Built a BBS02 bike, mistake?

Hi all, I've been lurking here for quite a while, finally got my first ebike build finished a few days ago and I am wondering if I made a mistake with my setup. I ordered my battery and BBS02 from Eric at LunaCycle, who has been very pleasant to deal with. The battery is a "48v Samsung 18650 20ah ebike battery". I've been riding road bikes for the last 4 years so I'm in decent shape and I tend to ride about as fast as I can. The bike is a 2014 charge plug 4:



I like the bike quite a bit, and on my old 4 mile commute it was perfect as a regular no motor bike. We moved a ways out of the city, so here is my new commute:



Which I managed to do a few times without a motor but it left me really sore and drained, not ideal. So I bought the BBS02 and installed it last weekend. After a few test rides around the house I rode it to work the last few days. Every time I take off with a full charge, and after about 9-10 miles the BBS02 starts shutting down while accelerating. I believe the voltage is dropping under 44v while under load, causing the unit to power down. The first time it happened I measured the battery and it read 47.8v while disconnected from the bike. I have a little inline voltage meter that I haven't installed yet, so maybe that will give me some more info once I get it setup. Anyways, it looks like I am managing to drain the battery after about 10 miles. I am able to finish the 14 mile commute, but only by reducing the PAS to a low level and keeping my cadence really high. As the battery gets low if I forget to down shift and try to take off in too high a gear it tends to switch off. The first day I rode the bike with the BBS02 I was riding in my old style, only down shifting for hills and starting in a relatively low gear. I enjoy pedaling hard at a low cadence, which is apparently not ideal for mid drive motors. Since then I read that I should keep my cadence high, and I have been doing my best to shift a lot and keep the crank spinning fast. This seems to keep the BBS02 much cooler, but has not solved the shut down after 10 miles issue.

I'm still pretty new to all this, but it seems to me that I could probably switch to a higher power battery and probably get it work on a charge without having to limp along the last 3-4 miles. However, after riding this a few days, I would like to go a bit faster. Most of my ride is quiet and secluded and I would like to crank up the speed a bit, getting to and from work a bit faster than I am able to with the BBS02. I went with the BBS02 as I have a fairly hilly ride (see above map), and I read that mid drive is best for hills. However, I have to slow down to <15mph on the hills, and I would like to go up them much faster. Now I am thinking I may be happier with a more powerful setup. I like to ride hard and fast, and I tend to only downshift for hills. On my regular bike I usually just leave it on the big crank and one of the hardest gears, as I enjoy pedaling hard at a low cadence.

Finally to my questions:

1. Does my hypothesis about the BBS02 shutting off due to low voltage seem plausible? If so, would switching to a 52V battery allow me to ride hard for the full 14 miles?

2. Would I be happier with a high power hub kit? I ride hard and fast, and I enjoy pedaling at a lower cadence in a hard gear. I would like to go 30 mph on the flats and 20+ up hills. This is with me pedaling hard the entire time. I am 200 lbs and I ride with saddlebags with around 10lbs of crap in them. I've seen the 3000w setups on a moped rim, which looks cool but that would sacrifice a lot of stealth, and I would like to stay with 700c wheels if possible. I am thinking of maybe switching to a BMC or MAC geared hub. Would they be powerful enough to get me where I want to go in terms of flat speed and hill climbing power?

Cheers

bokokon said:

Every time I take off with a full charge, and after about 9-10 miles the BBS02 starts shutting down while accelerating. I believe the voltage is dropping under 44v while under load, causing the unit to power down. The first time it happened I measured the battery and it read 47.8v while disconnected from the bike.

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I would guess that either you are not getting the actual 20Ah capacity (isn't balanced, needs to be left on the charger possibly for several days so the BMS can fix that), or you are using an awful lot of watt-hours really quickly.

I have a little inline voltage meter that I haven't installed yet, so maybe that will give me some more info once I get it setup.

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I'd highly recommend doing that as soon as you can, so you can see what watt-hours you are using, and how much the battery itself is providing.

It'll also tell you if the shutdown is because of the BMS cutting off power to the system (the voltage would drop to nothing or at least really low), or if it's the controller shutting down for it's LVC (voltage will actually go up, most likely).

Anyways, it looks like I am managing to drain the battery after about 10 miles.

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I use probably 50wh/mile on my trike, and drain a "20Ah" (more like 15-17 really, I forget the last full test result) in something like an Ah+ per mile.

If you're using ~2Ah per mile, that's a lot of power, and I'd expect stuff to be getting a little on the warm side. If that's not happening, my guess is the battery is not giving you the full capacity, for whatever reason). Otherwise, you are simply using a lot of watt-hours and are going to need a second battery paralleled to the first, or a single larger battery.

As the battery gets low if I forget to down shift and try to take off in too high a gear it tends to switch off.

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Well, if you startup in high gear it takes a lot more power, and that can use up your battery quick (and it can also heat up your motor and controller; this is the problem I have with my bikes as they use hubmotors that can't change gears, and I have lots of stops and starts).


If you prefer a different cadence, you could change the sprockets the BBS02 uses, or those yourself use, on the crank's chainrings.

Thanks for the input amberwolf, I will get the inline meter thing wired early next week, waiting on an order of connectors and wire to show up. I may try and scavenge some parts to get it wired up tomorrow so I can do testing over the weekend. The first day I rode with the BBS02 I pushed it pretty hard, and didn't shift much. The motor was pretty hot after 10 miles, when it started shutting off. Today I took it much easier, shifting a lot (which was annoying), trying to keep the motor spinning fast per the instructions here: http://electric-fatbike.com/2015/08/18/care-and-feeding-for-your-new-bbs02/. Motor was much cooler but still shutting down at 10 miles.

Who knows, maybe the battery will get better after some use/abuse? I'm still wondering if I should switch to a burly hub motor as the BBS02 feels weaker than I was hoping for.

Yikes! That seems really low mileage. I get that out of a 48V 11Ah Samsung 29E pack with a 1000W front DD. My BBS01's get 20 miles out of 36V 11Ah batts. Ouch!

if the bbs02 is the regular 750w kit there is NO WAY you can drown a 20Ah battery after 10miles. running at full amps which is around 15A to 20A at that power level it would take one hour to be depleted. and at full power and you pedaling hard you can easily do 20 mph.
you can do 30mph on the flats with that kit. speed uphills depends on your weight and hills' steepness of course.
i guess your battery is the problem. i built several bikes with that kit and even with an 11Ah battery ppl are able to do 20mi minimum.
my 2.5kW mid drive which blasts up forest's hills at 20-30mph can do 20mi minimum for 1kWh of energy.

Thanks for the input everyone. I have been able to go 25 mph uphill with the BBS02, but the motor seemed to get pretty hot. I will install a temp probe in it soon so I can watch the heat.

izeman, I was under the impression I could make it 20+ miles with the 48v 20ah battery, so I agree my current range seems very low. What should I check/watch to determine if something is wrong with the battery? I think I can get the inline meter thing installed tonight, but honestly I'm not really sure how to tell if its the battery or the BBS02 that is failling.

Thanks for the help

My BBS02 gets at least 35 miles out of a pair of 16Ah Lipos so I reckon your battery is the problem.
I weigh 300lbs and have steep hills in every direction here.
On the flat I can get 50 miles no problem.

You have a weak cell, or you have high resistance somewhere in the circuit. A bad cell is found by monitoring every cell, if they are all good then find the hot spot after a ride (or test impedance to locate what is draining your battery).

Other possibilities are:
A short. That could drain the battery even at rest.
A fault in the BMS
A mechanical resistance (friction)

MadRhino said:

You have a weak cell, or you have high resistance somewhere in the circuit. A bad cell is found by monitoring every cell, if they are all good then find the hot spot after a ride (or test impedance to locate what is draining your battery).

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A definite possibility. One side/corner of the battery feels much warmer than the rest after a ride.

MadRhino said:

A short. That could drain the battery even at rest.

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Maybe, but I am leaving the battery on the charger until I start each ride, so the battery is definitely "fully charged" when I start the ride.

MadRhino said:

A fault in the BMS

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Also a real possibility...

MadRhino said:

A mechanical resistance (friction)

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I don't think so, when the BBS02 shuts off I can still ride the bike at a decent clip. It feels pretty much like it did before installing the BBS02, just heavier of course.
Seems that the issue lies somewhere within the battery. I just bought it from lunacycle, so I will try and send it back to them for a replacement.

A 48v battery should be about 54v fresh off the charger, so 47.8v after charging doesn't sound right. Sounds like a row of cells has gone down.

On my regular bike I usually just leave it on the big crank and one of the hardest gears, as I enjoy pedaling hard at a low cadence.

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Diesel, why do you want to hurt yourself? They make gears for a reason. Seriously, it does sound like you cooked a few cells with max current demand from the battery. This kit will most likely wear out quickly riding this way. You may want a much bigger motor/ battery for speed on hills.

I see several possible problems here.

That battery is about ideal for a minimum range of 27 miles, at 20mph. As you go faster, you start using more power. Doubling your speed quadruples the power requirements. So if you're riding at, say, 30mph, you'll pull that minimum range down to about 12 miles.

So the problem would be: You don't have enough battery for the speed you're going.
Solution: Slow down, or get a bigger battery.

You also stated you "enjoy pedaling hard at a low cadence". While that's fine for you, it's not fine for the motor. Making the motor work hard by being in too tall of a gear will cause it to over heat, and also cause it to use far more power, dramatically shortening it's range.

Something is clearly faulty. You don't need to think about alternative motors until you've got this one working properly. A wattmeter will show you what's happening with the battery.

you didn't say what battery this really is. just that it's 48v. how many cells in series? this would help.

1. I'm assuming it's this battery pack.
http://lunacycle.com/batteries/packs/48v-samsung-18650-20ah-ebike-battery/
Go here and select the 26F cell, and then select 1A, 2A, and 3A discharge. On an 8p pack that equates to an 8A, 16A, and 24A draw. Look at the sag. This is why I say all those 18650 cells are best used in low draw flashlights.
http://lygte-info.dk/review/batteries2012/Common18650comparator.php
With a resting voltage of 48V, your per cell voltage is already down to <3.7V per cell group. Put a 24A load on that and the bottom will drop out, causing either the bms or controller lvc to kick in and shut you off. Most 48V controllers have an lvc of ~42V. If it's the controller cutting off, releasing the throttle for a few second should reset it so it will power up the bike again. If it's the bms I think most of them require to disconnect the battery to reset, but I could be wrong on that as I've never used a bms yet. I do have a couple of 80A ones ordered though to try out.

2. I don't know, but a DD hub motor is much more reliable.

you're right. 18650' voltage sag is the main reason i decided against them when i built my pack some time ago. nowadays there are good cells that handle that quite well, and i you make the pack large enough they can provide a reasonable current.

Thanks for the input everyone. Erica at Luna Cycle agrees there is something wrong with the battery, so it is heading back this week for a replacement. I decided to go with a different model for the exchange. The original battery was the 48v 20ah 26f model, the new one coming is a 52v 20ah 25r triangle edition. A bit more expensive but I am thinking of building a second rear hub bike, and I would like to use the same battery in both bikes, and the higher output will give me more options I suppose.

Drunkskunk said:

I see several possible problems here.

That battery is about ideal for a minimum range of 27 miles, at 20mph. As you go faster, you start using more power. Doubling your speed quadruples the power requirements. So if you're riding at, say, 30mph, you'll pull that minimum range down to about 12 miles.

So the problem would be: You don't have enough battery for the speed you're going.
Solution: Slow down, or get a bigger battery.

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I have been averaging about 15-17mph overall for the ride, as I have to stop a lot for traffic/peds/lights etc. So my average pace while riding is probably a bit over 20mph. On the straight flats, which there aren't many of on my ride, the speedo says I am going 28.5mph, which I think maybe slightly exaggerated. I am used to cycling on a regular bike, so I am working pretty damn hard the whole time. With the BBS02 there is a point when you feel that you are spinning the crank faster than the motor and I get there consistently. It feels like the motor is helping me accelerate and I am doing most of the work at cruising speed. Anyways, my point is that I am going fast but I am also working hard. You think this style of riding will still leave me with half the range?

speedmd said:

On my regular bike I usually just leave it on the big crank and one of the hardest gears, as I enjoy pedaling hard at a low cadence.

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Diesel, why do you want to hurt yourself? They make gears for a reason. Seriously, it does sound like you cooked a few cells with max current demand from the battery. This kit will most likely wear out quickly riding this way. You may want a much bigger motor/ battery for speed on hills.

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Hah I definitely use the gears on my bike, I did ride single speed for several years, so I got used to pedaling at a slower cadence I guess. Anyways I got tired of struggling up Seattle hills so I switched to a regular road bike and I do shift plenty, just probably not as much as most cyclists. If you read the OP, I noticed on my first ride that the BBS02 got really hot after 10 miles or so of riding. I wasn't downshifting enough, and I was going pretty damn fast uphill. So I did some reading and all my rides since then I have slowed down on all uphills and I do my best to keep the crank spinning fast. However, this hasn't really changed the range of the battery. The battery advertises 50a continuous output, 80a bursts. Doesn't the BBS02 draw 25a max? My understanding of how all this stuff works is pretty limited but I don't think the BBS02 should be able to damage the battery going up a few short hills.

My pack is rated at 200A continuous 20C and 300A burst 30C, but I can guarantee it wouldn't last long if even stressed to half that. The 26F is <2C rated (5.2A), so best used at <1C. 50A on an 8p pack is ~2.2C (over 6A), so over the max rating. The 25R cell is rated for 8C (20A) so is a lot better suited than the 26F. I'm going on 4 years and 12K+ miles on my $275 888WH 10ah 20C 88.8V rc lipo pack and I've still got ~90% capacity. Running at 1C still gives me 1000W of power, which is one reason I went to 24s.

Understood, you like mashing gears. Me also, but have learned to spin as it does work much better long term (knees) and you generate much more power for much more time. I see joint replacement in folks that never learned the lesson quite often these days.

For the battery, it most likely got out of balance causing a cascade effect on the weak cells, dragging the whole thing down quickly. Like two guys lifting / moving a log, and one guy runs out of strength and starts dragging his end causing the move to stop quickly. Big gears and dead stops will spike current better than most anything, slamming the weaker cells most from what I understand.

The Max current from the controller on the BBS02 should not , would not, be enough current to damage a good battery . Luna batteries were supposed to be good .
Did Luna not check the batteries when building the pack ?
Sounds like the battery pack to me, as I have a cheep battery Chinese pack rated at only 2c and I get more miles that that , with a Mac running on 48 volts ( 54 volts , not, hot off the charger )
at 18 to 19 amp limit .

speedmd said:

On my regular bike I usually just leave it on the big crank and one of the hardest gears, as I enjoy pedaling hard at a low cadence.

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Diesel, why do you want to hurt yourself? They make gears for a reason. Seriously, it does sound like you cooked a few cells with max current demand from the battery. This kit will most likely wear out quickly riding this way. You may want a much bigger motor/ battery for speed on hills.

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ScooterMan101 said:

. Luna batteries were supposed to be good .
Did Luna not check the batteries when building the pack ? Sounds like the battery pack to me...

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Sheesh. That was already determined, bad battery pack and Luna is replacing it. You won't see that happen with a China battery. It doesn't get better than Luna.

More and more I'm thinking the BBS02 isn't a great commuter. Perhaps with the new generation 48V there will be fewer problems. I hope so. I still like this setup better than any other. Big old heavy HD are a yawn by comparison.

For flat road riding, why deal with the complexities and wear issues of a mid drive. I don't believe It was ever intended for that. It's forte is the adaptability to using a vast array of gearing options for integration into more varied rides / riding situations. Nothing beats this type of drives ability at riding around the cow pastures (natural terrain) throughout the world.

speedmd said:

For flat road riding, why deal with the complexities and wear issues of a mid drive. I don't believe It was ever intended for that. It's forte is the adaptability to using a vast array of gearing options for integration into more varied rides / riding situations. Nothing beats this type of drives ability at riding around the cow pastures (natural terrain) throughout the world.

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Depends what's important to you. Crank drive means the wheels are easier to remove and install for flat repairs.

tomjasz said:

ScooterMan101 said:

. Luna batteries were supposed to be good .
Did Luna not check the batteries when building the pack ? Sounds like the battery pack to me...

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Sheesh. That was already determined, bad battery pack and Luna is replacing it. You won't see that happen with a China battery. It doesn't get better than Luna.

More and more I'm thinking the BBS02 isn't a great commuter. Perhaps with the new generation 48V there will be fewer problems. I hope so. I still like this setup better than any other. Big old heavy HD are a yawn by comparison.

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Exactly. I am so glad I went with Luna over a foreign vendor. New battery arrives Friday, I would be waiting weeks and probably paying full price for a second battery had I ordered from elsewhere. Eric is very helpful and experienced as well. Things go wrong, especially with hand built batteries I imagine, LunaCycle promptly agreed to replace the battery, and even let me pay the different to upgrade to a different model. Assuming the new battery treats me well I will go back to them in the future.