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So, theoretically, one can ride past the zero-bar level (for another 10AH or 20AH)... correct?
Once you've done a few complete cycles does the fuel gauge reflect the battery level accurately? Or do you depend more on the odometer?
yes, theres nothing stopping you from riding past 0 bars until the battery is actually flat.
If you have access to a data cable, you can actually set the fuel guage assumed capacity to at least 34Ah, probably more.
I figure most do not have access to a cable, so I videod the tutorial on the assuption you would not have access to one.
Later I will do a video for those who do have access to a Peak CAN-usb cable.
The thing to watch out for is how balanced the battery is at the bottom (ie do they all go flat at the same time).
LiFePO4 cells don't survive a reversal in the same way a nimh battery can.
To get best service life and usability out of a LiFePO4 batttery, aim to only use 80% of its capacity.
so thats 32Ah for a 40Ah cell
and 40Ah for a 50Ah cell
If you stick to 80%, it will be a long time before reversing a cell is a possibility.
If you set the fuel guage so 0 bars = 80% used, than you aren't trying to do sums while riding (its just plug and play).
The other thing is that 80% used is towards the end of the "flat" region of the discharge curve, meaning each bar represents the same amount of range, all the way to 0.
the fuel guage won't change automatically, as the red light-recharge-red light solution only sets the guage to a max of 30Ah (0x9C 0003, 0x9E 6060).
Matt
Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km
It looks to me like the Evpower BMS system is configured to turn off the Vectrix charger if any cells are overcharged but doesn't use a contactor to disconect the Vectrix battery from the motorcontrol board in case any cells are overdischarged. If this is true then is it possible to do that or run an alarm when that happens ?.
I'm ordering the 50AH batteries (from FalconEV).
I'm ready to order the kit - just let me know when/where to send the payment :-)
So, if I leave the fuel gauge as is - and I have the 50AH batteries, when the fuel gauge goes to zero, and the red battery light comes on... I should be at about 60% discharge, correct?
I'm thinking that I can treat this similarly to riding a gas-bike with a "reserve" capacity. Once the red-light comes on I should still have plenty of range to find a place to plug-in without worrying about getting stranded.
But, my son is the computer genius - if anyone can reprogram the fuel gauge he can ;-)
yep, you got it.
The master module actually sounds a high pitched alarm if any cell goes out of bounds (ie below 2.5v or above 4v).
it also opens the main relay (so basically you can't charge).
It can't do anything about overdischarge - I don't know of an easy way of implementing it.
My solution was to have the fuel guage say the battery is flat somewhat short of when it actually is.
so basically stay away from the bottom end and all is well (don't try to go past 0 bars).
as it happens, in the beginning, your cells come from the factory sufficiently well matched that all of them go flat more or less simultaneously.
so the pack level low voltage limit works fine in stopping you from damaging anything.
as the battery gets older, their capacities start to diverge, so that where when new a red battery light used to mean your battery is flat, it would now mean on an old battery you have lost a cell.
But to get to the condition where you can overdischarge and reverse a cell, you either have a pack where the capacity has fallen below what the fuel guage thinks it is (so have done the 1000+ cycles) or gone well past 0 bars.
as far as going past 0 bars without red battery light (ie using reserve capacity), you could probably get away with it once in a while.
the thing to watch out for there is that the original charger will only put back in the assumed battery capacity + 3Ah.
example:
you have 50Ah cells.
your fuel guage assumes 30Ah capacity.
you ride, go past 0 bars and use 40Ah.
on recharge, the charger puts back in 33Ah, meaning the batteries need another 7Ah to be full.
on subsequent recharges, the original charger still tries to put back an extra 3Ah, so it will sort itself out given long enough.
I suppose the theme of this post is not to go past 0 bars :)
Matt
This
Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km
Thanks Matt that's what I wanted to know. I would prefer an active way of protecting the battery but an alarm would suffice.
Maybe a solution to the problem is using a latching type contactor like this http://www.gigavac.com/products/contactors/datasheets/gxl14/index.htm .
It's better than a plain contactor because it normaly uses no power.
getting a contactor to break the circuit is no problem (I'd use an ev200, its rated to break 2000A @ 300v (once), and costs $65).
I'd prefer power to hold, and loss of power to break, from a reliability perspective.
that gigavac costs ~$200.
The contactor are largely accademic at this stage.
its deciding when to open it thats the real trick.
thanks to the variation in equivalent series resistance amongst the cells, you could well find yourself with a bike that won't move just as you are trying hard to accelerate past someone.
ie, 42 cells = 108v (controller low voltage limit)
so cell average = 2.57v.
some are below 2.5v, mainly because you are drawing ~200A, not because cells are being reversed.
That would be rather a bad time for the contactor to open.
1V is actually the lower limit on LiFePO4 cells to stay away from.
below that little micro shorts form, and you suddenly have self discharge.
The BMS in the kit can sort out the self discharge, but its best avoided all the same.
The ideal solution would be for the controller to limit sag so that the lowest cell is maintained at 2.5v, rather than just keeping the traction battery above 108v.
That has the effect of slowly reducing power and top speed until the bike effectively won't move (you're well past 0 bars by this point, so not unexpected)
limiting the lowest cell to 2.5v is possible, but will require re-writing of the motorcontroller program/firmware, something thats beyond my capability.
The red boards on top of each cell already provide a high bandwidth good/bad signal, so the motor controller only needs one input (not 42).
It could also be implemented by putting a big high power resistor (like a 1kw light bulb) across the contactor.
That would limit the bikes speed to a crawling pace.
All this is something thats only necessary when you are trying to use every last Wh out of your battery.
At this stage its cheaper and easier to put in a bigger battery than try to sqeeze every last Wh out of a smaller battery.
Matt
Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km
actually, on second look,
that gigavac contactor is really cool :)
although it latches, IIRC it still draws power if you keep applying voltage.
it just won't open when you stop.
very interesting indeed.
I had a look at them when www.evworks.com.au started stocking them, but didn't use them as the EV200's where plentiful and cheap.
Matt
Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km
Curious - once the bike is converted if we still find that we have just the 30AH capacity to use (despite installing the 40 or 50AH batteries) what is the advantage of the larger capacity battery? I will be happy, of course, to be able to ride all the way until the last bar disappears, but if the 40AH battery pack and the 50AH battery pack should be used just the same as a 30AH pack, i.e., not ridden below 'zero' bars, is it worth investing in the larger battery pack?
When I was making the decision on whether to get the 40AH vs. the 50AH pack I thought that the 50AH would provide a greater range. But if I'm understanding the last few posts - I would need to either modify the fuel gauge to reflect the presence of the increased capacity, or just plan on plugging it in whenever the bars on the fuel gauge reach 'zero'.
If the safest bet is to just plan on not going below 'zero' bars on the fuel gauge - then the 40AH battery pack would seem to be the most practical choice - don't you agree?
I had decided on the 50AH pack, but now I'm re-assessing my decision - any advice would be welcome.
Hi oobflyer, I think you got it wrong. Riding a full 40AH pack down to 5 Ah using 35Ah would mean to use the last 5 Ah without the fuelgauge, and the estimated range. The MC does reduce the poweroutput when the voltage gets below a certain value at a certain current draw. It does not reduce the power when the gauge shows zero bars.
Greetings Mike
Matt,
As far as I remember the BMS that you use has two relay outputs, one triggered by over-voltage which you use to shut off the charger, one for under voltage. The latter could simply be wired in parallel with the kill switch. I am sure Mik would know exactly where best to tap those lines. This way you would shut off the bike when a cell goes under voltage and protect it from reversing.
Harry
Regarding contactors in the VX-1: You would need at least 2 contactors so that the first one closes with a resistor in series and pre-charges the capacitors. Otherwise you would have repeated inrush-current events destroy the fuse and maybe even the capacitors on the MC.
Regarding battery capacity: Larger batteries might last much longer (increased total lifetime mileage) due to several factors. The main issue is how well they can cope with peak current draws. If a battery is capable of 5C current, then for a 30Ah battery this is 150A, for a 40Ah battery it is 200A, and for a 50Ah battery it's 250A.
I have not looked into the specs for the various Lithium cells discussed here, but you could of course have a 40Ah cell capable of higher peak and/or continuous current than a 50Ah cell. It seems to me that higher capacity cells might be worse off in demanding applications like an EV, because they might have been designed for higher capacity, not higher current or power. For example the 6Ah NiMH cells in the NHW10 Prius have about 30% less capacity than other D-sized cells (9000mAh), but can handle 100A peak and 32A continuous current draw.
The other issue is depth of discharge (DOD). For NiMH it is certainly an issue, but I'm not certain how much it matters for LiFePO4 batteries. If you regularly drain the battery empty and regularly fill it completely, the overall mileage you get out could be drastically reduced.
For me, I'd prefer power over range. The acceleration of the VX-1 is too low for my liking anyway. Choose a battery that can tolerate regular full throttle accelerations and allows double the range that you regularly use. Keep it between 30% SOC and 80% SOC most of the time.
Regarding low-voltage cutoff (LVC): I share Matts concerns about sudden shutdown under heavy acceleration. It should be up to the rider to decide if they want to risk the life of one of the cells, or their own life! The cell-level LVC should in my opinion be set so that it gets triggered under the heaviest acceleration when the battery is at less than 25% SOC. It should trigger a very bright blinking LED and a warning sound. That way it will be a useful tool that allows to use all the battery capacity if needed, by adapting the throttle demands to the voltage drop of the weakest cell. But it would allow as much power to be delivered as the rider demands in emergencies.
For rental bikes or bikes sold with a warranty this approach would likely cause battery damage and trouble, but I am talking about a solution for the knowledgeable owner-rider of a Vectrix.
This information may be used entirely at your own risk.
There is always a way if there is no other way!
So far I have only quoted range with 30Ah, as to set the fuel gauge to that you usually don't need access to a usb-CAN cable.
The worst case scenario is if you buy the 50Ah cells, and I don't find a way to set the fuel gauge above 34.3Ah even with a usb-CAN cable, is the battery service life is very very long.
partially because a bigger battery is less stressed, alot more because much greater capacity loss can be accepted before you start losing range.
That or you install a cycle analyst like I did, so you can see exactly how many Ah you have used.
its not overly user friendly in this application though.
The way the fuel gauge works is:
There are two memory locations inside the charger that tell it how big the battery is.
at present, to get 34.3Ah you enter
0003
FFFF
in binary that works out to
0000000000000011
1111111111111111
Now a memory location does not necessarily serve one purpose.
It is possible that part of the program that does the counting from 0, up to the assumed capacity, only looks at the first 2 binary locations of the first memory location.
Given Vectrix are planning on releasing at 42Ah version, I'm pretty sure the count up program looks at at least the first 3, allowing:
0007
FFFF
or
0000000000000111
1111111111111111
or
a max of 71Ah.
The best case scenario is that is the case.
I am still trying to get access to an original charger again to try it out on my own bike (I sold my own charger some time ago).
The master module has a single relay, which I am using to connect/disconnect the charger from the mains.
The powersupply driving the relay is a 12v one, and is large enough to drive a contactor aswell, or just about any other relay.
you could use the kill switch instead of a contactor, but again, there is still the problem of differentiating between sustained acceleration, and cell reversal.
Matt
Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km
The Cycle Analyst meter seems like a nice alternative - maybe that could be added to the "premium" kit?
;-)
I might add it as an add-on to the kit.
It may not be economic to send it around the world for USA customers (since its made in the USA and I'm in Australia)
basically you need the 200v high current variant (US$140+$10shipping) and a 75mV 100A shunt (~US$10 inc shipping).
I will make a video for it once i get around to it, but, I have to get the kit all together first before I start worrying about add-ons :)
Matt
Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km
That sounds good Matt - I'll order the Cycle Analyst from here and look for your advice on how to hook it up while we have the bike apart.
I ordered the batteries! I went with FalconEV and the 50AH batteries. The gentleman at FalconEV strongly recommended the CHL brand over the others mentioned earlier. I'm not sure what his experience was, but he made it very clear that CHL brand was superior. In any case - I've made the commitment - now the hard part... waiting!
I Have ordered a 200v cycle analyst high current variant (also large screen).
I plan to put it on one of the Vectrix's I converted a few weeks ago.
That will allow me to add that extra installation to the videos.
Then I will try setting the fuel guage to 36Ah (0004 0F00) to see if it still works correctly.
I will report back if it does, so that everyone wanting 50Ah conversions will know for certain that it works (I still think it will).
Matt
Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km
That sounds good, but for those of us without computer knowledge the Cycle Analyst seems like a good option. If I had that on my bike and just kept an eye on the Amp-hours that I've used I'll know when to start looking for a plug (I imagine around 45AH?)
I watched an interesting video yesterday:
http://jackrickard.blogspot.com/2010/07/4c-lifepo4-power-tests.html
in it you can see a demonstration of how the Li-ion batteries behave under load when stressed to the maximum capacity. The test was done on a 100AH pack with a 400 Amp load (4C in 2.5 AH bursts) until the batteries had spent their claimed 100AH capacity. Since they were pushed to the limit they were damaged, but that was the point of the test - too see when to stop and recharge. The conclusion? 95% - in this case 95AH. So, I image that 50AH batteries should be able to handle 47.5AH of riding, but to maintain an extra buffer of safety 45AH might be a good cut-off. Do you agree? How many AH do you use on your 60AH Vectrix before looking for a plug?
Here's my dilemma. What do you guys think?
Here in Australia the Vectrix was originally about $17k. I liked the concept. Went for a test ride, loved it, but thought it was just a little expensive for what it is.
After a while, the price dropped to about $14k and I had another "hmmmmmmmm" moment, but I was very happy with my Scarabeo 500 and still didn't go ahead with it.
Then Vectrix went bust and the Aussie dealer started selling new left over stock on ebay. I picked one up for just over $5k thinking that the worst that could happen is that I lose $5k, which I'd lose on just about any of the scooters which I'd have otherwise considered. I've been very happy with that decision so far. I'm still getting about 40km from it easily enough for my usual riding and 35km on freeway. That's possibly 5km less than when I first got it, but it's difficult to quantify.
Of course the one issue with the Vectrix has always been range. Apart from that I really enjoy the ownership experience. Now thanks to Matt I have the ability to double (or more) the range...but the cost of that will be not much change from $6k including shipping the scooter to the other side of the country and back.
So now to that dilemma I mentioned. I will then have a scooter that will owe me $11k which still has no parts available, no service back up and no sign of things realistically improving which could break down tomorrow, whether it's a circuit board, a motor, accident damage, whatever. I'm a bit concerned about spending another $6k on something that could stop working tomorrow....permanently.
Thoughts?
If you get to where you need with your 40km range, I would wait until the bike actually fails. Even with Matts Li conversion, you still have limited range. It still isn't a real motorbike. What if the motor controller fails after the upgrade, then the charger, etc. Even the plastic of the fairngs. What if one falls and breaks that? Until Vectrix is back and selling parts again, these bikes are hard to service and not a good investment. I actually bought a used 2nd Vectrix which I got for under 2k just for parts.
That's just my opinion.
I understand the dilemma - I went through the same process, however I decided to go for it. If you want to wait and see how it works out for me I'll be posting here as the project moves forward.
Meanwhile - isn't Vectrix officially back in business? If the charger breaks down, for example, can't we contact Vectrix and purchase a new one? I haven't tried it recently, but when I wrote to Vectrix in February of this year (2011) I received a reply regarding the parts needed to take apart the battery pack (Can-BUS cable, in-rush limiter, etc.). I decided not to go that route, but they responded with the prices and ordering info that I requested.
I tend to be optimistic - and, of course, I knew from the beginning that I was taking a risk on a new company/new product. The cost wasn't so high for me, however. The VX-1 cost just over $7K (after the California state tax incentive). The Li-ion upgrade will cost me around $5K. So, I will have $12K in a bike that could potentially save me thousands of dollars in gas ($12K was the original asking price for the VX-1, but as you mentioned, they dropped the price soon after they started selling them). This doesn't count the 10K miles that I already have on it.
It's a tough decision - let us know what you decide.
Just out of curiosity: How much did they quote for the inrush current limiter?
This information may be used entirely at your own risk.
There is always a way if there is no other way!
yep, using a cycle analyst is the easy way (its actually the way I still use).
If the fuel guage won't work, I will have to make a separate kit for the 50Ah cells that includes a charger replacement.
A new video will also be needed to show that installation.
That change would cost ~$600 extra, but does mean you have an original Vectrix charger you could sell.
On my 60Ah cells, I aim not to go past 48Ah (or 80%).
I once got as far as 50Ah.
I could in theory go further, however, acceleration starts to degrade and becomes less predictable.
for continuous discharge, 80% is about where the voltage starts to fall off a cliff.
for dis-continuous discharge (such as jacks test) you can go much further.
basically the lithium ions have time to get back into the easy to get to areas.
you also see this effect when you park up for a long period of time.
Matt
Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km
The cycle analyst is a week away from being shipped.
The bike to put it in won't be available for around 3 weeks.
btw - if you are going to buy a cycle analyst for a vectrix,
I highly recommend getting the large screen version.
they're all 200V units, and are easier to read if your eyesight is not that of a 20 year olds'
Matt
Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km
This was the reply from Vectrix:
I ordered something as simple as a larger windscreen and a lower seat BEFORE winter 2010. Still waiting though..
I hope I get them before winter 2011 :-)
"doing nothin = doing nothing wrong" is invalid when the subject is environment
whoa, theres some fairly big margins there:
Inrush current limiter is included in my kit (costs ~$5)
PCAN USB is US$255 here: http://www.gridconnect.com/usbcanin.html
a usb extension cable is like $5 off ebay
Matt
Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km
I agree.
265 USD against 1123 USD!
That means that vectrix li+ may cost 3000 Euros to build?;-)
By the way, I could get a pcan Peak for 100 euros, nice deal. BUt It didn't come with the cable to connect it to the vectrix, Anybody know where can I buy it?
Its just a normal DB9 serial cable IIRC.
Matt
Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km
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