Question Using a car battery charger as a power source. What's the problem.

[Boeingdvr]

Ok, I'll start right out by saying I know very little to nothing about batteries, chargers, omhs, Amps, and the rest.
I was down at the LHS yesterday and asking questions and looking to buy Lipos for a Parkzone PNP Typhoon. The sales guy recommended Thunderpower 21oomAh battery packs and a Hobbico Quick field Charge mkII. He then remarked that all the mkII needed is a 12v power source from either a 12v battery or a power supply. I asked why not use a automotive deep cycle battery charger as a power supply and he remarked that it wouldn't work as the auto charger didn't have enough amps to do the job.

Ok, what am I not seeing here. 12v 10amp deep cycle Schauer battery charger should have the ampage right? I got about 13.4v out of the charger and that is within the mkII input pwr range. I will confess that I have been using this auto charger on my Hobbyzone field charger that comes with the aerobird extreme and it seems to work charging the 6 cell NiCd and NiMh.

So why can't a auto charger be used as a power source? I bet there is a bunch of electro wizards shaking their heads as they read this but that's why I just fly em I don't try to fix em.

PS I did read the mkII instructions and it also says not to use auto type chargers to power the mkII. Inquiring minds need to know why!

Thanks for your help guys. These threads have helped a me get back into RC and really enjoy electric planes. Things have gotten so much better (and a little more complicated) in 20+ years.

Boeingdvr

[everydayflyer]

Atomotive battery chargers are not well regulated or filtered. They have to much AC ripple / spikes on thier output. They work fine if you hook them to a 12 volts battery and the MK II to the battery. The 12 volt battery acts like a very large capacitor.


Charles

[warren52nz]

I agree with Charles. And you could also use just the charger and a big electrolytic capacitor on the charger (without the car battery) to the same effect. (Something like 10,000 uF at 25 volts). If you're doing this yourself make sure you hook up the capacitor the right way around (plus to plus....) Otherwise they explode in a rather impressive way!!!

I'm assuming the charger can deliver enough amps and that your Li-Po charger can handle the voltage from the charger. It's likely that adding a capacitor to the car charger will put the voltage up to something like 16 volts DC. The capacitor makes the voltage sit up on the peaks of the unfiltered waveform. To be safe you should measure the voltage after adding the capacitor and then check your Li-Po charger is rated for that voltage.

BTW, the capacitor will make it charge car batteries faster (at a higher current) too.

[abenn]

OK, my charger isn't a Hobbico, but when I was using a motorcycle battery with a car battery charger as a power source it used to trip out due to either too high input voltage (if the battery charger was switched on and the charging current was low) or too low input voltage (if the battery charger was switched off and the charging current was high)

Like Charles has said, car battery chargers are not well regulated voltage-wise, so the voltage swings by a large amount depending on load. I bought a dedicated stabilised 12v (nominal) mains power supply unit, and that's solved the problem

[JIM CALDWELL A]

Field charge set up I have been using for 10 years with no problems other than replacing the 12 volt trolling deep cycle battery after 7 years, $65.00 Walmart.

12 volt Deep Cycle Trolling battery Group 24 75ah size.
Schauer 10 amp battery charger (27 years old)
Chage the first set of batterys at the field with out the charger hooked up to lower the the voltage, then hook up the charger and you can leave it all day.

No AC at field? charge from from trolling battery until the eye changes from green to black hook to car using jumper cables and charge for about 1?2 hour and you will be good for the after noon.

For the F/E Boat Nationals last year I decided to up grade to a Schumaker
2/12/25 amp charger because I was going to be charging 3 packs 3 times a day. It has 3 settings - reg. battery, voltage goes to 15.5 volts
deep cycle, voltage goes to 16.5
AGM, voltage limited to 14.2
All at the 12 amp charge setting. same procedure as above.

ALL WAYS charge the battery up when you get home and charge once a month during the winter and it will last for years.

[charge1(ds)]

If your going to use your car it has to be on. you don't want to finish a day strong and call someone saying my plane batteries killed my car batteries. You can use that power supply its just no good. you can pick up a nice power supply from a lot of different companies.

[gunracer]

Originally Posted by charge1(ds)

If your going to use your car it has to be on. you don't want to finish a day strong and call someone saying my plane batteries killed my car batteries. You can use that power supply its just no good. you can pick up a nice power supply from a lot of different companies.

* * *

i guess it depends on how many packs your're charging and how big they are...i routinely charge 8 3s 2100 lipos along with 5-8 nimhs on my non-running car batt and she starts up everytime...

[everydayflyer]

Thousands of flyers use their car batteries as a source to charge at the field. This has been done for many ,many years. I charged NiiCads from the car / truck battery for approx. 20 years. Some electric flyers are smart enough to kep an eye on the automotive battery's state of charge and many smart chargers will not function if the supply volts is to low. On most chargers this is designed to prevent over discharging you 12 source battery and stranding you at the field plus it is never a good idea to deep cycle a standard automotive battery. .

Some electric flyers have extra large capacity deep cycle batteries (sometime more than one) and extra high output alternators installed in their vehicles.

I used the jumper cables rountine to charge a smallish marine deep cycle battery many years ago when I only had a small Alum. John Boat and elec.trolling motor.Some weekends between fishing and camp lighting the trolling battery needed a boost.


Charles

[hall woo]

saw an ad about a welding system using the alternator long time ago

[Lee]

I had all kinds of troubles with my MKII chargers until I went to a quality power supply like the one sold at Lightflight. I have 2x MKIIs hooked to each 12v/13A power supply. (Mine are Cosel brand)

I would get frequent alarms and I killed a car battery even though I was charging it between charging my lipos. I don't think it was the MKII charger I think that the car batteries were not designed for trickle charging. It's like leaving the lights on.

I now have 4 of the MKIIs and charge 8 batteries at once. Very dependable and the chargers seem to alarm early if they are having a problem with a abnormally charging battery. I recomend the chargers.

One of the flyers in our group uses a 12v/6A transformer that was designed for giviing power to a portable electric ice chest. It wasn't very expensive and he got it at Target.

[mohillbilly]

The MKII is a very forgiving charger, I used to run mine off a small lawn battery w/ a car trickel charger hooked to it at all times. Then I started using a very old pc power supply that I later found out was droping to 10.3V if charging with both stations at Max amps (4A total). Has yet to trip the low vlotage with that supply.

Mo.

[Dennis157]

FYI the MarkII is not a real good lipoly charger. It is actually designed for
liion batteries it wont charge fully to 4.2VDC other than that its a great field charger



The DC supply that comes with a AccuCycle Elite has no filtering, just diodes &
xformer , it works fine. According to Red S. site ,cells can be charged using
a pulsating DC componet.

I think the reason some auto batt chargers wont work properly, is because they
have regulation circuit that adjusts to batts chg level. Their made to see voltage
coming in to them, not just deliver a steady source. I tink?