Charging Un-matched Li Polies in Parallel?

Hi, I have three TP Li Poly batteries 3S 2100 mAh that have bee
discharged to varying degrees of voltage. It sometime takes about 3
minutes to recharge individually, depending.
I wonder it they could be connected in parallel and recharged? Or woul the batteries be un-balanced? If this could be done, would the chargin time be shortened?
Wa
-- Wa ----------------------------------------------------------------------- Wan's Profile: http://www.rcgroups.com/forums/member.php?us01 View this thread: http://www.rcgroups.com/forums/showthread.php?tI646
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Wan wrote:

Not a particularly good idea to connect batteries at varying states of charge in parallel, no.
Get some more chargers ;-)
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wrote:

You should not charge Lipoly batteries in 30 minutes. They should not be charged at more than a 1c rate , which would be one hour , or slightly more. In your case the charge rate should be no more than 2100 ma.
You also need to be ...very... concerned about the... balance.. of the individual cells. If they are unbalanced they need to be charged at a very slow rate. In most cases a 12 hour charge would be OK. One of the idications of an unbalanced pack is if the volage per cell is less than 3.3 volts. In your case the pack should be no lower than 9.9 volts. They can still be unbalanced if they are not this low in voltage , but this is the most common symptom.

Don't charge more than one pack at a time . Multiple packs can be charged in parallel but only if all cells and packs are balanced.
I would recommend that you go to here before you do anything .
http://www.thunderpower-batteries.com/html/charging.html This is a link to a pamphlet on charging Lipoly batteries.

Ken Day
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Charging at 1C may well give a 30 minute charge time if the the pack is less 50% discharged, which is entirely possible. I've occasionally gone over 80% dischgarge, but 50% is more typical for me; may be the same for Wan.
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Wan, this is one of those things that could likely start a fire. Don't even think about it. Just hooking up LiPos in parallel without balancing the packs can ruin the batteries or start a fire. The packs will start to balance themselves when hooked in parallel. If there is a significant voltage difference, the low internal resistance will cause a huge current flow from the higher voltage packs.
If you have a charger that can discharge LiPos, like the Astro 109D, discharge the packs to a common level, then you can hook them in parallel and charge them that way.
PCPhill
----- Original Message -----
Newsgroups: rec.models.rc.air Sent: Saturday, March 25, 2006 7:46 AM Subject: Charging Un-matched Li Polies in Parallel?

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I meant to mention this before, there is a decent 4 port LiPo charger that can charge your packs simultaneously, so you can avoid the balance issue on your packs.
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXKAU0&P=0
PCPhill

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I concur. If you have only one charger, it should be a Triton or something comparable that gives you lots of flexibility and information about the pack and the charging process. But if you get a 2nd . . . I have that Polycharge-4 (that's what the link points to) and it's been working just fine. Being able to charge 4 packs in parallel (5, counting my Triton) has been immensely useful.
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Thanks, everyone. I have read the pamphlet from TP and follow the procedure closely. My charging has been done in a thick oven baking dish. I believe I understood the hazards.
I did keep data from my 3S TP Li Poly rechargings after flying sessions. I found on the average it takes about 30 minutes or so for each battery. Sometimes it may take abut 5 - 10 minutes if I wanted to top off a Li Poly before leaving for the field. I don't think Li Polies need topping off, but I just want maximum flight time.
So according to your advice, I should not try to put my 3S TP Li Polies in parallel with others for recharging? And if I find a cell that measures less than 3V, I should take up to 12 hours to bring it back to voltage?
I have an Astro 109 and it could charge one battery at a time. Though it is a good charger, I regret I had not purchased the PolyCharge4 by Great Planes. Maybe it's a recently available item?
Wan
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On 25 Mar 2006 18:41:28 -0800, snipped-for-privacy@toast.net wrote:

With all due respect , you really need a Covered container of some sort. You can't be TOO careful with these batteries. I have a small fire-proof safe that I charge and store my batteries in. I have about 25 packs of diffferent capacity and configurations , so this works very well for me. I don't carry them all at one time , depends on what I'm flying that day. I have another safe in my garage that I also use to charge and store batteries in.

Wan , I was speaking of a discharged pack when I said one hour , thats why I went on to say charge at a 1C rate and gave an example for your battery so you would know that.

Won't hurt to do this but no point in it. Lipolys hold their charge longer than any of the most used batteries. NIMH self discharges faster than any , Nicad second , then Lipoly.

I assume you're responding to me since I addressed charging 'unbalanced' packs in parallel. I said that "Multiple packs can be charged in parallel but only if all cells and packs are balanced ". The packs must also be the same capacity and cell count.

It can take that long to do it safely , it really depends on the state of imbalance.

In my opinion , you have a better charger than the Polyquest. Read the specs on the Polyquest. It's not nearly as powerful as the Astro and I don't think it would charge your three packs in an hour if they are discharged fully. According to the specs it's only good for 3 amps , only half the power you would need for your packs. It's hard to beat the Astro Flight 109. I've had a number of chargers including the Triton and the Astro Flight is my pick , of course , it is a dedicated Lipoly charger. I have no other batteries now except flight packs and transmitters.
I have an Astro Flight 109 and I routinely charge five 3s1p 1500ma packs in parallel. But I do keep a close eye on my packs. It's capable of 9 amps and will charge multiple packs in parallel.
Everyone here is just trying to help. I haven't seen any bad advice. Sometimes it's easy to misunderstand one another and there are so many variables to consider that we can't cover it in a post here. Thats why I referred you to the the charging instructions on the Thunder Power site.
We can't stress enough the dangers associated with LiPoly batteries if mishandled. I'm certainly no authority on electric flight but I have been in it for quite a while and been using Lipoly's for about 3 years or more. I've seen a few of them burn . In fact I had two 1500 3 cell packs go up in smoke. That was before I became well aware of the problems associated with charging packs with unbalanced cells. Fortunately one was in my safe and the other was outside on concrete. Here is a web site that really goes in depth on the study of batteries. Also aptly named.
Hope this helps http://www.batteryuniversity.com/
Ken Day
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Ken, I had not checked the manual for the Polyharge4 until you mentioned it. It does have a 3.0 A limit. Probably works for my TP 3S 2100 mA battery since 1C would be 2.1 A. I would have a problem with this charger as I have packs (3S3P Kokam) that require 4.5 A. In times past I had a Triton capable of max rate of 2.5 A. I found it took several attempts (charge and charge again) before the packs were up to voltage. This may take hours. So I would have a problem with the PolyCharge4 as well for the Kokam batteries.

I have not heard any disparaging remark here. Everyone has been most helpful.

Thanks
My first LiPoly was bought 3 years ago. Only ruined one pack by accidentally leaving it plugged even when the switch was off. Since then, I was advised to uplug and remove a pack from the airplane. Prior to that, I was deeply involved in glo power.

I could be wrong, but I thought one should not charge LiPolys on any metal surface?

Thanks again.

Wan
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Ken Day was right. I went back to my log of charging my Li Polies and it did take about an hour to recharge a nearly exhausted 2100 mAh pack. When I said it took about 30 minutes, it was about a partially discharged pack to keep it strong for the next flying session.
Wan
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On 26 Mar 2006 01:59:51 -0800, snipped-for-privacy@toast.net wrote:

The safes I have are covered in some sort of non conductive material which looks like some sort of hard plastic. They are built very much like a briefcase and have a hinged cover like one.
Ken Day
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4ax.com:

As I read the spec, it's 3A per output, not 3A total. I haven't found anything in the manual that suggests that there's a total charge current limit (aside from 4x3A). It uses a 20A fuse, and says that whatever's powering it should be able to provide 14A "in order to achieve the maximum potential from the charger."
So I'm thinkin' the limit really is 3A per output, not 3A total.
Each output appears to be limited to 30W, though, so if you're charging a 3 cell pack, you'll get more like 2.5A. Even allowing for the detection time and the (presumably) slower charging near the end-of-charge, you should be able to charge your deeply-discharged 3S2100s in about an hour if you're charging one pack per output.
As I said in the other post - if I had only one charger, it would be something more like the Astro 109 or the Triton or that Hyperion charger that a friend of mine showed me, because sometimes I really want to know how much charge the pack needed, and what the voltage is, etc. But for the rest of the time . . .
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wrote:

I stand corrected. I should have read the specs a little closer before I opened my big mouth :-) I just took a quick look at the specs on the Tower web site and it appeared to be 3 amp total. Thanks for pointing this out. I do like the fact that you can charge batteries as if you have 4 separate chargers , then you only have to be concerned with cells being balanced instead of packs and cells.
Ken Day .
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wrote:

Even though this charger is basically 4 chargers in one and can charge 4 packs at the same time , you still can't avoid the balance issue. You need to make sure the individual cells are balanced.
Ken Day

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Granted, but he was talking about charging seperate packs in parallel, not the cells within a single pack.
PCPhill

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