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Combination of MPPT and lithium batteries?


Party Plant
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I have To replace my old bank of batteries (Dixon 105Ah - 3 string of 4).

I was thinking of getting the Pylontech US3000 3.5kWh (hoping to get away with 2). I have 2 x MLT Oasis 448 inverters (working in parallel) and believe the batteries will work with them.

However, I’ve been told that my WRND Proseries 48 (150V, 120A) might not work properly with the Pylontech.

Can this be so? If so, why? What do I need to know about MPPTs charging lithium batteries? I know WRND does not have a great reputation, but I have not noticed any problems with it and don’t want to spend on a replacement if I don’t have to.

any advice?

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1 hour ago, Party Plant said:

I know WRND does not have a great reputation

It's always difficult to "review" a product, because there tends to be a bit of a reverse survivor-bias (loser-bias). I disassembled one of their failed units some years ago to see what it was like. Now the trouble with that is 1) it was a failed unit, so maybe I got the Monday unit as they say, 2) it is quite possible that quality has improved since then.

But with that disclaimer out of the way... the unit I disassembled scared the heck out of me. The design itself is not bad. It's a synchronous buck converter. To build bigger units, they put more inductor+FET boards in parallel (all driven by the same logic), which is exactly how some others (eg Microcare) does it. Nothing bad up to that point. The assembly was just absolutely atrocious. The FETs had no mica insulation waver to the heatsink (also the body of the unit) for example, it seems it relied only on the paste to provide insulatio. This is important, because the drain of the FET is tied to the back tab and a short to the body would short out one side of the buck converter. Locking washers were used directly on some of the power boards in a way that scraped the copper off the copper pads. The main battery bolts were isolated from the metal case by slivers of double sided tape. There are no fuses in there (to protect at least the microcontrollers and other non-main-current circuitry). It was so bad I could never in good conscience advise anyone to ever use one.

But... maybe it was just that one. IDK.

Edited by plonkster
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@Party Plant quick question, can you adjust the charge settings on the WRND? 

Then other thing, if you going to upgrade to new MPPT, then go for the MLT MPPT because it can connect with the Oasis and communicate with it and it's got all the lithium settings already on it. 

Victron wil work nice with it to, i spotted some people doing it. I'm running a Microcare mppts on my MLT powerstar  but it's limited to adjust te settings super low but I'm running i DiY lifepo4 setup so it's fine for mine.  

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On the WRND MPPT I can adjust float volts, current limit, equalize voltage (also duration and frequency), boost voltage (also duration), boost equalize end amps, and PV 60.0Vmp.

The MLT Nomad MPPT looks like it would make things simpler 

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2 hours ago, Party Plant said:

On the WRND MPPT I can adjust float volts, current limit, equalize voltage (also duration and frequency), boost voltage (also duration), boost equalize end amps, and PV 60.0Vmp.

Sound like they copy the Microcare stuff. 

Just give MLT a call, you order direct from them and they add the extras with it. http://mltinverters.com/wp-content/uploads/2018/07/Nomad-spec-2018-07-11.pdf

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3 hours ago, Gerlach said:

Sound like they copy the Microcare stuff. 

Maybe in function, but completely different MCU. Microcare uses a PIC, WRND has something else,  I think it was ATMEL but it might have been some ARM thing.

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1 hour ago, plonkster said:

Maybe in function, but completely different MCU. Microcare uses a PIC, WRND has something else,  I think it was ATMEL but it might have been some ARM thing.

Thanks for the correction there, jip, i actually ment the function part. The inside looks different, spotted when you posted the inside of one you took appart.

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