PIP-4048MS and PIP-5048MS inverters

[offgridQLD]

+1 on the long winded Quote. I was starting to get a little dizzy scrolling though it on a Iphone trying to find the actual responses hidden in there


Kurt

[PlanB]

Is anyone else having issues with the box returning to factory defaults? I've set up the user battery option with mains charging limited to 2A a couple of times only to have it jump back to AGM charging at 20A.

[Adverse Effects]

ok doing a bit of looking around

its the 4048 4000W BUT it seems that its also listed at 5KVA and if that is the case

PIP-MS 5K52.30.rar this could be an update firmware

update firmware

the reason i say the 5K and not the 4K because of this quote in a different forum

Firmware Update Pip4048MS:

News from MPP Solar, have an answer today get tomorrow at 6h on the question which firmware is the correct one.
The fault was in the wrong firmware I have chosen. I have a set of three 4kw Pip4048MS, which was advertised as 12kw. So I have the software loaded 4k. Wrong. is the It 5k software.
(My 4kw unit had suddenly turned limp at 3200W and was at 100% utilization, as incorrect firmware of my set plays)

Now these things are advertised in VA, when I bought it still in kw.
So you can play different firmware, even back to an older one. The different firmware versions without description and mapping of real devices, there are also older versions messed up on the server, so dear to ask.
Mainly because the Flash tool makes NO check whether it is the correct version for your device.

Correct Software: PIP-MS 5K52.29 (UPDATED)
and PIP-MS SCCMPPT1.24

So no error on the part MPPSolar (apart from the lack of explanation in the ReadMe), no reduced performance of the device.
Wood and oil you can pick up again, now no witch burning. I'm concerned it is a UTS error.

[weber]

[Edit: The following excellent information was actually posted by Coulomb, from my computer. -- Weber]

its the 4048 4000W BUT it seems that its also listed at 5KVA

Yes, a little confusing. I think inverters are often quoted at a power factor of 0.8, so the headline number (in this case 5000 VA or 5.0 kVA) is more impressive than the actual power output (4000 W or 4.0 kW). I suppose it's nice to know that the IGBTs or MOSFETs will circulate the current required for an 0.8 power factor load, such as an induction motor. But you can only draw 4 kW plus losses from the battery side. (the extra kVA just circulates from the DC bus capacitors to the motor and back to the capacitors again 100 times per second, with some losses of course).

In short: the model most of us are talking about is rated at 4000 W and 5000 VA.

So you could connect a 4000 W heater (power factor 1.0) and run it all day, or a 5000 VA motor with a power factor of 0.8 (drawing real power of 0.8 x 5000 = 4000 W). [ Edit : assuming that the continuous power rating is realistic. ]

[PlanB]

Just curious which graph you got the 76%=3.32v balancing point from a few pages back weber?

[weber]

Just curious which graph you got the 76%=3.32v balancing point from a few pages back weber?

It's from this paper that Johny found, that these powerpoint slides are based on.
http://www.cse.anl.gov/us-china-worksho ... %20BMS.pdf
See pages 11, 12, 13 and 15.

The graph on page 15 suggests it is more like 3.325 V.

[PlanB]

So for a cell cycled between 20% & 80% SOC only about 0.1v difference? Or just 1.6v for a 16 cell pack. That's less than the voltage drop typical of 1C discharge.

[weber]

So for a cell cycled between 20% & 80% SOC only about 0.1v difference? Or just 1.6v for a 16 cell pack. That's less than the voltage drop typical of 1C discharge.

Right. But when floating/balancing at 76% SoC using our BMS, the charge current will be throttled back to the balance current of 800 mA which is around 0.005C for a 180 Ah cell. So voltage rise due to internal resistance will be around a millivolt per cell and can be ignored.

The low end of the cycle can be determined by coulomb counting. The capacity of the smallest cell, and hence the battery, could be determined by an occasional excursion all the way down to 2.8 volts, which can safely be considered empty, even at 1.2C (the peak load of the PIP-4048MS on a 180 Ah battery) and at temperatures as low as 15°C. This might be done annually, or every 365 cycles.

[weber]

Reports of a fault in a 24 V model
https://brandon314.wordpress.com/2013/0 ... er-review/

[offgridQLD]

Looking at the yellow case it looks to be a different model not the 24v version of the pip4048. That said I'm not sure if it has any Common layout, or construction defects.

I know the ridgidity or lack of suport of the caps was something I noted when I poked around in my pip4048.

Don't particular kinds of loads make the caps vibrate at particular freqancys or at least try to if they are unsupported.

Kurt

[Adverse Effects]

Reports of a fault in a 24 V model
https://brandon314.wordpress.com/2013/0 ... er-review/

"This entry was posted on April 1, 2013 at 11:14"

so its an old post

[weber]

Sorry. Yes, my mistake. That's in the LC series, not the MS series. I think that means it has a low frequency transformer.

[T1 Terry]

So for a cell cycled between 20% & 80% SOC only about 0.1v difference? Or just 1.6v for a 16 cell pack. That's less than the voltage drop typical of 1C discharge.

Right. But when floating/balancing at 76% SoC using our BMS, the charge current will be throttled back to the balance current of 800 mA which is around 0.005C for a 180 Ah cell. So voltage rise due to internal resistance will be around a millivolt per cell and can be ignored.

The low end of the cycle can be determined by coulomb counting. The capacity of the smallest cell, and hence the battery, could be determined by an occasional excursion all the way down to 2.8 volts, which can safely be considered empty, even at 1.2C (the peak load of the PIP-4048MS on a 180 Ah battery) and at temperatures as low as 15°C. This might be done annually, or every 365 cycles.

3v under a 1C load is very close to 0% SOC, not completely discharged but at the end of the advertised capacity. I would be looking at a system that disconnected non essential loads at around 20% SOC and a warn at 25% SOC, this way the fridge/freezer remains safe along with emergency lighting, this is how we set up caravans and motorhomes and the odd off grid set up. The warning alarm gives plenty of time to either fire up an auxiliary power source or minimise usage if it's in a quite time like after sun down or the middle of the night

T1 Terry

[offgridQLD]

I would agree on that voltage under that load though sustained 1C loads are not usually associated with off grid power systems.

The system in question is 180Ah x say 53v - 9500w load! that's never going to happen for any period of time with a 4000W inverter .

Typical off grid homes idle loads would be more like 50 - 300w depending on the system in question though by the sounds of it this one is going into a home with very frugal usage. Most likely would only see a few spikes of a few thousand watts throughout the day. Usually around short active times in the kitchen breakfast and dinner.

I always find it funny trying to relate the power electronics and baterys of our EV's to offgrid power electronics and batterys. Just how Huge the demands are from a Ev. I get all impressed when I see my PV pumping in 7000w. Or loading up my inverter to see 6000w output.

Then I back the Imiev out of the driveway and pull 20,000w followed by a roll down the street and regen pumping 30,000w into the batterys as I let off the accelerator. Amassing numbers when you try and relate the two.

Kurt

[PlanB]

Good point, I never did the sum to realise 1C is pretty unlikely for this. Makes the performance of battery management systems in EVs, where 1C or 2C is likely, look good.

[T1 Terry]

Good point, I never did the sum to realise 1C is pretty unlikely for this. Makes the performance of battery management systems in EVs, where 1C or 2C is likely, look good.

Battery management for house battery has very different requirements to EV battery management. These cells behave differently under light discharge and the cell capacity makes a huge difference to cell balancing using the discharge method or shuffle transfer. 0.5 amps will balance a 40Ah or 60Ah cell, but useless for a 400Ah to 1,000Ah cell. This requires a completely different management method, combine that with solar charging that can be any where from a trickle to over 100 amps yet only available for around 3hr in winter yet up to 10 hrs in summer and the EV battery management system would not even close to being up to the task.

T1 Terry

[weber]

Battery management for house battery has very different requirements to EV battery management. These cells behave differently under light discharge and the cell capacity makes a huge difference to cell balancing using the discharge method or shuffle transfer. 0.5 amps will balance a 40Ah or 60Ah cell, but useless for a 400Ah to 1,000Ah cell. This requires a completely different management method, combine that with solar charging that can be any where from a trickle to over 100 amps yet only available for around 3hr in winter yet up to 10 hrs in summer and the EV battery management system would not even close to being up to the task.

Our BMS has 0.8 A bypass and will be used with 180 Ah cells. I assume you're thinking of BMSs that don't control the charge current (except OFF or ON). Ours will attempt to throttle the charge controller back to the bypass current when the first cell is full, by using the serial input to the PIP-4048MS to send commands that reduce the absorb and float voltages.

[T1 Terry]

The trick is reducing the current down to 0.8 amps yet charging all the other cells, at the same time. Even a 0.1% out of balance equals a difference at that time of 1.8Ah between the highest and lowest cells and that will take a continuous 2 1/2 hrs to correct with a 0.8a discharge balancer. In the mean time the system is still in operation so the only time that imbalance will be seen is at the top of the charge, good luck with getting 16 cells within 0.1% balance during that period . As soon as you stop the charging the load will drop the high cell voltage and the 0.8a balancing will stop as the cell will no longer register the high voltage required to activate the discharge balancer circuit, so you won't get a 2.5hr crack at rebalancing the cells during the 5 peak sun hrs solar charging you get during summer, to make matters even worse, that's only 2.5 peak sun hrs during winter.

T1 Terry   

[offgridQLD]

Terry,
      Are you trying to suggest that 400ah+ lifepo4 cells in a offgrid aplication can't be top balances (to within aceptable levels say 10-20mv) using PV charge controllers and 800ma or so cell top balancing boards.

If so I would have to disagree and can link to some examples of people who have been susesfully doing it in Au for years. With detailed data logging of just how well its working.In fact what they are finding is after a fine comissioning ballance by hand. Once the cells are in operation powering there home .Is a very short absorb stage (triggering their ballancers)is needed to complete the balancing to satisfactory levels (around 20 mins).There just isn't much to correct. Some are just Setting a Eq charge once a week for 1hr at the balancing voltage they desire.The cells just don't drift much under light C loads and modest DOD levels.

Kurt

[T1 Terry]

48v 16 cell systems Kurt? 4 cell 12v system will stay in balance without any form of balancing attached, so the balance boards work fine on these 24v systems can be an issue, 48v system are most definitely an issue at the top end of the charge. If you are telling me you have witnessed 48v 400Ah systems that will remain within 10mV to 20mV at 3.6v yr after yr I'd be very interested in any information you have.

T1 Terry

[antiscab]

The cells just don't drift much under light C loads and modest DOD levels.

If they have never been overdischarged (been below 2v) than they don't drift at all

If you use a BMS like the ZEVA one, the shunts latch for some hours after charging stops (you can program how long for and such)

you don't need to be charging to do balancing - but you should start out with a balanced pack in the first place

[offgridQLD]

" If you are telling me you have witnessed 48v 400Ah systems that will remain within 10mV to 20mV at 3.6v yr after yr I'd be very interested in any information you have."

Im not saying some adjustment to the absorb time (or time spent balancing) isn't need if conditions change to much. Say a week of unseasonaly bad weather and high demand high DOD might require a extension of the absorb time. Though on average he is finding from 15min to 30min is all that is needed. so if you don't mind a little more time than is really necessary in absorb then a good 30min or a tad longer should cover it without to much user intervention. Though I think his aim was to keep the time spent at balancing voltages to a minimum to extend the life of the cells.


Lots of info spread across a forum but this thread has some details. Basically he started out with 16x400Ah blue sky energy/calb cells configured as 2p 8s with two cell balance boards for each 2p cell but soon after upgraded his inverter to 48v and reconfigured the cells to 16s 1p - 48v one one cell balance pr cell.

http://forums.energymatters.com.au/sola ... c5108.html

My personal view is its not the number (10mv - 20mv - 30mv) that's so important or worth being to pedantic about. More that it doesn't keep drifting over time. 5mv that becomes 500mv over a year isn't good but 50mv that stays that way all year is fine. We are just trying to avoid a exponentially larger drift in individual cell SOC.




Kurt

[weber]

The trick is reducing the current down to 0.8 amps yet charging all the other cells, at the same time. Even a 0.1% out of balance equals a difference at that time of 1.8Ah between the highest and lowest cells and that will take a continuous 2 1/2 hrs to correct with a 0.8a discharge balancer.

Bzzzt. Factor of 10 error. 0.1% difference would be 0.18 Ah and take 15 minutes to correct. But no-one cares about a 0.1% imbalance, so I'll just take your point as still applying to a 1% imbalance (which we barely care about).

We will manually balance them to better than 0.1% before they go into off-grid service, by leaving them charging from the grid at 0.8 A for as long as it takes. After that, the main cause of imbalance I've found is the variation in current drawn by the individual CMUs. But this variation is typically less than 1 mA. That should only require an average of 2 minutes balancing per day at 800 mA.

[PlanB]

Dave is it one of your cell top modules that will throttle the absorb & float voltages? If I took your cmds in on an RPi serial port & echoed them to the 4048 (so we can maintain our serial connection) then echoed the 4048 response back at you would your wait for ACK timing be generous enough to allow this to happen transparently?

[weber]

Dave is it one of your cell top modules that will throttle the absorb & float voltages?

Sort of. The present plan is to use the modified CMU that we call an IMU, for this. It lives on top of the current-shunt rather than on top of any cell. We would put it last in the comms daisy chain, instead of first as it is in Mexy. It would run a PI control loop on the maximum cell voltage, to keep it down to 3.32 V (76% SoC).

If I took your cmds in on an RPi serial port & echoed them to the 4048 (so we can maintain our serial connection) then echoed the 4048 response back at you would your wait for ACK timing be generous enough to allow this to happen transparently?

It would work because there is no wait for any ACK. Our BMS comms is strictly one-way, and if one command packet to the PIP-4048MS is corrupted and ignored, there will be another one along in 1/15th of a second if the value needs to change, and in one second if it doesn't need to change. And if any cell gets to 3.5 V then the IMU will turn off the battery contactor, and perhaps reconnect it and retry after some delay.