BMS grades / types / categories

[podolefsky]

A Level 11 popcorn button ?

Let me think about the charge shuttling vs shunting category. While the implementation & cost are very different between the two, the end goal is the same: to top-balance the cells. The levels are categorized based on overall goal and not so much implementation.

Great thread! This will be really useful.

A charge shuttling system can balance the cells at any point during the discharge cycle, not just to top balance during charging.

You might break up level 2 into subcategories like 2.1) what you have, 2.2) also does temperature, 2.3) actually includes temperature in the SOC calculation, etc.

[Nuts & Volts]

Hmm technically this would be a Level 0, since it isn't a BMS at all, it's just a means of balance charging the pack, but it excibits behavior your would expect of a Level 2 BMS.

A level 2 charger?

Level 0 being a charger without the option to cutoff at HVW
Level 1 being one that can be shut off either via charger logic or a HVW
Level 2 being one that balances and regulates voltages accoirding to charge state just like an RC balance charger.

An RC charger actually has two settings. In regular charge mode it seems (this is what it looks like) that is simply charges and monitors the cells, stopping at HVC of one cell. It tries to charge to HVC of the pack but is stopped if cells are out of balance. Then you have balance charge mode which I am not sure how it works sorry. My guess is it pulls current from a few cells charges back up and then pulls more current until all cells are balanced.

[chef]

Thanks Skeez and Coninsan for the additional BMS links.

So, where does the balancing charger fit in with this BMS scenario? Let's say, for the sake of argument, a balancing charger on LiPo with a cell monitoring (Level 0?) system?

Integrating the BMS & charger is the next logical step. This enables the BMS to precisely control the charging and reduces the risk of a communication failure between separate BMS and charger units. From the descriptions of the RC balancing chargers, they have taps to each battery terminal required for top balancing. The balancing charger alone isn't a complete BMS, but as part of a greater system it is a vital component. The RC units handle HVC & top balancing while other circuitry takes care of LVC. In the future there will likely be more integration with large format cell chargers & BMS's, eventually encompassing all the functions of a BMS as we now know it. Volumes will have to ramp up first to make this viable.

[chef]

A charge shuttling system can balance the cells at any point during the discharge cycle, not just to top balance during charging.

You might break up level 2 into subcategories like 2.1) what you have, 2.2) also does temperature, 2.3) actually includes temperature in the SOC calculation, etc.

That's probably a good idea though I'm hesitant to make hard delineations for sub-features. That's because there may be BMS's that mix & match features (for instance 2.4 & 2.2 but not 2.3). There's already some blurring of the lines between L1 & L2. Maybe it would be clearer if I bulletized the features under each level?

Thanks for the clarification on charge shuttling. I'll update the post.

[podolefsky]

Thanks Skeez and Coninsan for the additional BMS links.


Integrating the BMS & charger is the next logical step. This enables the BMS to precisely control the charging and reduces the risk of a communication failure between separate BMS and charger units. From the descriptions of the RC balancing chargers, they have taps to each battery terminal required for top balancing. The balancing charger alone isn't a complete BMS, but as part of a greater system it is a vital component. The RC units handle HVC & top balancing while other circuitry takes care of LVC. In the future there will likely be more integration with large format cell chargers & BMS's, eventually encompassing all the functions of a BMS as we now know it. Volumes will have to ramp up first to make this viable.

Elite Power Solutioons system has communication between BMS and charger. I guess this makes the charger part of BMS, so technically it has communication between the cell monitoring part of the BMS and the charging part.

[podolefsky]

That's probably a good idea though I'm hesitant to make hard delineations for sub-features. That's because there may be BMS's that mix & match features (for instance 2.4 & 2.2 but not 2.3). There's already some blurring of the lines between L1 & L2. Maybe it would be clearer if I bulletized the features under each level?

Thanks for the clarification on charge shuttling. I'll update the post.

I agree, don't want to make it too complicated. I like the simple levels 0-3. Maybe then have a list of possible features and each system can have a check if it has that feature.

[frodus]

like this:
http://liionbms.com/php/bms_options.php

[podolefsky]

like this:
http://liionbms.com/php/bms_options.php

Yeah, something like that. I was thinking like this:

BMS_____________Elithion____EPS__ etc...

HVC________________x________x__
LVC________________x________x__
Balancing____________x________x_
Charger Ingration_____ ________x_
etc...
etc...
(we just keep adding features to the list here)

[chef]

The Elithion folks did a nice job assembling that list. We could probably reference that and be done with it unless you guys want to continue updating this one.
On the flip side, they use some peculiar terminology that doesn't flow well IMHO.

[frodus]

let me know and I can give the feedback to Davide.....