lettersize
10 mW
- Joined
- Oct 26, 2015
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- 32
Bestechpower BMS
- Thread starter dnmun
- Start date
izeman
1 GW
you can calculate that by yourself, and then decide if it's good enough for YOU 
i have a very well balanced 20Ah pack here and can't complain. it works very well. but if your cells are completely out of balance, heavily abused, old or what ever you will under certain cirumstances not be able to balance it, even if you charge the whole night.
with a 141mA balance current you can discharge 100.000 mAh / 141 mA = 0,015% per hour. so assume one cell is completely discharged, and the other is full charged it make take weeks to complete.
please note that this does NOT show how the BMS works, it's just give you an idea of the numbers we're talking about.
i have a very well balanced 20Ah pack here and can't complain. it works very well. but if your cells are completely out of balance, heavily abused, old or what ever you will under certain cirumstances not be able to balance it, even if you charge the whole night.
with a 141mA balance current you can discharge 100.000 mAh / 141 mA = 0,015% per hour. so assume one cell is completely discharged, and the other is full charged it make take weeks to complete.
please note that this does NOT show how the BMS works, it's just give you an idea of the numbers we're talking about.
GmagNeato
100 W
Great news.. I got my BMS wired up and nothing went POOF! However, I'm not sure it's functioning correctly. One of the parallel strings in my 14s packs shows a voltage of 4.10, while the others are all at 4.17. When I plug the charger up, and read the voltage at the input of the BMS, I'm getting 59.3 or thereabouts. The voltage on the output is 58.2. So it appears that the BMS is not allowing any voltage through. I'm thinking this may be because the pack hasn't dropped below the maximum voltage threshold of the BMS, but am not sure. And shouldn't the BMS be slowly discharging the 4.17v parallel strings? They've held that exact voltage for over 24 hours now.
Should I connect to a load (still waiting for motor - any suggestions for load that can handle this voltage?) and discharge to say 3.8v or so and then charge it back up and see what happens?
However, I'm not sure it's functioning correctly. One of the parallel strings in my 14s packs shows a voltage of 4.10, while the others are all at 4.17. When I plug the charger up, and read the voltage at the input of the BMS, I'm getting 59.3 or thereabouts. The voltage on the output is 58.2. So it appears that the BMS is not allowing any voltage through. I'm thinking this may be because the pack hasn't dropped below the maximum voltage threshold of the BMS, but am not sure. And shouldn't the BMS be slowly discharging the 4.17v parallel strings? They've held that exact voltage for over 24 hours now.Should I connect to a load (still waiting for motor - any suggestions for load that can handle this voltage?) and discharge to say 3.8v or so and then charge it back up and see what happens?
Lurkin
100 kW
I have decided I would like to buy a Bestech BMS for the Q76R project I am making. As it is my first home built battery, I'm little lost with choosing the right BMS from Bestech as it seems there are many options.
All of my calculations are in the first post here: https://endless-sphere.com/forums/viewtopic.php?f=14&t=75415#p1138493
The plan is to use 48v (max charge 54.5v), max 35a discharge. From what I can work out, the following part numbers are all 35a max continuous discharge:
HCX-D163
HCX-D100
HCX-D107
HCX-D167
HCX-D268
I'm a little stuck because I don't know which attribute is considered important beyond that. I have also attached a summary I have made of the 13S Bestech BMS if that helps. Can anyone help me choose the right one of these five BMS?
All of my calculations are in the first post here: https://endless-sphere.com/forums/viewtopic.php?f=14&t=75415#p1138493
The plan is to use 48v (max charge 54.5v), max 35a discharge. From what I can work out, the following part numbers are all 35a max continuous discharge:
HCX-D163
HCX-D100
HCX-D107
HCX-D167
HCX-D268
I'm a little stuck because I don't know which attribute is considered important beyond that. I have also attached a summary I have made of the 13S Bestech BMS if that helps. Can anyone help me choose the right one of these five BMS?
markz
100 TW
If I remember correctly, Bestech Power requires a MOQ of 2, depending on what you get, I could go in with you.
tomjasz
1 GW
overrated for 36 and 48v packs.
Lurkin
100 kW
I'm not following you Tom, this is new to me and I kinda need you to spell it out.
DAND214
10 MW
Overrated in what way? I know if you can get the HVC lowered it would be better, the LVC is fine. I think I have the HCX-D167 and it appears to work fine. 44vand the LVC is fine but HVC is 1/4 volt higher bthan what we do.Lurkin said:
So if you can get lowered it would be better for the cells,
Dan
DAND214
10 MW
OH HO?
tomjasz
1 GW
There are lots of inexpensive, reasonably priced BMS, that aren't Besttech and will serve the needs of average users at half the price or less. I bought the same BMS used in thousands of packs by OEM builders, for $10-$20.Lurkin said:
Lurkin
100 kW
DAND214 said:
This is exactly why I used the calc to overcalculate capacity, so I can reduce the operating voltage range to maximise cell life/ compensate for cell degradation.
Lurkin
100 kW
tomjasz said:
Happy to hear your alternative suggestions Tom, welcome to put them here: https://endless-sphere.com/forums/viewtopic.php?f=14&t=75415
I guess being a safety feature it would be strange to me to buy a range BMS off ebay etc as I don't have the knowledge of how to detect a good BMS from a bad one. Hence coming to this thread where this brand has been tried and tested, even if it is a more expensive option (anyone know the prices as they are not on the website?). With the amount I've spent on the bike already it seems like the wrong area to try and save money.
tomjasz
1 GW
Sorry, I derive some income from having found a reputable supplier. Some good leads in the ultimate weld thread. The AU fellow that shared with me insisted I not share. But you might get with Ballarat Bikes for a source there. I'm behind you in knowledge, but I'm happy and so is everyone I sold to.
Lurkin
100 kW
I understand - I'll probably stick with Bestech this time round, I have another battery to put together in the future that will be less critical and I'll look to do something cheaper with that.
Anyone keen to comment on which of the five Bestech BMS I should go for?
Anyone keen to comment on which of the five Bestech BMS I should go for?
9lives
10 W
Lurkin, I'd give the d132 a go. 30 amp max continuos and looks similar to the d131 I have run with nil issues. My guess is they will ask for about $70us plus postage ($28 approx) for a sample. Henry at bestech was who I dealt with and he sorted order quickly.
tomjasz
1 GW
When Beseech specs say "adjustable" does that mean factory set?
http://www.bestechpower.com/518v14spcmbmspcbforli-ionli-polymerbatterypack/PCB-D132.html
http://www.bestechpower.com/518v14spcmbmspcbforli-ionli-polymerbatterypack/PCB-D132.html
izeman
1 GW
Yes. They set it to predefined values.
tomjasz
1 GW
So set to a specific cells performance it's basically rendered either useless of less than ideal if recycled into a new pack with different cells?izeman said:
izeman
1 GW
Sorry. I don't understand your question. The values they choose, and which are given by the resistor network, works very well for lipo and li-ion. There are some discussions about ideal values, so there it's maybe more a personal preference than a technical limitation.
Lurkin
100 kW
9lives said:
48 x 30 = 1440w. I need a max of around 1500 watts, ideally a bit more, which is why I was going for 35a continuous? Damn it, BMS are sticky! :lol:
The current rating of the BMS should really be chosen based on the discharge rating of your batteries. The idea is you want the BMS to trip before the batteries can overheat or be damaged. The motor controller has its own current limiter. It's usually good if the BMS has a significantly higher rating than the controller to avoid nuisance trips.
Lurkin
100 kW
I'm yet to finalise the cell choice, but it will likely be LG INR18650MJ1 3500mAh or Sanyo NCR18650GA 3.6V 3500 mAh both of which have a maximum discharge current of 10A. The pack is to be 13S either 14P or 15P depending on how things fit when I actually receive the frame and can make cardboard models of the battery sizing. Therefore 14P x 10A = 140a maximum continuous discharge or 150a maximum continuous discharge.
Having said that, I would like to be able to separate the pack in half and use half on another bike at the same time. (i.e. physically remove half, put it on another bike for my partner and we ride together to the farmers market or the moon!).
In this case 1/2 x 140a = 70a maximum continuous discharge which is about double what we need 8) I think we will be ok with 35a maximum continuous discharge 8)
But it does bring me to a second question - I can remove 1/2 the pack in this way... whats the best method - treat them as two sepearte packs in parallel with a BMS each? is it ok to use BMS in this way?
Having said that, I would like to be able to separate the pack in half and use half on another bike at the same time. (i.e. physically remove half, put it on another bike for my partner and we ride together to the farmers market or the moon!).
In this case 1/2 x 140a = 70a maximum continuous discharge which is about double what we need 8) I think we will be ok with 35a maximum continuous discharge 8)
But it does bring me to a second question - I can remove 1/2 the pack in this way... whats the best method - treat them as two sepearte packs in parallel with a BMS each? is it ok to use BMS in this way?
Connecting the two packs to each other requires they are at the same voltage when the connection is made or there is the possibility of destructively high current as one pack tries to charge the other one. If you have a way to ensure the voltages are close enough, it can be done but would be prone to 'accidents'.
The safest approach is to use the two packs independently and switch from one pack to the other when using two. This would require two BMS units. I have something like this on my bike. There is a 3 position switch that selects one pack or the other and one off position. The switch activates a hefty relay.
The safest approach is to use the two packs independently and switch from one pack to the other when using two. This would require two BMS units. I have something like this on my bike. There is a 3 position switch that selects one pack or the other and one off position. The switch activates a hefty relay.
tomjasz
1 GW
When I was looking for a 3 position switch most responses were clueless. We did it anyway and it worked out great. Best solution in my opinion
Would you share which switch you used?
Lurking, here's a BMS guy I used on eBay. He's been extremely responsive and answers email questions very quickly. Not sure about what it'll be like over the holiday. 100% rating.
http://www.ebay.com/sch/zhan-lingj/m.html?_nkw=&_armrs=1&_from=&_ipg=50&_trksid=p3692
we added a voltmeter to the assembly and make a bracket from junk plastic parts.
Would you share which switch you used?
Lurking, here's a BMS guy I used on eBay. He's been extremely responsive and answers email questions very quickly. Not sure about what it'll be like over the holiday. 100% rating.
http://www.ebay.com/sch/zhan-lingj/m.html?_nkw=&_armrs=1&_from=&_ipg=50&_trksid=p3692
we added a voltmeter to the assembly and make a bracket from junk plastic parts.
Attachments
tomjasz
1 GW
Here's the switch we used.
http://www.amazon.com/Eaton-Military-Termination-On-Off-On-Contacts/dp/B005T6B7GQ
http://www.amazon.com/Eaton-Military-Termination-On-Off-On-Contacts/dp/B005T6B7GQ
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