Powerbank - does this make sense?

[cliffm]

Has anyone found a sufficiently robust power bank to trust near salt water? The Bluetti AC240 (Pioneer 150) is IP65 rated, but is 72lbs and rather large! I'd like something I could store outside the cabin, either in the cabinet below the icebox on my Cutwater 28 or below that cabinet's floor where the generator usually goes. The AC60 is also IP65, but with only a 600W inverter it has limited options to operate as an anchored shore power solution and operate a DC fridge/freezer.

In salt environments have people gotten away with a power station with simple covers on the AC and other output ports?

We just purchased a Bluetti elite 200v2 as it is a compact size and 2600W, and I believe will fit under the cockpit shelf/seat when needed as shore power supplement. It's 53lbs

 

[DDean]

Quick update on the Bluetti Elite 200 V2 for those interested in this new unit. We went out with it for the first time last weekend.

It fits perfectly under the corner cockpit seat.

I ran the grill by connecting the boat to the Bluetti and powering the boat via Shorepower. The most the grill could get out of it was 1250watts using a 5-15 nema to shorepower. Seems like 10Amps to me and definitely well below full grill power (1800w). I was able to pull 15Amps for other devices so I’m not sure what’s happening with the grill - perhaps the next increment up in power exceeded 15A? Next time I’ll plug the grill directly into the Bluetti and see if it’s different, to eliminate the boat from the equation. Took awhile to cook dinner!

Charging the Bluetti via the Bluetti car DC cigarette lighter plugged into the cave was at 105w at 13V and didn’t appear impacted by engine RPM, probably because it’s coming off the house bank. It was the same with the engine off. It will take forever to charge the Bluetti at that rate - it’s helpful but we will have to find a more direct solar strategy to charge the Bluetti on the boat if we need that.

I can’t find a 5-20p to L5-30r cord longer than 2feet in Canada, or that will ship to Canada. I probably need that to pull 20Amps. I’m using our full stock shorepower cord plus 15amp connector for now. Want to solve this.

Charging the boat back up to 100% via the Bluetti was fast - I think it charged up at 15A and we were back at 100% before we knew it. It struck me that charging via shorepower avoids the super slow trickle for the top 20% capacity the alternator provides, and one could use even a small power bank to top up that extra 20% while out - for those of us with AGMs that top 20% takes a long time to recharge via motoring and it’s roughly 40% of our usable power in an R27NW. Maybe there’s a combination strategy of using the engine alternator to charge up to 80% and a smaller power bank for the remainder.

I’m increasing our boat solar to around 400W with a Victron 100/30 soon. I suspect that much of the time that will keep the boat at net neutral power each day and the Bluetti will became a means to the grill and coffee and perhaps warm water (hot water would drain it), and to store excess solar when the house is already at 100%. I might be able to keep the Bluetti charged up via the house bank using that 100w cigarette if it’s in there all the time.

But I wish that there was a solar controller with switchable outputs - one to charge the house bank and one that I could hook into the Bluetti when I want to do that. Going through the 100w cigarette port is wasteful wHen the house bank is at 100% and solar is pumping it out.

 

[Pandion]

But I wish that there was a solar controller with switchable outputs - one to charge the house bank and one that I could hook into the Bluetti when I want to do that. Going through the 100w cigarette port is wasteful wHen the house bank is at 100% and solar is pumping it out.

I'm not all that familiar with Bluetti, but I think that the unit contains a solar controller and is designed to take direct input from solar panels via MC4 connectors.

If you're going to update your solar to 400W, have you considered installing a two-way switch between your panel(s) and your solar controller? That would allow you to feed your solar panel output to your solar controller to charge your AGM house bank or to route the solar panel output directly to your Bluetti (assuming it will accept that much input). It's not a "hands off" solution but would accomplish your goal.

Another option could be to use a DC-DC charger such as a Victron XS (which can bypass the charging profile and be run as a constant voltage power supply) between your AGM battery and your Bluetti. Not quite as efficient but those units are highly configurable and could be programmed to mimic a solar panel output through the MC4 connectors.

 

[DDean]

That’s a great idea thank you. It might be a bit above my pay grade to install such a thing but I’m going to look into it as you are exactly right, these power banks have controllers built in. Mine uses an XT60 input

 

[DDean]

UPDATE:
Picked up a Victron 100/30 controller and a JA Solar Deep Blue 440W panel. Both are now installed. Only one real day of testing but that panel put 1000wh into the house (R27OB NW) mid sept on a semi cloudy day. The house was back in float mode (fully charged) around noon and stayed at 100% until the sun went down. The panel was putting out 230ish watts under very suboptimal conditions. I acknowledge that the house was not very depleted, but if its charging it up by noon it will be able to charge from almost fully depleted (of the usable 100AH) before the sun goes down, and then we are back at 100% when the dark hits. We typically are down to about 85% from 100% overnight. Its a 37v panel so current from the panel to the controller should be fine even if its pumping out the watts. Ive limited the current from the controller to the bank to 27Amps so it doesnt trip the 30AMP fuse.

The Bluetti is probably now delegated for coffee and when we want power on the dock for dinghy pumps etc. Im going to leave it plugged into 12V to charge it up during the day to keep it full instead of all that glorious sunshine be wasted when the house is already full. It will be good back up as well. It runs the grill OK if I wanted to use the power for that (I dont find that the grill cooks meat very well as the food is not covered, much prefer the stove)

I mounted the panel with Gemini clamps - AWESOME - and I installed MC4 connectors on the roof as well as on the stock panel (which was 190W not the 175W the boat was supposed to come with BTW). I can move panels around as I want now.

WHICH BRINGS ME TO A NEW QUESTION:

My Bluetti is 170AH at 12V but my guess is that if I use it to charge the boat through shorepower, that I will be doing so at 120V, which reduces the Bluetti to sub 20AH - which sucks! Does it matter? Does the charger then convert it back to 12V so its all a wash or does it take a massive hit during the conversions?

Im hoping not to need the Bluetti to charge the boat BUT how do I charge the boat with the Bluetti more efficiently than via shorepower?

 

[Submariner]

WHICH BRINGS ME TO A NEW QUESTION:

My Bluetti is 170AH at 12V but my guess is that if I use it to charge the boat through shorepower, that I will be doing so at 120V, which reduces the Bluetti to sub 20AH - which sucks! Does it matter? Does the charger then convert it back to 12V so its all a wash or does it take a massive hit during the conversions?

Im hoping not to need the Bluetti to charge the boat BUT how do I charge the boat with the Bluetti more efficiently than via shorepower?

170 amp-hours * 12 volts = 2,040 watt-hours.
2,040 watt hours / 120 volts = 17 amp-hours.

It's two ways of saying the same thing, depending on the voltage.

Consider the inverter. Its purpose is to convert 12 volts DC to 120 volts AC.
The water heater draws 750 watts. Assume I run it for an hour. I'll consume 750 watt-hours. At 12 volts, 750/12 =62.5 amp-hours. At 120 volts, 750/120=6.25 amp-hours.
Personally, I don't find it very useful to think of 120volt AC on my boat in amp-hours. I do the above conversions a lot to 12 volt, since the 12 volt DC electrical system is the house battery bank, and the shunt keeps track of consumed amp-hours (at 12 volts DC).

The battery charger does the inverse. It converts 120volts AC to 12 volts DC.

I have a Kisae 60 amp battery charger. The "60 amp" is based on the 12 volt side of the battery charger. Wattage is specified at 1,050 watts.
1,050 watts / 14.4 volts = 73 amps. On the battery monitor, I will see 73 amps or less at 12 volts going into the battery.
1,050 watts / 120volts = 9 amps. So on the amp meter needle on the AC panel, I will see around 9 amps.

The Bluetti has its own inverter that's providing the 120volts AC power which you plug into the boat's shore power connector.
The spec sheet on a 2000 watt-hour Bluetti battery states 40 amp-hours. That tells me the battery they're using is 50 volts DC.

This all gets confusing because AC (alternating current) can't be stored. Electricity can only be stored in a battery operating at DC (direct current). 12 volt, 24 volt, 48, 56 volts... all DC.
An inverter gives us 120volt AC from a battery at DC.

Ohms Law: Voltage = Current * Resistance. The resistance is constant (it's in the wires throughout the boat). So as voltage goes up, amperage will go down. They are proportional to each other. As amperage goes up, it'll generate heat (from the resistance). Heat is lost power. So electrical is a balancing act. We want amp's to be low, to keep heat down, and not have a lot of lost power caused by resistance.

The USB outlets on the boat that we charge our phones with, they're 5 volts DC, by the way. 🙂

This is a great discussion, by the way. I'm currently working on a video for our YouTube channel "Electrical Overview for the R27-OB LE with LFP."

 

[DDean]

Thanks always @Submariner.

That’s what I hoped but I was worried that there might be a step down at the battery charger because efficiently capturing shore power might not be nearly as important as from a power bank!

I’m glad it’s a wash!

And you’re right, 400W up top does seem like a game changer, already.