What size AC charger for 650 AH of LiFe batteries

[sailbadsinner]

Hi All. So I'm adding 650 Ah of LiFe batteries. (Until I feel motivated to upgrade Balmar LA regulator/ALternator, I'll have a split config with 300 Ah of LA batteries too--I know how to do that.) So my question is how big should my AC charger be for the new 650 AH of new LiFe. The usual rule of thumb is 10-20% of battery bank capacity and there are some 80 Amp LiFe small AC chargers available, which would charge a depleted pack in about 8 hours. But that plus the 40 Amp LA battery charger is going to put me at about 14 ams on my 30 amp 120 V dock circuit just from battery charging. That is less than 50%, but I'm picturing a warm cord and blowing a breaker if I use a toaster oven or Air fryer. Have other people just gone lower on the LiFe chargers to preserve capacity for other AC uses? I'm thinking of maybe going with a 30 Amp model, but full recharge will then be 22 hours. Maybe a second 30 amp charger on a switch for when I'm in a hurry to recharge the LiFe bank?

While I'm asking questions, my LiFe batteries will last longer if i don't always charge them to 100%, but I have not seen that "set a max percentage charge" feature in a small marine environment AC charger. (My home 48 KW solar system has a setting for that.) It looks like the Victron Blue Smart charger might get there by setting a lower charge voltage via Bluetooth, but they only go up to a 25 A. model.). Thanks!

 

[dLj]

Wow - almost 700 amp/hrs of useable power... man, you run some electronic toys!

I don't think anyone can answer your question as to how big a charger to put on for your new bats. That answer lies in your lifestyle on your boat. I wouldn't be overly concerned running close to max power - that's what it's made for. But that's me. I charge my lithium batteries at 0.5c. meaning for my 400 amp hr bank I charge at 200 amps. But that's with my engine alternators. When hooked to shore power it's much less but that's because I run through my inverter/charger and that's the limiting unit. If I were adding in a separate charger I'd start by looking at what my bats max charge rate permits - usually about 0.5c or 325 amps in your case. But you need to check what that is for your batteries. Therefore, I'd start looking there and work backwards to what my system can handle. And what I need... But I quite like short charging times...

As to the upper limit - as far as I'm aware - nobody really knows. If you've got a reference point from your solar at home - that sounds as good as any...

dj

 

[dlochner]

Look at the Victron Multiplus Inverter/chargers. Some of them have a high charging rate. One Multiplus feature is the ability to automatically get AC power from any source. In your running the toaster while charging example, the Multiplus would effectively and automatically reduce the charge current to provide AC to the toaster. This will of course extend the charging time, but that's not a big deal as it only takes a few minutes to toast a bagel.

Rather than having a second charger, consider using a DC-DC charger. Victron has one that can output 50a and I believe Sterling has larger capacity DC-DC chargers.

 

[colemj]

At your battery capacity, there really isn't any practical limit on the size of the charger, as they will be able to accept all the current you can give them.

Decide how you will be charging. You state you will have a shore power charger, which typically means the boat will be on shore power for a longish time between use. If so, then size of charger doesn't matter much because you have lots of time to charge.

If you are planning shore power charging to be as rapid as possible, as a charging stop while using the boat, then as large of charging sources as you can reasonably apply given electrical limitations is the answer.

As for running other things while charging, if your usage is the first case, then the charger will likely be on float or turned off most of the time after the initial charge up. So other loads won't be consequential then.

Mark

 

[BAD ORCA]

If you are in no rush to charge your batteries, there is no reason not to use a smaller amperage charger. I charge my 300ah LFP bank with a 50 amp Victron Phoenix Smart IP43 charger. At full 50 amp output id draws about 700 watts. I dont bother to try and manage AC loads while its charging and have not tripped my 30Amp dock breaker yet doing usual routine. That being said, i'm never cooking with the induction hob while running the water heater and air conditioner at the same time anyways regardless. There is always the option to run charging at night or remotely if you use Victron, you could turn charging on/off remotely while away from the boat. Maybe a small solar panel to trickle charge the start battery? I like the DC-DC charger idea as well. You can put it between banks to keep the start bank topped up.

The Victron Phoenix charger has a version that has three outputs. so it can be connected to two battery banks at the same time. It will share the 50 amps with both battery banks until one gets full and then pass along the extra amps to the bank that still needs charging.

 

[sailbadsinner]

Yeah, my nickname in college was "Mr. Electricity..." One of the first things I did with this boat was to replace the small number of incandescent lights with a lot more LED lights like new boats have--mood, task, light strips, etc. It is now very cheery in the evening with the dimmable and settable daylight/evening lights all over the boat. But it draws more power. Music, video, AIS transmitter required for Mac race, .... everthing seems to draw more power.

Right now, the boat lives at a dock and I take weekend and 2 week cruises around Chicago, so the smaller charger taking 22 hours for a full charge is fine. With the Victron, it looks like I can set the voltage to keep the LIFe at a lower charge state at the dock for long life, but then run them up to 100% charge before a trip.

But I'm also equipping the boat for wintering in the Bahamas and Eastern Carib starting next year, when I will be at a dock a lot less and might want a faster charge. DC powered AC is on the upgrade list and I already have a BedJet (look that up, it is great!)

But that is a good point about the DC -to- DC charger which I will be installing to charge the LiFe batteries from the LA only engine alternator/regulator. I had been planning to rig that to be disabled when the engine is not running, but that could be configured to allow some of the 40 amps from the LA battery charger to flow to the LiFe pack over the DC-to-DC converter once the LA batteries are charged.

The tangled webs we weave! I was just renewing my US Sailing Offshore Safety at Sea cert and they reminded me that 55% of boat fires come from electrical problems, so careful design and installation is a good idea.

 

[Stu Jackson]

That answer lies in your lifestyle on your boat.

This ^^^^. What your storage capacity is (i.e., battery ah) compared to your Daily Draw Load is THE critical source of any answer to your question.

You could have a gazillion ah of storage, but if you only use 100 ah a day, it's no different than having 400 ah of storage. As in: big deal, so you have a big battery.

Glad that you also recognize that charging LFP to 100% is not something to be proud of. It means you have read the instruction manual.

Good luck.

 

[BAD ORCA]

Yeah, my nickname in college was "Mr. Electricity..." One of the first things I did with this boat was to replace the small number of incandescent lights with a lot more LED lights like new boats have--mood, task, light strips, etc. It is now very cheery in the evening with the dimmable and settable daylight/evening lights all over the boat. But it draws more power. Music, video, AIS transmitter required for Mac race, .... everthing seems to draw more power.

Right now, the boat lives at a dock and I take weekend and 2 week cruises around Chicago, so the smaller charger taking 22 hours for a full charge is fine. With the Victron, it looks like I can set the voltage to keep the LIFe at a lower charge state at the dock for long life, but then run them up to 100% charge before a trip.

But I'm also equipping the boat for wintering in the Bahamas and Eastern Carib starting next year, when I will be at a dock a lot less and might want a faster charge. DC powered AC is on the upgrade list and I already have a BedJet (look that up, it is great!)

But that is a good point about the DC -to- DC charger which I will be installing to charge the LiFe batteries from the LA only engine alternator/regulator. I had been planning to rig that to be disabled when the engine is not running, but that could be configured to allow some of the 40 amps from the LA battery charger to flow to the LiFe pack over the DC-to-DC converter once the LA batteries are charged.

The tangled webs we weave! I was just renewing my US Sailing Offshore Safety at Sea cert and they reminded me that 55% of boat fires come from electrical problems, so careful design and installation is a good idea.

yes. i have not actually tried it yet, but you can set the parameters in the Victron charger settings to maintain a lower SOC. Mainly, might only need to play with the float voltage setting. I thought i remember reading setting it somewhere around 13.4'ish float will get you something like 80% SOC and hold it there. I forget the specifics though.

 

[sailbadsinner]

>. You should also recognize that charging LFP to 100% is not something to be proud of. It means you jay not have read the instruction manual

Exactly, that is why I'm asking about finding a charger to keep them around 75% when the boat is at the dock or I'm on a day sail or weekend trip but taking them to 100% before a 333 mile Chicago to Macinaw race with a big crew onboard and no expected engine running time for several days. I think we all agee with your statment above, so why is it so hard to find a charger which will do that? I have looked at about 80 LiFe batter chargers and I found one that will do that. I guess the vendors want us to buy LiFe batteries more often...

Good point about knowing my daily use. My problem is I'm not living on the boat now. The last owner put in 2 Rutland wind chargers and 2 large solar panels and lived for 2 years in the Med and Easter Carib with that power budget, 700 Ah of LA and no dock charging. But I use a CPAP at night, I like to cook with electric gadgets, and I'm upgrading boat systems with computers and iPads, so I need more power. I have a spreadsheet of guesses on daily use and solar and wind gain, but I'm curious what other people are doing about this issue.

When my home power hourly rates go high($1.35/Kwh one day last week), I switch the house to running off pure solar and batteries until the rates go back down to $0.11/Kwh. So I know my house power budget. The SolArk 15K controller then recharges the 40 KWH of batteries with solar or at 275 Amps from the Grid. But that controller/charger weights 135 lbs and would not fit in my engine room! lol.

 

[dLj]

I think you are over-thinking this. Just charge the batteries then turn off the charger. It doesn't really matter if you charge them to 100% and then just let them sit. LiFePo batteries have a small discharge rate. Let them drop down to where you feel you then need to recharge, turn off the charger when they are back up somewhere in the 90% range and turn off the charger. Or don't and let them go back to 100%. It's doesn't kill them. It seems the issue is when you constantly maintain them at 100%.

dj

 

[Blitz]

I think you are over-thinking this. Just charge the batteries then turn off the charger. It doesn't really matter if you charge them to 100% and then just let them sit. LiFePo batteries have a small discharge rate. Let them drop down to where you feel you then need to recharge, turn off the charger when they are back up somewhere in the 90% range and turn off the charger. Or don't and let them go back to 100%. It's doesn't kill them. It seems the issue is when you constantly maintain them at 100%.

dj

I'm not sure he is at the boat all week, but I was thinking he has some power draws during the week or time away from the boat such as freezer, refrig, lights or whatever. Maybe the OP could clarify.
I would have the same question.
He could calculate his draw during the time not there and figure if his bank would hold out in time to come back and charge them up.

 

[TimFromLI]

Whatever charger you buy, but a victron inverter charger. You will eventually want to convert everything over to lithium

 

[dLj]

I'm not sure he is at the boat all week, but I was thinking he has some power draws during the week or time away from the boat such as freezer, refrig, lights or whatever. Maybe the OP could clarify.
I would have the same question.
He could calculate his draw during the time not there and figure if his bank would hold out in time to come back and charge them up.

Good point. I forget that people do run all sorts of stuff when not on the boat.

I shut my boat down when I'm not there. The only thing that could turn on would be my bilge pump, but I have a pretty dry boat. It doesn't take me long to get the frig/freezer back up when I come back but there are folks that want it running so they can just get on and it's already cold. I also have solar so I can be shore-energy independent for a long time even running my frig/freezer. But running that I wouldn't want to be gone longer than a week without being able to monitor how things are running. For me, a long time ago, I realized every time I leave my boat I should do it with the mindset that something may come up and I have no solid idea when I'll be back. So I always leave the boat as if I might not make it back for months no matter what my plans are. I've had several occasions when I thought I'd be back in a few days and sh!t hit the fan making it much longer than planned...

He is a confessed technology junkie... Nothing wrong with that - just eats electrons... He might have things I haven't even thought about running all the time. It would be good to get a clearer picture of how he runs his boat.

dj

 

[Hayden Watson]

The 0.2c rule is for FLA and does not pertain to FLP.

I can only speak for what I did on my boat. When charging from shore power, I wanted to be able to recharge the fully depleted battery to full charge in about 10-hours so that I could go into a marina near 0% SOC in the evening and leave the next morning with 100%. I have 560Ah and I installed two Victron IP22 30A charger which met my design goal.

When charging from the engine, I wanted the least run time I could manage. I installed a 250A large frame Denso Hairpin alternator on my 23-hp Universal M25XP which is controlled by the Zeus regulator. I limit the max output to 190A to stay withing the limits of other items in my charging system. With output limiting to control the alternator temperature, this lets me do a 0% to 100% in less than 4-hours.

 

[CrispyCringle]

If you like playing around with settings and features I highly suggest getting a Victron charger (and their other stuff). If your worried about it, the Multiplus Inverter/Chargers have the ability to dial down the maximum Amps they will pull from shore power. They can also be set to kick in with inverter power when you try to pull to much from shore power. Properly set up, you wont overload your shore connection. The OP mentioned the desire to charge to a intermediate SOC- like 70-80%. The SOC value you see on a battery monitor is not a direct read like voltage. Its a derived value that is an estimate. Without going into the details of my boat setup, you can do that, but its really just tricking the system to think its full at, say 13.15 V instead of 13.2V. But for me, I do that on shore power because I also have solar and I dont want the AC charger kicking on when there is free solar available. If you dont have a bunch of solar, just charge it up and let it stay at float charge. The multiplus will charge at 120 Amps DC. Thats not a huge draw from shore power, but that will top up your batteries fast. Thats the beauty of lithium- it takes all you can give it until about 98%, unlike lead that will start to pinch off the charging around 93% and it takes forever to get to 100% SOC.

So to answer your question, I would go with a high capacity charger. You arent doing your system any favors with a small charger.

 

[sailbadsinner]

A lot of good replies, thanks so much! Yes, I'm sure I will go all LIFe eventually. But there are some more urgent system fixes needed for this new-to-me 1985 cruiser, like a mass of wires and fuel lines broken loose from rusted fittings flopping around in big tangle in bilge water! (The last owner was good about 'keep the boat from rotting' things like replacing hatches and portals and keeping the deck sealed, but the engine room is very neglected!). This project is just that 4 of 7 100 Ah LA batteries needed replacing and I was not going to buy more LA batteries! So four 165 Ah LiFe batteries with bluetooth are replacing them with minimal changes to charging system this year. The individual battery 'blueteeth' give me accurate SOS, down to the cell--I would not buy a LiFe battery without bluetooth at this point just for that feature alone, i.e. is there a bad cell, are the cells equalized, etc!

Yes, I'm pretty sold on the Victron at this point as I do like to program things to be optimal. But I also like to just relax when actually sailing. Right now, rather than one big Victron charger I can reprogram for different situations, I'm thinking about two of the 25 Ah Smart Blue ip67 chargers; one on all the time when on shore power set to voltages that gives me about 75% SOC and a second on a switch, set to give me 100% state of charge I can turn on before a trip. That also gives me redundancy in case one fails.

But that is a good point about using solar and wind power ahead of dock power. I used to teach an IOT architecture course, so I could create a little IOT box that reads my outlook calendar to find the next sail, looks at the weather forcast to see how much sun and wind I would get and then turns on the dock power chargers the night before my trip. The home solar power DIY community has a Rasberry Pi open source kit to build stuff like that.....But I'm not doing anything like that until my fuel lines and wires in the engine room are all secure and safe! And the soundpooofing that is flopping around. And the ... (Ok, a remote on/off over the Internet would be simpler!

Right now I also don't trust the charge point setting on the two Rutland 1200 MPPT controllers, so I turn off the wind and solar charging when I'm not on the boat. Keeps the wind generators safer in storms too. But that can change with some effort.

 

[UpperPintle]

Check on specs on the BMS that you will use for your 650 Ah bank. The spec sheet should how the max continuous charge rate.

 

[Tally Ho]

I have a 314 Ah LFP battery I am installing on Tally Ho this year. I have a 20 Victron charger and a 60 amp charger by Wattcycle. Both charge the battery just fine…but the 60 amp charger does it a lot faster (when battery is been drawn down). But it also makes a lot of noise when it is cranking out 60 amps. And I am not sure about the charging profile on the WC charger…

So, I will be using the Victron on the boat, and feel comfortable. i sail during the day (or a weekend) and return to the dock where I am on shore power. The Victron has the battery topped off and ready to go the next day. Now, my energy requirements are pretty minimal.

So, as has been stated…you need to know how you are going to use your available power, how often you are on shore power, and for how long.

Greg

 

[BAD ORCA]

But that is a good point about the DC -to- DC charger which I will be installing to charge the LiFe batteries from the LA only engine alternator/regulator. I had been planning to rig that to be disabled when the engine is not running, but that could be configured to allow some of the 40 amps from the LA battery charger to flow to the LiFe pack over the DC-to-DC converter once the LA batteries are charged.

Yes. If you connect one to your start bank (charger) and one to your house bank and have a DC-DC charger between them, you could if you wanted to, turn them both on at the same time and send the charge current from the 'start bank' charger through a DC-DC charger to charge the house bank instead. It gives you redundancy by having the two chargers, but also the option to direct the charging however you want, or to pass extra charge current from your engine/alternator along to your house lithium bank when motoring, without wasting the energy or for fear of melting down your alternator. Also, Sterling Power which makes a great product has bi-directional DC-DC chargers now, so in essence could pass as much power as you want between battery banks in either direction.

 

[jssailem]

I wanted to be able to recharge the fully depleted battery to full charge in about 10-hours so that I could go into a marina near 0% SOC in the evening and leave the next morning with 100%.

This statement by Hayden gives you the clue to the question of “How big?”

It is based on your drain of the battery and how long it will take to replenish the battery. You estimate how much your sailing activity will drain the battery. I would figure on the usage might be for at least 80% of your cruising time. That will give you a number you need to fill. Then size the charger to refill the battery in the time you want to allow. It is a depth of replacement for the time you want wait around equation.

@Tally Ho shares this equation results in his response #18 above. Do the math and you’ll discover the best charger for your needs.