Vienna aka Viennese

[biscuit]

I'm reading the lithium conversion/add-on threads rather carefully and thinking in terms of my little Vienna chair which I love, as it fits indoors and in the car & shops very nicely, though it is a pig outdoors and lets me down at every opportunity.
My pair of lead bricks is 17Ah and I bought a new pair recently to go in my battery box. I never want to bother to replace that again, but I do want to use this kind of chair.

If I were to get these cells http://eclipsebikes.com/product_info.php?products_id=90
and string 8 of them in series I'd get a 10Ah battery, am I right?

A pair of those strings in parallel would exceed the present Ah. For like £250.
I'd need knowledge built up like I see expresso did - I think it's all to be found on this site already - also various bits and a suitable charger (and figure out how to connect the new battery to my chair and the charger.)
Does that sound like a reasonable place to start making my little chair work reasonably?

My laptop turns out to have died since I last used it (2016). Bloody thing was always demanding I do this and that while it was working, now I want something from it it's dead, so programming my chair is a non-starter until that is sorted. So if anybody knows of a reliable way to programme a VSI control pod using an Android mobile, that would be good too.

[Burgerman]

If they will physically fit, then it would be an improvement. Better to fit more Ah really though. As it is you will get about 60% more range.

[biscuit]

I can't add voltage as the chair would not go, its pod would give an error message.
I think that means: I don't get that benefit, but
I benefit from lighter batteries, longer life if I get the charging right, quicker charging and bigger range if I put in LiFePO4 cells as 8S nP, n being according to how much space I have
Am I right, particularly about the benefits?

My lead bricks are 12V each in series in an off-board chargeable box. Does the VSI know about that? Is it necessary or beneficial to keep that voltage?

I also have a broken Vienna and Intentions to do various things to improve its driveability while keeping its frame. First things first though, and I have usable chairs meanwhile.

[steves1977uk]

A control system doesn't care about the battery chemistry. Also you're not adding volts, it's amps at the same voltage. For eg. I had 2x40Ah 12v lead bricks in my originally, this was replaced with a 24v 75Ah LiFePO4 pack which fitted in the same space giving me a 2x-3x increase in range.

Steve

[biscuit]

If I put in (for argument's sake) an 8s of LiFePO4s it will actually be 8x3.2V=25.6V. Is the VSI pod sensitive enough to freak out because that is more than 24V? I can't remember if my lead bricks were more than 12V each when they arrived. I remember years ago having a torch that stopped working with rechargeachable AA batteries. What is the tolerance for the difference between the actual and nominal Voltage? How does that work?

[steves1977uk]

Usually it's 30v+ before a control system trips due to an excessive voltage. A Lithium pack is above 25.6v until you get down to the last 10% of remaining capacity, which then it falls off like a cliff!

Steve

[Burgerman]

32V for Dynamic. 35V for PG Drives. And if an 8S pack reaches that voltage you already killed it!

[biscuit]

Can someone please explain C rate or point me to an earlier explanation of it, please? It keeps coming up in various threads as an important thing that must be high enough - for what, idk. And how to tell from battery specs I also don't know.

[Burgerman]

C = Capacity.
The capacity is the number of Ah a battery has stored.
If you had a 100Ah battery, you can take in theory, 1A for 100 hours. Or 50A for 2 hours. Or 100A for 1 hour before it is emplyt.

So if you have a 50Ah battery, and you pull 50Amps of current from it, thats 1C.
If you pull 200A of current from it, thats 4C. Because you are pulling 4x its capacity in Amps from the battery.
If you pull 25A from it thats half C.

Lithium batteries hate being fully charged, or worse charged too high even by a tiny amount.
And hate being empty, so best kept above 80%.
They also love low currents, or low C rate charging and use. The lower the C rate in use the longer they last.

So high rate cells like headway max allowed 10C, max in use practical 3C, best lifespan .3C, And large packs to keep this lower, help them to give a long service life.

[biscuit]

I'm gradually gathering the parts and know-how for conversion to lithium. So far I've got as far as ordering a PL8 and a bunch of the orange things for holding cells. Maybe over-capitalising for a Vienna, but I love that little chair, plus it'll be good to try this and more worthwhile than papercraft - I can use the papercraft embossing tool for heat shrinking plastic.

I'm more or less following expresso's threads and the threads he used for guidance. I'll do this slowly because I am ignorant and I have to budget. Also because this is not what I am used to, so I am nervous about it and I'm putting it off!

I will use the lithium instead of my lead pigs, not as well as them, if I can manage that. At present the battery - controller connectors are plates, but there must be a way to bypass those. I can not see a way to use both batteries.

Question: On one of my VSIs the charge lights are gone out, so it's like a car with a leaking fuel tank and no fuel gauge, it's nerve-wracking to drive! But the charge indicator would be unreliable anyway, I believe. Is there an alternative battery state indicator I can get, that I can use on board with LiFePO4 batteries?

[Burgerman]

With lifepo4 theres no easy cheap way to have a battery gauge. One reason we tend to fit 55 or 70 mile fuel tanks! Drive as long as you can stay awake. Go home, and charge!

You can monitor cell voltages individually, with a tiny monitor, and it will only really tell you when to stop. Or at 90% done...

Or an expensive Ah meter. So that if you have a 70Ah lithium you are half distance at 35Ah. Except you should really not ever fully discharge it so turn back at 30Ah.

[biscuit]

An optipower 1200W link below. Is this a good power supply for a PL8?
https://www.fast-lad.co.uk/store/produc ... s_id=39761
Is it too much or too little power?

[steves1977uk]

http://www.coolice.co.uk/cccases/coolice-psu-s.html Half the price! I have been using a 2400W one with the PL8, no issues!

Steve

[ex-Gooserider]

Question: On one of my VSIs the charge lights are gone out, so it's like a car with a leaking fuel tank and no fuel gauge, it's nerve-wracking to drive! But the charge indicator would be unreliable anyway, I believe. Is there an alternative battery state indicator I can get, that I can use on board with LiFePO4 batteries?

I've been asking the same question, and according to Will, who is another of our lithium experts, a cheap 4 digit voltmeter can be used as a guide... (I have some on order, 4 digit, 0.6" high LED's total package size not much more than the LED size, about $3.00 US each, off eBay....)

He says that while the steady state voltage reading on a LiFePO4 pack doesn't change very much until it is almost to late to make any useful distance. However if you keep an eye on how much of a voltage DROP you see while moving, and the length of time it takes for the voltage to recover back to normal, it will (with practice) give you a feel for how much capacity you have used... As the pack discharges, you see more drop, and a longer recovery time...

Same thing would apply to lead bricks, except you will see more of a drop in voltage and longer recovery times as they discharge... Remember, those LED charge lights are really just a dumbed down volt meter without the numbers....

ex-Gooserider

[biscuit]

My dumbed- down voltmeter (the one that "works") goes down to orange as soon as I push the chair's top speed.

Anyway the Viennese project is on hold atm, pending sorting out a few other things around here. It'll probably remain as an indoor chair, so its lead bricks will not bother me.

[biscuit]

The Viennese project is still on hold, probably indefinitely as it's an indoor chair now. But I tweaked the steering , which I had thought was fine, and now it's a much smoother ride and I don't have little prangs and bumped knees when I turn around in a narrow space. All I did was get rid of the irritating standby mode and the turn delay, turning in reverse was 70% and I changed it to 100%, same as turning forwards was. At least, that's what I *think I did with the turning.
Always in the past I'd just thought my own steering was a bit off.
I look forward to achieving great things with my Salsa R2 tomorrow. I'll be happy if I can manage to stop its crazy manoeuvring and maybe its tail wagging on the straight.

[Burgerman]

viewtopic.php?f=2&t=8035

READ very carefully. And copy to make a good start.

[biscuit]

I'll likely have questions. Some settings are mysterious on the Viennese's VSI, so I'm guessing there will be mysteries in the VR2 as well.
But my brain is fried atm, so questions - if any - will wait.

[Burgerman]

Compared to many they are super simple and almost clones of each other so you should be able to almost copy your favorite settings across to the VR2.

Make sure that the four important ones are set to max. 100.

Turn Acceleration
Turn Deceleration
Minimum Turn Acceleration
Minimum Turn Deceleration.

Also best to set reverse acceleration to 100, and reverse deceleration to 100.
Set forward acceleration to whatever you feel comfortable with.

It will then steer properly. If you do. No bruises.

[biscuit]

My lead pigs in my Vienna have died already. They were vrla batteries. Maybe my Pihsiang 3A charger is the wrong voltage for vrla.

Generic 10A charger will charge at 3.65v x 8 or a too high 29.2V and then the BMS will keep switching the 10A on/off repeatedly for a few hours while it murders the cells a bit, as it attempts to balance them with inadequate 50 to 100mA balance circuit and repeatedly allowing the high cells to reach 3.700v or more over and over... Enjoy! Best not to watch it do that!

I've been looking at a pair of 12V drop-in LiFePO4 batteries for my little Vienna, because of the weight of lead, not the performance. That little wheelchair . I'm sure they must take a battery box and build a chair to fit it.

It's easy to find fairly cheap-ish LiFePO4 mobility batteries, but more of a problem to find a suitable charger. On eBay all the 24V chargers have an actual output of 29.4V which is too high, if I understand correctly. I think that charge Voltage is for lipo, not LiFePO4 batteries. The drop in mobility LiFePO4's have a charger included and they tell you not to use anything else (the batteries would be a pair in series in a box, so I'm not too sure how that would work) I'm guessing it's going to be 29.4V. so that would be a double whammy against those drop-ins

Not one of the mobility chargers I have around here has any specs or online info, they just say output is 24V. And the same goes for mobility chargers for sale. I found a 28.8V charger online, as it is not a "mobility" charger, there are some specs but no XLR plug. Would that help increase the longevity of my batteries? I'd need to put an XLR plug on it (soldering - ugh ) and then I think my Vienna would be p&p and portable.

[biscuit]

Here's the page I found with a table with charging voltages for lithium batteries.
http://www.cobox-ebikes.com/296/basic-u ... fepo4.html

[Burgerman]

Some of that is correct. Some is dumbed down. Some is overly simplistic. But its generally correct in most places. Doesent allow for internal resistance, voltage drop under load, or proportional voltage based current control such as we use in a powerchair, etc. So a bit too simplistic. Applies to small battery packs mostly.

[biscuit]

Here's what I saw: batteries
https://rover.ebay.com/rover/0/0/0?mpre ... 2794911393 they say you have to use their charger that comes with the batteries, but I think maybe not. My guess is it's a lipo charger.
Instead, this charger
http://eclipsebikes.com/advanced_search ... er&search=

[Burgerman]

You dont want eiher of those. I dont know where to start... Its too low Ah, and you will gain little. Its using a BMS that will cause problems and a short lifespan. They claim 1000 and you wnt get half of that so no gain over a 22Ah lead battery that fits the same space. And 2A charger is because the BMS cant cope with more.

https://www.ultramax.co.uk/media/catalo ... 2-tech.pdf
Max current is only 20A. So the BMS inside pulls the plug to protect the 1C cells inside every time you try to take 21A from the battery. And that happens a lot!!!

Maybe by reading the first post here carefully!!!

viewtopic.php?f=2&t=1813

[biscuit]

It leaves me with the question, what is a BMS for?? It looks from that post like it's no use whatsoever, but it must have some function.

[steves1977uk]

A BMS is like a poor mans PL8 with weak balance circuits and very limited configuration. Best to avoid!

Steve

[Burgerman]

Do you know what volts and amps are?

Yes they are of some use. They will replace a battery that never needs to exceed 20A in discharge. Possible if you are lucky in a tiny scooter? Or a UPS, or a lawnmower. But since 22Ah lead batteries can do this and more too, and are larger in capacity, then its basically a massively overpriced swap. With no real advantage. Other than to say you have lithium.

The whole point of fitting lithium is to be able to take advantage of 2 things.

1. EXTRA AH (much more range) in the same Volume. It means that I can replace the 80Ah lead battery in my new salsa chair, with 180Ah instead. This means that I get a massive range advantage, and because there is more Ah the cells all get an easy life and will last 10 years. Fitting the same Ah as lead, or less, does not achieve that.

2. LONGER LIFE. Fitting MORE Ah in the same space, and using high rate cells, means that the battery can have adequate power for your max load use. And not be limited in Amps. It also means the cells have an easy life and last a decade.

What does the BMS inside the dumb lead brick do?
It allows people marketing batteries to sell you a "lithium" battery without most of them coming back in a week destroyed through ignorance. It also allows you to charge with a simple dumb cheap non cell balancing charger. But its does this badly shortening cell life. Meaning that instead of a 10 year life and 2 to 5 thousand cycles, you are getting a best case 1000 cycles, and will see half that in reality because the small Ah means the cells are worked much harder. And they really dont like it!

The BMS also cuts power like a switch, if you exceed 20A load when trying to accelerate or climb a curb, or turn in place with a wheelchair. And you then stop dead. Why do they fit them? Because its the only way to stop people putting a too small lithium battery into something like a powerchair which would otherwise kill the low C rate cells. In other words it allows them to sell lithium batteries to people that put them in the wrong places. And to allow cheap dumb chargers to be used.

[biscuit]

Oh dear. I'd be one of those despicable lot if I used my shopping list!

I can well believe it is pretty much a con.

Benefit no 3 of lithium is the weight. Nobody in our house likes to lift my little battery box of lead batteries. It's about 12kg. With those 2 Li batteries it would be less than half that. It would be manageable. I don't have the need for speed or the energy for range. So it's longevity/cost vs weight.

[steves1977uk]

12kg is nothing! They should try lifting 2x24kg batteries that's in my F55S chair which I'm hoping to convert to Lithium to get the weight down and since the Haze EV batteries are knackered!

Steve

[biscuit]

Lol 12kg - it is possible to lift it, just not nice, wrenched muscles & sore backs etc. 24kg - no hope! 24kg X2 - no hope ².