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Field Charging 3s lipos

Old 05-14-2016, 11:59 PM
  #1  
sosterhaus
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Default Field Charging 3s lipos

Many of the threads and posts seem to be targeted to larger lipo's and all day flying. My needs (and I believe those of many other Electric RCer's) are more modest with planes under 4#, using 3s (and maybe 4s on occasion) lipo's with maybe a morning or afternoon of flying. Generally, hope in the near future to get in 8-12 flights of 6-10 minutes.

Rather than buy a dozen lipo's, looking for efficient and very simple way to charge at the field (no electricity) without huge cost. Love to use solar, but might be too costly vs. a dozen lipo's. With the small amount of needed charging (have 5 lipo's), would a regular car battery suffice or go to heavier marine battery? Have a charger at home for recharging it after use. Figure about 40 minutes to charge so over 3-4 hours could get 3-4 charges, so maybe total of 9 flights. Could hook up 2 chargers and double the recharging.

Any thoughts or responses on what others do. Thanks -- any input is appreciated.

Steve O.
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Old 05-15-2016, 12:30 AM
  #2  
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I used to use a larger deep cycle with a cellpro 10s. It would give me maybe 4-5 charges of a 4s 5000mAh iirc. Im not saying it was a new, or even good battery. It will work. If you dig a little here in these forums, this has been discussed at length in a couple/few threads.

"Most" modern lipos can handle a 2c charge rate (1c still is best for longevity). Check with the manufacturer. I utilize faster charging currents at the field.

"Any thoughts or responses on what others do?"
Personally, I bought a small generator and built a charger box. Might be an option for you to consider as the addiction takes further hold of your life.
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Old 05-15-2016, 12:54 AM
  #3  
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A 12v car battery will work. Balance charger ?
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Old 05-15-2016, 01:36 AM
  #4  
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Do you drive. The reason I ask, I run a HITEC X4 charger off of my truck battery at the field. I can have 4 charging at once and that helps keep things flying. As mentioned above, if you search this forum there are some pretty nice setups some guys have put together
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Old 05-15-2016, 02:30 AM
  #5  
sosterhaus
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Thank you all for the replies. Sounds like a car battery will handle my needs for now. When I have used my vehicle battery but not best option. Do use a balance charger and most lipo's are 1800 and 2200 mAh though looking adding a bit bigger plane needing a 4s 3500 later this summer. Still fairly new at RC, but have too many hobbies. Even though retired, we travel, are snowbirds and time just slips by.

Really enjoy RC, but trying to keep it in perspective or so I try. Thanks again.

Steve O.
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Old 05-15-2016, 04:41 AM
  #6  
firemanbill
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I carry a deep cycle marine battery in the back of my truck for charging at the field. I can charge my 6s batts of it without issue.

You could charge 3s 2100's off of it for several days without recharging it.
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Old 05-15-2016, 07:57 AM
  #7  
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I did carry separate battery before for charging but now don't bother. I use the vans starter battery. I can charge a bunch of 3S without engine running - but if I am charging a number of packs - then I run the engine just in case.

If you do sort a separate battery - you can always get a lead to charge it via the ciggy socket while driving to / from flying site - so in effect you never have to remove and charge at home.

Nigel

Last edited by solentlife; 05-16-2016 at 07:27 AM.
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Old 05-15-2016, 11:13 PM
  #8  
firemanbill
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I had to give a buddy a jump start one day. He spent much longer at the field and charged a lot more than he meant to I suppose.
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Old 05-15-2016, 11:28 PM
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sosterhaus
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Yeah, happened to me last year, will probably get a battery to haul to the field. Should suffice for my needs. Thanks.
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Old 05-16-2016, 07:35 AM
  #10  
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OK its not so simple a matter of just get a battery. Lead Acid battery's do not like to be discharged below 50% even on a proper deep cycle. So your 80A/hr battery is really only 40 at best. Then you have to consider that as charge state declines, the charge rate you can get for your packs falls away as well.

This all means that you need increase battery size to compensate. I got fed up with lugging that battery around and reverted to using the onboard starter battery. As I say - if I charge more than a couple of packs - I start the engine.

I would never trust the shut-off facility on the charger - supposed to stop you discharging battery too low.

Nigel
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Old 05-16-2016, 12:27 PM
  #11  
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Originally Posted by solentlife View Post
OK its not so simple a matter of just get a battery. Lead Acid battery's do not like to be discharged below 50% even on a proper deep cycle. So your 80A/hr battery is really only 40 at best. Then you have to consider that as charge state declines, the charge rate you can get for your packs falls away as well.
All good reasons to perhaps simply buy a few extra LiPos and don't worry about field charging.

It's certainly a cheaper option long term than using you car engine as a generator, gas price being what it is.
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Old 05-16-2016, 12:48 PM
  #12  
solentlife
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I have to agree that more LiPo's does make sense until like me you end up with boxes of them. When do you stop buying them ?

I run from 2S 1000 up to 5S 3000 packs and in the 3S and 4S I have more than 5 of each size.

Its not the carriage of so many LiPo's ... its the putting back to storage those not used that day.

I usually take a variety of models with me in the van ... cars even Volvo Estates don't carry as many as my Renault Master Van !!

Lets take an average session for me ...

Stampe : 3S 1300 Blue Turnigy square packs
Cessna 182 : 3S 1250 Rhinos (this is HK's and the square 1300 doesn't fit !)
Hummer : 3S 1250 Rhinos
Mini Katana : 3S 2000 Compacts
Lancaster : 3S 2250 Rhino
Yak 55 : 3S 1750 Rhino
Polaris : 3S 2000 compacts
Skipper : 3S 1750 Rhino

I have left out the fuel models usually in there as well.

I may alternate one or two above with my F15 4S 1600, T45 3S 2200 / 4S 2700, Edge 540 5S 3000, Ultimate Biplane 3S 2000, Edge 540 4S 1600 etc. ....

All depends on weather that prevails that day as to what gets flown ...

Nigel
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Old 05-16-2016, 02:41 PM
  #13  
sosterhaus
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Solentlife and Jetplaneflyer -- great points. May very well be for my flying to get 3 or 4 more batteries (and another charger) and enjoy 8 or 9 flights and not worry about field charging, though probably could get 1 charge off Van battery if need be. Generally take 2-3 planes. May even be a bit cheaper than buying a deep cycle, box, etc., plus making sure it is charged.

As my lipo's are smaller (3s 1800, 2400 and maybe 3200 in near future) this just may be the best solution. Plus, keeping the battery fleet around 8-10, with 2 chargers at home should only take 2-3 hours to recharge for next outing.

You all have been most helpful.

Steve
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Old 05-16-2016, 02:52 PM
  #14  
JetPlaneFlyer
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What I sometimes do is use some of my older large LiPos as the power source to charge up smaller LiPos, or hook a couple up in parallel to charge a larger battery.

This is a good use for older batteries that are losing some of their 'punch'. It also gets around some of the problems that Nigel describes when you have lots of different sizes.. You just charge them all then 'transfer the charge' to the ones you need more of on the day in question.
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Old 05-16-2016, 03:27 PM
  #15  
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I have a bank of 4 chargers at home ... 2 x 50W, 1 x 60W and 1 x 80W ... with 2 x 3in1 Dischargers.

One of the 50W jobs also travels in the van with me.

I have a second 60W charger but it has a USB bridge fault and needs to be connected to both power and PC to operate. So it stays as a spare.

People tell me I ought to have one high power charger to replace the above ... but I believe in 'redundancy' I know that I will always have a charger even with failures.

The 60 and 80W chargers have iR testing, Battery metering etc.

That's my setup and works well.

Nigel
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Old 05-16-2016, 04:42 PM
  #16  
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Speaking of batteries... My Jeep needs a new one now. ugh... I hate it when I have to spend my toy money on real world stuff....
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Old 05-16-2016, 06:17 PM
  #17  
sosterhaus
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Agree Nigel, redundancy makes lots of sense. Just made an simple t-plug adapter that will connect my 3s 5000 mAh lipo's to my charger. Have 2 that I do not use in flying so those will provide at least 2 charges at field--maybe even 4 for the 1800's though will see.

Steve
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Old 05-16-2016, 07:51 PM
  #18  
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Originally Posted by solentlife View Post
That's my setup and works well.

Nigel
It all depends on your needs. Your setup is fine for smaller batteries but a 50W charger would take 2 1/2 hours to charge just one 6s 5000mAh battery. I have seven of those, plus eight 6s 3000mAh.

That's 31 hours of 50W charging. Even with your four chargers it would be over 6 hours of constant charging, then i have some smaller batteries to throw in the mix

With my one iCharger 4010 duo I can charge the lot in 45 minutes. In terms of watts of charging power for $ spend the big powerful chargers are better value.

For field charging I picked up a 300W Turnigy 'Reaktor'. Great little charger as not a lot of expense.
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Old 05-16-2016, 08:04 PM
  #19  
solentlife
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Originally Posted by JetPlaneFlyer View Post
It all depends on your needs. Your setup is fine for smaller batteries but a 50W charger would take 2 1/2 hours to charge just one 6s 5000mAh battery. I have seven of those, plus eight 6s 3000mAh.

That's 31 hours of 50W charging. Even with your four chargers it would be over 6 hours of constant charging, then i have some smaller batteries to throw in the mix

With my one iCharger 4010 duo I can charge the lot in 45 minutes. In terms of watts of charging power for $ spend the big powerful chargers are better value.

For field charging I picked up a 300W Turnigy 'Reaktor'. Great little charger as not a lot of expense.
No argument there at all .... big packs demand big power ... simple.

I have 2x 5S 3000 and they fly my Edge 540T ... I charge those on my 80W Accucel while all my other smaller stuff is being charged. So really I don't notice it because I charge up so many smaller ones anyway. Those at 2C are well catered for with my chargers.

If I was to go for 6S and so on ... then yes - I would be looking at the 300W Reaktor or similar.

Nigel
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Old 05-16-2016, 08:21 PM
  #20  
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Hi JPF ....

I think its time for you to carefully in detail explain the process of charge transfer you use from one LiPo to another .....

I do say carefully as we need to be sure that no newcomer to E-Power has an accident !!

Nigel
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Old 05-16-2016, 08:43 PM
  #21  
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Most "12v" chargers can accept 3S LiPo as source to charge other LiPo (or other types if the charger is designed for it)

The "LVC" (low input volt error stops charge) of most of these is appx 10.5 v under load which comes out 3.5v/cell which as actually considered an acceptable LiPo LVC
(Better check where your charger cuts out on low input voltage....)

No... don't just connect + to + & - to - of 2 packs and hope for the best. Current in that case will be limited by internal resistance of the packs (which is very low) and the E=IR Ohm's Law formula.
Voltage difference = current * Resistance. The potential is there to melt your connectors off the packs.
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Old 05-16-2016, 11:32 PM
  #22  
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Originally Posted by solentlife View Post
Hi JPF ....

I think its time for you to carefully in detail explain the process of charge transfer you use from one LiPo to another .....
It's pretty straightforward Nigel. I have a few 6s 3000mAh packs that while still good enough to fly models reasonably well are getting a bit tired, so I prefer to fly with newer ones, so i can use these batteries as 'charge donors' to power my charger off of. If you have a bunch of old smaller batteries you could connect them up in parallel to have the same effect.

My 300W 'Reaktor' charger will take input of up to 28V so a 25.2V (max) 6s LiPo is perfect for supplying power to the charger. Some chargers are limited to lower input voltage, so could not accept a 6s battery. Just read the manual to find out what your charger will take.

I can charge a few small LiPos from one 6s 3000mAh or I can parallel up a couple of them giving 6000mAh capacity and use that for charging one of my big 6s 5000mAh batteries for my 700 size helis.

As pointed out by fhhuber, you can only do this 'transfer of charge' by using the charger to control the charge process. You cant simply connect up a charged LiPo to a discharged one, that could end badly! Also be careful not to over discharge the 'donor' battery. You can either set a low input voltage voltage cutoff in the charger software, or simply plug in a cell checker/alarm into the balance port of the donor battery (which is what i do).

It's just a useful way to get more use from the batteries i have rather than buying yet more new ones.
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Old 05-17-2016, 08:50 AM
  #23  
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Its funny that I have been considering for quite a while about using my old packs for the charger.

I have loads where one cell has failed or they just don't deliver punch to fly. Connecting up to provide charger source is a solution. The better ones get used as Rx supply in wet fuel models because the power draw is very low and they can work fine.

I will be revisiting this matter.

Nigel
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Old 05-17-2016, 02:55 PM
  #24  
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Looks like using 3s 5000 mAh lipo's might be a good solution -- simple and re-purposing. For me, field charging 1800's and 2200's with 50W and 80W chargers shouldn't be an issue. At a 2C (2.2 amps) charge rate X 12.6V Max. Voltage = 27.7 Watts. Takes about 40 minutes and the 5000 X 80% (4000 mAh max drawdown) should give 2 charges, though might see drop in amp charge rate on 2nd. Even a 4s 3400 on 80W charger should not pose a problem -- 3.4 X 16.8 = 57 Watts.

So, having 2 3s 5000's, if my math is correct, should be able to add 3-4 extra flights from existing batteries in 3 hours at the field.
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Old 05-17-2016, 03:16 PM
  #25  
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Sound like a good plan. You could connect up your two 3s 5000mAh in parallel to make 10,000mAh which you should be able to get four charges (maybe even five) of your 3s 1800-2200mAh batteries or two charges on your 4s 3400mAh. It's certainly a lot more convenient solution than lugging around a huge and heavy deep cycle marine battery.

Get one of those little cell checker/alarms that plug into the balance wire and set the alarm to 3.4V to protect from over discharge of the donor batteries.
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