Hi everyone, I'm looking for details about the new (?) BMS being supplied with the Headway packs. I'm still considering Gary's circuit and am looking for some sort of comparison of the benefits and drawbacks between each design. If anyone has any detailed information on the functionality of the Headway BMS that would be excellent. I need one for my 12 cell pack. Thanks!
Headway BMS?
- Thread starter oofnik
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flashedarling
100 mW
- Joined
- Jul 21, 2008
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- 49
I have pretty much the same question. I'm building a 24s6p pack and I don't have a clear idea of what I'm going to for BMS or charger. I am not sure how much fun i would be to make and test 6 of Gary's BMS units. Or how much better that woul be than just ordering either a BMS or complete pack from Headway. I'd love it if someone could help out here.
GGoodrum
1 MW
flashedarling said:
Atually, all you need is one BMS board, not six. You just need to wire all the cell junctions together, so that you end up with 24 groups of 6 paralleled cells.
-- Gary
dnmun
1 PW
kurt's 36V headway BMS looked well built, 2.5V for the LVC. remember that the crucial difference between gary's design and the stock headway design is the higher LVC and the lack of output fets in the open source BMS gary developed. you can decide whether you will push your cells to the maximum discharge or not, having fets in the battery cable just introduces power loss and the possibility that the BMS will leave you dead if there is a failure on the board or when the LVC cuts in and turns the BMS off totally. at least the open source design allows you to cripple it home with minimal current as the brake line keeps kicking in. it looks like a little skill challenge if you are not used to soldering up pcb boards, but not impossible, but like with lotsa hobby stuff, doing it yourself is not always cheaper either. i doubt if headway would reduce their LVC since they have to warrantee the battery, and the only way they can shut it down is to use the output fets. you can buy a BMS from mr ping too.
headway got a false rap from someone on one of the threads (was it dmitri?) who implied they had problems when it was actually another BMS and he didn't realize that. you can look at the discharge graph that dr bass did and from that you can estimate how much power is left in the headway pack when the LVC is at 2.5V versus 2.1V, and think about your situation and expected needs for the battery to make the best decision. buying the entire pack already built with a BMS is easiest, and cheapest too. plus i think they do better work than i could. wish i had money for one of their packs myself so i'm biased.
headway got a false rap from someone on one of the threads (was it dmitri?) who implied they had problems when it was actually another BMS and he didn't realize that. you can look at the discharge graph that dr bass did and from that you can estimate how much power is left in the headway pack when the LVC is at 2.5V versus 2.1V, and think about your situation and expected needs for the battery to make the best decision. buying the entire pack already built with a BMS is easiest, and cheapest too. plus i think they do better work than i could. wish i had money for one of their packs myself so i'm biased.
I'm considering only using the BMS as a charging balancer. If I use the Headway BMS I'll bypass the FETs and wire in some sort of indicator signal when the LVC trips or something like that. But if I'm going to go through with all that maybe I might as well just build the Fechter / Goodrum BMS (have we standardized a name for that board yet? 
). I've also got my own independent cell LVC design still standing.
Currently I'm using an R/C balance charger. I wire the cells up in 6s2p for charging since the charger can only do 6s at a time. This makes my wiring harness quite complicated, not to mention the sllloooowwww balancing. I think I need something that will protect the cells during discharge that's a step above the simple voltage cutoff on my Castle controller.
So it's either a Headway BMS, my LVC circuit, the open BMS... oh, decisions.
). I've also got my own independent cell LVC design still standing. Currently I'm using an R/C balance charger. I wire the cells up in 6s2p for charging since the charger can only do 6s at a time. This makes my wiring harness quite complicated, not to mention the sllloooowwww balancing. I think I need something that will protect the cells during discharge that's a step above the simple voltage cutoff on my Castle controller.
So it's either a Headway BMS, my LVC circuit, the open BMS... oh, decisions.
flashedarling
100 mW
- Joined
- Jul 21, 2008
- Messages
- 49
I've got every part of my motorcycle planned now. Ordered the motor, lined up instrumentation and controls, even ordered a mini-mill so I could make some aluminum brackets. I am just stuck on this BMS thing.
I'm not a huge fan of tedious work but I do like the extra control the Open BMS gives me. I don't like how if I order a complete headway pack and a cell goes bad I would have to send the whole pack back, I'd much rather just find the bad cell. On the other hand is the headway BMS the only way to get a warrantee, and how long is that warantee.
On the other hand, what if I want to reconfigure my pack later.
This is really eating at me. Of course I've got time before the weather is warm enough to actually ride the bike once done but I'm starting to order everything now and this is the last stumbling block.
IN ADDITION: You say that the current limit control on the headway also drains the pack slightly. Can you give any indication how much? Is that only when the pack is running or when it is unplugged as well?
I'm not a huge fan of tedious work but I do like the extra control the Open BMS gives me. I don't like how if I order a complete headway pack and a cell goes bad I would have to send the whole pack back, I'd much rather just find the bad cell. On the other hand is the headway BMS the only way to get a warrantee, and how long is that warantee.
On the other hand, what if I want to reconfigure my pack later.
This is really eating at me. Of course I've got time before the weather is warm enough to actually ride the bike once done but I'm starting to order everything now and this is the last stumbling block.
IN ADDITION: You say that the current limit control on the headway also drains the pack slightly. Can you give any indication how much? Is that only when the pack is running or when it is unplugged as well?
voicecoils
1 MW
@ flashedarling
I can suggest you contact John @ http://www.stealthelectricbikes.com.au (E-S member GetADirtBike) he has experience with large Headway packs.
Secondly if you choose to go with Headway complete pack + bms + charger, I'd suggest you specify that you want the pack made with screw type cells and constructed like this:
That way, if any single cell failure may occur then it should be possible to remove the affected cell for replacement.
I can say that I'm very happy to have my two 36v10Ah blue cell headway packs. I haven't been able to test maximum continuous discharge or LVC cut out but Kurt on E-S has a similar pack with no problems. Being sent a complete pack, ready to drop in makes life heaps easier!
As for current drain, over a 2 week period of no use my packs both went down less then 2v each left off the charger IIRC. I don't see it as a big issue as long as you use (or somehow cycle) the packs at least once a month or so.
Cheers!
I can suggest you contact John @ http://www.stealthelectricbikes.com.au (E-S member GetADirtBike) he has experience with large Headway packs.
Secondly if you choose to go with Headway complete pack + bms + charger, I'd suggest you specify that you want the pack made with screw type cells and constructed like this:
That way, if any single cell failure may occur then it should be possible to remove the affected cell for replacement.
I can say that I'm very happy to have my two 36v10Ah blue cell headway packs. I haven't been able to test maximum continuous discharge or LVC cut out but Kurt on E-S has a similar pack with no problems. Being sent a complete pack, ready to drop in makes life heaps easier!
As for current drain, over a 2 week period of no use my packs both went down less then 2v each left off the charger IIRC. I don't see it as a big issue as long as you use (or somehow cycle) the packs at least once a month or so.
Cheers!
dnmun
1 PW
i think all the 10Ah headway cells are the screw top version now. the blue sleeve almost seems to be a new formulation since the internal resistance is 8-9mohm from what dr bass found on his tests.
you could also buy a completed pack and take the BMS out and change the value of the LVC by changing the components in the comparator circuit to get down to 2.1V to extract the last 5% from the pack, when i looked at the output fets on kurt's BMS, they looked they would have a super low on resistance, but i bet you could still bypass the output fets, but then you would need to be able to shut off the controller using the brake line when any of the cells dropped to 2.1V which i think may happen now that people are starting to get these packs in the group buy next month
you could also buy a completed pack and take the BMS out and change the value of the LVC by changing the components in the comparator circuit to get down to 2.1V to extract the last 5% from the pack, when i looked at the output fets on kurt's BMS, they looked they would have a super low on resistance, but i bet you could still bypass the output fets, but then you would need to be able to shut off the controller using the brake line when any of the cells dropped to 2.1V which i think may happen now that people are starting to get these packs in the group buy next month
voicecoils
1 MW
dnmun said:
I believe you are incorrect, however best to ask Victoria directly for the exact answer.
My blue cells in my two 36v10Ah packs are tab welded. John @ http://www.stealthelectricbikes.com.au (E-S member getadirtbike) has a number of recent packs with new cells that are tab welded.
I've just received 8 screw type blue cells too.
My understanding is that the cells are all made the same (can shape) and then the screw caps are tab welded to the cell on either side. I could be wrong however.
dnmun
1 PW
that sounds right, so you could also buy replacement cells with the tab welded on and replace the bad cell by cutting it out with some scissors and then soldering a new one back onto the old tab. that would keep the soldering heat off the top of the cell too.
everybody wants the screw tops now, but what if the screw tops end up having problems holding the screw torque tight on the connector and wiggle free and cause intermittent resistance spikes to drive the LVC on the BMS awry. or maybe they end up getting unduly twisted because of the stiffer connection through the cap, i think all the group buy packs are screw tops.
everybody wants the screw tops now, but what if the screw tops end up having problems holding the screw torque tight on the connector and wiggle free and cause intermittent resistance spikes to drive the LVC on the BMS awry. or maybe they end up getting unduly twisted because of the stiffer connection through the cap, i think all the group buy packs are screw tops.
flashedarling
100 mW
- Joined
- Jul 21, 2008
- Messages
- 49
The screwtops having problems if too much stress on them is a concern, but I plan on keeping the load off of them in custom battery holders, other effects of wear and aging causing them to have resistance spikes is more a worry but I'm not certain.
Looking at the pictures of the packs Victoria posted in the other thread it looks like all cells are the new blue ones but are flat topped and are spot-welded to the aluminum connectors. I don't think they will be that easy to separate. I like the specs quoted to me on the Headway BMS but the desire to have more control is really what is holding me back. I included the specs Victoria sent me, the seem to be around what I need. Still.......
Also, sorry if I sound like a broken record, this is the last thing I have to decide before I start by build.
Looking at the pictures of the packs Victoria posted in the other thread it looks like all cells are the new blue ones but are flat topped and are spot-welded to the aluminum connectors. I don't think they will be that easy to separate. I like the specs quoted to me on the Headway BMS but the desire to have more control is really what is holding me back. I included the specs Victoria sent me, the seem to be around what I need. Still.......
Also, sorry if I sound like a broken record, this is the last thing I have to decide before I start by build.
The specs don't look too bad. 150ma balancing current should be OK as long as the cells stay healthy. 60 amp continuous discharge is pretty good too. Not sure how big a motor you want to run. The real test is, well, a real test. We need guinea pigs...
voicecoils
1 MW
I'll just reiterate most of what I said before.
I can understand being indecisive, I was too before making my purchase.
I would suggest trying to get decisive about the specs you require.
Pack Voltage
Pack energy storage (Ah or Wh's)
BMS discharge capabilities (continuous and maximum)
Once you've decided your requirements, try to find a solution that exceeds them. I would go with the most robust BMS you can get. Having some headroom for discharging current will be handy if you ever want more power
Unless you want a very high Ah pack the only two viable options I see are Headway 10Ah cells or PSI 10Ah cells (14Ah in the near future). For larger packs, search E-S for 'markcycle' and 'hipower'. He is using higher capacity prismatic hipower lifepo4 units and likes them.
Headway cells are about 1/2 the cost of PSI cells and can come with BMS, charger, and fully assembled. If you specify exactly what you want and the product delivered does not meet it, take advantage of the 1-yr warranty and return it.
If the highest performance is required then LiPo pouches or A123 cells should be options on the table, with maximum complexity and price compared with other options.
I can understand being indecisive, I was too before making my purchase.
I would suggest trying to get decisive about the specs you require.
Pack Voltage
Pack energy storage (Ah or Wh's)
BMS discharge capabilities (continuous and maximum)
Once you've decided your requirements, try to find a solution that exceeds them. I would go with the most robust BMS you can get. Having some headroom for discharging current will be handy if you ever want more power
Unless you want a very high Ah pack the only two viable options I see are Headway 10Ah cells or PSI 10Ah cells (14Ah in the near future). For larger packs, search E-S for 'markcycle' and 'hipower'. He is using higher capacity prismatic hipower lifepo4 units and likes them.
Headway cells are about 1/2 the cost of PSI cells and can come with BMS, charger, and fully assembled. If you specify exactly what you want and the product delivered does not meet it, take advantage of the 1-yr warranty and return it.
If the highest performance is required then LiPo pouches or A123 cells should be options on the table, with maximum complexity and price compared with other options.
Doctorbass
100 GW
flashedarling said:
I received these documentation too.. if i remember correctly they are at 100$ us each?
Doc
voicecoils
1 MW
flashedarling said:
blue ones can be bare for tab welding or screw topped (like the picture I showed earlier in the thread).
If you bought a reassembled screw type pack of 24s6p you should have at least 27.6kW cont, 30.6kW peak of power on tap staying within the specs and cutoff of the BMS.
Also if you were concerned about single cell failure, just buy a few extra loose cells. They're a minor cost in the greater scheme and then you have a drop in replacement close at hand if needed.
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