[Caevlist] Designing BMS low power sensing circut

Thu Sep 18 20:46:37 PDT 2014

 FEVT ltd used latching contactors from Albright.

http://www.albrightinternational.com/files/downloads/catalogues/SW80%20ETC%20TELECOM%20LEAFLET.pdf

You need to add a latching circuit when operating with low level BMS
systems. When BMS keeps the contactor ON/pulled there is very little energy
consumed. A simple trigger which is powered by few supercaps creates OFF
burst when the signal from BMS is lost. Contactor controller can be
programmed to sniff standard I/O's.

We did the previously mentioned to cancel the current drawn from several
contactors in a battery system. We used separate unit with PIC18F2480 SW/HW
watchdogs. The distributed design allowed cross supervision over several
CPUs with some redundancy. This topology allowed us to make systems which
worked 10 years with next to none service (some SW updates were made to add
redundancy). Winston's (aka TS) LFP-350AHA cells worked just as well that
10 years.

By default there is build-in hand shake protocol over CAN bus between the
main CPU and contactor controller. So if the CPU's SW (called Core SW) for
some reason loses it's mind next controller CPU takes over the system
control and initiates the preprogrammed CPU reboot sequence. Depending on
the setup user does no even know there was a reboot done. So adding this to
low level BMS you can achieve more stable and robust system.

One neat feature was a timer code which basically allowed CORE to determine
how many seconds the system may be on what ever is happening. Temperatures
or voltages are not going haywire in few minutes. Say some of the
electronics go broken. A divine touch or what ever is the reason. Contactor
controller allows to operate the system over the set timer according the
parameters. Naturally this controller may sniff all components on the CAN
bus to determine if the timer was set right.

I could make a patch of these contactor controllers if needed. I sold the
company away in 2010 but I still know the technology inside out.  Company
wen't belly up over a year ago so I dare to use the system design now (?)

I must say I'm stunned how long term technology investors did not know
Moore's law. :) There was a lot of critics how expensive touch screens and
multiple CPUs are and they will never be mainstream in vehicles. User
interface development was scrapped because: "no one will use touch screens
in cars. They distract the driver and are going to be forbidden by law".  :D

-Jukka

http://www.google.com/profiles/jarviju#about

2014-09-17 7:26 GMT+03:00 Adrian DeLeon via EV <ev at lists.evdl.org>:

> OK, it sounds like Steve is having a "phantom" current issue - the phantom
> being a contactor that is always on.
>
> Are these packs plugged into the AC mains while sitting unused? I had a
> similar issue with the 12V auxiliary battery in my EV. After about 4 days,
> the 12V battery would go dead from the small but constant currents drawn by
> the motor controller and mini-BMS board. I solved the problem with one of
> these:
>
> http://batterytender.com/products/motorcycle/waterproof-800-usa-western-
> hemisphere.html
>
> It's an 800mA trickle charger used to keep the batteries in ATVs and
> snowmobiles from going dead while in storage. It's a smart charger,
> weatherproof, isolated, and runs from 120/240 VAC. It came with both
> alligator clips and a set of ring terminals. Mine is wired to the charging
> plug of my EV, so as long as I'm plugged in, my 12V battery stays fully
> charged.
>
> After retiring one of my EVs, I put the trickle charger to use on a 7AHr
> gel battery that runs an automatic chicken coop door. The battery stays
> charged and the door will still operate for days during a power outage.
>
> If keeping your packs connected to AC power while in storage isn't
> possible AND this is a "run" contactor, you could wire the contactor coil
> through a connector adjacent to the main pack connector. When connecting a
> pack there would be the big connector (main pack) and the small connector
> (a small shorting plug that would activate the contactor coil).
>
> If this is a charging contactor, find a way to power it via AC mains. That
> way when the pack gets disconnected from the mains, the contactor will turn
> off at the same time.
>
> -Adrian
>
>
> On 09/16/2014 07:24 PM, Mike Nickerson via EV wrote:
>
>> I have a Mini BMS system also.  I suspect the contractor might be for
>> charging circuitry.  I have the same issues with an SSR in my system.
>>
>> The Mini BMS is set up to terminate charging if necessary when a cell is
>> over voltage and the ignition system is off.  It does this by turning off
>> the SSR or contactor on the AC line to the charger when it detects a cell
>> alert with the ignition off.
>>
>> When you turn on the ignition system, it re-arms the contactor back to
>> on, to prepare for the next charge cycle.  The problem is that the
>> contactor stays on all the time the vehicle is parked.  On my car, it takes
>> about 2 weeks to drain the auxiliary battery.
>>
>> I solve this by pulling the fuse to the EV control circuits which
>> includes power to the SSR.  I've wondered if there is a better way too.
>>
>> Mike
>>
>>
>> On September 16, 2014 7:02:41 PM MDT, Lee Hart via EV <ev at lists.evdl.org>
>> wrote:
>>
>>> Steve Clunn via EV wrote:
>>>
>>>> I am working on some Golf Carts and portable 12V power packs that get
>>>>
>>> used
>>>
>>>> sporadically and may sit for months without use.
>>>>
>>>> I have contactor on one 12V and 36V that draws about 1 amp.  The
>>>>
>>> problem
>>>
>>>> is, if everything is happy, the Mini BMS Circuit keeps the contactor
>>>>
>>> ON.
>>>
>>>> Which draws enough current, that at some point, will drain the
>>>>
>>> battery down.
>>>
>>>> I am trying to come up with a way that the owner can walk away from
>>>>
>>> this
>>>
>>>> system, and come back to it and have it ready to go without having to
>>>> switch switches OFF and ON.
>>>>
>>> Steve, could you elaborate a bit more on exactly what you need to do?
>>> My
>>> impression is that you have a 36v pack, with a contactor to connect it
>>> to its load. You don't want to have an on/off key switch; just hop in
>>> and drive. But that would mean keeping the contactor on all the time,
>>> which would run the pack dead?
>>>
>>> The best I can think of is something like a seat switch. When no one is
>>>
>>> sitting on it, the switch opens and turns the contactor off, which
>>> removes all loads from the batteries. When someone sits on the seat, it
>>>
>>> turns on the switch, which turns on the main contactor, and away you
>>> go.
>>>
>>> Another possibility is that Albright (and others) make latching
>>> contactors. There is a magnet as well as the solenoid coil. The magnet
>>> is sized to hold the contactor on (once it is already on), but not
>>> strong enough to pull it in (if it is already off). You then pulse the
>>> coil with a positive pulse of current to turn it on, or a negative
>>> pulse
>>> of current to turn it off. In both states, the continuous power
>>> consumption is zero.
>>>
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National Drive Electric Week 

Corvallis Event Description 

A good time will be had by all in Corvallis, Oregon on Saturday, September 20 th at its National Drive Electric Week (NDEW) Event. There will be an exhibit of several different brands of Electric Vehicles (EVs), including a Tesla that was just driven by its owner from Albuquerque. You will have an opportunity to ride in and drive an EV. This event will enable you to discuss EV features and operation with experienced owners, not dealers. A few owners, who are also engineers, will be there for those who want to discuss more technical aspects of EVs. This event is in conjunction with the famous Corvallis Farmers' Market. 
It will begin at 9:00 a.m. The main EV exhibit will be at the corner of NW Monroe Avenue and Second Street. When the Farmers' Market closes at 1:00 pm this exhibit will move to the Ride Terminal which also will open at 9:00 a.m. It is in the drive-up lanes at the Citizens Bank Main Branch on the northwest corner of SW Second Street and Jefferson Avenue. The Bank's address is 275 SW Third Street for those using a navigation system. Electric Vehicle rides and perhaps the opportunity to drive one will be between the hours of 9:00 a..m. And 1:00 p.m. Opportunities to drive an EV will definitely be given after 1:00 p.m. Reservations for those drives will taken at both event sites. 
The Corvallis NDEW event will showcase the wonderful features of Electric Vehicles (EVs). It will demonstrate their highly responsive drive systems and low centers of gravity, which make them fun to drive. That they have no tailpipe makes them friendly to our noses and health. Operated on hydro-, solar- or wind-power they are friendly to our climate. That electric vehicle motors make almost no noise makes EVs friendly to our ears. That their energy comes from low cost electricity, not expensive fuels, makes them friendly to our pocket books, as does the very small amount of maintenance that electric vehicles require. That their operation is simple makes EVs easy but still fun to drive. 
That only 5% of our daily trips are longer than 40 miles on average makes the Electric Vehicle an ideal second car for two-car families. A plug-in hybrid electric vehicle is ideal for single car owners. Range is not a problem for either kind of owner. Copies of a report on the advantages of driving electric will be available for visitors to take home as an informative memento of this event. 
So come to this wonderful event and experience the joy of driving electric. While here enjoy some locally-grown produce from the famous Corvallis Farmers' Market, while you learn more about vehicles that are fun to drive and offer so many other advantages. 

Ride/Drive Plan 

The Ride Terminal will be the canopy-covered, drive-up teller facility at the main branch of Citizens Bank. EV owners should enter one of its open lanes from Second Street and park under the canopy as near to the west end of that lane as practicable to await the arrival of riders. Thanks to the Citizens Bank the wait will be a comfortable one. Even though fully-charged at home, some EVs may need to recharge during this operation, if we do not have a sufficient number of vehicles participating. Kieffer Nissan's station may be the best choice for those who live far from the Ride Terminal. Its use will be cleared in advance with that dealership. 

Riders may begin to arrive at the Terminal as early as 9:15 on Saturday morning, September 20 and the last as late as 1:15 p.m. Please let me know what part of this period you will be able to cover, if not all of it. Two Leafs are coming from Lincoln City to help us out, but we are likely to need several more from Corvallis than have already volunteered. Please help us with this important function. Visitors to our EV Exhibit on the northeast corner of Monroe Avenue and Second Street will be given invitations to take EV rides. That invitation will provide them with the location of the Ride Terminal and the hours of operation. A few of us who are tending the exhibit site may offer ride/drives throughout the afternoon for visitors who want to drive an EV. 

It is suggested that owner/drivers describe their vehicle's main features and operational characteristics prior to departure from the Terminal and exhibit these during the drive. Refer to the NDEW website for tips on making the most out of this opportunity to encourage the ownership of Evs. 

The following route was checked out last Saturday to assure that it would work for our purpose. Presuming that there will be an insufficient number of EVs and a waiting line for rides, this plan limits the length of rides. It can be adjusted by owner/drivers as the supply/demand situation becomes clear. From the Ride Terminal drive south on Second Street to its dead end. Turn right on B Street, then left onto Fourth Street. Move to the right lane and exit onto Philomath Boulevard. Turn right onto 15 th Street and right on Western, then left on Third Street. Move to the right lane and turn right into the Citizen Bank parking lot. Drive through it to Second Street and re-enter the Ride Terminal. If there are a sufficient number of owners, those who want are encouraged to offer their passengers an opportunity to drive their EVs on a route, designated by those owners. 

This Ride Terminal will also serve as a satellite area to exhibit those EVs that could not be fitted into the main exhibit area. 

Please volunteer to participate as an owner/driver and send comments on this plan to eagerwj at centurylink.net or call Walt on (541) 753-5837. Thank you. 