Please post your proposed setups for using A123 M1 lithium cells here.
Number of packs, how they are built, what they are powering, how you charge them, how you balance them etc.
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Please post your proposed setups for using A123 M1 lithium cells here.
Number of packs, how they are built, what they are powering, how you charge them, how you balance them etc.
TERRORHURTZ:
Four 10 cell (34V) packs from DeWalt DC9360 batteries.
Cells are connected with 14 SWG (2mm) copper wire, doubled, soldered directly to the cells.
Wotty speed controller.
Two Bosch 750 motors.
Charging at event (no balancing):
Two 48V 10 Amp power supplies.
Four M1 Lipo Dapters fixed at 37V cut off.
Each pack is charged through a 12V 100 Watt bulb (to limit current to about 5 amps) and a Lipo dapter.
Charging and balancing at home:
Custom PC-controlled rig and software using PCI Analogue to Digital card (National Instruments 6220E)
John
(Message edited by terrorhurtz on April 11, 2008)
If I was ordering more Lipo Dapters, I would probably get them set at 36V, rather than 37V, to reduce the chance of over-charging a cell in a pack if it is out of balance. Wouldnt make any significant difference to the performance.
I havent measured how much charge we tend to use in a fight, but they usually only take around 5 minutes to re-charge.
Obviously you should let them cool down before re-charging.
(Message edited by terrorhurtz on April 11, 2008)
Ka-putt ( feather ).
Two four cell packs ..copper wire, doubled, soldered directly to the cells.
Balancer - http://robotbirds.com/catalog/produc...d=1248Balancer
Hannibalito III, 4cell pack. In use for 7 months.0 problems.
Soldered together with tabs, shrinkwrapped together.
Charger,software updated Schulze Chaemeleon.
Astroflight Blinky balancer
Balanced before and after each event they were used, during the event directly charged.
Drive, Speed 900s 4.5-1 gearratio 95mm wheels with the most grippy mountainbike tyre I could find. Controlled by customized Scorpion XXL.
(Message edited by maddox on April 11, 2008)
John, what can A123s be safely charged at then? 5 minutes sounds crazy speeds to charge them.
Even though i use lipos the methods are the same. During events I will usually charge between 0.5/1C (2.2/4.5A) and around 0.1C (0.4A) when im in no rush.I have charged them on a few occasions at almost 2C (9A). I tend to balance charge all the time, my balancer/charger combo work together so that charging/balancing is much faster and safer.
I have run about 20 cycles through my lipos before they show any signs of un-balance of more than 0.15v per for any cell.
Theres no real point me putting how theyre built and what theyre powering as theyre off the shelf and rated far higher than A123s but thought the charging info might be useful.
http://www.first-products.de/specsenglisch.htmhttp://www.first-products.de/specsenglisch.htm
Suggests 10 Amps max charge current out in the field and 3 Amps on the bench at home.
We charge around 5 Amps, so 2/2.5C. Just depends on the power supply.
I guess 5 min re-charge would be after a shorter fight. Probably more like 10 mins after an average fight.
John
(Message edited by terrorhurtz on April 12, 2008)
This looks promising:
http://www.fmadirect.com/new_applications/10s_charger.htmhttp://www.fmadirect.com/new_applica...0s_charger.htm
One of the few single box 10S charger and balancers.
I like the sound of Displays Individual Cell Internal Resistance.
Good price too.
Supposedly starts shipping next week.
are there any other battery packs like the dewalts with a123 cells like makita or bosch packs
No, Bosch uses a different li-ion
http://www.westlondonmodels.com/product1096/ThunderPower-TP-1010C/http://www.westlondonmodels.com/prod...ower-TP-1010C/
This is the 10 cell charger I use, when you buy it, it will only charge lipo/liIon - but if you buy a data cable you can download the new software for A123s, nicads, nimhs etc.
http://www.westlondonmodels.com/product1098/ThunderPower-TP-210V/http://www.westlondonmodels.com/prod...Power-TP-210V/
and thats the 10cell balancer i use which both link together. You can balance 2x 10cell packs together with that balancer i beleive.
how much power do you think would be needed to run 2 speed 900s and a mag motor on 24v i though i may be able to do it with 2 but what do you think
The speed 900s can be run on a 3 or 4 cell pack. If they have a decent reduction.
The Magmotor, I suspect a S28-150. 2 packs of 8 cells parallel seems the least you need.
And then I doubt it has the stamina to run 3 minutes.
My nicads only expel around 1.2Ah during a 3min fight with a mag on 24v and two 18v drills on 24v.
The problem with running a mag is that you need large surge currents which is why I use nicads. I dont think A123s currently have the ability to give out large bursts of current so you will be looking towards 3 packs.
On a weight for weight basis, A123 is always better than Nicads, unless the ambient temperature is above ~40C.
Matt is planning to use the Mag for an axe which would mean large start up currents, having not used such a mag before how many pack would people recommend. (i.e. how many Ah would be needed - I had suggested 4Ah to him for a 3 min fight)
the amount of Ah is really not that important, more the amount of current the cells can take in short burst without degrading.
You will always be better of with 2 or more packs in parralel than 1 high mAh rated pack.
Soldered 7S4PA123-M1 should reliably be able to burn out a S28-150 magmotor under any conditions before the cells are damaged. With 7S3P the batteries are still likely to outlive the motor. 7S2P, youre quite likely to slowly damage the cells without current limiting unless the magmotor is not working hard enough to get hot. In general, we should be current limiting low resistance motors. A123 wants current limiting more than Nicads, since the stall currents generally work out higher.
If you decide to go with less batteries, you would need to be vary carefull that you could never stall the motor e.g. by fitting limit switches or timing it.
In the last Little Spinner that used the S28-150 we had 3 sets of 1100mAh NiMh battereis in parrellel and to limit the current we had a magnetic clutch arranged so it would slip if the load on the mag got too high and couldnt stall the motor, we did have to add an acceleration ramp to limit the inrush current so as not to slip the clutch when spinning up the disc.
Some Mega Power 960SR chargers and LCB-12S balancers available on ebay.
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=380020491998http://cgi.ebay.co.uk/ws/eBayISAPI.d...m=380020491998
Just ordered one of each.
John, whats your opinion on the a123 packs sold on robotmarketplace?
Looks promising, except I cant see any mention of balance wires in the packs. Triple welded tabs sounds good. Youd have to either buy loose cells, or open the pack and add your own balance wires.
BattlePacks do them with balance wires:
http://www.battlepack.com/LiFEPO4.asphttp://www.battlepack.com/LiFEPO4.asp
but it doesnt say how they are connected - soldered or welded?.
Im now thinking that, unless you have very high current needs and are preapred to lose some capacity, it is better to go with spot-welded tabs, rather than soldering.
1) Welded - lower current capability, unless done well with copper tabs. See http://www.youtube.com/watch?v=5vQTBoHPBxQhttp://www.youtube.com/watch?v=5vQTBoHPBxQ
2) Soldered - higher current, but probably affects the cells, even if done carefully.
If youre just running drive motors, the standard steel tabs (as found in the DeWalt packs) should be fine.
The question also is: does soldering increase the internal resistance of the cell, as well as reduce the capacity? I shall have to do some tests.
What we really need to find is someone that has a nice little spot-welder...
quote:
Looks promising, except I cant see any mention of balance wires in the packs Thats why I sent an email to verify. As soon as I get a response I will let you all know.
It is very interesting indeed.
cant afford em yet
Just posted some findings on the MegaPower Infinity 960SR charger with LCB-12S balancer:
http://www.terrorhurtz.com/a123/MegapowerInfinity960SR.aspxhttp://www.terrorhurtz.com/a123/Mega...nity960SR.aspx
I almost forgot to mention, I never really got a satisfactory answer back from RMP. They said their lipos had balancing wires even though i specificaly asked about their A123 packs. So I replied that I was referring to their A123 packs but I never got an answer back on that email.
The significant finding on the 960SR is that it does NOT prevent individual cells going over 3.7V, even when using the balancer. It just uses the average cell voltage. No better than a dapter in that respect. On a not too badly balanced pack, this is OK, because the balancer should have got the cells fairly close by the end of charge.
But as I say in the piece, you need to keep an eye on new packs, and if they look badly out of balance, then reduce the current, to give the balancer time to do its work. Fortunately the 960SR makes it easy to see if they are way out.
You could always balance first with a new pack before you start charging. Ive found that once the packs have charged and discharged a couple of times the pack keeps pretty level all the way through. Then I can charge and balance on 8A at once.
Apart from that, is it a decent charger for A123 John? How much A can it supply on a 10 cell pack?
Note that you shouldnt try to balance a half-charged pack. That may actually make the balance at peak worse. On a new pack it shouldnt be a problem, but even then its a waste of time - its only the balance at peak we are interested in and tiny differences at half charge can turn into large differences at peak.
Leaving it charging at 0.5 amp will be much more successful.
Yes, it is a very nice charger, they have clearly put a lot of work into it. The only nice-to-have on it would be the ablity to set the cut-off voltage (fixed at 3.7 per cell for LiFe).
The problem with using average voltage is common to a lot of the chargers I suspect. One that might do it better is the FMA CellPro 10s, because it was designed as an all-in-one solution. But the CellPro only has a small text screen and I think being able to graphically see the balance is much more important.
John, What is your view on balancing by discharging each individual cell in a pack to a common target voltage?
That might be OK, as long as the target is above 3.55 Volts i.e. the cells are over 90% charged.
It would still take a while, a) because of the voltage drop acrioss the cell at any significant currents, but mainly because b) the cell voltage seems to exhibit a considerable amount of hysteresis, particularly at higher currents. In other words, after a change in state-of-charge, it takes a while for the cell voltage to settle to its true value.
Well RMP does not supply balancing leads with their A123 packs.
From the Australian forum:
quote:
Got some premade A123 packs from RMP, a bit disappointed with them . Ill have to pull the heatshrink off them to balance them as their are no balance connectors