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igvan avatar image
igvan asked

Two inverters in 12v van system / paralleling batteries

Hi all, I have a 12v 600ah lifepo4 setup in my van, ~300 amp max discharge. Not Victron batteries, but all other components are. My main inverter is a Multiplus 3000. I am planning to add a Phoenix 500 watt inverter to use for small loads, mainly laptop charging, so that I do not have to always fire up the Multi. I plan on running them both to my Lynx Distributor separately and fusing them appropriately. The Multi will power my AC breaker panel, the Phoenix will just run one plug via the outlet on the unit. I do not plan on running them in tandem, but it may occasionally happen unintentionally.


Does this all sound good/acceptable? I believe it should be fine, but I'd like to tap into all the knowledge of this community.


Another question that maybe should be its own post, but my bank is two 300ah batteries. They will be paralleled, but I am going to fuse them separately and have a Blue Sea switch for each individual battery. From there they will go to the Lynx distributor. I am contemplating whether they should be paralleled at the distributor, or beforehand, which would allow me to also have a master switch, in addition to the two individual battery switches. Redundant, I know, but still thinking about doing it.

What are your opinions? Each to its own position on the Lynx, or paralleled beforehand and share a position on the Lynx? I know I can just parallel at the battery, but I prefer to fuse and switch each individually and parallel downstream. If paralleled before the Lynx, suggestions on what busbar would be best suited for that? This may be stupid, but could I just run each battery cable (after fuse and switch) to the same post on an appropriately rated master switch, then to the Lynx?


Thanks much for any and all opinions/suggestions.

battery chargingmultiple inverters
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6 Answers
offroadflow avatar image
offroadflow answered ·

Hi Igvan.

To the first question:
No problem there.
Even running both at the same time.
Always as long as you keep the AC out separate (i know you know but mentioning it anyways).

As for the second part:
Just keep it simple.
;)

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igvan avatar image
igvan answered ·

Thanks much for the input, @offroadflow


Any others have input/advice, particularly on the battery parallel question?


Thanks all


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najab avatar image
najab answered ·

What's your reasoning for having independent battery switches plus a master switch after they're paralleled? Is it so that you can switch out one battery and still run the other?

If so, have you considered the scenario that one is fully charged and the other depleted, one battery switch is on with the other other off and you then switch the other one on?

I'm no expert where batteries are concerned but I'm seeing a large current being drawn from the full battery as the voltages equalise - possibly damaging battery one or the other.

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igvan avatar image igvan commented ·

I'm wanting each one switched and fused just in the instance something goes wrong with one battery and I need to disconnect it from the system. Just seems best practice to fuse each individually, though I know paralleling at the battery is perfectly okay.


I guess the master switch after is totally unnecessary, and I think I will forget about that idea. So it would be fuse and switch each battery and run each to its own position on the Lynx Distributor. I know a Power In/simple busbar would be all I need since each battery is already fused, but I already have two distributors and enough space for each battery to use a position. The negative cables I would have to parallel at the SmartShunt before sending to the distributor to keep just the batteries on the battery side of the shunt.


So does the hive mind here think its superfluous and unnecessary to fuse and switch each battery, or should I stick with my plan? Another thing I like about fusing and switching each is I can run slightly smaller cabling from each to the distributor. I have plenty of 2/0 already, so thought that would be a good plan rather than paralleling at the battery with 4/0.


Again, thanks to everyone for the thoughts.

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igvan avatar image
igvan answered ·

Thinking now about simplifying and doing a post connection between the two batteries. This would allow me to fuse each battery individually but just have one master switch for both.


So it would be 200 amp terminal fuse with 2/0 from each battery+, to a post, then 4/0 from the post to switch, and from switch to Lynx Distributor.


Does this sound like a smart way to go about things? Again I'm fully aware I can just parallel at the terminals, especially with a two battery system, that is perfectly sufficient, but I do still like the idea of fusing each battery at the terminal.

If this is a good idea, does anyone have good recommendations for what post to use to parallel the batteries?


Thanks all

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pwfarnell avatar image
pwfarnell answered ·

Do not forget that if both inverters are on, the ac outputs will not be in phase with each other and the voltage difference between the two live wires could be much higher, up to twice your nominal voltage.

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igvan avatar image igvan commented ·

Thanks for the comment, I thought running them in tandem could affect phase, but did not fully understand that meant it could spike the voltage so dramatically.

I do plan on only using one at a time, however, as with anything that is not completely idiot proof, I do for-see the instance where someone forgets the small inverter is on and powers on the MP. What potential damage could this cause? Twice the voltage sounds like it could be quite bad, though I suppose proper fusing should avoid anything catastrophic.

Does anyone know of any way to prevent both inverters being turned on at the same time? Some sort of failsafe relay that won't allow power to one unit while the other is on? Or maybe an alarm if preventing power isn't possible.

As I said, the small inverter will only be providing power via the units on board outlet. It will feed an extension cord to one, max two outlets in my van. The MP will feed my AC breaker panel.

Thanks

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shaneyake avatar image shaneyake igvan commented ·
As long as there is no electrical connection between the outputs of both inverters there won't be a problem. If you are going to feed outlets then those outlets can only be feed from one inverter and must have no connection to the other one.


Most like the inverters will trip in overload if you accidentally connected the 2 together. Victron inverters are pretty robust but they could die.

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igvan avatar image igvan shaneyake commented ·
Thanks for the reply, @shaneyake

The outputs from the inverters will most definitely be isolated, outlets will only be powered from one or the other inverter, no connection at all between the two. One, maybe two outlets will be direct wired to the Phoenix 500 watt inverter. All other outlets will be run off of the MP, via the AC distribution panel. No chance they would get crossed or connected in any way.

They will obviously both be hooked to the Lynx Distributor and drawing from the same battery bank. Even if they were both at max output, the batteries in theory could keep up given their discharge rating. This will never happen, but for sake of idiot proofing, all that is accounted for.

So this sound totally fine to you? Thanks much for your thoughts.

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igvan avatar image
igvan answered ·

So is the consensus here to just keep it very simple and go battery to battery, and then main pos and neg coming from opposite ends of the bank? I guess I’m fine with that, it’s how I initially had it set up, I just thought best practice was fusing each battery and connecting down line?


Thanks

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