# Balancing Chargers



## Chompers (Jan 8, 2008)

this thread is in response to a side conversation in the 'need help choosing a battery' thread.


Shipping from hong kong is a pain, but it is fast. (my box was at my front door in 5 days (including Sunday).

the LHS wanted over 4.5 times the cost of the accucel-6 for a lower quality charger, it didn't have a power supply either.

.Personally i use an old MRC control master 20 power supply- and thus i do not include this in the cost.
Also old computer power supplies work nicely- and are easy enough to come by. 
you can also clip the leads to 12v auto battery.The TB6 might be a better fit for some depending on shipping/ and feature needs. if you do not need a second power supply you would be hard pressed to find a better value charger. and that is the very reason that i bought the accucel 6 rather than a more expensive model.


Irregardless of price, a charger like this would only be beneficial if the battery packs had balancing taps.

for my large scale instillation i am wanting to go with li-ion packs due to there built in short protection, but i have not seen reasonably priced li-ion packs with balancing taps. Iit would offer the safety of a li-ion pack with the longevity of a lipo pack. but they don't seem to exist.


But since such packs are not available i am now leaning twords a modular design with interchangeable li-po packs. although not ideal- it would allow for the charging of the pack out side of the engine on a propper charger. Since a trade off must be made between longer running sealed packs and properly charged battery cells; i feel that it is a wiser decision to go with properly treated batteries (balanced). does this make sense? thought and comments would be appreciated on this.


I really raise this question of using a balancing charger because over time the voltage between cells tends to drift. this can cause over charge/discharge of the li-xx cell. This is BAD- this is where trouble in using these cells can occur. but if charged properly they work flawlessly.


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## sailbode (Jan 2, 2008)

Hey Phil,
I'm using an "Imax B5 balancing charger. I think I paid around $40 from the same place. Unlike you, my planes are in the 5 pound range using (2) 5000 mah 3 cel packs in series (24volts) drawing 60 amps. We're talking straight up acceleration! Wow, what a ride! OK enough plane talk...sorry guys, yes I guess there is a good reason we are called crazy plane guys!. 

I just got a Li-ion pack from Rick at "Cordless" (for a train) and asked about the lack of cell taps. Rick gave me the impression for this application they are not really needed. Wouldn't hurt but probably not worth the trouble or added expense....unless I misunderstood him. I'm not too concerned as these are the same batteries that are used in cordless drills and I believe most of them don't use balancing chargers either.
Don


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## Michael Glavin (Jan 2, 2009)

Most Li-Ion battery packs NOT individual cells have a safety circuit built into them, this safety circuit is comprised of a controller or IC that monitors each cell (or parallel cells) voltage to prevents the cells from over-charge. Voltage realized at the cut-off switches or FET's is also monitored by the IC to prevent excessive current consumption during charge and or discharge. Additionally there is typically a poly fuse, these are also known as fusible links too; shorts, excessive heat and or current opens the one-time fuse. Once opened the poly fuse must be replaced. Some Li-Ion battery packs have in addition to the aforementioned safeties a PTC or thermistor that monitors pack temperature and reports back to a "smart charger", these devices control charge current preventing overheating or thermal runaway! PTC's are also offered as accesories coupled to smart chargers and placed under the battery to again report the temperature while the battery is under charge.


All that said NO; Li-Ion battery packs with cell balancing structure that requires ancillary equipment (chargers) do not exist, as the concept is in play already and included by responsible pack assemblers... But not all Li-Ion battery packs are created equal as you can purchase these cells in bulk and assemble battery packs similar to NiCD/NiMH packs without safety circuits. In this case a smart charger is a must and the need for cell balancing becomes plausible. Cell balancing to some degree is achieved by slow or trickle charging cells of most chemistries.


I've played around with lot's of battery chemistries in the infancy of the RC Aircraft markets exposure to high energy density batteries (power to weight), to that end we expended 100's of hours testing-charging-using and abusing batteries for aircraft. It was a blast at the time my son and I traveled all around the USA competing in contests and working with sponsors at shows and such. Fond memories for sure! Last I checked we still have hundred of Lithium battery packs most of them have seen better days, they simply are not as robust as NiCD or even NiMH. They inherently loose capacity from the date of manufacture forward, cycling (using-charging-discharging) only increases the inevitable capacity reduction to sooner than later. Lithium Magnesium is the stuff currently....


Michael


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## Greg Elmassian (Jan 3, 2008)

With the balancing chargers so inexpensive, adding the taps would be cheap... for our use, you would want to have a connector for the taps if the battery was permanently in place. Still a cool idea, the batteries will last longer, and add in that remote status gadget! 

I might be doing a few battery conversions soon, and that would be the cat's meow to be able to remotely see the status of your batteries. 

Regards, Greg


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## Dave Ottney (Jan 2, 2008)

Go to RCGroups.com and check out the battery forum. The search feature is very good so you can do a search for balancing chargers and for taps to get all sorts of info. I use FMA CellPro4s for balancing all my lipo packs. I even put taps on a LiIon pack I built. 
Dave


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## Del Tapparo (Jan 4, 2008)

Posted By Greg Elmassian on 19 Jan 2010 04:54 PM 

I might be doing a few battery conversions soon ...





What?







Do I need to clean my glasses? Maybe it's a virus!









Actually, that's great Greg. Nothing like hands-on experience. Glad to hear it.


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## Greg Elmassian (Jan 3, 2008)

Would not be my first use of batteries, just the first one done for someone else... there's about 200 rechargeables here at home... and a few chargers, and several precision power supplies for testing, and a scope, freq counter, RF service monitor, and a bunch of radios, ham that is.. 

I wonder though, while the multi-tap stuff is essential for high charge rate/high discharge situations, how much more life the multi-tap could extract from a lithium pack in our area of use. 

Regards, Greg


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## Michael Glavin (Jan 2, 2009)

Greg, 

In my experience it matters not at our discharge and charge levels, function really is a factor. And as I note in my previous post most Li-Ion battery packs are already balancing the cells with onboard safety circuits. 

I draw my “matters not “conclusion from actual experience with numerous Li-Ion packs without benefit of safety circuits. The very nature of the Lithium charge regimen helps in this regard, near the end of charge we’re essentially trickle charging and or minimizing/ limiting current to a pre-defined variable set point based on cell count. 

Cells died on the batteries with the “safety circuit” as often as those without. 

A loaded expanded scale voltmeter (applies a 1A or higher load while displaying voltage) is the best or simplest most effective method to identify cell failures, especially true of cells/packs wired in parallel. I used to see voltage levels well above accepted no fly minimums, only to realize the battery was unable to support said voltage under 1A load. In this cause voltage is no indicator of battery and or cell capacity. 

Most of my experience was garnered from small 6oz to 16lb ready to fly electrically propelled 3D aerobats all the way to 40% Giant Scale 3D gas powered scale aerobatic planes and there onboard flight systems which supported as many as fourteen digital servos which consumed power in large gulps, often spiking upwards of 25 Amps. Typical flight packs are Li-Ion in 2S2P format while electrically powered models use Li-Poly of various series/parallel configurations based on voltage and current requirements. To be honest the Li-Ion cells utilized as flight packs on the GS Aerobats were not up to the task unless ganged in 2S3P formats with the 4000-4400mAh cells 18650 cells (same cells typical of our applications with trains). 8 Amps was typically garnered from a 4000mAh 2S2P battery pack, I recorded many battery packs providing 8A at rated voltage for 20 minutes or so... 

High discharge/fast charge Li-Poly battery pack applications definitely benefit from cell balancing IMO. 

Cell balancing is not an issue unless multiple cells are configured into battery packs. 

Michael


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## Greg Elmassian (Jan 3, 2008)

Michael, I understood everything you said. 

If you were responding to my last sentence, maybe I was unclear... In our situation, where a very rapid charge is not necessary, and the discharge rates are usually 1/2 C, not C times a big number, I wonder if balanced charging would give more total battery lifetime. 

Regards, Greg


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## Chompers (Jan 8, 2008)

hey greg

if you want battery voltage feedback take a look at the new spectrum ground based Radios. They have a new 'telemetry' feature that allows the RX to send real time info back to the tx. the info is then displayed on the built in screen. 

Of course being a 'new' product expect to spend about the same as a 7 Channel DX7se- with half the channels-mixes-and range.... BUT real time battery and sensor feed back would be cool.

http://www.spektrumrc.com/Products/Default.aspx?ProdID=SPM2120


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## Greg Elmassian (Jan 3, 2008)

Yeah, I liked the other 29 dollar transmitter/receiver gadget that could work with any system... 

lots of cool ideas. 

Regards, Greg


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## Chompers (Jan 8, 2008)

I do believe that ballancing would give longer total battery life time, in the sense that trains would run longer. would would happen is that packs that are propperly ballanced will take more mah per charge because the target voltage will not be prematurely reached, like wise LVC will not cut in prematurly due to an under charged cell. 

plus ballanced cells don't run the risk of going boom as much. even a slightly over charged Lipo cell runs the risk of quite serious failure. 

Michael brings up the point of the built in PCB- which i have interpreted as voltage protectors. battery space says that there pcb will limit over/ under voltage cut off.(my question is is that for each cell of just the total pack voltage) reverse polarity (they make keyed battery connectors for a reason) and current limit (actually use full safety feature). 
I guess it brings the question down to trust- do i trust there PCB or a quality charger- the accucel lets me see the individual voltage of each cell during any point in the charge phase-with the pcb i am blind as to the actual voltages. 

I'm just not sold on the idea of a lowly pcb delicately allotting voltage and current to each cell in perfect moderation lol I would just feel better knowing exactly what is going on. plus the accucel has other safety features like user adjustable MAXIMUM mah valuse that may be added into teh battery- and maximum time that the charger will run irregardless if the cell registers as done or not. its jsut extra layers of protection. 

Michael also brings up teh pint of the temp. probes. it is nice to know that if i wish to use them the accucel has a temp probe port  but i have found that the balance setting at 1C doesn't even warm my lipo batteries- they are room temp when they finish charging. defiantly a good thing 

Dave, i must confess having been a member @ RC groups for a few years the battery forum is one i have never visited. i mainly hang out in the park flyer and mirco/ indoor forum. can't believe i haven't searched there yet 

am i probably over analyzing this??? yes I'm an EE major its my nature to that 

Thanks you guys 
your input is appreciated


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## Chompers (Jan 8, 2008)

greg what battery monitor are you thinking of? link? 
for 30 bucks i think i might just add one of those to my next large HK purchase


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## Michael Glavin (Jan 2, 2009)

Greg, 

I tried to answer your question, Ill try again. Sometimes I run onto a siding and get lost. 

“In our situation, where a very rapid charge is not necessary, and the discharge rates are usually 1/2 C. I wonder if balanced charging would give more total battery lifetime.”

It matters not in my experience... Cells died on the batteries with the “safety circuit” as often as those without. Since the safety circuit provides cell balancing and my data graphed both batteries equipped with safety circuits and those without. The battery packs without; were unbalanced and relied on the charge algorithm only. 

I didn’t make it clear but most smaller aircraft flight systems are much less demanding and draw a good parallel for comparison, i.e., ½ C discharge rates with sporadic spikes.

My example of the larger aircraft was just FYI.

Michael


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## Del Tapparo (Jan 4, 2008)

Posted By Greg Elmassian on 19 Jan 2010 10:46 PM 
Yeah, I liked the other 29 dollar transmitter/receiver gadget that could work with any system... 

lots of cool ideas. 

Regards, Greg


Greg - Can you provide a direct link to this gadget please? I couldn't find it.

Thanks,
Del


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## Greg Elmassian (Jan 3, 2008)

Sure Del, it's under chargers...

*http://www.hobbycity.com/hobbycity/...ry__869Mhz* 


This should work.

Regards, Greg


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