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-   -   Car battery for field charging? (http://www.Wattflyer.com/forums/showthread.php?t=74042)

MKE-Flyer 07-08-2014 03:05 PM

Car battery for field charging?
 
Can I just use a simple car battery to charge my LiPos on the field? I just inherited a car battery charger and I figured it would be cool to have batteries charging while flying. I see people use Marine batteries but they are out of my price range, I would like to stay in the 50-75$ range.

Batteries I will be charging (1.8A, 2.2A, 3.2A & 3.3A LiPo)

Thanks

rcers 07-08-2014 03:10 PM

Car batteries are VERY ill suited for deeper discharges. Remember their purpose is to provide VERY small, large bursts of power for the starting motor and initial electronic demands - then get charged right back up.

Due to this special purpose they have relatively small capacities. Once the car is running the alternator runs all the stuff and even provides power to recharge the battery. Think about it - most batteries in a car will be COMPLETELY discharged after about 30-40 seconds of running the starter motor.

Most decent sized car batteries would only allow for 4-5 charges of a 2200 3s pack before being nearly completely "empty". Some large trucks and SUV's have larger batteries, but most cars just have to supply 3-4 seconds of cranking power then they are done. So they make em to do just that - tiny crank and then get recharged.

Thus the reason for using deep discharge (marine or RV type) that are much higher capacity and are OK with being further discharged. This is needed for boats as most runs are short and you turn the engine off, then re-start, then off etc. RV's you sit and run lights and other accessories and they need much higher capacities - and more importantly the cells are used to being taken to lower voltages. That can kill a car battery in short order.

Sorry man...

Mike

MKE-Flyer 07-08-2014 03:25 PM

I can get this for 72, would be any good?

http://www.kmart.com/diehard-marine-...irectType=SRDT

rcers 07-08-2014 03:30 PM

Not sure - I find the super cheap marine and RV batteries are well, super cheap. :)

I have a gate at the house that uses a 12v battery. They don't last long here in the TX heat. When I got cheap batts they lasted a year, and when I got good they lasted 3 or 4 years. Now I just leave the gate open. LOL. I am going to wire that, at some point to simply use AC as the battery cost is just too high!

You really do get what you pay for....IMHO

But it might be OK for a while - hard to say. You will be better temp wise for sure - high heat kills batteries...

Mike

MKE-Flyer 07-08-2014 03:32 PM

This is for flying once a week on the field, I just found this for $76 after online discounts. Seems to have more Amps and runtime.

http://www.kmart.com/diehard-marine-...irectType=SRDT

solentlife 07-08-2014 04:45 PM

Car Breaker Yard ............ go and get a second hand battery ... they are cheap - breaker yards have a load tester to check battery is ok ...

Being cheap - means that when it starts to go down hill after a year - it's no big deal to go get another. Take old back to the yard - they'll usually give a $ or so of the replacement for scrap value.

Just because it's a scrap yard - doesn't mean that the batterys are no good ... car gets totalled in a crash - but parts etc. are still good.

Saves a lot of money .... and your standard car charger ... or as I have a splitter system that charges along side the cars own battery.

Nigel

fhhuber 07-08-2014 05:59 PM

It really depends on how much charging you will be doing...

A couple of charges of a 3S 2000 mah pack then take the car battery home and recharge it and you'll be fine. but if you do 3 charges of 12S 5000 mah you won't finish the 3rd charge and you'll damage the car battery due to the deep discharge.

Marine batteries from WalMart are in your price range and a better choice than a car battery because the plates are designed to handle a deeper discharge. But even then you can over-discharge and damage the battery.

No matter what type battery you choose as a source for field charging you have to monitor yow deeply you are discharging and stop before the charger's typical cut off due to low input voltage. Regularly hitting the charger's cut-off will destroy even the deep cycle marine batteries.

I've used deep cycle marine batteries in a solar system on my model hauling trailer. Worked fine for 5 years service. (5 years is pretty good for a deep cycle marine battery) I've gotten hold of some LiFeMgPO4 batteries now, which can handle higher current and deeper discharge. Increased my solar panels to 100 watts of panels and can now deliver 100 amps for 5 hours before needing to worry. (I can supply EVERYONE at the flying site... until I get my big Me262 built)

rcers 07-08-2014 07:17 PM

Indeed - batteries are all damaged by deep discharges, even Marine type.

That is why I use a cheap generator when I am at field without power. I am super lucky that our field has AC outlets on all the tables. I'm spoiled.

kyleservicetech 07-08-2014 07:36 PM

Quote:

Originally Posted by MKE-Flyer (Post 952507)
Can I just use a simple car battery to charge my LiPos on the field? I just inherited a car battery charger and I figured it would be cool to have batteries charging while flying. I see people use Marine batteries but they are out of my price range, I would like to stay in the 50-75$ range.

Batteries I will be charging (1.8A, 2.2A, 3.2A & 3.3A LiPo)

Thanks

Those Marine batteries are rated for discharge in about 15 - 20 hours or so.
So, if you've got a decent 70 Ampere Hour deep cycle battery, you can discharge it at 4 or 5 amps and do fairly well. Once you start pushing 10 amps or so, you need to go to a big heavy 120 Ampere Hour battery.

In my case, I'm pulling 50 Amps out of my 12 Volt DC source, and that results in killing even a very good quality 120 Ampere deep cycle battery in only a few months.

The problem is, at very high discharge rates, where the lead acid battery is discharged at 1/2 C (60 Amps) or so, the effective ampere hour rating of these batteries drops like a rock. Like down from 120 Ampere Hours to 50 Ampere hours.

For my two high powered Cellpro Powerlab 8 chargers, I'd need three or four 120 Ampere Hour deep cycle batteries in parallel. That's one of the big problems with giant scale models with 12S battery packs. IOr in my case, a 12S2P A123 pack that is charged as a 6S4P pack. With a charging current of 30 Amps. What do you charge them with???

This is what I use.
Harbor Freight Gasoline/Alternator Setup. That Harbor 6.5 Hp Freight Predator engine now has 165 hours on my hourmeter. It still starts on the very first pull. Every time. (This allows charging my 12S2P A123's as a 6S4P with a charging rate of 30 Amps. That allows recharging my models in 15 minutes)
http://www.wattflyer.com/forums/showthread.php?t=66066

And lead acid battery issues:
A123 Batteries outlast my lead acid deep cycle battery?
http://www.wattflyer.com/forums/showthread.php?t=48469

http://www.wattflyer.com/forums/showthread.php?t=65723

dereckbc 07-08-2014 10:19 PM

SLI batteries, car starting batteries do not not react well to cycle service and will significantly shorten their life.

A better method is to buy a good AGM deep cycle battery, charge it up at home and take with you.

kyleservicetech 07-09-2014 12:40 AM

Quote:

Originally Posted by dereckbc (Post 952553)
SLI batteries, car starting batteries do not not react well to cycle service and will significantly shorten their life.

A better method is to buy a good AGM deep cycle battery, charge it up at home and take with you.

As an example, you can buy a electric power substation back up battery (Price is $800 or so.) with the part number STT12V150, which is a 150 Ampere Hour 12 VDC battery. These batteries are rated for an 8 hour discharge time.

Their specifications indicate that this battery is only good for 90 minutes at 60 Amps. That translates to 90 Amp Hours or 90/150, which is 60% of its rated 150 Ampere Hours. And, this battery weighs in at 165 pounds! That's double the weight of a typical 120 Ampere Hour deep cycle battery.

Based on this info, that 150 Ampere Hour battery would only be good for four flights before it is totally discharged. So, if you want to pull about 60 Amps out of one of these batteries and get 6 or 8 flights out of it, you'd be looking at something like a 350 Ampere hour battery.

On the other hand, this 150 Ampere Hour battery is the SMALLEST battery size of the STT type. These batteries range up to 3000 Ampere Hours. You'd better have a big truck to haul one of these around. (Yup, I've seen these big batteries. They just about need a fork lift truck to move them.)


So what is Wallyworld selling?

dereckbc 07-09-2014 01:32 AM

Quote:

Originally Posted by kyleservicetech (Post 952567)
As an example, you can buy a electric power substation back up battery (Price is $800 or so.) with the part number STT12V150, which is a 150 Ampere Hour 12 VDC battery. These batteries are rated for an 8 hour discharge time.

What you are referring to is Peukerts Law which is most pronounced in Flooded Lead Acid Batteries. It is mainly due to internal resistance losses in the battery. AGM batteries particularly pure lead types are not so drastically affected by the Peukert affect. In fact some are very good like Concorde and Odyssey. They do not cost the xtremes you are speaking of.

For example a Odyssey 31M-PC2150 cost roughly $300 and rated 100 AH @ 20 hours and 92 AH @ 10 hour discharge rate. Price is still high, but Peukert affect i snot extreme.

If you want the best money can buy then Concorde is the Cadillac of AGM batteries as they invented them for military aircraft and expanded into consumer markets, racing, marine, RV, and solar. If you want a Beast of a 12 volt battery then Concorde PVX-1530T cost is roughly $385 rated at 150 AH @ 20 hour, 135 AH @ 10 hour, and 124 AH @ 5 hour rate. These batteries you can take down to 80% DOD and still get 1500 cycles out of them. If you are using 3S 4 to 5 AH packs that is 20 recharges in a day.

But it is not nessecary to get a beast of a AGM battery. A good light weight 40 to 60 AH model costing around $100 to $150 is all that is needed along with a home charger and set of Jumper cables for the field work. If the battery gets low in the field, hook up your jumper cables and idle your vehicle engine for 30 minutes. Or if you want to be Joe Cool get a 200 watt solar panels and a 20 amp MPPT charge controller and you can set out there for a years if you want and fly.

Money no object for you? Do not want to be bothered by Mr Peukert, and light weight, well get a EV LiPo battery like Thundersky or Calib 4S 100 AH pack for $300. I use 4 of them them in my 48 volt racing golf cart. It will climb a tree, pop wheelies, and burn rubber. 0 to 30 mph in just over 1 second.:D

fhhuber 07-09-2014 02:02 AM

You don't need 200 watts of panels... 100 watts of panels is more than enough to charge 3S 4400 mah at 1C without even having a storage battery even if the panels are not at the best angle for collecting solar energy.

Many of our chargers are rated 50 to 60 watts. You can do a lot on just the 45 watt solar system from Harbor freight.

carpetbagger 07-09-2014 02:22 AM

"car breaker yard" HA! I like that term. We call them "boneyards" or "junk yards" and they are always a good source for cheap car parts.

My charger, which charges all sorts of batteries, runs off 12 volt DC or 115 v AC. Haven't tried it on my truck battery yet since it is 9 years old and probably ready for recycling.

For a charger battery a Deep Cycle would be best. Big, heavy, and $$$. I would probably opt for hauling my Honda EU2000i generator.

kyleservicetech 07-09-2014 05:05 AM

Quote:

Originally Posted by fhhuber (Post 952579)
You don't need 200 watts of panels... 100 watts of panels is more than enough to charge 3S 4400 mah at 1C without even having a storage battery even if the panels are not at the best angle for collecting solar energy.

Many of our chargers are rated 50 to 60 watts. You can do a lot on just the 45 watt solar system from Harbor freight.

Yeah
That's one of the big negatives for those 12S2P A123's in my giant scale models.
The good thing, they can be recharged in 15 minutes. :D
The bad thing, my two Cellpro chargers are pulling a combined 950 Watts out of my 12 Volt DC supply. :censor:

(Ref http://www.wattflyer.com/forums/showthread.php?t=66066)

solentlife 07-09-2014 06:25 AM

Quote:

Originally Posted by carpetbagger (Post 952584)
"car breaker yard" HA! I like that term. We call them "boneyards" or "junk yards" and they are always a good source for cheap car parts.

Same whole world over ...

Quote:

My charger, which charges all sorts of batteries, runs off 12 volt DC or 115 v AC. Haven't tried it on my truck battery yet since it is 9 years old and probably ready for recycling.

For a charger battery a Deep Cycle would be best. Big, heavy, and $$$. I would probably opt for hauling my Honda EU2000i generator.
Why I suggest the Breaker yard battery is that it's cheap ... will last maybe a year and it's no big cost to replace with another. On my yacht and my other boats (I have 4) .. I use them and they get hammered hard ... main yacht is into years of use already and they are fine. If you plug a charge splitter in your car and keep it topped up while driving etc. - as you would with a Caravan - then it will last a surprising length of time.

$300 ?? how many Breaker yard battery's could you buy with that ? Just for arguments sake - the yard asks $50 for a HD 100 A/hr job ... that leaves $250 you can either take wife / girlfriend for a meal or buy a bag of LiPo's .. :rolleyes::rolleyes:;););) or of course send me the balance as a thank-you !! :D:D:p>:p>

Nigel

dereckbc 07-09-2014 04:54 PM

Quote:

Originally Posted by fhhuber (Post 952579)
You don't need 200 watts of panels... 100 watts of panels is more than enough to charge 3S 4400 mah at 1C without even having a storage battery even if the panels are not at the best angle for collecting solar energy.

Many of our chargers are rated 50 to 60 watts. You can do a lot on just the 45 watt solar system from Harbor freight.

You are right, you can use smaller wattage panels, but Grid Tied Panels are half the cost of battery panels.

Those Harbor Fright 45 watt panel kits the box is worth more than the panels and controller that it comes in. If you are lucky at solar noon you might get 2.5 amps for a few minutes. A good Grid Tied 200 watt panel with MPPT will give you 16 amps on a 3S pack.

Besides I design off-grid solar battery systems and have all the stuff I need to anyway. If I remember correctly those HF 45 watt kilts cost around $200. I can buy a 200 watt grid tied panel for $150 and they can be used to charge up to a 6S pack directly without a controller at 7 amps. What is not to like? More power, better quality, and less money. :D

solentlife 07-09-2014 05:25 PM

Being also a Yachtie ... the subject of Solar Panels is a serious matter and to be honest was a cure for insomnia for me !!

Sorry to peeps here....

I came to conclusion that my amount of use vs cost of the panels etc. meant I needed to live a very long and healthy life to cover the costs ...
That was on a boat that they could be mounted and not intrude on others.
But looking at modelling ... because I fly at various sites and not just one - the thought of carrying such capability around in my mind is not practical. If you can permanent rig a set-up - fine great ... but if like me - you have no real permanent site - then it's back to more portable solutions.

I will add this as well ... if it's considered that Solar is going to be transported to / from each site - then you need the 'walk-on' type ... that is the type that can take punishment to avoid cracking the 'glass' that's got the cells embedded in ... I had a beaut of a panel few years back - guy who gave up yachting gave me his .. it got cracked in the back of my Land Rover one day and that was it ... a very expensive looking glass then !

Nigel


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