Luna ga 14 ah shark pack

[teklektik]

Other than Luna only two (em3ev and lectric cycle) provided information on what type of cells were used and only em3ev specified configuration, all the others just stated the voltage and AH's.

Both also rated the packs according to the cell rating just like Luna.

Not at all.

EM3EV (a battery manufacturer) has banks of in-house cell testing rigs (I've seen their cell test, CNC, and die stamping equipment on a live video tour with Paul and Justin). For many years they have based their advertised battery capacity not on published manufacturer cell capacity, but rather on de-rated cell capacity from in-house tests - see below.

Typical Battery Specification:

• We use 14S (50.4V, based on 14*3.6V), not 13S (46.8V nominal, based on 13* 3.6V) like everybody else, so that means a working voltage of over 48V most of the time and it also means that you're getting that much more capacity than you would have had with an equivalent 13S Pack from somewhere else (7.7% extra versus a 13S equivalent). Our 14S NCM packs have very similar charge and discharge voltages to our 16S A123 packs.
  
  
• We conservatively rate the cells as 2.45Ah (25R), 2.10Ah (22P), 2.85Ah (29E) and 2.95Ah (30Q) and 3.15Ah (32E). Although the manufacturer classes them a little higher than this. Like with any Li Ion type battery, best long term performance is obtained by not using all of the available capacity all of the time.
  
  
• Energy Density of 150Whrs plus for finished pack.
  
  
• Cycle Life estimated at 500 cycles plus. Cycle life is extended by charging to 90% and limiting discharge to 90%. We make it easy to control the Charge voltage with our switching charger. To accurately limit discharge the Cycle Analyst is a great tool.
  
  
• PPTC thermal fuses used on all signal wires. If a fault were to ever occur on any of the small balance wires which run around the battery pack, the fuse simply shuts down the connection and keeps everything safe. Once the fault condition is removed, function returns to normal.
  
  
• Charge Voltage of 58.8V for 100% Charge, 57.4V for 90% Charge (our NCM chargers include a switch to charge to 100%, 90% and 50%).
  
  
• Maximum Charge Current 12A max (BMS limited).
  
  
• Whilst the 22P cell is 3C rated and can deliver 2C or more continuously, it is recommended not to run them at these levels on a routine basis. The 29E and 32E cells are 2C rated and we recommend a Max of closer to 1.5C. If your setup and usage means that the pack will be operated at high continous Current levels, consider the 25R or 30Q Packs which can deliver very high current levels without strain. Recommended Max Discharge Current: 22P pack - 30A, 29E Pack - 30A, 32E Pack - 35A, 25R Pack - 40A+, 30Q - 40A+. The 25R and 30Q Packs can easily delivery 40A continuous or more, but the packs are limited to 40A Continuous by the BMS, although the BMS can easily deliver much more for extended bursts.
  
  
• Dimensions: 75mm thick. 250mm long, 150mm wide.
  
  
• Weight: 4.9kg (22P and 25R), 5.2kg (29E, 32E and 30Q), not including charger or packaging.

Of course, EM3EV uses only authentic cells - no cheap knock-offs. This is a firm that has been innovating for us for many years and posting detailed specs with realistic ratings.

And, yes - I buy my batteries from EM3EV - I believe in patronage for companies that have a track record of developing and bringing new top-quality products to market - not just copying someone else's development efforts (e.g. triangle pack, 3-voltage charger)...

 

[RickM39]

We conservatively rate the cells as 2.45Ah (25R), 2.10Ah (22P), 2.85Ah (29E) and 2.95Ah (30Q) and 3.15Ah (32E). Although the manufacturer classes them a little higher than this. Like with any Li Ion type battery, best long term performance is obtained by not using all of the available capacity all of the time.

So, they rate the 2.5 at 2.45, the 2.2 at 2.1, the 2.9 at 2.85, and the 3.2 at 3.15. That meant the 12.8 AH pack became a 12.6 AH pack.

When I bought the GA pack from Luna it was advertised as 13.5 on the website at the time, so the 3.45 cells were discounted to 3.375.

Seems like Luna and EM3EV were doing the same thing, discounting the capacity slightly from the manufacturer's rating.

It would be great if we could keep this to a technical discussion about batteries and keep away from contentious feelings about other matters.

 

[broke]

Oops

 

[RickM39]

Mine is a 48v pack and it has never hit LVC.

On the longest ride I took so far the bike used 11.5 AH and the battery was getting soft, dropping below 40v at 6 amps or so. Still had a little left.

At that point it's probably time to quit unless you really have to keep going.

Here are some single cell results at a 1.5 amp discharge to 3.15 volts.

 

[RickM39]

I have seen tests of the GA and PF cells posted on flashlight sites that show the cells delivering energy much closer to the rating even at high discharge rates.

Either they had ringer cells or maybe something else is different about how we test.

When I raced 1/10 oval pan cars on a banked track we did a few things to make batteries perform.

The 2000 nicads were rated at a standard charge of 1/10 C but we charged at 3 C.Also there was a huge difference if the pack would finish just before the race and be warm from the charge vs sitting for awhile and cooling off.

The pack also needed to be completely discharged before starting the charge, then start the pack 40 minutes before your race.

One time the scoring computer quit and everyone kept repeaking their pack... I partially discharged mine at a high rate and timed the recharge right... everyone wondered why my car was much faster than theirs in that race.

The nimh's were even more sensitive, they wanted to be hot off the charger 135F to perform at their best.

Maybe we need to zap them like we did the nicads... still have the zapper.

 

[teklektik]

So, they rate the 2.5 at 2.45, the 2.2 at 2.1, the 2.9 at 2.85, and the 3.2 at 3.15. That meant the 12.8 AH pack became a 12.6 AH pack.

When I bought the GA pack from Luna it was advertised as 13.5 on the website at the time, so the 3.45 cells were discounted to 3.375.

Seems like Luna and EM3EV were doing the same thing, discounting the capacity slightly from the manufacturer's rating.

It would be great if we could keep this to a technical discussion about batteries and keep away from contentious feelings about other matters.

'Were?' New story?

You claimed the Luna packs are rated according to 'cell capacity' - that's 3.5Ah. A quick inspection shows that's how they're rated there today on the site - for instance 17.5 Ah 13s5p = 3.5Ah. I have no way of knowing what you saw or think you saw in the past. I gave a rundown of EM3EV policy of using plainly stated de-rated cell capacities - no math, no historical posts required - the way they always have done it and different than what appears today on the Luna site and what you stated.

This was about your claim - which is false.

No apologies here - if you find it 'contentious' that someone likes the detailed information and values the reputation of a different and long-established firm, well, get over it.

 

[RickM39]

Wow, seems like there's a lot more going on here than a 1.5% de rating!

Actually if you want to be perfectly accurate the GA's are rated 3.45 for a total of 13.8 for a 4p pack.

The OP was talking about significant missing capacity maybe 15%-20%?

If it was 1.5% either way the thread would not have started.

 

[broke]

Oops

 

[Gregory]

That sounds like a smooth move. They have already pretty much promised you one, might as well take them up on their offer.

 

[Hillhater]

Another ride today and my pack is charged at 11.30 ah from lvc to 58.8
What the heck am I loosing more power?
My last 2 charges have been less then 12 ah
.........

Broke.. I suspect ( with you collection od Ebikes) that you know full well a little about battery behaviour. ?
Why then do you keep posting irrelevent data like the above ?
LVC is not a measurement. Unless you measure and quote the actual starting voltage , the charged capacity means SFA !
Also , is that "LVC" caused by the pack BMS, or the controller LVC ?
And further, from the description of your riding techniques, you should realise GAs are the wrong cell type for your use !

Likewise Rick, i hope those capacity test you posted were just for comparative purposes (cell to cell), and not intended to suggest those cells were in some way not performing to spec ?
A 1.5A discharge to 3.15 v, is not representitive of any manufacturers test for capacity.

 

[broke]

Oops

 

[RickM39]

Rick, thanks for sharing your testing. fyi GA is rated at 3300mAh per the datasheet. Being an energy cell, it delivers markedly less capacity vs rated proportional to increased current.

The box that the GA's came in from Panasonic states "3450 mAh" so some inconsistency there. It also states a charge rate of 1/10 C so maybe that's part of it?

It is normal for batteries to increase IR as they discharge (I seem to remember learning about that as an EE major back when Nixon was president) but the nature of these is the IR goes up ALOT as they reach 20% left.

I'll do some more experimenting this week as time permits.

Broke, what was the voltage when the pack hit LVC? It seems that is at least part of the issue.

 

[999zip999]

Could be the way you are measuring ah ? Do you know how much you have taken out , like with a C.A. ? It seems you are measuring what's going in not what you are taking out ? Is this right ?
I mean what device ?
Please give starting voltage and end voltage at lvc.
Trying to get to the bottom of this.

 

[Alan B]

I suspect we are seeing the results of an undercharged pack that is out of balance.

Undercharging packs to "extend" their life often leads to unbalanced cell groups which reduce overall pack capacity. The BMS depends on full charge voltage to properly balance the pack. Once the pack is unbalanced the BMS's individual cell LVC will trip the pack off before the rest of the cells are discharged, and the total pack voltage not reaching the expected low value indicates this condition. Charging an unbalanced pack to full voltage then results in some cells being overcharged slightly while others are still undercharged, and until the BMS is able to rebalance the pack (which may take many recharge cycles), the pack voltage may appear to be near full but the pack's full capacity is not available until the pack is fully rebalanced.

Running a pack completely down is inconsistent with operating a pack for long service life. Pack capacity drops over time, and is also a function of temperature. For long service life a pack should be configured for at least 20% more capacity than is used. The last 10% of capacity is not very usable with increasing internal resistance and increasing voltage drop and cell heating.

We understand this pack is a 14S4P 18650GA cell pack. These cells, according to the spec sheet I found at NKON, have several capacity ratings under the manufacturer's specified test conditions:

Rated: 3300 mAH (13.2AH)
Typical: 3450 mAH (13.8AH)
Minimum: 3350 mAH (13.4AH)

So the pack could deliver a typical 13.8AH or a minimum of 13.4AH when it is new and balanced. Some packs will deliver even more, depending on test conditions and manufacturing variations.

It is very common for measurement instruments to have error, no assumptions about accuracy should be made. Instrument calibration should be verified.

I don't have the specifications on the actual BMS in the pack, but they typically require 4.15 to 4.20 V per cell to properly balance the cells. Undercharging defeats the balancing and allows cell groups to drift in state of charge and the pack's effective capacity will be reduced. Some cell groups will operate at higher voltages and some lower, those operating at higher voltages will suffer reduced life from higher voltage, and those at lower voltages will suffer reduced life from hitting LVC. A single charge to full voltage will not necessarily re-establish proper pack balance, it may take many full-voltage cycles to restore balance. Balancing only shaves off the cells that are high, it takes multiple cycles or continued charging to bring the low ones up. Running cell groups to the BMS LVC (which is a very low value like 2.5V) is likely to reduce their capacity further and thus cause greater imbalance and further reduction of pack overall capacity.

To optimally operate a pack at reduced voltages requires a BMS system designed to have adjustable balancing levels, which is not present on these packs. It also requires considerable excess capacity due to capacity reduction from low charge voltage as well as staying well above LVC at end of discharge. For best life the pack should also be rated to deliver considerably more than the peak load currents.

I have seen a high correlation with pack capacity loss from: running packs to low voltage cutoff, drawing too-high peak currents and operating the cell groups imbalanced (which can be caused by charging to less than full voltage).

An ideal charger for these simple-BMS protected packs should probably have only two levels. One for storage level (around 50-60%), and the other for full charge. For best pack life, never discharge below 20%, charge to storage level until you need it, and fully charge it just before use to let the BMS balancing work properly. If a pack is stored for an extended time, periodically charge it fully and discharge it back to storage level to exercise the cells and allow the BMS to do the balancing.

I would also like to see battery pack manufacturers bring out a connector with individual cell group voltages so we could measure them and apply external balancing when needed to lengthen the life of the pack and understand the true status.

 

[broke]

The pack is being charged to 58.8 with a satiator. And has been left over night on the charger a couple time pack is new less then 20 charges.

 

[RickM39]

We understand this pack is a 14S4P 18650GA cell pack. These cells, according to the spec sheet I found at NKON, have several capacity ratings under the manufacturer's specified test conditions:

Rated: 3300 mAH (13.2AH)
Typical: 3450 mAH (13.8AH)
Minimum: 3350 mAH (13.4AH)

Do you know what the manufacturers specified test conditions are, such as at what current? I've not seen that spelled out anywhere.

I do beat the heck out of the pack climbing my local down hill track then bombing down. Then A little wheelie practice tell I hit the lvc.

Could it be that hitting the pack hard when nearly discharged could explain the LVC?

When my 48v pack is approaching 41v or so I feather the throttle to keep the voltage from dropping too low.

 

[Green Machine]

I figured ~12.7Ah, the OP got 12.5Ah. The LVC has been confirmed at near 100% DOD also.

The OP is saying he is getting 12.5 ah and his low voltage cut off on a 52v is 46v...... the lvc should be 38v so obviously something is not right here either in testing equipment or maybe the bms is cutting off to early so the bms may have a problem.

12.5ah and the pack is at 46v sounds awesome to me..... just the question is why is the lvc cutting off at 46v

SO how you ssay the LVC has been confirmed to be 100 percent DOD i don't know. Nothing has been proven here.... just a bunch of conjecture and dealers with hidden identities blowing up smoke clouds.

 

[broke]

Oops

 

[999zip999]

NO I wound not use lvc on the bms as the rule. Over time this practice can unbalance a pack. You don't drive your car till dry, then fill up. Then try putting it on the charger for overnight light discharge more time on charger. This may balance the pack. I more concern of lvc cutoff of 46 volts.
I always have a set of sense wires bms or not. This will tell state of charge at cell level ez. Is one cell group low tripping bms. May going up steep hills at end of charge. Maybe once or twrice. You would have to check cell voltage at cutoff to see which cell is tripping the bms. Sounds like work. Like.
1. 4.15v
2. 4.09v
3. 3.95v

13. Xxx volts
State of charge.

 

[broke]

Oops

 

[broke]

Oops

 

[Hillhater]

The pack at 46v resting voltage, is not fully discharged.
That represents 3.28v* per cell which by consulting the discharge graph, means the cell has discharged 3.0 Ahr almost exactly....12Ahr for the whole pack if perfectly balanced.!
Either the LCV is set wrong ( can we confirm this is not a controller setting confusing things ?)..or the OP is hitting the pack too hard near the end of discharge. Effectively these are 2C discharge rated cells with heavy voltage sag.
Either way, I will say this again ..GA cells are the wrong choice for the OPs stated riding style !
(* EDIT .typo correction 3.18v to 3.28v)

 

[Alan B]

I think the battery is sagging really bad at low voltage I don't check voltage until I get home. And it's around 46v to 45.9v at lvc I haven't been able to get 12 ah into the pack the last couple of charges. It's been low 11s ah. 11.4 ah and 11.3 ah.

If the pack is bouncing back to 46v is it safe to just run the pack down to lvc everytime? That way I will know when the battery is done?

Running a pack to BMS LVC every cycle is a sure way to reduce pack life. BMS low and high shutoff values are designed for emergency protection, not normal use. Apparently the LVC on this BMS should be 38V or about 2.71V per cell group.

This behavior is consistent with a severely out of balance pack. One cell group is at the LVC of about 2.71V and the rest are at 3.33V for a total pack voltage of 46V. The already weak cell group is being repeatedly rammed to LVC, which is likely to cause further reduction in capacity.

The pack needs either a full balancing (at a minimum), or the replacement of the weak cell or group, if it is damaged. One cell operating at significantly reduced capacity would be sufficient to cause this pack behavior.

 

[fechter]

If you read a bunch of datasheets for high quality Li-ion batteries like LG and Panasonic, you'll see the industry standard discharge rate for determining capacity is 0.1-0.2C or so. This is to make apples to apples comparisons. At higher rates, all batteries will have less capacity. They have graphs of this in the datasheets so you can estimate performance in the actual application.
At higher rates, you also have more sag so will hit the LVC earlier, further reducing capacity. This is normal and all batteries do this to some extent. Take some "10Ahr" lead-acid batteries and run them at 20A discharge and see how much you get. It will be less than half the rating.
My point is this is normal industry standard stuff. Same thing goes for battery voltages. A 48V battery is rarely at 48V.

 

[999zip999]

Zip says Stop discharging the pack to lvc. Ok. Leave on the charger after light turns green. Give it time for the bms to bleed down the high cells. To know state of charge you need to find cell voltage and write it down to share with us the state of charge it looks like these.
1. 4.19v
2. 3.88v
3. 4.25v

13. Xxx
If you share with us it will tell us state of charge.
Do these at hvc and find the high cell 1 thru 13 ez.