Luna charger / battery issue

Hi - I'd appreciate some advice...

I have the following battery and charger from Lunacycles.

- 52v Samsung INR18650-25r 20ah
- Luna Charger 52v Advanced 300w Ebike Charger

The charger will not charge the battery to it's maximum 58.8v as it used to.

It seems to only charge to 57.4v and then it cuts off. The readout on the charger then shows 58.8v (I assume this is why it will not put more power into the battery as it thinks the battery is at maximum charge) but in reality the battery is only charged to 57.4v as evidenced by it's built in screen and via Cycle Analyst.

Is the battery faulty or is it the charger? Hoping the charger

Thanks

It could be the charger, or the BMS cutting off. I would put the charger as the more likely of the two. (update - in rereading the posting above it was indicated that it "used to" charge to the full value, and that it "pops to the full value when it cuts out now". This may indicate the BMS is stopping the charge, which it would do if a cell group was rising to the value that triggers this behavior in the BMS)

It would be easiest to try another charger first, if you have one available or can borrow or obtain one. If it exhibits the same behavior then the battery becomes the likely issue.

Some chargers have switches that adjust the endpoint voltage. If your charger has a switch it could be in a different position than before.

Most chargers are not designed for vibration or moisture resistance, carrying the charger on the bike, or encountering humidity or being dropped may result in problems. There is usually an adjustment internally using a low cost variable resistor that is not resistant to moisture/vibration. It doesn't take much to cause a shift such as this. Components may drift with time.

The electronics in the charger is also subject to line transients which can be very high voltage spikes and may cause damage. This is generally a total failure rather than a small voltage shift however.

It is good to have a spare charger, with two you can compare them to help pinpoint problems, and you have a backup in case of a failure. My experience with ebikes has been that chargers are the most failure prone item in the system.

The programmable Satiator charger from Ebikes.ca is a good one, it is potted for vibration and moisture resistance, and adjustable so it can handle a wide range of batteries, charging rates and end of charge states, as well as having UL ratings for safety. Unfortunately this comes at a price (which is understandable) but may not fit the budget.

OK thanks. The charger has a switch that enables charge to 80/90/100% but it doesnt seem to do anything! It used to work so I think maybe you are right about some sort of damage.

I had the same situation with a luna charger and they replaced it for me,

Although it seems annoying you are probably better off undercharging by 1.4 volts anyway to preserve battery life span, that top volt comes off pretty quick as soon as you ride anyway.

I have gone to a Satiator as my main charger, along with all the features the best one for me is silence, no more fan noise,

Keep your eye out for a cheap 2amp charger of proper end voltage. Always check new charger with volt meter or multi meter for polarity also before plugging in to battery. Always always check with multimeter as China doesn't always follow the red and black rule.

Eventually, the battery may need to be top balanced. Depending on the consistency of each string, it could be months. If they are rock solid, with no deep discharges, years. :lol:

I'd start by inspecting/testing the 3 position charge level switch. It might be fine but it's probably really easy/cheap to replace, and your symptoms kind of match what a failure in that switch would cause.

If need to turn the screw for adjustment I make a screwdriver out of a chopstick or a piece of plastic . But always check twrice and small adjust if needed.

Contact Luna and see what they say. They could most likely offer you a replacement charger. It could be the BMS cutting off also, which could explain why the charger goes to 58.8 when the battery disconnects. This would be harder to troubleshoot, so trying another charger is the easiest first step.

Could be a bad parallel group racing to over voltage before the other groups. To test for this without cutting it open, If you just let it sit on the charger for a day or two it should slowly top balance and the voltage will slowly increase and the charger will cycle on for a few minutes every once in a while. How quickly depends on the discharge rate of the balance circuity. If that is the case, your battery is close to the end of its life and will require replacement of the problem cells.

Thanks for all your replies and help. I think I'll try a new Luna charger first.

If the pack needs fixing does anyone know of anyone in the UK that can do this? I can't really send it to US especially with all the restrictions now with batteries on planes.

How many cycles do you have on it. How is the capacity ? Ah ? Maybe a few light cycles with time on the chrarger ?

I have the same issue, and I don't think it's your battery. I have 2 Luna Energizers, and the first one measures 58.68V (the one with the burned out display), and the second one measures 58.4 (I confirmed it with my Fluke multimeter). When I charged one of my batteries with the 2nd charger, it stopped charging at about 58V. I then plugged the battery into the other charger, and the fan turned on, and it continued to charge it about a half volt higher. I'm about to open it up to see if there's an adjustment inside. Does anyone know?

And does anyone know if charging to a slightly lower voltage will affect any of the functions of the BMS such as balancing? If charging to 58V isn't that big of an issue, maybe I'll just leave it alone. I wonder what voltage the balancing starts at.

Another interesting thing to note is that there seem to be 3 versions of this charger. Notice how one is longer than the other. The 1st version had a 2-position current switch and a 3-position voltage switch. The 2nd version had a 5-position current switch and a 2-position voltage switch. The current version seems to have a 5-position current switch and a 3-position voltage switch.

I wish they would add a 4th position (or change one of them to 40%) for a 40% charge for storage. I only use my battery once a week or less, so I like to keep it at 40% until I need to use it. I wonder if it can be done easily at home. Anyone know? Can I just add a resistor to one of the terminals on the switch? Right now I just use a voltage booster on a 12V AC adapter to charge it to 40% but it is super slow (takes a day, but I guess it's ok). Here's a link to the voltage booster. They have a new 900W model that looks interesting. I wonder if it can be used as a charger (5A all the way until the cutoff voltage).

https://smile.amazon.com/gp/product/B00E8D7XYG/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

I'm also thinking about buying one of these $20 52V chargers to play with. Maybe I can set the voltage to attain a 40% charge.

http://www.ebay.com/itm/58-8V-3A-Charger-for-48V-14-CELLS-Li-ion-Battery-Pack-AC110V/172591619867?_trksid=p2047675.c100011.m1850&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D42818%26meid%3D8b82040089ef4df68cba5ab74901675c%26pid%3D100011%26rk%3D1%26rkt%3D11%26sd%3D201279247330

giblet said:

Hi - I'd appreciate some advice...

I have the following battery and charger from Lunacycles.

- 52v Samsung INR18650-25r 20ah
- Luna Charger 52v Advanced 300w Ebike Charger

The charger will not charge the battery to it's maximum 58.8v as it used to.

It seems to only charge to 57.4v and then it cuts off. The readout on the charger then shows 58.8v (I assume this is why it will not put more power into the battery as it thinks the battery is at maximum charge) but in reality the battery is only charged to 57.4v as evidenced by it's built in screen and via Cycle Analyst.

Is the battery faulty or is it the charger? Hoping the charger

Thanks

Click to expand...

Ooh, looks like you can adjust it. I think I'm going to dive inside and set it so that the fan turns off when the voltage is 58.8V.

https://endless-sphere.com/forums/viewtopic.php?f=2&t=75672&start=25#p1187432

The balance function is solely in the BMS and to what the BMS is set to thru each sense wire. I haven't test a bms in such a way. I believe each cell is balance to a slightly different voltage but to end up to the final voltage. Meaning its how the bms balance circuits are set to. Setting a bms to a lower number is hard because a lower number at voltage can be a big difference in capacity. Or voltage is not the same as capacity as a linear number. It's easier to balance at full volume. Just my opinion not based in fact.

I'm not sure I understand what you're saying, but my understanding of a BMS is that it monitors each group of cells and will not allow any to go above 4.20V. This way, once the pack is charged, all the groups are at the same voltage, but it cannot do this until all the groups reach 4.20V, or one or more groups will not be at the same voltage. This is why I want to charge to 58.8V (4.20V/cell).

999zip999 said:

The balance function is solely in the BMS and to what the BMS is set to thru each sense wire. I haven't test a bms in such a way. I believe each cell is balance to a slightly different voltage but to end up to the final voltage. Meaning its how the bms balance circuits are set to. Setting a bms to a lower number is hard because a lower number at voltage can be a big difference in capacity. Or voltage is not the same as capacity as a linear number. It's easier to balance at full volume. Just my opinion not based in fact.

Click to expand...

Yes the charger needs to be high enough for bms to bleed down each cell group.

Finally got another charger from Luna (this time I got the 220v European version with 5 position switch version, 1 - 5amp output and 80/100% switch) - charged my battery at 100% and it went to 57.4v again and cut off.

So I guess it's not the charger.

It would seem that each of 14s cells in the pack are charging to 4.1v.

1) Is there anything to worry about? I mean I know will prolong the life of the pack not charging to 100% anyway but should I be worried that the cells might be going bad?
2) How much range would I be losing from the full charge to 58.8v? (I have a Tangent 3kw motor)
3) Can I use the Cycle Analyst to check anything suspicious and if so what screen should I be looking at when I'm riding - the bike seems to pull to 3000w when needed (not often) and I get loads of power all the way through the discharge cycle.

I guess my only option is to rip open the pack and test the BMS and see what each series of cells is measuring. Is this dangerous?

I'm a complete noob so sorry if I sound stupid.

Charging to 4.1v will give you roughly 80% of the potential capacity. Normally this won't hurt anything and will prolong the life of the batteries and minimize the potential for fire. At this voltage, balancing won't happen. Eventually this may become an issue, but healthy cells tend to stay in balance for a long time.

From the observations, I'd guess both chargers are just set a little low. It doesn't really sound like a BMS problem. It might be worth cracking open a charger to see if there is an easy way to adjust it.

Well last night I charged the battery as full as I could - on the charger it read 58.4v, on the battery the display read 57.6v. On the bike the CA read 57.4v.... haven't got a multimeter so I can't actually test it properly.

If I got a decent charger would that be able to restore the battery and balance it?

If so what charger?

Thanks in advance

Without an accurate meter it is hard to know which, if any of those values is right. The CA can be calibrated. The meters on low cost chargers are not always exact and are not generally set up to be adjusted that I know of.

If the BMS is stopping the charge then at least one cell group is reaching a voltage higher than 4.20. Depending on the BMS this could be something like 4.25 or 4.30. Each time the battery is recharged the BMS will bleed the high cell group. Cycling the battery may improve the balance and allow it to fully charge again, but this can be a slow improvement process, especially if the battery is not used and recharged frequently.

BMS's work best when batteries are charged and discharged a lot. When a battery sits the BMS can't do much, and they draw a tiny little current from the pack. Batteries that sit a lot can't be balanced by the BMS. Balancing occurs during the last part of the charge cycle and after charging completes for a while.

Some chargers continue to output voltage after the charger indicates "charge complete" so the BMS can restart the charge cycle repeatedly as it bleeds down the high group to bring up the low groups to restore balance more quickly.

Since this battery is not behaving normally it is especially prudent to watch it during charging and take precautions to insure that if it does fail to flames that it not catch anything nearby on fire or damage anything with the smoke.

The only way to know the state of charge is to check each cell group I would write down like this.
1. 4.09
2. 4.19
3. 4.15

14. Xxx volt
What I was saying earlier how do you know at what voltage each cell group shuts off at. As opposed to a group shutting off the bms. Good to get to the bottom of this.

How's the investigation going? I really think you should open up the charger and adjust the potentiometer. I just did this today to both of my Luna chargers, and they're charging to whatever voltage I set it at. I don't think there's anything wrong with your battery. It's just that every charger is calibrated differently, and yours maybe set too low.

giblet said:

Finally got another charger from Luna (this time I got the 220v European version with 5 position switch version, 1 - 5amp output and 80/100% switch) - charged my battery at 100% and it went to 57.4v again and cut off.

So I guess it's not the charger...

...I guess my only option is to rip open the pack and test the BMS...

Click to expand...