ams introduces chip for simpler cell monitoring & balancing

[MitchJi]

Hi,

http://www.greencarcongress.com/2013/10/20131017-ams.html

ams introduces new chip for simpler distributed cell monitoring and balancing operations in Li-ion battery systems



ams AG, a provider of high-performance analog ICs and sensors, has introduced a simplified and more robust method of implementing cell monitoring and balancing in lithium battery systems. The innovative architecture developed by ams has been implemented in a new, highly integrated chip, the AS8506, to perform distributed cell monitoring and balancing operations for stacked cell modules, including Safe Operating Area (SOA) checks and passive or active cell balancing.

The new chip is suited for all lithium-based cell chemistries, such as those found in hybrid and fully electric vehicles, as well as for EDLCs (also known as supercaps or ultracaps).

In conventional systems, a complicated algorithm running remotely on a high-end microcontroller decides which cells have to be balanced. The new architecture supported by the AS8506 can control balancing locally at the cells, enabling designers to implement a more streamlined cell management system that eliminates the powerful host controller, complex software and vulnerable serial communication links normally used today.

The AS8506 can implement both passive and active cell balancing autonomously, or it can support a microcontroller-based system via its Serial Peripheral Interface.

An advanced analog circuit in the AS8506 compares up to seven cell voltages against an internal or external reference with an accuracy of 1mV, to support cell-balancing and cell-monitoring functions. Cell voltage measurements can also be digitized with an accuracy of 5mV and reported to a host controller.

Active and passive cell balancing use a similar circuit design, but active balancing requires an additional flyback transformer. The control circuit is integrated in the AS8506.

The device also features internally or external adjustable upper and lower cell voltage limits. Temperature measurement is carried out through two external NTC sensors.

The fully autonomous cell management architecture enabled by the AS8506 is in contrast to the typical system implementations found today using existing cell monitoring ICs. These are typically limited to the sequential capturing of cell voltage measurements that must be processed by a host controller. These prior architectures have several drawbacks for designers of battery management systems, according to ams:

The system must stream large amounts of data over a serial link—a communications channel that is vulnerable to interference in noisy environments.

A powerful host controller running complex software is required to turn individual cell voltage measurements into useful functions such cell balancing decisions. Writing this software is a difficult and time-consuming task. The software requires exhaustive testing in order to qualify for use in automotive ISO26262-compliant systems.

Sequential cell measurements require complex compensation algorithms in order to produce valid voltage and current readings across a stack of cells. By contrast, the simultaneous measurements captured by the AS8506 require no compensation.

The AS8506 marks a breakthrough in cell monitoring—not an incremental improvement on previous cell monitoring ICs, but a completely new approach. By offering local cell and temperature monitoring, the AS8506 gives system designers a simple and robust means to implement a battery management system, with just a simple microcontroller required for basic system functions.

—Manfred Brandl, Product Manager for battery management in the automotive business unit at ams

 

[powersupply]

So much bla bla for a 1 cell OZ 890 (multiplexed into 7 cells) plus a max 100 mA DC-DC flyback converter?
Such mouthful marketing language backed by a >$9 price (in 1K quantities)?

A 7s (32V) BMS!

By using only one cell to work with at any time they make their life easy.
But that 1:7 multiplexer also divides the actual duty time of any charge/discharge power by seven.
Plus probably some more dead time inbetween.
And cell 1 even less: with "..Cell1 maximum charging/discharging current is limited to 30mA.."

Each cell will be balanced with 14mA max (averaged)?
Except cell1 which is 4mA?

Did I get that right?

Doesn't even have LVC and HVC!

This cannot be!

Where am I wrong?

 

[circuit]

The AS8506 cell monitoring IC is available for sampling now. It is priced at $9.10 for 1,000 pieces. ams also provides a non-automotive version called the AS8506C. It is priced at $7.80 for 1,000 pieces.

Are they kidding with this? There are chips for $3-4 that do 16s!

 

[methods]

EDIT: Yes I realize this is a 4yo post... I am catching up :wink:


You guys are pretty quick to bash... I dont see a single thread on anyone trying it before talking trash.
It may be trash... but how about we actually TEST IT before flaming it... especially where there may be a conflict of interest as at least one member is selling a very similar product.

The chip looks like prospective stroke material to me... How many others are offering active balancing that brings up lower cells as well as passive balancing to bring down higher cells?

The demo board is priced very reasonably at a hundred bucks

100mA is a lot of balance current... On a scan I saw no mention of 14mA balance currents. I see that with active balancing the current is limited to 100mA thu the chip and dependent on the transformer selected.

edit - ok... 100mA/7 = 14ma... but that would be a non-case where all cells are balancing. Not a realistic case. In my experience one or two cells are a problem.

7 cells multiplexed is fine... how much power do you want to burn reading the cells every 10ms? It is not necessary - furthermore it is wasteful. Checking the cells every half second is fine. Most if not all LVC happens under dynamic load. Thats a dynamic LVC, not a static, so no need to respond so fast... in fact we usually add hysteresis to slow down the response! Nobody wants the BMS tripping when they smash the throttle from a dead stop and see a tiny blip of LVC. If it is a static LVC then little or no load is present so no rush eh?

For HVC... a half of a second is going to make no difference. Maybe a mV... even at 2C or 3C charging. What is far more important is the quiescent current of the BMS and how that affects shelf life.

If we are going to bash a product lets do it based on Testing, disappointment, and relevant facts.

Yes I agree its expensive - so is Linear
Yes the external components are probably very expensive
Yes it will probably have endless problems... just like LTC6802 did... and I was beta tester on that

A member tried to open the door to an opportunity. Dont slam it unless you want to put up the $100 for a demo board to show that it is in fact shit.

-methods

 

[methods]

Here is some useful information for anyone who wants to investigate:

The demo kit is on Mouser: http://www.mouser.com/new/ams/ams-as8506/
Parts on Octopart: https://octopart.com/search?q=AS8506
(Future has them for $8 bucks and they appear to still be in production)

Click on Development Tools
(Yes... the documentation is sparse on the demos)

Looks like they have a general purpose USB board that works with the configuration software.
I see a simple board, a passive board, and an active board.
Looks like they want people to test their stuff.

The data sheet is linked above. Its 94 pages... which is longer than any Maxim data sheet I have ever seen.

-methods