PIP-4048MS and PIP-5048MS inverters

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T1 Terry
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Post by T1 Terry » Sat, 24 Jan 2015, 01:47

offgridQLD wrote: "broken up into sets of 4 and each individually charge controlled "

So Terry, your saying you have two separate 12v chargers on your 24v 8 cell banks?


Your secondary system being cell level motoring with balancing ? what are the voltage limits befor the secondary system kicks in?


The key point I guess is how good is the manufacturing process / consistency of the Calb/Winston cells. That's the one thing we cant change and as long as your interconnections are up to scratch . Most likely the only reason they go out of balance. How much and how long it takes is on average with our kind of assuage is the key bit of info.


Kurt

The systems use 12v nom. solar panels, the negative for the "B" set (12v to 24v nom) is tied to positive terminal of the "A" set (0v to 12v nom.) By cutting the positive on the "A" solar the "A" battery stops charging, but the "B" battery continues to charge. By cutting the neg on the "B" solar the "B" battery stops charging, but the "A" battery could continue charging if required.
3.6V in any cell in the 4 cell pack sets the secondary system into action, at any other time the charging is left to the primary control.
Mains charging is SOC controlled, start at 20% SOC and stop at 80% SOC, no run-aways within this range, but either secondary circuit can cut the mains supply if a high cell voltage is detected. This was required as a safety in case the SOC was incorrect or lost due to a temp disconnection of the meter.
As far as dirty connections, they show up on a log graph as a quite obvious tell tale, high voltage when charging and immediate low voltage under load equals a high resistance some where within that cell group. We use multiple smaller capacity cells in parallel to build up to the Ah required, then series connect these packs. The advantage is the differences in production tolerance's are balanced out across a number of cells, this really helps with maintaining a balanced pack.

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Post by offgridQLD » Sat, 24 Jan 2015, 04:17

"it's the slow trickle charge at the very top end of charging that seems to cause the most run aways."

Wouldn't that just be that you can only really measure the inballance at the top and the bottom of the cells SOC. So the slow trickle of current at v absorb is not causing the inballance just making it visible/mesurable as all the cells reach full at different times.

Kurt

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Post by T1 Terry » Sat, 24 Jan 2015, 05:03

When the charge rate is low, the first cell full will run away every time if the control is measuring terminal voltage only.
An attempt to explain the way I see it, the terminal voltage is set at say 14v, if all the cells are at 3.5v at same time, the charge will simply stop till the voltage drops below 14v, then a small amount of current is added to raise the voltage back up to 14v if it drops slightly. The cell that is 100% charged will immediately increase it's voltage, you can't get anything more in so the voltage goes up.. to say 3.55v, this means the other cells must be lower than 3.5v for the total to still add up to 14v. This process repeats until either a secondary control stops the charging for a period or the cell will be damaged.
When the charge rate is higher this voltage creep in a single cell doesn't seem to occur as the charge period is very short compared to the period of no charging, the battery may only be 99% full, but does it really make any difference if there is ample current available to replace anything used from the battery? Unlike an EV, the battery isn't charged then drained, it's connected to the charging device (solar) all day, then drained over night, if that 1% is a make or break for the over night capacity the numbers have not been done correctly and a larger capacity pack is required, not a charging regime that will get in that last 1%

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Post by offgridQLD » Sat, 24 Jan 2015, 05:31

That charging method isn't used because we want every last drop of capacity. It's used because there is no reliable way to tell her if there is a inballance between the cells unless you charge them until you reach the upper knee and find out as they all reach that state at different times.

As mentioned a few times just because you don't see cell level voltage discrepancies below the knee doesn't mean you are avoiding them or don't have them they are just hidden in the flat voltage that lifepo4 cell have over the bulk of there SOC.

Kurt

Last edited by offgridQLD on Fri, 23 Jan 2015, 18:32, edited 1 time in total.

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Post by offgridQLD » Sat, 24 Jan 2015, 05:33

The above was not taking into account the smaller less pronounce knee at 78% SOC mentioned earlyer.

Kurt
Last edited by offgridQLD on Fri, 23 Jan 2015, 18:41, edited 1 time in total.

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Post by weber » Sat, 24 Jan 2015, 05:48

The monolith just successfully completed its first discharge test with the customer's cells. Starting with a full battery and with all charge sources turned off, it took just over 13 hours of running our 4 person household, from 9:35 am to 10:49 pm, when the IMU shut off the source contactor due to a smoothed undervoltage stress of 12. We consumed around 6.7 kWh of AC energy. The design daily energy for the customer's two-person off-grid household is 3 kWh.

The battery is nominally 180 Ah at 52 V = 9.36 kWh. The cutoff was based on lowest cell voltage, corrected for IR drop, and was designed to correspond to 80% DoD.

The last reading, 15 minutes before cutoff, showed the lowest cell at 3.200 V, highest cell 3.218 V, total battery voltage 51.2 V, at 15 amps discharge.

It did reveal one software bug. The coulomb counter said the DoD was 166.9% at 15 minutes before cutoff. I think I may need another right shift somewhere. Image Presumably that was 83.5% DoD. Relative to the nominal 180 Ah that's 150.2 Ah. Multiplied by 52 V that gives 7.81 kWh of DC energy. So the efficiency was something like 6.7/7.8 = 86%.
The average AC load was 6700/13 = 515 W. So the loss amounts to 84 watts, most of which is the standby power consumption of the PIP plus the DC-DC, IMU and contactors.

All as expected, or better, (apart from the magic 167% DoD).
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Post by T1 Terry » Sat, 24 Jan 2015, 12:05

offgridQLD wrote: That charging method isn't used because we want every last drop of capacity. It's used because there is no reliable way to tell her if there is a inballance between the cells unless you charge them until you reach the upper knee and find out as they all reach that state at different times.

As mentioned a few times just because you don't see cell level voltage discrepancies below the knee doesn't mean you are avoiding them or don't have them they are just hidden in the flat voltage that lifepo4 cell have over the bulk of there SOC.

Kurt

If the end charge terminal voltage is 3.45v x the number of cells, how much capacity out of balance can you have without a cell running away to 3.6v causing the secondary system to kick in? If you must use cell balancing then start the load dump at the cell level at 3.55v, but not on top of the cell, remote from the battery pack so the heat is not added to an already hot cell. Just because that is the easiest spot to do it doesn't mean it's the best spot, try holding one of those cell balance boards between your fingers when it's dissipating a 2 amp load as heat, what effect do you think that heat would have on cell cycle life if added to an already hot cell?

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Post by offgridQLD » Sat, 24 Jan 2015, 12:16

"what effect do you think that heat would have on cell cycle life if added to an already hot cell?"

Perhaps in a car regen braking at high current or racing up a mountain sucking 100kw from the battery they might get hot. In a offgrid application with a inverter that can only consume 6000w continuous and a chager that can only charge it at 6000 - 8000w the cells would never get above ambient temperature with 0.4C max charge/discharge.

Yes the on cell boards do get a little toast when shunting the full 2A for long periods.Though when they are clamped to a big aluminum cell post & 14kg of thermal mass in the cell they don't get that hot and Im sure they would have little effect on the cells temp. In day to day use they shouldn't shunt much and not for very long.

Yes I agree there might not be much in the 3.55 - 3.6v range. I was under the impression you were not changing as high as that.

Kurt
Last edited by offgridQLD on Sat, 24 Jan 2015, 01:20, edited 1 time in total.

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Post by T1 Terry » Sat, 24 Jan 2015, 12:47

The aim is 3.45v per cell and no cell going over 3.6v. Someone might be able to provide the link to a post regarding cells being held at 3.65v with milli amps going in and balance boards attached in an attempt to balance the pack over a few days.... it was in reference to float charging I think, read through the results of that action and gauge from there if charging a cell to 3.65v gets them hot or not.... then add that heat from the balance board using the cell contents as it's heat soak, are you sure that isn't doing damage to the cell?

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Post by T1 Terry » Sat, 24 Jan 2015, 14:01

An interesting item regarding solar and off grid in Climate spectator south facing panels seems the idea is not as silly as it sounds, yet everyone told me I was wasting my time with south facing panels Image
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Post by weber » Sat, 24 Jan 2015, 16:20

I'd like to remind folk that this thread is about the PIP-4048MS inverter/charger/mppt, which is already somewhat off-topic for an electric vehicle forum.

South facing arrays, while good to know about, are not specific to systems using the PIP, so please continue any discussion of them elsewhere. Perhaps repost the link in a separate thread in "The Lounge".

Discussions of cell balancing schemes are only relevant to this thread if they can be applied to a 48 volt battery charged by a PIP-4048MS. There is certainly more than one way to do this, and it seems to me that all three of us (Kurt, Terry and myself) know what is required, and all 3 proposed methods should work, although they are all very different. We're each working with the gear we have and the gear we know. All good stuff.
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Post by T1 Terry » Sat, 24 Jan 2015, 16:56

I believe some where around page 4 the connection was made between the thread title and solar arrays, that was why the link was posted here as at times this thread has pertained to solar positioning etc Image Image

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Post by weber » Mon, 26 Jan 2015, 07:18

I've had some brilliant help on the Monolith in the last two days. Yesterday Jeff Owen turned up unannounced, just when I needed some serious help figuring out how to attach the twinwall smoked polycarbonate sheeting and make it look decent, with stuff I could buy today. He came up with a brilliant design as usual.

My friend Dr Mark Hayes helped me find everything in Bunnings this morning and my dad helped me by cutting all the polycarbonate sheets and the fibro-cement backing sheet (for fire resistance against the outside wall of the house).

And Coulomb (Dr Mike van Emmerik) wrote the software to drive (PWM) the State-of-Charge meter you can see working below.

Image
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Post by weber » Tue, 27 Jan 2015, 06:38

Mike and I sure worked hard today to get the case finished. Jeff Owen phoned his apologies. Called away to a family event. What does his family think this is, Australia Day holiday or something? Image

We didn't quite get the case finished. The plastic louvred vents for the sides and top will have to be put in on site.

I had spray-painted the vents flat black, then put them out in the morning sun to harden the paint faster, then stupidly forgot all about them. When I finally remembered, they looked a bit like that Salvador Dali painting with the clocks. So I'll have to buy some more.

Also, the next monolith will have the aluminium framing painted flat black too, But I ran out of time on this one. I think it looks pretty cool with the natural aluminium, but we had to be a lot more precise with our mitred corners with it not being flat black. We'll see what the customer thinks.

Between outside faces (not including the 1.6 mm of aluminium) the dimensions are 225 x 900 x 2025 mm +- 1 mm. (1 : 4 : 9)

Image Image Image
Image Image

Is it an alien artifact, or is it an open-source, Prius-transportable, tomb-stone for coal fired power. Image
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Post by weber » Wed, 28 Jan 2015, 04:00

The installation went well today, although we did not get the array connected. But I'll be back out there again tomorrow.

We're keeping their old existing system going, with a changeover on the AC switchboard, until we are confident we have overcome any teething problems with the monolith. You can see the old gear temporarily jammed untidily to the right of the monolith.

Sorry about the poor light for the photo below. And sorry it's shut down, so there are no pretty lights shining through the smoked polycarbonate. I'll do better tomorrow.

Immediately to the left of the monolith, two thirds of the way up, you can see the generator inlet, and symmetrically on the right you can see the shutdown button with the SoC meter on its side.

Image

Many thanks to all who help make this possible.
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Post by Adverse Effects » Wed, 28 Jan 2015, 05:53

so when dose the monolith worship meetings start?

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Post by PlanB » Wed, 28 Jan 2015, 21:43

Who needs fancy multi drawer tool caddies with castors when you've got an ironing board? Also your cat has scary eyes. Nice job on the 'tombstone to coal fired power', we live in interesting times.
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Post by weber » Thu, 29 Jan 2015, 16:13

Thanks Adverse Effect and Plan B. Your comments make me smile.
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Post by offgridQLD » Thu, 29 Jan 2015, 16:23

Looking good on location. Image

So once the system is fully operational. Is it going to be fully intrusted to the new owners with installer on call if there happens to be a issue. Or will you have remote access to the PIP online to keep tabs on it.

I know a lot of installers have remote access to there clients systems for the odd check up.

.....we just don't want the story to end on handover Image

Ps, My 400ah calbs have been no fuss at all and performing beautifully .Very happy with the upgrade from lead acid.

Kurt
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Post by Adverse Effects » Thu, 29 Jan 2015, 19:59

get one of thos micro stick computers like the BBB or Rassbry Pi and have it set up in linix to remote in to for maintenance Image Image

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Post by weber » Sat, 31 Jan 2015, 07:24

The old and the new. The old lead-acid system on the right. The new lithium system on the left.

Image

At night, without the camera flash, so you can see the internal lights.

Image

The top of the monolith, showing the two vents above the PIP's MPPT heatsink, and the conduit entries which are (left to right) generator in, AC out, PV array in, and shut-down button and SoC-meter.

Image

The next two photos show the three vents being fitted to a side. Both sides are the same. After the "Salvador Dali" fiasco, I have cleaned out 5 Bunnings stores of the dark brown version of these vents, which I spray-paint flat black. In fact I settled for using one white one and it appears in the photos in this post. Can you pick it? No, but you might in a few years time if some paint gets rubbed off. So you can guess where I put it.

I've placed them in reverse chronological order because that way they happen to also make a (poor) cross-eyed stereo pair. Use Ctrl+minus to reduce them in size.

Image Image

The new PV array, maxing out the PIP with 6P x 3S of 195 W SunTechs. [Edit: Corrected "6S x 3P" to "6P x 3S"]

Image
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Post by weber » Sat, 31 Jan 2015, 19:00

All aspects of the monolith design, aesthetic, structural, electrical, electronic and software, are open-source. Steal this idea. Just make sure you steal it properly, as there are significant safety issues relating to fire and electric shock.

Let me know what aspects you want documented.

I have designed it, to the best of my knowledge, to meet the current versions of AS3000, AS4509, AS5033 and AS4086, but it is up to you to verify its safety and suitability for your own purposes. Of course the big question-mark hanging over it is how robust, reliable and long-lived is the PIP-4048MS inverter/charger that is the monolith's heart. Only time will tell.

Apart from myself, the greatest contributor to this project, by far, was Dr Mike Van Emmerik (Coulomb) for electronics, software and construction help, and for always responding to my innumerable ravings via email, despite having a full time job and a family. At least this Weber & Coulomb project only took 3 months, not 5 years. Image But of course we have re-purposed, as the monolith's nervous system and brain, the (open-source) BMS we developed for the MX-5, which took up so much of those 5 years.

Also deserving of special mention are David Chaplin for electrical design advice, construction help and installation help, Greg Breslin and my father David Keenan for construction help, Trevor Berrill for control-system design advice, and Jeff Owen for saving my arse when I discovered, with 2 days to go to the second scheduled installation date, that my ideas about neatly cutting and solvent-welding the twinwall polycarbonate were the purest fantasy. Also Mike (again) for saving my arse by debugging-extraordinaire, and by implementing a state-of-charge meter with one day to go.

And all of the above for visiting and giving me the benefit of their intelligent company on what is otherwise lonely, and therefore hard to motivate, work.

Also my wife Janelle who has been a "monolith widow" and taken care of my household chores as I battled with the control software development and testing for the past month or so.

Also "the customer" (who shall remain nameless for security and privacy reasons) who was willing to take a risk on something that he knew only existed in my mind, and who paid 50% in advance, which made its development possible, and who put up with all the schedule-slips with great patience (well OK, perhaps he got a teensy bit concerned towards the end). Image And thanks to my former lead-acid system customers Gordon and Hanneke, Vicki and Maurice who must have given me a pretty good rap for "the customer" to be willing to take this risk, and to Gordon (again) and his African visitor Younus for installing most of the PV array.

And I want to thank all you folk who have helped me with valuable advice and discussion on this forum. Kurt (offgridQLD), Johny, T1 Terry, Kris (PlanB), Adverse Effects, 7Circle, celectric, antiscab and neilg.

Also Arthur C Clarke and Stanley Kubrik. Image

And in case you haven't had enough monolith photos, here are some full-frontal nudes.

Note the fibre-cement backing sheet for fire retardancy, and polycarbonate is one of the least flammable plastics (490°C ignition and self-extinguishing when external flame is removed).

Image Image Image

Image

When I first had the idea for a lithium-based standalone power system in a smoked polycarbonate monolith, months before "the customer" appeared, I described it to Mike in email and asked, "Is this a crazy idea?".

He replied: "Of course. But all great projects start that way, I suspect."
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Post by weber » Sat, 31 Jan 2015, 19:31

Here's the user manual for the Monolith.

Operating_instructions_for_the_Black_Monolith.pdf

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Post by weber » Sat, 31 Jan 2015, 21:35

offgridQLD wrote:So once the system is fully operational. Is it going to be fully intrusted to the new owners with installer on call if there happens to be a issue. Or will you have remote access to the PIP online to keep tabs on it. .....we just don't want the story to end on handover Image
Adverse Effects wrote: get one of thos micro stick computers like the BBB or Rassbry Pi and have it set up in linix to remote in to for maintenance Image Image

As you can probably gather from the 3 page user manual above, it's entrusted to the owner, with me on-call for any problems -- actually on-email (from the customer's work location) unless it's an emergency. I'll certainly let you all know how it goes. So far, no news is good news.

Remote monitoring, and the ability to remotely update the software would be nice. But it would be a lot of additional design effort and the customer has poor mobile phone access (you have to climb on his roof) and the landline is not likely to be amenable to ADSL (a very long way from the exchange) and they have not installed satellite internet.

Maybe PlanB, who is handy with a RaspberryPi, can get this aspect working.
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Post by Johny » Sat, 31 Jan 2015, 22:28

Incredible job Weber. I have watched with interest as the monolith developed and I think it it's a wonder to behold.
I have plans for an off grid system to sit side by side (metaphorically) our grid tied system and hope to tap into your knowledge and development when I finally get the bickies to go ahead.

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