Inverter Max Input Amps, Generator size, cable size?

[chulew]

I’m looking to replace my 24V Magnum MS4024PAE inverter with two of the 4448 (48V) versions (stacked). I will use a 240V generator TBD for charging my bank. What should my inverter setting be for Max Input Amps if I want to charge at the max continuous 60ADC (x2=120A for stacked) and the rest of the available power used to run loads (assume continuous).

I have the ME-RTR remote/router already and for my existing single MS4024PAE it has a max Input Amps limit of 60. Will this setting maximum change based on having 2x4448s instead? The AC Input limits for 240V starts to confuse me is why I'm asking.

Once I know the max Input Amps my setup can utilize, I can figure out my generator to inverter cable size (~22') and choose a generator.

Spec Sheet is below and here is the link to the manual for both 24V & 48V: https://www.dropbox.com/scl/fi/e81e...4PAE.pdf?rlkey=4u4yoqfhs0qda17e5of3xjszx&dl=0

Thanks in advance!

 

[MisterSandals]

What should my inverter setting be for Max Input Amps i

Just so you know, the inverter pulls the amps. I think any setting for amps would be max charging amps.
The number to watch for input is volts.

But for input to supply your desired charging amps: 120A x 28V charging = 3360W (sorry i always got the long way around)
3360W / 240Vac = 14A from your generator

 

[chulew]

Just so you know, the inverter pulls the amps. I think any setting for amps would be max charging amps.
The number to watch for input is volts.

But for input to supply your desired charging amps: 120A x 28V charging = 3360W (sorry i always got the long way around)
3360W / 240Vac = 14A from your generator

I really appreciate you showing your work (calculations) as that helps me a lot but the manual shows Input Amps is a Shore Power setting, not a charger setting. It tells the charger when to start backing off to support the loads.

To clarify, I'm looking for Max Input Amps (AC) based on the max power two stacked inverters could pull in continuous operation while trying to charge the bank.

 

[MisterSandals]

To clarify, I'm looking for Max Input Amps (AC) based on the max power two stacked inverters could pull in continuous operation while trying to charge the bank.

That’s what I calculated but at 28V rather than the nominal voltage your attachment shows (17.5A AC per leg).

 

[chulew]

That’s what I calculated but at 28V rather than the nominal voltage your attachment shows (17.5A AC per leg).

I think I'm confused, my apologies. You used 28V but I'll be charging up to ~54.4V @ 60Adc for each of the two new 48V inverters so 120Adc max charge.

So 120A*54.4V=6528W?
6528W/240V=27.2A just for charging.
(4000x2)-6528=1472W remaining for loads while charging?

So 8000W / 240V = 33.3A AC (per leg?) this is where I get confused. So I need a generator that can output 33.3A AC @240v in order the handle max charging and still pump the well (~1300 watt)?

So AC Input Amps setting = 34A?

And how does 85% charger efficiency and power factor >0.95 figure in?

Thank you!

 

[MisterSandals]

Sorry, I missed the switch to 48V. Your math looks right.

So AC Input Amps setting = 34A?

This does not make sense that there is a setting in the 4448s for this.

What battery(s) do you have that will accept 120A?

The 85% efficiency and .95 power factor increase input requirements by 15% and 5% respectively.

The big question is whether you need 120A for your battery bank.

 

[RCinFLA]

Most LF hybrid inverters don't actually measure DC battery line current. Direct battery current measurement cost extra money in components.

They regulate charging current by inverter AC input voltage times inverter AC input current divided by inverter efficiency lookup table value to get charging power (pass-through AC loads not included). Then charging power divided battery voltage yields battery charging current. As battery voltage rises during charging the bulk charge current drops off a little.

Many low freq hybrid inverters also allow AC input max current control. Charging bulk current will be limited by either direct bulk charge current user setting or user set AC input current max allowed, whichever is less. If AC output loads eat up available user set AC input current limits then battery charging will be backed down to stay within user set AC input maximum AC current. If AC loads exceed user set AC input current limit then inverter will slide into supplementing the AC input current shortfall from battery power. Great feature when running from a generator to avoid overloading generator.

AC sourced battery charging on LF inverters has fairly good AC input power factor in the 0.92-0.95 range. There is no supplied charging current for short period where transformed down AC sinewave voltage valley falls below battery voltage which limits the peak power factor value and also results in a bit less maximum charging power compared to inverter's forward power, battery to AC output capability.

 

[chulew]

I wish these would tap the battery bank to keep generator from overloading but it only limits charging to run loads.

I have 12 x 24V 50Ah LiFePO4s in parallel. I will reconfigure them as 6 series strings of 2. Charge rate is 0.5C, currently 6 hr empty to full @ 100A DC. How will this change my charging scheme? I figured it out once before but I've forgotten. Double the voltage, same current for 2 series is the same charge time?

 

[MisterSandals]

I will reconfigure them as 6 series strings of 2.

12 x 24V x 50Ah = 14400Wh no matter how arranged

2S6P? Which would be a 48V at 300Ah battery (14400Wh still)

.5C on a 300Ah battery is 25A
25A x 48V = 1200W charging

Double the voltage, same current for 2 series is the same charge time?

Half the charge time

24V x 100A = 2400W charge rate
14400Wh / 2400W charge rate = 6h

48V x 100A = 4800W charge rate
14400Wh / 4800W = 3h

 

[chulew]

12 x 24V x 50Ah = 14400Wh no matter how arranged

2S6P? Which would be a 48V at 300Ah battery (14400Wh still)

.5C on a 300Ah battery is 25A
25A x 48V = 1200W charging


Half the charge time

24V x 100A = 2400W charge rate
14400Wh / 2400W charge rate = 6h

48V x 100A = 4800W charge rate
14400Wh / 4800W = 3h

Fantastic! This is really helpful. I'm learning how to do these calculations the way they make the most sense (easy)!
I thought that doubling my charger capacity should cut something in half. I can also then avoid running new cable for more solar.

I know it's right by why is 0.5C on a 300Ah battery = 25A? (300*0.5)/6P=25?

I can quickly swap out the 24V inverter for one of the 48Vs:

48 x 60A = 2880W charge rate
14400 / 2880W = 5h (better than my current 6h charge time)

Eventually I'll stack the other one and bump up to 120A charge current.
So 48V x 120A = 5760W charge rate
1440Wh / 5760W = 2.5h (oh yeah)

How does actual bulk voltage affect these figures? Especially when I get to 54.4V just as the batteries top off?

Inverter is rated at 4000W so 8000W stacked / 54.4 = 147A but at 85% charging eff = 125A, close the 120A spec'd rating (60x2) so I think this makes sense. Or am I doing it wrong?

 

[MisterSandals]

I know it's right by why is 0.5C on a 300Ah battery = 25A? (300*0.5)/6P=25?

Heh, ya got me! Good catch, this is why I show my work!

.5C of 300Ah is 150A as I am sure you know.

 

[MisterSandals]

I can quickly swap out the 24V inverter for one of the 48Vs:

But once you make a 48V battery, the it becomes 150Ah

150Ah x 48V still 14400Wh
.5C x 150Ah = 75A (this is still a lot but more reasonable)

 

[chulew]

12 x 24V x 50Ah = 14400Wh no matter how arranged

2S6P? Which would be a 48V at 300Ah battery (14400Wh still)

12x 24V x 50Ah = 600Ah bank (it was late when you replied)

So S26P @ 48V = 300Ah = 150A max which is close for stacked 48V inverters with 120A total max charging.

0.5C @ 150A = 4h or 3.2h @ 120A (charger max)

 

[MisterSandals]

0.5C @ 150A = 4h or 3.2h @ 120A (charger max)

If you are charging a fairly complex battery at this rate, your battery wiring will need to be perfectly balanced and flawless.

For balanced wiring you should read the first 4 posts of this thread:

Calculation of parallel string battery currents

Hi, everybody! I'm a retired EE. I didn't want my EE skills to fade away after retirment, so I exercise them when I can. Whenever I see a non-trivial circuit analysis problem on one of various forums I frequent, I challenge myself to solve it. Recently I watched Will's video about current...

diysolarforum.com

 

[Jack Rabbit Off Grid]

I’m looking to replace my 24V Magnum MS4024PAE inverter with two of the 4448 (48V) versions (stacked). I will use a 240V generator TBD for charging my bank. What should my inverter setting be for Max Input Amps if I want to charge at the max continuous 60ADC (x2=120A for stacked) and the rest of the available power used to run loads (assume continuous).

I have the ME-RTR remote/router already and for my existing single MS4024PAE it has a max Input Amps limit of 60. Will this setting maximum change based on having 2x4448s instead? The AC Input limits for 240V starts to confuse me is why I'm asking.

Once I know the max Input Amps my setup can utilize, I can figure out my generator to inverter cable size (~22') and choose a generator.

Spec Sheet is below and here is the link to the manual for both 24V & 48V: https://www.dropbox.com/scl/fi/e81e...4PAE.pdf?rlkey=4u4yoqfhs0qda17e5of3xjszx&dl=0

Thanks in advance!

Have you already purchased the 4448’s? If not I would would look into a Schneider XW PRO or pretty much anything other then a Magnum product.

I have a 4448 I purchased in 2021 that came to me broken. Would never charge from day one. I purchased it prewired on the Mini Magnum panel so should have a 5 year warranty. Nope! tried to get it warrantied for over a year nothing but trouble. Email after email and calling leaving messages. Waste of time horrible customer service! I tried finding a service center to repair it for me. None of them wanted to touch it with a 10 foot pole. most stated they don’t have any parts and can no longer get parts. I finally gave up and searched the entire US for the parts to fix it myself. Finally found them in Tennessee $325.00. I also purchased another one on eBay a used 2010 unit to power my house while I fix the first one. That cost me another $1100.00.

There is another member on here that finally got a warranty replacement after months of complaining. It was made in Mexico and lasted 3 minutes Before it let out the magic smoke.

Magnum was a good company but not anymore. I too had a 4024 that was purchased new in 2007 and it’s still going strong. My neighbor now owns it.

rant over.

​

​

 

[chulew]

Have you already purchased the 4448’s? If not I would would look into a Schneider XW PRO or pretty much anything other then a Magnum product.

I have a 4448 I purchased in 2021 that came to me broken. Would never charge from day one. I purchased it prewired on the Mini Magnum panel so should have a 5 year warranty. Nope! tried to get it warrantied for over a year nothing but trouble. Email after email and calling leaving messages. Waste of time horrible customer service! I tried finding a service center to repair it for me. None of them wanted to touch it with a 10 foot pole. most stated they don’t have any parts and can no longer get parts. I finally gave up and searched the entire US for the parts to fix it myself. Finally found them in Tennessee $325.00. I also purchased another one on eBay a used 2010 unit to power my house while I fix the first one. That cost me another $1100.00.

There is another member on here that finally got a warranty replacement after months of complaining. It was made in Mexico and lasted 3 minutes Before it let out the magic smoke.

Magnum was a good company but not anymore. I too had a 4024 that was purchased new in 2007 and it’s still going strong. My neighbor now owns it.

rant over.

​

​

I already have two Magnum 4448s to replace the 4024.

 

[chulew]

If you are charging a fairly complex battery at this rate, your battery wiring will need to be perfectly balanced and flawless.

For balanced wiring you should read the first 4 posts of this thread:

Calculation of parallel string battery currents

Hi, everybody! I'm a retired EE. I didn't want my EE skills to fade away after retirment, so I exercise them when I can. Whenever I see a non-trivial circuit analysis problem on one of various forums I frequent, I challenge myself to solve it. Recently I watched Will's video about current...

diysolarforum.com

What do you consider a fairly complex battery?

I have 12x24V battle borns.

 

[MisterSandals]

12 big lithium batteries wired in any configuration is complex to me. Getting them wired properly has many facets. Its an incredible amount of energy.

This installation and incident came to mind:

Local Pittsburgh Solar Battery Fire

https://www.wtae.com/article/millvale-fire-sprezzatura-food-energy-hub/42708022

diysolarforum.com