lifeP04 48v 20Ah compare - Cammy Vs Ping

[ping]

Dogman,

If you take a look at Cammy's listings carefully, you will find she's using at least 2 kind of cells with different density and pricing.

BTW, 300x150x110mm for 48v20ah is ultimate density of LiFePO4. It's hard to make it.

Also, please give me a chance for advertisement. Almost all her ebay prices are higher than ours except 48v20ah. However, her shipping cost is really low, but it's air mail.

Ping

 

[etard]

What happened to vaporthug? I think the obvious winner is ping because he has stuck his reputation on the line and cammy is nowhere to be seen. Lets have a followup.

 

[dogman dan]

I see what you mean, Mr Ping. How can a 48-15 and a 48-20 have the same weight? Could it be the same way free shipping costs $65? Part of why we allways can't wait to see the tape removed from all sellers packs. But we don't have to strip your packs to know what is inside anymore.

I see gossip about the c rate of the cells you are using now, but haven't seen you say what it is. Are they 3c, or more? A few people are doing above 2 c discharge rates, so how about a test at 2 c? We know most any cell does well at 1c, but most of us discharge em between 1 and 2 c.

 

[julesa]

Hi Ping,
I also had a question about your 48v 20Ah battery. In your ebay page for this battery, it says:

Maximum Discharging Current: 60 Amps
Discharging Cut-off Protection: 40 Amps

I'm confused. Is there a delay after exceeding 40 amps before the cut-off protection happens? Why is the cutoff only 2c? I thought these cells were rated for 4c continuous?

 

[StevenR]

I have to be careful to avoid BMS cutoff on my 48V20aH Ping pack and I'm usually not careful enough - at least once on a ride I will trip it. My cycle analyst has read 58.08 and 59.48A max on the two rides I have on it. 58 is close enough to 60 to say the 60 is actually where the BMS trips. Note that I use a cycle analyst for battery output and watts up meter on the charger and they agree within 3-4% (discharge aH to charge aH) so the 58.48 might actually be exactly 60 amps because my CA calibration is off a little bit.

 

[ejonesss]

also what's confusing is how can you draw more than the cut off?

Hi Ping,
I also had a question about your 48v 20Ah battery. In your ebay page for this battery, it says:

Maximum Discharging Current: 60 Amps
Discharging Cut-off Protection: 40 Amps

I'm confused. Is there a delay after exceeding 40 amps before the cut-off protection happens? Why is the cutoff only 2c? I thought these cells were rated for 4c continuous?

 

[StevenR]

I suspect even a 24 ah battery would be a big enough one, but a 30 ah would do fine I'm sure. But Pings bms would still cut out at 60 amps though.

I've been thinking about adding one or two 10 aH in parallel with eBikes or home-made shottky diode protection. Would this take care of the cut-out problems ie. would they play nice and share the load such that I could pull 65A without cutting out the smaller pack or would they load share 50-50 and cutout the smaller pack all the time. Would there be other issues related to running two different capacity the batteries in parallel? An additional 10 aH would extend my range and only be a few pounds heavier than the 12aH of lead I was dragging around.

 

[StevenR]

I'm pulling 2.1kW+ in steady state cruise (35-40 MPH!) regularly without a cutout. I'll look at what the current is (I'm headed out for a ride in half an hour or so) but the voltage is about 46.5 so that must be close to 45 amps.

 

[lesdit]

Does the Ping type pack BMS cut off the moment the current hits 40 amps, or is it more of a time delay thing?
I am considering running a Ping pack in parallel with a Dewalt based pack for bursts of high current on an etek
powered light duty trail bike.
The idea is the ping pack would sag under power causing the a123 pack to take the more aggressive current
hits.
I need current spikes of 150 amps or so.

 

[StevenR]

My Ping BMS does not appear to cut out at 40 amps at all. It cuts out right around 60 amps and then instantaneously.

 

[lesdit]

60 is pretty good. Does the BMS reset buy itself, when you back off on the power? Or a reset is needed?

Maybe the seller, the honorableness Mr. Ping, can say if all 48v 20ah packs are able to provide
60 amps now.
Maybe we can get some more detailed specs. I'm surprised nobody has un-mummified these packs to take
snapshots of the cells.
Perhaps Ping can't call out the specs because they are buitl from limited supply cells from various manufacterers
as B stock ( not fully up to spec ).


So for etek/mars: Two pouch cell packs in parallel, and a third pack with series string of a123's for amps in high demand
short duration spikes.

 

[dogman dan]

I could be wrong, and often am, but I interpreted the max amps, 60, to be cut off setting on the bms. Max continuous is a ampreage above which the battery will get accelerated wear or even damage? Mr Ping could set us straight on this too. So the bms may allow a damaging ammount of power to flow, so it can handle spikes on startup, etc, but the battery should be selected to avoid continuous draw above the max continuous spec. That is how I have interpreted it.

Again beating the dead horse, untill i see any batteries test at more than 1 c, I consider it a 1c battery.

 

[StevenR]

I'll be the test case to determine minimum battery life caused by abusive use. Although I want to add additional capacity in parallel for 80 to 100 mile range, most of the time I will be running a single 48V 20aH pack and my normal operating parameters would push it to 2C+ at 2100 watts continuous. I have been looking at how to bypass the BMS on discharge so that peaks will be slightly over 3C. We'll see how long it lasts. Although even at 3-4 charge cycles per week (and probably none for several snowy months) I wouldn't expect any answers for more than a year. I'll see if I can convince Cammy to sell me a pack at a reasonable price (How about it Cammy? - I'll go $500 bucks) and I'll alternate them under similiar canditions to see which one holds up better...

 

[lesdit]

couple of quick questions:

Does the BMS reset after over current by itself, after N seconds, or what ?

What markings are on the individual cells. It's about time we find out what entity makes the cells.
Ping isn't. Cammy isn't . Reports also say the BMS board is identical. Photos of BMS or cells might be useful.

So come on, peel back the damned duct tape and maybe end some of the mystery !

 

[StevenR]

I waited a bit - probably less than a minute - the first time the BMS cut out then I cycled power using the key switch and it came right back. It may reset by itself after some period of time but I put my key switch where I can reach it and just flip it on and off to reset. I try to test it (if I think of it) and intentionally trip it before I stop to take a break and just let it sit to see if it comes back without the power cycle routine.

 

[dnmun]

mr stevenr, if your BMS is allowing 60A and you were reading 2100 watts, then the average cell voltage is only 2.19V. you really should not allow any cell to drop below the 2.1V mark that everyone uses for cell reversal. i presume you have allowed the cells to balance so none of them are lower in capacity than the others, but if one cell does run low under your destructive testing regime, then it will be permanently damaged if current is forced out of it below 2.1V, and not really repairable. please don't blame mr ping if this happens since he did warn to set your CA to shut the controller down at 40A, and if you feel you need to modify the BMS to get even more current out, then learning how to do it on your own will provide enough knowledge that you may seek to protect your battery a little more.

rather than buy another 2 10Ah packs, why not just get another 48V20Ah pack and run the 2 in parallel, or maybe even in series with a stronger controller at 96V? that may get you over 50mph, closer to lowell.

 

[ZapPat]

couple of quick questions:

Does the BMS reset after over current by itself, after N seconds, or what ?

What markings are on the individual cells. It's about time we find out what entity makes the cells.
Ping isn't. Cammy isn't . Reports also say the BMS board is identical. Photos of BMS or cells might be useful.

So come on, peel back the damned duct tape and maybe end some of the mystery !

If you poke around there are a couple users that have opened up their ping packs and taken photos - one guy even made a duct tape repair pdf not too long ago.

 

[dogman dan]

Most of us have only peeled the top off. A few have done more to replace a bad cell, or more usually a mechanically damaged cell. I can't recall any pics that show the markings on the pouches. If you have one, please repost. That duct tape thead is a long one.

 

[StevenR]

mr stevenr, if your BMS is allowing 60A and you were reading 2100 watts, then the average cell voltage is only 2.19V. you really should not allow any cell to drop below the 2.1V mark that everyone uses for cell reversal. i presume you have allowed the cells to balance so none of them are lower in capacity than the others, but if one cell does run low under your destructive testing regime, then it will be permanently damaged if current is forced out of it below 2.1V, and not really repairable. please don't blame mr ping if this happens since he did warn to set your CA to shut the controller down at 40A, and if you feel you need to modify the BMS to get even more current out, then learning how to do it on your own will provide enough knowledge that you may seek to protect your battery a little more.

rather than buy another 2 10Ah packs, why not just get another 48V20Ah pack and run the 2 in parallel, or maybe even in series with a stronger controller at 96V? that may get you over 50mph, closer to lowell.

The peak current is 60A. This is only reached if I open the throttle too quickly at low speed and the BMS trips immediately. I am reading 40-45A at 2100W and the voltage reading is 46.5 or more (2.9V/cell or higher). I am relativly unconcerned about reduced battery life. If I only get a few hundred cycles out of it I will be more than satisfied. Note that I am also not one to abuse an item then try to take advantage of warrantee coverage. If I do these things and the battery is destroyed I will not hold Mr. Ping in ANY WAY responsible - I may be mad at myself but I will just order a 30 aH unit (from Ping). With that in mind, attached are pictures of the Ping BMS (sorry about the glare). Would this work like the Crystalyte controller such that if the shunt were soldered together it would increase the BMS trip point? The other option I am considering is just cutting the discharge ground wires on either side of the BMS and putting powerpoles on them so I can put a jumper across. If I did this would it charge normally or would I have to replace the jumper when I charged it?

I'm working on an email to Ping right now to ask several of these questions as well as to get prices on either two 10aH (if it is reasonable to parallel batteries of different capacities) or a split 20 aH battery. I am trying to put together options to be able to have 10 (although it's probably not enough for the 5303), 20, 30 and 40aH power options - with more to follow - 50, 60, 70...

 

[Pete]

With that in mind, attached are pictures of the Ping BMS (sorry about the glare). Would this work like the Crystalyte controller such that if the shunt were soldered together it would increase the BMS trip point? The other option I am considering is just cutting the discharge ground wires on either side of the BMS and putting powerpoles on them so I can put a jumper across. If I did this would it charge normally or would I have to replace the jumper when I charged it?

Yes. But when you exceed the C rating you may get enough voltage sag to trip the LVC. the BMS over current points are loosely matched to the batteries they are supplied with, to protect the battery from damage.

If you want to place the responsibility for discharge protection on circuitry other than the BMS, you can wire a separate negative wire direct to the battery negative. Then the BMS is being used purely for balancing during charging. Be aware that by bypassing the BMS for discharge you will loose not just the over current protection but also the cell level LVC protection.

As your pack ages (which by the sounds of it will happen rapidly ) and individual cell capacities start to vary you are in a position of destroying cells through over discharge. Controller level LVC protection can not monitor individual cell voltages and it is possible to undervolt a cell without the pack voltage getting to LVC.

For your application it might be worth considering either PSI cells, or at the very least spread the load across multiple parallel packs. You may end up getting 2 or 300 cycles when thrashing a single (modified BMS) battery vs 1000+ cycles from a pair of parallel batteries that are being used within their specification.

 

[fechter]

Would this work like the Crystalyte controller such that if the shunt were soldered together it would increase the BMS trip point? The other option I am considering is just cutting the discharge ground wires on either side of the BMS and putting powerpoles on them so I can put a jumper across. If I did this would it charge normally or would I have to replace the jumper when I charged it?

...

If you reduce the shunt resistance by soldering, that will certainly increase the trip current.
I don't think it will have any effect on charging. You might also be able to slow down the response so it won't trip on short peaks. Some people have had success with just putting a large capacitor across the output of the BMS.

It would probably be a bad idea to just bypass the BMS on discharge since you would lose the low voltage protection feature. The shunt/high current cutout circuit also functions as an electronic circuit breaker to protect the wiring against shorts.

If you increase the current too much, the FETs on the BMS might overheat or blow. If you can see numbers on them, it should be possible to estimate the safe limits. These could be upgraded as well.

The cells could puff up and rupture if the discharge current is allow to go too high for more than a second or so.

 

[StevenR]

Kinda moved the discussion to http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=6666 "Need input on people using 48V20aH with Crystalyte 5303" or something like that. This discussion seemed a bit off topic here. But for those looking at it here, I did wire the bypass. It seems to need to be reconnected to charge. Peaks went from 58.5A with BMS to 60A without. They appear to be transients on startup - I can't see them anywhere but peak hold on the CA.

In regards to the topic here, Ping ROCKS. That being said, I may try to win a lowball auction on some unknown eBay sellers (zero feedback from HK - it better go cheap). I'll keep everyone posted. Hey, SOMEBODY has to be an eBay sellers first sale or more guts than brains...

 

[dogman dan]

Just try to find one with prismatic cell packs. The eastjimmywu round cell ones have had some real problems.

 

[Fredo]

Just a quick update concerning my Cammy 48V/12Ah battery.
This is the initial plot:

After 10 cycles, still 9.2Ah so no real improvment and far from 12Ah. Seems that all the elements are quite well balanced. After a full charge, each one them are at 3.8V. After a full discharge, all of them are at around 2.7V with one at 2.5V. If I recharge only this one, another one reach 2.5V after 0.2Ah.

This is what you can see inside:

Not really clean assembly !

 

[swbluto]

Just try to find one with prismatic cell packs. The eastjimmywu round cell ones have had some real problems.

It seems cammy's has the "round cell ones" from the above picture. Oh well, we know where this is going. :lol: