To protect lithium batteries from charging below 0C, I see that you can set a minimum charging temperature, which will force float mode if the battery temperature falls below this value. Likewise a BMS with a charge/no charge relay + temperature sensor could trigger the WS500 input and force float mode. If you use Amp regulation in float mode (LIMIT_FLOAT_AMPS=0), will this override the float voltage in order to maintain zero current in/out of the battery? For example, in the morning you might have a battery below minimum charging temperature at a low SOC with a voltage below the set float voltage. When starting the engine/alternator will the WS500 lower the output voltage to below the float voltage set point in order to prevent current flow into the battery? Or do we also need to set a very low float voltage to protect the battery in this scenario?
Good question. Al, would you like to respond to this one?
@al-thomason
@rick-admin
You bet.
This is a great question, with actually a number of points to bring forward. As an overview - the WS500 regulator considers many points when making the decision on how hard to drive an alternator: Battery Voltage is certainly a key one, but other considerations include any limit on amperage that has been put in place, temperature adjustments and cutoffs, as well as alternator temperature. This is just a few. In totally there are perhaps 8-10 different items considered with the most restrictive one at any point in time \'wining\' if you will.
Looking at the case above, the short answer is: If battery temperature is below the cut-off point, no charging will be allowed. Does not matter if one is in bulk or float or... if below the hard stop limit - the WS500 will hard stop and not allow any charging.
Now in addition to the hard temperature cutoffs there are also soft cutoffs. Refer to the \"Reduced Charge..\" parameters in the $CPB command. These allow one to set trigger temperatures as well as voltages which when exceed will place a cap on the amperage that is allowed into the battery. Letting a chilled battery warm up slowly for example. (All these hard and soft limits are applicable at high battery temperature as well). Using this one is able to safely bring a rather chilled, but not stone cold, battery slowly to its operating temperature. It also allows for pull back on a battery that is getting too hot, allowing it to cool off some with the eye towards preventing a hard cutoff.
Another detail contained in your question is how the float target voltage and amperage limits interact. Referring to above, if battery current is targeted for 0A, the WS500 will adjust the alternator output to regulate on the battery amperage - keeping it centered around 0A -- even if the that results in battery voltage settling under the \'target\' float voltage. Most time we see this, where the float might be set at 13.38v, but when actively regulating battery acceptance current to 0A, the resulting battery voltage is lower, maybe 13.3 or 13.27v. So in this case, the 13.38 becomes more of a safety backstop then the prime control point. Meaning, that while in Float, the regulator will not allow VBat to raise above 13.38 (if so configured), even if it means battery current falls below 0A. You can actually see this at the transition from Acceptance to Float, when Vbat is still high until the \'Surface Charge\' in effect bleeds off - the regulator will halt output because Vbat is above the 13.38 target, amperage will likely be a negative value as house loads are supported. But once Vbat drops below 13.38, the WS500 will begin applying drive to bring the amperage towards its target 0A value.
A lot of details in here, and I hope it goes to show the care the WS500 takes to protect the battery while also providing for proper charge management. Do let me know if this is clear and addresses your question, and feel free to post any follow up. Thank you for considering the Ws500 Alternator Regulator.
-al-
Thank you for the detailed response! So in normal operation if LIMIT_FLOAT_AMPS=1, the alternator will provide a 1 Amp current to the battery so long as Vbat < Vfloat? If Vbat is > Vfloat, then the alternator will no provide current to the battery regardless of the float Amp setting? However if float was triggered by an out of range battery temperature, then no current will be provided to the battery even if Vbat<Vfloat, correct?
When float is triggered by a BMS using the WS500 input, I assume this results in a hard stop also?
Just to clarify, in hard stop situations does the WS500 shut the alternator down entirely, or does it switch to a zero current to the battery mode that will still support house loads?
Thanks again!
You are welcome. Breaking this down:
\"So in normal operation if LIMIT_FLOAT_AMPS=1, the alternator will provide a 1 Amp current to the battery so long as Vbat < Vfloat?\"
Yes, you are correct. At that moment amperage is the controlling factor
\"If Vbat is > Vfloat, then the alternator will no provide current to the battery regardless of the float Amp setting?\"
And yes again, this is correct. And now that VBat is > VFloat, it becomes the controlling factor. Alternator output will reduce until Vbat lowers below the target.
\"However if float was triggered by an out of range battery temperature, then no current will be provided to the battery even if Vbat<Vfloat, correct?\"
Out of range battery temperatures does not force the battery to change stages - ala, go into float. It will only however cause the output to scale back while in the Reduce-Capacity temperature ranges, and eventually cut off charging if temperature exceeds the hard limits. If we are in the RDC range (say 35c to 40c), even if in BULK phase, the WS500 can reduce output to limit battery current to the RDC Amps value - but the regulator will still remain in BULK mode and if the temperature returns to normal will resume charging without the RDC current restrictions.
\"When float is triggered by a BMS using the WS500 input, I assume this results in a hard stop also?\"
FEATURE_IN or CAN communications from a BMS to force into float will only place the regulator into float. If however battery temperature is ALSO out of range, the same overriding actions as noted above will happen - even if the BMS is calling for float, if the battery is over the fault temp, the reg will hard-fault.
\"Just to clarify, in hard stop situations does the WS500 shut the alternator down entirely, or does it switch to a zero current to the battery mode that will still support house loads?\"
Any hard fault will cause the WS500 to stop all alternator output and flash out an error code while changing the LED to RED. Hard faults can only be recovered from by cycling the power on the IGNITION wire. The reason for this is: Hard Faults should really never occur, they are an indication of some issue with the overall system design and installation - as such, the WS500 stops all activity with the hope the user will look to correct whatever caused that issue in the 1st place.
-al-
\"Out of range battery temperatures does not force the battery to change stages - ala, go into float.\"
Okay, thank you for clarifying this, it\'s a bit confusing as the manual states:
BAT_MIN_CHARGE_TEMP; // If Battery is below this temp (in deg-c), stop charging and force into Float Mode to
protect it from under-temperature damage.
BAT_MAX_CHARGE_TEMP; // If Battery exceeds this temp (in deg-c), stop charging and force into Float Mode to
protect it from over-temperature damage.
Well,
This is a bit embarrassing... I just verified in the source and indeed when the max/min temperature limits are reached, the WS500 does force into float mode! There is also a hard fault, it is triggered by battery temp exceeding 60c
So, I would say sorry for the miss-direction, and that you questions have been great as perhaps the WS500 should do better! Here is what I am thinking:
MIN_ / MAX_CHARGE should cut the drive to 0%, but leave the charge mode unchanged.
Hard fault should be based on MAX_CHARGE vs. fixed limit of 60c. Maybe hard fault should be 120% of MAX_CHARGE_TEMP (Example, if MAX_CHARGE_TEMP isset to 40c, at 40c and above set field drive to 0%, then if battery continued to raise do a hard fault at 48c)
We are preparing a new firmware release for this winter, and it seems the handing of the temperature limits could be improved...
Thoughts?
-al-
Having BAT_MIN_/BAT_MAX_CHARGE_TEMP cut the field drive to 0% would probably be the safest option. A more convenient option would be zero current to the battery while still supporting house loads, but I suppose the WS500 doesn\'t have any way of knowing where the shunt is installed, so this could result in the battery being charged at unsafe temperatures....
Having your high temp hard fault depend on BAT_MAX_CHARGE_TEMP vs a static 60c seems like a good idea, especially since a few people are starting to experiment with LTO (Lithium Titanate Oxide) batteries which can supposedly operate in a range of -50c to +65c for charge and discharge!
Would you also hard fault for cold temperatures? % of BAT_MIN_CHARGE_TEMP won\'t really work for that unless you switch to Kelvin:)
I\'m imagining the cold battery in morning scenario, you probably wouldn\'t want to hard fault (unless it\'s at like -40C or something) as it would be annoying to have the cycle the ignition once the battery temp rises above the hard fault level...
Cold hard stop: Ya, plus there are some batteries with heaters in them that we support, allows very cold operations! Plus, batteries getting too cold are not commonly a result of the alternator driving them!
I think it is better to stop all field drive when hitting temperature limits vs. 0A. There is a flag in the WS500 config where you can EXPLICITLY state the shunt is at the battery, but even so: Is a bit unclear if presenting some voltage to a hot battery has undesired impact - even if current is 0A.
Thank for the feedback!
-al-
\"I think it is better to stop all field drive when hitting temperature limits vs. 0A.\"
Yeah, seems like a safer approach. I suppose a BMS \"no charge\" relay triggering the WS500 input could also be indicating a similar problem (cell temp too high or cell voltage too high), but in this case the WS500 will go to float, not zero field drive. However, most of the time the BMS \"no charge\" condition simply means the battery is full and it would be preferable to continue supporting house loads in float.
\"Thanks for the feedback!\"
No problem! Thank you for all the information. I\'m looking forward to getting to the point in our project when I can purchase a WS500 and start using it. The WS500 appears to offer far more control and configurability than any other regulator I have researched.
Glad could help. And yes, the Ws500 does have a lot of capability - most of the time we have an answer for problems folks are having. And on the rare occasions when we don\'t, we can look to include a new feature in the firmware. Recall, all Ws500 regulators feature field up-gradable firmware!
-al-
Just following up on this discussion, has the addition of low temp/high temp field limiting been implemented in a new firmware release?
I assume of course that this will be a configurable control via the WS500 input. We are working with multiple Li battery banks and need to ensure low temp/high temp disconnect. However we also need to sequence the banks that are being charged and need to shutdown the alternator while making the transition from one bank to another which I expect to be able to do with the same input.
After spending a little more time thinking before posting I believe the best way to handle the bank switching and associated alternator shutdown is to simply control the ignition lead to the WS500 allowing for a shutdown delay (for bank switching) in our control logic.
The balance of my earlier post regarding firmware changes incorporating temp field shutdown is still valid.
We are targeting v2.2.0 firmware to be released some time in Feb, likely mid Feb. Am in the final phases of testing now. It will have the changes talked about above:
-- Min/Max bat temp limits will Disable the regulator vs. forcing to float.
-- Max Bat Temp Fault is 120% of the upper limit vs. hard coded at 60c.
This is great, always nice to work with manufacturers who actually incorporate suggestions from users and are responsive to their questions !
Do you see any potential issues with using the ignition lead to accomplish the alternator shutdown required while battery bank switching ?
That should work well. Make sure to give a 2 second of more notice (ala, de-powering the Ignition lead) before actually switching batteries. Alternators take upwards of 3-400mS to full \'wind down\' once the Field drive is removed to prevent a voltage spike when the battery is disconnected (What SAE defines as a Load Dump event). 2 seconds makes sure all is nice and safe.
Of course when resuming you will have the engine Warmup Delay again as the regulator powers on. If that is a concern you might consider reducing the Warmup Delay to its min of 15 seconds.
Thanks for the feedback we use this logic with our existing MC614 based systems and cannot wait to get the WS500 in place. The control of alternator output as one reaches defined alternator temp limits is perhaps one of the greatest features we are looking forward to using. The current regulator does a hard 50% drop in output and in some cases this results in a max output/50% output control cycle which is by no means acceptable.
