First eBike Conversion Questions...

DMLPDX

Member
Hey all,

Don't know how to ask this question other than to describe a problem I'm having. I have a Trek 8.6 DS that I just converted with a Bafang BBS02 750w + LunaCycle "shark pack" 52V 11.5 ah with a C965 display.

I'm still tweaking things but overall have been impressed with the build. I live in Portland and so I do have some hills to traverse in my daily commute. They're not huge hills more like steady grade.

Today, I was on my way home and on a very modest grade in PAS. I'm still fine tuning the rear derailleur so I was pedaling maybe the 3rd or 4th (of 9) gear on the spool. I've been noticing that the display shows battery level, but when under load, it seems to show more the load on the system, so if I'm going up any grade I tend to notice the battery indicator showing drain...maybe drawing from 100% to 20-40% occasionally. But today the battery seemed to draw down to the lowest level, then showed no level, the battery display started flashing, then the mid-drive stopped assisting and basically began to spin. I was able to correct the problem by reboot (turn off, then back on).

Obviously, the motor or the battery or both were overloaded...but I'm not sure I should be expecting this.

Any explanations?

PDX Dave
 

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Adrian

Active Member
Sounds like the battery can't supply the current demanded and the voltage sagged to a point below the low voltage cut off.

It's the reason you should get high power battery cells - like 25R - with these 750w BBS motors as they will actually draw way more than that under load.

I've no idea what cells you have in that pack but you can reduce load by putting on a smaller chainring (Lekkie for instance) and/or changing gear to a more suitable one - 1st or 2nd.
 

George S.

Well-Known Member
You would want to be in a gear that allows the motor to turn without any bogging down. But you said a mild slope. The voltage is dropping as you try to get more current, but it's probably a low wattage.

It could be a loose connection that gradually fails as you try to pass current through it. Bad connections tend to get hot. You might try drawing power just with the throttle. It could be a glitch in the assist.

Not sure if this is intermittent or a constant pattern. As the current increases, the voltage drops every time or just sometimes? The lights going out are a voltage drop. No lights is a huge drop.

I'm sure Eric will resolve the issue. Maybe you can pin it down a little so he knows what to swap . Luna sells a little meter that shows amps and volts. The meter makes things more precise, like "at 6 amps the voltage drops from 50 to 44."
 

flymeaway

Well-Known Member
Any explanations?
C965 displays watts. What is it indicating on the hill climb? I have the 750W BBS02 and am using a no-name 15AH 48V brick. I have some fairly steep grades to climb over some distance and haven't experienced any battery issues. In fact, until recently when I was riding in 26 degree weather, I'd never seen the indicator come off full, the C965 beeped and it dropped one bar. I chuckled.......

One other question, have you felt the motor when this happens to see if it's very hot? If the motor is carrying an excessive load, or the voltage is too low, the motor will heat up quickly.

Court J.
 

DMLPDX

Member
Hey guys,

Thanks for all your thoughts. I just completed the conversion over the weekend so I have not really had enough experience with the system as I've only driven it twice.

Here are the specs for the battery. Adrian, this is by all accounts a very high quality Panasonic battery pack. It is 52V 11.5 ah.

There could be a loose connection between the battery pack and wiring harness. I have a crimped tube connector with shrink wrap. It is enclosed in a plastic conduit tube. I am confident it's fairly water tight. But, it was raining quite heavily at the time. I have not had an opportunity to put fenders on quite yet. I was too anxious to try the system out.

George, on any moderate climb the C965 shows drain on watts fairly consistently. Again, haven't driven enough to know for sure if it's all the time, but my sense is, it is. I have no throttle on this setup as yet, just PAS.

Flymeaway, on a hill climb it will drop from 5 to 2-3 bars, but when load decreases (and current) it restores to previous setting. I have not checked the motor to see how hot, but as I work through these problems, I will do so.

Thoughts?
 

George S.

Well-Known Member
I have the 48v version of that pack with the high capacity cells. You have the performance cells. No way that pack lacks the ability to deliver amps.

You could try leaving the pack on the charger overnight. If you have the fancy charger, leave it on the lowest switch setting, the 100% charge setting. The idea would be to balance the cells.

I'd try riding with no water, just to see if there are any chinks in the waterproofing. Bad year for dry rides in the Pac NW.

Watch the watts, see what you're getting. No throttle means no chance you've messed up the controller. I've hit 1300 watts. The 48 volt system gives a lot of extra power versus my older 36v. MAC hub.
 

DMLPDX

Member
Thanks again George.

I purchased an upgraded my charger when I ordered the shark pack after reading what Eric had to say about charging batteries and how to prolong their life. This charger will allow me to charge at a high rate (5 amps) or a low rate (3 amps) and to what capacity (80, 90, or 100%).

I'll play with it a bit...see what happens.

Maybe Eric will pipe in a bit. I've emailed him about this but haven't heard back - probably off on holiday.

David
 

Adrian

Active Member
Hi David, as George said, those cells should be able to provide the needed current if everything is okay with the pack.

On my 750W bbs02, I have high power cells too and I also see the battery showing drain when going up steep hills - the battery can show full and drop a bar and then show full again once the load is removed - so I think that is completely normal. But, you said the drain on yours went to the point that the motor cut out which isn't normal unless the battery is fairly flat to begin with. George's idea of leaving it on the charger to balance was a good one.

As for weather proofing the battery-motor connection, I used liquid paint as well as shrink wrap and it has survived winter snow, ice and slush as well as torrential rain in the "summer".
 

JoePah

Well-Known Member
you can do some basic troubleshooting on that battery pack. I suspect it either has a defective cell or something with that BMS.

When your motor cut out, what was the state of charge, or battery level just before you started climbing the hill? If it was already less than 40%, then it might be voltage sag is hitting the BMS cutoff.. And that is not good for you for a new battery.

After the battery pack is fully charged, measure the voltage with a volt meter. It should read at least 58.8 volts http://lunacycle.com

If it charges fully, and you're seeing a lot of voltage sag under load, that points to a defective cell... The only way to troubleshoot that is by installing a voltmeter on your bike and watching it as your ride up the hill.. For a new battery under warranty I dont think you should have to incur that expense.
 

RoyL

Active Member
Could possibly be a bad cell somewhere in the pack. I have a similar set-up and do notice a drop of a couple of bars going up a steep hill, but in no way should your motor cut out on a gradual incline. Could you get your hands on a replacement battery to try?
 

DMLPDX

Member
George I went ahead and charged to 100%. I have relatives in town so I haven't had much time to dicker with the bike but I snuck out while grilling dinner tonight and with the 52T sprocket and rear derailleur in 3rd (still haven't found time to adjust) ironically I went up a steep grade out front of my house and the watt meter didn't flinch and in dry conditions.

As soon as possible I will get the rear derailleur adjusted, get the fenders on, and see if I can replicate. And I will get a voltage meter to ck.

David
 

George S.

Well-Known Member
I'm glad it doesn't appear to be the battery or the BMS. In the early testing, it helps to make sure the motor isn't getting hot, just to protect it. People are upgrading the BBBS 02 and HD to different chain rings, like the Bling Ring, which make it easier to align things, from what people report. They are usually a 42T. The 52T is something where you would want to watch the temps. Not great for hills. Karl at Electricfatbike.com has tons of info on the 02, like how to install a temp gauge, lots of stuff on optimizing the motor.

I like Adrian's suggestion on the liquid paint. A lot of people use silicon, but the Liquid Paint can be applied with a brush, comes in black, and lets you stay fairly neat doing lines. Plus it comes off if you want to remove it.

Hopefully you get some dry weather to do some testing, tweak the bike, and then figure out the water proofing, if necessary. I don't really know how waterproof the battery cases are. Not sure if water can get between the battery and the mount.

Some people have suggested that a full charge every now and then is a good idea to complete balancing the cells. The first time I did the 100% charge it reached the final charge voltage (about 54.5v) and continued to charge for a couple of hours. I get pretty good dips in the voltage when drawing a lot of amps. Still trying to figure out what is 'normal' really. Next I'll try to run my battery down, see how that looks/works.
 

DMLPDX

Member
George/Adrian,

Get out of my head :). I was just about to ask that question re: Liquid Tape!

So, the upgraded LunaCycle charger displays a continuous voltage while charging and apparently upon completion. Is that as accurate as a voltmeter?

David
 

George S.

Well-Known Member
David,

Most paint does tend to be liquid. I tried Googling 'liquid paint' and didn't get anything close. :)

The charger readout is really just a voltmeter. So it tracks the voltage as it rises, during the charging.

The charger seems to work as a voltmeter if you just plug the battery into the charger, with no AC current.
 

DMLPDX

Member
I had the same problem with finding LiquidPaint.

Just plugged in the charger and the readout was 54.6V.

So, battery does not appear to be the issue. I think the problem originated from either excessive load vis-a-vis 52T vs moisture - or a combination of both.

I used the battery straight from Luna with only charging to 80% once, which may have allowed the "unbalancing" problem George had previously referred.

Have the LiquidTape, 42T BlingRing on order. Have fully charged battery to 100% - on short ride up significant grade with no fluctuation. Will adjust rear deraileur tomorrow after guests depart.

Will advise.

Thanks again for everything folks.

Also, George, thanks for the reference to Fatebikes. There's a lot of really good info there, including tips on tires, etc. The world of e-biking apparently involves a bit of a paradigm shift.

David
 

JoePah

Well-Known Member
Uh. If the battery is only charging to 54.6 volts after a full charge you have a real problem. Either your measurements off,or you didn't receive a 52v battery. A 52v battery hot off the charger should read 58.8 volts.

Check the Luna link I listed above

Try writing down the voltage whe the battery is 100%. Then watch the voltage when you're going up a steep hill. And write that down. If you can find the power level get that as well. Report that info to Luna and aske them if that amount of voltage sag is normal. Gears etc should be noted.
 

DMLPDX

Member
Hi JoePah,

Thanks for the comment. As it turns out, I had previously set the toggle set to 80% charge. I set it to 100% charge, and upon completion the display reads only 57.9 V. So, it does appear the battery may be defective.

I'll contact LunaCycle.