Battery issue and questions

JTL said:

I believe Karl posted something a while back about using the battery charging wires to run other DC things like lights. I think he was referencing Anderson connectors or something similar. I wonder if I could do the same thing with a barrel connector providing I maintain the correct polarity? If I can, could I also check the remaining power using my multi tester and a barrel connector with bare wires. Is the charging port just an extension of the main drain port?

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dogman dan said:

47 volts under load? Or not under load? What is your load? That could be normal for a 40 amps controller and a big hill, for it to sag from 47v to 42v.

If you cut any wires on that battery, most vendors would say that ended any kind of warranty support.

Why would you attach a discharge to the charge port? just make a y cable that plugs into your discharge plug to run 48v lights and stuff.

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eTrike said:

Hi. Sorry to hear of your troubles. Luna Cycle has a history of poor support for their battery issues. It sounds like this is the case here again. If you purchased it very recently their warranty period may still be in effect. I'm curious how you're getting your voltage readings?

It certainly sounds like a battery issue-- not the charger. I would suspect the BMS is stopping the discharge as one group hits LVC, indicating an issue of either cell group or BMS.

A "52V" Luna pack is 14S, so for NCRB cells a 42V cutoff might be appropriate to account for sag. If your voltage measurement is taken with a multimeter after the pack has cut out, the OCV (open circuit voltage) might be ~46V. Your reading of 47.5V is feasible if the pack is cold, but if the lowest it goes during use (under load) is 47.5V, then the issue is a cell group or BMS.

The charging port should work as you describe, but it taps into the BMS so current limits must be observed (usually 15A for BMS or ~5-10A depending on barrel plug).

Hope this helps!

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Ykick said:

Where (roughly) are you located?

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Nelson37 said:

The ideal way to troubleshoot this would be with a wattmeter continuously connected to the system so that available power under load can be determined.

Another piece of info that might shed some light on the issue would be How far, on flat ground, and at what speed, can you ride before the battery cuts out? Also, how much do you weigh, and how much do you pedal?

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Nelson37 said:

The voltage a battery displays under no load, and what it displays with a load, will be different and can be dramatically different. Like from 48V to 42V, 42V being a likely cutoff for the BMS. It is similar to "how fast can you run, and how fast can you run while carrying a refrigerator?" Drop the fridge, and you can run faster again, right? Remove the load, and the battery will likely spring right back up to 48V, until you load it again.

The question about actual range may very well provide useful information towards solving your problem. If that is not your main goal, that is your choice.

Based on extensive reading and a heavy diagnostic backround, it is IMO Extremely Unlikely that a BMS with an LVC set too high is the problem. A defective cell causing extreme sag WHILE UNDER LOAD is highly likely. Your symptoms correlate well with numerous examples of this problem.

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eTrike said:

Hi again. You're most welcome. Sorry to hear its been over 30 days (no exchange for another pack) but the good news is the warranty should be 90 days for a replacement if needed. Did I understand correctly that the pack ships with bare wires? Do you have the color display or some way to check voltage or watts under load?

The support info you received sounds like Eric from Luna Cycle or someone who was trained by him as they aren't fully comprehending your issue as you noted with the charger. As you may have been coached, it can be tricky to share details in a public forum as Eric has previously used this as a reason to provide less support. I would not have recommended sharing your location due to this, but anyway it is quite odd that they say it needs 5-10 charges to balance when new. The #2 option they gave repeats what we've shared and is a likely scenario. Let's check some numbers...

The NCRB cells are pretty much empty near 3.3Voc/cell, and dead near 3.2Voc/cell. Under a 20A load your pack might fall ~6V under load, so your reported numbers are in keeping with the performance of these cells if the LVC is set at 42V. Lowering your LVC to 38-39V will allow for extra sag but is not recommended as cell differences would be exacerbated and the BMS will have a hard time correcting the increased imbalance, leading to further degradation of the weakest cells if this cycle is repeated. You can manually taper your power towards the end of your discharge if you really have to, but consider this a reserve as this is sub-optimal-- it would be preferable to recharge at this point for the sake of your cells.

These NCRB cells are a poor match to anything over 20A (5A/cell). The GA packs fare better but is still a poor match for a BBSHD when used at full potential. We've seen a handful of users report similar problems with Luna Cycle GA packs here.

Hope this helps!

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JTL said:

eTrike said:

Hi again. You're most welcome. Sorry to hear its been over 30 days (no exchange for another pack) but the good news is the warranty should be 90 days for a replacement if needed. Did I understand correctly that the pack ships with bare wires? Do you have the color display or some way to check voltage or watts under load?

The support info you received sounds like Eric from Luna Cycle or someone who was trained by him as they aren't fully comprehending your issue as you noted with the charger. As you may have been coached, it can be tricky to share details in a public forum as Eric has previously used this as a reason to provide less support. I would not have recommended sharing your location due to this, but anyway it is quite odd that they say it needs 5-10 charges to balance when new. The #2 option they gave repeats what we've shared and is a likely scenario. Let's check some numbers...

The NCRB cells are pretty much empty near 3.3Voc/cell, and dead near 3.2Voc/cell. Under a 20A load your pack might fall ~6V under load, so your reported numbers are in keeping with the performance of these cells if the LVC is set at 42V. Lowering your LVC to 38-39V will allow for extra sag but is not recommended as cell differences would be exacerbated and the BMS will have a hard time correcting the increased imbalance, leading to further degradation of the weakest cells if this cycle is repeated. You can manually taper your power towards the end of your discharge if you really have to, but consider this a reserve as this is sub-optimal-- it would be preferable to recharge at this point for the sake of your cells.

These NCRB cells are a poor match to anything over 20A (5A/cell). The GA packs fare better but is still a poor match for a BBSHD when used at full potential. We've seen a handful of users report similar problems with Luna Cycle GA packs here.

Hope this helps!

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Nelson37 said:

JTL - The question of roughly how far at what average speed you get before the pack dies is important diagnostic information which can give a rough estimate of what watt-hours you are getting from the pack, and point to whether, or not, it is truly defective. Short of a wattmeter or voltage check under load, which requires additional equipment or wiring, this is currently the most important piece of information you can currently supply.

This will make the third request. If there is some good reason for failing to supply this information, please inform so that I can contemplate it in great amazement.

The very low LVC you were given may be just a temporary measure to take the controller out of the equation as possible source of the cutoff, but may be in the dangerously low range if the BMS is actually malfunctioning in some way, and again, IMO, this is something that you definitely should have been informed about by the vendor.

How Far, Damnit?

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eTrike said:

The GA packs fare better but is still a poor match for a BBSHD when used at full potential.

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eTrike said:

JTL said:

... it seems like most people producing batteries are not making a 52v size, not sure why. How important is 52v?

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52V is a 14S battery, 48V is typically a 13S battery. You'll get slightly more(~7%) speed and range with the larger battery.
The reason you don't see more is because 52V is a marketing gimmick from Luna Cycle. It is a 14S battery which when marketed honestly should be considered 50.4V (3.6V nominal x14). em3ev markets a 14S as 50V fwiw. I'd imagine more sellers will start to market 52V (3.7V nominal) so potential customers aren't confused and misled by the gimmick.

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eTrike said:

JTL said:

Based on the nominal 3.6 v isn't a 48v really 46.8? I thought I read that nominal voltage is 3.7v. I am on a slow learning curve. I am basically down to two vendors, EM3ev who was very helpful in the past when I was deciding between a hub motor and a middrive and California Ebikes which I know nothing about. They both have a Dolphin style pack at 48v and it has Sanyo 30Q cells,11.8ah 3C. It might fit in my frame. Not so much AH as what I had. I could get 22p cells with some higher AH in a rectangle pack. Have no idea what 22p means. Any thoughts.

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Yep, you'll see that 46.8V number on 13S em3ev packs. A few cells are 3.7V nominal but most are not. I don't know much about Cali ebike batteries, but em3ev batteries are over-engineered imo-- quality build with solid cell connections and loads of safety features as you can read in their descriptions, the like of which you won't find elsewhere outside of automotive packs.
Further, em3ev has a much smaller markup than Luna Cycle packs, so are a great 'bang for your buck'.
(fwiw dissecting Luna Cycle packs reveals a number of QC issues-- typical of average China-built quality, likewise with their charger-- the cells are legit however and the shortcomings can be improved by a competent end user)

30Q is a great cell and does surprisingly well under high loads and temperatures. 22P is a good high power cell from Samsung. The Ah might be closer than you think-- a 14Ah GA pack from Luna Cycle is closer to 12.5Ah in practice. As you can read on their site, em3ev de-rates their cells to give a closer approximation of real-world use.

A "48V" pack is a hold-over from the days of lead-acid nomenclature, excepting when it is a 16S LiFePO4 pack (which is essentially the same voltage as lead-acid). 36V and 72V batteries are less confusing (10S*3.6V=36V), but similar marketing exists with tool packs (DeWalt 36V is max voltage, not nominal). As long as you know what you're looking at it is easy to discern and equate, but the learning curve can be somewhat steep.

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eTrike said:

Nice-- it sounds like you're getting a refund from Luna, which is an exceptional level of service besting their written warranty statement and previous service examples, good for them and you!
Any of those packs will work a treat. I'm partial to the 25R but the 30Q is excellent as well. 22P is your least expensive option (comparing $/Wh) and has proven to be a very reliable cell.

You can get some idea how they perform under load on lygte-info.dk comparator: http://lygte-info.dk/review/batteries2012/Common18650comparator.php
Note that this does not factor longevity or other potentially important factors-- even laptop cells like 26F look decent on that comparator. It is worth noting the cliff edges under the lowest 0.2A draw to approximate open circuit voltage limits-- you'll see that cells like 25R and Sanyo GA have LVC cliffs near 3.4V, below which the cells have 10-15% remaining. It is best to avoid this lower capacity for the sake of longevity and deduct it from your comparisons to determine your optimized relative capacity.
For example, you'll note that 22P drops like a rock after 3.4V. This means you can use more of the stated capacity without increasing the risk of cell failure. 30Q has a more gradual cliff steeper after 3.4V but is reasonable down to 3.1V.

Using this info for the 25R, I used a pack tested @80% DOD cycled between 4.1-3.4V. If you need more range you can always charge to full before riding, but try to the lower 10% if possible. There is a 25R cycle life test on the forum somewhere...

Cheers!

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