A123 Battery Pack Advice

[Mike Johnson]

Tom

 I also fitted the Wemotec fan, no green putty on mine must have been good right out of the box,

I am using Flight Power 4350Mah 4S in mine, I know thay are heavier, but give great duration, the only other mod I did was to put the Rx up higher to allow the battery to go back further, I am also using a Spektrum 6100 Rx and have not run out of range yet!!!!!!

 Mike

[Tom Foreman]

Mike,

the large Flight Power will presumably run a lot cooler, again I too have moved the RX into the canopy above the battery. How did you get on with the CoG? I'm going to add some lead to the tailpipe to balance out the A123 5s1p which weighs approximately 380g. How much does the Flightpower weigh?

I'm not too bothered about duration, 5 mins is OK with me, its the hot batteries that I'm hating!

Tom

[Mike Johnson]

Tom

 They Weigh 453gms with connectors, I have not checked the C of G, but it fly's and glides fine, the batteries do not get hot at all, they are 25C so pulling about 50amps they are well within capacity which is 108.75amps at 25C which is the low end of the capacity, max is 50C bursts which is 217amp, don't think the Twister will get there.  Mind you when I put them with my 6S to make up 10S in my Extra they are close too the 152 amp climb out.

Mike

[Tom Foreman]

Cheers, with any luck I'll have a soldering iron waiting for me when I get home, all depends on my naughty step daughter getting out of bed and answering the postie. Otherwise it will be an early divertion to the postal depot tomorrow morning on the cycle into work!

 Tom

[Mike Johnson]

Good luck with the soldering, I did not have any problem making up my A123 packs with a 75watt Iron from the DeWalt packs, just measured the Twister and I can get 4s in without problems, but the fith cell would have to be on top, unless I carve out the inside of the battery tray, I think I will just sitck with the LiPo's for now and keep the A123's for my Rx supply in my bigger machines.

Mike

[Frank Skilbeck]

Chris Bott wrote (see)

There could be Frank.  We set the LVC to off or as low as we can set it.

What sort of current will you be pulling? The A123 volts do depress quite a lot..

You could change to a bigger prop while on A123's to keep the power the same.

At the moment on a 4s lipo my peak amps are around 40 amps and 15v at WOT, but I've stopped using full throttle even for take off and usually pull less than 30amps during the flight. I swapped from a 13 x 6 to a 12 x 6 prop mainly to reduce the torque reaction on take off. So if I'm pulling 30 amps or so what volts can I expect out of a 4s A123 pack.

I would look at 5s but wanted to try a premade pack first.

[Chris Bott - Moderator]

From memory I think at 30A you'll be at around 3V/cell  so only 12-13V I'm afraid.
After charging to 3.6V They seem to drop to around 3.4V without use.

Last night I was measuring an 8S pack which depressed to 20.5V at 50A

This is where a direct swap is usually disappointing.
To get the Watts up, a bigger prop is used and current has to be even higher, reducing duration again..

They have so many advantages, here we are hitting the downside.
Let's keep telling Puffin that we want 5S and 6S packs.
Could you use a 2S and a 3S ?

My 8S pack is doing over 1KW which I'm using in a 60 sized warbird.
They are safe, abuseable, and I'll be charging on the field in about 15 minutes between flights. 

[Frank Skilbeck]

Chris

Thanks, I'll get a 4s pack and give it a try on the ground, if it's not quite upto the job, I can always use it in my Fantom and Twin Star which are using 3S lipo's.

Shame nobody is doing a ready 5s and 6s packs.

[Danny Fenton]

Yes we have been saying this for a couple of years, I have never flown on less than 6 cells A123, its like trying to use a couple NiCds, you have to get to a decent number before it works.

[Mike Johnson]

A DeWalt 36volt 10S pack is just two 5S packs waiting to be split and have leads soldered onto the tags left after you have split them, already welded together in 5S, then cover them, come on guys its not that difficult.

 Mike

[Danny Fenton]

No Mike it is not difficult at all to some of us but there are others that are not so clued up. If we want this technology to become more mainstream, and the prices to come down accordingly then we have to get as many people on board as possible.  The more people that use these then the more chance we have of chargers and ancillary bits coming along, when we started with A123 there were NO chargers at all. so we not only had to make our own but dsesign them too.

The UH cells come with tabs welded on so you can make packs in any size you like. the JST balance leads are more interesting to source as larger ones are quite elusive, but again it can be circumvented by using multiple plugs as I have on my 6 and 8 cell packs.

Not everybody is even aware that it isn't ALL De Walt 36 volt packs that contain LiFe cells..............

[Chris Bott - Moderator]

I agree Mike

All my A123's have been from Dewalt packs. Its easy to solder to the welded tags.

But for some, dipping their toe in the water, the Puffin ones are very good value.

If you pay £80 for a 10 pack (inc post) then add cables and balance connectors and heatshrink, then it comes close to Puffins prices.

Bye the way, do you have a contact for heatshrink big enough for 6S and 8S bricks?
I cant find any anywhere at the moment.

[Mike Johnson]

Danny

 I have not found any DeWalt 36volt packs that aren't LiFi's thats news to me.

All the packs I have are made up of combinations of ballance leads even the bought one's, I don't think anyone supplies their multiple packs with just one lead at least I have not seen any above 4S with one ballance lead.

Chris

Yes the puffin one's are good value and are redily avilable, its a good way to start.

As to the shrikwrap I have only found 105mm from BRC, though I have not looked for any bigger, they take a 4S pack veritcally, you have to cover the end's yourself with somthing, I use fibre reinforced tape, I am sure a trawl thought the internet would bring results for larger shrinkwrap.

 Mike

[Danny Fenton]

Hi Mike BRC do up to 6 cell balance leads if you need them, the De Walt packs you need to use are the 9360, 9280, 9180. Which are 10 (36 volt), 8 (28 volt) and (18 volt) 5 cells respectively.

Mike are you still finding packs on Ebay? I haven't spotted any for a while, which is why I got some loose ones from UH and a single cell from Puffin recently. Timbo ordered some from BRC but got sent non A123 cells (liPo style softpacks).

Cheers

Danny

[Mike Johnson]

Danny

 Must admit I have not looked lately for the DeWalt packs on e-bay, but have been looking for the B&D 1100Mah packs to make up some smaller Rx packs, seems thay are even more elusive than the 36volt.

Mike

[Danny Fenton]

LOL UH, Our chums in Hong Kong are doing them apparently, a friend has bought some. I have not tested them myself so cannot comment on whether they are genuine A123 or how they hold up under scrutiny. But the 2300 from UH are the real mccoy thats for sure.

If you get hold of some let me know

Cheers

Danny

[Chris Bott - Moderator]

The 1100's are in the B&D VPX   equipment which I don't beleive has made it over to the UK yet.

The yellow ones on UH could well be genuine. They look exactly like the ones I've seen on the web that have been taken from VPX batteries.

 Interestingly, the button on the 1100's is positive, like conventional batteries.

[Mike Johnson]

Chris

 That is the problem, you can buy a whole unit including the saw and drill with the VPX pack but not just the batteries will keep looking, if I find any in Europe at a sensible price I will post here.

Mike

[Frank Skilbeck]

If I was making up my own pack I'd probably go down the UH route, but considering the Puffin packs come complete with a balancer lead etc they seem good value.

Note on my 4s plane I'm not sure if a 5s A123 pack would fit, it would either be too wide or too long, the battery bay is only just big enough for a 4s 3200 mah LiPo

[Mike Johnson]

I don't know what you are trying to put them in, but on my Twister I can get two x two in line and one on top, I have tried this in the battery compartment and it fits, just have not bothered as I am using a 4S LiPo @ 4350Mah at the moment may try it later when I break open another DeWalt pack that I have.

 Mike

[Frank Skilbeck]

I was thinking of my E Flite Beaver, you thread the battery in via a hatch on the bottom. The battery box extends into the cowl and a 4s lipo is quite a tight fit. The plane was designed for a 3s or 4s lipo and a 4s 123 pack would fit OK, but I couldn't make it any wider, longer or deeper.

The motor I've fitted is a 750kv motor, but as I say it has more than enough power on a 4s Lipo.

[Tom Foreman]

Well I've put together the packs, just need some flying weather to test, unfortunately have had to add 4 oz of lead to the tail of my MPX Twister jet to get it all to balance. AUW is now 1200g (42oz). The motor pulls 50A giving me 630W, similiar to the 4s1p 2600 LiPo setup. But I am now carrying 200g (8oz) extra weight so hand launches should be interesting . Photos of soldering packs attached.

A123 materials

Pack glued together

Pack in homemade jig ready for tinning

Not pretty but functional

[Tom Foreman]

Ready for tinning battery bars

Battery bars, balance leads and discharge leads all done

Fibre glass tape applied

2 finished 5s1p A123 packs, weigh about 400g

[Tom Foreman]

Charging 1 pack

Looks like the cells survived my soldering OK!

Internal resistances look good, better than my LiPo's

Success! The pack will pull 4.5C in auto mode.

[Danny Fenton]

Hi Tom, keep us up to date as to how you get on with them?

I am not familiar with that charger, what voltage does it charge the cells too and whats the maximum charge current?

I have just started a Brian Taylor 69" Mustang for 10/12 A123 and if weight allows a 1lb sound system.

 Cheers

Danny