Problem with JBD BMS Heat function on

[J.P.]

I have several JBD BMS with the HEAT function that are not working... at least not in the way I need them to work.

I have discovered (by trial and error) that the heating function only works if the battery is connected to an active charger. The best I can tell, if it's connected to an active charger, when the BMS senses the temperature has reached your "Charge under temp Trigger Value" setting, it simultaneously turns off the Charging Port and connects the ground to the H- terminal which will turn on your heaters if you have them connected properly. Once the temperature reaches your "Charge under temp Release Value", it disconnects ground to the H- and turns on the Charging Port again.

The problem I am having is that I have some "Gate Operator", Automotive" and "Tractor" batteries connected to these BMS's and these batteries are connected to

Mroinge MBC022, 12V 2A Lead Acid & Lithium(LiFePO4) Automatic Trickle Battery Charger Smart Battery Maintainers​

and once the battery is full (which is 99% of the time), the maintainer goes to sleep and the BMS does not sense that it is connected to a charger and the heaters do not activate when the temp drops.

Has anyone figured out a way around this issue? I could just put a (not smart) trickle charger on these batteries and allow the BMS to turn off the charging when the battery is full but I wish there was a better way. Any Thoughts?

 

[timselectric]

I have several JBD BMS with the HEAT function that are not working... at least not in the way I need them to work.

I have discovered (by trial and error) that the heating function only works if the battery is connected to an active charger. The best I can tell, if it's connected to an active charger, when the BMS senses the temperature has reached your "Charge under temp Trigger Value" setting, it simultaneously turns off the Charging Port and connects the ground to the H- terminal which will turn on your heaters if you have them connected properly. Once the temperature reaches your "Charge under temp Release Value", it disconnects ground to the H- and turns on the Charging Port again.

The problem I am having is that I have some "Gate Operator", Automotive" and "Tractor" batteries connected to these BMS's and these batteries are connected to

Mroinge MBC022, 12V 2A Lead Acid & Lithium(LiFePO4) Automatic Trickle Battery Charger Smart Battery Maintainers​

and once the battery is full (which is 99% of the time), the maintainer goes to sleep and the BMS does not sense that it is connected to a charger and the heaters do not activate when the temp drops.

Has anyone figured out a way around this issue? I could just put a (not smart) trickle charger on these batteries and allow the BMS to turn off the charging when the battery is full but I wish there was a better way. Any Thoughts?

It's working properly as designed.
It shouldn't drain the battery, ever.

 

[J.P.]

It's working properly as designed.
It shouldn't drain the battery, ever.

You did not read the entire post. I understand that it is working as (poorly) designed. It does not work with a full battery hooked up to a smart charger that has gone into sleep mode. Any ideas how to make it work other than a non-smart trickle charger?

 

[SeaGal]

I just read the entire post twice. What is the issue? It sounds as though it does heat before charging?

 

[J.P.]

I just read the entire post twice. What is the issue? It sounds as though it does heat before charging?

OK. When the battery is full, and the smart charger is in sleep mode, and the temperature drops below the setpoint, the heaters will not kick on because the BMS does not sense that it's hooked up to a charger. The heat mode only works when it has charging current. It seems that it has to disconnect the charging port, BEFORE it will turn the heat on and it does not bother to disconnect the charging port unless it senses power to it.

 

[SeaGal]

But surely if the batteries got drained a bit, then the heater would kick in when charge current starts?

I have a JBD too, but without heater on a static 48V home system. I use the cell temp figures from the BMS UART port to turn on a grid-powered heater to keep the cells toasty all the time, but that wouldn't be a good solution for an off-grid situation.

 

[Wjm1964]

These bms heat functions will only work when they see a charge voltage and the other issue is if the charge circuit is off and the temperature drops the low temp side will also kick in and stop charging anyway. Ideally the bms should take or allow some voltage to go to heat pads only until temperature climbs and then allow charge to begin.

 

[J.P.]

I guess there is a lot of back story that would help define the issue and my goal. I am in South Central Texas so we do not have freezing temps all that often. I also have fabricated 12V batteries for my vehicles using Headway 38120HP Cells with custom 3D printed cases. The way I understood the HEAT function on the JBD BMS's to work, I thought if I had a charger hooked up to them they would kick on the heaters and KEEP the battery from freezing. I found out the hard way that it does not work that way, at least not with the smart charger I was using.

The issue came a few weeks ago when we had a cold snap that went into the teens and lasted for a few days below freezing. When I went to start my car, the battery was under 32F and it cut off the charging port and (even though I have a Balmar APM-12 installed) the electric in the car was surging and the Heater fan motor was cutting on and off and it threw some codes in the ECM so I cut the engine off and was unable to drive the car until the battery got above freezing.

I am trying to figure out a way to KEEP the batteries from freezing with this setup. My next attempt will be to use a 14V 2A Power supply (wall wart) connected to the batteries so they see a constant charging voltage and see it that works. I am just unsure of the long term ramifications of this if the battery sees constant 14V charging voltage at 2A. Will it hurt the battery? Will it burn out the power supply? Something else?

 

[SeaGal]

In that case, could you just wire up an independent grid-powered heater then, using an STC-1000 type thermostat?

 

[TacomaJoe]

I'm with SeaGal. My thinking is that having the 14V present won't work if the battery is charged. I suspect that the BMS senses a charging current to trigger the event. I was picturing a couple in parallel where one hits the low temp threshold first and starts pulling from the other battery.

 

[J.P.]

In that case, could you just wire up an independent grid-powered heater then, using an STC-1000 type thermostat?

In a previous battery of this type that I built for my Generac Standby Generator, I used a KSD Bimetal Thermostat (NO 5C) that has worked OK but I was hoping the new HEAT function on the BMS would work better.

 

[J.P.]

I'm with SeaGal. My thinking is that having the 14V present won't work if the battery is charged. I suspect that the BMS senses a charging current to trigger the event. I was picturing a couple in parallel where one hits the low temp threshold first and starts pulling from the other battery.

You are probably right. Once there is no current flow, there is noting for the BMS top sense. I will test it anyway. The best answer if for JBD to redesign that function and give us more control options in the App.

 

[timselectric]

Any ideas how to make it work other than a non-smart trickle charger?

Constant float charging.
Maybe.

 

[timselectric]

Ideally the bms should take or allow some voltage to go to heat pads only until temperature climbs and then allow charge to begin.

This is exactly how they work.

 

[timselectric]

This is how the heat function works on BMS's.
When the temperature hits the low temperature limit. It transfers the incoming power from charging to the heating pad.
When a charging source is available. It will heat the battery until it gets to its "allow to charge" temperature.
Once this temperature is reached. The BMS transfers the incoming power to charging the battery.

Note: the heating is only ever powered by the charging source. (Never from the battery)

 

[J.P.]

This is how the heat function works on BMS's.
When the temperature hits the low temperature limit. It transfers the incoming power from charging to the heating pad.
When a charging source is available. It will heat the battery until it gets to its "allow to charge" temperature.
Once this temperature is reached. The BMS transfers the incoming power to charging the battery.

Note: the heating is only ever powered by the charging source. (Never from the battery)

Yes, but if the battery is full, (even though a charging source is connected), there is no power flowing into the battery (because it's full) and therefore the heaters are not activated. Poor design in my opinion.

 

[timselectric]

Yes, but if the battery is full, (even though a charging source is connected), there is no power flowing into the battery (because it's full) and therefore the heaters are not activated. Poor design in my opinion.

If the charging source is available. And the BMS temperature sensor is at the heating setpoint. It should be heating.
Maybe the charger isn't large enough for the heating?

 

[J.P.]

If the charging source is available. And the BMS temperature sensor is at the heating setpoint. It should be heating.
Maybe the charger isn't large enough for the heating?

I only have a 20W heater in this battery. 20W @ 12V = 1.67A. The charger is 2 Amps. I have done several tests and the way it works is, if the battery is (less than full) and actively charging when the temp goes below the low set point, the BMS will shut off the charging port and redirect that power to the heaters and they will heat until the battery is above the release point and then the heaters will be turned off and the charging port reactivated.

The problem is when the battery is full, it does not do that. It seems that it is programmed to only turn off the charging port if it is actively charging and it will not turn on the heaters until it turns off the charging port... which does not happen if it is not actively taking a charge.

 

[timselectric]

I only have a 20W heater in this battery. 20W @ 12V = 1.67A. The charger is 2 Amps. I have done several tests and the way it works is, if the battery is (less than full) and actively charging when the temp goes below the low set point, the BMS will shut off the charging port and redirect that power to the heaters and they will heat until the battery is above the release point and then the heaters will be turned off and the charging port reactivated.

The problem is when the battery is full, it does not do that. It seems that it is programmed to only turn off the charging port if it is actively charging and it will not turn on the heaters until it turns off the charging port... which does not happen if it is not actively taking a charge.

Right
No need to warm the battery, unless it needs to be charged. It can be discharged at lower temperatures than it can be charged at.