Smart BMS CL 12-100. Does it stop charging from the alternator due to low battery temperature?

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valden asked Mar 17, '24

Smart BMS CL 12-100. Does it stop charging from the alternator due to low battery temperature?

Does the Smart BMS CL 12-100 actually stop the charging current from the alternator from passing through it and to the positive bus bar if a low temperature alarm is received from a lithium battery?

The Smart BMS CL 12-100 in my boat is installed in the usual way, with the alternator connected to the alternator post and the positive bus bar connected to the Li-ION post. This means that this BMS is the only device between the alternator and the bus bar. So if the BMS receives a 'too cold' signal from one of the Smart Lithium 12.8V batteries, does it cut the charging current from the alternator? Hopefully, the answer is 'Yes.' Is it? Thanks.

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Edit: I have found this info on the product brochure for the Smart BMS CL 12-100:

"It monitors and protects each individual battery cell within the battery (or battery bank) and will disconnect the alternator, charge sources or DC loads in case of low/high battery cell voltage or high temperature."

OK, the Smart BMS CL 12-100 will disconnect the alternator in case of high battery temperature. What about low battery temperature?

The reason I am asking is that the boat will be used in the Arctic, where the temperature of the batteries is likely to fall below 5ºC on occasions. It seems that if the engine is started when the batteries are below 5ºC, the alternator will pump charge through the Smart BMS CL 12-100, even though the batteries are signalling to the BMS that they are too cold to be charged.

I am aware that the minimum 'allowed to charge' temperature can be adjusted within the batteries, using the Victron app via Bluetooth connection. However, it seems that Victron have a good reason for setting the allowed to charge temperature at 5ºC, as warranty is voided if it is set lower than this. While my batteries are no longer covered by the two year warranty, I don't want them to be damaged.

So, while I was hoping that the answer to this question would be, 'Yes, the Smart BMS CL 12-100 will stop charging from the alternator if the battery is too cold,' it seems the answer is, 'No, it won't stop charging from the alternator if the battery is too cold.'

I would really like clear confirmation about this and if possible, some detail on why the design of this BMS only cuts charging for high temperatures and not low. I have some ideas about why, along with a workaround using a relay, but I would like to hear Victron's thoughts on this. Thank you.

BMS alternator

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klim8skeptic ♦ commented · Mar 18 at 09:58 AM

@Valden Question forwarded on.

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kcbuild commented · May 19 at 06:52 PM

Also very interested in a definitive answer to this question. It seems like the Smart BMS contactor should act as a back up and open if the battery temperature is too cold to allow for safe charging.

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Answer 1 · 2024-05-20T08:57:11Z

klim8skeptic answered · May 20 at 08:57 AM

@Valden @kcbuild Looking at the Smart Lithium Battery manual , the battery will instruct the BMS to disable charge should the battery be too cold.

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valden commented · May 20 at 09:21 AM

Hello klim8skeptic. Thanks for this thought. Sorry, but it's not a definitive answer. Let me explain why. While it's true that the manual for the Smart Lithium Batteries states that cells can tell the BMS to disable charging, the manual does not take into account that there are different kinds of BMS with different function sets. It's likely that all of Victron's BMS have the ability to cut charging by controlling what connected Smart Battery Protect devices do, but not all of Victron's BMS have the ability to pass alternator output through to battery bus bars. The Smart BMS CL 12-100 was developed to do this specifically, while protecting the alternator and the batteries from each other.

As such, the statement you've found in the battery manual does not cover the instance of charging management I'm asking about in this thread. The question has not been answered yet, but needs to be. It is:

'Does the Smart BMS CL 12-100 stop charging from a connected alternator if a battery cell is too cold?'

Anyone? :-)

Thanks.

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klim8skeptic ♦ valden commented · May 20 at 09:46 AM

@kcbuild Your right neither the manual, datasheet, BMS overview mention charge disable at low temps.

@Guy Stewart (Victron Community Manager) could you clarify this?

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valden klim8skeptic ♦ commented · May 24 at 07:45 AM

@Guy Stewart (Victron Community Manager)

Hello Guy. A few years ago you asked me if you could do a story about this boat, which has a substantial and complete Victron system. It's on YouTube. The boat is about to attempt a journey through the North West Passage, where water temperatures will be colder than around northern Norway, which you and I were discussing at the time.

Can you please ask the right person in Victron to address this question, before the attempt fails due to a failure in the charging of Victron's batteries. Nobody wants that. We need to know if we can rely on the Smart BMS CL 12-100 to stop charging from the two alternators if battery temperature falls below the set minimum, which is presently 5 degrees C. The documentation is not clear on this.

Thank you. :-)

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Guy Stewart (Victron Community Manager) ♦♦ valden commented · May 25 at 12:16 AM

Hi @Valden

I've asked internally if someone at Victron can get back to us with an answer

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Answer 2 · 2024-05-28T05:47:35Z

Guy Stewart (Victron Community Manager) answered · May 28 at 05:47 AM

Hi @Valden

This was the answer I got back from Johannes;

The battery is the source of alarm so if that’s disabling charge due to temperature or voltage condition the BMS follows and stops the charge.

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valden commented · May 28 at 08:02 AM

Hello Guy.

Re this answer from Johannes, I'm going to hold up a score card that says, 'Bedankt. Leuk geprobeerd, maar geen sigaar.' Thank you. Nice try, but no cigar. :-)

Of course, if a battery sends an alarm to stop charging, a Victron BMS will use its Charge Disconnect port to signal to another device to stop charging. This was not my question.

My question was carefully framed to ask about the Smart BMS CL 12-100. This BMS has two ways to control loads and charging. It can signal to other devices via its Load Disconnect and Charge Disconnect ports, and, it can control charging from an alternator itself, internally.

As mentioned in my question, the instruction manual for the Smart BMS CL 12-100 states:

"It monitors and protects each individual battery cell within the battery (or battery bank) and will disconnect the alternator, charge sources or DC loads in case of low/high battery cell voltage or high temperature."

This statement specifically excludes low battery temperature. The clear implication is that it doesn't stop charging due to low battery temperature.

I don't want to labour the point, but people are about to risk their lives attempting the North West Passage, relying on Victron Energy systems. We need a proper answer to this question.

Could you please ask Johannes or a colleague to address the question that I asked, with a reply that is framed in terms of the language used in the question. This helps ensure that the answer hits the spot. :-)

Thank you.

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