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-   -   Operating my LiPo Charger from batteries (https://www.wattflyer.com/forums/showthread.php?t=80072)

SoCal Perky 05-31-2019 04:47 AM

Operating my LiPo Charger from batteries
I am planning on trying a few new flying locations in a desert area. Being such, there is no power there to power my charger, and I do not want to switch over to gas until I fly awhile and see if I like the locations or not. Being the locations are some distance in the desert, I really don't want to use any vehicle to charge it that I depend on getting back to civilization with. I currently use a SkyRC iMAX B6 and charge 2/3 cell LiPo's from 450-2200 MaH. The charger book says you can power it with 12-18vdc I believe it was. Has anyone tried using like a wet cell of some type like a garden tractor battery to power one to charge their batteries? I tried it one time using a electric gate battery, but it turned off after like 15 minutes and said the voltage was too low to operate. The gate battery was not in great or new condition, but I wonder if the charger really needs 14 vdc like when a car that uses a 123 volt system is running to charge.

Anyone run their chargers strictly off a battery(s)? Any advice??

I'm planning on charging mostly 1300-2200 batteries and I believe a 2200 MaH battery stores about 2.2 amps of power in it. If I wanted to charge a 3 cell 2200MaH battery 9 times, would I need something like at least a 20 amp battery plus what the actual charger would use for the charging process? I dunno, looking for some advice... Thank You in advance for any help or recommendations.

solentlife 05-31-2019 11:21 AM

OK ... yes you can charge using a battery as power source. But your assumption on ampage is not enough.

Remember that as the battery powers the charger - it is also reducing its own level of charge. Any Lead Acid battery - even a Deep Cycle does not appreciate being driven lower than 50% charged level.

Given that a 3S LiPo is similar voltage level to a reasonably charged Lead Acid battery - we can then base on the ampage needed ... but taking into regard the 50% mark.

You wish to charge up 9x 3S 2200 packs. .... that's 9 x 2.2 as you rightly say. ~20A/hr.

Allowing a 50% mark ... now the power supply battery needs be 2 x 20A/hr = 40A/hr

Now we have to adjust because at 50% charge level - the Lead Acid battery will be lower voltage and struggling to provide the WATTS needed for the charger. I suggest add another 25 - 30% capacity ... now we are looking at a Lead Acid battery of about 50 - 60A/hr.

Lets move to practical and leave the techno aside.... I have always maintained that if you want to use Lead Acid batterys - then get to a Vehicle Scrap Yard where they sell of 2nd hand car / truck batterys. They will usually load test the battery in front of you ... cost is far less to pay .... and if it doesn't do the job - you haven't lost much.

My preference is for batterys supplied to power vans / trucks with hydraulic tail-lifts. They are a compromise battery that can suffer 50% discharge better than usual car battery.

Beware of usual so-called Deep Cycle batterys - because most are actually compromise format such as needed in RV's, Boats to power domestic as well as start engines. True Deep Cycle batterys should not be used for engine starting.

I have boats and I stopped buying Leisure batterys many years ago and now buy Scrap Yard batterys ... present batterys are 2 years old in my yacht ..

Final comment : You can while driving to flight location - charge your Lead Acid battery using your B6 ... so you know its topped up before swapping it round to power the charger !

pmullen503 05-31-2019 05:01 PM

A small gas generator (600-1000W) will also work but you'll have the noise. The initial cost is more than a new deep cycle battery but you won't have to worry about recharging or over discharging.

Wildflyer 05-31-2019 10:06 PM

Many of my friends use a separate full size car battery as their charging power. I don't think my best friend puts his charging battery on a charger more than once a month.
There are ways to hook up the "airplane" battery to the car so that the car will keep it charged while driving, yet separate them when you are using the "airplane" battery to charge aircraft.

I use my double truck batteries, I have a lead going back to the rear so that I can plug in my chargers.
I have charged 4 cell 4000mah batteries for 4 different teams of collage kids, probably 16+ times in one day with no trouble to start my diesel pickup after all that use.
A good condition, fully charged, large car battery, will provide many charges

solentlife 06-01-2019 01:20 PM

A good condition, fully charged, large car battery, will provide many charges
That's the main thing ... large and good condition.

But monitoring the state of charge of that battery is advised ... Lead Acid battery do not appreciate being left in partial charge state, second they should be at least in the top 1/3rd charged state ...

My cruising yacht has a double bank of 80 - 100A/hr car batterys. A 40A/Hr will do the job as long as engine is run often to charge it up ... but being a sail boat - its quiet and graceful under sail. The 40 would be cycling discharge / charge too much and life expectancy short. With Lead Acid - its always best to have MORE capacity than needed ... the battery will reward you with longer better service.

dereckbc 06-23-2019 05:38 AM

I can help you out a bit here as I work with batteries professionally. The answer you will like is YES you can do this, bu tnot quite as simple as it appears to be.

Pb batteries fall into three basic categories, of SLI, True Deep Cycle, and Hybrid.

SLI or Starting Lighting & Ignition are made to provide very high quick burst of current to crank and engine, and then be recharged just as fat, Those would be your car batteries. They are constructed of thin spongy plates that do not fill the battery jar to allow room for corrosion and flaking. Thise thin spongy plates provide low internal resistance so they can provide high currents. They are not made to be cycled and if pressed into deep cycle service will only have a shirt battery life. Dead giveaway is a SLI battery only specifies CCA and MCA rating with no RC or Amp Hours. Stay away from them.

A true deep cycle uses much heavier and thicker plates made to be deep cycled down to 80-% on AGM models properly maintained up to 1000 cycles or more. They cannot provide those high starting current, or be charged as fast as an SLI battery, A True Deep cycle battery will only have a Amp Hour Rating and some will have a RC rating.

Hybrids try to be both SLI and Deep Cycle. Plates are thicker and heavier than SLI so they can do some deep cycle work, but thinner than deep cycle so they can do some light cranking. Hybrids come with all kinds of marketing names like golf cart, wheel chair, trolling motor, RV and the list goes on. Dead giveaway it is a Hybrid is they will have CCA, MCA, RC, and Amp Hour rating.

Both Deep Cycle and Hybrid will work. All that is left to do is the battery math. Keeping it simple say you buy a 12 volt 100 AH deep cycle battery, and use say 3S 2200 mah packs. That will get you roughly 40 to 50 recharges,

solentlife 06-23-2019 10:03 AM

With respect and no argument with Derek.

There is a book that explains all simply and is my GoTo book on electrics ... it has provided many with sound and good advice :


by Alastair Garrod.

It explains the differences of Lead Acids and where they can be used. Although written for Boat owners ... its wealth of information is worth the read.

solentlife 06-23-2019 10:08 AM

A trick worth noting ...

Maybe like me - you go to the field with a number of LiPo's of varying size ? You decide because of conditions that day to only use a range of sizes leaving others unused ? Why not put them to good use in charging up the ones you are using ?

Many of the low to medium range chargers such as B5, B6, B6 mini, Accucel 50 .. 80W etc.; accept 12 - 18V input. As long as the supply LiPo is larger and exceeds 12V - you can charge up your smaller batterys and at same time reduce charge level of your unused ...

SoCal Perky 06-23-2019 09:46 PM

Thank You everyone who replied. The solution is in the replies and that are much appreciated ����

Turbojoe 06-24-2019 12:49 AM

I'm thoroughly convinced people WAY over think battery charging for a flying day. Preparation is always the key to success. Way back in the very early 80's when I was racing off road R/C I ALWAYS showed up with my cars fully rebuilt, ready to race and my NiCad packs fully charged. I always "peaked" my packs using a good old fashioned lead acid car battery just before I set the car down on the start line before each race. I was always first into turn one to miss the pile ups and won most races by a large margin because I made sure my packs had the highest possible voltage at the start and my cars were 100% race ready.

I still use the same procedures when I fly. I charge all batteries BEFORE I leave home. Now with LiPo's it's not as critical but sometimes I still do a "top off" charge using my car battery only if it's a performance plane I intend to fly. I NEVER worry about the car battery going flat and making me walk home. It just isn't going to happen. Again, preparation is the key to success. Charge all batteries BEFORE you leave home and have a great flying day. Be lazy and wait for batteries to charge at the field then you get to sit and watch others fly while you charge. I have NO sympathy for you. Forget about the field battery. If you charge before you get there and you need to charge again your car battery should be able to (within reason) provide more than several LiPos could pull from it.


solentlife 06-24-2019 01:17 PM

Joe ... generally I do not think anyone is advocating arriving at flight site with minimal setup. I know for myself - I have a number of each size LiPo and occasionally because of conditions - find myself short on a particular pack.
A field solution then is an advantage.

When our club has open meetings and we have various 'guests' from other clubs ... even countries - often we have the Gaui Heli Demo guys. They have 12S setups and a generator.

As regards Car Racing and NiCd days ... I did indoor car racing (hours spent applying silicon to tyres !!) running on gym floors etc. Most people only had the one pack fitted into the car unlike todays LiPo jobbies.
I used the following based on Lead Acid :


The top one powered from 12V Lead Acid .. bottom one from mains 240V.

Clockwork timer .. all designed to max charge in the pit time between races. We had fans cooling the batterys while we charged to get maximum mA in ...

Samman37 07-03-2019 03:09 PM

I've mentioned that the plane batteries can be charged by a generator, especially when you're outside the house or even drive somewhere and don't want to use your car batteries. One of my friends was offering me to try it, I haven't decided what to buy for now but find a blog with kind of good reviews about them (view it). And now after that, I've started to think about rather a big guy who can charge not only my plane but a car too. Maybe you shoul think about solar generators. :confused:

solentlife 07-03-2019 04:34 PM

Solar may seem a good idea ...... but start calculating panel needed ..

Lets say a B6 charger at 50W. It needs a minimum of 12V at 5A to even start to charge at low to medium rates in the 2 and 3S ranges.

Solar panels .. I have a 1ft square panel sits on my motorboat to top-up the SLA battery that runs my auto bilge pump ... that panel is 12v at 0.6A ...

That means to get equivalent to the power - is 10 panels .....

Once you factor in the voltage drop and sunlight factors - you can double that ... portability now seems to be 'out of question' ... unless you cover roof of your trailer / vehicle ?

Samman37 07-04-2019 12:35 PM

Originally Posted by solentlife (Post 1019585)
Solar may seem a good idea ...... but start calculating panel needed ..

Lets say a B6 charger at 50W. It needs a minimum of 12V at 5A to even start to charge at low to medium rates in the 2 and 3S ranges.

Solar panels .. I have a 1ft square panel sits on my motorboat to top-up the SLA battery that runs my auto bilge pump ... that panel is 12v at 0.6A ...

That means to get equivalent to the power - is 10 panels .....

Once you factor in the voltage drop and sunlight factors - you can double that ... portability now seems to be 'out of question' ... unless you cover roof of your trailer / vehicle ?

For better understanding, I wasn't talking about standard solar panels or flexible panels. I was talking about the generator with solar modules, like Wagan (EL2547) or something like it. But, for camping somewhere aside from civilization seems to be not so bad idea to take some additional panels with you.

For about the car - no way for me for now, because I'm a brave owner of Suzuki Swift 2007... The roof is not so large for such modernization.

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