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5kva Axpert with Lithium only for UPS


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Hi Guys

After some research and a few quotes from installers, I've decided on this basic system - Axpert 5kva 48v with 2.4kw Lithium. 

I plan to install myself and have COC done professionally. 

The purpose initially is only as a Ups. 

Question - should I be considering MPPT vs PWM when selecting the inverter? Also, is there a configuration for the inverter that would best suit the battery - I'm thinking charge rate specifically. 

 

Tx 

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1 hour ago, RyanBM said:

Axpert 5kva 48v with 2.4kw Lithium.

2.4 kWh of lithium (50 Ah) is very light for a 5 kW inverter; probably too light.

1 hour ago, RyanBM said:

should I be considering MPPT vs PWM when selecting the inverter?

It won't matter too much now, but if and when you run panels, you'll much prefer MPPT, even though it costs a little more. MPPT firmware is also more common, so if you need an update or patched firmware, it is more likely to be available without having to beg for it from your supplier.

Some people prefer PWM and claim better efficiency, but for a house installation, you usually want many panels, and much prefer to wire at least pairs of them in series. For PWM, all the panels have to be paralleled (as far as I know).

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9 minutes ago, Coulomb said:

2.4 kWh of lithium (50 Ah) is very light for a 5 kW inverter; probably too light.

It won't matter too much now, but if and when you run panels, you'll much prefer MPPT, even though it costs a little more. MPPT firmware is also more common, so if you need an update or patched firmware, it is more likely to be available without having to beg for it from your supplier.

Some people prefer PWM and claim better efficiency, but for a house installation, you usually want many panels, and much prefer to wire at least pairs of them in series. For PWM, all the panels have to be paralleled (as far as I know).

Tx Bud- why do you say the 2.4kw maybe too lite?

 

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On 2021/01/26 at 11:50 PM, RyanBM said:

it should read 3kva not 5kva

Ok. It's still on the light side; a single US2000 is comfortable with 25 A continuous discharge, or less than 25 x 50 = 1250 W at the load. With occasional bursts to twice that, or less than 2.5 kW.

Edit: also be aware that most (not all) 3 kVA inverters are 24 V, and most Pylontech battery modules are 48 V. 

Edited by Coulomb
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Hi

Plan on going a similar route for loadshedding. Lights + Tv + Amp + alarm + network = 500w ish

5kva Axpert VM iii + 3.5kWh PylonTech US3000 (maybe 2 x US2000) Should get about 5 hrs. 

Will add panels later (maybe sooner rather than later if Eskom gets their 10% increase) .

Chose the VM iii because it will supplement with utility if the PV isn't enough and it has a wide voltage for the mppt. 

@RyanBM, have you decided on the invertert yet? 

Looking at this

Kodak 5kva Backup Kit

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If you guys are going for load shedding backup, lead acid batteries are totally fine since you are only doing 2 hours at a time.

I've been running for roughly 3 years now on my current set of lead acids and they are still going well.  It is roughly R10k to replace them which I budgeted to replace every 3-4 years.  The fact that lithium batteries are more complicated to install with the Axpert, more expensive and also age, I don't think it makes sense.

My 2 cents.

Edited by Gnome
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3 minutes ago, Gnome said:

If you guys are going for load shedding backup, lead acid batteries are totally fine since you are only doing 2 hours at a time.

I've been running for roughly 3 years now on my current set of lead acids and they are still going well.  It is roughly R10k to replace them which I budgeted to replace every 3-4 years.  The fact that lithium batteries are more complicated to install with the Axpert, more expensive and also age, I don't think it makes sense.

My 2 cents.

Thanks. 

Financially it makes sense. 

I plan on adding panels at some stage. Does that make a difference? 

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1 minute ago, swazz99jhb said:

Thanks. 

Financially it makes sense. 

I plan on adding panels at some stage. Does that make a difference? 

Yeah, I'm using mine only as a UPS, not panels.  If you are going UPS only, I think lead acid makes sense.  Since I have no experience dealing with panels, I can't answer for you what is best suited there.  But lead acid doesn't deal well with being discharged for long periods.  So I think there lithium is definitely the better option when you are thinking of going off-grid or partially off-grid.

The financial input for a system with and without panels are completely different.  You can do a UPS backup that allows 2-4 load sheddings a day for relatively low cost compared to what you need to put in to go off-grid or even partially off-grid.

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  • 3 months later...
Posted (edited)

@RyanBM

Maybe too late but here's my thoughts..

Definitely MPPT - far superior to PWM. Having run both I'd never go back to PWM.

Re the batteries:

I've run with lead acid (GEL) batteries for the last 15 years - 900Ah, 24V. Now the batteries have been replaced (they lasted pretty well and have now been relegated to run my greenhouse).

I've now replaced them with Lithium (Pylontech) - why?

1. They have a greater discharge capacity (can go as low as 20% or 5% for the newer US3000C 48V version)

2. If you decide you want more storage then just plug in another battery (impossible with lead acid)

3. Much neater in their cabinet - I had gel batteries but liquid ones need regular maintenance.

4. I can communicate with the BMS so I know exactly how they are performing and if I need to charge them.

Price wise there isn't a huge difference.

Edited by Acuario
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