Victron Multiplus 24/2000 shutting off at beginning of charge-cycle

[herman2021]

I have a new Victron Multiplus 24V Compact and a new BigBattery 24V HAWK Lithium. When turning on the Multiplus it will go into Bulk Charging mode and make a hum for about 30-60 seconds then shut off completely. Another 30-60 seconds will go by and then it will turn on again and try again and shut off again. It will do this one or two more times and either a) keep going successfully, the hum gets quieter, and then eventually make it to Absorption mode or b) end in a Fault. I have a Cerbo GX and looked at the VRM logs and noticed "High DC Ripple" faults. Sometimes it says this in Victon Connect after it shuts off and other times it says nothing in Victon Connect... just that it is Off. I replaced the battery connections and feel pretty confident they are solid.

My Multiplus Charger settings are Current=50A, Absorption=29.2, Float=29.2 (29.2 was recommended in the HAWK "manual").

Any ideas?

Jeff

 

[sunshine_eggo]

What is the AC source?
How many amps is that source?

BigBattery specs are garbage. Please set to: 28.8V absorption, 27.2V float.

 

[MisterSandals]

Absorption=29.2, Float=29.2

BigBattery specs are garbage. Please set to: 28.8V absorption, 27.2V float.

Yea, my money is on the battery micro-cycling: charge, settle, charge, settle... cannot be good for battery or charger.

If this keeps happening even at 27.2V float, let your battery settle for a few hours without a load and set float just below that (or however much time YOU want between charge cycles).

 

[sunshine_eggo]

Yea, my money is on the battery micro-cycling: charge, settle, charge, settle... cannot be good for battery or charger.

If this keeps happening even at 27.2V float, let your battery settle for a few hours without a load and set float just below that (or however much time YOU want between charge cycles).

I think it's actually a mismatch between the MP settings and the AC source.

 

[MisterSandals]

I think it's actually a mismatch between the MP settings and the AC source.

What is the source of a high DC ripple fault? Related or caused by such a settings mismatch? (Trying to learn something here!)

 

[herman2021]

Thank you all for your replies.

What is the AC source?
How many amps is that source?

Standard 120V 15Amp residential service. I have the Multiplus set to not pull more than 12amps.

 

[sunshine_eggo]

Thank you all for your replies.

Standard 120V 15Amp residential service. I have the Multiplus set to not pull more than 12amps.

I would reduce your charge current to 45A to see it if addresses it. Additionally,

Is dynamic current limiter enabled?

Is UPS disabled?

Is PowerAssist enabled?

 

[herman2021]

My settings are:

AC input limit = 12A
Dynamic Current Limit = Enabled
Accept wide input frequency = Enabled
UPS = Enabled
Ground Relay = Enabled
PowerAssist = Disabled
Charge Current = 50A (I just changed it to the default 37A)
Absorption = 29.2V (I just changed it to 28.8V)
Float = 29.2V (I just changed it to 27.2V)
Conditional AC Input Connection = Disabled
Disconnect AC Input on = Battery Voltage > 32V

 

[sunshine_eggo]

My settings are:

AC input limit = 12A
Dynamic Current Limit = Enabled
Accept wide input frequency = Enabled

This really isn't needed unless you are on very dirty power.

UPS = Enabled

Consider disabling UPS for troubleshooting purposes.

Ground Relay = Enabled
PowerAssist = Disabled

PowerAssist is extremely useful, and it should be enabled unless you have an explicit reason not to. With it disabled, regardless of AC Input settings, charging + loads can overwhelm the AC input.

Charge Current = 50A (I just changed it to the default 37A)
Absorption = 29.2V (I just changed it to 28.8V)
Float = 29.2V (I just changed it to 27.2V)
Conditional AC Input Connection = Disabled
Disconnect AC Input on = Battery Voltage > 32V

What about "Weak AC Input" on the charger screen. This is generally not needed unless the power is very dirty.

Something to keep in mind:

When AC input is fed to a MP, it operates in passthrough mode to power all loads with the AC source. It will charge with any surplus current. If your loads < AC input, it can get ugly.

Lastly, DC ripple is often caused by insufficient wire gauge (current and/or length) or a loose connection. Worth checking every wire, connection and device between the MP and the battery for tight connections and for the presence of excessive voltage drop.

 

[sunshine_eggo]

What is the source of a high DC ripple fault? Related or caused by such a settings mismatch? (Trying to learn something here!)

Handling that separately. Mentioned it in the post above.

 

[herman2021]

Thanks! More settings:

Charge Curve = Adaptive + BatterySafe (but I've tried all settings and no improvement)
Weak AC Input = Enabled
Stop After Excessive Bulk = Enabled

I've checked the battery wiring and it seems pretty solid to me.

When AC input is fed to a MP, it operates in passthrough mode to power all loads with the AC source. It will charge with any surplus current. If your loads < AC input, it can get ugly.

I have no AC loads on the inverter during this testing.

I made the changes I mentioned in my last post and I still get the same behavior. I was watching Victron Connect very closely and when this happens the Battery Voltage had jumped to around 34V give-or-take. Can't tell if that jump was before or after the sudden shutoff of the MP... it all happens at the same time.

 

[sunshine_eggo]

That almost sounds like a BMS high voltage disconnect issue.

For giggles, reduce charge current to 5A and see if it goes away. Sneak up on it from the bottom.

What is the wire gauge and length?
And do you have any fuses/breakers between MP and battery?

 

[herman2021]

That almost sounds like a BMS high voltage disconnect issue.

Yes, it seems like the BMS gets unhappy and shuts down. I'm trying to check with BigBattery to see what their commissioning procedure is to ensure the cells are equalized, etc. on a brand new battery.

For giggles, reduce charge current to 5A and see if it goes away. Sneak up on it from the bottom.

I tried 5A and all is well. Will start creeping up.

And do you have any fuses/breakers between MP and battery?

I had a Bussman breaker on POS and a Victron SmartShunt on NEG. And then from those to the MP. But as part of my testing I disconnected all that and am currently connected straight from the battery to the MP. Still have the issue.

 

[sunshine_eggo]

Yes, it seems like the BMS gets unhappy and shuts down. I'm trying to check with BigBattery to see what their commissioning procedure is to ensure the cells are equalized, etc. on a brand new battery.


I tried 5A and all is well. Will start creeping up.


I had a Bussman breaker on POS and a Victron SmartShunt on NEG. And then from those to the MP. But as part of my testing I disconnected all that and am currently connected straight from the battery to the MP. Still have the issue.

Wire gauge and length?

 

[herman2021]

Wire gauge and length?

The standard 2' 6ga cable (4' "round-trip") from BigBattery.

I just replaced it with 2' 2ga cable and put my SmartShunt and ANL Fuse Holder back in the circuit adding another 2' of 4ga cable. Total of 4' of cable (8' round-trip).

I just increased to 20Amp charging and it worked well. Will try again with 30Amps.

 

[sunshine_eggo]

I like the sound of that.

6awg is marginal for that current @ 24V in my book.

 

[herman2021]

Well, looks like I can't go above 20A charging. I tried 30A then back down to 25A and both caused the shutdown. It happens at the end of bulk, just before absorption. At this phase the charging current is lowered down to 0 and then the MP tries to "test the waters" by increasing to the charge-current setting and sees the battery popping up in voltage and then the MP goes back down to 0 and then tries again and eventually after 3 or 4 times the MP senses it's done with bulk. But during this "testing the waters" with charge-currents higher than 20A it will, I guess, cause too high of a voltage on the battery and it shuts down.

 

[sunshine_eggo]

Dang, again, that sounds just like a BMS cut-off.

Bleed the battery down and try 27.6V absorption @ 45A. That should result in a very long absorption time and should eliminate the BMS as the issue at least at the bulk to absorption transition.

If that works, keep inching absorption up until the problem returns.

Hopefully, you can find something workable, and the batteries balance themselves if that's what's going on.

 

[herman2021]

Here's the latest... I called BigBattery and they didn't seem to have any experience with the MultiPlus and initially wanted to blame it on the MP. But after I pushed back a couple times they finally said to lower the bulk/absorption charge to 27.2V. They said 27.2-29.2 is considered full-capacity of their batteries. I asked why they advise 29.2V and I didn't get much of an answer. I asked if 27.2V will still activate the balancing logic in their BMS and they said it would. So I'm still at a loss as to why anything higher than 27.2V would be necessary if 27.2V is considered full and is enough to balance.

So... I set absorption to 27.2V and raised the charge-current to 45A. Worked great. I then tried 28.2V and the problem re-emerged. I then tried 27.8V and the problem re-emerged. I then tried 27.6V and the BMS didn't shut off completely when nearing the end of bulk but it did temporarily shut off the receive-charge (could pull current but could not put current back in to the battery). I then tried 27.4V and that seems to work fine like 27.2V does.

For each of these tests I first depleted about 11Ah from the battery.

 

[sunshine_eggo]

Their statements are conditionally true, but they lack explanation.

27.2 is 3.4V/cell. You can get them charged to about 95% at this level, but you will have a notably long absorption period.

27.6 is 3.45V/cell, and it will get you to 98%+ a little faster than when charging to 27.2V (3.4).

Assuming you're cycling the system regularly, I would run each absorption voltage for several days and then bump it up 0.1V until you can get to 27.6V. If you can get recharged in an acceptable time, that voltage reduces charging stress while still getting damn close to 100%. It should improve cycle life.

You should tweak your absorption time up/down as needed until the current is about 0.03C when it transitions to float.