Best Way to charge gel 7a 12v on way to field?

Best Way to charge gel 7a 12v on way to field?
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Best Way to charge gel 7a 12v on way to field? - 10/5/2005 2:07:57 PM

speedster 1919

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From: Martinsville, IN, USA
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I have a van and keep my planes and field equipment in it all the time. My flying time is not planned most of the time since I'm on the road as a salesman. If I decide to fly ,I want to use my rear lighter outlet to charge my 12v gel battery on way to the field ,about an hour. If I just put a cig lighter plug with alligator clips ,will my car charge the battery safely while I drive or would it be better to get an 110v inverter and plug in my wall wart charger for the 1 hour I drive. The car charge rate could be potentionally be 40 amps and I don't want to gas or overcharge my gel battery inside my field box.

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RE: Best Way to charge gel 7a 12v on way to field? - 10/5/2005 2:26:12 PM

Mad Wax

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If you plug the cig. lighter straight into your acid battery it'll damage the battery, if not explode or split. You need to regulate the charge output. Some van/truck outputs are 24v also. To fully charge that battery (from flat) in one hour approx 7A charge which is very high also for all battery types. Probably best to use a slower charge but start the charge before you leave, or perhaps the night before (if it's a NIMH 1A charge with delta peak shut off before you go to bed and it'll be done by next morning)

If it's a lead acid battery they don't take kindly to fast charges, so I would possbily use a slow charge once it's topped up it continues with a very slow trickle charge (can be left trickling 24/7) however it'll probably eventually flatten the van battery

(in reply to speedster 1919)

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RE: Best Way to charge gel 7a 12v on way to field? - 10/5/2005 2:42:09 PM

speedster 1919

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From: Martinsville, IN, USA
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Thanks for the reply. I know the rear plug is not 24v and the gel battery will not be fully discharged. I basicly want to top up the charge as I drive to the field. The charge wall wart is about 1/2 amp and will do this safely , maybe pluged into an 110v inverter with lighter plug for cars. I think !!!!!

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Hey Buddy -That was the most spectacular crash I've ever seen , That rolling cart wheel with parts slinging out was cool...

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RE: Best Way to charge gel 7a 12v on way to field? - 10/5/2005 4:38:38 PM

JNorton

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From: Montague, MI, USA
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Mad Wax,

quote:

If you plug the cig. lighter straight into your acid battery it'll damage the battery, if not explode or split.

If the gell cell is charged there is no problem. Put a 1 amp fuse in series with the cig. lighter for protection and you are good to go. this is exactly how I keep my field battery charged.

John

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RE: Best Way to charge gel 7a 12v on way to field? - 10/7/2005 6:32:05 AM

AS-EE

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From: Greenville, SC, USA
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Please remember people to include a fuse as Jnorton has stated above because if your gell cell battery has less voltage than what is being supplied at the cigeratte lighter socket then you will have huge current flowing through the wires to the small gell cell battery. It is safe, however to hook up a Gell cell battery if it is charged because it will have the same voltage potential as that being supplied by the cigeratte lighter socket and thus there will be a net voltage drop across the wire's resistance of zero and therefore 0 amps of current flow.

(in reply to JNorton)

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RE: Best Way to charge gel 7a 12v on way to field? - 10/7/2005 12:59:08 PM

speedster 1919

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From: Martinsville, IN, USA
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That way still sounds iffy.........So to play it safe I went to Harbor Freight and bought a 110v converter and pluged in my Hangar 9 wall field battery charger. Seams to work OK. The inverter is suppose to shut off if car batt gets to low. Funny but my cig plugs only works when van is running......... Also I checked the price of the inverter off the net from Harbor Frieght and it was $19.95 at the store it was $29.95. I asked why the big difference in price and was told I was paying for the store front. But I could go home order and pay the frieght for $19.95.

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Hey Buddy -That was the most spectacular crash I've ever seen , That rolling cart wheel with parts slinging out was cool...

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RE: Best Way to charge gel 7a 12v on way to field? - 10/7/2005 1:43:54 PM

BillS

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From: Greensboro, NC, USA
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quote:

Also I checked the price of the inverter off the net from Harbor Frieght and it was $19.95 at the store it was $29.95. I asked why the big difference in price and was told I was paying for the store front. But I could go home order and pay the frieght for $19.95.

Carry the printed copy of the web page and they will sell it to you for the same price. Always check the web. Harbor Freight bears watching.

Bill

(in reply to speedster 1919)

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RE: Best Way to charge gel 7a 12v on way to field? - 10/7/2005 4:44:36 PM

JNorton

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From: Montague, MI, USA
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quote:

ORIGINAL: speedster 1919

That way still sounds iffy.........So to play it safe I went to Harbor Freight and bought a 110v converter and pluged in my Hangar 9 wall field battery charger. Seams to work OK. The inverter is suppose to shut off if car batt gets to low. Funny but my cig plugs only works when van is running......... Also I checked the price of the inverter off the net from Harbor Frieght and it was $19.95 at the store it was $29.95. I asked why the big difference in price and was told I was paying for the store front. But I could go home order and pay the frieght for $19.95.

So you take 13.8 volts DC from the automotive system convert it to 120 VAC and then convert it back down to 13.8 volts VDC.

Sometimes it helps to think about what you are doing. Again I say the field box battery doesn't know where it getting its voltage from and doesn't care.

John

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RE: Best Way to charge gel 7a 12v on way to field? - 10/8/2005 2:32:01 PM

speedster 1919

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From: Martinsville, IN, USA
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Hi John I know that sounds whacked to convert back to 13.8 volts but on some vehicles it could be 14.2 - 14.5 The vehicle battery being larger will set the initial charge rate of probably 15 amps to replace starter usage . I was not sure the 7 amp gel cell was smart enough to take just the 1/2 amp it would need. The 1 amp fuse in line with a cig plug sounds safe , but I wanted a inverter anyway...............Right now I know I am safe with the Hanger 9 12v charger. My tower .75 needs all the juice for the sullivan starter it can spare. That is a tight ABC engine.

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Hey Buddy -That was the most spectacular crash I've ever seen , That rolling cart wheel with parts slinging out was cool...

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RE: Best Way to charge gel 7a 12v on way to field? - 10/9/2005 1:42:08 PM

JNorton

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From: Montague, MI, USA
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Now I understand!

quote:

The vehicle battery being larger will set the initial charge rate of probably 15 amps to replace starter usage . I was not sure the 7 amp gel cell was smart enough to take just the 1/2 amp it would need.

Current will split between the two batteries depending upon their state of charge. If the gell cell is charged it will draw a minimal amount of current even though the alternator is supplying 30 amps to charge the car battery. Exactly like AS-EE posted.

John

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RE: Best Way to charge gel 7a 12v on way to field? - 10/9/2005 2:35:55 PM

JimTrainor

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From: Ontario, ON, CANADA
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The only problem I see with the fused direct connect is that if the 7 Ah gell cell is significantly discharged it might draw more than one Amp and then the fuse will blow. Then you'll be left with an uncharged battery... which would defeat the whole purpose.

You could discharge your battery then measure the max current when you connect it. Even with a measurement to see what's happening, I think I'd just hook up the battery and fuse and see what happens. The fuse will protect the battery (and car). If you find it never blows, then I'd say your fine. You might want to carry a spare fuse with you figure this out.

If somebody knows the internal resistance of a 12 7Ah gel cell we could figure out the answer.

(in reply to JNorton)

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RE: Best Way to charge gel 7a 12v on way to field? - 10/9/2005 3:18:41 PM

JimTrainor

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I just measued by own 7 Ah gel cell. This is what I measured using a Hanger 9 charger (nominally 12V/600mA):

battery voltage no load: 13.4 V (it is fully charged)
charge voltage when the Hanger 9 charger is attached: 15.2 V
charge current: 300 mA

(p.s those number don't make complete sense to me...they say that batteries internal resistance is 6 ohms. higher than I would have guessed?)

So... If I connected this to 13.8 volts the current would be lower.

Repeating the excercise with a discharged battery would be more informative. (But I don't have any easy way to discharge my battery at the moment.).

If you do try the direct connect to your car, and the fuse blows, a resistor in series would limit the current. But if you're uncomfortable with it, don't sweat it. Just get the inverter.

(in reply to JimTrainor)

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RE: Best Way to charge gel 7a 12v on way to field? - 10/10/2005 12:25:26 AM

AS-EE

Posts: 191
Joined: 8/25/2005
From: Greenville, SC, USA
Status: offline

quote:

I just measued by own 7 Ah gel cell. This is what I measured using a Hanger 9 charger (nominally 12V/600mA):

battery voltage no load: 13.4 V (it is fully charged)
charge voltage when the Hanger 9 charger is attached: 15.2 V
charge current: 300 mA

(p.s those number don't make complete sense to me...they say that batteries internal resistance is 6 ohms. higher than I would have guessed?)

So... If I connected this to 13.8 volts the current would be lower.

Repeating the excercise with a discharged battery would be more informative. (But I don't have any easy way to discharge my battery at the moment.).

If you do try the direct connect to your car, and the fuse blows, a resistor in series would limit the current. But if you're uncomfortable with it, don't sweat it. Just get the inverter.

A battery at a voltage potential of zero is practically a dead short circuit and tons of current will flow through it. I hope you realize that the power produced will be substantial and the battery will get hot instantly and could lead to serious injuries. So even if you had a 13.4 charge voltage you will STILL need a way to limit current. Also it's not very wise to discharge a lead acid battery completely as this will ruin it.

(in reply to JimTrainor)

Post #: 13