24s BMS for LiPo Battery

[dnmun]

a pcm is the same as a BMS. you should not have to monitor the individual cell voltages if you have a BMS to protect the pack on discharge or during charging.

there is not much power left in the lipo below about 3.5-3.6V so assume all the Ah have been used up by 3.4V is reached. it will climb back up to 3.7V when you take the load off then.

do you have the D131 now or planning on ordering some? i may have one or two left if you wanna go that route but no idea if you are in the US.

 

[izeman]

it depends on how much time you want to spend on maintaining your battery. if you attach celllogs (4 pieces) to your paralleled packs and set the alarm to 4.2v and watch the charging process in person and stop manually as soon as a cell goes beyond hvc then you're fine.
i don't know what the risk would be if your controller cuts the motor during the start. if this is a risk you can't take, there is nothing else to do but add more capacity. if you over discharge those batteries they tend to puff, raise their internal resistance, and loose lifetime.

 

[pbrownhg]

"expecially" was a typo and not a spelling mistake...LOL! :lol:

 

[pbrownhg]

I am in Canada and would be interested in knowing how much you want for you D-131 board? I am also looking for a bulk charger for this system...I believe it is 100.8 V that I need???

As far as "cutting the motor at start", though I do not know, I understand the the BRUSA MD-35-605 is very good at controlling max current flow. It is easily set through a resistor, (www.kruspan.ch has more info for those that are interested.) I am hoping that this will be sufficient to never go above that set value.

 

[dnmun]

i would assume you would not wanna have the motor lose power on take off so i would not recommend it be used for protecting the motors from high current discharges. you need to design the battery and motor so you have ample excess capacity to handle any emergency.

the BMS is really to protect the pack from overcharging and overdischarging and short circuited output. it will allow you to use a high current bulk charger and still be able to balance the pack. i used 101V when i was forcing my first 24S lipo pack to balance, but after that i let it charge up to the 99.6V level. you may wanna charge it up to about 101V+ right before use but not keep it at high voltage between uses because the high voltage eats up cycle life.

 

[pbrownhg]

So to summarize.....

If during the testing phase on the ground I deem that, for example, 200 amp is the max draw (I should have never said "400 amp" this is only what the motor and controller are capable of in a burst) I need to get a decent takeoff, I will set my MD-35 with a resistor that will not allow more than that, ever. Then I use a bulk charger and the D-131 board to properly charge my batteries to a max of 4.2V, for use shortly there after. Then I make as big a 24s pack as I can (with the HK nanotech batteries) with available weight room (needs to be greater than 5s for 40amp/pack or less)
For a safe takeoff, there will not be any current limiting device on board the craft, except the controller limiting a ceiling of 200 amps to the motor. I monitor the cycle analyst closely during flight and the BMS monitors at every charge.

Is it agreed that this is a pretty good plan for my application?

 

[dnmun]

i would not recommend the nanotech packs. i had several puff up on me with no cause so i am not comfortable with using them.

but i have 21S 24Ah of 3P 8Ah nanotech in my battery. that is because mark poole gave me 8 of the 6S 8Ah nanotech packs last year so i used them and bot 3 more of the 5S to get to my 21S3P nanotech pack.

i don't know about the current limiter. never heard of them. your BMS will provide current limiting if that is what you need but i don't think you wanna have anything in there to stop the current even if it exceeds your expectations.

i'll go look for those two 24S lipo D131 BMSs i have somewhere here.

 

[IBScootn]

Regarding a BMS for lots of amps in a vehicle where safety is paramount, I would talk to the folks at http://evolveelectrics.com

They have lots of experience with the Orion BMS as well as the Elithion BMSs. These products should handle the # of cells and currents you're looking for.

 

[IBScootn]

Maybe take a look at this 24 cell BMS. Another guy is using it in his 160A motorcycle.
http://www.emsiso.com/Pages/emsiso/userfiles/files/BMS_datasheet.pdf
Best

 

[pbrownhg]

If not the Turningy NanoTech, then what is the general concensus on the best LiPo brand and technology in the 6S 5000 maH?

 

[dnmun]

others may not have the same problem with the nanotech puffing up. i put mine under some relatively small compression now and they seem to have lost the puff.

let others who have more experience with lipoly from HK offer up opinions.

 

[pbrownhg]

I am looking at an Elcon 8000W HF charger configured to charging Lithium-ion batteries. Please correct my logic....

At 24s5p LiPo, charging upto 4.2V/cell would be 100.8V. 8000/100.8V=79.36a. The D-131 BMS can handle 80a cont. That would be 16 amp/p and a charge rate of 3.2C.

Until someone suggests a better alternative, I was going to go with the middle of the road 35-70C, 6s, 5000 mah Turnigy Nanotech batteries . They are rated for an 8C charge rate. It would take approx. 19 min. to charge the pack.

Am I going to blow myself up or ruin my batteries?

 

[dnmun]

go with the 8Ah nanotech and build two identical packs side by side with one of the D131 on each pack. 25C discharge is more than i would imagine you could do more than a few dozen times if it goes to full discharge each time imo.

i should have included some of my 6AWGx8mm hole cable lugs for you to use to wire it up in parallel. i have the ebay link, but the 200A is gonna be hard on almost any connector besides a solid connection imo.

 

[izeman]

it's a general rule that slower charging to lower voltage and slower discharging to higher voltage prolongs cell live. how much is being heavily discussed.
a) 100.8v is correct
b) 80a charging is correct
c) 3.2c is correct
from the datasheet you are fine. but is it really necessary to charge in 19min? i found 1c charging a good compromise. i think flight precheck and stuff takes some time, and going from storage charge (3.85v/cell) to full charge should take 30min with 1c charging.
200a connectors? i wouldn't do that. the road to go is a solid copper bar and screw down ring connections.

 

[pbrownhg]

Is the Anderson SB-350 not upto the job? I will take the 1C advise and resize my charger. If you buy a more powerful charger, does the BMS have an adjustment to control rate of charge if the BMS was just used to charge and not discharge?

I have not fully committed to which way I will set up my system. If I put the BMS on the discharge side, I am concerned that there will be a device that could decrease power at a time when power is needed. I want to be the brain behind when I need power and not a device telling me in my emergency "you are not getting power". The goal is to have as direct a line between controller and motor as possible with reasonable safety measures in place.

 

[dnmun]

you can bypass the BMS on discharge. use it for charging only. i am sure that BMS will handle 50A of charging current but try to keep to 1C imo.

 

[izeman]

...I want to be the brain behind when I need power and not a device telling me in my emergency "you are not getting power". The goal is to have as direct a line between controller and motor as possible with reasonable safety measures in place.

there are not many cases where i vote against a bms, but this may be the one case. if your life depends on it and you don't have enough money, or just don't want to spend that extra money on really tested high professional $$$ equipment i would just check the battery with every charge, manually balance if needed, and add that little more capacity so you won't drain the battery too low. you have a really easy to calculate use case. your raise/take off always takes more or less the same time and therefore the same Ah, so it's easy to calculate/plan and add 30% more for safety. it's not like our ebikes where you "just hop on for a ride" and then find out that you rode those extra miles and now have a strong head wind driving back, which totally discharges your battery. this is a scenario that you can safeguard with a bms.

 

[izeman]

you can bypass the BMS on discharge. use it for charging only. i am sure that BMS will handle 50A of charging current but try to keep to 1C imo.

+1, and see my last post

 

[dnmun]

you cannot manually balance it to full voltage as a BMS does. you have to force the lowest cell to climb up to full charge in order to avoid having it be too low at the end of the discharge if you discharge with no BMS. that is why it has to charge to 101V. to make sure all the cells are at full charge. 4.20V.

 

[izeman]

you cannot manually balance it to full voltage as a BMS does. you have to force the lowest cell to climb up to full charge in order to avoid having it be too low at the end of the discharge if you discharge with no BMS. that is why it has to charge to 101V. to make sure all the cells are at full charge. 4.20V.

sure you can balance that battery. use a bc168 charger connected each one of the 4 6s balance plugs (one after the other). if you bulk charge to let's say 90-95% soc and then top balance with this charger you'll be fine and perfectly balanced. the bc168 balances ways better and more accurately than the d131. even if the bc168 "knows" nothing about the other 18 cells in the pack it's still more accurate by a factor of 25. 1mv (claimed) accuracy against 25mv+/- of the d131.

 

[fechter]

Another way around the discharge current limitation is to bypass the discharge section of the BMS completely and just use a large fuse or circuit breaker between the pack and controller to protect against over current.
Then, you can use a small simple interface circuit that monitors the BMS output and stops the throttle or key switch input to the controller if a single cell goes too low. The crudest way is to use a small relay powered by the BMS such that when the BMS trips, the relay turns off, killing the throttle.

In this mode, you may be able to use a 15A rated BMS at 150A or 400A. Again, you still need some kind of fuse or circuit breaker to protect against over current or shorts.

 

[pbrownhg]

What is the skinny on the Anderson SB-350 as a connector for my 101V and 200-250 amp current draw?

Is this Bussman fuse the best option for me?

http://electricmotorsport.com/ev-parts/fuses-holders-2/anl-style-fuses/ann300-cnn300-very-fast-acting-limiter-fuse-300-amp.html

 

[dnmun]

Another way around the discharge current limitation is to bypass the discharge section of the BMS completely and just use a large fuse or circuit breaker between the pack and controller to protect against over current.
Then, you can use a small simple interface circuit that monitors the BMS output and stops the throttle or key switch input to the controller if a single cell goes too low. The crudest way is to use a small relay powered by the BMS such that when the BMS trips, the relay turns off, killing the throttle.

In this mode, you may be able to use a 15A rated BMS at 150A or 400A. Again, you still need some kind of fuse or circuit breaker to protect against over current or shorts.

and if you don't wanna have engine failure even if you smoke the pack then you can use an indicator LED which is grounded through the P- lead, like richard talks about for a relay here, and when the BMS shuts off for LVC it would turn off your LED 'ready', or active, signal.

so you would have the go/no go signal in your face and could decide how to manage the situation then.

 

[fechter]

What is the skinny on the Anderson SB-350 as a connector for my 101V and 200-250 amp current draw?

Is this Bussman fuse the best option for me?

http://electricmotorsport.com/ev-parts/fuses-holders-2/anl-style-fuses/ann300-cnn300-very-fast-acting-limiter-fuse-300-amp.html

I think the Andersons are OK.
The fuse is rated for 80v. Might be OK at 100v, but some risk of arcing over (bad). You might check the stuff for large solar systems.

 

[pbrownhg]

In my investigations, an Italian contact has brought to my attention that he is using Lithium-Ion batteries from a Chinese source with good success. The batteries are 32aH cells with a 10C cont. rating. the cells are 820 grams each and cost $32 USD each. For my 24 cell configuration that is only $768.00 USD. This sounds like an amazing deal. Can anyone throw words of caution?