Victron Smart Battery Sense.

[noelex 77]

I purchased one of these devices recently.
For those of you who are not familar with the Victron products:
The idea is to attach this small device directly to your house battery terminals. It will then comunicate battery voltage and temperature via bluetooth with Victron solar controllers (and other charge devices).

As it is measuring the voltage directly at the battery terminals, the result will be more accurate than when measured directly via the solar controller, as the latter is subject to voltage drop in the wire and the fuses etc between the solar controller and the batteries. Unfortunately, this voltage drop is dependent on the current in this wire so it cannot be adjusted by altering the charge set points. The magnitude of this voltage drop will vary significantly with the installation, particularly with the distance between the solar controller and the gauge of wire used.

The second function of the Smart Sense is to communicate the battery temperature. Battery temperature is important when charging lead acid batteries, as it alters the recommended charge set points (absorption and float voltage). The solar controllers without any accessories can measure temperature and adjust the charge parameters automatically, but the temperature at the solar controller is often significantly different to battery temperature so without an accurate reading of battery temperature this feature is near useless. The Smart Sense has the ability to convey the correct battery temperature.

The final advantage of the Smart Sense is for people with multiple solar charge controllers. The battery voltage read by each of the charge controllers is generally slightly different due to calibration and manufacturing differences. If the wiring is similar, this tends to be a reasonably constant error and can be partially adjusted for by slightly altering the charge set points. For example, my port solar controller reads 0.02v higher than the central controller. This sounds very little, but unless this is adjusted for, the port solar controller can be counting down the absorption timer for much longer than the other solar controllers. This can be adjusted by altering the charge set points of the port solar controller by 0.02v. The Smart Sense removes the need to do this, and is more accurate, as all solar controllers now recieve voltage information from the same source (the Smart Sense) eliminating any difference.

Finally, Victron have promised that with the next firmware release (1.47), a network with the Smart Sense will allow all solar controllers to coordinate their charge algorithm so they will all drop to float at the same time. This will be help for those with unresolved charge coordination problems.

The Smart Sense is very easy to fit, has only two wires and has its own fuse holder. The other good news is the reasonable price, about $50.

The biggest drawback is the poor range of the Bluetooth communication. There are two versions: normal and the “long range” model. However, in my case even the long range model failed to reliably contact the solar controllers when attached to the batteries. Having read similar user reports from those with a reasonable distance between the batteries and controllers, I expected this. I have an aluminium waterproof bulkhead between the batteries and the solar controllers so the unit did not stand much chance even with the waterproof door open. You might think this renders the unit usless, but this not the case. By feeding some wires directly from the battery the Smart Sense can be mounted remotely. As these wires carry almost no current, providing the wire gauge is reasonable, the reading will still be accurate and the Smart Sense can be placed close to the solar controllers and in direct line of sight. Of course, the battery temperature measurement is no longer accurate so part of the functionality of the unit is lost, but given the low cost, the voltage (and future charge synchronisation) abilities still make the Smart Sense worth considering.

Hopefully the above user report is helpful, although the real test will come after installing 1.47. It is worth noting there are other Victron products that perform the same functions as the Smart Sense. Some of these also measure current entering the battery, which can be used to terminate the absorption phase more accurately. However, these products are more expensive and complex than the SmartSense.

This is what the unit looks like (Victron photo):

[john61ct]

Very odd the BT is the only data medium, one would think adding a hard wired option would not have cost much.

OTOH it is universally advised to place your charge source as close as possible to the batteries, so long as not directly above an FLA bank where electronics are susceptible to corrosive fumes.

But other devices are also consumers of such data, I can imagine a setup where this unit could be used for monitoring only, not by any charge source.

Hopefully this will be corrected in future.

[john61ct]

Given how generously supportive Victron is of open-source development, I'd bet a mcu-based project shows up that reads the BT data and "translates" to the various wired protocols.

Not just Victron's proprietary ones but BMS / charger compatible CANbus dialects, isoSPI,
M-BUS, MQTT, IOT-bus / NB-IoT, maybe even LoRaWAN

[noelex 77]

Originally Posted by john61ct

OTOH it is universally advised to place your charge source as close as possible to the batteries, so long as not directly above an FLA bank where electronics are susceptible to corrosive fumes.

This is good simple advice, but close to the batteries is not always the best solution for a solar controller on a boat so it is better to evaluate each case. For our electrical system installing the solar controllers close to the batteries was not logical.

It would be nice is Victron made a wired (as well as a Bluetooth) Smart Sense . As the communication ports are available and the protocol is open I am sure a Raspberry Pi version could also be cobbled up by an enterprising owner.

Some adjustment to calibrate the output (especially voltage) would also be nice so perhaps Victron can incrorporate this into a future firmware update for the Smart Sense.

[john61ct]

Example application, if OP considers this a derail and anyone wants to discuss further, I'll branch off a new thread.

_____
Elcon chargers fitted with the CANbus option can be programmed to start charging / continue charging only so long as they are receiving an OK signal iirc every 5 seconds.

So the FOSS MCU device located near the bank, keeps receiving the BT signal from the bank post's SBS, and it keeps sending that OK signal over a secure wired connection every second.

When the bank reaches the termination setpoint you've programmed, **or** temperature goes too high (also user defined), **or** any of these control elements fail

then the signal no longer being sent, causes the charger to shut down within 5 seconds.

[noelex 77]

Originally Posted by john61ct

then the signal no longer being sent, causes the charger to shut down within 5 seconds.

I don’t think this type of protection old be an advantage for the Smart Sense. If communication between the Smart Sense and the solar controllers is lost the chargers would default to their own internal measurements which is fine. In most cases this would be far preferable to shutting down the charging.

Voltage drop will tend to cause the internal charge controllers to measure a slightly higher voltage when supplying current. Temperatures are also likely to be higher at the charge controllers. So the small discrepancies, even if they were significant will be on the safe side .

The only exception is with Lithium battery chemistry where it may be desirable to disable battery charging at very low temperatures, but this function would normally be managed for all charge sources by the BMS.

[john61ct]

Originally Posted by noelex 77

I don’t think this type of protection old be an advantage for the Smart Sense. If communication between the Smart Sense and the solar controllers is lost the chargers would default to their own internal measurements which is fine.

Sorry I was not more clear.

Note with LFP or any chemistry, it is even more critical to terminate charge based on an overtemp condition.

And yes, disabling charging when temps get cold is especially important for LFP.

My example was repurposing these sensors for general use, no longer (necessarily) in conjuction with any solar controllers present.

As an alternative to the BMS in an LFP setup doing charge control, since most are not failsafe as I described above.

And I prefer to usually keep BMS functionality limited to protection only, not normal day to day operations.

So the goal above is a generic central charging controller (overseer?) based of the sensor readings, independent of any particular other brand components, just using the Elcon charger as an example.

Could be adapted to simple contactor control, or interfacing with a Wakespeed alternator VR, etc etc.

[Pete7]

Originally Posted by noelex 77

I purchased one of these devices recently.

Good aren't they We have had ours for a month but spending Christmas on the boat has given me chance to look up the data on a regular basis. Water temperature is currently 8c and feels like it when you run the cold tap. The batteries in the bilge behind the engine also report similar temperatures. Interestingly, after motoring for 3 hours on Christmas morning the battery temperature was 18c from the nearby engine heat even though the batteries are in separate batteries boxes. Same again this morning.

Be interesting to see what happens during the summer if we have to motor any distance.

I am not really into apps and stuff, but the Victron network app which is used to set up the smart controller to the BT widget was delightfully simple and now easy to monitor both the smart controller and BT in an instant on an old iphone.

The battery voltages are high because we have just plugged into shore power for some heat, tad cold, damp and misty this morning in England.


Pete

[tanglewood]

Thanks for the report. This is great to know, and to me makes it a viable product, sort of. As you point out, you lose temp sense which for LA is an important piece. I have LFP, so don't care about that part.


But I'm with you on really wanting a wired version. I love the idea of bluetooth and an app for configuration. But I have an inherent distrust using wireless for anything where operation is critical, or unattended. It's just too undependable in my experience.

[noelex 77]

Originally Posted by john61ct

Sorry I was not more clear.

Note with LFP or any chemistry, it is even more critical to terminate charge based on an overtemp condition.

I am not sure the Smart Sense is suitable for this. Something that can shut down all charge sources is needed, not just the Victron units and if the goal is trying to detect a fault condition (rather than general battery temperature), the SmartSense is not going to work as it will only measure the temperature of one cell.

[john61ct]

Originally Posted by noelex 77

I am not sure the Smart Sense is suitable for this. Something that can shut down all charge sources is needed, not just the Victron units and if the goal is trying to detect a fault condition (rather than general battery temperature), the SmartSense is not going to work as it will only measure the temperature of one cell.

The SBS is just used as a self-contained temp+voltage sensor that transmits that data via BT.

It was not my intention to get into the overall system design here, just pointing out how these units **could** be used in an open-hardware context, as **one** handy component.

You can use more than one if you feel necessary,

this is just one "pack level" sensor, for protecting against gross fire risk from thermal runaway or against deep freeze conditions as you suggest

but although the mcu may well collect data off other temp sensor types as well, I've never seen any such system use one per every cell, IMO that would be overkill.

Obviously what you **do** with the data, control logic etc, gets programmed into your mcu based (FOSS) software project.

And, as already stated, I just used the Elcon as one example, each charge source could have their own signal / control mechanism, or contactors just remove that bank off the charge buss leave the source running for others, powering loads or whatever.

[Yellowjacket]

I'd purchased and installed the Victron Smartsense for the reasons given, especially for providing accurate house bank battery temperature to solar controller. However, as pointed out, bluetooth signal was so weak it could not be detected by smart phone nor iPad less than two meters directly above the battery box through thin wood deck, let alone by solar controller four meters away at battery bus on the other side of bulkhead in engine room. Victron is aware of the issue.

The Victron 712, as pointed out, is more expensive and complex, but hard-wired to a display which has a far better bluetooth signal and no problem communicating to solar controllers. The 712 has its own interesting quirk, in that reported voltage changes if the LCD dsiplay is illuminated or not. Also, one has to decide whether it's more importqant to read house bank battery temperature or voltage at a second battery, say the start battery.

[roland stockham]

Is this an addvertisement for Victron? I don't see any question or information other than what is in the catalogue. I am sure, like all Victron stuff, this is well built and does what is says but I can't personally see any need for one except maybe to compensate for very poor battery placement or undersized wiring.

[john61ct]

The standard use is temp-compensating for lead batteries.

The smaller MPPTs don't do temp sensing well, and not everyone has a BMV.

Plus better voltage accuracy.

Of course many don't care about such details but for those who do, and for whom $50 isn't much, they're great

[Pete7]

Originally Posted by Yellowjacket

I'd purchased and installed the Victron Smartsense for the reasons given, especially for providing accurate house bank battery temperature to solar controller. However, as pointed out, bluetooth signal was so weak it could not be detected by smart phone nor iPad less than two meters directly above the battery box through thin wood deck, let alone by solar controller four meters away at battery bus on the other side of bulkhead in engine room. Victron is aware of the issue.

Oh, kind of makes me glad I opted for the slightly more expensive blue version with a claimed 10m range over the black 3m version.