Yesa

[GGoodrum]

what would be great is a board that monitors indiviudal cells, then reduces the throttle signal until the cells are on the good side of their cutoff point (if this happens at all). This would stop the bms's from cutting out then having to be reset under high loads

Yes, that would be good.

Overcurrent could trigger the same response.
If the BMS had an opto-coupler with and open collector output to interface to the controller, it would be easy to adapt to almost any controller.

This is pretty much how the LVC circuit Bob designed works right now. If, under load, a cell dips below 2.7V, it cuts the throttle by pulling down the brake inhibit line. As soon as the load is removed, the voltage will rise. The LVC circuit will then "let go" of the brake signal. If you still have the throttle engaged, the voltage will drop again and the circuit will trip the brage signal again.

I've purposely run packs down to where this happens, in order to test the circuits. It usually first happens as I'm going up a slight hill, where the load climbs up to 40A, or so. You can feel the power cut, in and out, about once a second. If you back off the throttle a bit, the power returns and doesn't cut out until the pack is basically completely done. With a well-balanced pack, where all the cells dump at once, this "get home" capability could be short. In most of my a123 packs, which have seen a fair about of torture testing, there always seems to be one block of cells with a slightly higher "burn rate", or slightly lower voltage/capacity, so these will trip first. I can usually get another mile, or two, before it starts cutting out all the time. When that happens, the cells will usually take a full 2200-2300 mAh back in.

While I feel fairly comfortable draining a123-based packs all the way down, I'm not sure I'd try this with these other big LiFePO4 cells. In this case, what the LVC circuit would do is protect a cell that happens, for whatever reason, to get significantly out-of-balance with the rest of the cells.

-- Gary

 

[recumbent]

These packs are rated at 12ah... so getting 7.7 ah out of a pack isn't ideal... however they do sag

This all sounds soo bad. :?

Could it be, we are not figuring out capacity correctly? Getting slightly over half of what the manufacturer claims, is terrible, and bordering of a warranty claim.

I'm ordering 16 "Lifebatt" cells in January, I fully expect to get near 10 amp hr's they claim, not half. Nor do I expect them to sag so much they trip the bms. Maybe I should get a few more cells for parallel hook-up how depressing.

 

[BiGH]

yeah - i think its a sag issue now. Casue after i reset the bms its fine to go again....

anyways i'll b using those boards that use teh throttle inhibit in my next pack that sounds really really good

 

[Battboy]

These packs are rated at 12ah... so getting 7.7 ah out of a pack isn't ideal... however they do sag

This all sounds soo bad. :?

Could it be, we are not figuring out capacity correctly? Getting slightly over half of what the manufacturer claims, is terrible, and bordering of a warranty claim.

I'm ordering 16 "Lifebatt" cells in January, I fully expect to get near 10 amp hr's they claim, not half. Nor do I expect them to sag so much they trip the bms. Maybe I should get a few more cells for parallel hook-up how depressing.

NOT to worry recumbent - you will find no sag with LiFeBATT and should not have to order more cells! Nuff said.

Best,

Don

 

[Freddyflatfoot]

Yep, agree with BigH, I am sure it is a sag issue.
I am using a 24v 10 AHr pack, and can get 10 AHr out of it, but only draw 1C to 1.5C. (Recommended draw 1C)
The specs on the 36V pack have a constant draw rate of 2C.
So I expect that if you are drawing beyond the recommended draw rate, then the voltage will sag beyond the cutoff under heavy load, and you wont get the full capacity.
Seems if you are working within the draw rate of the batteries, then you'll get the full capacity of the batteries, and you should get the extended life benefit of Lifepoo.
On the Yesa website, they actually suggest the power ratings for the motors that should use the respective battery packs. I figure if you use a motor that is within those parameters, you shouldn't have any probs, but if you are using, say a 1500 w motor, and the battery pack is rated for say 300 to 600 w, then I reckon you can expect the battery pack to perform below expectations.
if you're using motors that are drawing currents way beyond normal power assist levels, then maybe Yesa batteries aren't for you.
Just my 0.02 worth.
Maybe Yesa can let us know what they think.

 

[BiGH]

Yep, agree with BigH, I am sure it is a sag issue.
I am using a 24v 10 AHr pack, and can get 10 AHr out of it, but only draw 1C to 1.5C. (Recommended draw 1C)
The specs on the 36V pack have a constant draw rate of 2C.
So I expect that if you are drawing beyond the recommended draw rate, then the voltage will sag beyond the cutoff under heavy load, and you wont get the full capacity.
Seems if you are working within the draw rate of the batteries, then you'll get the full capacity of the batteries, and you should get the extended life benefit of Lifepoo.
On the Yesa website, they actually suggest the power ratings for the motors that should use the respective battery packs. I figure if you use a motor that is within those parameters, you shouldn't have any probs, but if you are using, say a 1500 w motor, and the battery pack is rated for say 300 to 600 w, then I reckon you can expect the battery pack to perform below expectations.
if you're using motors that are drawing currents way beyond normal power assist levels, then maybe Yesa batteries aren't for you.
Just my 0.02 worth.
Maybe Yesa can let us know what they think.

Yes I agree, however i also think there is a weak cell or two. i'm running a 35a controller, and the packs are 12ah... meaning 2c is 34a so i'm almost running within specs!. however i believe due to the weak cell, thats why its not giving all it can be.

This is where dewalt probably has the advantage of having crazy discharge rates. Either way the Yesa cells run my bike the 25k each way to work i need so i'm happy. I'm almost up to a saving of $200 - I've paid for the 48v of lead i used before the batteries, and about to start making inroads into the cost of the yesa packs.

 

[Freddyflatfoot]

BigH,
You're getting 50 k's out of a commute, or are you charging at work?
If you are getting 50 k's, that's impressive! Is that with or without your own assistance? (I'm thinking without with the speeds you do)

 

[recumbent]

NOT to worry recumbent - you will find no sag with LiFeBATT and should not have to order more cells! Nuff said.
Don

Thanks Don, what a relief it is to hear, and look forward to dealing with you. 8)

I was wondering if the batteries with the rolled-up, soft, (prismatic) type cells that is causing the problem. The small, cylindrical ("F" size) Li-mn cells I have in the Bionx system perform excellent the first season, so far.

edit: even the nicad's in the old Heinzmann unit also worked great, but heated-up when pushed hard, then the emergency pulsing action kicked in till it cooled.

 

[Battboy]

We have found prismatic cells can "get hurt" much more easily than the cylindrical cells. Sandia has passed the LiFeBATT cylindrical cells on all their "roughness" tests which includes shock, vibration, and abuse of the cell that could occur in a real world environment.

Prismatics, because of their soft format can suffer damage much easier if the integrity of their outer case is compromised or suffers from the shock of being on the road.

Best,

Don Harmon

 

[BiGH]

BigH,
You're getting 50 k's out of a commute, or are you charging at work?
If you are getting 50 k's, that's impressive! Is that with or without your own assistance? (I'm thinking without with the speeds you do)

I charge at work - use 6ish amp hours going there, and 5ish coming home. I always peddle along with the bike - i upped the gearing so that i can peddle along, and while i might only contribute a very small amount, its still noticeable and gives me a perfect fat burning workout 60-70% max HR

 

[Freddyflatfoot]

Just out of curiosity BigH, I would be interested to know how your pack would go if you limited your max amps, to say, 15A?
Yeah, might be an average lower speed, just reckon your range would increase by a fair amount!
On my MTB, is fairly easy for me to do that, as I can just change gears to reduce the load on the motor. I often do this going up hill, change down until the amp draw is around 8 amps, and just amble up the hill. Easier on me, the battery, and the motor!
You are getting/have a CA, they can limit the amp draw?

 

[BiGH]

Hi Rob,
The CA sure can limit the amps, however since mine is the standalone model, it means I'd have to make a small circuit (i CBF atm).

I've ridden at lower speed along the tracks, got 40k no problems, some was high speed, most was under 30kph

 

[calinb]

My 48 V / 20 Ah pack arrived about a week ago and I've made a few commutes to work (~13.5 mi and 700 foot climb and descent each way). The Yesa LiFeP04 pack powers my Crystalyte Cruiser on a Target store Schwinn Ranger that I purchased on sale for only $120.

Wow--this is what I had in mind for an electric bike! My 18 Ah SLAs could only get me to work if I contributed a lot of pedaling--especially now that temperatures are below freezing in the morning. With the Yesa LiFeP04 pack, I can pedal up the 2 mile / 6% hill climb at nearly 20 mph and then barely pedal again for the remainder of my ride. The motor puts out much more power than it did with the SLA batteries while going up the hill and I no longer get a "low voltage" light from my throttle LED. I wonder if I even need to pedal at all on my way to work with this pack. (Though it is nice screaming up that hill at 20 mph and getting a bit of exercise at the same time.) Also, I no longer have 30 lbs. of SLA batteries in my front panniers (in addition to another 30 lbs. of SLAs in the back) and the bike handles so much better without the weight on the front wheel.

Sam was very helpful at Yesa and answered all of my question promptly via email and IM. I had originally expected to receive the pack and two chargers nearly a month ago, but in a subsequent IM chat, Sam recommended that I wait for the latest LiFeP04 cells and the new CPU based BMS to be released to production.

So I waited. When the pack finally arrived it came via UPS express and I received it in excellent condition--thanks to the excellent Yesa packaging. I'd purchased a Tubus Cargo rack and Ortlieb Bike Box 3 from The Touring Store and I was pleased to find the Yesa pack fit the Bike Box 3 exactly as I expected. The Bike Box 3 is a nearly perfect box for the Yesa pack. The pack fills the box with just enough room on the sides for the BMS, a fuse block, and the Bike Box 3 straps.

See file comments below for more information.

Regards,

-Cal

 

[calinb]

One more photo showing the Yesa packaging. The white boxes within the shipping carton (above and below broken styrofoam strips in the middle of the photo) held the chargers (one shown). The battery pack was wrapped in plastic in the middle.

-Cal

 

[BiGH]

I have to say i'm very impressed with the customer service from YESA. I've had 2 international phone calls and without prompting I've been offered a partial refund / compensation for the low capacity of the cell (which i tend to agree is a good offer) since the battery does actually work, its just the capacity was not up to scratch.

I had low expectations of YESA, but have to say they've won me over in a big way. I woudln't hesitate to buy another yesa pack

And from my understanding i'm the first one to have a low capacity pack.

I'd highly reccommend YESA packs to anyone - with one caveat - buy a single cell charger as well when you buy the pack! ($12.99 USD extra) it just saves issues if you do end up having a problem!

I also found out there are some very interesting developments in the BMS' at YESA. It looks like they are going to be a force to reckon with. Apart from Storm and I, I don't know of anyone else that's had issues, and YESA recitifed the situation in both cases.

 

[D-Man]

How much do these Yesa battery's cost?

 

[kbarrett]

How much do these Yesa battery's cost?

Go to ebay. Search for "missbattery".

Cost is dependent on voltage and amperage.

 

[calinb]

I bought an extra charger ($50 each) to keep at work. All U.S. $

(1) 110U.4820F LiFePO4 Battery Pack 48V 20AH 1 $950.00
(2) 110U.483A LiFePO4 48V Charger $100.00
UPS Express Shipping $125.00
PayPal credit card fee $23.50
total $1198.50

-Cal

 

[BiGH]

Have to say that the chargers that yesa ship are great, they don't individually balance cells fully though, so a single cell charger may be required, but they charge fast and are reliable (i do trips with chargers in my bag and haven't had any die yet - where as Albie's been through 3 SLA chargers already!)

a 2nd set at work is great too, as it means you can take 1/2 the batteries = half the cost and half the weight on ur bike!

 

[D-Man]

I think that when it comes to buying the premium battery packs, the seller should test the high dollar pack and give the buyer a printout of the performance data for that particular pack. That way there won't be any problems. Not everyone is going to have an ebike meter to verify that the pack is within spec.

 

[BiGH]

Hi Dman - i agree, however there is a problem with that. What do they test it at?

ie should it be drained at a constant rate of 35a? 20a? both? what if its for a motorcycle ?

the capacity depends on the application.

BUT

i do agree that it would be good if they could be tested at ONE or TWO of these - to get an idea of capacity.