Faster battery charging on the hook

[Arthurc]

Has anyone figured out a slick solution for faster battery charging while off shore power? I routinely drop to 60ish percent at anchor since the inverter does almost all the boats AC needs and with a 1600ah agm bank it’s about 8hrs of gen time to recharge using the xantrex 3000 inverter/charger. As far as I know the lifeline L16s will take way more charging amps than the 150, plus at 80 percent the xantrex drops charging rate as it switches to absorption, great if plugged in for long periods but not sure it’s needed during daily use.
I thought about 3 options:

Larger AC bulk charger - hard to wire and play nice with the xantrex, cheapest, requires generator run time.

Large alternator off gen or AC motor - noisy as I’d loose the sound shield, Ac motor would be super noisy given my watermaker sound. Requires generator run time.

Small engine with alternator - complex, another thing to service, But adds redundancy and low fuel usage.

Other than the washing machine, heat pumps (for cooling only) and water maker I don’t need the gen if I did a separate solution.

Has this problem already been solved, and/or am I over thinking it? This was interesting Diesel Battery Charger


AC

 

[DavidM]

I think your best choice would be a single larger charger of as much as 400 amps. I guess they make those somewhere for marine use, have never seen one though. That should cut your genset running time to about 4 hours. Make sure your generator can handle the load as it will be about 60 amps at 120V or 30 at 240V.

I don't think changing to L16 will help your charging rate significantly and they don't come in AGMs AFAIK.

Another help is solar panels to top off the last 15%. It will take a lot of panels and area for 1600 Ah though.

You have a heck of a power load, about ten times that of my little Mainship Pilot 34 so everything has to be much much bigger.

David

 

[Simi 60]

**** tonne of solar works a treat.
We regularly smash in 80+ amps @ 24v and run 240v everything
Batts are usually reading 100% by 10am in summer.

 

[boathealer]

**** tonne of solar works a treat.
We regularly smash in 80+ amps @ 24v and run 240v everything
Batts are usually reading 100% by 10am in summer.

Yep. 1600Ah house bank, 1440W of solar.

By noon on sunny day I am back to 100% with no generator running at all and a full-size double-door house fridge running 24/7.

 

[Arthurc]

I don't think changing to L16 will help your charging rate significantly and they don't come in AGMs AFAIK.
David

Thanks, good idea on solar, and agree on power load, but I have limited interest in trying to reduce it, prolly a reaction to growing up on sailboats.

Lifeline makes 6v AGM L16s Which is what I have, great batteries!

 

[Arthurc]

I hear you on the solar, only problem is I’m in the Pacific Northwest So sunny days are rare most of the year. I realistically only have 12x6 feet of roof space and that’s if I can walk on them.

 

[O C Diver]

Blue Seas offers latching relays (a momentary pulse is required to switch the position from open to closed. Another pulse to the other coil, opens the relay. No continuous power is required to maintain position. There is a manual bypass incase of coil failure.) that would allow you to split the bank into 2 for charging purposes. I would explore getting a large multi stage stand alone battery charger of atleast the same amperage as your inverter/charger. This setup would allow you to split the bank and bulk or completely charge it much faster, and then recombine it. Also, it would give you the ability to only use one charger if the other house loads are too much. Finally, it gives you redundancy if the battery charger in the inverter fails.

Ted

 

[caltexflanc]

Are you running down to 60% SOC of that bank everyday? Or just waiting until you hit that point before charging? We found that running the generator for an hour or two in the morning and likewise in the evening did the trick, but it sounds like we had a lot more stuff on board that required the generator anyway (stoves, laundry dryer, dishwasher, battery chargers for miscellaneous other banks, such as the DC house bank, A/C etc). Then again if you are drawing down 600AH @12v daily (we had a 24v system), that implies a lot of loads too.

Most generators are not fragile and should be run without compunction; I don't see a cost effective solution to your issue unless you are planning to use the boat year around and/or with a 100 nights a year at anchor or a mooring for the next five to 10 years. Then solar or adding a DC generator start to make sense to me.

You don't have to get to 100% SOC every day either.

 

[ranger58sb]

Larger AC bulk charger - hard to wire and play nice with the xantrex, cheapest, requires generator run time.

Think this is what I'd do. Wouldn't have to be bigger than your existing charger function; you should have several options on the market to chose from.

I wouldn't expect it to be all that difficult to wire in. Dunno about playing nice with the existing Xantrex, but I think during bulk and most of absorption both chargers would continue putting out as much as the batteries will take from combined input.

-Chris

 

[O C Diver]

Another thought:
Battery chargers switch from bulk to absorption based on battery voltage. If you added another 150 charger, the two chargers should work in harmony until you reach atleast the absorption phase and maybe the float phase. While it may not shorten the final phases, it should dramatically shorten the bulk phase. This would obviously be cheaper and easier to wire than what I proposed in post #7. The concern would be making sure that you wire in the second charger so that the bank wiring can handle 300 amps of continuous charging.

Ted

 

[Arthurc]

Won’t they trick each other into thinking the battery voltage is higher?

 

[Arthurc]

I actually am on the hook today, might try my 40a portable charger in combination with the xantrex and see if that works.

 

[O C Diver]

Won’t they trick each other into thinking the battery voltage is higher?

As long as they are connected to major battery cabling, the voltage will be the battery voltage and the charger voltage. So the chargers will stay in bulk phase until the battery bank voltage comes up to the switch point. If the wire size were smaller, the resistance value would have the battery charger seeing a higher value and switching bank and forth out of bulk phase.

Still not certain how it will work in absorption and float phases, but halfing the bulk phase should be worth a couple of hours of reduced generator time.

Ted

 

[Arthurc]

And the redundancy is nice, I have at least 25a at 120v free on the B side of my panel (non inverted side) so could fit a pretty big charger.
That said I can’t seem to find a large marine charger above 160a.

 

[O C Diver]

And the redundancy is nice, I have at least 25a at 120v free on the B side of my panel (non inverted side) so could fit a pretty big charger.
That said I can’t seem to find a large marine charger above 160a.

Since we're spending your money, I might consider a second inverter instead of a stand alone battery charger. Lot to be said for redundancy or more capacity.

Really don't think you want to go above 300 amps of charging capacity. That would be close to 20% charge rate on your bank, wouldn't it?

Ted

 

[Arthurc]

Interesting idea, I like it, and frankly it’s not that much more, biggest consideration is mounting location. I do want to ditch my xantrex for a magnum so I could use the xantrex as the backup. Only issue is won’t they be out of sync and affect my 240v stuff (CruisAir)

 

[Endless Adventure]

I have a slightly smaller house bank - I replaced my Magnum 2812 with a Victron Quatro 12/5000/220-100/100 120V and upgraded my cable to 4/0. This gives me up to 220 amps charging though I have it set to 180 max for bulk and rarely see it above 120 unless I’ve really pulled the battery level down.

 

[O C Diver]

Interesting idea, I like it, and frankly it’s not that much more, biggest consideration is mounting location. I do want to ditch my xantrex for a magnum so I could use the xantrex as the backup. Only issue is won’t they be out of sync and affect my 240v stuff (CruisAir)

Not sure sure what you mean.

Ted

 

[tiltrider1]

The first thing I would check is the size of your wiring. Voltage drop between your charger and your battery could cost you significant time. Once you are satisfied that you are getting 100% out of your first charger then adding the second charger to the mix as OC has stated will help greatly with the bulk phase.

I run 4/0 wire between my 150amp charger and batteries to reduce voltage drop issues and speed up charging. I also have a 40amp back up charger that I use to speed things up while charging off the generator.

 

[Arthurc]

Yep I’m on 4/0 wire and getting the full charging amps. I think the problem is my avg use is 50a during the day, the Charger is 150a, so I’m getting a max of 100a in at bulk, never mind when I use the microwave, etc since the whole boat is basically inverted. So on avg I’m getting maybe 80a at bulk, if my recharge needs are 800a that’s a long time just at bulk, never mind the fact it switches to absorption after 480a of charge.

 

[Arthurc]

Not sure sure what you mean.

Ted

Isn’t there an issue with them not being in Phase and damaging a true 240v appliance? My understanding is if you buy two exact same xantrex or magnums they can sync together to provide 240v service but just adding another inverter to my B side of the panel could cause major issues (I think, but I’m no expert)
I think it’s both frequency and phase that need to be aligned?

 

[Retriever]

I've been puzzling over the same problem.

Solar really does help, even in the PNW, at least in the summer. I have ~1200 watts on the PH roof and it gives me ~350 amp hours most summer days. That saves a lot of genset time. I normally charge in the morning until I'm well into absorption, then let the solar do the rest throughout the day.

Cloudy days and winter I end up running the generator more than I'd like, and too much of that time is just to charge batteries. Shortening the bulk time by adding additional charging capacity seems like it would make a large enough difference to be worthwhile.

My boat has a single Victron MultiPlus 3000 watt inverter with 120 amp charger. I'm thinking I'll add another identical inverter, wired to give me 6000 watts of 120v power. This will provide 240 amps of charging at 12v. A few things to think about with this setup (and I'm trying to figure this stuff out from Victron)...

1. Are both inverters always idling? Or does the slave shut down to save the idle power draw when there's little power demand (most of the time).
2. What happens if one inverter fails? Does the other one seamlessly take over? Or does everything shut down until the programming is changed from a master-slave system to a single inverter.

With more inverter capacity, a big battery bank, and large alternators, I'll likely also add a 120v-240v autotransformer so I can occasionally power 240v (washer, dryer, watermaker, limited AC) loads when running the main engine. This gives some redundancy if I lose the genset and means I won't have to run the genset really lightly loaded when I just want to make water underway, for instance.

 

[hollywood8118]

Even though it is the PNW I do not believe your giving solar the credit it is due, I know of many boats that use solar here with great results. 50a of continuous drain is a fair load, I cringe when both of my refers are running with other loads and I get to 16-20 amp drain.. and that's intermittent. I'm about to start installing panels on my boat to help the bank.

HOLLYWOOD

 

[Arthurc]

Which panels are you going with?

 

[ksanders]

You can double your charging and inverting capacity with a factory supported solution for your XANTREX SW series inverter/charger.

Simply add a 2nd XANTREX SW series inverter/charger to your system and configure it for parallel stacking.

The instructions for this are in the Xantrex installation manual.

Here is a cut and paste from the manual

Parallel Stacking
A parallel stacking configuration allows the inverter and charger capacity of a system to be doubled.

This is a planned winter upgrade for my boat. Adding a second inverter/charger will reduce my generator run time and provide redundancy as well.

The greawqt thing about this solution is that there are no conflicts between the chargers as they transition out of the bulk charging phase which occures at about 85% SOC on my bank.

 

[twistedtree]

I too would add one or more AC to DC chargers. Mastervolt and Victron make them, as do others. I had a 1000Ah bank and charged at 280A using the generator. It still takes time, but less time vs with less current.


To answer your earlier concern, the chargers will not interfere with each other. Just be sure they are programmed to do the same thing. During Bulk they will all be going balls to the wall. But when Absorb is hit, they will all back off, and it's likely one charger will work hard than the other(s), but who cares.


Keep in mind that more charge current will reduce your charge time, but it's not a linear relationship. Doubling charger current will not cut charge time in half. Your bulk charge will be faster, but you will also reach absorb at a lower SOC, and absorb will then run longer. I'm not sure just what the gain will be, but doubling the charge rate might yield 75% of the charge time.

 

[DDW]

You can reduce the time in bulk by adding charge capacity. 1600AH of Lifelines will take probably 500A charge initially at 60% SOC, and maybe 800A at 40% SOC. When absorb is hit (constant voltage reducing current) this due to battery chemistry and extra charge capacity will not change that. A full charge (important for AGMs) will take 6 hours regardless of your charge capacity. You could change it by changing battery chemistry to LFP, which will accept a very high charge to near 100%.

If replacing chargers or inverters, not sure why you would pick Magnum over Victron or Mastervolt - Magnum is 20 years behind in every way.

 

[ksanders]

You can double your charging and inverting capacity with a factory supported solution for your XANTREX SW series inverter/charger.

Simply add a 2nd XANTREX SW series inverter/charger to your system and configure it for parallel stacking.

The instructions for this are in the Xantrex installation manual.

Here is a cut and paste from the manual

Parallel Stacking
A parallel stacking configuration allows the inverter and charger capacity of a system to be doubled.

This is a planned winter upgrade for my boat. Adding a second inverter/charger will reduce my generator run time and provide redundancy as well.

The greawqt thing about this solution is that there are no conflicts between the chargers as they transition out of the bulk charging phase which occures at about 85% SOC on my bank.

Looking at the instruction manual this is really easy. You are basically paralleling the cables for the most part and connecting the 2nd unit to the System Control Panel.

 

[O C Diver]

Isn’t there an issue with them not being in Phase and damaging a true 240v appliance? My understanding is if you buy two exact same xantrex or magnums they can sync together to provide 240v service but just adding another inverter to my B side of the panel could cause major issues (I think, but I’m no expert)
I think it’s both frequency and phase that need to be aligned?

Ok, you have options.

As Kevin was saying, you can stack them.

The other alternative is to not run the inverter on the second one, so it's only a battery charger. I was focusing on having a inverter/charger on each generator leg for balance.

At this point I'm going to step back. 300 amps out of 2 chargers is a lot of juice. Without seeing your battery and wiring setup, I don't want to take something for granted and you have a spectacular event. I think the concept of 2 battery chargers (whether splitting the bank when using the second charger or not) is very sound for your application. Evaluating bank wiring and calculating maximum charging rate for the batteries based on a manufacturer's recommendation, needs to be carefully examined and planned. The last part would be what happens if you're using both chargers, start the main engines, and have additional amps possibly from the alternators.

Ted

 

[rslifkin]

More charger capacity to pump more amps in during bulk will certainly help. I'd also look at adding as much solar as you can reasonably fit (even if it's only a few hundred watts). That'll reduce your draw-down, and if you have periods of lighter load during the day, it'll help get things topped off after the generator does the bulk charging.



Realistically thinking, what are your biggest loads and when do you tend to use them? It might make sense to plan the biggest loads to occur during a generator run so you have less power to put back into the batteries (because you won't have taken it out in the first place).