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Post by flydiver on Sept 17, 2009 15:20:04 GMT 1
Not a big reason to chime in. Good explanation.
Dillzio-no need to cycle lipos. These are not NiXX and outside of a possible gentle 'break-in' for the first few cycles there is no benefit to doing this. There are many reasons for a lack of dishcharge on lipo chargers but that is a main one-not useful. One more discharge is just one more cycle wasted. Taking them down to a low voltage (like NiCad) is not beneficial. Actually, taking them down to 50% and then re-charging is better.
IMO the exception is unsused lipos. I personally try to keep mine at 50%, in a zip-loc in the fridge. The longer they will be sitting, the more benefit from this. This is a bit compulsive. If they will be used frequently don't worry too much about it.
You are not doing them any favors at all by taking them down to 2.8 under load. Won't kill them but the flogging it is a bit harsh in the long haul.
The LVC on the Cub is about 8.8-8.9v-a bit low IMO but then I think almost ALL ESC LVC is too low. The ESC firmware has not kept up with lipo advances. The only ESC I know that can be programmed to a safe LVC is Castle, but I don't know them all.
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Post by ginginho on Sept 17, 2009 15:50:35 GMT 1
Ah, thanks for the feedback. It seems I am being a little harsh on my poor little Lipos. I've never actually had the resting voltage on any of the cells below about 2.9 though (and that was only for a minute) so hopefully I haven't done them any damage. My Zippy 2200mah 15Cs say on the label not to charge them at over 2C. I've set the charger up to charge them at 2.2 amps (1C) for the normal charge cycle, and 3.1 amps (1.4C) for the fast charge cycle. I though that since the specified maximum for the battery is 2C, 1.4 would be OK. Is this incorrect? I have been discharging my packs/cells with a light bulb that's drawing 4 amps, I generally run the pack down until my battery alarm goes off (that's set to 2.8v as near as I can figure), which causes the lowest cell to settle on a resting voltage of about 3.4. If one or more cells are still too high, I drain them individually through the balance connector until the voltages are reasonably consistent. I was under the impression that this would be a good break in procedure? Some packs/people are venturing into charging at over 1C I've not been there myself. I tend to charge my 2250's at 1.8A, so around the 80% of 1C mark. Consensus of opinion seems to be that charging lower than 1C does less harm to the packs. Each cycle take a little bit out of their life span. The key to these are they have a finite number of cycles they can do, the easier you are on them the greater that number will be, and conversely the harder you are, the shorter their life span. If you are happy that you will replace your packs on a regular basis then don't worry about being soft on them. If you want to use them for hundreds of cycles then treat them with kid gloves  If time is against you then once you've mastered the art of looking after lipos read up on parallel charging packs. It can be done, I often do 2x2250 at 3.8A halving my charge time. You should be very conversant with the properties of Lipos before attempting this.
I take no responsibility for damage to property, injury, death etc.
Should you attempt this, you do so at YOUR OWN RISK |
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Post by flydiver on Sept 18, 2009 6:22:58 GMT 1
There are some new packs that apparently will charge at 5C.
The Cellpro series has been set up for ages to do 1/2/3C. I use them all with no apparent problems on a wide assortment of lipos. I would not recommend this with other chargers unless you know what you are doing and are very lipo safe while charging. Charging is the most likely place to get into trouble with lipos.
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Post by Dillzio on Sept 19, 2009 9:29:44 GMT 1
Thanks for the tips guys. It's nice to have a place like this where I can get good advice about this sort of stuff. Unfortunately there are no RC clubs on my side of the city that I can find, but I am aware of some regular flyers at a nearby reserve on saturday mornings. I should go by sometime and ask them if they are part of a club.
I will have to get a balance connecter converter off of ebay so that I can parllel charge. Being able to charge two batteries at once is going to be way quicker than using a higher charge rate on single packs that will ultimately reduce their lifespan.
Oh, and in lipo charge mode, this charger does drop off the input current when the cells are getting full. Once this current is reduced however, the charger seems to take AGES to balance the cells. Like most other charges, in fast charge mode the final charge voltage is 1/5 instead of 1/10, so the battery charge cycle will finish quicker, but the battery won't hold quite as much charge.
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Post by Dillzio on Sept 19, 2009 9:43:56 GMT 1
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Post by ginginho on Sept 20, 2009 12:33:10 GMT 1
First off, don't even think about parallel charging until you are very conversant with lipo technology. Your previous statements regarding voltages would suggest that you are not yet there. That lead may work. It doesn't look particularly good though. You do not want to charge packs only via the balance lead as the wire that constitute this connection are not built to take charging currents. Really you want a balance board and a Y (or several depending on how many packs to parallel) lead so that the power it delivered via the main lead, the balance leads only doing what they are supposed to do. |
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Post by Dillzio on Sept 20, 2009 13:11:01 GMT 1
The stock super cub LP charger only charges through the balance tabs, and so does this mid-range Turnigy charger: www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=7898&Product_Name=Turnigy_420_Balancer/Charger_2S~4SI don't think there is anything wrong with charging through the balance tabs, as long as the charging current doesn't exceed what the wires can handle. Judging by the gauge of the wire I'd say it could easily handle 3 amps. What statement regarding voltages suggests that I don't understand Lipo technology? I was referring to the three cells of a 3S battery, each of which has two tabs, and is wired together in series. The main 12v power wires connect to the positive tab of the first cell and the negative tab of the last cell, thus combining the voltages of all three in series. If you rip open the top of an old Lipo you can see for yourself. The main negative lead connects to the same tab as the black lead on the balance connector, and the main positive lead connects to the same tab as the first wire on the balance connector. |
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Post by ginginho on Sept 20, 2009 14:27:31 GMT 1
The stock super cub LP charger only charges through the balance tabs, and so does this mid-range Turnigy charger: www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=7898&Product_Name=Turnigy_420_Balancer/Charger_2S~4SI don't think there is anything wrong with charging through the balance tabs, as long as the charging current doesn't exceed what the wires can handle. Judging by the gauge of the wire I'd say it could easily handle 3 amps. What statement regarding voltages suggests that I don't understand Lipo technology? I was referring to the three cells of a 3S battery, each of which has two tabs, and is wired together in series. The main 12v power wires connect to the positive tab of the first cell and the negative tab of the last cell, thus combining the voltages of all three in series. If you rip open the top of an old Lipo you can see for yourself. The main negative lead connects to the same tab as the black lead on the balance connector, and the main positive lead connects to the same tab as the first wire on the balance connector. You've previously stated "3.1 amps (1.4C) for the fast charge cycle" for some of your packs. Do you think this is safe if charging only via the balance lead which you state "could handle 3 Amps" ?? Not one statement, but a few. "I thought it was 2.7 before they were damaged. " and "I have been discharging my packs/cells with a light bulb that's drawing 4 amps, I generally run the pack down until my battery alarm goes off (that's set to 2.8v as near as I can figure), which causes the lowest cell to settle on a resting voltage of about 3.4. " for instance. Ok, you've been straightened out on these points, but it still suggests that you are not totally conversant with the technology. All I'm attempting to do it to make you aware that parallel charging is not something to start doing if you are relatively new to the technology. You've had your new charger for less than a month and only have been flying (and hence I suspect using lipos) for just over a month. This suggests that you're not "an old hand" with these.  |
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Post by Dillzio on Sept 20, 2009 16:01:09 GMT 1
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Post by Dillzio on Oct 26, 2009 1:40:34 GMT 1
I've just been reading the manual for the Turnigy Accucel-6 charger, and as far as I can tell it is IDENTICAL to my polimax charger, other than the fact that the Turnigy has a cooling fan. The manuals are the same almost word for word (Turnigy manual appears to have been proof-read by someone fluent in English) and they even have the exact same diagrams.
I even read somewhere that the Turnigy can be calibrated by turning it on while holding start and minus-arrow, and the exact same thing happened on my charger. I think the electronics are actually identical, just a different case - Just like the Imax and Mystery chargers.
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Post by Dillzio on Feb 8, 2010 4:06:29 GMT 1
One warning note about this charger:
DO NOT USE LIPO DISCHARGE MODE
It does not balance the cells while in this mode, and sometimes it even lets the pack voltage below 9v.
I wanted to discharge my ebay batteries to measure how much current they took to do a full charge, and a full discharge. What ever their capacity was to start with, I'm pretty sure it had gone down after using the discharge mode on this charger, as some of the cells were as low as 2.6v.
If you do want to discharge lipos with this charger, first use the storage mode. That will get you down to 3.8v per cell and will perfectly balance the pack. You then change to NiMH discharge, and set it to 9.5v. Your balance connector on the battery will be free, so you can hook a battery alarm up to that to alert you if any cell goes below 3v. After that, I would advice checking if the battery is still balanced, and if so, you can discharge all the way down to 9v, but make sure you use a battery alarm! This charger will only discharge at 0.4amps for a 3s lipo, so it's quite a slow process. If I want to discharge a battery in a hurry, I hook it up to a 12v headlight bulb with the battery alarm connected. If you do discharge like this, ALWAYS USE A BATTERY ALARM, I learned that one the hard way!
Other than the Lipo Discharge mode on this charger, I still find it to be a very good little unit.
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Post by flydiver on Feb 8, 2010 4:34:51 GMT 1
Have you looked at a lipo discharge curve? Once they hit the end of capacity 'knee' they just fall off. Unless cells are d**n close to perfectly matched to start it's unlikely they'll hit the knee at the same time. They may be close to balanced one minute and not very close the next.
I suspect the good news it with a DC rate that low it did not ding the lipo very badly taking it down that low.
I agree with that this is likely just a clone of the AC-6 from the same factory with a few minor tweaks. They are popping up everywhere.
FWIW I've found the lousiest capability on mine is the NiCad charging. The stock peak termination is grossly off. It would be hard to get a decent charge with this unit.
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Post by john66 on May 28, 2010 9:57:00 GMT 1
I bought this same charger last weekend from ebay for £29.99 with free postage from a uk seller. It arrived wednesday so yesterday I decided to use it in storage mode as I didnt know when I would next be using my batteries. After I had done this I used the same battery checker that ginginho has from GC to find that the 2 of the 3 cells were different. I decided to recharge them on balance charge figuring this would sort it out. It hasnt 1 cell remains different on both my stock battery and a loong max 2250 i have. Any thoughts anyone, hows your one dill?
Stock battery
1. 4.13
2. 4.13
3. 4.10
Loong Max 2250
1. 4.19
2. 4.18
3. 4.15
these readings I have just taken now.
John
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Post by ginginho on May 28, 2010 11:42:55 GMT 1
I bought this same charger last weekend from ebay for £29.99 with free postage from a uk seller. It arrived wednesday so yesterday I decided to use it in storage mode as I didnt know when I would next be using my batteries. After I had done this I used the same battery checker that ginginho has from GC to find that the 2 of the 3 cells were different. I decided to recharge them on balance charge figuring this would sort it out. It hasnt 1 cell remains different on both my stock battery and a loong max 2250 i have. Any thoughts anyone, hows your one dill? Stock battery 1. 4.13 2. 4.13 3. 4.10 Loong Max 2250 1. 4.19 2. 4.18 3. 4.15 these readings I have just taken now. John John, Are you checking these with the little board? These aren't very accurate on a per cell basis, generally used just to check the overall pack charge and to make sure that the cells haven't been hammered (after a flight). I don't know your charger, but if it's similar to most, you should be able to see the state of each cell whilst it's charging the pack. Although these are not likely to be extremely accurate, it will be better than the "field" board. Try starting a pack on a storage cycle then press the second from the right button, this is how I display individual cell charge on my (looks similar) charger. |
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Post by john66 on May 28, 2010 11:48:02 GMT 1
Cheers ginginho, yes I'm using the little field batt tester, will put them on storage again later and try what you say.
Thanks, John
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