Can you combine two chargers to get 50A?

[LeoKa]

At my marina I have 50A shore-power available. My inverter/charger is 30A max. (Mastervolt CombiMaster 12/3000-160 120V). I wanted to buy 50A model but it was on back order forever.
Recently, testing my solar system charging, my lithium bank (680 AH total) was depleted to 55% purposely. When I reconnected the shore-power the draw was too much for the MasterVolt and kept shutting down and back on, till the battery level was back to 65%. After that, the charging went on smoothly. The 160A max from the charger was not enough juice for the batteries.
The 50A MasterVolt model can do 200A charging, but I will need to buy one and get rid of the 30A model I have.
What if I buy just a regular charger from MasterVolt and combine it with my existing 30A charger/inverter? Is this possible? Will I get the 50A from shore? If yes, how would you do it?
MasterVolt chargers can be networked with Masterbus, but there is no instructions on how to combine two chargers and how to wire them?
Thanks.

 

[twistedtree]

I think I would be on MasterVolt to explain why their charger is shutting down, and asking for my money back if they can't make it work to specs. It should be able to run at full output indefinitely. Hopefully it's just a setting of some sort.

 

[LeoKa]

Maybe you are right and it should run, regardless of the load. However, I do not have good experience with MasterVolt tech support, or even on communication level.
So, the shut down and back is not really my concern. I am stuck with this model, unless I get rid of the existing setup and go with another brand. All and all, I’ve spent over 3K for this setup.
My question was about how to get the 50A from the shore, if I keep this 30A charger/inverter?

 

[KnotYet]

It sounds as though you are comparing the 120 VAC shore power rating to the
12 VDC charger capability. Those values are independent of each other.

If the 30A you refer to is the max draw at 120 VAC that would be about 3600 watts.
If the 160 refers to the charging amps, at 14 VDC that would be about 2250 watts.
50 amps at 120 VAC can provide about 6000 watts of power.

 

[LeoKa]

Maybe my description of the problem was not good. It happens. Let’s put aside the charging issue.
What I really want is to figure out how to provide the 50A to the house? Do I need another inverter and combine it with the existing one? My boat is wired for 50A already; cables, distribution panel, breakers, etc.
The only bottleneck is the 30A inverter/charger, which is fairly new and works fine. I need to keep the existing equipment, but willing to buy additional, if I can provide the 50A instead of 30A to the boat.

 

[KnotYet]

If your boat has AC with the inverter turned off then you can use whatever amps
your AC breakers and wiring are rated for. If your outlets are connected only to
the inverter output with no 'pass-through' ability, which would strike me as odd,
there should be a way to do it by adding an appropriate switch and breakers.

 

[tiltrider1]

The simple answer is yes you can connect two battery chargers to the same bank to speed up recharging.

I have an Inverter/charger that is capable of adding 150 amps DC to my bank. I also have a 40 amp DC back up charger should my Inverter/charger not be available.

Once in a blue moon I find my self wanting to minimize generator time while recharging a deeply depleted battery bank. In these times I turn on the back up charger. This lets me charge at 190 amps instead of 150.

That said, thing are not really just that simple. Wire size and voltage loss are important topics. The banks ability to take the additional amps come into consideration and can your shore or generator supply enough power to supply two battery chargers are also important.

 

[LeoKa]

If your boat has AC with the inverter turned off then you can use whatever amps

your AC breakers and wiring are rated for. If your outlets are connected only to

the inverter output with no 'pass-through' ability, which would strike me as odd,

there should be a way to do it by adding an appropriate switch and breakers.

Wow, that is cool! I had no idea, but you are correct. I just turned off the inverter and I still run the 120V appliances. Thank you for this clue.

 

[LeoKa]

The simple answer is yes

That said, thing are not really just that simple. Wire size and voltage loss are important topics. The banks ability to take the additional amps come into consideration and can your shore or generator supply enough power to supply two battery chargers are also important.

I believe all my wiring is up to this requirement and the lithium bank I have can suck up plenty or current.
May I ask you how did you connect them?

 

[READY]

If I am correctly reading between the lines, I think the issue is that the existing transfer switch in the inverter charger is only rated for 30 Amps. If your inverter is sucking a lot of that just to charge the depleted batteries there is not much current left for any other connected loads (that are on the inverter). So the inverter transfer switch is shutting down as it should. Without knowing the full set up on your system it is impossible to suggest the best solution. If you can add a second charger and safely connect it upstream to your 50amp shore power you could get more charging current to the batteries.

 

[READY]

Sorry one other observation. Most battery chargers allow you to limit the amount of charging amps.If you can do this that will allow more current for other uses. You need to keep the total current flowing through the inverter/charger(AC 120v) to less than the 30 AMP rating. Sure your batteries will charge a bit slower but you don't need to make any other modifications.

Other than the charger, what other loads were running when it shut down.Normally an invertercharger is only connected to moderate loads and things like heaters or air cons would not be on the inverter circuit.

 

[LeoKa]

I think we are going off track here.
My story about the inverter/charger shut down has no significance. I believe, the unit behaved as it should have and when the battery bank needed too many amps, it could not deliver, so it shut down for safety. My unit can handle 160 amp max charging, but I could see on the monitor that it was trying to draw more. Again, once the battery bank was around 65% the shut down cycle stopped and everything was charged up normally. I think the 4 lithiums I have are just too much to fill at 55% where it was.
This thread is about how to add another charger/inverter and connect to my existing one. As it was stated above, this could give me enough charging capacity to handle the lithium bank’s need. Additional benefit would be having more inverting power, as well, since I have the 50A shore power available.

 

[SteveK]

deleted

 

[LeoKa]

I think I did describe what happened, but let me try again.

My lithium bank was down to 55% SOC. This happened, because I turned off my inverter/charger to test my new solar system charging. My solar MPPT set is new and I wanted to know, if my panels can keep up with the house needs. (They could not, so my battery bank was depleted) This was a test only, so no problems, no damage.

When the test ended, SOC was at 55%, I turned the inverter/charger back on to recharge the battery bank (680AH). At this point, the inverter/charger display was showing a draw over 160A, which is the max of my charger. Once the draw was close to 165A, the inverter/charger turned off the charging for few seconds and restarted it again. I could see the charging coming back, but again, around 165A draw, it would turn off again. This was going on until the SOC was around 160-165%, when finally the draw was below 160A and the charging continued normally. Nothing broke, no damage, no burning. It was just proper functioning, in my understanding.

I just mentioned this to illustrate why I want to either replace my existing inverter/charger (costly!), or just add another inverter/charger to increase my charging capacity. Since the shore power here is 50A, there is room for another inverter/charger.

So, my question is; How add/connect another inverter/charger to my existing MasterVolt Combimaster?

 

[READY]

I checked and there is a setting for max charge. I would highly suggest you start by reducing this. As previously mentioned even if running at max rated charge it should not shut down. I would figure out why that is happening. It could be a thermal shut down. The size of the battery bank would not create a shut down under normal circumstances. Sure a bigger bank will take longer to charge but I cannot come up with a theory of why it is suddenly working as expected once you get to 65%.I assume it is set up for a lithium charge profile?

 

[LeoKa]

.I assume it is set up for a lithium charge profile?

Yes, it is set to Lithium profile. However, MasterVolt does not allow any customization. Plus, they only vouch for their batteries working properly with that profile.

The max charging is default to 160A. That is where it is now. I do not plan to run any more solar tests, so the lithium bank will not go down again to 55% SOC. At the marina, I always have shore power to keep the batteries up. Underway, I have charging option from my generator, or from the alternator.

 

[twistedtree]

I think we are going off track here.
My story about the inverter/charger shut down has no significance. I believe, the unit behaved as it should have and when the battery bank needed too many amps, it could not deliver, so it shut down for safety. My unit can handle 160 amp max charging, but I could see on the monitor that it was trying to draw more. Again, once the battery bank was around 65% the shut down cycle stopped and everything was charged up normally. I think the 4 lithiums I have are just too much to fill at 55% where it was.
This thread is about how to add another charger/inverter and connect to my existing one. As it was stated above, this could give me enough charging capacity to handle the lithium bank’s need. Additional benefit would be having more inverting power, as well, since I have the 50A shore power available.

This is a fundamental misunderstanding about how chargers work. Every charger I have even encountered will limit it's output at it's rated max (or close to it), and run like that forever until the battery voltage comes up.


If the charger is shutting down, something is wrong/broken. I agree this is separate from your desire to add more charging capacity, but something is still wrong with the MasterVolt.

 

[LeoKa]

If the charger is shutting down, something is wrong/broken. I agree this is separate from your desire to add more charging capacity, but something is still wrong with the MasterVolt.

I am not questioning what you say. It has only happened once, never before. I had it for 2 years. Maybe there is something to be fixed, but MasterVolt is not very helpful on any issues. If this was a frequent event, I would research it, but my goal is to figure out the additional inverter/charger schema. Wiring, matching, etc.

 

[Bmarler]

Some inverters are able to be stacked, (wired in parallel) some are not. If the goal is just to have more charging power, another stand alone charger could work.
The other issue, is that you may be exceeding the capacity of the transfer switch on the existing inverter. Running a 50 amp service through a 30 amp transfer is no good.
A 50 amp main panel with a 30 amp breaker servicing the inverter and a sub panel for inverter loads might be appropriate. A separate breaker for the additional charger adds charging capacity without taxing the transfer switch.
Your options really depend on how it’s set up now, and what you’re really trying to gain.

 

[LeoKa]

The inverter/charger unit is set to 30A limit by default. I have not changed this.

The wiring is 50A all the way, including main/sub panel breakers.
I can add another breaker for 30A and wire in a new charger, if I buy one.

This additional charger should be connected to the bus bar which feeds the battery bank, correct?

 

[JDCAVE]

No one has yet asked, “Why would you want to add another charger?” I don’t see a reason. Particularly with LFP. It’s simply not cost effective. Your battery bank (680 ah) is too small to warrant a second charger.

If you discharge your bank to 55% SOC, you need to put 45% of 680 ah back into the bank. That’s 306 ah, or a little less than 2 hours of charging at 160 amps. Now if you follow TT’s logic and get to the bottom of why the charger is dropping out and fix that problem, then you can charge that LFP bank up to nearly 100% SOC in 2 hours. If you are concerned with the house loads and throttle it down to 100 amps charging, you’re done in 3 hours? Surely that’s good enough? At least it would be for me.

Jim

 

[twistedtree]

OK, then there are a few ways you can do this.


1) Do you want/need more inverter capacity in addition to more charging capacity? If so, then I would check to see if the mastervolt inverter can be "stacked" with a second one in parallel. If you do this, then you will need to adjust the input limit in each so they don't together overload your 50A shore connection. This will mean either buying the mastervolt computer adapter and downloading their software to make the adjustments, borrowing the same from someone, or hiring someone to come make the adjustments.


2) Install a dedicated charger. It should be sized for about a 20A AC input load since that's the max that you have available after the inverter. But keep in mind that if your inverter plus charger are consuming all of your 50A, then there is nothing left over for house loads. You will have to make adjustments to either or both devices to reduce their power draw to leave some for house loads, and that will take you make to needing the mastervolt adjustment tools.


As for charger brand, there is advantage to getting mastervolt because it will in theory work better with the inverter, but I wouldn't count on it, especially with Mastervolt. And if it doesn't work as desired, you will be SOL as you have discovered with Mastervolt's lack of support.


If you get a different brand charger, just read up on it to understand how you adjust it to work with your batteries. Many need some sort of adapter just like Mastervolt to fully configure them. DIP switch setting may get you close, but check them carefully against what your batteries require. In my experience it's rare to find DIP switch settings that actually match your needs.


3) Reconsider whether you really need more charging capacity. When will you use it if the boat is mostly at dock on shore power, and you recharge underway via alternator? If the problem is the tripping/shutdown, which we now know has only happened once in two years, you could adjust the inverter to reduce it's power draw, in hopes of fixing that problem. But again, you will need the Mastervolt adapter and software.

 

[Bmarler]

The inverter/charger unit is set to 30A limit by default. I have not changed this.

The wiring is 50A all the way, including main/sub panel breakers.
I can add another breaker for 30A and wire in a new charger, if I buy one.

This additional charger should be connected to the bus bar which feeds the battery bank, correct?

Yes. If you decide you really do need another charger, that’s where to put the output, being careful to make sure you’re on the right side of any monitor shunts.
That said, others here are absolutely correct that you probably do not need this.
If the only way to reduce the charge output from the existing mastervolt is to set the breaker size to a smaller setting, I’d try that first. It costs nothing and only reduces the charger output.

 

[Flatswing]

This is a fundamental misunderstanding about how chargers work. Every charger I have even encountered will limit it's output at it's rated max (or close to it), and run like that forever until the battery voltage comes up.


If the charger is shutting down, something is wrong/broken. I agree this is separate from your desire to add more charging capacity, but something is still wrong with the MasterVolt.

This: Most cruising boats (including mine) have large house banks that can accept considerably more amps than the usual single inverter/charger can provide in bulk mode. As twisted tree said, until the abs. Voltage is reached, All inverter/chargers should happily provide the maximum programmed Amps. Adding a second charger will reduce the total charge time but would not be expected to fix the problem of your Mastervolt shutting down at max output. Is the inverter/charger overheating? Does the inverter/charger have a functioning battery temp monitor (or connection to the Lithium BMS) that is shutting it down?

 

[Don L]

I think I would be on MasterVolt to explain why their charger is shutting down, and asking for my money back if they can't make it work to specs. It should be able to run at full output indefinitely. Hopefully it's just a setting of some sort.

I thought the same when I read post#1 that someone had a crap charger.

Instead of thinking getting a second charger (which should be OK) I would be thinking getting a new and bigger charger.

I ran my 70amp charger the other day for 4+ hours at max output couple of weeks ago after doing a discharge test on my LFP batteries.

 

[LeoKa]

Thanks to All for the answers.
Few thoughts.

It is correct, the easiest way to get the 50A from the shore is to replace my existing inverter/charger. This might be my future solution.

My existing setup with MasterVolt is working fine, except that one time, when the draw was too high at 55%. I do have the required MasterShunt, adapter, laptop, software, for the limited adjustments MasterVolt allows. I can reduce the max power draw from the present 160A for my inverter/charger. If the shut down happens again, I might do it.

Adding another charger is also a possibility, since I have all the panel/wiring in place already for 50A. (The only reason I have a 30A charger now, because that was the only model available at the replacement of an old one.)
Do I want to tinker with another brand charger for smooth operation, if that possible? I am not sure. Not until the situation becomes unmanageable.

I will continue to test and watch this charging dilemma. I also wish to know why that heavy draw turned off my charger, but on the daily life here in the marina with shore power on all the time, it is not crucial. However, when the time comes to go to the big blue, I will have to make a decision. I think I will keep the MasterVolt 30A as a backup and buy a new 50A inverter/charger.

Talking about inverter/charger models, I really like those which do not require additional parts for monitoring/settings. MasterVolt is not one of them. I have 6 MPPTs for my solar system and they all have Bluetooth. Very convenient for settings, updates. MasterVolt does not have any models with Bluetooth. Victron ditto. At least, I could not find one.
Anyone can recommend a brand? An inverter/charger 50A with Bluetooth?

 

[LeoKa]

https://www.renogy.com/rego-3000w-12v-pure-sine-wave-hf-inverter-charger-split-phase-design/


How about this one?

 

[SteveK]

I wish to add that my Magna inverter has two input/output each 30A so can pass through up to 60A or in your case 50A by hopping the in/out hot line. I do not know if Mastervolt has that option.

 

[LeoKa]

I wish to add that my Magna inverter has two input/output each 30A so can pass through up to 60A or in your case 50A by hopping the in/out hot line. I do not know if Mastervolt has that option.

No it does not. Max 30A out. 30A transfer.

 

[ranger58sb]

Talking about inverter/charger models, I really like those which do not require additional parts for monitoring/settings. MasterVolt is not one of them. I have 6 MPPTs for my solar system and they all have Bluetooth. Very convenient for settings, updates. MasterVolt does not have any models with Bluetooth. Victron ditto. At least, I could not find one.
Anyone can recommend a brand? An inverter/charger 50A with Bluetooth?

Our Victron MultiPlus 24-3000-70-50-120 sorta kinda has Bluetooth... but it's via BMV-712 or a VE.Direct "Smart Dongle".

But that maybe what you meant about additional parts...

-Chris