question

morganb avatar image
morganb asked

Victron 12.8v Smart, VE.Bus BMS Low Voltage Recovery

Hi Guys

we have installed a system in a vessel and have had a Issue where the Shore power was kicked out and battery left to drain to around 9V, we have installed 20-30 systems so think we know he gear fairly well,

System
2 x 200AH 12.8 V Smart Batteries
ve.bus BMS
multiplus 12/2000/ Compact running latest 497 Firmware
BP200 for Loads
BP65 For DCDC chargers

- went to boat to find system at 9V or slightly less,
- Alarm not running As i assume to Low voltage for BMS
- Plugged in shore power nothing Came to Life
- Checked Charge current no Current


Question 1

By the Manual if the Mulitplus cannot see the VE.Bus BMS it should charge at 5a until it reaches it nominal Voltage (12v) , it suggests this can be tested by removing the VE.bus BMS cable from the Compact and this should happen

this in our case did not happen.
we also tried to re run the test with the batteries at 10V (less then the 12v) by pulling the BMS cable out of the Multi ( tired before or after the AC-Detector) never did we see any current Come out of the Multiplus Compact to attempt to recover the batteries,

Is this because its a Compact not a standard Multi??

Question 2

I think our buzzer helped drain the batteries to this level the Pre alarm does not seem to work as per manual, the alarm would sound 100% of the time while the loads have been switched off, meaning it will just keep draining untill the BMS switches off at max of 1A

See manual

In case of an imminent under voltage shutdown, the pre-alarm output of the BMS will switch on. In case the voltage continues to decrease, the loads are switched off (load disconnect) and at the same time the pre-alarm output will switch off again. In case the voltage rises again (operator has enabled a charger or has reduced the load) the pre-alarm output will switch off, once the lowest cell voltage has risen above 3.2V.

can someone explain why this is the case, and i have also seen this on another vessel also where loads are disconnected but Prealarm keeps going, ?

BMS
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2 Answers
ludo avatar image
ludo answered ·

I guess you don't even have the power to enable the BP65 for the chargers.


Get yourself a 12v battery and some jumpstart cables to prime the battery. If you're worried about the current put a 12v 100w lamp in series, don't burn your fingers. When the lamp is dark the battery is primed, BMS and BP65 should work again.

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Stefanie (Victron Energy Staff) avatar image
Stefanie (Victron Energy Staff) answered ·

@MorganB

Answer 1 - They are quite similar with the exception that the 12/2000 Compact requires DIP switch 1 off and ds 2 on for a system with VE.Bus BMS.

Answer 2 - Is that your guess or is that exactly what you experienced? I tested this and it is not the case in my setup. Remember that the pre-alarm depends on the pre-alarm setting in the battery signaling this to the BMS. If it's set too low, it can appear like it won't turn off. Leave it at 3.10V

Note that the VE.Bus BMS will not work if the battery voltage drops below 9V, preventing the Multi from starting.

You might get away with it if you follow the recovery procedure explained in the Lithium Battery Smart manual, but it depends, among other things, on how long the low cells have been been below 2.5V.

Caution: Do not use jumpstart cable as suggested in the other post. This is completely uncontrolled and most importantly dangerous. This will not bring your battery back to life.

And a last word: The BMS load and charge disconnect should be considered as the very last resort to protect the batteries from deep discharge. And even if that happens, there is never much time to recharge the battery in time because parasitic loads, even in the milliampere range, can continue to discharge the battery, be it through the BMS's own consumption, the battery monitor or the battery's self-discharge.

So you have to take precautions to prevent it from happening in the first place. This also includes not leaving the system unattended for weeks or months.

3 comments
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Matthias Lange - DE avatar image Matthias Lange - DE ♦ commented ·
to add:

Is the mains detector installed?


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morganb avatar image morganb Matthias Lange - DE ♦ commented ·
Yes mains detector is added
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morganb avatar image morganb commented ·

to answer your questions,

1, Yes we have set dipswitches correctly

2. yes this is what i experienced and have had another client also experience the setting is set to 3.1v as factory. so can you explain how it worked for you, the Alarm stayed on after the load was turned off and stayed on, in my case i was not on boat when it got to BMS shutoff 9 v, but when we got back above 9v the alarm stayed on all the way untill the 3.1v, my reading of manaul the alarm only sounds between 3.1v and Load disconnect,

Note that the VE.Bus BMS will not work if the battery voltage drops below 9V, preventing the Multi from starting. this comment i agree with but in the manual it sates if the multiplus does not detect a BMS or BMS under 9v the multi will start charging when ac detected with 5a current until the bms is active or nominal voltage reached, this did not happen

agree with you last comments client was complacent and refused to pay for a Cerbo to get the system online to keep an eye on,


effectively what I'm saying with all this is it seem to me the manual or system is wrong on 2 levels

1. the pre alarm does not shut off when expected and we think this contributed to the low SOC

2. the Multiplus compact did not do its job in recovery requiring us to manually charge,

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