dumbass
100 kW
Hence a problem with commercially available BMS then isn't it.......
Bob
Bob
BMS-Free, info for the curious on bypassing the BM-mess
- Thread starter thedarlington
- Start date
Tommy L
100 kW
dumbass said:
I've done 850watt load tests on Headway 8ah Red cells in a 4S2p 16ah (4.5C discharge)
0 seconds no load 3.44v per cell 13.70v pack
1 second in 850w 3.12v per cell 12.51 pack
1 minute in 850w 3.04v per cell 12.20 pack
2 minutes in 850w 3.05v per cell 12.21 pack
3 " " " " "
4 " " " " " "
5 " " " " " " "
6minutes in 850w 3.05v per cell 12.21 pack
7minutes in 850w 3.04c per cell 12.16 pack
8 minutes in 850w 3.03 per cell 12.12 pack
9 minutes in 850w 3.02 per cell 12.08 pack
10minutes in 850w 3.00 per cell 12.00 pack
11minutes in 850w 2.96 per cell 11.77 pack
12 minutes in 850w 2.80 per cell 11.20 pack
72amp start and 78amp finish
69F start and 98F finish
0.17KW pulled in 12 minutes
You can see that the last 2 minutes (11 and 12 minutes) it's dropping fast!
If you did the discharge to only 80% you would stop at the 10 minute mark at 3.00v per cell
Tommy L sends....
dumbass
100 kW
Tommy L said:dumbass said:
I've done 850watt load tests on Headway 8ah Red cells in a 4S2p 16ah (4.5C discharge)
You can see that the last 2 minutes (11 and 12 minutes) it's dropping fast!
If you did the discharge to only 80% you would stop at the 10 minute mark at 3.00v per cell
Tommy L sends....
Tommy....Thanks for the data. Based on your testing I feel comfortable with my 2.7v LV alarm setting. Not to mention that I do not consider TS or GBS cells to be in the same class as Headway Red cells. As I've memtioned I only use an alarm not a cutoff. So I can turn off the alarm and continue riding if I feel lucky.
Bob
agniusm
1 MW
dnmun said:
There are some around, here is another one: http://www.bmsbattery.com/16-smart
this is the one i will use on my cargo bike
Tommy L
100 kW
dumbass said:
Hi Bob!
Are the GBS a better LiFePO4 then my Red Headway? If so by....
Density
Price
Quality
Longevity
Curious ... Thank you!
Tommy L sends... \\m//
999zip999
100 TW
I not going to BOIL my battery to get 1.5ah as to prove that I can get 20ah out of an A123 cell. I think I will live with a 18ah cell and have it live. If you what to run your battery to 2v. good luck with your pack. This is a thread of how to run a pack without a BMS. Battery murder system. Best wishes. With 3.8v to 2.0v for a A123 cell. Please report back with your pack after 2years.
dumbass
100 kW
Hey Tommy,
This is a hard question for me to answer because I've never had any HeadWay cells of any kind. I have 2 each ThunderSky and GBS.. 24v 20ah packs. I run them as ether 24v 20ah packs or jump 2 together for a 48v 20ah. I've been running the TS for 3+ years and have never had a cell problem. I've had the GBS packs for about 18 months but they have never been mounted on a bike. I bought them for my wife's bike for when her lead died. But it never did and she's happy with the lead. So I am going to use them on a new build this winter.
I buy the GBS cells as a 4 pack for $124 for the 4 (12v 20ah). They are prismatic cells with connection studs same as HW cells. They are oly rated at 3c. With my TS cells I draw less then 2c with them. One of the things I don't like about TS or GBS cells is they are rated at 2.8v to 3.6v. I charge to 3.65 and have my alarm set for 2.7v.
Just based on all the cell ratings I would say HeadWay cell are a better cell. In fact I have considered putting together a 48v 20ah Headwa pack or maybe use the 15ah cells to build a 48v 30ah pack. But I already have the GBS cells so I don't think it will happen.
Bob
This is a hard question for me to answer because I've never had any HeadWay cells of any kind. I have 2 each ThunderSky and GBS.. 24v 20ah packs. I run them as ether 24v 20ah packs or jump 2 together for a 48v 20ah. I've been running the TS for 3+ years and have never had a cell problem. I've had the GBS packs for about 18 months but they have never been mounted on a bike. I bought them for my wife's bike for when her lead died. But it never did and she's happy with the lead. So I am going to use them on a new build this winter.
I buy the GBS cells as a 4 pack for $124 for the 4 (12v 20ah). They are prismatic cells with connection studs same as HW cells. They are oly rated at 3c. With my TS cells I draw less then 2c with them. One of the things I don't like about TS or GBS cells is they are rated at 2.8v to 3.6v. I charge to 3.65 and have my alarm set for 2.7v.
Just based on all the cell ratings I would say HeadWay cell are a better cell. In fact I have considered putting together a 48v 20ah Headwa pack or maybe use the 15ah cells to build a 48v 30ah pack. But I already have the GBS cells so I don't think it will happen.
Bob
Tommy L
100 kW
dumbass said:
The 15ah cells (I've got some of the 16ah that are not normal production) are very sweet!
They seem to be the SIZE favorite if going for the Headway.
If you pull 4C from a 1P pack, 60amps is doable.
If you build a pack of 2P, 60amps all day long without much heat build up.
Sizing sizing sizing...... I dislike some of the responses on this forum of members trying to make certain battery chemistry do things outside
of it's physical capability, then call it crap.
Look at specs. Take specs for what they are worth. Then...... Test products yourself and see where it's sweet spot is and use it there
I believe for longevity for a battery or cells, Parallel them up! Share some load! If you need 60amps, find something that can do it
it's normal working range then......double it up. I'm sure this will make for a happy pack
By passing the BMS is not for everyone. I in fact enjoy it.....but it comes with responsibility. Not sure I like the BMS LVC at 2.1v for a LiFePO4 pack when I
know that my headway is at 80% DOD once it reaches 3.0v under a heavy load of 4.5C. After that, the battery does start to drop quickly, but only after
2 more minutes of use (in that given discharge test). IMHO, why stress the Battery Pack/Cells like that? I'm sure there are BMS with settable LVC,
"but I think I'll try the buzzer for $1.99 Jack" (a Jokers Wild TV show statement! lol)
Tommy L sends.... \\m//
dnmun
1 PW
but you miss the purpose for having LVC. it is not there to allow you to run the pack to exhaustion, it is there to prevent the accidental over discharge of the pack which happens when the pack is left attached to the motor with the controller on and people go off and leave it unattended. that is what the LVC is for, to protect the pack from the owner.
the HVC is there to prevent over charging as the cells age or get damaged from overdischarging, and go outa balance.
like i said at the beginning the thread is for those who don't understand how a BMS works and instead just wanna call it a 'battery murdering system' because they think it is cute to say.
a BMS does not prevent you from using the pack within a narrow operating envelope, it just protects the pack from mistakes and accidentally leaving it connected to the load and also from overcharging.
the HVC is there to prevent over charging as the cells age or get damaged from overdischarging, and go outa balance.
like i said at the beginning the thread is for those who don't understand how a BMS works and instead just wanna call it a 'battery murdering system' because they think it is cute to say.
a BMS does not prevent you from using the pack within a narrow operating envelope, it just protects the pack from mistakes and accidentally leaving it connected to the load and also from overcharging.
Tommy L
100 kW
dnmun said:
Fair enough dnmun!
But some people do not know how much energy to use from a pack (Maybe no CA or other) and run it to the LVC.
Taking a LiFePO4 down to 2.1v slowly might not damage it, but when people are using the LVC as a "dont use the ebike anymore and start pedaling"
then I believe this to be 100-110% DOD. Probably not good to do on a continued basis. But some do, then complain about out of balance, no range...
blah blah blah.....etc..
I've made the mistake of no BMS and left it plugged into the controller for a month and killed a pack. A BMS could have saved it from such a deep discharge.
I lost 2 out of 40 cells on that. Could have been worse and now I have to keep a close eye on the other 38 even more now! lol
My view on the "BMS Free" is to understand Batteries and or Cells. Watch them under different conditions of use. I enjoy to know my stuff.
Others out there could care less, plug it in, drive it. There are many car drivers out there that know the car has a "GO" pedal and a "Stop" pedal and where
to put fuel and follow GPS directions down a narrow alley. Just saying! lol
Tommy L sends....
dumbass
100 kW
dnmun said:
I agree a BMS has values and your example of leaving the controller attached is one of them. However, I don't remember anyone saying or even implying a BMS was a "battery killer". The comments of some are simply pointing out that there are alteritives and they ( I ) are sharing some of these alteritives. You keep insisting that many commentators don't understand a BMS just because we choose not to use one. Rest assured that just because some of us choose not to use a BMS is not an indication we do not understand how it work or it's purpose. It's simply our choice.
Bob
Tommy L
100 kW
dumbass said:
Hi Bob!
Concise and nicely written!
Tommy L sends....\\m//
dnmun
1 PW
dumbass said:
"I not going to BOIL my battery to get 1.5ah as to prove that I can get 20ah out of an A123 cell. I think I will live with a 18ah cell and have it live. If you what to run your battery to 2v. good luck with your pack. This is a thread of how to run a pack without a BMS. Battery murder system. Best wishes. With 3.8v to 2.0v for a A123 cell. Please report back with your pack after 2years."
etriker
100 kW
dnmun said:
It depends on the make.
The best way to know is to find a data sheet for your cells.
Notice where the A123 cells fall off the cliff.
http://www.batteryspace.com/prod-specs/6610.pdf
They are done at about 2.5v ?
I use these for my A123 packs for lvc alarm.
They are easy to hear. Loud.
http://www.hobbyking.com/hobbyking/store/__18588__Hobbyking_2_8S_Cell_Checker_with_Low_Voltage_Alarm.html
It is easy to set the alarm voltage to 2.7v.
For charging hvc I use this hooked to an old dell.
http://www.hyperion-world.com/products/product/HP-EOS1420iNET3/
It gives a lot of feedback on the condition of the cells when charging, charges fast and gets the cells in balance.
I also use a watt's up meter like a fuel gauge on the car.
http://www.amazon.com/Watts-Meter-Analyzer-WU100-Version/dp/B001B6N2WK/ref=sr_1_1?ie=UTF8&qid=1345815721&sr=8-1&keywords=watt%27s+up+meter
I don't want a bms that can cut the bike off in the middle of a big intersection with a pickup truck 4 feet right behind me.
I would rather have a loud beeper go off and then I decide what to do next. Time to pedal.
Tommy L
100 kW
etriker said:dnmun said:
It depends on the make.
The best way to know is to find a data sheet for your cells.
Notice where the A123 cells fall off the cliff.
http://www.batteryspace.com/prod-specs/6610.pdf
They are done at about 2.5v ?
I use these for my A123 packs for lvc alarm.
They are easy to hear. Loud.
http://www.hobbyking.com/hobbyking/store/__18588__Hobbyking_2_8S_Cell_Checker_with_Low_Voltage_Alarm.html
It is easy to set the alarm voltage to 2.7v.
For charging hvc I use this hooked to an old dell.
http://www.hyperion-world.com/products/product/HP-EOS1420iNET3/
It gives a lot of feedback on the condition of the cells when charging, charges fast and gets the cells in balance.
I also use a watt's up meter like a fuel gauge on the car.
http://www.amazon.com/Watts-Meter-Analyzer-WU100-Version/dp/B001B6N2WK/ref=sr_1_1?ie=UTF8&qid=1345815721&sr=8-1&keywords=watt%27s+up+meter
I don't want a bms that can cut the bike off in the middle of a big intersection with a pickup truck 4 feet right behind me.
I would rather have a loud beeper go off and then I decide what to do next. Time to pedal.
Nice! \\m//
CanadianWinters
100 W
Tommy L said:My view on the "BMS Free" is to understand Batteries and or Cells. Watch them under different conditions of use. I enjoy to know my stuff.
Others out there could care less, plug it in, drive it. There are many car drivers out there that know the car has a "GO" pedal and a "Stop" pedal and where
to put fuel and follow GPS directions down a narrow alley. Just saying! lol
Tommy L sends....
I totally agree with this.
BMS-free is not for everyone. You need to know what you are doing.
8)
arkmundi
10 MW
999zip999
100 TW
I think I have grown to have a personal relationship with my batteries as they can be fikkle or not. You can easy see the bad child. All said and done I'm going to do surgie on the 180 cell konion pack just for love. Maybe a 15s- 62v12ah pack bms free.
