PINNED - Lithium battery conversion/info

[Burgerman]

Those are good quality cells. But way too small Ah for powerchair use.

That's a tiny 2.3Ah cell x 5p x 4s so totals 10Ah and 12 volts. For a powerchair you need to be looking at 2 to get 24 volts.

Once you have 2 of those you then have just a 10Ah 24v battery. Way too small for a powerchair. That typically has 24v and 70Ah to start with, and the whole point of lithium is that it can allow MORE Ah to fit the same space.

You need to be looking at about 1.5x the Ah of the lead battery you are replacing to see any real benefit that lithium batteries are capable of.

In other words. you would need 30 of those complete battery packs on that page...

[mous3]

2x 6cell chargers?

Well if you used 2 separate power supplies that were FLOATING, ground wires not at the same potential you could charge it as 2x 4 cell packs. Or charge first 4 cells, then the other 4 cell later on.

But not really practical.

And ideally you need to fully charge all your new cells, and soak charge them, so they are FULL. Then store them for a week or 2. To find self discharge rates.

Floating ground wires ? What do you mean by this I have 4 outputs on my psu they are independent. Or I can go direct off mains for one and psu the other charger.
Soak charging I get and iv started got 12 cells full before having to go off for cruffs all labeled, will do the last 12 on Monday
Defiantly not the most practical solution. Charging as 2x4s4p the plan idealy is 1x8s4p less wires for balanceing

[mous3]

And today's fun working out how the (duck) to fit them in to a 28cm x 16.5 cm x 25cm box. So glad I am using the 15ha cells. 8s 3p is easy using the plastic blocks and bars supplied however the 4th parallel group will have to sit down the side at odd angles and not using the building blocks time for the hot melt glue gun and making up flexible wire bus bars but as these cells are bolt together so I can't solder direct to the battery terminals I'm a bit stuck.
I know of the tags with holes in them that you find crimped on to automotive electrics but are they up to the job if soldered and crimped to heavy copper cable? And if so what are they called? If not any ideas as the remaining cells will interlock at about 55deg from upright so no terminal will be totally parallel to another.

Each cell is 18cm by 4cm in its holder

[woodygb]

Ring terminals.

Heavy duty.

http://www.barden-ukshop.com/sto001---1 ... 1200-p.asp


http://www.barden-ukshop.com/stop-end-t ... -162-c.asp

[mous3]

Ring terminals.

Heavy duty.

http://www.barden-ukshop.com/sto001---1 ... 1200-p.asp


http://www.barden-ukshop.com/stop-end-t ... -162-c.asp

Thank-you xx your a star you and BM deserve a medal

[Burgerman]

Floating ground wires ? What do you mean by this I have 4 outputs on my psu they are independent. Or I can go direct off mains for one and psu the other charger.

Your power supply may have 4 or more actual connections but they may not "float" and as such the NEG connectors may well be all tied together internally. Or not.

If they are, and you connect two hobby chargers to these 4 connections, then the chargers NEG connections are also tied together.

Now,,, If you connect those to charge a 24v 8cell battery, as 2x 4cell batteries, then these two BATTERY negatives are about 14v different... One of them is coming from the centre of the battery pack.

So when you plug in the battery or chargers there will be a very big bang and thousands of amps will try to flow as you short out 4 cells... Please tell me you understand this! Or there will be smoke.

[nandol]

olá Woody and fellas,also in that store a new CTEK for LIFEPO4...http://www.barden-ukshop.com/ctek-lithi ... 3043-p.asp

[nandol]

http://www.ctek.com/pt/en/chargers/LITHIUM%20XS

[Burgerman]

Unlike the hobby type chargers that correctly throttle back to allow the accurate balance circuits to keep all cells below 3.600v during charge, this just relies on some sort of BMS to be fitted, to screw the job up for you... http://www.wheelchairdriver.com/BMS-lithium.htm

So it does almost exactly the same as every other Lead acid CC/CV (dumb non balancing) battery charger does. Fail.

For any charger to PROPERLY charge a lithium pack you must have built in cell balance capability. That means a 24v battery needs 9 battery connections - not 2! (although technically it needs 11 to do it right).

It also adds a further 6 marketing bullshit "stages" we don't want...

[mous3]

I get it now about my power supply. I have been having some very short blunt emails to hobbyking and scsexpress parcels and my new charger magicaly arrive at my mum's this lunch time VAT free.
So I can charge the completed pack. I am just finishing charging the individual cells on my small hyperion charger as my second one dose not float the cells it just witches off so it is taking ages.
In about 3 weeks I will take all the cells and chargers and a power supply each to my friend who will help put it all together and fit the balance leads he is more than qualified to do this in his sleep, if we have time he will take a look at the left motor se if we can get a few more months out off it.

[Burgerman]

Qualified. Usually means "trained" or has bits of paper. But little idea!

The non Hyperion chargers had a charge algo that I didn't have anything to do with.

It probably just charges and when the amps fall to some random pre determined point, stops charging... Most of them do that.

Works ok (ish) on low resistance LiPos. Doesn't properly charge LiFePO4s - they need at least an hour, preferably 3, AFTER charge "ends" at the same fixed CV 3.600v point, until amps drop to zero. Or almost. The Hyperion all do this. As in, they say, "end" and then 3 minutes later continue charging anyway... It lets you "fly" at about 99 percent charged and says "done". But on LiFe batteries the extra time is needed, to completely fill, and fully balance the cells. Its called soak time.

[mous3]

I'm leaving them floating for about 2hrs.
As for qualified friend yes he has degree in electronics design but the 27 years as an RAF sparky and Lockheed systems engineer and the 15 years I have known him in which he taught my to fly rc aircraft of all sorts and how to build them from starch I think counts for way more than his OU degree. he has built packs of cells from the very first 5c cells to his 12s 8ha powered phantom for with no commercial pack would fit and balance, it has so much grunt he tail stands it for take off and when the turbine boys ask what he is running he hovers tail down cos he can.

Just LiFe cell are new to us as you wouldn't bother with them in rc aircraft and like so many of us on this sight I never expected to become reliant on a wheelchair.

[Burgerman]

Been there with DFs. But really, get a turbine! Different world.



This is my biggest one. About a gallon a minute...

Its a Gas turbine starter for a real phantom F4 converted to a pure turbojet for kicks.

Its very very noisy! Its sat on my transfer board. About 12 inches diameter, about 22 inches long.



Note little home made 4 inch diameter model plane turbine next to this monster...

[Burgerman]

Small pear for scale sat on top.

I also fly these...



That goes a bit. And is even louder!

[Burgerman]

I got thrown out of all my local model clubs. They are all of the opinion that I a bit mad. And I fly rather low. Never have much with a throttle. They are running, then they stop and go silent.

[mous3]

LOL but we stay up longer heli_bee (rcgroups) my joke project is a Burt Rution protius for the st athon jet meat but I had a bin bag landing dam sheep after an unpowered test flight of 2hrs. I have no A test so flying under the landing path of heathrow means I have to fly on a buddy so i just go slope a real test for the average wheelchair.

[Burgerman]

I have no A or B (refused on account of I refused to be tested by people that were about half as capable as I was) and have been flying pure speed machines since I was about 15.

Now 53...

I have done competitive "organised" pylon racing, (too slow - many rules) and outright daft overpowered and over revved for about 35 years.

I have lots of ducted fan motors here. Always fitted with a prop... Best way to get power/speed. If you could keep one on (prop), no carbs just venture, crankcase pressured fuel, 70 percent nitro, etc. They make tons more power than conventional "plane" motors and run at about 30k rpm. When I turn up at the field most normal folk go home! Or put in ear plugs.

If its not unbelievably loud, 30k rpms, stupidly fast, spitting flames, or plain O my god what's that? Then it doesn't interest me. No scale. They are toys.
Performance above all else. As light, and clean as possible with stupid power levels... No throttle. That needs a servo. Servos are heavy, makes it slow...

If you cant let go, straight up, and wander over to get your transmitter from your car later, its a toy!

You may wonder why I took up drag racing bikes. I love speed and power! Wheelchairs sort of took the fun out of things.

[mous3]

Yeh l still jump of clips though race down hills at 60 mph one stupidly skiny bits of rubber with effectivly no brakes and very " interesting" steering.
I have allways been drawn to scale flight quiet stuff slope aerobatics the odd. I have autisum of some type loud gives loss of motor control not conducive to flying but i love to hear the turbines just expect me to be an uncordinated non communicating heap.
On the LiFe around I'm on my last 8 cells

[Burgerman]

You can charge 2, 3, 5, or all in parallel you know? Just connect all together. As long as all held at 3.600v for a while.

[mous3]

Duh that would have taken just one day.

[Burgerman]

http://www.youtube.com/watch?v=TWfph3iNC-k

When are you going to try this?

Jeb Corliss doesn't realise it, but he needs my large Solent Gas Turbine on his back!

[mous3]

I do not think that would be compatible with my babe joints I have hjs It's a problem with conceive tissue and coordination

[nandol]

Been there with DFs. But really, get a turbine! Different world.



This is my biggest one. About a gallon a minute...

Its a Gas turbine starter for a real phantom F4 converted to a pure turbojet for kicks.

Its very very noisy! Its sat on my transfer board. About 12 inches diameter, about 22 inches long.



Note little home made 4 inch diameter model plane turbine next to this monster...

Ói John...with that phantom stuff,give a ride to " frankie sinistro " and...http://www.youtube.com/watch?v=qtFBRJFN3p8

too much sunshine here...my face red lobster have a good weekend fellas

[mous3]

We know he's gone a little to far in the quest for speed when BM powers one of his chairs with one though a turbine power hand bike would be so cool drivers wouldn't be so keen to get to close at junctions for feed of blistering their paint work and melting bumpers.

As to 24v LiFe conversion hers a few tips I have learnt make up one 3.3v string of however many cells you are using do not use the orange building blocks cos they are a pig to get back off for the actual build then charge the whole lot In one go this will save you days. This will mean leaving them floating as described by BM. label your cells with a fine tiped permanent marker or labels and pen .

[Burgerman]

This snt like the little model turbines, I have a couple of those, its LOUD! And chucks a lot of dust/heat up...

[mous3]

I know It's not a toy ! Just that it would make a potential power plant for disabled friendly drag bike,Trike life after all only has the limits set but those who has no creativity.

[Burgerman]

Doesn't have enough power for that.

I do know where there is an Alison turboshaft helicopter engine in a shed though. It would convert to a pure thrust motor easily enough.

This one I have is a Plessey Dynamics Solent gas turbine (A starter motor!)
As used on this Kart here:

http://www.youtube.com/watch?v=-1lya-SU_0Q

If you read the caption, it says John Williamson (me) is the guy behind this.
That's not true. I do know the guy whose kart it is, only because he also uses a Plessey Dynamics Solent turbine and we discussed oil systems for it...
This kart eventually did 137mph I think from memory after a very long run up. So nothing like enough power for drag racing. They only make about 82 shaft HP.

[Burgerman]

http://www.youtube.com/watch?v=R8mXh6THEKo

These things are way louder than turbines and more fun... And cheap to build. And cheap fuel. (Mix of Kerosene and propylene oxide)

I have one stuck on my ceiling here in my room...

[mous3]

All good fun but not practical for powering the average power chair sadly.

[Burgerman]

Yep it is. For drag race use.

Bob madox will build you a couple of custom pulse jets. See here: http://www.youtube.com/watch?v=Lf63jbhcphY