MNDIY 48V series inverters operating voltage

Started by dapdan, January 20, 2022, 10:48:26 PM

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dapdan

Hi Midnite,

Can any one confirm the operating DC voltage range for the 48V series as I want to use a Li-ion battery with the upper voltage going as high as 67V. I could limit it to 66V and still get useful capacity from the battery its native 16s configuration. I have a Schneider and Magnum that go up to 68V but I dont want to use these inverters as the DIY line has its built in mppt CC that will streamline the installation. I also want a new inverter to play with. Magnum and Schneider are quite boring now. I cant find any information of the specification of the 48v inverter. The 24V variant goes up to 33V so I was hoping the 48V would  be twice the 24V and be at 66V. I have not found any info to confirm my hopes.

Damani

Wizbandit

I just tested a DIY3548 and it shutdown at 59.8V
The manual says Battery Over Voltage is 60V, I didn't quite get there...
The manual also says it is settable up to 60V but I can'r find the parameter that sets it.
I will have to look and see if I can find a MODBUS register that holds the value.

dapdan

Whiz,

Thanks. It would be quite usefull if it had a higher limit of around 68 like the Schneider, outback and magnum. that limit gives the flexibility needed when setting up DIY, second life lithium batteries that could range in setup between 12s and 16s for the two main chemistries that vary in charging voltage of 3.75V and 4.2V per cell (effectively ranging between 50.4V and 67.2V).

dapdan

Wiz,

I also just realise that if you were equalizing batteries you inverter would shut down before you get to your EQ for lead acid being around 62V. Thats a real shame. Midnite really need to have this upper voltage increased to at least 64V for the lead acic folks.
4

boB

Quote from: dapdan on January 21, 2022, 05:57:46 PM
Wiz,

I also just realise that if you were equalizing batteries you inverter would shut down before you get to your EQ for lead acid being around 62V. Thats a real shame. Midnite really need to have this upper voltage increased to at least 64V for the lead acic folks.
4

The DIY inverters SHOULD be able to run up t 63 or 64 volts actually.  We may need to have "the talk" with them.
I remember Sol-Ark's Chinese inverter only went up to 60V before they had Deye make them specify up to 63 or 64 VDC

Where do you see those max DC voltages up to 68V, Dan ?

Usually these inverters use a 63V rated electrolytic.  Magnum specifies  36 - 64 VDC  on its  MS PAE inverter.
Haven't looked at the others you mentioned yet.

Our own inverters will be rated to 64 volts though.

boB






K7IQ 🌛  He/She/Me

dapdan

boB,

Thanks much. I have a Magnum PAE 4448 and the specs say 36 - 68V input. A youtuber who has a outback 3648 is running a 16s Li ion config and the specs note on the inverter also show it runs up to 68V. My Schneider Conext 4048 also shows it can run up to 68V.

It would be great if you could have your inhouse 24V and 48V inverters run up to 34V and 68V respectively as this would allow DIYers to use second life Li-ion packs up to their common native module config which tend to be 16s (which needs charging up to 4.2V/cell which works out to be 67.2V). I am not realising this as I phase out my old lead acid to second life Li-ion (I am using some BMW and Ford packs) these tend to come in 16s or 4s modules. If you try to remove a cell you lose the factory compression set up and would then potential lose some cycle life and have the messy task of trying to cut away cell that are usually welded at cell level with aluminium bus bars. So it would be really nice if you guys would have your inverters going up to 68V. This would be a deal breaker for me and it would be sad as I am a Midnite fan and believe in your products. Please also ensure that all of your CC has the constant voltage charging protocol that Li batteries require.

Your MN3524DIY going up to 33V is actually a better fit for a Li-ion 8s config. I could restrict the charging per cell to 4.1V and charge at 32.8V battery level and that could work for me. Trouble is I am having difficulty sourcing one. My usual source, Altestore, says that this inverter is on backorder and I really need one right away as I am consolidating a shipment to myself in Barbados through Miami. Any guidance or assistance on this would be appreciated boB.

Thanks again.

dapdan

boB,

I was just checking magnum manual and we are both right. the summary specs does say 64V but the detailed manual says HBCO is at 67.6V on page 35. It has the 24V variant HBCO at 34V which is good for Li-ion applications. In the same summary spec sheet it says absolute max for 48V is 68V and for 24V is 50V! wow. That last one is astonishing.

So we are both right. I can tell you when I get my second life Li-ion I will be testing them against these elevated voltages and see how it goes. I really think this is the direction that inverters should go because the second life Li-ion market is has been really taking off in the past few years and EV generally use the Li-ion poly chemistry batteries that are 3.7nominal and 4.2 fully charged as opposed to the 3.2nominal and 3.7fully charged of the LiFePo4 chemistry. You guys need to ensure that your gear and accommodate all of the chemistries and configurations that are out there.

Damani

dapdan

#7
here are the page from the manual








dapdan

All,

I can confirm that my conext sw4048 is configurable up 68V for the high voltage cut off as i just did it by going into the advance menu on the SCP. This schneider rig is more than 4yrs old and has not made a miss step in that time. Midnite you can't let schneider old kit put your  new one to shame. Come on guys Lithium is the future, either get on the train or be left at the station. Honestly, if your new kit doesn't do at least 68V HVCO i will have to stick with the conext SW4048 until a better one comes along. I cant regress.

Damani

boB

Quote from: dapdan on January 22, 2022, 08:58:27 AM
All,

I can confirm that my conext sw4048 is configurable up 68V for the high voltage cut off as i just did it by going into the advance menu on the SCP. This schneider rig is more than 4yrs old and has not made a miss step in that time. Midnite you can't let schneider old kit put your  new one to shame. Come on guys Lithium is the future, either get on the train or be left at the station. Honestly, if your new kit doesn't do at least 68V HVCO i will have to stick with the conext SW4048 until a better one comes along. I cant regress.

Damani

So, which lithium batteries are you using that needs to go above 64V ?   That would be unusual for Li chemistry.

I can definitely see that for Nickel-Iron batteries though.

So, what Schneider has evidently done is to have blessings from their capacitor manufacturer that they can run continuously at 5 volts above the capacitor's ratings.  I'm sure that the 24V inverters use 50V electrolytic rated capacitors so they don't have to do anything special there.

24V inverters high voltage specs aren't just half of a 48V specifications as far as the capacitor ratings.  For example, there are no 31.5V electrolytic caps.

Running at 64V continuous is technically an over-voltage for a 63V cap but 1 more volt and should be OK.

The thing about electrolytic capacitor voltage ratings are that they almost ALWAYS allow higher voltage for a surge.  That is not a big issue.
I'm sure that these caps can take an over-voltage but that actual rating can change from individual cap to cap and probably batch to batch as an absolute limit.

I'm pretty sure the DIY inverters can also stand at least 68V surges because of capacitor ratings.  I think that the Chinese are just scared of going too high for some reason and don't really understand the markets where a bit higher voltage is needed for people like you and me.

As for HVCO of 68 volts, I'm sure that is because the surge is OK for those voltages but it is difficult to accurately cut-off at exactly 65 volts because of noise, etc...  So, they just chose a number.

On the Schneider, can you actually choose to Absorb or EQ at 68 volts or 67.7V ?

We will still ask SRNE about this higher voltage rating spec.  I know that Sol-Ark, also made in China raised their voltage from maximum of 60 volts which is obviously not high enough for 48V batteries.

boB





K7IQ 🌛  He/She/Me

Robin

I can't speak much for second life lithium batteries. They are typically Lithium Ion rather than Lithium Iron Phosphate or Ferro Phosphate. We look at the more common batteries that are sold into the renewable energy market and make sure we can support them. Some of the Schneider inverters go to 68V and some only to 64? We had planned on supporting up to 64V on our Rosie and B17 because of the available batteries out there. 68V is extremely high, but we will see what compromises come into play to go higher than 64V? I can't say what those compromises are at the moment, but a couple things do come to mind.
1. Capacitor ratings. The industry standard is a 63V electrolytic. Like Bob said it is not a big deal to allow 64V, but going all the way to 68 will require a lot of thought and checking with the electrolytic manufacturers. We use four brands of electrolytics now. I doubt they will say go ahead and overvoltage their parts. So that puts us into the next voltage range which will give us less capacitance. Less capacitance may affect the way things work?
2. working voltage range. Since our inverters use a transformer we are tied to a range (turns ratio) that the inverter can run up and down to. It may be that in order to support 68V instead of 64, we would have to short change the lower operating voltage. I believe it is presently 40 on the Rosie and B17. I don't know about the DIY. Making changes like that are not trivial, but we will ask what can be done on their end if anything.
There are all sorts of circuits and design related criteria based around 64V. In order to get the attention of the DIY manufacturer first we need to get their attention on this subject. They too may not be concerned about supporting Lithium Ion batteries as they are not a very safe battery. That is why all the commercial batteries are something else. Lithium Ion will yield the most energy for the size for sure. That's why cars use them, but the commercial Lithium battery companies are not using that chemistry. The normal operating voltage of a 16 string lithium iron phosphate is 51 or 52 volts. That is a far cry from 64 or 68. But, like I said, I will ask what tradeoffs would be required in order to go above 64V? We will have to look at each inverter design and see just what if anything can be done to accommodate a higher DC voltage.
I did a quick search on the internet for Chinese high frequency inverter specs. I was not able to find one that went above 62V? I did not look at everything though. Vokek, Sungold and  Sigineer. I could not find the specs for Growatt?

Thanks, Keep the comments and questions coming.
Robin
Robin Gudgel

dapdan

Rob/boB,

Thanks for the the extremely detailed and technical response. This is why Midnite is my number one. I have been researching the lithium battery second life market for a bit now and it is 99% EV batteries where they prefer the higher energy density of the Li-ion chemistry which in turn requires a charge or 4.1/2 per cell. Right now your can get second life li-ion between $100 and 150 per kwh storage, LiFeP04 is still on average above $200/ kwh. Most manufacturer seem to be either at 4s\8s\16s hence why we are at 16.8/33.6/67.2V. You could break open the modules and go down to 3s/7s/14s/15s however you will lose the compression of the native module as some come in a metal enclosure and then you have to be cutting welded cell tabs etc. I am not really keen of the last two points this is why I am on the hunt for an Inverter that can go to that upper limit. The production of LifeP04 will not approach the volume production of EV and therefore Li-ion will always tend to be cheaper. In fact it is the EV market that really started the downward pressure on the price of lithium batteries as it caused production to be ramped up and brought it to the masses. It like off grid panels versus grid tie panels.

I am just happy that talented and smart people like yourselves are will to listen to the DIYers working in their garage or basement.

Damani