BMI cells

[Battboy]

I see, well he might be interested in the new packs that we are now developing for Motorcycles and high-end e-bikes. These are under design now and preliminary breadboard model testing at the moment. We will be launching them early 2009 as complete modular systems for these kind of guys. They will be standard equipment on several of the motorcycles that will be competing in the TTXGP race in the U.K. next year: http://www.ttxgp.com/

Best,

Don Harmon

 

[miro13car]

I presume I am the only one on this forum which uses HPS 10Ah 36V to power my bike.
HPS has quite easy life powering my bike - max ever drawn 48A.
Unfortunate I live in place in rather harsh winters.
In all my excitment about this pack I cannot forget that this pack quite detoriate in cold weather .
You can count me as a one who is going to take my pack apart and adopt to my bike, becuse lugagge rack is ment for lugage not for battery.
Because I didn't owned LiFePo before I simply don`t have comparison with other , but I suspect chemistry is chemistry and there are other cells out there, problem is there are not many 10Ah. Once I see serious offerings in 10Ah category for sure I will consider them as cells for my batt replacement for my 2 other elctric bikes - almost sure they will be cheaper than LifeBatt.
Agree, LifeBatt is the most expensive 36V 10 Ah pack on the market, do you agree also?
3Years warranty is just the symbol for DIY crowd, I took my pack apart already.
Problem is PSI/lifeBatt/BMI doesn't have much competition, that's why price is like this.
You need more to be allowed to usethat Phostec powder and prices would come down.
Exclusivity make that cells so expensive.
MC

 

[swbluto]

True, patents tend to cause increased price to upwards of the patent's life(usually around 23 years). But I think it's worth it if it stimulates the very same innovation that originally beget lifepo4.

 

[miro13car]

To claryfy this,
LifeBatt pack seems to be affected by cold by loosing capacity only.
It agree with Sandia Lab reports. About 0.8% loss for every 1C drop.
I don't see any difference in power delivery so far at minus 5C.
Bike easly reach 30km/h just like in summer.
But my trip is short -8km , battery doesnt't have a time to cool down really, I keep bike in my kitchen.
It depends how warm is your batt before start riding.
MC

 

[mcstar]

Just a random thought on temperature control for the LiFePO4 batteries. For those living in cold areas who are planning to convert a motorcycle or automobile, consider designing your airflow across the system so that cooling air can flow across the motor and then be directed into the battery spaces. This will allow the motor's heat to warm your batteries up and give them the same capacity in the winter as in the summer. I thought of this because one of the motor manufactures (either Perm or Agni) has a motor with a hose attached to it blowing cooling air over the rotor. I was thinking that if you put the entire motor in a shroud or box, then you could have the heated air directed into your battery space and use it to help maintain battery temperature. Perhaps you'd want to create vent valves of some time to allow the adjustment of more or less warm air as needed.

I've been tearing down a Honda insight battery pack and have been impressed by the great lengths they went to control the temperature environment in their battery packs. Perhaps thats one of the reasons they can get 200,000 miles out of their battery packs?

 

[miro13car]

mcstar,
do you use factory made BMI 48V pack or home made pack from BMI cells.
it is so hard to get in touch with anybody who owns BMI/LifeBatt HMS pack.
on electric Echo site there is no contact to the man who bought pack only to disributor.
mc

 

[mcstar]

mcstar,
do you use factory made BMI 48V pack or home made pack from BMI cells.
it is so hard to get in touch with anybody who owns BMI/LifeBatt HMS pack.
on electric Echo site there is no contact to the man who bought pack only to disributor.
mc

Yes, I bought a complete 48V pack from BMI. It has 4 BMS boards each monitoring 4 cells. I'm using a cheapo 2Amp charger howerver which seems to work well enough, it's just a bit slow. It keeps the pack balanced well. I've got about 100 cycles on it and still get well over 10Ah of capacity.

 

[fechter]

What does the BMS look like?

 

[miro13car]

mcstar,
from published pictures here and other web sites like CampaTracka.com /Australia,Armin Pauza/ it is clear, you pack is identical to my and no doubt uses the same boards called VMS, but they are identical electronics.
My questions are about how your BMS/VMS works. They don`t have any LVC and cells are simply connected in series with wires going from which cell to the boards.
Does your voltage LEDs on the top always turn off 1, 2 minutes after you disconnected pack from controller like manual says?
My LEDs /always only one of the clusters/ often stay for like 1 hour after disconnecting battery and resistors are warm,
does it mean cells are balanced after removing load?
Also I have other questions.
Can you , please comment on this?
MC

 

[mcstar]

They don`t have any LVC and cells are simply connected in series with wires going from which cell to the boards.

Yeah, this is correct, mine are directly connected to the VMS, however I've added a high voltage ciruit that controls my charger as described below.

Does your voltage LEDs on the top always turn off 1, 2 minutes after you disconnected pack from controller like manual says?

Yes, this is how they behave on mine. They come back on whenver I connect the charger or pull a load from them. They stay on while I'm pulling the load and turn off after a couple minutes of non-use. They are always on while charging and balancing. The top does get warm to the touch while balancing.

My LEDs /always only one of the clusters/ often stay for like 1 hour after disconnecting battery and resistors are warm

I did notice this on mine during the first couple weeks I owned it. I assumed it was balancing during this period. The problem was, that the charger did not disconnect automatically during this period to give the batteries the chance to balance (balancing current is only done at about 200ma). To correct this, I realized that I needed to be able to cycle he charger off and on until the balancer could even out the charge on the cells. To facilitate an overnight charge, I added a ping BMS board that I had in spare, in parallel with the BMI VMS and wired its over voltage circuit in-line with my charger. This has two effects. First, I get a much faster balancing period since the balancing current flows through both circuits. Second, each time over voltage is detected the charger is cut out for a few minutes, then it comes on again when the voltage settles down due to the balancing currents. This cycle repeated for several hours until the pack is well balanced. Now it only takes an hour or so of balancing after each use. I hope I'm being clear, do you understand what I mean? FYI, you could do something similar if you wired up a Mosfet curcuit to control the charger. You'd want the Mosfet to conduct while the OHV signal is low and turn off when the OHV signal is high. Use the Mosfet on the ground side of the charger's connection and you'd have basically the same setup I do without the extra balancing circuit.

I know that there is a new circuit board currently in developement at BMI that can be used to control a charger during balancing and also handle the LV condition. It's supposed to be ready in Jan or Feb if you want to wait for that. In the meantime, it's likely you're not getting a full 10AH from your pack. I was at about 7Ah before I setup the charger in this way. Now I get at least 10.5Ah per charge and I've gotten more than that before (when it was warmer outside).

 

[miro13car]

mcstar,
thank you , finally somebody with the same technology.
I see what you had added to your charger. Ping's BMS's overvoltage cycles off/on your charger. it is if you disconnected and again connected charger several times. But isn't processor going to register these as seperate charge cycles?
I don't know.
You know that VMS records over, under voltages and # of cycles like power tools batt packs do also, example Milwaukee.
We forgot to mention buzzer. How buzzer plays in all this.
According to manual short beeping buzzer plus OHV light means to terminate charging immediately.
I understand this short beeping plus OHV light means ONE only cell reached over some max volts , 3.6V perhaps?
I use LifeBatt charger is "damb" and out of synch with OHV light. Before orange LEDS turns to green/end of charge/ on charger buzzer and OHV on pack comes on , the time diff is maybe like 5-7minutes.
Buzzer/OHV comes on at 43.3V and if I ignore beeping and keep charging charger gets green LED at 43.5V.
Now, should I follow charger or battery.
IS my batt going to be undercharged if I turn when beeping starts. Good question.
I noticed one LED cluster will stay 1 hour on when I ignore beeping and keep on charging.
So I stopped that practice and disconnect charger 1 minute after I hear OHV beep.
What do you think?
Do you do the same thing.
I sure would cut load the moment I hear OLV beep for sure, but I never discharged so deep.
In summer right when I got my pack at 25C above zero I got more than 10Ah from it twice , once even 11Ah but it was NOT in Turbo mode /max. 10A, max 500W/ with many stops when pack recovered/rested.
I would not probably got 11Ah with like20A continous.
macstar, what your opinion about charging/OHV/OLV/buzzer and the way I snhould charge.
MC

 

[miro13car]

I forgot to add that after I opened my LifeBatt pack 24 hours after riding all cells were perfectly balanced all read precisely 3.33V , I was impressed indeed.
No doubt you get what you pay for.
I must add that days before that my bike tipped and pack slid down on the concrete not really hit but was dragged maybe 1 meter on the ground. So I wanted to check for damages - nothing- everything tight and solid inside.
Circuit boards profesionally assembled .
MC

 

[mcstar]

Ping's BMS's overvoltage cycles off/on your charger. it is if you disconnected and again connected charger several times. But isn't processor going to register these as seperate charge cycles?

From what I understand, and information here... http://www.electric-echo.com/lifepo4/lifepo4_bmi_docs.shtmlthe VMS only registers a "cycle" when the voltage goes above 3.65 and below 3.2V. So, this should not be a problem. However, I do not yet have a cable to connect it to my PC so I cannot verify this yet.

We forgot to mention buzzer. How buzzer plays in all this.
According to manual short beeping buzzer plus OHV light means to terminate charging immediately.
I understand this short beeping plus OHV light means ONE only cell reached over some max volts , 3.6V perhaps?

I use LifeBatt charger is "damb" and out of synch with OHV light. Before orange LEDS turns to green/end of charge/ on charger buzzer and OHV on pack comes on , the time diff is maybe like 5-7minutes.
Buzzer/OHV comes on at 43.3V and if I ignore beeping and keep charging charger gets green LED at 43.5V.

Please don't do that. The reason is that when the OHV/beeping starts, at least one of your cells is over the 4.0 or 4.2V setting. You need to disconnect the charger once it starts beeping (either manually or using a circuit) to let the VMS balance the pack. Balancing only takes place at 100ma so it may need some time to bring the higher cells back down. Once the OHV cuts off, you can continue charging (this is what the ping BMS does for me in my setup)

Now, should I follow charger or battery.

Always follow the VMS

IS my batt going to be undercharged if I turn when beeping starts. I noticed one LED cluster will stay 1 hour on when I ignore beeping and keep on charging.
So I stopped that practice and disconnect charger 1 minute after I hear OHV beep.
What do you think?

I'd remove it immediately to prevent over volting. An over charged cell's voltage climbs VERY quickly. It can raise a volt or more in about 10 seconds.

 

[mcstar]

What does the BMS look like?

The VMS is this one, but my pack has 4 of these wired up in series
http://www.electric-echo.com/lifepo4/lifepo4_bmi_vms.shtml

 

[rkosiorek]

mcstar,
thank you , finally somebody with the same technology.
I see what you had added to your charger. Ping's BMS's overvoltage cycles off/on your charger. it is if you disconnected and again connected charger several times. But isn't processor going to register these as seperate charge cycles?
<snip>

MC

Ypedal has the same VMS, BMS or whatever you want to call it. he bought it from PSI. i'm not sure if he is using it though with his home built packs. you can see it in his thread

http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=6028

rick

 

[miro13car]

" you need to disconnect the charger to allow VMS to balance.."
I thought balancing takes place well before charger is disconnected.
I understand shunt resistors get hot , because balancing is in progress.
According to description of Garry's /Bob Macree's BMS shunt resistors get hot during balancing, once cell reached max voltage shunt takes over overflow.
I think once cells get close to 4V /when you keep charging despite OHV buzzer shunt resistors try to dissipate extra energy.
They really get hot after buzzer sound.
I have question - recently one LED cluster never comes on after I connected charger , this cluster comes on but at the end of charging maybe after 15 minutes.

What do you think?

 

[fechter]

The VMS thing is almost bizzare. A buzzer? WTF? What about guys like me that can't hear?
Anyway, it does look interesting.

 

[swbluto]

Perhaps they have the haptic version of a buzzer for those who'd need it. You know... "Hand buzzers".

 

[michaelplogue]

Just take the buzzer leads and wire them to your saddle. That way, you'll get a nice little jolt in the jewels to let you know it's time to stop.....

 

[mcstar]

The VMS thing is almost bizzare. A buzzer? WTF? What about guys like me that can't hear?
Anyway, it does look interesting.

It's really just a speak, like the one on computer mother boards. The sound it makes is more like a squeak than a buzz. But there are also LEDs and two pins that go high whenever the setup is tripped. IOW, one goes high for overvoltage and the other goes high for undervoltage. These are 5V pins that can be used to drive other circuitry as needed. (like for that the haptic vibrator if needed

 

[docnjoj]

Haptic, paptic! I am offering 1/2 patent rights on a copper chain mail jock strap with 2 leads out. They will have allegator clips that will coinnect directly to the 2 speaker leads. Perhaps an amp can be installed for a serious warning! Could save vasectomy money!
otherJoc er Doc

 

[mcstar]

:lol: :lol: :lol: :lol:

 

[miro13car]

Well, buzzer is rather for bench testing?
HPS packs suppose to be automotive packs, who is going to hear from beneth of vehicle?
On bicycle IF I wanted, I wrote IF I wanted to fully discharge I would take chances, if I were in quiet place I could hear it .
When I ride farther I always check on LEDs, they are quite accurate.
mcstar, what do you think about my pravious questions?
MC

 

[mcstar]

" you need to disconnect the charger to allow VMS to balance.."
I thought balancing takes place well before charger is disconnected.

The problem is that each cell can only be balanced at 100ma. When a LiFePo4 cell is fully charged, it's terminal voltage rapidly increases. So, if you are charging a 2amps for instance, then the cells that are fully charged will have very high terminal voltages and the ones that are not quite fully charged, will have voltages below the fully charged voltage. The VMS will be attempting to shunt this current using the resistors, but can only do 100ma at a time. This is much less than your chargers current (most likely), so you need to cycle the charger to give the VMS time to discharge the high cells to prevent damaging them due to over voltage.

I understand shunt resistors get hot , because balancing is in progress.
According to description of Garry's /Bob Macree's BMS shunt resistors get hot during balancing, once cell reached max voltage shunt takes over overflow.
I think once cells get close to 4V /when you keep charging despite OHV buzzer shunt resistors try to dissipate extra energy.
They really get hot after buzzer sound.

They won't be able to dissipate any full charge current over 100ma, so they are probably over heating if you allow the charger to continue while the buzzer sounds. For sure the terminal voltage of the full cells will be too high at this point. I wouldn't risk the damage to them.

I have question - recently one LED cluster never comes on after I connected charger , this cluster comes on but at the end of charging maybe after 15 minutes.

I've never seen this happen, I'll pass it on to others that use these BMS to see if they've seen before and can give some ideas.

 

[fechter]

Haptic, paptic! I am offering 1/2 patent rights on a copper chain mail jock strap with 2 leads out. They will have allegator clips that will coinnect directly to the 2 speaker leads. Perhaps an amp can be installed for a serious warning! Could save vasectomy money!
otherJoc er Doc

Don't get the polarity reversed on that or else it may cause the throttle to increase instead of decrease...

It sounds like the VMS could allow the cell voltage to go higher than the safe limit.
I never understood systems that took the cells over their desired charging voltage then used the shunt to bleed them back down to the proper level.