Yesa

[fechter]

Can someone please explain to me what happens to the BMS when the packs are in series?

Why is it affected? It doesn't make sense to me.


I can understand problems with charging if the charges are earthed, but not in use when there's no common earth.

Everything will work fine unless the BMS detects an overcurrent condition and opens. When the BMS overcurrent FET opens, but the one on the other pack stays closed, the full voltage of both packs will be across the FET, which will be double the voltage it's designed for. Poof.

Ypedal was having the BMS overcurrent trip while accelerating, and that is a likely scenerio in many systems. It's also very likely that one BMS will trip at a slightly different point than the other one.

The BMS really needs to be designed for the total voltage.

One other way around this limitation is to bypass the current limiter part of the BMS and rely on the controller to limit the current during discharge. You would still want the BMS to be active during charging.

 

[powerdog69]

I've been told by Crystalyte that they use LiCoxNiyMnzO2. does anyone have any info on this type of Battery?

 

[TylerDurden]

I've been told by Crystalyte that they use LiCoxNiyMnzO2. does anyone have any info on this type of Battery?

search "emoli"

 

[Ypedal]

LiCo=Lithium cobalt
LiMn=Lithium Manganese ( emoli)

From wich clyte dealer was this ?

 

[efreak]

Hi,
I have considered ordering my pack from sam at yesa, at this point I am gonna try to assemble the bike. in a couple of months make the final decision on the batteries since the riding season is comin to an end pretty soon. but it seems to be good batteries you van order the cells and assemble your own pack.

http://www.alibaba.com/company/10935478.html
some company info

efreak

 

[powerdog69]

I contacted Crystalyte and asked them what type of lithium they sell.
Does any one have any specs on emoli are they any good?

 

[xyster]

I contacted Crystalyte and asked them what type of lithium they sell.
Does any one have any specs on emoli are they any good?

Do a search here for "emoli" or "LiMn" or "manganese" -- there's plenty of material. Yes, emoli's, along with A123 LiFePO4 cells, are for now the best cells money can buy for ebikes. Each has comparative advantages and disadvantages.

As for the "LiCoxNiyMnzO2" batteries: the electrodes in lithium batteries sometimes employ a mix of metals. In that case the battery, Lithium Cobalt Nickel Manganese Dioxide, would probably have specs in between lithium cobalt and lithium manganese.

 

[powerdog69]

cheers will do some reading

 

[efreak]

congrats!!

thanks for the pics eagerly awiting some data from the pack

efreak

 

[Johnbear]

My friend has this pack it seems to work great. We measured the capacity on a watt's up on a real life ride. Over 10AH max current was 39 amps, no cut outs. We will see what time will tell. He bought it from ebay fro Yesa. Sam so far is pretty quick to respond to e-mails.

There is only about 5 cycles on this pack and the weather is now crappy. It weighs 11.5 lbs. His bike weighs about 55 -60ish pounds.

We both ride more like cyclists than motorcycles / using the assist as assist and pedal augmentation. Still pushing over 40 miles 64 kms in 10 ah in hilly Vancouver takes a fair amount of peddaling.

 

[Mark_A_W]

Can someone please explain to me what happens to the BMS when the packs are in series?

Why is it affected? It doesn't make sense to me.


I can understand problems with charging if the charges are earthed, but not in use when there's no common earth.

Everything will work fine unless the BMS detects an overcurrent condition and opens. When the BMS overcurrent FET opens, but the one on the other pack stays closed, the full voltage of both packs will be across the FET, which will be double the voltage it's designed for. Poof.

Ypedal was having the BMS overcurrent trip while accelerating, and that is a likely scenerio in many systems. It's also very likely that one BMS will trip at a slightly different point than the other one.

The BMS really needs to be designed for the total voltage.

One other way around this limitation is to bypass the current limiter part of the BMS and rely on the controller to limit the current during discharge. You would still want the BMS to be active during charging.

If the controller is limiting the current (mine is 17amps, battery has a 20amp fuse, not sure about BMS), then even with 2 batteries in series, the system current would still be the max controller current (say 17amps)?

The current from one battery is passing through the other does the second battery BMS pass 17 amps or 34 amps?

It's so confusing for a mech eng like me..



Storm, I'd charge those packs of yours every now and again - mine came with instructions to charge every 3 months if not is use.

 

[xyster]

If the controller is limiting the current (mine is 17amps, battery has a 20amp fuse, not sure about BMS), then even with 2 batteries in series, the system current would still be the max controller current (say 17amps)?

Yes. Current is like the volume of water flowing through a hose. The rate will be the same at any point in the hose, and is limited to the rate at the slowest point, like a kink in the hose. Voltage is like the pressure that water is under. Every battery added in series boosts that pressure (potential energy of the electrons, aka voltage), but not necessarily the volume of water (number of electrons).

 

[Mark_A_W]

Yep, so if it's limited by the controller, then there's no reason not to run the packs in series. The BMS is never going to see more current than the max set by the controller.

The only other trouble could occur if one of the BMS cuts out the pack due to low voltage. But it's not hard to stay away from that, if you have a voltage meter of some sort on the bike.

I can't see why Storm can't run his packs in series, as long as the system current is lower than the pack maximum current. Just don't trip the BMS - I've never tripped the one on my Lithium pack.

 

[Storm]

Yes I also think it would be ok but I have the 48v LFPs now with the factory bms and charger so I wont muck around trying the others, I think I will leave that to someone else willing to play unless I use them later to extend my range, others on this site seem to be using LFPs wothout a BMS, how do they do that?

 

[BiGH]

I'm thinking of getting some of these to supliment my other lithiums on order - they still have no shipping date grr, and since my sla has gone,
I'm thinking of two 36v Yesa packs. Sam has emailed me and said they are fine for series 72v connection.

I've emailed back becuase of the guys here running 48v packs - what are the BMS components built for? will they run at 96v or 2 in series???

 

[BiGH]

so anyway i started emailing Sam @ yesa about the packs.

I went through many emails and got quoted a price in HKD....


that was higher than the ebay price!

so i'm not pleased with yesa at the moment. (S)he tried to inlate the postage price AND the unit price above what ebay is showing.

can someone pm me what they paid for the 36v 12ah packs?

 

[Freddyflatfoot]

Does anyone have any experience with these Yesa batteries?
Would like to know discharge rate and expected life cycle,
Thanks, Rob

 

[BiGH]

some notes on the BMS:

I have 2x of the 36v batteries.

text on the board: BL75v35.

fets are: irf3805s rated at 55v and 75a untested as yet at 72v (each pack is showing 40.6v system voltage at the moment- as received i haven't charged either yet)

 

[efreak]

Sounds like you ordered them. Did you?

good luck then, I wonder how storm made out with his new pack.

They certainly look alright.

efreak

 

[BiGH]

Sounds like you ordered them. Did you?

good luck then, I wonder how storm made out with his new pack.

They certainly look alright.

efreak

http://endless-sphere.com/forums/viewtopic.php?t=1481&postdays=0&postorder=asc&start=180

sure did. I'm getting a box for the BMS after the lecture i'm giving now - then after temp boxing of bms' and changing the front tube (grr) i'll give the bike a go at 72v( 81.2v fully charged)

 

[BiGH]

I need a cycle analyst to make more accurate measures, but.

I got about 20klms out of the pack before BMS cut off the power completely. (it was a 2x 36v 12ah packs). The added voltage makes you go very fast - i was keeping up with traffic and i coudln't really peddle enough to contribute (except as the pack was dying at the end). i need a bike computer to get accurate measurements of my speed etc. I might take the pack out again tomrrow, and put the heart rate monitor on that bike so i can measure speed etc, still need to measure amps used though. preliminary findings though - its a great pack, the chargers seem to work fine (on the first charge now). and my PRELIMINARY findings is this is a good pack. I do wish i'd gotten a larger aH pack however, might use this as the neighbourhood pack and see if i can order 4 36v 20ah packs or something! so much experimenting!

 

[Freddyflatfoot]

Good to hear that you are happy with the pack!
I just got mine yesterday from Storm, and have only just finished installing it! Already I can notice the difference, and I haven't gone anywhere, :lol:
Pack was nearly charged, only took about 10 minutes to top it off.
Oh, as for the charger, I noticed that the power lead is a standard fitting, so just replace the power lead with an Aussie one, like you get on a portable cassette player,
Cheers,
Rob

 

[BiGH]

yes but i don't want to have to open the charger to do that (warranty issues) - i'm happy to butcher after warranty period of over though! But i don't want to loose my investment just yet. I need to get a lot of distance out of this pack to pay off its high price.

my other problem is that i'm trying to find excuses to go out and ride it lol!

 

[Freddyflatfoot]

Ah, your charger must be different to mine!
Mine has a conventional lead that plugs into the charger, so I can just replace it.
How are you finding battery sag?
Went for a short run tonight, and was disappointed to find that the battery v sagged down to 22.5 v! I did load it up? to max amps of 15, but I would have thought that Li based battreies don't sag anywhere near that of SLA's?
Starting voltage was just under 30v, but very quickly dropped to about 26 v, and under moderate load was dropping below 24 v!
Dunno if this is normal, but certainly not what I expected of LiFePO4.
Rob

 

[BiGH]

Ah, your charger must be different to mine!
Mine has a conventional lead that plugs into the charger, so I can just replace it.
How are you finding battery sag?
Went for a short run tonight, and was disappointed to find that the battery v sagged down to 22.5 v! I did load it up? to max amps of 15, but I would have thought that Li based battreies don't sag anywhere near that of SLA's?
Starting voltage was just under 30v, but very quickly dropped to about 26 v, and under moderate load was dropping below 24 v!
Dunno if this is normal, but certainly not what I expected of LiFePO4.
Rob

I haven't measured voltage sag as yet. I'm awaiting my cycle analyst (shoudl be two weeks) and then i can get some decent figures on sag. I'm figuring that it will sag a bit though since off the bike after my ride the pack voltage was 78v... this is still above 72v!...

It is highly possible that the cells are just not designed for high c discharge possibly!