PIP inverter repairs and hardware modifications

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offgridQLD
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Re: PIP inverter repairs and hardware modifications

Post by offgridQLD » Thu, 18 Jun 2015, 19:18

"Using 15 lifepo4 would get around the prog 29 48v maximum "

"With 15 lifepo4, could set 29 to 46.5, 26 to 53.5 and 27 to 49.5 and fine tune from there. Do you see any problem with that setup"

Why is 48v LVD for a 16 cell a problem? It would give you 3v a cell. I don't see any issue with that as I don't think you would see that kind of voltage on a sizable lifep04 bank with just a PIP4040 and it's max loads it would apply to the cells. At least not until the cells were at a very low SOC.If SOC gets so low that your seeing that kind of voltage then   you would want the inverter to disconnect anyhow.

46.5v and 15 cells is only 3.1v I think that's probably a bit unnecessarily high for a LVD of the inverter. I have it set at 3v pr cell but I also have cell level Low voltage disconnect so I am not relying on the inverter monitoring the entire bank voltage so I can afford to use tighter safety margin for the inverter LVD .

But like I said in my first post unless your using small banks and trying to use the full capacity of the bank regularly then nuance LVD events under load are not a big issue with Lifepo4.

Just as an example my PIP4048 running from a tiny 40AH 16 cell lifepo4 bank) will run a 2200w load with program (29) set at 48v LVD all the way down until about 10% SOC ..perhaps even a bit less befor I trigger the LVD on the inverter. So you can imagine how stiff the voltage is on a 400ah bank.

Kurt
Last edited by offgridQLD on Thu, 18 Jun 2015, 09:37, edited 1 time in total.

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Re: PIP inverter repairs and hardware modifications

Post by solamahn » Thu, 18 Jun 2015, 19:45

Good. Thanks. I was going to get 2 lots of 16 lifepo4 for 2 jobs, then thought of just get 2 x 15 but now, I will go back to 2 x 16.
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Re: PIP inverter repairs and hardware modifications

Post by weber » Thu, 18 Jun 2015, 22:42

Welcome, solamahn. It's great to hear what the common faults are. Also great to hear that MPP Solar is listening and fixing problems.

Here are two posts on our fan replacement. But this was all about noise, not corrosion. The first gives the specs and the model we used. The second gives the replacement method.
http://forums.aeva.asn.au/viewtopic.php?title=pip4048ms-inverter&p=54806&t=4332#p54806
http://forums.aeva.asn.au/viewtopic.php?title=pip4048ms-inverter&p=54866&t=4332#p54866

Kurt, solamahn has apparently already read my post about our cap and MOSFET upgrade. For those who may have missed Kurt's edit -- full specs for the parts are given here:
http://forums.aeva.asn.au/viewtopic.php?title=pip4048ms-inverter&p=56103&t=4332#p56103
It more than doubled the voltage headroom of both the caps and the MOSFETs relative to our maximum bulk/absorb voltage of 55.2 V for 16 x LiFePO4 (3.45 Vpc).

Kurt, 3.0 V per cell corresponds to a near-zero state of charge when the LiFePO4 cell is only under light load. So 48 V is too low for a low voltage cutout with 16 cells. So solamahn's suggestion of using 15 cells is good in that it gets that up to 48/15 = 3.2 V per cell. We might then be able to make it load dependent by sending serial commands to vary it on-the-fly.

I note that our float voltage is 53.8 V for 16 cells. That's 3.36 Vpc. With 15 cells we'd need to use 50.4 V. But that's well within the PIPs float voltage range. Bulk/absorb would be 51.8 V which is likewise fine and would give the caps and MOSFETs another 3.4 V of headroom.

I don't know why we didn't think of dropping to 15 cells ourselves. I don't understand your objection, Kurt. Please try to explain further.

Anyone else see any problems with using only 15 LiFePO4 cells with the PIP?

The PIP4048MS manual is here
http://www.mppsolar.com/manual/PIP-MS%201-5K%20manual.pdf

[Moderator note: Subsequent exchanges with solamahn at this time can be found here.]
Last edited by weber on Thu, 18 Jun 2015, 12:49, edited 1 time in total.
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Re: PIP inverter repairs and hardware modifications

Post by solamahn » Wed, 24 Jun 2015, 14:31

This is what I found in the 3248/4048 service manual.
ALL of the mosfet are 11-320110-00G (MOSFET IR/IRFB3307ZPBF 120A 75V N BULK TO-220).* *: In the new version, they will be 11-320138-00G (MOSFET TI/CSD19505KCS 201A 80V N BULK TO-220) or 11-320117-00G (MOSFET IR/IRFB3077 210A 75V N BULK TO-220)
No wonder I am having so many 4048 mosfet failures. I think it's a combination of full batteries not aiding much to voltage regulation, the undersize mosfets and perhaps variation in solar input current and load.
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Re: PIP inverter repairs and hardware modifications

Post by Scott » Fri, 17 Jul 2015, 01:22

Does anyone know the pinout of the RJ45 communication port by any chance? Is there any power available on there?

I see there's a remote display panel available that doesn't need external power as long as the inverter has dry contacts. My hunch is that there's 12V on there but want to see if there's any concrete info before I go poking around.

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Re: PIP inverter repairs and hardware modifications

Post by coulomb » Fri, 17 Jul 2015, 13:47

Scott wrote: Does anyone know the pinout of the RJ45 communication port by any chance? Is there any power available on there?
Yes and yes. It seems that while there is a perfectly good standard for RS232 on RJ-45 EIA/TIA - 561, the PIP does NOT use it. So this is a non-standard cable.

There is power, but it is not used by the provided cable. The provided cable uses only 3 wires, ground, TX and RX.

I could not find specifications on this; this was found by examining and buzzing with a multimeter:

[ Edit 2: This seems to be a 2013 model. The 2014 model seems to be different, with power on pin 4; see next post and Weber's confirmation. ]


+-----------+-------------+----------------+----------+
| Function. | RJ-45 pin # | D9 pin #       | Function |
| (PIP)     |             |(provided cable)|(Computer)|
+===========+=============+================+==========+
| SGND      | 8 --------- | 5              | SGND     |
| TD        | 1 --------> | 2              | RD       |
| RD        | 2 <-------- | 3              | TD       |
| +12V      | 7 (or 4)    | NC             |          |
+-----------+-------------+----------------+----------+


[ Edit: Weber pointed out in email that the TX and RX with respect to the DTE are confusing; he offered the above as making more sense. ]

The PIP is transmitting on D9 pin 2. At idle, you can measure ~ -11 V on D9 pin 2 with respect to D9 pin 5. The provided cable has a female D9 connector.

[ Edit: the RS232 port is isolated, so the "Ground" mentioned above is really a signal common. It is also the common for the 12 V power. I measured 11.9 V pin 7 to pin 8. ]

Note that the above could change at any time. Some newer PIPs seem to have a USB port as well as the RS232 on RJ-45 connector. Note that other (lower power) PIP models have *only* a USB port, no RS232 port at all.
Last edited by coulomb on Sun, 19 Jul 2015, 05:23, edited 1 time in total.
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Re: PIP inverter repairs and hardware modifications

Post by Scott » Sat, 18 Jul 2015, 00:04

coulomb wrote:
+-----------+-------------+----------------+
| Function_ | RJ-45 pin # | D9 pin #       |
|           |             |(provided cable)|
+===========+=============+================+
| Ground    | 8           | 5              |
| RD (DTE)_ | 1           | 2              |
| TD (DTE)_ | 2           | 3              |
| +12V      | 7           | NC             |
+-----------+-------------+----------------+


Thanks very much Coulomb.

I had another look, it seems my inverter has a different comms board to one I've seen on this thread. It's similar, but mine is double sided with some jumpers for setting the relay/power switch switch behaviour.

Worst part is the +12V line is on pin 4 on my RJ45. Ugh. I guess I'll just pull power through diodes on both options.

The USB versions still worry me. I was told that the RJ45 on the USB equipped inverter is labelled as the remote display port. They probably just put a USB-Serial chip in there, but if anyone comes across a photo of the board it would be helpful.

ImageImage

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Re: PIP inverter repairs and hardware modifications

Post by coulomb » Sun, 19 Jul 2015, 15:36

Scott wrote: I had another look, it seems my inverter has a different comms board to one I've seen on this thread.
Ah. Yes, the PIP I have here (borrowed) is a 2013 model. The serial interface board looks like this on the left, with your apparently 2014 board to the right:

Image     Image

The 2013 model doesn't seem to have the dry contact at all. It does appear that they changed the position of +12V and even ground. So beware if anyone else tries to plug anything into that RJ-45 other than the supplied cable.

The power switch on this older model is totally separate, and appears at the bottom right of the front panel, not underneath (as normally installed). [ Edit: Duh! This was a mod to the unit I've borrowed. The switch is underneath on all models, as standard. ]

I hope you're right about the USB connector being or a remote display. That would indicate that the RS232 port won't disappear in future versions. Presumably there would be a 2015 model out now, with the hardware for the leakage testing of the PV array, as required by the latest standard.
Last edited by coulomb on Thu, 23 Jul 2015, 05:07, edited 1 time in total.
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Re: PIP inverter repairs and hardware modifications

Post by coulomb » Sun, 19 Jul 2015, 16:19

Scott,

after looking at your photos again, I wondered why there was a relay on my board, and no DC/DC. So I looked underneath, and realised that what I assumed was a small relay is actually a tiny power supply. I don't know if it's DC/DC or AC/DC.

[ Edit: it actually is a relay; see below ]


So now I have an under the board photo to compare with yours. Again, the 2013 model is left/first, and the 2014 model is right/second.

Image     Image
Last edited by coulomb on Mon, 20 Jul 2015, 06:10, edited 1 time in total.
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160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

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Re: PIP inverter repairs and hardware modifications

Post by Scott » Sun, 19 Jul 2015, 23:07

coulomb wrote: after looking at your photos again


Thanks for the photos, they're very helpful.

That black box is a relay (see here) and it looks to me like they're routing it out to the RJ45 on pins 3,4,5 although it's difficult to see clearly with all the silkscreen.

Image

I haven't measured but I'm pretty sure the HFPW pins are 'high frequency power' which drive the primary side of the isolation transformer. The secondary side would the be center tapped and the two zener diodes clamp it to plus and minus 12VDC for the RS232 voltages. The two caps would then smooth the two supplies.

I managed to find a destructive test report that had photos of the '2012' board. It doesn't use the separate 2 way HFPW connector but still uses HFPW+ on the other 6 way connector. I assume that the + line wrt ground will generate enough power to drive the RS232 line, but not enough to drive an external display. It doesn't look like there's any power line on the 2012 board's RJ45 at all.

Here's the photos I have of all the boards, the dates on the transformers match up.
boards2.jpg
boards2.jpg (223.46 KiB) Viewed 2428 times
Comms board 2017.jpg
Comms board 2017.jpg (45.58 KiB) Viewed 1675 times
EDIT: Added photos of 2015 board
Edited Coulomb: added photo of 2017 board

[ Edited Coulomb: Replaced the above dead image with a saved one. Also added the 2016 board below. It's from a 3 kVA machine, which means it doesn't have the USB port. Thanks to RiaanH for the images. ]

Image
Last edited by coulomb on Sun, 28 Aug 2016, 09:13, edited 1 time in total.

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Re: PIP inverter repairs and hardware modifications

Post by ChrisHobson » Mon, 20 Jul 2015, 00:30

Image

MY PIP/Axpert is a June 2015 build. I took a photo of the board this morning. Hope it helps.

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Re: PIP inverter repairs and hardware modifications

Post by Scott » Mon, 20 Jul 2015, 09:53

That's great, thanks very much.

The inputs to the board look the same, and it still looks like it drives RS232: the RJ45 connector, optoisolators for the serial lines and two capacitors for the dual supply which wouldn't be needed if it were USB only.

The 6MHz crystal is probably for a USB-serial chip on the bottom of the board.

If anyone ever has a chance to see underneath the board then please post pictures.

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Re: PIP inverter repairs and hardware modifications

Post by coulomb » Mon, 20 Jul 2015, 16:41

ChrisHobson wrote: MY PIP/Axpert is a June 2015 build. Hope it helps.

It sure does, thanks Chris. Interesting that there only seems to be one relay on your board. So it seems that the relay on the 2013 board is the dry contact one, even though the signal doesn't seem to be named like the others on the main connector.
Last edited by coulomb on Mon, 20 Jul 2015, 06:43, edited 1 time in total.
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1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

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Re: PIP inverter repairs and hardware modifications

Post by dockarl » Wed, 22 Jul 2015, 22:56

Sounds like you folks have made some awesome progress here - congrats to Weber and Coulomb for a job well done..

LOL Coulomb - the power switch you so describe on the front panel of the 2013 model doesn't come out of the factory that way - but I did modify mine that's with Weber at the moment so that the switch was more accessible...

I've been pretty hard to get in contact with over the last while, but I'm guessing this means that Weber was successful in getting my blown board up and running again? Woot! If that's the case, awesome news.

We're doing some work with Aboriginal communities up in Central Australia and I'd dearly love to use this unit as a backup for our genset, so if my hunch is right and between the two of you you've pulled off a miracle and got it kicking again - would be appreciated.

Cheers,

M
Last edited by dockarl on Wed, 22 Jul 2015, 13:30, edited 1 time in total.

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Re: PIP inverter repairs and hardware modifications

Post by dockarl » Thu, 23 Jul 2015, 22:04

Solamahn - fellow previous PNG expat here.. I worked on the LNG project based in POM and previous to that around Madang. I'm a comms eng currently out of work, or working for myself which means working for free :)

I thought I'd pipe up here - just replying to your comments quite a few pages back with regards to your mosfet failures always seemingly occurring when the batteries are at a high state of charge, and usually after a load.

I can confirm that's the same behavior I noted with my PIPS - I had 3 failures in 12 months - all up it was only in service around 6 months the remainder of the time was either waiting for parts from the manufacturer to manually replace myself, or waiting for new boards to arrive..

I also noted that these failures often occurred when we were at a high SOC and the sun came out from behind a cloud - but the commonality was that it was always when batts were at mid to late absorb and high SOC. I was using AGM batts, about 375Ahr total 3 strings of 12V 125Ahr in series parallel.

These issues initially occurred (as you described with the PIP itself), without any external SCC (just using the internal scc - see my video here, which I captured and sent to MPP) and after some weeks working back and forth with MPP they issued a firmware upgrade early 2014 which made the PIP scc a lot more stable. Unfortunately though I continued to use their PCM5048 SCC in parallel with the inverter. These exhibited similar behavior with 'overvoltages when batteries at high SOC' which kept causing the bus caps and fets to blow on the inverter - here is an example I caught on camera and sent to MPP. It was very, very frustrating, particularly given the high cost of returning boards etc back to Taiwan for changes that never seemed to fix the problem.

I was a very early adopter (they told me my unit was the first into Oz). After 12 months of patiently navigating the difficulties of the whole experience, and being sent up a lot of dry gullies, when they couldn't find a solution they stopped replying to my emails. In the last email I received, they blamed my failures on 'high inductive loads', and from memory said the failures were on the AC side, which just wasn't the case. The failures were always on the DC side and always occurred during these DC overvoltage events at high SOC. I found myself with a bunch of useless fried hardware, including a broken inverter board only 3 months old. This disappointed me a lot as I had thought Eric and I had developed a pretty good rapport through hundreds of emails. Coming from an R&D background myself, I understood that product development is an ongoing thing, so I'd also invested a lot of patience, time and effort into helping him sort out the teething issues. It was certainly a very disappointing outcome.

Ultimately after lots of unanswered emails I got pretty insistant and warned him that if he failed to address the problem and honor the warranty, my only choice would be to let others know. I got no reply so I made a series of videos detailing my experiences (see the first one here). Ultimately the whole experience left me with a very bad taste in my mouth, a lot of wasted time and a much lighter wallet.. That is probably one good example of why it may be better to deal with Giant as at least then you'd have consumer protection laws to assist in the event that something similar happened.

Glad to hear things appear to have been more responsive for you with warranty, and interested to hear that they've seemingly changed the fets now..

Luckily a friend (as above) offered to have a look at the inverter and we're still hopeful I might get mine kicking again, and I feel fairly confident that with the combination of better fets and caps, and different charge controllers, my experience may be better this time.

For those considering using the MPP gear, one thing I definitely would suggest is be wary of their charge controllers. There are numerous other examples around the interwebs of people having similar experiences to me with the MPP Charge Controllers going haywire and failing to do that most basic task - controlling charging. Prolonged overvolts to 63V and higher seem to be a 'thing' with them. Personally I think it's because their PIDS are software based and under certain conditions the nyquist rate of the underlying signal exceeds the sampling rate of the gear - and control is just completely lost. I thought this may only be an issue with AGM's but I've since had one report to my youtube channel of it happening with straight LA's as well.

I log all my gear live online at 10 second intervals and I definitely have not seen the same overvoltages since I've moved to a different manufacturers charge controller and (by necessity) inverter - everything else in my system, batteries, cabling, panels etc - is all the same.. so it tends to indicate pretty strongly to me that there is something with the MPP SCC's that doesn't play well with some battery chemistries, and that it could be worth considering using a different brand charge controller if you choose to use the PIPs.

M
Last edited by coulomb on Fri, 24 Jul 2015, 04:22, edited 1 time in total.

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Re: PIP inverter repairs and hardware modifications

Post by coulomb » Sun, 26 Jul 2015, 02:21

dockarl wrote: Sounds like you folks have made some awesome progress here -
Errrm... Image
...I'm guessing this means that Weber was successful in getting my blown board up and running again? Woot! If that's the case, awesome news.
Actually, I was just borrowing the PIP unit, because it wasn't being used much, for protocol research.

But now that you remind us, it is rather a long time since Weber's first unsuccessful attempt at fixing it, so we decided to make testing it a part of Project Day.

Weber has a PIP repair manual from somewhere, so we decided to start by following the testing procedure. Some parts of it were a bit silly, where resistance values obviously depend on the multimeter in use (and we obtained three wildly different readings from three multimeters for some measurements). But overall, it was still pretty useful, and we discovered a multitude of failed parts:

Image

Ok, I'm being a little melodramatic here...

The row of capacitors were pre-emptively removed from Kurt's unit, but there was a similar number each removed from both of dockarl's inverter main boards. Several of these had bulging tops, which would have looked more impressive, but alas weren't kept.

The bottom row of MOSFETs were replaced with higher voltage versions, even though only one set of four was faulty from each board. You can see the right hand two let go with gusto, and a few of the others were a bit blackened. That's only one PIP board's worth of battery-side MOSFETs, by the way.

In the middle row, we have IGBTs from the two boards, on the high voltage side of the high frequency transformer. "Only" four are blown, which means we can make one good board from two bad ones. But on the right end of the middle row, there are three faulty high voltage MOSFETs, from the buck stage. There are only four of these (from two boards), so alas we could not get one board working after all. There is a last stage, another full bridge of IGBTs, and they seem to be OK, at least so far. (Perhaps this last stage was protected by the failures earlier down the chain).

It might be worth mentioning the amazing chain of power conversion in the PIP inverters. When inverting, it starts with the MOSFETs on the nominal 48 V bus; these are the 16 MOSFETs shown at the bottom of the photo (four sets of four paralleled devices). The resulting square wave feeds the high frequency transformer, which then connects to the full bridge of IGBTs (left middle row). This seems to create a high voltage bus, perhaps 400 V. There is then a buck stage, involving strangely either a pair of MOSFETs or a pair of IGBTs. These boards have two MOSFETs, and they do seem to be paralleled (source to source and drain to drain). Finally, there is the full bridge at the 230 V AC output, using four IGBTs.

Note that all of these stages (with suitable gate drive!) are power flow reversible, and this seems to be how the PIP does its mains to battery charging.

So dockarl, we gave it a good go today, but fell short. Weber will order replacement parts soon, with the BMU prototype parts. Hopefully after those parts are replaced, the PIP boards will be working again.

[ Edit: reworded to mention Weber's original attempt to fix both boards; 230 V -> 230 V AC ]
Last edited by coulomb on Mon, 11 Jan 2016, 02:51, edited 1 time in total.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

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Re: PIP inverter repairs and hardware modifications

Post by solamahn » Sun, 26 Jul 2015, 13:57

Yes. Saw your videos. I don't think it is the number of panels or too much inductive load that has been causing the failures of mosfets on hs1. I have one site with a 2448ms running 15 x280w and 4 500 ltr deep freezers and no problem. It has 12 x 12v250ah AGM's. I just had another failure last week from a 2448 with 9 of those panels running 1 deep freezer but only has 4 batteries. I will update the software in all my sites. About 75 sites. Over time by I will end up changing all the main pcb's I suspect. I have changed more than 20 so far. Last one was a 2424msx. I also sell mppsolar ups from 2.4kw to 8kw with no failures. Hopefully the ongoing improvements to the pip range will result in reliable units also. We install from Aroma to Mekeo so far. Apart from the failures, I think pips are a terrific inverter/charger for the price. I deal with James at mpp. I have a 4048ms in service for more than 2 years without failure. I have never been back to that site. It has 16 x 280w and 16 12v200 AGM
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Re: PIP inverter repairs and hardware modifications

Post by dockarl » Sun, 26 Jul 2015, 20:29

Yep Solamahn I suspect it's ripple the charge controllers are trying to chase, and that's what Eric implied also. If my understanding of ripple is correct more batts = more 'capacitance' = batts filter the ripple. It still highlights a problem - better to deal with the ripple at the inverter and charge controller than at the batteries. Some research I have found indicates that high ripple aint good for batteries lifespan, but anecdotal evidence suggest more batts does seem to help the issue with these units. I guess it comes down to the economics of buying a decent charge controller vs the economics of lost lifespan from batteries due to potential unseen overvolts and high ripple.. In my case I was able to find a good european brand SCC for about the same cost as the money I wasted on the pcm5048's so it became a pretty easy decision..

In my case I have 12x125Ahr batts, for a 375ahr @ 48 Volts which isn't all that small, really. I think from memory MPP's specs call for minimum 200Ahr battery so per specs I have almost double the requirement and should be fine but doesn't seem to be the case.

Glad to hear your 4048ms system is working great.

Coulomb - thankyou very much for spending that time with Weber on your 'project day' - much appreciated. One thing I would like to do in part recompense is to donate the 'other' board to you guys to use for protocol research or maybe as a cold spare for all of us..

Cheers from Alice Springs,

M
Last edited by dockarl on Sun, 26 Jul 2015, 11:26, edited 1 time in total.

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Re: PIP inverter repairs and hardware modifications

Post by solamahn » Sun, 26 Jul 2015, 21:35

Yes. You notice that when AGM's are full, they don't regulate voltage as good. But that could be said of all battery chemistries, I think. I wonder if setting the float to 52 would help. But really the scc should react quick enough to a change in solar current so that it is not the batteries that at doing the voltage regulation.
I tried lots of different things to fix this problem. Originally I thought the MOSFET failures were due to overheating so I mounted the inverters off the wall a bit, turned the fans upside down, reduced max solar charge, reduced load, fitted smaller ac out breakers, connected panels 3 in series instead of 2 and even changed from using one inverter to two in parallel.
Looks like the problem was always the use of 125A fets on hs1 instead of the 200A ones which are fitted on the latest versions.
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Re: PIP inverter repairs and hardware modifications

Post by ChrisHobson » Mon, 27 Jul 2015, 08:34

solamahn wrote:
Looks like the problem was always the use of 125A fets on hs1 instead of the 200A ones which are fitted on the latest versions.


Hi Solamahn

When did they make the change from 125A to 200A mosfets roughly?

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Re: PIP inverter repairs and hardware modifications

Post by solamahn » Mon, 27 Jul 2015, 10:18

I don't know. It must have been this year some time. Hopefully yours has the 200's
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Re: PIP inverter repairs and hardware modifications

Post by Scott » Fri, 14 Aug 2015, 07:37

Not sure if anyone's posted the service manual yet. It's not great but it's something...

http://dealer.mustek.co.za/write/upload/specs/sol-i-ax-5m/axpert_mks_4-5kva_service_manual_20131104a.pdf

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Re: PIP inverter repairs and hardware modifications

Post by Tjadenw » Fri, 14 Aug 2015, 07:48

Thank you

I've been looking for the service manual
Do you have the Axpert 3K service manual also?

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Re: PIP inverter repairs and hardware modifications

Post by coulomb » Fri, 14 Aug 2015, 16:36

Thanks, Scott, every bit of information helps. This has more detail than the repair manual we had so far.

I hope that this isn't literally the schematic of the MPPT controller:

Image

If so, there is essentially no dead time, so the two MOSFETs will short the panel with the input capacitor in parallel with it, allowing a pulse of current to "shoot through" the pair every half PWM cycle, causing needless heating and stress. But apart from the power supply schematic, which seems fairly complete, these schematics seem very generic. Still, a lot better than nothing.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

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Re: PIP inverter repairs and hardware modifications

Post by coulomb » Tue, 18 Aug 2015, 01:50

At Project Day yesterday, Weber noted that the above topology is somewhat clever; with the interleaved nature of the SCC, there is always a smooth current drawn from the input (when one half is fluxing its inductor (top transistor of the pair on), the other half can be free wheeling (bottom transistor, really just a low loss diode, turned on). Presumably this reduces the current that has to be supplied by the capacitor at the input (this capacitor would absorb solar panel energy when none of the top capacitors are conducting, and supply it later). For those interested in the technical details, here is an article on multi phase buck converters. It looks like ripple current reduction is the main benefit, but there seem to be others.

I spent most of project day installing the parts recently purchased for dockarl's PIP and the spare board he bought. It looks like his original board was one of the first PIPs manufactured, made in 2013. The replacement board is from 2014. It seemed to make sense to work on the 2014 board first. Seven devices went into that board: 2 MOSFETs from the buck stage (and thanks to Scott's manual, we now realise that these aren't in parallel*), 4 IGBTs from the bus end of the DC-DC converter, and the switcher for the bus soft start circuit. This latter one we replaced, even though the originals seemed OK, because the original fault code was 09, "Bus soft start failed". (It was cheap, contrasting with the > $10 each plus tax for the IGBTs). We now believe that when nearly anything blows up from along the power train, the microcontroller will pick this up as a bus soft start error. Weber pointed out that you can't soft start if you have no power, after all.

[ Edit: * Actually, they are in parallel, the manual's block diagram seems to be highly idealised. The MOSFETs or IGBTs for the buck stage are actually in the negative side of the bus, for example. ]
[ Edit: * It turns out that later models have only the one IGBT/MOSFET in the buck stage. These have a TO-220 diode in place of the TO-247 package.]

One of the buck MOSFET/IGBTs (they could be either) is right behind the biggest film capacitor I think I've ever seen. It measures 50 x 40 x 30 mm. When trying to put this MOSFET in, I thought this is nuts, I may as well pull out the capacitor and make things easier for myself.

Image

It's doubly crowded in, by the fins of the heatsink on top and this capacitor in front. Others have the smaller (but still large) blue capacitors in front as well, but fortunately not this one.

Well, it has "leads" that are the same size as the contacts of automotive fuses; they're almost like quick connect terminals. So it was hell getting it out, and even more hell getting the solder out so I could put it back later. Fortunately, there are many plated through holes around the slots where these "leads" pass through the printed circuit board, so I didn't have to worry too much about losing plating between top and bottom side of the board. I ended up using a drill as a crude milling tool, carefully taking my time so that the thin drill didn't break. It did make the MOSFET easier to replace, but for the spare board, I decided not to remove the big black capacitor from that board Image

I set up a current limited power supply, with 24 V of batteries in series, so that hopefully nothing too violent would happen if anything went wrong. I switched on, and... nothing. No light from the LCD display, no fans whirring, no power LED. Huh. I'm sure it was working at least to that level last time, so now with all these repairs it's worse. But wait, last time we were running off the mains, not the battery. Ok, set up the mains wiring, switched on and... nothing. Image

Huh? But last time... Weber pointed out that the mains wire was attached to the other board, the 2013 one, so we must have tested on that board, not this one. But before I did the whole replacement exercise on the other board, I thought I'd try and see what's wrong with this one, if only to figure out what parts to buy. After all, with Scott's manual for the Axpert inverters, the one fairly complete schematic is for the power supply. Well, for the battery power supply; it turns out that there are two similar power supplies, one that runs off the battery, and one that runs from the AC input. They both use a UC3845 "current mode PWM controller" IC, but get this: one is a through-hole version, and one is surface mount! I can only imagine that one came first, say the battery one, and then it was decided that the AC input one would be added later, and they only had room to put it surface mount underneath. I guess they didn't want to mess with the existing through hole one; don't mess with something that works.

All the semiconductors seemed to check out OK, except for the UC3845 chip. The resistances didn't seem close to what the repair manual suggested that they should be. When I checked the other board, the resistances were much closer to what was specified. Resistance checks like these can be very unreliable, since they depend so much on the multimeter used, but I felt confident that the other board would work.

So I mentally noted to buy this chip, and set out to make the repairs to the other (2013) board. It turned out that it wasn't such a hard thing to replace the buck MOSFETs with the big black capacitor still in place, when I managed to squeeze a socket in there and rotated it by a combination of finger power and pliers. So this time, I connected up the power supply and battery, switched on, and... nothing. Waah!   Image

But last time... Ah, again, that was on the mains. Could it be that three of the four power supplies were broken, and the one I hadn't tried was still good? Only one way to find out. I connected the mains wiring, switched on, and... Light! Beautific, glorious light was poring forth from the liquid crystal screen! Joy! Image

Now to connect a battery before I had to head home; it was getting late by this stage. But at that point, I spotted a medium sized white capacitor. Oops! Image I had removed a white capacitor that was blocking the IGBTs (it has normal pigtail leads, so it's easy enough to remove and replace), and had forgotten to replace it. (Part of it is visible at the right end of the photo.) Sigh. So I'd have to wait for Weber to replace the capacitor and try again next morning.

That was this morning, and it seems to charge the battery just fine from the AC input. As I understand it, that involves the whole power train (full bridge at the AC output, buck converter, and two full bridges at the DC-DC converter on either side of the high frequency transformer). Actually, it may not involve the first two, I just don't know how the battery charger function actually works. But it's a pretty good sign. Weber didn't attempt to fire up the inverter part as an inverter, reasoning that something bad may happen because the power supply (from the battery) is not working.

I have the other board here now, and will attempt to get it working. Hopefully, the same repair will get the other board working as well. So dockarl, we think we're getting close to repairing the two boards.

[ Edit: by the heatsink -> by the fins of the heatsink; white capacitor was blocking IGBTs; visible at right end of photo. ]
[ Edit: buck converter is not in reverse when AC charging.]
Last edited by coulomb on Sat, 15 Jul 2017, 09:10, edited 1 time in total.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

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