48v 20ah Mr. Lau Chan / Lifepo4.hk pack arrived (May '09)

RTLSHIP said:
My 48 v pack reads 59.5 v when fully charged. Thats what the charger goes to. Put multi meter onto DC charging part.
It should read 59 or 60. Once removed from charger mine will drop about 2 volts in half a day or so. I'm refering to my 48 v
15 ah.
At 15 lbs, I suspect this ebayer might have sent me 10 or 12 ah pack. I just emailed him. I say this because it should shut down at 30 amps not 10 amps. It's shutting down on 1/8 throttle with pedaling ( on BD-36) On the Brushless, no sweat.
Click to expand...

You probably have a prismatic pack. Prismatic are lighter (about 10% I think) at the same ah capacity and they read 59v charged - the 18650 packs start around 54v I think - safer for the BD36 controller which only has 60v caps

If your pack comes in 12ah 16ah flavors, that's a dead giveaway it's prismatic.
 
you should charge any 16S lifepo4 all the way up to 3.65-3.7V. are you sure the pack is fully charged? could the charger be shut off and you are measuring the resting battery on the charging leads?
 
There are a few random threads around here about using SLA chargers on LiFePo4 but in case anyone can tell me for certain, I have one of these:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=350175377855

which normally charged my SLA's up to 52v or so - can I use it to try to charge this pack?
What's strange about the SLA charger is I cannot read the output on my meter - it gives me an insane number like 1,800 volts, perhaps because there is no resistance?
 
any info about the pack? can you measure the individual cell voltages or is the BMS still wrapped up. the charger needs to see a load to operate i think so that is why your meter reading is not steady.

you may just need to keep charging until it climbs up to 59V.
 
dnmun said:
you should charge any 16S lifepo4 all the way up to 3.65-3.7V. are you sure the pack is fully charged? could the charger be shut off and you are measuring the resting battery on the charging leads?
Click to expand...

Remember this is 18650, not prismatic, is 3.7volts correct for 18650 lifepo4?
I thought 18650 is 3.3v ?

The charger outputs 53.1 to 53.4 volts (fluctuating rapidly) to my meter directly.

So it's outputting something.
 
for now, get it charged with the sla charger. I still wonder if the wiring is why it won't charge. I know it's hard, but try not to ride anymore till you solve charging. On top speed, when I ride 48v, it's with nicads, and some voltage sag. my lifepo4 is 36v.
 
Yeah I will not be doing any more rides until Monday or so at the soonest so I hope to fix it by then.

I had put the charger back on but I will stop it and pull out the 16s leads and measure the group voltages.

By the way, when things are actually working, is it safe to stop and start a charger on lifepo4?

ps. Mr. Lau had written back and said that I should use the regular negative hookup
So I guess it is proper with this BMS to use the same leads for output as for charging.
 
Any LiFePO4 cells, either cylindrical or prismatic, should be charged up to about 3.65V per cell group. So 16S = 58.4V charging voltage.

LiFePO4 cells will generally sit at about 3.2 or 3.3 V per cell group for most of their output curve, so unless it's hot off the charger, or almost drained, the pack will put out somewhere around 50-54V. Like dnmun said, it seems like you're measuring battery voltage instead of charger voltage.

Another possibility is that your charger needs to be adjusted or replaced -- you're not going to get a full charge on a 16S LiFePO4 pack at 54 volts.
 
THESE PACKS COME IN 10 AH, 12, 15, 20, 30 AND MAYBE 40. Dimensions on my pack are approx. 8.5"x5.5x4.5
No dead give away as this guy hasn't responded to my emails yet. Maybe your BMS probably has to be working
correctly to get a full charge unless you by- pass BMS which is not recommened, especially on a brand new pack that
needs breaking in and balancing.
 
you charge the cell up to 3.65-3.7V and it will drift off to 3.35V or so depending on the quality of the chemistry, but that is called the resting voltage. the nominal voltage for lifepo4 is 3.2V.

charge your 16S lifepo4 pack to a minimum of 58.4V and 59-61V is not too high, but not needed.

you should just keep charging as long as it will take current. keep charging until the ccurrent drops below 100mA, then you can stop, but keep track of that voltage.
 
dnmun said:
any info about the pack? can you measure the individual cell voltages or is the BMS still wrapped up. the charger needs to see a load to operate i think so that is why your meter reading is not steady.

you may just need to keep charging until it climbs up to 59V.
Click to expand...

You may be onto something. Isn't the charger output supposed to be "constant current" until it reaches a set voltage limit, and then switch to a constant voltage for cell balance. While in constant-current mode, the voltage should be only slightly above the battery voltage (just high enough to produce the specified current). Maybe just keep charging and see if the voltage climbs any. if it does, maybe it is working fine. Ideally, the voltage would slowly climb to about 58 or 59 volts, then switch to constant voltage mode at a slightly lower voltage.
 
I think the charger is incredibly slowly trickle charging the pack, thinking incorrectly that it's finished.

My meter is now flashing between 52.6 and 52.7 which probably indicates 52.65

For those saying that I am measuring the battery output, again, I also tried directly measuring the output from the charger with no battery at all and it's 53.1 - 53.4 - so maybe the charger is bad.

I will go measure the leads now and make sure it's not unbalanced.
 
16s breakdown, there are two groups that are 3.4 and two 3.2 and the rest are 3.3

52.6
49.3
46.0
42.7
39.5
36.2
32.9
29.6
26.3
23.0
19.7
16.4
13.2
9.8
6.6
3.3
 
Are you sure the charger is connected correctly. I found this and thought that it might help.

"On the BMS board the
battery negative connects to B-,
the power (load) negative connects to P-
and the charger negative connects to C-.
Charger and load + connect to the battery positive terminal. It is that simple."

Not sure if this is the same as your BMS, but worth checking.
 
Gow864 said:
Are you sure the charger is connected correctly. I found this and thought that it might help.
Click to expand...

Thanks for that gow864, unfortunately that's from a very different board at the bottom of this page:
http://www.ev-power.com.au/-DIY-Small-LiFePO4-Battery-packs-.html

and there is no C- on this BMS board from what I can tell.
This apparently is a newer/different design and even CammyCC shows it wired directly to the main output leads so I am going to stick with that for now.

I suspect something is wrong with the charger. It's perfectly possible it was defective to start with or the beating the package took damaged it somehow.
 
a lotta people get spooked with the initial charge, but after a few cycles it seems to settle down. i think your charger is ok, maybe the BMS is shutting down the charge because it feels like it has enuff. the voltage may come up at the end when it gets the last little bit.
 
Well I hope you are right but I don't think it's doing anything now.
It's supposedly a 6A charger, even if it was only 3A there's no way it should take the 3-4 hours I had it running today.

I had to shut it all down as I have to leave and no way I am leaving an unknown charger plugged in while I am away.

But I'll run it for a long time over the weekend. I did notice the charger fan seemed to turn on and off at times.

I sent an inquiry to Mr. Lau about the problem, we'll see what he has to say tomorrow.
 
I am starting to regret my decision... now he thinks he can charge me $26 for regular airmail to replace the charger... I'm screwed (I don't have $26 to spend if I wanted to right now)

email from Mr. Lau (Emma) (and by the way his English is remarkably good)
You are right, the voltage of the charger should 56-59V
Would you please send the defective charger back to this address?:
....

Because we should take the defective CHARGER to get a new for replacement.
Otherwise, I need pay it myself.
I appreciate your understanding
I will send you the CHARGER replacement soon.
Free shipping is just by sea mail (6-9 weeks to arrive)
Would you please upgrade it to air mail (7-14 days delivery)
It will be US $26 by air (7-14 days)
Click to expand...
 
Familiar mr lau customer service. :roll: Use your sla charger in the meantime, leave it charging 24-7, and don't ride to cutout for at least 10 cycles. It will be fine with the sla charger, but it won't balance so good without the higher output. Leaving it on charge all the time will to the same thing, but sloooooly, so you don't want to ride too far and get the pack out of balance if you can avoid it. Too bad you don't have an adjustable pot in your sla charger, if you did, you wouldn't need mr laus charger at all.
 
I have a feeling that Mr. Lau is what a call a "kitchen table" business.
I suspect many of our lifepo4 vendors are.
I watch alot of PBS specials and I've seen this kind of entrepreneurship demonstrated often in China/Hong Kong.

The free part replacement you get with Ping and CammyCC is probably because you are paying a 20% premium in price. I definitely didn't pay that premium so I guess I am getting what I paid for.

I have nothing against a family trying to raise their standard of living but after selling so many packs they should not be learning now to double box the items before they ship and to test everything before it ships.

I'll say this much, I get answers to each and every email and their English is very good. They warn me when they will be away on holiday or on Sunday. So they have learned good communication if it was not present early on. But they still should know to test every single thing considering how expensive it is to ship replacements.

I'm still curious how the shipping charge on their EMS invoice appears to be $300 or so unless I am interpreting yuan incorrectly. Something is funky about that.
 
dogman said:
Use your sla charger in the meantime, leave it charging 24-7, and don't ride to cutout for at least 10 cycles. It will be fine with the sla charger, but it won't balance so good without the higher output. Leaving it on charge all the time will to the same thing, but sloooooly, so you don't want to ride too far and get the pack out of balance if you can avoid it.
Click to expand...

I am afraid to try my SLA charger on this since it's supposedly a 3-stage charger and I am afraid of it charging lifepo4 the wrong way. Are there any charger experts around who are certain it's safe to try?

As long as I can temporarily get it back up to 52 volts I guess it's safe for short trips but sadly the whole point to this deal was to get that mega range, sigh.

I wish I could find someone else with this same charger to verify the starting voltage should be higher than 53
Cammy uses it and at least one other vendor on ebay, so maybe we can find someone.

Hey wait a sec, look at the bottom left here:
http://www.superetrade.com/images/cammycc/bicycle battery/pic/cc1.jpg

I wonder if that 53.8 is the charger output or the battery's? Because it's the same charger in the picture.

Also, my lights are the opposite of that's in the top left photo - theirs is red/green, mine is green/red

(since the bottom left doesn't have the lights on at all, I now realize the 53.8 is the battery output)
 
Hey dogman you are right, it is VERY slowly charging it.

Last night it was flickering between 52.6 / 52.7

Now after another five hours more it's flickering between 52.7 / 52.8

I suspect after a few days it might be up to 53. Ugh.

So instead of a 5 amp charger it's more like 0.5 amp, LOL

update: no, it seems that was just a fluke with my meter, it's not the best quality, now showing 52.7 steady

I've just risked putting the SLA charger on it. To my surprise, the charger seems to accept the battery just fine and is charging it, even though 52.7 is higher than my old SLA's ever reached.
 
After 45 minutes on the SLA charger I got nervous when I saw one of the four lights on the charger flickering so I stopped it.

But the voltage measures 53.2v now so it's working! After 5 minutes the voltage is 53.1

I'm going to let the charger cool a little as it seems to have gotten toasty on the bottom.

It's probably not desirable to stop and start a charge like that but is it safe?
Can lifepo4 just take charges in random lengths at random levels and just absorb whatever they are given?

This SLA charger supposedly is 3 stages, the first is 2.5A,the second is 1.8A,the third is 0.8A
I wonder if that's on a timer or relative to resistance and will cause problems with lifepo4 that have different resistance than SLA towards the end of the charge?
 
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