BMS warming light and buzzer before disconnect

[AKA-None]

Personally I don’t see an issue with a device able to look at current draw, rate of change, and at least temperature to make a prediction that “at this rate there will be an over current shutdown “
Or are we not talking about anything that smart

[wholybee]

Originally Posted by AKA-None

Personally I don’t see an issue with a device able to look at current draw, rate of change, and at least temperature to make a prediction that “at this rate there will be an over current shutdown “
Or are we not talking about anything that smart

You can't predict over current like that. If you turn on your electric cooktop and it draws 200A, there is no way any BMS could have predicted you would do that. And, if that 200A caused an overcurrent situation, it needs to be remedied immediately, not after an alarm.

You can predict a low voltage cutoff that way to some extent.

[SaylorMade]

Originally Posted by AKA-None

Personally I don’t see an issue with a device able to look at current draw, rate of change, and at least temperature to make a prediction that “at this rate there will be an over current shutdown “
Or are we not talking about anything that smart

Over current protection should absolutely kick in at the instant it is detected.
You can allow certain periods of "boost" where higher current draw is allowed, but not to any extent.

Low and high-voltage, and temperature (to a certain extent) could be ok to have short grace period where a buzzer sounds.

But the requirement does not allow for such nuances, and these grace periods should in any case be very short, so how is it useful anyway?

[SaylorMade]

Originally Posted by wholybee

You can't predict over current like that. If you turn on your electric cooktop and it draws 200A, there is no way any BMS could have predicted you would do that. And, if that 200A caused an overcurrent situation, it needs to be remedied immediately, not after an alarm.

You can predict a low voltage cutoff that way to some extent.

Since we do not have a "Like" button here, I'm gonna leave you this

[fxykty]

Prediction doesn’t make any sense.

For all the usual triggers of disconnect, such as high voltage, high temperature, voltage imbalance, low voltage, the condition does not require an instant response. So it’s certainly feasible to have the disconnect event trigger an alarm when it’s detected and to have a 1 minute or 5 minute delay before changing the state of the relay to disconnect the battery.

Over current is a different kind of fault and that’s what fuses are for.

[ben373]

I would imagine that the BMS or possibly another device has a set of parameters for the warning.

Such as high voltage disconnect maybe set at say 15v by the BMS but you get the warning at 14.7

Maybe a market for such a standalone device.

[smac999]

I'm going to bet that over half the boat lithuim batteries now in service are internal BMS, and have no way to connect any warning.

[djdeakyne]

If a BMS has User Defined outputs, this can be a fairly straight forward implementation.
REC has User Defined Optocoupler Outputs and the Elecrodacus calls them EXT IO ports. All you have to do is set them to trigger .2v or so prior to the main contactor's voltage and wire it to a buzzer or relay/alarm.
There may be other DIY BMS's out there that have multiple outputs but I know these and therefore my $.02. Cheers, Dave

[mstr_cmdr]

Not quite the Whole Story:

Pantaenius also requires that the lithium battery system be installed by a licensed electrician and that a certificate be issued stating the installation meets AS/NZ Standards 3004; that the certificate includes the name, licensed contractors registered number; and, on the contractor's letterhead, with all pertinent details.

[SaylorMade]

Originally Posted by mstr_cmdr

Not quite the Whole Story:

Pantaenius also requires that the lithium battery system be installed by a licensed electrician and that a certificate be issued stating the installation meets AS/NZ Standards 3004; that the certificate includes the name, licensed contractors registered number; and, on the contractor's letterhead, with all pertinent details.

Do you have some example of this in the exact wording?
Not doubting you, but I am curios to see how they define "lithium battery system".

Must also be country specific? I just went through their requirements in my country and no mentioning of Lithium batteries anywhere.

[Mattzilla]

My X2 BMS has this function. Battery balance X2 has pre alarms and led indicators.

[sailingharry]

So a lot of discussion about disconnect on overcurrent and how to alarm. You will notice that the listed spec doesn't even have disconnect on overcurrent as a requirement. The only BMS that disconnect on overcurrent are simple units that can be overpowered. A good BMS does not have an over current trip, and fuses are just fine.

Over and under voltage and over and under temperature all have leading indicators. They are super easy to implement a pre-warning that will be many many minutes in advance.

I will probably be going lithium this winter. There will be an over voltage and undervoltage cut out that will trip the main contactor, but that should be such an extreme case that it may never happen in the life of the battery. However, several tenths of a volt before that condition, the BMS will trigger an audio and visual alarm. In the high voltage case, it will also disconnect or shut down all charging sources. Similarly, in the low voltage case, it will shut down the inverter. I'm not entirely sure how I will handle the temperature requirements. Low temp disconnect is actually inappropriate, as a low temp shut down of charge sources is all that is necessary. In any BMS disconnect, I will have ample time to consider a response.

The above listed standard, quite similar to the abyc standard, makes tremendous sense. How can anyone enthusiastically endorse a system that will with no warning disconnect your main battery. Imagine motoring into a strange and tricky entrance when the BMS decides that you are overcharging the battery and shuts down your navigation system and depth instrument. I certainly wouldn't stand for that! I agree that while at sea having a complete shutdown of all electrical systems due to a low voltage condition is unlikely, of little consequence, and appropriate punishment for failing to monitor your battery SOC.

[Robertkwfl]

Originally Posted by sailingharry

The above listed standard, quite similar to the abyc standard, makes tremendous sense. How can anyone enthusiastically endorse a system that will with no warning disconnect your main battery. Imagine motoring into a strange and tricky entrance when the BMS decides that you are overcharging the battery and shuts down your navigation system and depth instrument. I certainly wouldn't stand for that! I agree that while at sea having a complete shutdown of all electrical systems due to a low voltage condition is unlikely, of little consequence, and appropriate punishment for failing to monitor your battery SOC.

Totally agree. While any system can fail without notice, a BMS is an automated system that can shut down every electrical device on your boat—for a variety of reasons. Where an approaching shutdown condition can be predicted, it makes sense to warn the operator. A prudent sailor should also think about how to power critical devices like autopilot and running lights in event of a shutdown.

Most Victron BMSs have pre-alarm capabilities.

[mstr_cmdr]

Originally Posted by SaylorMade

Do you have some example of this in the exact wording?
Not doubting you, but I am curios to see how they define "lithium battery system".

Must also be country specific? I just went through their requirements in my country and no mentioning of Lithium batteries anywhere.

As required by Pantaenius (Australia):

Please note that you are required to notify us if you have Lithium Batteries installed on your Vessel.

If your installation was completed by a Licenced Electrician and the installation meets AS/NZS 3004.2, / or Equivalent CE or ABYC standard. Pantaenius will note this on your policy file and there will be NO deduction in Cover applied to your policy associated with Lithium Batteries.

What we need!

We require a statement from a Licenced Electrician stating that they have inspected your battery installation and confirm that it meets or exceeds AS/NZS 3004.2.
The brand of the batteries must be noted on the statement.
The statement must be on the Electrician’s letter head which must display their License NO.

Hope this assists.

[svmatilda]

The requirement to monitor voltage and temp of each cell in the battery is going to need extensive work to retrofit and would almost need the batterys (several cells make a battery) to be fitted with sensors during manufacture. In the specs "The BMS shall continuously monitor the voltage and temperature of each cell in the battery" This is not going to be a simple SOC meter but going to need a specialised system with multipul sensors.

Then once you get over this hurdle then you may find the next is that change to a Lithium may not be certified for the vessel in question. You also will need certification of the install to be covered by insurance.

I have heard some have been knocked back on a claim if the system is not certified, putting in Lithiums is not really a job that should be done by an amature (a lot have i know) and I guess now those failures are starting to cut into the insurance companys bottom line.