More LiFePO4.... Free_shopping88....????

I've only used the pack once so far because it's only feasible for me to commute by bike once or twice a week. I left it on the charger last night to charge it for the second time. Except for the cut-outs, it worked well when I used it after the first charge. If the BMS detected low voltage on one of the cells causing the cut-outs, I'm hoping the cells will balance out as the pack is discharged and recharged over time.

How did you determine which of your cells was going low? Also, what did you use for your 3A load?
 
Hi, To measure the cell voltages. using a DVM, cell one goes form the Negative on the BMS board and the bottom of the right hand resister. Second cell would be from the bottom of the first resister and the second cell. Moving across the row of resisters gives you each cell voltage. You can tell when your reaching the end of the pack as the voltage starts dropping fairly rapidly as the weak cell(s) begin to die. This started around 36 volts at about 5 hours. The BMS shut off when cell 3 got to 2.18 volts.
My wife is a little upset as I have the dining room table covered with wires and the two of our electric range burners I am using. I have a Watts up Meter that I can detach from my MTB and I am using this for AH, pack volts, watts. etc. I started out using a couple of cheap porcelean light bulb fixtures and 60 watt bulbs. This only was drawing 1/2 amp. Then I saw the stove and had enough jumper wires to hook up two burners. The bulbs and burners are all hooked in parallel. This draw is 3.50 amps at full pack voltage and 3.27 amps when it died. To be fair the pack should reach full potential after a dozen or so cycles and the cells become more balance. We will see.
What is strange, cell one reads the lowest voltage through out the test until near the end when cell three suddenly starts dropping. At cut off all the other cells are still over 3 volts. I either have a weak set of cells or I am hoping that cell 3 will come up after a few cycles.
I am waiting for a rear wheel and a Topeak bag for MTB. Hopefully will have the Bike back together late next week and do some real world tests. I have a wilderness brushed 24 volt front motor that I am running at 36 volts. Before I screwed up my home made A123 pack, the bike drew 25 amps peak and the voltage drop was fairly low. I have a feeling the voltage drop will be much higher with this pack. This will cause the BMS to shut off much sooner as a 3 amp load vesus a 25 amp load will make a cell to reach cutoff much sooner at peak load. Anyway Test cycle 3 is under way and will let you all know.
 
 
Hello, Tests up to 5 cycles with a little over 3 amp draw. Cell 3 is the one that drops and cuts off the BMS at 14.5 AH from what is suppose to be 20AH pack. There has been no significant increase over cycle 1. I do not feel it will get any better. I will email LAU today and see if he responds. I see he is getting negative feedback on some of his packs for Slow delivery, wrong chargers, low AH. I think he needs to re-think what he is doing if wants to stay in the Lifepo4 Battery business. Test 6 is underway with an A123 cell hooked in paralell to cell 3. I want to see if the pack AH increase and see what voltage and which cell shuts down the BMS. Hopefully I will have MTB back together at the end of the week and will test pack in real life.
 
patriot, do you charge your battery through the jimmy wu BMS? mr ping mentioned that the signalab board is his board and he did not know how there were other boards out there with his name brand on. so like mr cammycc just said, this is all suspect.

i wonder if you are even charging the battery up to total charge. the BMS may shut down below the maximum amount of charge is stored, so you have less capacity. but if you have cells where the resting voltage is 2.18V, they are likely in bad shape already from being reversed under load. make sure all the cells have charged to 3.65V, every cell, which you can measure just like he said from the base of each resistor to ground. while charging.
 
dnmun, A little misunderstanding, the 2.18 on cell 3 was when the BMS cutoff during the test. The latest test with an A123 cell hooked to cell 3 kept cell 3 voltage up throughout the test. The BMS shut down at 14.7AH and was shut down by either cell 4 at 2.25 volts or cell 2 at 2.27 volts. The charger seems to be set at 43.6 to as high as 44.1 volts. The pack resting voltage is 43.4 to 43.8 volts. Got my curiosity up so I just checked the pack that has been charging since late afternoon yesterday until this morning. Do not know how LAU is getting the Signal Lab BMS. It seems the BMS balancing is not that good. The BMS when balancing the resistors that are shunting get warm, they are all cool so it is not balancing. The lowest cell is cell 3 at 3.35 volts while the highest cell is at 3.72, with everything in between. Cells 2 and 4 are over 3.65 volts. So I can conclude the pack at a low amp draw 1/6C only is 14.5AH not the 20AH I was sold. Under a peak 25 amp draw, I am sure my amp hour will be much lower as I will hit the cutoff voltage sooner. Really nothing I can do about it as I haven't heard of anybody getting satisfaction from LAU. I want to get my MTB running again so I don't have to ride my electric stingray through the snow. Should get the rear rim today and then I have to take it to the LBS to get the gear cluster swithed to the new rim. I am hoping to have bike back together this weekend.
 
I think you may need a charger that puts out more voltage to get pings bms to do any balancing. Before I broke it, mine was putting out somewhere around 46 v. Look inside the charger for some adjustable pots.
 
I'm getting a little more delicate with the throttle so the pack isn't cutting out as much. Yesterday, I was still able to cruise at 31MPH on the 6-mile outbound commute but it was down to 27MPH at the end of the return commute (which is acceptable to me). The pack seemed to cut out more easily at the end of the return trip so I had to be even more careful with the throttle. I may wire a switch on the handlebar to reset the pack because it's a pain to stop and disconnect/reconnect the pack to reset it.

I've got a Watt's Up meter on order so I'll be able to get better info on the pack performance and recharging. It should work much better than any of the multimeters I've got.

I also wanted to note that my original battery bag with the BD36 kit was getting a little beat up (flying off the rack one time wasn't very good for it either) so I ordered a bigger bag from Nashbar last year. The new bag was too big for the SLAs but it fits the new lithium pack perfectly with about an inch to spare at the top (not bad for $15):
http://www.nashbar.com/profile.cfm?category=&subcategory=&brand=&sku=15404

The bag only has a pocket on the BOTTOM for storing the rain cover but I wish it had one in the top like the original bag has for storing misc stuff.

I'm still using the original (wimpy) rack but after a few disconnection mishaps, it now appears to be solidly bolted to the frame.
 
maybe you can fit the charger in the top of the bag and be able to recharge anywhere, like justin did. maybe even carry a lightweight 2 wire extension cord too so you can reach 10-20 feet to a plug from where you have to lock the bike, nice size for that, plus tools on top.
 
I used to carry my charger in my backpack, along with my laptop and other work stuff. Where I work, there's no place outside to plug in the charger so I always had to disconnect and lug the heavy SLA pack upstairs and charge it at my desk. Also, the facilities staff don't like bikes parked anywhere but the bike racks or bike lockers and would absolutely freak out if they saw an extension cord running to an outlet. Now, with the Lithum-cell pack, it doesn't need to be charged immediately after use so I just leave it on the bike and there's plenty of energy for the return commute. I put my accessories (tire repair kit, stubby phillips screwdriver, and lights) into a plastic bag and it sits on top of the battery pack. The battery controller and some of the wiring are underneath it but they seem to be durable enough to handle it.
 
You wouldn't happen to work at the PARC, would you? :wink:

As long as the premises and goods are secure, that sounds like a good strategy.
 
I took a chance and bought a 48v 12ah battery from free_shopping88 and hooked it up to my BL36. I just took it for a test run and it is a serious improvement from my sla 36v pack. I also did a stationary test with my crystalyte 408 and a 36v controller and it worked well with that. It took about 3 weeks to recieve it and I did get a prompt response to all my inquiries. I will keep you posted as to any problems that may occur using it.
 
Goody for You! :D :D :D Sometimes some not defective stuff gets shipped, but we never seem to hear about the good ones. We need all the feedback, including the good.
 
wavedog- I've got the BD36 setup and am curious if you're also having cut-out problems during acceleration or uphill? What is your top speed? I'm not seeing any improvement after 6 recharges but no degrading either (I'm still getting over 30MPH cruising on level pavement).

swbluto - I contract for a number of different companies. The only one I'm able to reasonably bike-commute to is in Mountain View near Google and the Shoreline Amphitheater. I had a short contract with Qualcomm down Foothill Expy that I bike-commuted to last year but that's over now (and they've since moved to Santa Clara). I attend the Thursday PARC presentations occasionally.
 
dogman said:
If it's mr Lau at least he changed his picture. In the past, it was pretty easy to tell when he changed names since he used the same pic on all his identities. It seems to me like pings pics are the only ones that show a battery that is the actual sise of the one in the auction. At least his feedback is mostly batteries and not fashion bracelets. But he may have sold a few batteries to himself to get started. Shipping is quick to mom's house.

Anybody out there one of the buyers? Let us know.
Click to expand...

Yes, we agree with you, this person have many many eBay accounts to sell the LiFePO4 battery, for example:free_shopping88, leebenmr08, mp3hk, playgame6969, jimmywu66.
All above eBay account is Mr Lau's account, the battery he sell is fake battery, the buyer be aware of this seller.
 
Cammy, you might want to look at a recent thread ,48v-20ah lifepo4 lasts only 34km on 5th cycle. The guy bought one of your batteries, and it looks to me like it weighs 2 kg less than the specs for the battery he bought. Whats going on?
 
Please note folks that my new Ping 48 volt 20 ah weighs 10 kilos, and of course works fine. I havent done a D/C test yet, but it can pull over 40 amps without any problems.
otherDoc
 
Mr Transistor
I torture tested my battery yesterday. Went up a very steep incline and up and down rolling hills for several miles with some pedalling and lots of full throttle and the battery seems to be working okay (no cutouts). I didn't have my onboard computer installed but I will do that today and I will start to record data better.
 
Mr Transistor, The cut out you refer to is the BMS, which is set to protect the battery at about 30 amps. When I first got my 48V 20AH duct tape LiFePO4 batteries I had the same problem. After getting a Watts Up meter, it turned out the cutoff varied by several amps between different BMS's, some cutting off under 30 amps. So I bypassed the BMS for some short tests, which solved the problem, but left me without BMS protection during discharge. As suggested elsewhere, I beefed up a bridge thing inside the BMS which now allows me to draw over 40 amps but still provides BMS LVC protection.
 
I got my Watt's Up meter in the mail recently and will start taking readings. I'm pretty sure that my BMS is cutting out way below 30A. I think the quality of individual cells in my pack varies a lot and one of them is probably dropping voltage too much under load. The markings on the chips of my BMS have been scrapped off so it will be a little difficult to accurately reconstruct the circuit. My guess is that one of the pins on the DIP chip probably has the voltage reference and when a cell (group of cells) falls below that reference voltage, the BMS shuts down it's FETs until the BMS is reset. I'd be willing to lower the reference voltage a little but am hesitant to disable it. I really don't want to pull apart the pack because of a destroyed cell unless I really need to.

wavedog- with your BL36 kit, what wheel size are you using and how fast are you able to idle on level ground?
 
sacman has a jimmy wu thread and we discussed the BMS over there. the shunt wires establish the voltage drop for a given current, that voltage is compared to the reference voltage by a comparator or op amp in the end of the DIP and that is either buffered to drive the gates of the output fets or drives them directly.

the fets have such high on resistance that they overheat and melt the solder out from under the tab and it runs down and shorts out the parts, and melts the wires too. everybody ends up buying a BMS from mr ping since it appears that the signalab pcb is illegally copied (it is mr ping's pcb) by jimmy wu or his supplier and the parts are all cheap and not very reliable. so it is crap. also the welds are of such poor quality that the leads have actually burned off in one pack, and sometimes the balancing leads break off from the individual cells so they can't be balanced.

you will need to walk your voltmeter up the shunt resistors on the BMS, measuring the voltage to ground (negative battery terminal) at the base of each resistor to establish what the voltage across each cell is, then you can start learning about how to keep the battery alive. make sure all the cells are charged before going any more, it could be dead already if the balancing leads have broken. but usually lifepo4 cells will be closely balanced, except the end cells seem to go out first.
 
Good Morning, Been busy. After low amp draw testing on my supposed 36 volt 20 AH form MP3HK and finding the most I could get out is 14.5 Ah, the BMS balancing is lousy. Lowest cell 3.35 volts highest 3.70 volts after an overnight charge. I manually charged all cells to 3.70 volts still only 14.5 AH. I wasn't thinking when I mentioned the charging, I was measuring the output volts from the BMS not the charger input, it is upto 40 volts, so it is fine. Now I hooked the battery to my MTB with a wilderness brushed motor. The BMS cuts out at 15 amp draw. I know the bike draws around 25 amps peak. Tried to bridge the sense wires, had little effect, cuts out around 17 amps. So i rigged the output directly to the bike, bypassing the BMS, and when charging I use the BMS. Voltage drop is higher, of course, than my A123 pack, but tolerable. I am debating to myself to get a Ping BMS from "Ping" or go with Gary's BMS as I want a low cell voltage cutoff protection. The advantage of Ping's is cost and quick exchange. With Gary's I would have to change balance plug let alone soldering the components and test and calibrating it. But I like the effort all the people put in to design this and would like to support them. What do you all think? The most I have drawn out of the pack is 9 AH and probally will not dare to go over much more than this until I get a good BMS.
 
i would recommend getting a BMS from ping. it plugs directly into the sense plug from the battery, since jimmywu uses a copy of mr ping's signalab pcb. the fact that you did not get far by soldering up the shunt means it is cutting out on LVC. imo
 
Hi, Should really proof read before submitting, charger is 46 volts, Yes I was thinking the same with going with Ping. I do not think it is the LVC as with my low amp test as soon as the voltage of the low cell came back up, the pack turned back on. I have to unplug the back to get the BMS to turn back on which tells me it is the over current draw shutting down the pack.
 
http://cgi.ebay.com/48V-20AH-LiFePO4-Battery-Electric-Scooter-E-Bike-Safe_W0QQitemZ220309819631QQihZ012QQcategoryZ11332QQcmdZViewItemQQ_trksidZp1742.m153.l1262

Has anyone ever bought a LiFePO4 battery from soso mum? The price is really really good!! :D Only 51 cents per watt.
 
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