Electrifying a Wot 4

[David Ashby - Moderator]

Are you happy with Eagle Tree now Tim ?

[Chris Bott - Moderator]

Timbo I would suggest that those batteries are LiFe's but they are no A123's. The grey line is volts isn't it? This just sags right off from 5.5mins onwards. A123's just dont do this. They generally either give full power or are empty.

My guess is that A123 (manufacturer) are using their nano particle technology to create huge surface areas for the chemistry to take place. Other manufacturers may be trying to catch up, using the same chemistry LiFe (Lithium Iron) but in a more conventional manufacturing technique.

I have another 10 cells in the post somewhere (another De-Walt battery) assuming that arrives, I could send you 4 to try. If you would send them back after testing. I dont have as much use for them temprorarily now the DH88 is kitted again .

You'd only have 2300 mAh, but you'd have all of it! And I recon they wouldn't dip much under 12V in your setup.

I understand if you'd rather get your own, but I'd urge you to try the real thing

[Tim Mackey]

Not entirely - No. I have even tried reducing the sample rate to see if it will reduce its over sensitivity to false peak readings but to no avail. The thing that annoys me is that you buy a piece of kit like this to provide you with easy and clear data - then spend literally days and days fiddling about and trialling all sorts of different methods of using it and so on, which ends up simply instilling more confusion and doubt about things than to begin with.

As the Honda advert used to say " don't you love it when something just works"

[Tim Mackey]

Morning Chris....thats a very kind offer, and I will take you up on it as I would lioke very much to do some proper and consistent testing of all 3 technologies and compare. I will then complie a brief "not too techy type" report and publish the results here on the forum in a seperate thread. Thanks again mate...... I will PM you my address.

I would have bought the hard can A123s if I could have found any !!

Yes the grey line is pack V and as you have seen it falls away horribly after just 5 minutes - I am still learning and experimenting with the eagle tree graph parameters and layouts etc, but should be able to post another couple or so shortly showing clearer less cluttered graphics. Thanks again.

I agree that these new soft pouch style packs are almost certainly NOT A123 manufactured.

 I will TRY and get some more info from the supplier

[Chris Bott - Moderator]

No probs, trust you won't keep 'em too long . And of course, they will only be bare cells.

It does depend on the ebay seller sending them to me etc etc - so I cant give you any timescales yet.

You probably know that when they have stock, they are available from our freinds at Hobby City. Search for  26650A

I've had one of those to add to an existing 6S to make it 7. That is working fine so I'm pretty sure they are genuine.

IF you ever beleive in them, you need a battery like ebay item 170224559108.
But note many of these are US sellers, we avoid those because of postage and duty etc etc.

Of course BRC do a 4S pack made up for £60 !
I am told that Alan Fry at Importechnik is making up packs with balance leads for £11 a cell. But I havent checked that. Or whether they are "genuine". 

[Tim Mackey]

Yes I know the BRC version...it was actually the one I ordered originally, but got sent this version instead in error, so I added a second one to bump up the capacity - these are "only" £40 each . Yep seen the UH ones.

Are you sure your happy to let me solder up a 4 pack from your nice new shiny cells !

[Chris Bott - Moderator]

That's fine, if you can't do it what chance have the rest of us got?

They come tagged together as 10S. I always try to cut the tags in half and solder to those. I've never had a problem with the welds except from my clumsiness. 

I want to keep a 6S tagged intact from the 10. So I'll see if I can get a 4S as well, or maybe 2 2S's.

I have soldered to bare cells OK. Just takes a huge Iron, and as quick as poss. The can end (+ve polarity by the way) doesn't half soak the heat away!

[Tim Mackey]

I really meant were you happy to have me form up a 4s pack from your individual cells

The can end is positive - interesting....wonder why they did that ? I have a huge iron - ooer missus !

[Chris Bott - Moderator]

Yep no problem. I have a couple of 3S's that have been swapped between long sticks of 3 and side by side configs 3 times. So they are pretty tolerant to that too. I could never see me making this offer with LiPo's can you

[Danny Fenton]

I was wondering why I hadn't seen any alerts about this thread, it looks like its stopped mailing me for some reason. Anyway glad you seem to be getting somewhere with the Wotty.

Timbo we have a sort of standard set up for the Eagle tree, ie parameters we set, we could send them if you like, it just means that all our graphs look the same ie scales and content.

It sounds like you need to do a callibration exercise on yours the same as Chris and I had to do

[Tim Mackey]

Great Idea Danny... I find the graphing set up a nightmare to be honest - the options available are ridiculous, with the ones I really want like simply changing the line colours to make them easier to see buried away in sub menus etc - very frustrating. I am now back on testing the EDF unit that will, be going into the Hawk, so the eagle tree has been removed form the wotty. The wotty motor is also going back to the supplier via my Weston trip, as it is pulling far more current than the specs suggest it should. Overall, I remain disappointed with these soft LiFePO4s.

I see from the mag that Puffin are now doing proper LiFe4PO4s in packs ready made up, and not a bad price either !

A123s puffin

[260 Flyer]

"I see from the mag that Puffin are now doing proper LiFe4PO4s in packs ready made up, and not a bad price either !"

At £10 a cell the're not far off ebay drill pack prices!

I think I'll wait to see how you get on with the real A123's before I splash out on some for my old Acro.

[Nick Rigg]

Hi Timbo - I was wondering if I should be at all upset that I bought a charger recently that isn't compatible with LiFEP04s. In other words, apart from the safety angle, are there any compelling reasons to switch from Lipos?

[Danny Fenton]

Hi Timbo excellent price, and they are made up with leads. Well done for spotting them. I need a couple more cells. I had earmarked a couple from Chris but he has gone and loaned em to some one

Seems a shame to dismantle such nicely made pack but I only need 2. Why do suppliers make such small packs? 4 cell max! I have nothing that uses less than 6

[Andy Sayle]

Tim,

If you want some single A123 cells (the hard case cylindrical 2300mAh jobbies) I bought a box of 25 of them fairly recently.  I am intending to make them into some 3s packs for use in various things, and also some 2s receiver packs for my Edge, and my jet.

You are welcome to take a few off my hands if you want them

Cheers

Andy 

[Danny Fenton]

Hi Andy how much and where did you get a box of 25 from LOL

Danny 

[Andy Sayle]

I bought a box from Hobby City.  $17 per cell, plus a bit for postage.  It worked out at just shy of £10 per cell in the end.  The prices at Puffin are pretty good though, especially as they are for a completely assembled pack!

I also took the opportunity to buy a handful of the smaller 1100mAh A123 cell, same type of construction, made by the A123 guys, so they should be cracking cells for receiver packs in smaller models, or where weight is an issue.

Cheers

Andy 

[Tim Mackey]

Yes please Andy....would appreciate that - I need 4 as a minimum. If thats do-able, then I will tell Chris not to worry about posting me any - cheers mate.

[Tim Mackey]

Nick Rigg wrote (see)

Hi Timbo - I was wondering if I should be at all upset that I bought a charger recently that isn't compatible with LiFEP04s. In other words, apart from the safety angle, are there any compelling reasons to switch from Lipos?

Hi Nick - I am still a bit of a LiFePO4 virgin TBH, but I guess for me, the only real attraction is their ability to fast charge at up to 3C ( some even say 4C at a push ).

I am a little disappointed with results so far of the "pouch" pack version as it has poor discharge curve and does not hold V well under load. However, as Danny and Chris will no doubt confirm GENUINE a123s perform better.

They are of course inherently safer and more rugged than LiPo being in a can rather than a flimsy handbag

[Chris Bott - Moderator]

Timbo, I'll hold off sending these cells until you decide with Andy.

If you are changing your motor in the Watty, I'd go for a 670KV tower pro or similar and use 6 A123's.
We are pushing these to 1Kw at full throttle, but using that sparingly as you know. (I don't think you'll look back)

I'm beginning to think in mWh rather than mAh.  Can you tell me if this all makes sense?

4S 4000mAh LiPo will give you 40A for 1/10 hour (in theory) 6 minutes. With Lipos you'll stay away from using all that for fear for the batteries health.  I'm guessing this would be at say 3.4V/cell? = 13.6V
This giving 14x40= 540W  for 6 mins.

6SA123 2300  giving 540W would be at around 3V/cell = 18V x 30A. The 2300 would last 4.6 mins. This is getting pretty close. And you get full power right throughout the flight.

Thinking in mWh  4S 4000mAh cells are 13.6 x 4000 =  5440mWh (except you can't use it all)
6S A123 2300 are 18x2300 = 41400 (that you can use all of)

Just comparing mWh makes for an easy comparison.. 

[Nick Rigg]

Hi - I noticed a little piece of kit called a 'Daptor' sold by a US company - can be used to convert LIPO chargers to use with M1 cells.

Anyone used one of these? 

[Danny Fenton]

Hi Nick,

I have seen these mentioned on the web and read a bit about them. However they are only a real advantage if you have a NiCd charger that can deliver a decent current to feed the LipoDaptor. Most do not.

The biggest advantage of the A123 cells (apart from not catching fire, nor getting fat and useless) is there ability to be fast charged. Chris and I regularily charge these at 10A (4C) and have been doing so for two years ( just over 1 year for me, over 2 for Chris) The deal is that you use 3.6 volts per cell until the current drops to zero. This means the cells are charged. It is as simple as that. NiCd, and NiMh will take current after they are full and convert this energy into heat.  A123 do not do this they just don't draw any more current.

Anyway where was I lol, to utilise the fast charge rate of A123 you need to have a charger that can deliver 10A many Lipo and Nicd chargers cannot do this, and therefore cannot supply the LipoDapter with enough current.

In the long run you are better of buying a charger that can cope with the high currents.

[Chris Bott - Moderator]

Lipodapter  does apparently work well. Note though that you do need to balance A123's too. Not every charge. I do it at home after a flying session.

[Danny Fenton]

Chris is more organised than me, I balance when I think about it - more like once every half dozen cycles

[FlyingAngel]

Hi-I also spotted some LIFePO4 pack at robotbirds. Have a look!