Ok, I bought a (slightly) used duct tape (Vpower) battery...

[sangesf]

You can't pull any more voltage than already exists. (well, not without a boost converter)

I use a 12V 50W halogen as a drain load on various cells, and it works fine. At about 3.6-4V, it draws about 2A or so.

You can even use a regular household 100W bulb, but it will be a much lower current drain (because it is higher resistance).

If the need arises, I'll try various low wattage / low voltage items to drain.
For right now, I have the 45.0v 5a charger doing a recharge after a 3ah run and will post the newest cell voltages in a bit..

 

[amberwolf]

Remember also that the BMS, if it's part of the pack, will drain down the high cells even when it's not on the charger--it will just take a while (if they're much higher in SOC than the others, a really long while).

It'll even do it while you're riding, as long as the cells in question are higher than the BMS's cell-level setpoint for that while under load. It's just that you are also draining at a much higher rate from all the cells.

So eventually, between charging and letting it sit, it'll balance out.

That's a part of why many packs seem to "gain" in capacity over time, when they're still relatively new, before usage and age begins to eat away at actual capacity.


The only test I definitely recommend you do is to verify that the high group(s) really are draining current into the BMS via the balance wire, as described previously. Otherwise you don't know if it's even working at all.

 

[sangesf]

So charger goes green..
I check voltage levels...
Cell group 1 - 3.75v
Cell groups 2 thru 12 - 3.35v

So what do I do?.... I unplug the balance wires and power leads (pre-BMS/battery side)..
I wait about 30 sec and plug them back in...
Plug charger in... It goes yellow (charging), for about 20 min...
I check voltages again and all cell groups are at 3.6x

Weird is all I can say..

 

[Rassy]

I think you may have just been getting close to full balance when you checked and got one cell group at 3.75v. The float charge drains off pretty fast. I gave my son and daughter-in-law a 48V 15AH Ping last year. Over the winter when they didn't use it much, and then didn't get it fully charged/balanced when they did use it, some cell groups got way out of balance. I got lots of "strange" results as it worked it's way back to full charge and balance.

Because they don't use the battery on a very regular basis, we hooked the charger up through one of those simple little 24 hour timers, set for 30 minutes on (and 23 1/2 hours off) out of every 24 hours. Now, after a ride, they first manually override the timer until the battery is recharged, then just leave it on the 30 minutes per day mode.

This is a Ping V2.5 with the LED's, and it is now staying fully charged and balanced. They never run it down too far, so I don't know if any capacity has been lost, but it really doesn't matter. I told them there are new better chemistries coming out, so when the battery dies, it's just an opportunity to get a better one.

 

[sangesf]

Well... I remove and replace all the wires and recharge...
3.75v each and when I remove charger and leave alone for a while, they all settle at 3.6v

I'll capacity test tomorrow and let ya know..

 

[sangesf]

Well after a couple of recharge cycles, I can say this is still a 15ah battery...

First (and second) charge cycle went to 3.75v per cell (45.0v) and then after an hour, settled to 3.6v per (43.2v) - all of that with charger staying connectEd..

Both capacity tests went basically the same...
5 miles into ride - check voltages
12 miles into ride - check voltages
22 miles into ride - check voltages
Up until cutoff.

After first 5 miles, I get readings of 39.6v (3.3v per) and ~ 2.5ah usage or 2 miles per AH or 24wh/m.
After 12 miles, still 39.6 and ~ 6Ah usage or 2m/ah or 24wh/m
Now it gets interesting....
After 22(.6) miles voltage is at 38.v (3.2v per) and now 11.6ah usage or 1.9m/ah or ~ 28wh/mi
Finally after 27 miles voltage drops to 37.2v (LVC cutoff at some point just below that) at 15.02ah or 1.8m/ah average for entire ride...

I will check the actual cell voltages when I get back in a few minutes and report cell levels..
(I'm letting the cells "self recharge" for a few minutes, before I ride it again for a min or two until it cuts off and I read the per cell V's immediately afterwards).

 

[sangesf]

So at the end of all, here's what I get...
Cut off was at 35.81v
Cell voltages were...
Cell groups 1, 2, 3 and 12 were.... 2.7x
Cell groups 4 thru 11 were at....... 3.0x

So at 27.86 miles and 14.94 AH later, I definitely have (via testing) a 15AH battery NOT a 20AH one.
(Unless EVERY cell group has ~ 5ah worth of bad cells - i.e. Extremely unlikely)

I can't find my damn tape measure, but once I do, I bet that the dimensions will fit one of the 15AH descriptions along with the weight, which I will check on Thursday.
Once I do those checks, and it confirms my suspicions, I'll let you know the sellers name (on eBay), so you can avoid her and her cheating/lying ways.

P.S. I also asked seller if I could have the invoice/receipt of the battery so I could, "warranty repair the battery/cells/BMS."

 

[heathyoung]

I think a lot of these sellers started out with good intentions, but at some stage along the way figured that few people would have proper instrumentation on board to even determine capacity for themselves, and so started short-changing them.

It sucks, but - as we have seen with some other sellers - when the heat gets to great, they just change their name, and their MO stays the same.

 

[sangesf]

Well...
Found my little tape measure and it's 190mm (7.5") x 180 (7.0") x 140 (5.5")
The MINIMUM size I found for a 20AH battery is 210x180x140 -- RED FLAG #1

Asked her why she thinks it's only 15ah and she says, "I don't know, maybe because you're only pulling 10a as opposed to 20a and a higher amp pull will give more AH? I don't really know anything about batteries", YET she has other auctions for some pulled apart and put back together batteries (along with some ebike kits and a Turnigy meter that you can get from HK for $30, that she has for sale for $70) AND her email address is something like ebikesales.com --- RED FLAG #2.

Asked her for the receipt/invoice (since it was supposedly purchased in June of this year) and she says she doesn't have it. --- RED FLAG #3

So, I would say, stay away from ICEMOM98 on eBay, since she's a sneaky little fargen icehole.


In the end I still got a 36v 15AH battery for $200 shipped, so it's not a total loss.

 

[heathyoung]

Yep - that sounds dodgy. If you have the gear to test capacity, why not use it and be honest...

 

[sangesf]

Yep - that sounds dodgy. If you have the gear to test capacity, why not use it and be honest...

And today for chits and giggles, I had my son hold onto my bike while he was on his skateboard so I could pul max amps for a full (almost) hour.. 17a controller..
52 min into ride.. LVC cutoff at 14.6AH
All cell groups again in the 2.7-3.0 volt range (Actually, they're quite balanced, so that's at least good since at least o know the BMS is doing it's job quite perfectly..

On a side note, still no reply from seller as to why she don't have a receipt if it was just purchased 4 months ago..
(Even a paypal invoice would work for "warranty repair")

 

[DAND214]

I think this is interesting.

location: Chicago, Illinois, United States as stated on Ebay!

Very interesting?

Dan

 

[sangesf]

I think this is interesting.

location: Chicago, Illinois, United States as stated on Ebay!

Very interesting?

Dan

I don't get it..

She said she bought it from Vpower in June... She lives in Chicago.. Not getting what you're saying.

I did check when she bought stuff from Vpower and the latest I found was March/April, the only way she "purchased it" in June is if she only paid for sea mail (which takes 2 months usually).

 

[DAND214]

Another ebay listing,

Custom made by Chicago Electric Bicycles LLC, the Electric Mountain Bicycle 48V is one of the best performing ebikes on the market today with a top speed of 25-30 mph and a distance of 20-30 miles on a battery charge. Ride at Lance Armstrong speeds and not break a sweat. You can still pedal like a regular bike, use only the electric motor, or pedal along with the motor (hybrid mode). Pedaling is optional.

He/she is one of our ES members.

Dan

 

[sangesf]

How about PM me with who it is, so I can contact them and find out what's going on..

 

[Nehmo]

Another ebay listing,

...Ride at Lance Armstrong speeds ...

Dan

'Course, we now know all such references to Lance Armstrong should be amended to "Lance Armstrong on pumpers speeds".

 

[sangesf]

I don't know if the seller on eBay is Lester from Chicago Bikes or not...
The eBay lister may have just bought stock from Lester and is trying to resell..
So unless I have proof, it's the same "person", I just stick with icemom98 being the "culprit" for the time being.

 

[DAND214]

Don't really know, just guessing.

Dan

 

[999zip999]

20ah Vpower = 16ah that's it. Or pay for a Ping 20ah and a 19.5ah. How cheap is cheap ? How much did you pay ? How much ?

 

[sangesf]

20ah Vpower = 16ah that's it. Or pay for a Ping 20ah and a 19.5ah. How cheap is cheap ? How much did you pay ? How much ?

The cost is not the issue, it's the way people portray what they're selling..
Just like you're saying... Vpower 20ah = 16ah? LOL...
My Vpower batteries.. All three that I purchased directly from Vpower, were at their rated capacity...
One of each.. 10AH, 15AH and 20AH.. All tested out to almost exactly to the rated capacity..

Now the seller sends me a message today that goes something like this...
"Well, these duct tape batteries sometimes don't live up to their capacity"

So basically the seller is saying to me, "When I (seller) bought it as a 20ah, I saw it only gave me 15ah, but instead of selling it as a 15ah battery and since the original seller (Vpower) sold it as a 20ah, I will sell it to you as one, as well."
In other words the seller is a flat out liar and is "passing the buck"..
OR
The seller just flat out sold a 15AH battery (as bought that way) and lied and said it was a 20AH.

 

[sangesf]

Here's ANOTHER BEAUTY...

On eBay, someone selling a motor kit and a 36v Lifepo4 "15AH" battery...

I ask if it's really a 15Ah battery and here is the response I get...

The battery says Beijing Wide-Power Electronics on it - I got it off ebay and don't have other info.
I have about 40 cycles on it. I don't know the actual Ah, as I don't have a watt-meter, but I got 24 real miles off of it.
If I use about 15 Wh per mile, that's 360 usable Wh, which is 67% of the nominal 540 Wh. I don't think the listed capacity is too far off.
24 miles at 30V LVC. A usable 67% stage of charge range seems pretty good to me. That's like cycling between 20% and 90%. What were you expecting?

What would I expect?!? WTF?!?? I'd expect the TRUTH! Up front.

 

[DAND214]

The cost is not the issue, it's the way people portray what they're selling..
Just like you're saying... Vpower 20ah = 16ah? LOL...
My Vpower batteries.. All three that I purchased directly from Vpower, were at their rated capacity...
One of each.. 10AH, 15AH and 20AH.. All tested out to almost exactly to the rated capacity..

You have or had 3 Vpower packs and they all tested at actual cap?

I don't see how it can be as rated as they don't put enough cells in the pack to get close, unless they are all perfectly match top Ah cells.
A 20Ah pack from them are 18 cells per series and at 1.1Ah per cell they still don't add up. At the lower rated 1.0Ah per cells they are even lower and we all know they would never put good cells in a pack they can dump on us.

Sorry, that's how I feel about it as I also had and still have the same crap stuff, 2-48v15Ah tested and even treed to match the cells but only got 10 and 11Ah out of them and the 20Ah was at 17Ah after testing, not to mention the shorted cells and BMS after less than 3 Ah discharge at only 7 amp load.

I understand how you feel about being straight a customer, That is what we are suppose to do. HONEST as possible. Sometimes we don't really know.

Dan

 

[sangesf]

When I say actual capacity, I'm talking within .5ah (9.5ah, 14.5AH and 19.5) NOT 20% like most people.
And FYI... I always run at below 1C, unlike a lot of other people that run em at 2C or higher.

Now the BMSs , that's a different story!

P.S. If you're only getting 17ah out of a 20ah battery, you DON'T keep it, you send it back and have your money returned or have them pro-rate the AH and have them refund you back the difference.

I've definitely gotten at LEAST 9.5ah out of my 10...
At MOST 15.2ah out of my old 15ah.
And 19.5ah out of my 20ah..

No doubt, I treat my batteries much better than most.


IT IS UNACCEPTABLE TO LET A TREND LIKE ALLOWING
PEOPLE TO SELL ITEMS STATING A CAPACITY THAT IS FALSE. WE MUST STOP THAT TREND NOW!!!

 

[amberwolf]

So at 27.86 miles and 14.94 AH later, I definitely have (via testing) a 15AH battery NOT a 20AH one.
(Unless EVERY cell group has ~ 5ah worth of bad cells - i.e. Extremely unlikely)

FWIW, you only need one group to be an average of 5Ah among the cells down for the whole pack to stop working at that point, when LVC kicks in, if your BMS has cell-level LVC (pretty sure it does).

Even just one bad cell that is far enough down to pull the rest of the group below LVC at about 5Ah short would do the same thing.

But I find it just about as likely that it was not really even capable of the full capacity in teh first place.

 

[Spacey]

If it's any consolation a so called 16ah Headway pack that I built for a friend has decided after 6 charges that it will only output 2 to 3Ahrs. Testing each cell as we type by discharging to 2.1V at 7A then recharging to full at 10A.

So far the first 7 cells only give 15.2ah the 8th cell gives out 13ah.... and this is at only 7A discharge the maximum my RC charger do, imagine how bad it is at 35A ... which is only 2C let alone the so called 10C continuous..... 160A my arse.

Still waiting to find the dud cell.

Hope you get your refund.