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Old 07-12-2016, 10:40 PM   #1
Atraxas
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Deep cycle battery to power a charger and charge lipo packs


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I have a couple 2800 mah lipo packs for my plane and possibly getting more with a higher amperage.

I am trying to find a deep cycle marine battery to power my Hi-Tek X4 balance charger so that I can continuously charge my lipo packs while at the flying field.

The marine battery would be my main power supply and wanting to know if anyone has tried or using this type of set up, because I would not want to get a battery that would last me 2-3 charges before having to recharge it.

I used to have my charger hooked up to my car battery to charge my packs but I have been told that car batteries are not meant to have power pulled from them and by doing this it shortens the life span of a car battery.
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Old 07-12-2016, 10:57 PM   #2
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Re: Deep cycle battery to power a charger and charge lipo packs

Regarding using your car battery as a power source and worrying about shortening it's life is not totally true. The difference between a auto battery and a deep cycle battery is the auto battery can supply large amounts of current over a short time and will recharge quickly. The deep cycle will supply smaller amounts of power over a longer time and can be discharged to a lower level but it takes much longer to recharge. I have tried to simplify the comparisons here but am sure that we will get lots of correcting comments. Another consideration with today's new cars is that most are equipped with minimum sized batteries
So you may not have a lot of charging ability. Just make sure your lipo charger can be set to cut off when the source reaches 12v or you may find a jump start may be needed.

If the plan is to charge high capacity lipos and if you plan on doing lots of charging , a good plan would be to series connect two 6 volt golf cart or deep discharge batteries in series for your 12 volts and much more capacity than a single #27 deep cycle. Another consideration is to have axcess to the innards of your batteries to be able to monitor the acid level and replace with distilled water before the level gets down below the plates as that could create sulfation and shorten any lead acid battery.

The last alternative is buy yourself a Telsa and you can charge everyone's batteries with no fear of running short ...LOL.

Last edited by stegl; 07-12-2016 at 11:04 PM.
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Old 07-12-2016, 10:58 PM   #3
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Re: Deep cycle battery to power a charger and charge lipo packs

I have a deep cycle marine battery and I charge my 6s 5500 and 6s3300 no problem.The battery is a Alliance Marine rated at 675cca 875mca.
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Old 07-13-2016, 05:46 AM   #4
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Re: Deep cycle battery to power a charger and charge lipo packs

Should do the job, better than bringing a noisy generator to the field.
Keep your wires short and use good connectors.
Higher cell count does cause the charger to kick out, try your car batt for a test, connecting directly to the car battery.
At least you won't have a dead car battery.
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Old 07-13-2016, 07:13 AM   #5
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Re: Deep cycle battery to power a charger and charge lipo packs

difference between a deep cycle and a standard car battery of today is the car battery is designed to maintain a much mote constant voltage (kind of like the difference between a123 and nicad batteries )car batteries will work fine if you keep it in is't operating range .but don't take it much below 12.6 ocv . . they are designed that way to give stable voltage to the electronics on the car . they will be damaged if cycled to low . a deep cycle will maintain output at much lower voltages without damage , this type of deep cycle battery raises havoc with the automotive computers because the voltage range can drop too low for proper computer function . a deep cycle battery in you car can also fry your alternator because they will hold the aletenator in the charge cycle too long . I use ultima marine battery .cheers Roger
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Old 07-13-2016, 07:37 AM   #6
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Re: Deep cycle battery to power a charger and charge lipo packs

I would think it much simpler to access the vehicle battery itself, rather than drag another to the field. There should be enough reserve to carry you through a normal flying session.

If afraid of being left with not enough to start the vehicle there are a couple of options. Start the vehicle to rewind the legacy battery part way through the day, (more on that next) or use our trailer setup with a charge/discharge control to allow the vehicle to charge a second battery but isolate it from the vehicle once that charge stops.

One thing I noticed with my CellPro charger was an error code when trying to work with 4S and above due to the static battery voltage. Would disappear if the van started.

ps. I modded my van right after purchase with the intent of this type of app and to isolate a trailer from the van lights. Found on some the extra current of trailer lights could trip the headlight current breaker, burn out the vehicle turn signal switch and with newer vehicles seriously affect the flash rate. I used electronic relays I had grabbed off Fleabay a while ago on all 3 circuits.

The only way this worked is the original 7-pin plug also includes fused vehicle power, direct off the battery accessory terminal, I used that as the source while the original circuits were for activation only. That source also allowed me to install a general-purpose lighter plug near the back and I built a rig with two heavy leads and banana receptacles to adapt most DC charger power in leads. It also allows me to plug in the small solar panel I purchased from Can Tire when on sale.

Been years since I owned a boat, but at that time marine batteries had pitch valves that would prevent leaking acid if the boat turned turtle. They also had a gas port to allow a vent hose connection. Wonder if anything has changed there or if that has made it to land use.
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Old 07-13-2016, 09:02 AM   #7
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Re: Deep cycle battery to power a charger and charge lipo packs

I use a booster pack but I don't know how many charges you would get. At my old club I had to use it to boost someones truck after he charged 4 large packs off it. I took a training course from Exide and we were taught that a car battery is not made to be discharged. It reduces the capacity of the battery. As someone stated in a above post. A car battery starts the car and then the alternator takes over. That's why in the winter time driving short trips with all your accessories on will discharge the battery. Your alternator can't put out much power at idle. At my new club we have a member that has a small Honda generator that is so quite you wouldn't know its running. He has a long cord and has it away from where the members sit. From what I've seen you either need to charge them at home before you fly or invest in a generator unless you can pay to run a Hydro line. I fly small electrics and charge all my batteries at home before I fly. I still fly glow and don't see myself switching my bigger planes over to electric power because of the batteries. Cheers Floyd
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Old 07-13-2016, 09:08 AM   #8
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Re: Deep cycle battery to power a charger and charge lipo packs

As stated... the capacity of the lipo isn't the whole story. A 3S 2800mAh requires less power consumption compared to a 6S of the same capacity to charge at 1C:

3S @1C draws 11.1*2.8 ~ 31 Watts
6S @1C draws ~ 62 Watts.
3S @2C draws ~ 62 Watts.
etc...

Your charger needs to manage the difference between input voltage and the output requirements, so there's also some effeciency loss. (I.e. higher power consumption).

Based purely on manufacturer specs, there's a simple calculation:
(10xAh)/Watts = Runtime

Let's look at a smallish Marine Deep Cycle battery rated at 70Ah.
Charging a 3S 2800mAh lipo at 1C gives: (700/31) = 22.5 hours of runtime

If it takes 60 minutes to charge from depleted, that translates to about 22 charges. The real number will be lower based on efficiency losses, and how long the charger stays connected, etc.. But it's a good guideline even if you're parallel charging. (Though... charging 10 lipos at the same time would introduce some other factors related to very high current draws... so, let's assume no extreme cases)

It's also important to note that you really don't want the full capacity of your deep cycle battery (much like you don't want the full capacity of a lipo). Ideally, you want to stop using a Marine Battery when its volage drops to 11.6V (20% left) and you never want to go below 10.8V under load. There are many arguements for respecting a cutoff voltage at 12.1V (50% left) for long term battery health.

In the end, you'll size a deep cycle based on the draw you need combined with your prefered cutoff voltage. Have a voltmeter handy when you use your setup the first time. It's a good way to verify that all is well.

An additional cost consideration is charging the marine battery. I initially used my RC charger, but eventually bought a marine battery charger for the ease of use and peace of mind.
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Old 07-13-2016, 09:16 AM   #9
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Re: Deep cycle battery to power a charger and charge lipo packs

That's difficult to believe about alternator output at idle. Unlike generators their purpose was to have variable output regardless of RPM based on field strength, controlled by the regulator. Yes, under heavy load there may be some limits on output current, but not as much as you would expect. Even back in the 90's Ford had their heated windshield that was a bit unique. Once the vehicle was started the system looked at battery reserve and if deemed adequate switched the alternator to 120VAC output tied to the windshield alone while the battery covered all other systems, (including heater blower, etc.). Mind you, the design was intended to burn off up to an inch of ice pretty quickly so the cycle time was not that long, but the other loads on the electrical system could still be substantial. Far more than I expect our chargers would require unless into the high capacity and cell count packs.

Since my van had the heated seat option the stock alternator is 160A. Think at idle there would be enough reserve to carry remaining loads. On that note the stock battery was coming into its 6th winter with no discernible loss of start power. When in the trade I usually recommended replacement before the 4th since saw far too many struggle in cold temps.

As for discharge; your battery should be rated for Cold Cranking Amps and even with numerous LiPo recharges should have enough reserve if topped up on the way to the field. I suspect the truck in mention may have had a weak or old battery or another problem.
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Old 07-13-2016, 11:56 AM   #10
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Re: Deep cycle battery to power a charger and charge lipo packs

Bad Idea to use the on-board car battery , the alternator in the cars today put out around 100-160 amps . by running your battery down you run the risk of burning out your alternator .it is also recommended if at any time you run your battery down you must charge it to 12.6 ocv before trying to start the car or alternator damage may result.

The worry is being left with just enough battery to start the car . a low battery will demand full alt output for far too long and will result in damage to the alternator . think about this 160A for let's say 1/2 hr while the battery charges to a safe level ,that is some massive heat build up . remember these alternators need to keep full voltage even at idle for the computer to function correctly that is why they are wound to have such high output even at idle . I have had guys come to my shop after changing 3 alternators scratching there heads and before even looking at it I know they have a battery with a low cell , it will start the car just fine because of the new low draw starters ,problem is when it does start with a low voltage battery the alternator can never reach shut down voltage so it runs it's self to death.

all new alternators now come with this warning .(min batt votls 12.6)



Get a deep cycle battery and charge it at home .
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Last edited by RAMJET; 07-13-2016 at 12:43 PM.
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