Question (series) one:
My
boat (a Freedom 33) has two
batteries: a 48v 300ah
battery for the
electric motor & a 12v 200ah
battery for... everything else. Right now, these are two separate systems. I'd like one battery to be able to charge the other (or, ideally, for them to be able to charge each other). I'd like some input on what device is best for the task.
My understanding is that a DC-DC converter won't be right for this task, as it won't be appropriate for regularly
charging batteries. A device intended to charge batteries will be needed.
Victron: as far as I can tell, has no DC-DC chargers that
work for 48v & 12v. Does have a converter (non-smart Orion) for this, but that's to output a stable
current for load, not for battery
charging as I understand it.
Mastervolt: My understanding is that the DC Master series is for DC-DC converting, like the
Victron Orion, but that the Mac Plus series is intended for battery to battery charging. There are two 48v & 12v options (one for each direction):
Mac Plus 12/48-15 and
Mac Plus 48/12-50
My understanding is that the 48/12-50 is intended to primarily output 12v
power, with a 48v
power input (i.e. from the 48v
electric motor battery to the house battery). It costs about $750 USD.
The 12/48-15 is the reverse - it would charge the 48v
electric motor battery from the house bank. It costs the same - about $750 USD.
Both have a bi-directional technology that allow a switch to be wired to reverse the flows, charging in the other direction. Still, I'm assuming I'd want to use that rarely? Or would both
work fairly equally in both directions? (I don't think so... judging by the manual on page 22, which I may not have fully understood.)
Sterling: Their website is... les clear... but they seem to have a few options for DC-DC battery charging from 12v to 48v, but not the other way around.
A few bright red box models, that are advertised as "marine-grade non-waterproof." For example the
BB124865. It seems to be a 12v input, 48v output battery to battery
charger, also with bidirectional technology. Cost: $415 USD. I like that
price, but I'm assuming the lack of a waterproof rating means it is unsuitable for a
sail boat, regardless of being "marine-grade".
There is now a waterproof option from Sterling:
BBW124830. It also costs $415, so about $300 less than the Mastervolts. It outputs about half the amps of the non-waterproof sterling (7.5 amps at 48v vs 15ish above). The Mastervolt 12/48-15 also outputs about 15 amps at 48v. This new Sterling has a much better IP rating: the Mastervolt has IP23, the sterling has IP68. It does NOT have bidirectional technology?
Am I understanding these products correctly (I'm pretty new to electronics)?
Is the non-waterproof Sterling just plain a bad idea on a
boat?
Is the IP23 rating of the Mastervolts good enough on a boat?
Is the bidirectional technology as good & simple as flipping a switch without doing anything else? Or are there limitations/drawbacks that I can't see in the
manuals?
Are there any other brands I don't know about that I should be looking at?
As far as I can tell now, the Sterling waterproof lacks the bidirectional function, which doesn't allow the house bank to use the much bigger 48v battery as a reserve source of power. The Sterling non-waterproof is non-suitable because of a lack of IP rating. The Mastervolts have a low IP rating and are hundreds of dollars more, but still seem best for my use case. (More on that below.)
--------------------------------------
Question number 2:
Currently both batteries can be charged from
shore power & the 48v battery can also be charged via hydro regeneration from the
electric motor (yes, I can get speeds capable of doing this often enough to be useful). I will be adding
solar (probably 2x 400w 40v ouput panels) - but I'm not sure what side I will be adding it on.
If I connect an
MPPT to the 12v house battery then the advantages seem to be: more consistent charging (even with some shading should output at a high enough charging voltage more often than for the 48v battery), the option to wire the
panels in parallel, more efficient use of that
solar power (no loss for house use from going through the Battery-to-Battery charger). The (very big) disadvantage is that I can't use the 48v battery as extra power for house uses at night, unless the bidirectional technology works as well as just flipping a switch connected to a Mastervolt Mac Plus.
If I connect an
MPPT to the 48v motor battery & set up the battery-to-battery
charger to primarily move power from the 48v batter to the 12v battery then the advantages seem to be: the Battery-to-Battery charger is well set up to effectively increase the
electrical power I have available to house functions dramatically & there's no inefficiency in pumping solar into the big 48v battery when the sun shines brightly. Also, I have a lot less need for bidirectional ability (but I still have to get an expensive Mastervolt). The downside is lower overall efficiency (solar to 12v goes through whatever losses the Battery-to-Battery charger introduces) - and all the other advantages listed in the previous paragraph become downsides as well.
Which battery would you recommend connecting the solar panels/MPPT to?
-----------------------------------------------
Question 3:
Currently I'm thinking I'll have to pony up the $$ for the Mastervolt 12/48-15 Mac Plus & hook up the solar to the 12v battery, hoping that the bidirectional function works well & I can flip a switch at night to allow the 12v battery to draw on the larger reserve of power from the 48v battery.
Edit: OR to hook up the
solar panels to the 48v battery, again pony up the
money for the other Mastervolt, assume I won't be using the bidirectional technology, and accept the less efficient solar to 48v charging and house use of Solar-> MPPT48v -> BBcharger -> 12v battery.
Edit: The safest option, which I'm not considering all that much sans
advice, is to get the waterproof sterling so extra solar can charge the motor batter & give up on using the motor battery as reserve house power.
Does that thinking make sense & do any of you have experience with the Mastervolt Mac Pluses, especially if the IP 23 rating is good enough or with the bidirectional technology?
Linear Mode
Recent Discussions