BMSbattery / EcityPower 48v Battery Review

I recently purchased a 48v 11ah lifepo4 battery pack from BMSbattery (http://www.bmsbattery.com/), which is the online store for E-city Power. I used the online chat session to work out the details of the order. I wanted a battery to fit in my Wilderness Energy cloth battery carrier. They worked with me online to determine what capacity battery could be configured to fit the dimensions of the WE carrier and provided the custom configuration at no additional charge. They also worked with me to be sure that the cutoff on the BMS would be adequate for my purposes. I got the 30 amp cutoff, although they could have supplied a 40 amp one. 40 amp seemed to high for a 11ah pack. They sent photos of the battery pack prior to shipping to be sure that the connectors and configuration were going to work. I got an e-mail notifying me that the battery had shipped just 6 days after I ordered. Not bad for a custom configuration. The battery arrived, well packed and fully charged, less than 2 weeks after I ordered it. I was really pleased with the whole ordering / delivery experience and the communication throughout. You could not ask for better service. The shipping was a little pricey ($95), but it did come all the way from China after all.

Here's how it was packed


This is what was in the box. They sent extra Anderson Power Poles to make the connection to the bike. Nice touch


This shows the connectors. The 110v plug is actually the input for the charger. Although this is a sturdy plug, I'm a little concerned that someday somebody might plug this into 110v, providing a spectacular end to the BMS and maybe the rest of the pack.


The pack fits perfectly in the WE tail bag. The performance increase above the standard 36v SLA pack is quite remarkable.

The charger appears to be good quality. It has a fan that is a bit loud when it is in full charging mode but the fan shuts off when the charger starts to taper down to float voltage. It's rated at 4 amps, 58.4 volts. It pulls about 3.8 amps off the 110v circuit when it's running. It has one quirk. If I take the battery off the charger and go for a ride, leaving the charger plugged in, the charger won't restart when I plug the battery back into it, even thought the battery has been discharged. You have to unplug the charger to get it to restart. Seems to me this might be problem for battery balancing. The resting voltage on the battery (coming out of the BMS) when it is sitting on the charger is about 53.8v.

The battery is nicely packaged in some kind of thick black shrink wrap with padding beneath it. The BMS is internal and completely enclosed. There are no external LEDs to determine what's going on with the BMS and no way to get to the individual cells without opening the pack. I gather that you can see the LED indicators on the newer packs from Ping Battery to confirm that the BMS is doing the right thing in balancing the battery. I guess that's a trade off with having this battery so nicely packaged. I wondered how the heat from the BMS would dissipate through the shrink wrap, but I've not been able to detect any heat either when charging or after use. On my longest ride so far I've only pulled about 2 ah out of the pack, so I really haven't put it to the test yet. I'm trying to break it in easily, like Dogman recommended. Just doing short rides and leaving the battery on the charger in between. I'll post a review about the performance of the battery after I've put some miles on it. So far, I'm a very happy customer.

FYI........The reason the charger doesn't restart is a safety feture built into the charger. You should alway disconnect the main power (120v) of the charger before disconnecting the the charger to the battery pack. The same goes for connection. you should connect the battery to the charger first then plug in the charger.

Chargers sometimes develop loose connections when carried around anyway, so leave the charger home as much as possible. Controllers are designed for some road vibrations but chargers are not.

dumbass said:

FYI........ The same goes for connection. you should connect the battery to the charger first then plug in the charger.

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That's actually not always the case. When I purchased a 36V/20Ah Li-ion pack the seller advised me to plug the charger into the ac wall outlet first then plug the charger into the battery to avoid a big spark. This did seem backwards to me but I did it, the one time I did not I got a big spark. I'm sure it varies from charger to charger but this charger must have a cap in there that causes the spark when plugged into the battery first. Powering up the charger first energizes the cap and prevents the spark.

Here's another charger where the seller says

Note: You must connect charger to AC power before connect to battery pack. Otherwise, the charger will NOT charge the pack and you will not get a RED LED indicate charging.

Click to expand...

http://www.batteryspace.com/smartcharger50afor37vli-ionpolymerrechargeablebatterypack.aspx

So go with what the seller says :wink:

-R

wakataka said:

The shipping was a little pricey ($95), but it did come all the way from China after all.

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So $298+ $95 for a 48/11Ah battery that'll do 40A if you want with a 4A charger; that's a good deal.

-R

If the battery holds up over time, it will be a good deal. I'll keep the forum posted as to how it performs.

wakataka said:

I'll keep the forum posted as to how it performs.

Click to expand...

Great - thanks! One of those would be just right for my BL36 now that its battery pack is waking up my eZip

What kind of cells in the pack, round or pouch? I'm assuming they may be 1c or 2c rate pouches. If so, they should be good for running 700 watt motors (22amp controller) like a bl36. If you have long rides over 10 miles full throttle between charges or steep hills on the ride a bigger pack would be best. Lots of stop and go hammers a battery too, so inner city riding might need a big pack too.

I cant tell what type of cells are in the pack. It's completely sealed up. It was curious to me that they offer both an 11ah and a 12ah pack. They said that they could reconfigure the 11ah pack to fit the WE battery case but not the 12ah.

The resting voltage on the pack is around 53.3, which would suggest 16 cells in series at 3.3v each. No way to tell how many cells there might be in parallel without opening the pack up. The weight of the pack, including the WE case and the foam padding I've added is 11.4 pounds. Pack by itself would be under 11 lbs.

I was really surprised that they would suggest a 40amp BMS with an 11ah pack. I doubt these are 4c cells.

I've got a WattsUp meter on my bike. With my old 48v SLA pack and a BL36 motor I rarely drew more than a couple of ah on my rides. During the week I have a relatively short commute and when I do longer rides on weekends I just go slower and pedal a lot.

After a couple of weeks break-in, I'll run this pack to near cutoff to see what I can get out of it.

If it proves to be as good as it appears now, I'm probably going to order another one for my wife's bike.

The amount of voltage sag at a given load is a good indicator of the C-rate for the cells. I bought a generic 48V/10Ah LiFePO4 pack in September and after it was broken in and I knew it was performing well I pushed it to 90% DOD. During this trip I jotted down the voltage shown on my WU meter over the course of the ride at 10A and 20A loads. Longer steady grade hills or on the flats are the the best places to do this as the current can be held fairly stable. Here are the voltages at 20A at the Amp-hours used:

48.0V 1Ah (~5.0V sag)
47.4V 2.5Ah (~5.4V sag)
47.0V 4.7Ah (~5.5V sag)
46.0V 7Ah (~6.2V sag)
44.5V 8.0Ah (~7.5V sag)

My battery is made of 5Ah pouches like a Ping and can be considered a 20A (2C) max battery.

I also have a 36V/6.6Ah LiMn pack made up of 3 Bosch Fatpack tool batteries and a 36V/20Ah Li-ion pack. The voltage drop at a 20A load for each of these packs is the same even though the first pack is one-third the capacity indicating those cells are a much higher C-rate (something I already knew).

-R

Russel - My WU is not mounted where I can see it when I'm riding, but it records the peak amps and the minimum volts. With a limited number of readings (3) so far and not pushing the pack hard, I'm seeing peak amps just over 20a and minimum volts just over 49v. These readings are on rides where the pack was discharged about 1ah at the end of the ride. I imagine the peak amps came near the end of each ride because I have uphill stretches near either end of my daily commute.

Sounds like the numbers I'm getting are pretty similar to yours.

One amp hour increments in battery size implies round cells to me. The pouches have come in 4 ah and 5 ah pouches in the past. If the round cells were a123's or other quality ones, no problem with that! The big problem with round cells has been bad spot welds that pop when the shippers kick the box around too much.

Dogman - I corresponded with Serena Fan at BMS battery and she tells me that all their E-bike batteries use pouch type cells. So the 48v 11ah battery has 16 11ah pouches. Even their "little frog" battery that hangs off the back of the seat post reportedly uses pouch type cells.

The thing that's scaring me a little is that they said first said it was a "Polymer Battery Cell", which I think translates to LIPO. There's just a little bit of language barrier (I don't speak Chinese but Serena's English is passable). I'm still trying to get confirmation that it's actually LiFePO4. The voltage readings I'm getting all but confirm this, but I still want to get it from the horses mouth. If it's a LiPO, I'm going to have to build a fireproof box on the back porch for it. It's not coming back into the house. I've seen the videos of RC batteries self combusting on YouTube. If a LiPO pack this big went thermal, it would light up the sky over half my town!

Cool, 11 ah pouches is something we have not current experience with that I've heard of. Gotta beat zillions of spot welds on cheap round cells like some of the junk on ebay. Lifepo4 is a type of lithium polymer, so I bet you have lifepo4, not the catch on fire lipo. Besides, the newer lipoly's are not so likely to cook off. But , ya know, I don't charge my lifepo4 in the house either. In the garage, which may burn the house down, but at least I'll make it out the back door alive if the garage goes up.

What are the specs on the battery? I couldn't find any on the website. Is it 10 amps continuous, 20 for a burst? That would make sense for a 1c cell. Or is it more? Do they say what the c rate for the cells is?

Dogman - The cells are LiFePO4. They sent me a draft catalog and promised to send a more complete one when it is final, which I will upload. They have pouch cells rated up to 230 ah. Here's a segment from the catalog, listing specs on pouch cells.

[pre]Capacity C-Rate Lifecycle Impedance
(Ah) (mΩ)
230.00  2C  2000  â‰¤1
210.00  2C  2000  â‰¤1
125.00  2C  2000  â‰¤2
105.00  2C  2000  â‰¤2
85.00  3C  2000  â‰¤2
21.00  3C  2000  â‰¤5
16.00  3C  2000  â‰¤5
13.00  3C  2000  â‰¤5
11.00  3C  2000  â‰¤5
9.00  3C  2000  â‰¤6
12.00  3C  2000  â‰¤15
11.00  3C  2000  â‰¤15
10.00  3C  2000  â‰¤15[/pre]

3c, Should be a pretty good cell then. Super. Of course, the best use of a 3c cell is 1.5c or maybe 2c. My brushless hubmotors have had average amp rates around 15-18 amps, so that battery ought to power a typical kit motor ok, as long as it doesn't have to climb hills for miles.

Whats the dimensions of the pack?
Thanks

The dimensions of my battery pack are L=275mm W=135mm H= 90mm. It was a custom size made to fit the WE battery bag. It fits with plenty of extra room. I'm not sure what the dimensions are on their standard battery packs.

I've got about a dozen shallow cycles on it now and it's still performing great. The most I've pulled out of it so far is about 2.5ah, so I really haven't yet got close to a full discharge cycle.

dogman said:

3c, Should be a pretty good cell then. Super. Of course, the best use of a 3c cell is 1.5c or maybe 2c.

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Is there a common published standard on how max discharge rates are established for different cells?

I'm curious to know if this is just the manufacturers who decide or if they have to follow some kind of certification process to be able to claim a certain rate.

For example, the cells in Ping packs are rated at 2c continuous. I've run them continuously at that rate or even a bit higher (2.5c) and I know that the cells don't heat up and that the voltage sag is very reasonnable (4-5 volts on a 48v 15ah pack).

On the other hand I followed YPedal's review of the 10ah Headway cells that are rated at 5c continuous and his experience seems to indicate that at that rate the cells will heat up and the voltage sag is pretty bad.

A 3C 15ah BMS Battery pack seems like a great deal if it can provide 45amps continuous with reasonable voltage sag and no over-heating issues. I just don't know if we can trust the numbers.

Unfortunately there is only the manufacturers claims, followed by our own testing. Most only provide any data for discharge at 1c. So to me, they are all 1c cells till somebody tells me different. We need more good reviewers, especially with batteries. I think we just about have the motors sorted out now, but batteries are still a can of worms exept for a few proven suppliers.

Btw, my 5c nicads from Justin clearly get warm and sag some at that rate. But so far it hasn't seemed to damage em. But hey, doncha kinda expect some warming and sag at 5c?

Even within the established safe discharge rates the higher c rate use is going to negatively affect cycle life in my opinon. But when a negative effect may still provide 1000 cycles, we can live with that I think. But knowing where the line you cross is, heading towards 100 cycles, would be a nice thing to know!

For me its kinda academic, I need more than 10 ah to get to town, and mabye 15 to get back, so I'll be under 1c on most of the bikes I own since I must have a big battery.

Below are the data I've got so far from my WattsUp. The columns show miles ridden, volts at the end of the ride, amp hours, watt hours, amps peak, volts minimum, and watts peak. You can get a rough idea of the voltage sag at peak amps by subtracting the volts minimum from volts at the end of the ride. It averages about 4 volts sag for an average of about 20 amps peak. At 20 amps, this 11ah pack would be just shy of 2c.

The WattsUp meter doesn't provide average amps. I can tell you that the 2.84 mile rides are my daily commute, which takes about 10 or 12 minutes, depending on how I hit the stoplights. So if I used 1ah in 10 minutes, that would be a an average discharge rate of 6 amps, correct? So my average rate of discharge is probably less than 1c.

[pre]Miles V Ah Wh Ap Vm Wp
2.84 53.16 0.81 40.80 19.70 48.87 966.40
2.84 53.08 0.70 35.80 20.39 49.13 1007.40
2.84 53.02 1.14 57.30 20.48 49.01 1008.10
8.53 52.60 2.62 132.40 21.68 48.74 1064.00
2.84 53.14 0.67 34.20 19.34 49.22 958.50
2.84 52.60 1.17 58.70 19.47 49.00 960.60
2.84 53.20 0.79 40.60 19.08 49.50 946.90
8.67 52.67 1.56 79.50 20.49 48.62 966.20[/pre]

That's good data and it's similar to my own battery log I started when I purchased my LiFePO4 battery (in addition to the trip log I've kept for years); .

View attachment Battery log empty.doc

Unfortunately I don't have any data for such low Amp-hours used so I can't make a comparison yet however here are the last 7 rides using my 48V10Ah LiFePO4 on my Kona.


So get some longer rides in and we can make some direct comparo's

-R

Yes, 1 ah in 10 minuites is a 6amp average discharge rate. Discharging at 1c would take an hour at 10 amps. So find a place to ride more or less non stop and I bet you can ride about 45 minuites full throttle before you run out.

Chances are you pull 20 amps or so starting, and cruise at around 12-15. Thats what I get with my Aotema motor. The stoplights make you sit there using 0, and pull down the average. The nice thing about stoplights is your battery likes a short rest. The bad thing is they kill overall distance range. But with a commute less than three miles, you won't be wearing out the battery too soon, or heating up the motor too much. 12 miles of stoplights would be a tougher ride.

Hi,
I guess you were lucky. These people sell garbage - hear my story.
I communicated with this company through email and told them I need a 24V 20A LiFePO4 continuous discharge battery for my bike, a charger and a 500W controller. I paid $423 for it online through PayPal and was eagerly awaiting my new LiPo battery. It It took 8WEEKS to arrive - 4 weeks "processing" and 4 weeks "shipping". When I received the box, it had a 250W controller, not 500W. Pretty much useless controller for my purposes.
I emailed the guy and he agreed that it was his mistake and said he would send me another one - but it has been 3 months and no replacement came.
The charger stopped charging after TWO charges - next day, pretty much. It just puts out 19V and does not charge. I connected to the company through Skype and for half an hour SHOWED the guy on camera all the testing of the broken charger. He promised to send another one - and guess what, NOTHING CAME.
The battery burned out in 2 weeks. I used it on Izip electric bike, which still rides nicely with simple SLA that comes with it. But this company's battery is completely burned (see picture). Needless to say, they promised to send another one and then stopped answering my emails. It's been 3 months and my $423 IS GONE....
I thought I'd save a few bucks but I lost all the money. And have a pile of junk in my apartment.
DO NOT BUY FROM BMSbattery or your money will be wasted!
ebikerider

Looking in another thread it seemed ecitypower put 175 amp Powerpole sets on as connectors. Is there a need for that size? I have 2 30 Amp powerpoles coming from my controller now. I'm wondering if Jack, or whomever does the fabrication, could put 30 Amp matching poles on the battery?