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Louisvdw

SmartSolar 100V vs 150V vs 250V

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What are the reasoning why you would use the higher voltage MTTP against a cheaper one and do the reasons justify the price.
I'm looking at this from the point of view of someone just wanting to start into solar, trying to reduce the monthly electricity bill, without breaking the bank.

This is just looking at the solar part. Lets assume ESS with 48V battery and Multi.

If I look at the cheapest option for each voltage we have:

  • MPPT100/20-48V (max 1160W) @ ~R2500
  • MPPT 150/35 (max 2000W)  @ ~R5000
  • MPPT 250/60 (max 3440W)  @ ~R10000

 

  1. Before your panels can start charging the batteries, the voltage need to be more that the battery voltage. With only 2 panels (series) in the 100V MPPT, the 3 panels under 150V and 5 under 250V will start sooner. But how much difference does this make in practice?
  2. Will the wire cost make that much a difference to offset the cost if you need to do 4 panels (2s2p vs 4s)?
  3. Any features that the 100/20 might not have that could limit your system?
  4. Would the 150/35 (2000W @ R5000) be better or same vs. 2x 100/20 (2320W @ R5000 - having 2x MPPT trackers might be better also)

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47 minutes ago, Louisvdw said:

MPPT100/20-48V (max 1160W) @ ~R2500

Hi Maybe i am missing something, but according to all my records the 75 and 100 series is only for 12 & 24 volt systems. (unless there is a new model i am not aware off) 

47 minutes ago, Louisvdw said:

Before your panels can start charging the batteries, the voltage need to be more that the battery voltage. With only 2 panels (series) in the 100V MPPT, the 3 panels under 150V and 5 under 250V will start sooner. But how much difference does this make in practice?

Not much.

47 minutes ago, Louisvdw said:

Will the wire cost make that much a difference to offset the cost if you need to do 4 panels (2s2p vs 4s)?

The wire cost will  be double, because you will need to run 2 strings, and then you would need another two fuse holders, mc4 connectors, 2 fuses and a bigger combiner box, so its not just the wire cost. 

47 minutes ago, Louisvdw said:

Any features that the 100/20 might not have that could limit your system?

It can only work up to 24Volt

47 minutes ago, Louisvdw said:

Would the 150/35 (2000W @ R5000) be better or same vs. 2x 100/20 (2320W @ R5000 - having 2x MPPT trackers might be better also)

The max power indicated in the spec-sheet changes with battery types, so you might get 58 Volt times 35 Amps = 2030 Watts from the 150/35 when you have lead acid batteries, but only 53 Volt x 35 amp = 1855 watts from the same MPPT when you have Lithium batteries. So you need to know what batteries you are going to use before you decide. 

I love working with the 250 Volt series, less strings, thinner wires. Less components resulting in less possible failures. 

47 minutes ago, Louisvdw said:

I'm looking at this from the point of view of someone just wanting to start into solar, trying to reduce the monthly electricity bill, without breaking the bank.

This is a great way of thinking, but do remember, once you start, the chances are great that you will upgrade in the future, you dont want to add a second, and a third mppt while you can buy a bit bigger now, at the current price and allow for some upgrading in the future. 

Not one person I have ever met, that started small, stuck to their small system much longer that 6 months... 

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25 minutes ago, Jaco de Jongh said:

Maybe i am missing something, but according to all my records the 75 and 100 series is only for 12 & 24 volt systems. (unless there is a new model i am not aware off) 

It looks like the 48V has been on the market for a while. I'm not sure when it was released, but they have special mention of the 48V 100/20 in the Datasheets (and I also see it in the prices at different places) https://www.victronenergy.com/solar-charge-controllers/smartsolar-mppt-75-10-75-15-100-15-100-20

 

25 minutes ago, Jaco de Jongh said:

The max power indicated in the spec-sheet changes with battery types, so you might get 58 Volt times 35 Amps = 2030 Watts from the 150/35 when you have lead acid batteries, but only 53 Volt x 35 amp = 1855 watts from the same MPPT when you have Lithium batteries. So you need to know what batteries you are going to use before you decide. 

Interesting, but logical. I did not think of that. I was just quoting max values according to the datasheets.

 

25 minutes ago, Jaco de Jongh said:

I love working with the 250 Volt series, less strings, thinner wires. Less components resulting in less possible failures. 

This is a great way of thinking, but do remember, once you start, the chances are great that you will upgrade in the future, you dont want to add a second, and a third mppt while you can buy a bit bigger now, at the current price and allow for some upgrading in the future. 

Not one person I have ever met, that started small, stuck to their small system much longer that 6 months... 

I can see the 250V benefit with less stings, although if you do upgrade/go bigger at some stage then I guess you will add some extra strings in parallel which will bring you to extra connectors, fuses, etc.
 

Are you saying the extra cables, connectors, fuses, etc. do cost more than the larger MPPTs, or is it more a benefit of the less messy setup?

 

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Posted (edited)
2 hours ago, Louisvdw said:

or is it more a benefit of the less messy setup?

Benefit, ease of installation and reduction in possible failure points.  

 

2 hours ago, Louisvdw said:

It looks like the 48V has been on the market for a while.

Never saw them, my supplier dont even sell them. Learned something new today.. 

 

2 hours ago, Louisvdw said:

Are you saying the extra cables, connectors, fuses, etc. do cost more than the larger MPPTs,

No, not at all,just mentioning that so you can keep in mind that isn't only cable costs involved. 

 

Edited by Jaco de Jongh

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21 minutes ago, Jaco de Jongh said:

Never saw them, my supplier dont even sell them. Learned something new today.. 

Even I learned something new 🙂 I also didn't know there was a 48V model below the 150/35. It's definitely new(ish).

3 hours ago, Louisvdw said:

Before your panels can start charging the batteries, the voltage need to be more that the battery voltage. With only 2 panels (series) in the 100V MPPT, the 3 panels under 150V and 5 under 250V will start sooner. But how much difference does this make in practice?

In my experience, the difference you make in starting up earlier will not make up the extra cost in any short amount of time.

3 hours ago, Louisvdw said:

Will the wire cost make that much a difference to offset the cost if you need to do 4 panels (2s2p vs 4s)?

Depends how far the wires need to go. I spent R1000 just on PV cabling for a PV-array that's 25 meters away. Now imagine having to spend twice that because you have two strings, or going with thicker cabling.

3 hours ago, Louisvdw said:

Any features that the 100/20 might not have that could limit your system?

There are hardware differences. The higher end models have a hardware current clamp, which means it handles overcurrent events differently. The smaller units (which will include the 100/20) stop charging and restart from zero, while the other models will clamp the current in hardware and keep going (thereby creating more power). This is not a significant difference, it only really has an effect if 1) you significantly oversize the PV array, like more than 20%, or 2) you frequently have cloudy weather that produces cloud flare effect.

Also, all of the models derate when they get hot (over 40 °C), so even though it is rated at 20A, it may well run at only 18A or so on a hot South African summer's day. So running the smaller 20A charger at full capacity will make less than the 150/35 that's running with the same amount of PV.

3 hours ago, Louisvdw said:

Would the 150/35 (2000W @ R5000) be better or same vs. 2x 100/20 (2320W @ R5000 - having 2x MPPT trackers might be better also)

The 150/35 is also one of the "smaller" controllers, without the fancy hardware clamp. So depending on the cable distance to the two strings, there is a compelling case for going with 2 x 100/20 in this case...

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Thanks @Jaco de Jongh, @plonkster.
Really helpful feedback so far.

In the southern cape where I am we do get a decent amount of cloudy days, but temperatures rarely get too high.  
On the MPPT calculator I should reach the 20A max on min temperatures (which never happens), so my expectation is around ~18A

image.png.780ea3c0d9dbe44c12b0013af06a487b.png

 

PS. If I look at the calculator version history, the 100/20 48V was added on V2.8 (still don't know what date that was)

 

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