How does an inverter/charger combo work with an external MPPT charge controller?

fisherman

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I'm looking at getting a Victron 100/50 MPPT charge controller for an offgrid 24v system I'm designing.

I want to have an inverter to power my 120vac items.

Also want to be able to plug my 2200w gas generator into the inverter to supplement load and/or battery charging at times. So looking at an inverter/charger combo unit.

So how does the charger portion of the inverter/charger work when you already have an MPPT charge controller in the system? I haven't seen anything for documentation or videos of this type of setup for offgrid.

Would someone be able to help explain how this setup would work?

Thanks
 

rmaddy

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You simply have two parallel charge sources. It's no different than having two solar charge controllers. It's a very common setup.

The only issue you have to work with is to ensure the combined charge current of all concurrent charge sources does not exceed the max charge current rating for your battery bank.
 

fisherman

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The only issue you have to work with is to ensure the combined charge current of all concurrent charge sources does not exceed the max charge current rating for your battery bank.

Thank for your reply. How would I find that rating? I would only have either 1x 24V battery or 2x 12V batteries in series to get my 24v

The Victron 100/50 MPPT would have 50A of charge current correct?
 

rmaddy

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The spec sheet for the batteries should state a max charge current. Which batteries exactly are you looking at?

A Victron 100/50 has a max battery charge current of 50A. But you can use VictronConnect to set a lower charge current if needed.
 

fisherman

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The spec sheet for the batteries should state a max charge current. Which batteries exactly are you looking at?

A Victron 100/50 has a max battery charge current of 50A. But you can use VictronConnect to set a lower charge current if needed.

I was looking at 1 or two of these Battleborn 24v batteries for my 24v setup: https://battlebornbatteries.com/product/cyber-monday-50ah-24v-battery/

Does Victronconnect work for the MPPT controller or just the inverter/charger such as the Multiplus 24/3000/70?
 

rmaddy

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I was looking at 1 or two of these Battleborn 24v batteries for my 24v setup: https://battlebornbatteries.com/product/cyber-monday-50ah-24v-battery/

Does Victronconnect work for the MPPT controller or just the inverter/charger such as the Multiplus 24/3000/70?
VictronConnect works with just about all Victron gear including the solar charge controller and the MultiPlus. Bluetooth is basically needed for it all to work. The SmartSolar MPPT has Bluetooth. The MultiPlus does not. You need to buy a Bluetooth dongle to make it work.

Oddly Battle Born doesn't show an actual max charge current. The manual states a "charge rate" of 0.5c. For a 50Ah battery that means only 25A of charge current. If you put two of those in parallel (which gives you a 24V 100Ah battery bank) then you can charge at 50A.

Keep in mind that a 3000W inverter on a 50Ah battery is a terrible mismatch. With a 3000W load you would fully drain the 24V 50Ah battery in about 25 minutes.

Make sure you do a full energy audit so you know how much battery capacity you really need. See:

 

fisherman

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Keep in mind that a 3000W inverter on a 50Ah battery is a terrible mismatch. With a 3000W load you would fully drain the 24V 50Ah battery in about 25 minutes.

Make sure you do a full energy audit so you know how much battery capacity you really need

Thanks I'm in the process of doing that.

Only reason I'm looking at the 3000w is to account for a 120v water pump (9A draw) surge which I agree is overkill as it'd only be running a few minutes a day. Everything else in the cabin will be very low consumption such as LED lights, router, laptop, etc.

Realistically I'll be more-so looking at one in the 1500-2000w range.
 

rmaddy

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Everything else in the cabin will be very low consumption such as LED lights, router, laptop, etc.
None of that needs an inverter. It's more efficient to run DC loads directly from the battery instead of going from DC (battery) to AC (via inverter) and back to DC (via a typical power brick). Something to consider.
 

fisherman

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None of that needs an inverter. It's more efficient to run DC loads directly from the battery instead of going from DC (battery) to AC (via inverter) and back to DC (via a typical power brick). Something to consider.
I could get a 24V>12V converter and power a few of those yes. The laptop has a 12v adapter but not sure on the router. Might also add a fridge so I'd need to see if it makes sense to go 12v or 120v there too.
 
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