I am experiencing erratic behavior (in particular, sudden battery shut-down) in an SVolt 2.71 kwH LiIon battery which is connected in parallel to

• a MUST 3.6 kw hybrid inverter with a mains feed and a PV feed from Solar Array 1, and

• a Victron 30/100 solar charger with a PV feed from Solar Array 2

The conditions under which the battery pack suddenly shuts down are as follows:

• the battery pack has an SOC of well above 50% right up to 100%

• the PV voltage on Solar Array 2 drops from one moment to the next, typically in the late afternoon when it is cloudy and this array suddenly gets no more sun at all. On a cloudless day, i.e. when the transition from sun to no sun is gradual, nothing will happen.

• The battery shuts down without any warning and its red light for "fault" flashes. The entire system then shuts down.

• The log on the Victron charger shows that a significant voltage drop down to less than 24 Volt has occured - but it is impossible to tell whether that drop occurred before the shut-down (and thus due to the sudden drop in PV input) or after the system shut-down (i.e., due to the battery having been disconnected by its BMS)

• After a moment the battery pack will then automatically restart, and on second or third attempt so will the inverter. All readings will now go back to normal.

My first try was to replace the inverter with a smaller RCT 2kw which I had run for 4 years using the same configuration, but originally with an AGM 24 Volt battery pack. That configuration worked perfectly, but then also started giving me trouble once I switched from the simple and robust AGM setup to the SVolt lithium pack. I thought that the RCT had reached the end of its life and therefore replaced it with the MUST - but actually matters got much worse.

I must confess that I then blamed the MUST inverter for it - but it has been tested by the supplier and was found to be faultless. Moreover, when I reverted to the old RCT inverter for comparison the same problem eventually occurred - though not as often (maybe the simpler and smaller inverter is just not as sensitive and does not interfer with the battery pack as easily).

My last attempts at problem finding have now been the following:

(1) I isolated the Victron's second solar array at the combiner box, but left the Victron solar charger as such connected to the battery. Again, I experienced a shut down.

(2) Finally I then also completely isolated the Victron from the battery. So far, so good ...

Two questions:

One, does anyone have a clue what might be going on here? I read up on this type of configuration and it is apparently not unusual to run a system in this way - but maybe the SVolt's BMS is just so sensitive that it responds to some 'conflicting messages' being sent by the two independent MPPTs.

Two, would it probably help if I were able to establish a BMS cable link between the inverter and the battery pack? It would enable the inverter to operate based on accurate readings from the battery; however, the second MPPT in the Victron - which seems to play a major role in the problem scenario - would of course still run independently. All I could do on that side is to experiment with the Victron's charger settings (which are currently on LiIon, but could be set more conservatively, e.g. to lower values).

I'd appreciate some help with this mystery!

Edited July 24, 2025Jul 24 by Chris M

12 hours ago, Chris M said:

I am experiencing erratic behavior (in particular, sudden battery shut-down) in an SVolt 2.71 kwH LiIon battery which is connected in parallel

You need to establish exactly what is causing the Svolt to shut down. Not a problem connecting 2 Scc controllers to the same battery bus but the setting are important between the 2 controllers. The Voltronic inverters are famous to overshoot the voltage setting when battery is close to 100%soc with intermittent cloud and sun. You need to set the Must inverter bulk charge and float lower than the victron values( victron Scc's don't overshoot). Set the charge bulk voltage on the victron to 28v and the Must lower to around 27.5v. Go to the Svolt screen and see why it is shutting down? The manual explains the procedure.

Dear Talia,

many thanks, that (= "Voltronic inverters are famous to overshoot the voltage setting when battery is close to 100%soc with intermittent cloud and sun") makes a lot of sense. Unfortunately my SVolt Manual gives no explanation on what the various abbreviations (like: OVP, SCP, UVP etc.) mean and how to interpret the values - for example, what does "OVP: 8" exactly stand for? Do you perhaps know where I can find more detailed information on this? Sorry for the trivial question...

OVP = Over Voltage Protection
SCP = Short Circuit Protection
UVP = Under Voltage Protection

Thank you! The readings I get at current are

OVP: 111

SCP: 4

OCP: 37

UVP: 2

But unfortunately there is no documentation as to what the numbers mean - are these codes, incident counts, values? Would you have any idea?

2 hours ago, Chris M said:

Thank you! The readings I get at current are

OVP: 111

SCP: 4

OCP: 37

UVP: 2

But unfortunately there is no documentation as to what the numbers mean - are these codes, incident counts, values? Would you have any idea?

From the top

Over voltage protection

Guess short circuit protection

Over current protection

Under voltage protection

I am just repeating what has been mentioned.

These codes are what are used by a lot of solar charge controllers that can support lithium batteries as one needs to load your own settings for the batteries used.

Just Google and download this manual and you will find what the letters mean. The picture with the green text on a black background.

Edited July 25, 2025Jul 25 by Scorp007

Thanks, got it.

That is quite a lot of OVP's

Just check what the battery voltage shows on the SVOLT's display when just the inverter is charging the battery ( temporarily isolate the external SCC )

Compare that to what your inverter thinks the voltage it is putting in is.

I've seen the axperts over read by as much as ~1.5v causing the OVP's to be triggered on the battery BMS especially during float.

6 hours ago, Chris M said:

Thank you! The readings I get at current are

OVP: 111

SCP: 4

OCP: 37

UVP: 2

But unfortunately there is no documentation as to what the numbers mean - are these codes, incident counts, values? Would you have any idea?

The numbers indicate the amount of times the specific error occured. OVP (111): The battery was overcharged or subjected to a high input voltage often(111 times). This is very high and should be investigated possibly a charger with incorrect settings.

Post your charger bulk and float settings for the Must inverter and the Victron mppt.

Thank you both, Beauvedere and Talia - wow, 111 OCs is indeed a lot!

I have temporarily replaced the MUST with my old RCT to rule out any inverter fault; the problem occurs less frequently, but remains popping up.

As for the inverter charger settings: at current it is set to bulk = 27.5 Volt, float = 27.2 Volt. I also disenabled both PC arrays as well as cut the link between the secondary Victron SC and the battery, so the only charge current comes from the inverter - that worked ok for 2 hs, then another shut down. OVP count remained at 111 but OCP went up from 37 to 38.

As for charger voltage: the battery display shows 26.95 V at 82.71 SOC while the inverter measures the battery as having/being charged at between 27 and 27.2 Volts. However, a control measurement with my multimeter only gives me 26.0 at the inverter's battery cable terminals, yet 27.4 at the battery's end (I'm running 25 mm cables, 1.8m long and the max combined charging amps of the small RCT is set to 50 Amps, the utility charger to 20 Amps). Finally , battery cell voltages 1 to 8 are all between 3367 and 3370 mV.

What a conundrum...🤔🤔🤔

7 hours ago, Chris M said:

then another shut down. OVP count remained at 111 but OCP went up from 37 to 38.

What load is connected to the inverter? You must not exceed 2500w@24v = 104A as the overcurrent alarm(OCA) is set at 105A and the overcurrent protect(OCP) is set to 110A in the Pace bms.

Yes, but we're well below that as the system only provides power to lights and essentials, plus the pool pump. Even if everything is on we will only reach a max of 1.5 kw = 63 Amps, plus the RCT inverter shuts down when you exceed 2kw load anyway (I tested that).

But initially I thought along the same line as the faults seem to coincide with the start of the late afternoon run cycle of the pump: so I replaced the capacitor on the 650 Watt motor thinking that it might create extremely short power surges on start up which theoretically could reach up to way above 2kw, but wouldn't trigger the respective circuit breaker due to latency. Nice theory, but the problem persisted. I'll nevertheless give the theory another go and now just switch the pump over to utility for a day or two and see what happens then.

Dear All,

I'm happy to report that thanks to Talia's information about the Voltronics common over-shooting of the set max voltage and Mr.Beauvedere's input it seems I have eventually resolved the issue. I set the values on both chargers significantly lower than suggested by the SVolt manual:

• on the RCT: Bulk = 27.5 V, Float= 27.2 V, 'Back to utility'=25.5 V, 'Back to battery'=27 V

• on the Victron: Absorption = 27.39V, Float = 27.2 V. (There's no option to set Bulk voltage here)

This has now worked faultlessly for 3 days and the battery is being discharged down to 28% SOC and then charged to a max of 93 % - no more OVPs since. In the final analysis I guess it was in fact the much higher bulk settings on both the MUST and the Victron where I originally had programmed Float = 28 V as per the SVolt manual. OK, it's still early days, but I'm cautiously optimistic for once 😉

In the next step I will now exchange the RCT again for the MUST and test that with the same settings. The supplier has tested the MUST and claims it is absolutely faultless, plus they set what they claim to be the correct values. In previous communication with their texchnical expert they had suggested that I use Bulk charging = 28v , float charging = 27.2v and battery cutoff volts = 23.2v. However, in my installation these settings did not work with the MUST, and I guess that Bulk= 28 V is pushing it - hence the OVPs.

Anyway, many thanks for everyone's input! I exchanged countless eMails with the supplier, the SVolt and the MUST manufacturers, and none of them were able to help. But you guys were great!

Edited July 28, 2025Jul 28 by Chris M

Ah, here we go again... No more OVPs, but another OCP when there was minimal load. What's even more perplexing is that the OCP occured immediately AFTER an appliance responsible for a load of some 700 Watts switched off, thus REDUCING the current drawn by the inverter from the battery by some 30 Amps.

What also doesn't make sense is that in order for the BMS to trigger an OCP I would need to put a massive overload onto the inverter:

1. The SVolt is supposed to be able to deliver a current of up to 100 Amps, so I suppose its OCP

2. If maxed out my small RCT 2 KW / 24 Volt inverter will draw 83 Amps

3. The RCT can handle a power surge of 150% for 5 seconds - so under extreme conditions a load of 3 KW which would then result in a current of 125 Amps to be drawn from the battery for a max of 5 seconds before the inverter's overload protection kicks in

4. I simulated the above scenario by putting a 2500 Watt load onto the inverter - it behaved exactly as it should and cut out after 5 seconds while the BMS did not trigger an OCP.

A couple of questions then:

• I tried to find out from the SVolt manual at which threshhold an OCP will be triggered and what the latency of the BMS might be, but there's no information on this. Does anybody have an idea?

• Is there perhaps a way to reset / recalibrate the battery's BMS? I tried its reset button but that doesn't do anything

• As there is no way to access the BMS settings via the battery display I thought it might be possible to get into it via a USB to RS232 cable. Any advice on this? I was not supplied with such a cable and would need to get the correct one first. The supplier says that they don't provide it on purpose as the manufacturer doesn't want users to tamper with the BMS, which is at odds with the manual which tells you to install PMS Tools on your computer.

Any hints would be greatly appreciated!

BMS settings 25.6 volt 2.71kWh SVolt

I used the RS 232 port and made a cable to serial 9 pin connecter and use Pbms 2.4

PIN 3 TX

PIN 4 RX

PIN 5 Ground

There is some info on this forum to use the CAN port to USB