BionX 500HS MOTOR and longevity of the 36 V Li-ion battery

the regen mode could exceed the bms or the cells ability to take the amps. if your batt is similar to mine, more than 5 amps is bad. it may also depend on usage, whether you brake to stop, or ride down a hill for more than a few seconds. a huge hill could over amp long enough to damage where a short spike may be within its specs. you need to ask your vedor about what the batt can do. if you can turn off regen it may be the thing to do. that way if you buy two batts, you have two good batts and tons of range instead of one good, one ruined. batt abuse is bad for all chemistries, but with lipo4, losing 10% may still leave you with years of cycles. sorta like we used to think about mileage when gas was cheap. also ask the vendor if it may toast the cells or just the bms, or maybe the bms just cuts out and protects the cells like it does for discharge.

I have heard (apparently this news comes from the one of our european importer) that is is not good at all to use the recharge function of the bionX

This would mean that Bionx didn't design the regeneration circuit properly. I have a hard time believing this. Yes regen provides wildly fluctuating voltage, but this is always the case. The 500W motor shouldn't provide that much more of a challenge. I'd want something more than a rumor before I stopped using regen.

I have had a Bionx in daily use for over two years now and the Lion battery still shows no appreciable wear. I use regen all the time.

i should read better, if the lion came with the bike, it should be designed to take the regen. i was stuck to the duct tape in my brain.

For that question, i think the forum needs to know just what kind of battery you have. As I understand it, only nicads like the deep discharge. If you battery is lithium polymer, like most cell phones, they really do like shallow discharges better. On my first phone, I treated it like a makita drill, discharging all the way before charging, and wrecked the battery in 3 months. Now I get two years on a phone battery by charging often to keep the cycles shallow. On Lifepo4, the 1000 cycle promises are for full discharges, but I think it still makes sense to charge ev's at every opportunity. Especially free ones!

Do you recharge the battery when it is almost empty or do you always leave about 20 % charge ?

I always charge it when I am done riding regardless of how much I have used. I try never to drain it empty. With the exception of the "memory effect" of some old NiCd technology, this is the way every battery likes to be treated. The reason is basic chemistry. A battery is a mostly reversible chemical reaction. Every time you use it some of the chemical reaction is irreversible, however. With lead acid batteries this the salts that form and precipitate out of the electrolyte. The more deeply a battery is discharged and the longer it is kept that way the more of the reaction becomes irreversible. This is probably the same way with NiCds, too, it's just to get any use out of them you had to run them through a deep discharge cycle at least once.

Hello.

I finally ordered a PL-350 too.

I asked a similar question ("using generation mode will ruin the battery?") to bionx and I am waiting for their answer. Basically my concern is about generation mode: with my Li-ion mobile phone battery I found that charging only partially the battery drastically reduces its duration (I started with 5 days autonomy, charging it from the standard charger). Then I started using a car-charger (so I charged the battery when driving the car, so mostly short chargment cycles of 20 minutes only). Quickly my battery life shortened from 5 to 2 days.
To go back to 5 days I had to totaly decharge the battery many times and full recharging using the "wall" power supply.
My fear is that Bionx generation is like using the car charger (many and short charging times).
But from Dave's experience it seems this is not the case. Anyway I'll wait for Bionx answer and if interesting I'll post it here.

By the way another story is my laptop: I have it since 3 years and half. It has Li-ion battery. 95% of times I use it with power supply, and when using the battery I almost never use it fully (so when I plug it again, the battery recharges even if there is still a lot of energy left). After more then 3 years the battery duration seems still the same (2 hours and half with normal usage and screen luminosity set to minimum)...

So combining these not-Bionx-battery-experience I'd say:
1) it's ok to charge Li-ion batteries even if they have still energy in them (laptop experience)
2) it's bad to charge partially the battery (mobile phone experience)

If (1) is true it is ok to charge the battery every day (even if on Bionx handbook they suggest ot charge it everyday if the battery level is under 50%).

If (2) is true we should avoid using generation.

But...

From what I read here it seems that generation is well desinged and worth using!

So combining these not-Bionx-battery-experience I'd say:
1) it's ok to charge Li-ion batteries even if they have still energy in them (laptop experience)
2) it's bad to charge partially the battery (mobile phone experience)

Statement 1 is correct. Statement 2 can be corrected by saying "it's OK to partially charge the battery, as long as you fully charge the battery after each use". On the Bionx you will be getting small charges from the motor when you brake. This is know as regenerative braking. These small charges are fine as long as you have used enough power from the battery before you start to put energy back. Think of it like a glass of water. The glass is full to the rim when you start. As you use small amounts of water there is now room in the glass to add a little water, however if you try to add more water than you have used the glass will over flow. The over flow in a Li-ion battery causes damage to the batteries. So you don't want to start your ride down hill before you use the motor on the flats or uphill for a mile or so. These short charges should not be a problem as long as you fully charge the battery after each ride. This would be like using your laptop on battery power then plugging it in to give it a chance to fully charge the battery.

BTW I charge my cell in the car as well but my accessories connection stays on all the time so it gets a full charge.

Grandpa Chas S.

Thanks Chas for the really clear answer.

I have to avoid to use generation when I start downhill. My house is in the middle of a 3km-long-5%-steep road, so half of my trips will start downhill.

When I start downhill with full battery I should avoid using generation. But I need to use breaks to survive. So maybe I should not use the break sensor or using only the front break when just leaving the house.

Just one final question:

I got the full glass idea, but what about the following scenario:
1) Today I start with full battery and use 40% of it WITHOUT USING GENERATION so I don't need to recharge it in the evening
2) Tomorrow I start (with 60% of battery) and I start downhill...

... In this case can I use generation (since the glass is not empty) or it's still better to try to use some energy before using generation?

(of course once back from "tomorrow" trip I'll need to recharge the battery since I used generation in this trip).

Thanks again!

1) Today I start with full battery and use 40% of it WITHOUT USING GENERATION so I don't need to recharge it in the evening

No No No.... You should always charge the batteries after every use. By charging the battery every time you use it you will increase the overall life of the battery. A battery will last longer if you use several shallow discharges as opposed to one deep discharge. Li-ion batteries are not effected by this as much as Lead Acid but it still has an effect on them. There are 2 ways to damage Li-ion batteries over-charge and over-discharge. Li-ion batteries have a voltage range they like to stay in. The range per cell if 3.86-volts down to 2.1-volts. If you keep your Li-ions in this range you will have no problems.

Now for my opinion on regenerative braking (Regen) on e-bikes. It is worthless!!!! Test have been done which shows Regen works well on EVs above 300 pounds because there is enough weight to produce a reasonable amount of energy from the motor. But on EVs that weighs less than 300 pounds more energy is saved by costing. I personally would not use the Regen feature just disable it. Somewhere here on V is a discussion about Regen that shows you can go farther by coasting, using the energy to allow you to freewheel, than you get back using Regen on the lighter EVs. Regen produces very little return to the batteries on light EVs so to keep Regen from causing you problems, and eliminate one more thing you have to worry about every time you leave the house on the downhill run just disable it.

I am sure there are some here would will disagree with this and I respectfully ask them to prove me wrong. This is something I have tested and on a single charge I went 1.2 miles further when coasting on the same hilly route.

Grandpa Chas S.

I did a bit more research and found this paper on Regenerative Braking.

Grandpa Chas S.

Hey Brace.
My hunch is a short 20 minute charge is not fully charging the phone, but when you unplug the phone from the charger in a way you have fooled it to reading a 'full' battery . This is a sneaky trick us electric forklift operators use to avoid the labor of changing the battery out before the end of our shift and passing the duty over to the next shift driver. The lazier driver would periodically plug the battery in for short quick charges and/or just before the new driver shows up to work , when the new driver gets on the thing it reads 'full' but it's dead in 1 or 2 hours rather than 7 or 8.
I think what Dave is saying is he uses the Gen and also Fully recharges the battery at the end of daily use, the latter being the defining factor in the longevity of the battery. So...
(1) Fully recharging is best .
(2) Gen is good, but I would not to see it as a primary source of daily charging but rather to compliment the Full charge it will get later.

I did a bit more research and found this paper on Regenerative Braking.

Very interesting document. I read it all.

For sure 2 better ways to "generate" energy are to improve the aerodynamics and using coasting as much as possible.

That said in my particular case there is one situation where I can take advantage of generative breaking: and this is downhill. Since I live in a mountain area it is not uncommon to have 6-7 km downhill roads. On those roads to survive you need to break, and so generation could be succesfully used. Anyways since Li-ion batteries cannot be charged too fast I should manually control the amount of friction breaking (using front break) and generaitve+friction breaking (using rear break and generative breaking both activated by using the rear breke handle) in order not to use generation only if the road is too steep.

Anyway I agree with the author of the article that generation should not be one of the 3 top features of an electric bike. If 10% of extra range is what we can expect from a very good generation system (like probably Bionx's one), it's better to have a battery with 10% of extra range and so we don't have the fear of damaging the battery since we are charging it too fast or things like that.

Anyway these info are really interesting. And since I have thie generative breaking I will for sure experiment with it. A good place to use it could also be 1% downhill with tail wind: instead of simply coasting it's possible to pedal a little and so in this way we slowly charge the battery.

But let me say one even more important thing: since when back home I'll totally recharge the battery I really need generation only when I am doing a trip where I know I risk to use the whole battery. In this case generation will give me those few km more to arrive home. But realistically when will I do a trip that is exactly my battery range+10%?... Probably... Never!!!

And so I can see 2 scenarios:
1) generation is practically useless...
2) ...unless the charger that charges the battery at home takes advantage of the generation I made, so it can charge the battery consuming less energy. If this is true, generation makes sense (since it makes you save on energy) and it's "enviornment friendly".

You all have missed breaking pads and rim saving aspect of regen.
I simply cannot imagine my TF withot regen.
Grinding rims with rubber plus dirt - terrible way to stop 28kg bike.
I don`t know how your regen works but on TF just sligt squize of handle produce strong breaking force saving pads and alu rim in the front. Without regen it would take twice AT LEAST distamce to stop my TF. You all forgot
wet rim in the rain , in this condition it would be suicide to ride my TF.
I am know very well that charging effect is so small, in my case regen does`t serve charging purpose.
Miroslaw

I have a few questions about the regen issues mentioned above.

Is the regen braking usually "all or nothing" on the e-bikes? Or can you control it, break a little bit or a lot, as needed?

Do the problems mentioned also apply to NiMH batteries?

I regularly use regen braking down the steep driveway, first thing after charging my Vectux. Should I stop that? The Vectrix tech told me it was no problem (when I enquired if that might be the cause of the motor controller fuse failures.)

Since I have the RETAMPI I have been able to observe that the Vectux battery receives about 13 times the amount of (peak) current during regen braking compared to the highest continuous current during charging. It shows the induced voltage of a Hall-effect sensor on the MC board (around the main positive battery cable).

And the peak regen current is 66.6% of the maximum current drawn during full acceleration, which must be less than the 125A rating of the controller fuse.

This is at the start of recharging: (7.03A @ 240V going in...)

I hope the NiMH battery can take the regen current without damage. I think I heard that they can accept high charging currents, but get damaged if they heat up too much. There might not be much of a heat problem due to regen braking, unless down a long, steep road.

Mr. Mik

I have a few questions about the regen issues mentioned above.

Is the regen braking usually "all or nothing" on the e-bikes? Or can you control it, break a little bit or a lot, as needed?

Do the problems mentioned also apply to NiMH batteries?

I regularly use regen braking down the steep driveway, first thing after charging my Vectux. Should I stop that? The Vectrix tech told me it was no problem (when I enquired if that might be the cause of the motor controller fuse failures.)

From what I learned in this thread you should not using regen braking with full battery. For Bionx you have all or nothing, but you can add extra breaking using the friction from your standard breaks (in order not to "overcharge" the regen circuit). So in this way you can "modulate" the all or nothing with your normal breaking, obtaining what you are looking for.

Moreover you can read the document linked a few posts above, from which I quote:

So, for any slope steeper than that, regenerative braking could recover useful energy. But remember,
there's a limit to how fast batteries can be charged and still maintain a long service life. From the
previous discussion, our 20Ah lithium ion polymer is limited to 111 Joules per second.

So an high input current is not the best thing you can use to feed your battery.

Moreover you can read the document linked a few posts above, from which I quote:

So an high input current is not the best thing you can use to feed your battery.

I read it all with interest.

But the problem remains that the differences between battery chemistries are enormous, and there seems to be little experience with NiMH batteries in EV's.
I believe I read the RAV EV has NiMH and some still run after long distances.
But even NiMH is not necessarily the same as NiMH.

Is anyone aware of other EV's with NiMH batteries?

Mr. Mik

The EV RAV4 uses, if I recall correctly, the Panasonic NiMH batteries which were the subject of the lawsuit between Ovonics and the Japanese. Ovonics was the inventor of NiMH batteries and had never licensed to anybody the rights to use NiMH batteries in a vehicle. I guess they saw that as their possible gold but there are some who point conspiracy fingers at the fact that Ovonics ownership has been for years been partly in the control of either GM or Big Oil, and that GM/BigOil wanted Ovonics to keep NiMH out of the hands of vehicle makers for nefarious evil reasons. I dunno.

Cobasys is a result of that lawsuit, in that it's a joint venture between Ovonics and some other companies (??Japanese??) .. Ovonics won the earlier lawsuit and Cobasys was their winnings. Cobasys has technology for large format NiMH batteries.. last time I checked it was 90AH per battery.

These batteries were used in the EV1 gen2 (the NiMH version) and in the EV S10 pickup both from GM.

I'd talked once with people at evbones.com (they specialize in revitalizing EV S10's) about the possibility of buying some of the Cobasys batteries. They managed to convince me otherwise in that ... you could only buy a pallet of them, at a cost of approx $20,000 ... and that these batteries were highly prone to explosion and absolutely must have a BMS unit but there is not a generic BMS instead each vehicle maker is supposed to design/build their own BMS unit.

I've never heard of a NiMH battery which was prone to explosion. But that's clearly what the guy told me.

BTW I believe the Honda Insight and Toyota Prius both use NiMH batteries. But that they're built up from some form of 'D' cell.

I have the 24 V Li-ion (Manganese) battery with my Bionx 250 Watt system. I have 900 miles on the system and mostly do not even use the plug in charger. I climb 1000 feet (700 net) on my ride into work. I use the assist level 1 for the last mile which ascends 450 feet in about one mile. This is a steep hill in Deer Creek Canyon, southwest of Denver. On my way home, I use the regen mode for all of the significant downhills. Without braking, I would hit 45 mph on the big hill. With regen set at 3, I'll still go 30 mph. Yes, I realize that this is a lot of charging in a short period of time. So far system is holding up. I leave the house with the battery full, get to work with one or two bars gone, and arrive home with the battery full again. Diagnostic mode shows the battery to have 28.9 volts for my full charge. Every once in a while it will show 29.0 volts, but this usually comes down to 28.9 overnight without my using the bike at all.

I do have some concerns about my high rate of charging. I did once ride the bike from where I work (South Valley Road and Deer Creek Canyon, Littleton, Co) up to Marshdale, in between Conifer and Evergreen. On the way home, I used the regen braking for most of the trip. I descended from 7200 feet to 5700 feet in about 7 miles. The battery did not blow up. I felt the case, and it did not feel real warm.

Anyway, the system has lasted 900 miles (nine months). ONly once or twice have I had the battery down to showing just two bars on the charge meter.

One of the settings for the system sets the regen charge level. When I have the system in diagnostic mode, I see that regen level one causes a "5" to show, level 2 is a "10", level 3 is a "20" and level 4 is a "40". The regen level is "45". My dealer set the bike up this way. I think the max number is 60, but I assume that that would mean an even higher charge rate.