striderjg

What should I use to charge my field bat. It's a hobbico torqmaster. I have available a 13.2v transformer. Can't remember the amps it's rated for but it's high enough. A dymond super turbo. Will either of these work. I know the super turbo is only designed for ni(cd/mh) but is it possible to charge a lead cell with it? Anyways, that's all.
TIA
-John

JNorton

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John
Let me tell you what 7 Ah gel cells don't like. They don't like to be charged with over 700 mA. The don't like to be deep discharged to 12 volt. They do like to be topped off regularly. I do this by first charging the battery. I have a 30 minute trip to the field each way. I use a Radio Shack cigarette fused adapter in one car and plug directly into the field box. The cars regulator keeps the field battery topped off. Do not do this if the field battery is fully discharged as it will pull more than 2 amps overcharging the battery. My flight box battery is now 4 years old with no problems starting a 1.20 Enya.

Most car parts stores sell a battery tender for small lead acid batteries for around $40.00. These will charge the battery then taper off to a float charge.
http://batterytender.com/default.php?cPath=11_3

A small 500 mA charger only for $8.00. Remove it after 14 to 16 hours
http://www.maxxprod.com/mpi/mpi-9.html

John

JNorton

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Red has a great section on lead acid batteries on his site. http://www.rcbatteryclinic.com/
John

jlkonn

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I bought one of these at Walmart for less than $20.
Last time I looked a couple weeks ago they still carried them.
I used it on my field battery, my riding mower while it sits over the winter and the old '84 CJ-7 that mostly sits in the garage.
http://froogle.google.com/froogle_cl...ring=mrd&hl=en
JLK

jlkonn

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Oh,
It does have a 1amp/off/2amp selector switch.
JLK

striderjg

First off, thanks everyone for the responcs.
Ok... i've been doing some reading. I'm really can't spend money right now, so I'm trying to exhoust all the options I have first. I solder'd up some bannana plugs onto my 13.5V transformer to give that a try. From reading seem'd like it should be safe for the battery. I tested the current it's feeding to the battery and there's the problem with that one. 60mA. That could take a while I have it hooked up anyways right now, as the batteyr has been sitting around for a long time and is really completely discharged. And actually the current has gone up by 20mA over th elast hour or so (started at 40ma), so I'll check it again in a little while. I do have a Exide Automatic Nautalus marine/auto 10A charger that I use for my car. Would this work by bulk charging at first and then flipping into float mode near end to keep from over charging. I would think the amps at the bulk stage would be to high, but I'm not sure. I tried ot find some info on the system the charger uses but couldn't find info on my model. I would think it follows what some others do, and uses a bulk, absorbtion and float stage. Bulk for initial charge to 80% or so at full current, then absorbtion with a 14 or so constant volt, then a float in the 13.5ish v range at just about topped out charge. Would the fact that the large current is only being applied to get the battery up to 80% change anything? I actually fired off a e-mail to Exide asking them if the charger could be used with this small of a capacity batt. If all else fails I'll shell out the cash for a float charger. Lol. I've just spent too much money currently, and trying to get away cheap with this one. I know it's not a lot, but u also don't know how broke I am Anyways, thanks all for the help.
-John

JNorton

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That's AC don't do it without a rectifier bridge you'll RUIN your battery!!!!!!

JNorton

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A small 500 mA charger only for $8.00. Remove it after 14 to 16 hours
http://www.maxxprod.com/mpi/mpi-9.html

striderjg

no, it's dc. 120v ac input, 13.5 dc out.

JNorton

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Cool I'm glad I misunderstood. A 13.5V transformer puts out AC. A wall wart can put out DC or AC. Just semantics but anyone trained in electronics would immediately think AC.

JNorton

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Please don't do this the current would be way too high.

If the battery charge is picking up it's a good thing. Keep using the 13.5 VDC wall wart.

striderjg

That's what I figured on the marine charger. Oh well. Just looked tranformer up. Guess i've been using the wrong term for years. Lol. Good to know. I'll leave the wal-wart on for the night and see what kinda current it's passing in the morning. up to 100ma now. The battery was stone dead. I think around 10v. Can gel cells cells reverse polarity? I have a bunch of old cig adapters laying around. I'll strip one of them and use it in car like u suggest when I get my plane ready to go to the field.
Thanks
-John

fredscz

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HARBOR FREIGHT had their battery tender on sale for $7.99 in the last flyer I received from them. I've been using one on my 6 year old flight box battery. I fly two/three days a week in good weather and no problems so far [kow].
FEB

striderjg

Update. This morning, battery was soaking up power at 600ma. That seems moer like it, and voltage on the battery was between 12.5 - 13v. Seems like this wal-wart might be just the trick. Although I'll see if it's able to top off the battery, and how much it's gonna slow down when the battery gets near full. One question. Those wal-warts ppl have posted. Are they constant current, or just like mine. Higher voltage, so differance causes current to move towards battery with a rating of 500ma max?
-John

JNorton

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Either or it depends on what they were designed to be used for as NiCd / NiMh chargers (constant current) or power supplies (constant voltage). Actually on a lead acid battery you want a constant voltage power supply of around 14.4 volts. Once the current falls back indicating a full charge then ideally the chargers voltage should drop below 13.2 volts to maintain a float charge. This is what the "Batery Tender and it's like do. Your power supply doesn't do this but you can use this one sucessfully by charging 12 to 14 hours. Don't leave it connected longer than that because you run the risk of overcharging the battery.

John