I have a slightly unusual marine system. The primary system is quite standard with a starter battery for the pair of engines and two house batteries to run lights, pumps, radar, instruments, etc. These batteries have a shore-powered charger 3 x 10 amps. My shore power plug is 30 amp capacity.
I have an isolated pair of lithium batteries that run the 12v cabin AC, hot water heater, cabin lights, and shower pump. These lithium batteries are charged by solar panels on the cockpit roof. This system worked very well until I added a cover to my boat lift. The charging rate on the lift is greatly reduced.
I wonder if adding a DC to DC charger that would recharge the lithiums from the house batteries would solve this conundrum. As I understand DC to DC chargers, there is no transfer of power until the source batteries are fully charged. Is that correct?
Are you wanting to charge the lithium bank while you’re hooked up to shore power, when you’re disconnected from shore power, or both?
I assume you want this to be able to charge while on shore power or with alternator power if you’re looking at a dc-dc charger
This is exactly what they’re designed for!
The smaller chargers are somewhat limited in features, the 50a is probably a little overkill but has a lot more flexibility
Either way you shouldn’t have an issue setting it up to kick on once the engine is running or the shore power chargers have kicked in.
Thanks for the replies. Yes, charging when on shore power or underway.
I willl look at the 50a version. The 18a doesn’t connect to Cerbo that I can see.
How does the charger know when the engine is running?
One of 2 ways, you can connect to the engine ignition wire or you can set the voltage trigger so it only activates when the starter battery is above a certain voltage, i.e. being charged. The manual has the details.
The charging process is not working very well when on shore power. The Orion Tr cycles on the bulk charge when the main house battery is above the threshold set (13v). The shore power charger is a Noco 5 x 2. As soon as the Orion switches to bulk, the main house battery drops to 12.8v and the Orion switches off. Secondarily my Smart Shunt has disappeared for the system. Shouldn’t it be showing a charge?
That’s to be expected if your shore power charger is sized greatly under the dc-dc charger. I’d suggest a larger shore power charger or lowering the dc-dc charge current if you’ve got an Orion xs
My drawing skills are poor. I have tried to sketch out the 12v side of my marine system. My Shunt VE.Can showed on my Cerbo GX device list and show current into and out of the second house battery set. It has now disappeared.
Whiskey Days - 12v wiring.pdf (27.0 KB)
My main lithium house battery shows 14.1 volts on a voltmeter, yet the Orion Tr only sees 13.2 volts. The Noco 5x2 charger is undersized but is really only a battery maintainer. The boat should return from a trip with batteries fully charged as each outboard has a 70 amp alternator.
I would check all your connections and grab a multimeter and figure out why you’ve got a 1v drop between the charger and battery, that’s definitely not good and possibly the shunt is involved here
I put an external charger on the secondary house batteries and brought them up to full charge. The voltage is holder at 13.3 for all house batteries with the NoCo charger. I think the NoCo was set on AGM and overcharged the primary house battery. I have doubled checked everything now.
However, the Shunt VE.Can is still MIA. This occurred when I connected the secondary house system through the Orion Tr to the primary system. I am using a non-isolated Orion (probably a newbie error). I will run a negative wire (6AWG) from the primary house system to the secondary house system to see if this makes a difference.
Whiskey Days - 12v wiring.pdf (27.0 KB)
Double check the comms cables, these are easily disturbed when doing work. Removev and reseat them and make sure they are pulled back against the clip. My battery monitor went MIA due to this and there are other cases on here.
OK. The VE.Can connection is basically a RJ6e network cable. I pulled and inserted both end and reinserted the terminator plug.
The power light is on and green.