a ton of experience with boat electrical.
@silicondt you need to read the manual, engine shutdown detection section.
you set the engine shutdown voltage at something like 13.4V, above the 12.8V fully charged voltage. The Orion starts to charge the house battery when the starter battery exceeds 13.4V, which means the starter battery is charging. If the Orion starts taking more current than the alternator can deliver then the starter battery voltage will fall and if it approaches the 13.4V shutdown setting the Orion auto regulates the current to stop the voltage falling below 13.4V, so the starter battery would still be charged and the starter circuit loads supplied.
My 2 cents worth and experience on these systems. Youâre on the right track moving away from the ACR.
ACRs donât behave well with LiFePOâ´ due to the flat voltage curve, so they can become unreliable or âhuntâ under light alternator load. A DC-DC charger is the correct solution here.
Also worth noting the DC-DC isnât just about charging profile it actively limits alternator load, which is the real protection point for both alternator and wiring when lithium can pull high current for long periods.
On the fuse side, be careful with âjust for dead shortâ thinking. Fuses should be sized to protect the cable, not just act as generic fault protection.
Overall, remove ACR, install appropriately sized DC-DC, and ensure cable/fuse sizing is done from conductor rating rather than assumed system current.
âOn the fuse side, be careful with âjust for dead shortâ thinking. Fuses should be sized to protect the cable, not just act as generic fault protection.â
This is just my understanding from reading as much as I could on the subject with boats and starter battery.
ABYC code requires no fuse on a starting battery for a boat. So the 300A fuse isnât even required, its just for dead short protection really.
The 300 amp is more to never have it pop when trying to start the outboard, but it would if I ever dead shorted it for whatever reason.
Everything else I do - yes fuse rated to wire being used.
Thanks for chiming in.