Have no idea of lithium brands. How many ah battery/ batteries? If your dc-dc charger is like my 25a it does the 25a with the motor running. Recommend a battery monitor if you ain't already got one

300 ah bank isn't daunting to charge , I guess your Orion is a 12/12 30 ? In that case it can charge 30amps so every hour that's 30ah, in 10 hrs that's 300ah. No solar or wind input ?

Three and a half years ago I purchased an Australian made ATLAS 135AH 12V Lithium Deep Cycle Battery from Aussie Batteries online for $670. I use it as the house battery. I use very little power on my boat so haven't really put it under much load. In fact, I temporarily hooked it up to a 10W trickle charging solar panel but have never got around to installing the larger panels I bought which shows how little power I use. Aussie Batteries don't have it on their website now, they have Giant Brand. I see that Aussie Batteries currently have them on sale. 120Ah for $400.

The one thing to keep in mind is the battery comes to you only half charged and you need to fully charge it before using it. I wanted a decent high quality charger anyway so I ended up buying a Victron Energy Blue Smart IP65 SLA/LiFePO4 Charger 12V 25A + but that set me back another $350.

If I was a cruising sailer, and not just a day sailer, I would definitely consider a DC to DC charger as backup to solar. I am a firm believer in keeping the house and starter batteries completely separate otherwise. Out of ignorance of the alternatives I trust Victron. I use their MTTP controllers.

If you want to shop around, I bought 4 big Lithium batteries from here over last 5 years. Two for boat and two for home. They were good price and still going fine.
www.4wdsupacentre.com.au/
And 3 x Renogy MPPT chargers from here. Also good price and going fine ebay.us/m/Jcksy1
I chose both suppliers because they have good reviews and been in business years. (Renogy reseller 211,000 sales and 99.4% positive feed back!)

I've 2 x B-TEC LiFeP04 12v 300Ah G2 Lithium house batteries installed October 2022. No issues with them whatsoever, so far. They're rated for 2500+ cycles, and on current usage won't get to that for many years to come. Still using a 110AH AGM lead acid for starter battery.

I have no expertise, so if I was replacing the lithiums, I'd either go same again, or the IP67 version, based on performance of the current ones or Victron, based on reputation.

I went with invicta batteries, from springers there really good to chat to for advice etc, comes with 5 year warranty and any problems you can take it back, they sell victron and enerdrive as well but recommended invicta for halve the price, I've had renogy in last boat but had problems and there service department was **** and useless and was a nightmare to send it back for warranty