Batteries & Chargers Discuss Li-P, Li-Ion, NiMh, Nicad battery technology and the chargers that juice 'em up!

Need a 12 volt education please.

Old 03-18-2006, 03:50 PM
  #1  
alienx
Super Contributor
Thread Starter
 
alienx's Avatar
 
Join Date: Feb 2006
Location: Secaucus, NJ
Posts: 1,894
Default Need a 12 volt education please.

I have all the parts I think I need to charge my flight battery (lipo w/ Triton charger). I made my own output leads for the charger. My problem is I don't know what to do to use it all.

What I mean is that I figured I could live with using my car battery for a while and forget about buying an AC source for the house. But the input leads on the charger seem way too short to use the battery in the car. I don't think the charger will even reach the ground and there is no way I want to charge a lipo under my hood!

I've seen people in here mention using marine batteries and one person suggested that 2 6 volt golf cart batteries were even better.

Can somebody please help me understand the smartest wat to go about getting a set-up like this? I guess that also means buying some sort of trickle charger for the 12 volt battery. Also, what are the pro's and con's of the different set-ups? Do I need to look out for certain battery or charger specs, or are they all the same?

I know very little about batteries and charging them, so any detail would be a very big help!!

Thanks. Andy
alienx is offline  
Old 03-18-2006, 04:33 PM
  #2  
Red Scholefield
Batteries/Chargers
 
Red Scholefield's Avatar
 
Join Date: Jul 2005
Location: Newberry FL
Posts: 726
Default

Unsolder the aligator clips and add banana plugs (Available at Radio Shack). Then put the aligator clips on some zip cord and cut some pieces of brass tubing the right size to mate with the banana plugs, As I recall it is 5/32 dia, take the banana plugs with you to the hobby shop when you buy the brass tubing. Pick up some red and black heat shrink to put over the 1" pieces of brass tubing after you have soldered it to the other endo of the zip cord, make sure it covers ALL the brass tubing as well as runs onto the zip cord for at least 1/4 inch. Now you can charge your packs from your car battery without leaving them under the hood of your car. I use a cigarette lighter plug to mate up with my charger with enough zip cord to enable charging outside of the car.
Red Scholefield is offline  
Old 03-18-2006, 06:05 PM
  #3  
alienx
Super Contributor
Thread Starter
 
alienx's Avatar
 
Join Date: Feb 2006
Location: Secaucus, NJ
Posts: 1,894
Default

Originally Posted by Red Scholefield View Post
Unsolder the aligator clips and add banana plugs (Available at Radio Shack). Then put the aligator clips on some zip cord and cut some pieces of brass tubing the right size to mate with the banana plugs, As I recall it is 5/32 dia, take the banana plugs with you to the hobby shop when you buy the brass tubing. Pick up some red and black heat shrink to put over the 1" pieces of brass tubing after you have soldered it to the other endo of the zip cord, make sure it covers ALL the brass tubing as well as runs onto the zip cord for at least 1/4 inch. Now you can charge your packs from your car battery without leaving them under the hood of your car. I use a cigarette lighter plug to mate up with my charger with enough zip cord to enable charging outside of the car.
Wow, this sounds great. It would solve a lot of problems. I guess the only thing that has been nagging me in the back of my mind is whether the length of the cords can be a problem. That is, do you need to worry about the length?
alienx is offline  
Old 03-18-2006, 07:07 PM
  #4  
ForestCam
Bad Influence
 
ForestCam's Avatar
 
Join Date: Aug 2005
Location: East Lansing, MI
Posts: 1,120
Default

I'd go with some 18 guage lamp cord form any hardware store. You won't get much voltage drop out of 10'.

Just a note on lamp cord, even though it may be white or brown or black or whatever you can still easily tell which lead is which because one side (neutral for A/C) will have small raised rib on the insulation.
ForestCam is offline  
Old 03-18-2006, 07:27 PM
  #5  
alienx
Super Contributor
Thread Starter
 
alienx's Avatar
 
Join Date: Feb 2006
Location: Secaucus, NJ
Posts: 1,894
Default

Originally Posted by ForestCam View Post
I'd go with some 18 guage lamp cord form any hardware store. You won't get much voltage drop out of 10'.

Just a note on lamp cord, even though it may be white or brown or black or whatever you can still easily tell which lead is which because one side (neutral for A/C) will have small raised rib on the insulation.
Thanks. Is the lead polarity important? I got some 16 gauge black lamp cord this morning, and the pattern on the two halves is different, but I assumed the wire inside the insulation was the same. Obviously I have to maintain the correct polarity between the different components like the battery and the charger, but do I have to worry about which lead I solder to the red or black connector?
alienx is offline  
Old 03-20-2006, 01:26 AM
  #6  
ExtremeRC
Rocket Man
 
ExtremeRC's Avatar
 
Join Date: Feb 2006
Location: Planet EDF!
Posts: 337
Default

I use a 12 volt 7 amp sealed lead acid battery, just like the ones they use in home alarm systems etc. I have one for my flight box for starting gas cars and helis. If I was to go and buy one again I would get the 12 amp version.

I use this to charge all my batteries with the Swallow advance, and use the advance to charge the sealed lead acid battery off the car once its dropped down from charging LiPo's nicads etc.

Its light, easy to transport, and you can charge 1500mah batteries about 7 times, then recharge the 7ah battery on your car, ad infinitum! Getting a 12ah would be even better..

As for wiring up your charger with longer leads, cable gauge depends on current draw, I would use 14 or 16 gauge wire from car to charger, and I would use a deans plug to connect your charger to the new extension wire, just to make sure you dont screw up the connections.
ExtremeRC is offline  
Old 03-20-2006, 04:06 AM
  #7  
ForestCam
Bad Influence
 
ForestCam's Avatar
 
Join Date: Aug 2005
Location: East Lansing, MI
Posts: 1,120
Default

Originally Posted by alienx View Post
Thanks. Is the lead polarity important? I got some 16 gauge black lamp cord this morning, and the pattern on the two halves is different, but I assumed the wire inside the insulation was the same. Obviously I have to maintain the correct polarity between the different components like the battery and the charger, but do I have to worry about which lead I solder to the red or black connector?
Doesn't matter which you use it just matters that both ends are the same, i.e. if you use the ribbed wire for + at one end make sure it's the same at the other.
ForestCam is offline  
Old 03-20-2006, 08:42 AM
  #8  
tim hooper
Single-task man
 
tim hooper's Avatar
 
Join Date: Jul 2005
Location: Telford, UK
Posts: 132
Default

Andy,

A lot will depend on what size of cells you use in your models. A little gel cell might be fine for a park flier, but won't have anywhere near capacity to repeatedly charge cells for a larger model.

You need to work out just how many charges you expect then buy a battery to suit, remembering that chargers in general aren't all that efficient (maybe 50-60%), and go from there.

Ideally a marine or 'leisure' battery is the way to as you can discharge these down to a very low level without causing any damage. The cheapest source for these (in the UK anyway) is a farm suppliers, where they're sold to power electric fences.

A final point to mention is where you carry the battery in your car. Putting a heavy battery at the rear of the car without any form of restraint at all is just asking for trouble in the event of a collision. Either strap it into place, or carry it in the passenger footwell!

tim
tim hooper is offline  
Old 03-20-2006, 05:02 PM
  #9  
falingtrea
Member
 
Join Date: Sep 2005
Location: MN
Posts: 116
Default

Originally Posted by alienx View Post
Thanks. Is the lead polarity important? I got some 16 gauge black lamp cord this morning, and the pattern on the two halves is different, but I assumed the wire inside the insulation was the same. Obviously I have to maintain the correct polarity between the different components like the battery and the charger, but do I have to worry about which lead I solder to the red or black connector?
If you can find some white heat shrink tubing, you could put it on the ends of the wire and then paint or felt tip the heat shrink with black and red. Or even better, if you could find two colors of heat shrink. You can also buy colored banana plugs and jacks from Radio Shack. Polarity is important, so the less margin for error the better.
falingtrea is offline  
Old 03-20-2006, 05:05 PM
  #10  
falingtrea
Member
 
Join Date: Sep 2005
Location: MN
Posts: 116
Default

Originally Posted by Red Scholefield View Post
Unsolder the aligator clips and add banana plugs (Available at Radio Shack). Then put the aligator clips on some zip cord and cut some pieces of brass tubing the right size to mate with the banana plugs, As I recall it is 5/32 dia, take the banana plugs with you to the hobby shop when you buy the brass tubing.
Or, if you are lucky (like me) the alligator clips they used are the proper diameter to directly plug into banana plugs, and you just have to clean the solder off.
falingtrea is offline  
Old 03-20-2006, 08:58 PM
  #11  
alienx
Super Contributor
Thread Starter
 
alienx's Avatar
 
Join Date: Feb 2006
Location: Secaucus, NJ
Posts: 1,894
Default

Man, I keep going back and forth on this in my mind. The charger extension idea seemed so good. But I am worried about running the battery in my car down. If you can drain a deep cycle battery while charging your plane batteries, a car battery would probably not hold up that well. I think I need to get on-line tonight and look for some marine batteries just so I have the facts.

I am planning on charging about 6-7 2200mah lipo's and maybe 3-4 small nimh batteries in a day I guess. Are there any specs i need to look for in a marine battery that would cover these requirements? I guess they are all 12v, but do I need a certain amount of amps or anything? I have no idea what makes one battery more powerful than another in terms of watts and amps and volts go.

Thanks.

PS. I just looked around the web really quickly. It looks like near $300 bucks for a battery and charger. This hobby is ballooning rapidly on me! I see trickle chargers and battery tenders. Is one better? It looks like the tender allows you to always plug the battery in for constant maintenance. This seems like a nice option. I guess I could leave it on my enclosed porch. Are there any toxic byproducts of charging to worry about?

Sorry for all the questions.
alienx is offline  
Old 03-20-2006, 09:07 PM
  #12  
frvrngn
Oops....
 
frvrngn's Avatar
 
Join Date: Aug 2005
Location: Simpsonville, SC
Posts: 550
Default

I have a semi related question since I just jumped on the Lipo bandwagon with the CommonSense deal they are running. I have one of those Home Depot Husky 12V car jump start boxes. I was going to use this for my 12V power source. Will it work OK? My largest pack's are 3s1p2000mah. It looks like it should work fine for both charging at home and at the field. I would rather not spend the money for a dedicated AC/DC power supply.
frvrngn is offline  
Old 03-21-2006, 01:27 AM
  #13  
falingtrea
Member
 
Join Date: Sep 2005
Location: MN
Posts: 116
Default

What's important is the Amp-Hr rating or reserve capacity of the battery. Most auto batteries are listed with cold cranking specs which are pretty useless for our application. But if you can find a reserve capacity or RC rating, that can be used a a good predictor of how much you car battery can charge. The RC is how long a battery will sustain a 25 amp-hr continuous drain until the per cell voltage drops below 1.75 volts. Most auto batteries have at least a 70 minute rating which means most auto batteries can handle 25 amp-hrs of drain and still have a good chance of starting a car. Here are some auto battry specs:

http://www.ibsa.com/www_2001/content...oduct_auto.asp
falingtrea is offline  
Old 03-21-2006, 02:20 AM
  #14  
alienx
Super Contributor
Thread Starter
 
alienx's Avatar
 
Join Date: Feb 2006
Location: Secaucus, NJ
Posts: 1,894
Default

Originally Posted by falingtrea View Post
What's important is the Amp-Hr rating or reserve capacity of the battery. Most auto batteries are listed with cold cranking specs which are pretty useless for our application. But if you can find a reserve capacity or RC rating, that can be used a a good predictor of how much you car battery can charge. The RC is how long a battery will sustain a 25 amp-hr continuous drain until the per cell voltage drops below 1.75 volts. Most auto batteries have at least a 70 minute rating which means most auto batteries can handle 25 amp-hrs of drain and still have a good chance of starting a car. Here are some auto battry specs:

http://www.ibsa.com/www_2001/content...oduct_auto.asp
OK, I've read up a little on this now and I see what you mean about RC. Having never charged a battery for a model (except in my car accessory socket), I don't know how long it takes or at what amp draw that say a TH2100 lipo might charge at. Can you add that info here, so I can try to figure how long a 90RC rated battery might last before it is in need of its own charge again? I am assuming if the amp draw of the lipo and charger was 12.5, then that would double the RC rating of the marine battery right!?

I guess one other thing seems a little unclear. If a 2 volt cell in a battery is only measured down to 1.75 volts (in terms of RC), does that mean it is a "starting" battery and not a deep cycle battery? Intuitively, a deep cycle battery should be able to be drained below 1.75 volts (I would think).

Anyway, I can call one of these battery places and get some suggestions from them, but I could really use some figures on amp draw AND time required to charge a lipo. Then at least I can give them some idea of my drain on the marine battery.

Thanks again.
alienx is offline  
Old 03-21-2006, 03:05 AM
  #15  
falingtrea
Member
 
Join Date: Sep 2005
Location: MN
Posts: 116
Default

Well you could take the 25 amp-hr and divide it by the 1C value of the battery being charged (which is the amp-hr capacity of the battery) to get a rough idea of how many charges you can get. Tha is as long as you are charging packs with a voltage less than 12V.

If you want to be more exhaustive you can do power calculations. Most of the newer battery chargers are more efficient and don't waste as much energy. If you are charging a 6V pack at 1 amp, the 12v input will only draw about 0.5 amp. But if you are charging a 18V pack at 1 amp, the 12V input will draw about 1.5 amps. So you have to calulate power to determine capacity more accurately.

Power is simply volts * amps

So the typical auto battery has about 300 watt-hrs of reserve capacity. A 2S 2000mA Li-Po is about 14 watt-hr, a 12 cell NiMH 2900mA pack is about 43.5 watt-hr. If you assume about 80% efficiency for the charger, then you should be able to charge 17 of the Li-Po packs or 5 of the NiMH packs and still be able to start the car.
falingtrea is offline  
Old 03-21-2006, 03:19 AM
  #16  
alienx
Super Contributor
Thread Starter
 
alienx's Avatar
 
Join Date: Feb 2006
Location: Secaucus, NJ
Posts: 1,894
Default

Thanks Tim. I am going to take this info and call one of the marine suplliers tomorrow and see what they can tell me about the right battery (and charger). Stay tuned!
alienx is offline  
Old 03-21-2006, 03:49 AM
  #17  
Jeremy Z
Wind Warrior
 
Jeremy Z's Avatar
 
Join Date: Oct 2005
Location: Round Lake Beach, IL
Posts: 635
Default

Here's what I'd do, for what it's worth.

Find a discarded computer with power supply. They're everywhere.

Search for threads started by me, and find the one where I asked how to activate an old PC power supply. Just pay attention on the night before garbage day, and I bet you can score an old PC.

When you're in the field, just clip the charger leads as follows. Black goes right to the negative battery terminal. If your car is like mine, it has a rubber boot over the positive terminal. So I open the fuse box and clip to the positive there. There should be room on the air cleaner for both the charger and the battery. No need to make it complicated, IMO. Just leave the hood up.

I have a little 7 Ah gel cell, and they don't last all that long. It's not even really worth lugging around, unless you have to walk quite a ways from your car to where you'll be flying.
Jeremy Z is offline  
Old 03-21-2006, 04:11 AM
  #18  
alienx
Super Contributor
Thread Starter
 
alienx's Avatar
 
Join Date: Feb 2006
Location: Secaucus, NJ
Posts: 1,894
Default

Originally Posted by Jeremy Z View Post
Here's what I'd do, for what it's worth.

Find a discarded computer with power supply. They're everywhere.

Search for threads started by me, and find the one where I asked how to activate an old PC power supply. Just pay attention on the night before garbage day, and I bet you can score an old PC.

When you're in the field, just clip the charger leads as follows. Black goes right to the negative battery terminal. If your car is like mine, it has a rubber boot over the positive terminal. So I open the fuse box and clip to the positive there. There should be room on the air cleaner for both the charger and the battery. No need to make it complicated, IMO. Just leave the hood up.

I have a little 7 Ah gel cell, and they don't last all that long. It's not even really worth lugging around, unless you have to walk quite a ways from your car to where you'll be flying.

Man, after all I've read (and I may be off-base), I am terrified to charge a lipo battery. Especially anywhere near my car. It may be that after a few times you get a little confidence, but right now, I have fear!!

I keep going back and forth on which way I want to go about this. I can either buy or make my own AC source and charge everything before I leave the house (but only one use per battery that way). I can put longer leads on my charger and charge off my car battery. Or I can get some stand-alone set-up. I was all set to do the longer leads thing this weekend but I got tired of trying to solder plugs on batteries and whatnot (needed two more hands!). So I quit for a while. I guess I will have to pick one and live with it until it becomes clear that one way or the other is better.

But thanks for the feedback. This is all shaping my opinion and helping me in a broader sense to get up the learning curve in this hobby!
alienx is offline  
Old 03-22-2006, 05:21 AM
  #19  
falingtrea
Member
 
Join Date: Sep 2005
Location: MN
Posts: 116
Default

Just an FYI, but I found a really cool item at Radio Shack. They have a cigarette lighter plug that has banana jacks on it. So if you have banana plugs on your charger input cable, you can plug right in.
falingtrea is offline  
Old 03-22-2006, 01:11 PM
  #20  
ExtremeRC
Rocket Man
 
ExtremeRC's Avatar
 
Join Date: Feb 2006
Location: Planet EDF!
Posts: 337
Default

I think you are driving yourself to paranoia for no reason, I use my car to charge the LiPo's at home, and everything else including the 7AH gel cell, I use the Gel Cell when I am out in a park/field and dont want to keep lugging stuff back and forth.

I also have a 2500mah car battery charger sitting in the garage and hook the car up regularly and let it slow charge the battery in the evening. This is by far the best way to do it, I sit a workhorse next to the car, sit the Swallow charger on it along with the battery, and connect to the car from there. There is no problem in lengthening your charger leads as long as you maintain cross sectional area of your conductors, IE buy yourself 12 or 14 gauge wire, or just above what is connected to the charger now, strip the ends, remove the clips from your charger and strip to clean copper, twist black to black and red to red, solder the twist, fold it over and heatshrink it! Then reattach the clips to the new cable ends observing the same polarity, and you're done!

Be cautious, check your setting EVERY time you charge ANY battery, and you should have no problems.
ExtremeRC is offline  
Old 03-22-2006, 02:34 PM
  #21  
alienx
Super Contributor
Thread Starter
 
alienx's Avatar
 
Join Date: Feb 2006
Location: Secaucus, NJ
Posts: 1,894
Default

Originally Posted by mocca View Post
I think you are driving yourself to paranoia for no reason.
I think you may be right. I hope anyway! I guess you just have to do it a few times to get some confidence. I've left my transmitter battery on charge overnight and the small nimh batteries for my parkflyer I charge in my car unattended. They are never even warm when I get back to the car to switch packs out.

This is all good advice for a noob like me though, so thanks for the opinion!
alienx is offline  
Old 03-22-2006, 06:24 PM
  #22  
gdhampton
Member
 
Join Date: Jan 2006
Location: Bishop, CA
Posts: 263
Default

frvrngn,

The instructions that came with my Triton say specifically not to use one of the jump start packs with your Li-Po charger. Did not research it enough to know why.
gdhampton is offline  
Old 03-22-2006, 06:46 PM
  #23  
frvrngn
Oops....
 
frvrngn's Avatar
 
Join Date: Aug 2005
Location: Simpsonville, SC
Posts: 550
Default

Originally Posted by gdhampton View Post
frvrngn,

The instructions that came with my Triton say specifically not to use one of the jump start packs with your Li-Po charger. Did not research it enough to know why.
Hmmm... I did a search in this forum after I posted and found that Red (who I consider a battery Guru) uses the exact same Husky pack that I have. He modded it by taking off the cables and adding banana plugs to the top, but thats it. Also saw that Deb Hicks uses them for charging at the field. I guess I can pm them and see whats up...
frvrngn is offline  
Old 03-22-2006, 07:50 PM
  #24  
gdhampton
Member
 
Join Date: Jan 2006
Location: Bishop, CA
Posts: 263
Default

Maybe the reference was to using the pack while it was plugged into AC? Basically, using it like a power supply. Not sure. It would be nice if it would work. Having one in the car is a great idea anyway.
gdhampton is offline  
Old 03-23-2006, 03:09 PM
  #25  
frvrngn
Oops....
 
frvrngn's Avatar
 
Join Date: Aug 2005
Location: Simpsonville, SC
Posts: 550
Default

I hope Red doesnt mind, but he gave me my answer. If anyone else is interested, I think this Husky pack is going to make a great, self contained power supply that is easily portable! When I bought mine, they were $39 or something. Not bad since a 17Ah Gel cell normally costs more than that!

From Red -
"The unit you have contains a 17 Ah sealed lead acid (gel cell) battery. There is no reason that it can't be used on any charger you want. I use it on all of mine.

The Triton statment was refering to automotive battery chargers used as a power source. You cant use them because they have no filtering and the raw rectified AC screws up the charger."
frvrngn is offline  

Quick Reply: Need a 12 volt education please.


Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.

Page generated in 0.17569 seconds with 12 queries