A customer with a sailing yacht wants to convert his domestic battery bank (2 x 85ah lead flooded) to AGM. They currently have a lead-acid start battery, which they wish to keep.
The alternator is a 115ah unit, which is regulated by a Penta D1-30 engine with an MDI unit.
They also require a new mains charger.
We are also installing a BMV-712 (Smart) to the house batteries.
There is a small <50w solar panel.
Our thoughts were to:
Install a 25a IP67 mains charger directly to the engine battery.
Install an Orion XS 50a unit between the engine and house batteries. The 115a alternator should cope with it well.
Connect the solar panel to the engine battery
This will ensure that the starter battery is always charged first and does not cause issues with the smart MDI unit fitted to the engine, which senses battery voltage, etc. Once the engine battery reaches its charge, the Orion will begin to charge the AGM bank.
My concern is that while the 115a alternator should cope with the Orion XS 50 (less than 50% load), how would the IP67 Charger cope? Would/could it be working flat out and lead to premature failure?
He does not want Lithium at the moment, but possibly in the future.
The Rolls S12-95AGM-RE will each support a charging current of 25a (50a total) which matches the max output from the Orion XS 50.
The XS can also have its Max Current output restricted if needed.
So my main concern is regarding if the AC Mains Charger will be overwhelmed? I.e duration of it running flat-out until the charge current to the AGM’s decrease as they become full.
I’d advise against the IP67 charger, as -like any brand of waterproof charger- they have a much higher failure rate than other products. The IP65 charger is available in a 12/25 and is much more long-term reliable in my own testing.
Day after day, only time could tell, but I did run an IP65 12/25 at full-bore output for 12 hours straight in testing one day and it survived, so that’s promising. If you don’t specifically need the waterproof functionality, an IP22 12/30 or an IP43 12/50 would be better choices.
Also worth noting that if you’re only putting 25A into the engine battery, you won’t be getting 50A out of the Orion XS to your house battery - power out will always be less (though in the case of the XS, only marginally due to its high efficiency) than power in. If you truly want 50A going to your house battery, a 50A or better charger on your engine battery will be required.
Indeed, the trouble is, it will located in a locker… often where rope, etc. might be stored, so I thought the IP67 sealed unit would be a better option for a potentially moist atmosphere. I did consider the IP22 12/30. Though I could extend the mains cabling and move it, and then reduce the charger to battery distance and cable diameter.
25a in/out while on the mains isn’t too much of an issue; it will still charge all the banks overnight. It comes into its own at 50a when the 115a alternator is running, and it needs a faster recharge at anchor or between stops.
I did consider the IP43-rated Phoenix 12/30 or 12/50, but it will blow the budget (it’s almost double).
I’d call the IP65 12/25 a pretty solid choice for that then - it’s still totally sealed against casual intrusion, just not a fully-potted brick like the IP67. And, though obviously it depends on your local market conditions, I believe the IP65 12/25 will tend to be only marginally more expensive than the IP67 12/25
I agree with both points raised but offer more information :
The maximum output of Orion XS can be set to less than 50A. I use one in my 4x4 to charge a 105Ah AGM. The highest charge current I’ve seen is around 15A and my XS is set up to deliver 25A max. You can argue that the XS’s full capacity is wasted in my case but I chose it for three reasons; a) it is more efficient and runs cooler than other Orion DCDC chargers, b) it is much smaller than other DCDC chargers and fits better in the space I have and c) I plan to upgrade to a LiFePo4 battery in future.
For the original poster’s case, choosing an Orion XS would set him up well for a future upgrade to lithium batteries.
For my vehicle application the starter battery is in the engine bay which gets too hot for a lithium battery, so I will always use a lead acid starter battery. Probably not an issue in a yacht but be aware of the temperatures wherever your starter battery is located. If upgrading to a lithium based starter battery, make sure to get one that can supply a bit more than the cranking amperage needed by your marine diesel.
Once the alternator is turning, the DC-DC charger may see the alternator voltage, not the battery voltage. This is a bit of a fuzzy statement on my part, the point is that the starter battery is going to get charged, but the house battery bank will probably begin to get charged before you might consider the starter battery “fully charged.”
The Orion XS is very configurable, so you can set a fairly high input voltage threshold so the starter battery will reach a higher state of charge before the house battery bank begins charging. As stated in prior posts, you can also configure the input and output amps. Since you have a relatively small alternator you can limit the Orion XS’ input current to 25 amps and then check to make sure the alternator isn’t overloaded or overheated.
I use an Orion XS to charge a small 12 volt LiFePO4 battery on the tongue of my trailer from my 48 volt house battery. The configuration of the Orion XS is set to keep the small LiFePO4 charged without draining the house battery should there be an absence of sun for more than a few days.