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Axpert MKS 5kVA PV Input disconnection & Reconnection

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babarshahzad123
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Axpert MKS 5kVA PV Input disconnection & Reconnection

Post by babarshahzad123 »

I have 03 Pcs Axpert MKS 5kVA inverters with each 4.5kW PV/Solar input is installed in parallel for single phase output configuration. I am facing one problem, a few times in a day inverters disconnect PV input with a click sound (relay operation) without any error indication and then load (about 4~6kW) comes on small 150AH, 48V battery bank. Within a minutes inverter takes PV input back and load shifted back on PV input.

This, some kind of PV input restart is a big burden on small battery bank and even sometime load is disconnected due to battery disconnection settings (45V), if anyone has experience on such kind of PV disconnection & re-connection, please support.

Thank You!

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coulomb
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Re: Axpert MKS 5kVA PV Input disconnection & Reconnection

Post by coulomb »

Welconme to the forum.
babarshahzad123 wrote:
Wed, 06 May 2020, 00:09
a few times in a day inverters disconnect PV input with a click sound (relay operation) without any error indication and then load (about 4~6kW) comes on small 150AH, 48V battery bank. Within a minutes inverter takes PV input back and load shifted back on PV input.
I suspect what is happening is that the voltage of your small battery is sagging under load, enough to trigger the inverter-charger to start a new bulk charge cycle. These PIPs are unusual in the way that they change from float charging stage to bulk charging stage; they do it via a ~15 second "zero charge" stage. Then, once charging starts again, they seem to spend ridiculous amounts of time at just one amp of charging, then ramping back to full charge current on a quite slow ramp. The result is some sixty seconds of the PV not fully supporting the load.

This cycles the battery a little, which as you've noticed is quite annoying. I wonder if it's some sort of lead-acid thinking, where it's perhaps considered "good for the battery" to " do a bit of work" and "wake up the lazy acid" or some such. My guess is that less than half the energy system batteries are lead-acid these days.

To see if this is actually what is happening, watch the middle "charge" led when it clicks off. If I'm right, you've been in float stage for a some time, and for the ~15 seconds it spends in the "zero charge" stage, the led would be off. When it starts charging again, it would presumably be in bulk stage, so the led would start flashing. I don't get this very often on my system, and my leds are hidden inside a box most of the time, so I can't be certain of this.

As for what can be done, there likely isn't much. Your battery is simply too small for your loads. With factory firmware or non-LFP flavours of patched firmware, this change from float to bulk stages is triggered by a 4.0 V drop in battery voltage for a certain length of time. I note in passing that even in patched firmware with KettleKomp™ (load and charge compensated battery voltage readings), we don't use a compensated voltage reading for this case. I suppose that's something that could be done.

* What chemistry battery do you have?

* What is the main firmware version in your inverters?

If you're not running patched firmware, it's possible that the battery is chronically under-charged due to the premature float bugs. Besides being bad for your battery, this could be increasing the internal resistance of the battery, which will make this problem worse.

* Are you confident that your battery is being fully charged?
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.

babarshahzad123
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Re: Axpert MKS 5kVA PV Input disconnection & Reconnection

Post by babarshahzad123 »

Thank you for the reply, Here are more details,

Batteries are tubular plate type 04x150AH. both float & bulk charge mode voltage are set as same 58V, since i am using batteries as cyclic order. Day time charging via PV and in night discharging with a small load. batteries are new and giving very good backup. Therefore I believe any change in float or bulk mode will not cause restart of PV input as both voltage are same. At lower load there is no PV restart, it happens when there is considerable load, i.e 25% or more.

All three inverters are of firmware 72.50, please refer snapshot from watchpower, highlighted data (30 Sec sampling) is the one when PV is disconnected. You can seen that there is almost constant load and battery charging current.
PV disconnected.JPG
PV disconnected.JPG (119.66 KiB) Viewed 98 times

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coulomb
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Re: Axpert MKS 5kVA PV Input disconnection & Reconnection

Post by coulomb »

babarshahzad123 wrote:
Wed, 06 May 2020, 16:42
Batteries are tubular plate type 04x150AH. both float & bulk charge mode voltage are set as same 58V, since i am using batteries as cyclic order.
Are those flooded? Otherwise, those voltages seem high for me, but I don't know lead acid batteries all that well.
At lower load there is no PV restart, it happens when there is considerable load, i.e 25% or more.
I've just realised that this is a sort of PV "dip" that I've seen reported by several inverter models. I've just now realised that this could be due to the "leaky bucket" exit from float to bulk charge stages (it also goes via "zero charge" stage). I will likely post more on this later. But I see that your inverters go to standby mode, with zero output. That seems different from others' behaviour, and seems serious to me. I have no idea at this stage what might be causing it.
All three inverters are of firmware 72.50,
So are these moderatly old units, like from early 2017? PF0.8 models?

Your device ID seems unusual; is it perhaps a clone?
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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