Battery preheating circuit

[Jonndeka]

Hi friends,

I googled about battery preheating method for EVs and most of the paper was the different types of preheating methods and I didn't find a suitable and applicable method for EVs.

I know these methods are classified by two directions: internal preheating and external preheating.
What is your suggestion? Just PTC resistive heating element is enough for heating? How can I calculate the value of the PTC resistor or how much current the battery needs to became heat?

Could you please share your experience?

 

[Comrade]

Can you describe your expected battery usage use cases? With emphasis on temperatures.

 

[Jonndeka]

Can you describe your expected battery usage use cases? With emphasis on temperatures.

Assume I want to develop a BMS for EV. One of these functions should be preheating of battery at subzero temperature for charging.
I would like to know which method/circuit should I implement for this?

 

[From-A-To-B]

Not an expert on this topic, but I’ve never seen a hobby-level BMS (think: JBD, Daly, etc) that easily and effectively integrates a heating circuit. I have seen some JBD manuals indicate that some of their BMS’s have ports to accommodate a heating element, but have never seen anyone here utilize that function. An affordable Bluetooth BMS with this feature would be wonderful.

Not the circuit-building advice you asked for, but maybe this is relevant fodder for this thread:

Of the EV modules I’ve handled, some apply heat/cooling to the big metal boxes that encase and compress prismatic modules. I’ve seen 75AH Ford modules (Batt Hookup had them for awhile) that had coolant plates in between pouch cells to more effectively cool / heat the cells.

Some people have posted previously about cooling / heating through the tabs of pouch cells, but it seems like heating the big faces of pouch cells or prismatic cells is more effective. (I’m summarizing from memory, here.)

For my simple applications, I’d love a BMS that could trigger a relay to power a small resistive heating pad, brining the module up to temp before charge. For me, it’s be acceptable to power this feature from the pack voltage, bonus points to run the warming from the charger power prior to charging the battery.

 

[Jonndeka]

Not an expert on this topic, but I’ve never seen a hobby-level BMS (think: JBD, Daly, etc) that easily and effectively integrates a heating circuit. I have seen some JBD manuals indicate that some of their BMS’s have ports to accommodate a heating element, but have never seen anyone here utilize that function. An affordable Bluetooth BMS with this feature would be wonderful.

Not the circuit-building advice you asked for, but maybe this is relevant fodder for this thread:

Of the EV modules I’ve handled, some apply heat/cooling to the big metal boxes that encase and compress prismatic modules. I’ve seen 75AH Ford modules (Batt Hookup had them for awhile) that had coolant plates in between pouch cells to more effectively cool / heat the cells.

Some people have posted previously about cooling / heating through the tabs of pouch cells, but it seems like heating the big faces of pouch cells or prismatic cells is more effective. (I’m summarizing from memory, here.)

For my simple applications, I’d love a BMS that could trigger a relay to power a small resistive heating pad, brining the module up to temp before charge. For me, it’s be acceptable to power this feature from the pack voltage, bonus points to run the warming from the charger power prior to charging the battery.

Thanks for the information.
Do I need a circuit for heating using a relay to power a small resistive heating pad?
Could you please refer me to a reference or document?
Thanks!

 

[From-A-To-B]

As an electronic lay person, I cannot answer any specific questions. But it would seem to be that, given the need to handle more than a few watts of heating, yes, you’d need a relay.

I’ve considered wiring up a manual version of this on my own larger batteries — a push-button, triggering a relay, to power a small heating pad— so I can more easily charge large packs during the winter.

But I haven’t implemented that, and it doesn’t add anything of interest in your quest to have a BMS manage this process.

It occurs to me that if you seek to develop a product and need advise on circuits, you might considering hiring an electrical engineer or someone with such a skill set.

Keep us updated!