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Do It Yourself
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darkmatter said:
Hey Homebrew,

Thanks for the digikey tip, I found it in a previous post but was being a numbnuts about digging through their catalog. I am interested in the fused switch you add. Is this to avoid shorting out your battery or will it possibly throw when your battery is charged and begins to get hot due to increased resistance. It says that it provides noncycling protection but I am not really sure what that is. You seem very knowledgable on the subject; what is your background? I am a High School Physics teacher so I know the electricity stuff but I have limited practical experience.

You have been extremely helpfull on this subject and I would like to extend my gratitude.
The fuse is for overcurrent protection (shorts). The ones I mentioned are specifically designed for rechargeable battery packs and all comercial packs have them. They reset themselves after the overcurrent condition is gone. They don't have anything to do with charging. You could add a thermistor to your pack but your charger would need to be setup for delta T charge termination and then you would need a 3 pin connector. Some chargers like the Maha universal chargers have a thermistor external to the pack to prevent overcharging but mainly use other voltage detection methods for termination.

I spent 6 years as an electronics technician in the Marine Corps. I have since moved on to engineering, although industrial engineering not electrical. Then I spent too much time reading about this stuff on the internet while bored at work. It satisfies my technogeek urges and applies to bikes. What more can one ask for?
 

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COOL BUZZ & TASTY S-TRACK
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Discussion Starter · #42 ·
Power inverter size for charging 2 batteries

Since it seems like your the tech here, I got a question.
I would like to charge batteries from my truck while camping.
What size power inverter would I need to charge two 13.2 (at the most) batteries at once?
 

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R.I.P. DogFriend
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No need for an inverter IMHO

Why bother with an expensive power inverter?

The better battery chargers (not necessarily made for bike lights) run off of 12v anyway.

Here is one that I think might suit you well that runs about the price of an inverter ($65) and runs off of AC or DC and will charge 2 battery packs at once up to 14.4v each. I'm told that the 2500mah limit is not really so, but check it out for yourself.

http://www.hobby-warehouse.com/wapfduacpech.html

There are many others out there. A good hobby store should be able to help you.

Even the Maha can use a cigarette lighter adaptor.
 

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Do It Yourself
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jeffj said:
Why bother with an expensive power inverter?

The better battery chargers (not necessarily made for bike lights) run off of 12v anyway.

Here is one that I think might suit you well that runs about the price of an inverter ($65) and runs off of AC or DC and will charge 2 battery packs at once up to 14.4v each. I'm told that the 2500mah limit is not really so, but check it out for yourself.

http://www.hobby-warehouse.com/wapfduacpech.html

There are many others out there. A good hobby store should be able to help you.

Even the Maha can use a cigarette lighter adaptor.

Inverters don't cost that much especially on eBay (maybe $20). The RC DC chargers are setup to attach directly to a car battery and not the cig lighter through the cars wiring. The Maha may have a cig adapter but it doesn't charge higher voltage batteries with it. The simple voltage regulator it uses only allows you to charge the higher voltage packs with a 18V-22V input. The NiteRider 13.2V Microbrute has a buck-boost switching regulator to allow it to charge higher voltages with the standard 12V input. That's why the 13.2V cost about $20 more than the 6V.

Anyway if you want to go the inverter route, you really don't need anything too powerful even for 2 chargers. Most chargers only draw 1Amp-hour. It's kinda funny that all chargers actually run off DC so you would be converting the DC battery to AC then through a AC to DC wall wort to a DC charger. It's not the most efficient method but might be the simplest.
 

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R.I.P. DogFriend
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I have made a couple of cigarette lighter cords for my chargers so I can charge while driving. I use Deans plugs to connect them to the lighter cord. Make sure that the plug and wiring is designed to handle the amp load regardless of whether you use an inverter or a 12v charger. I have found plugs rated as high as 10 amps with integrated fuses. If you run a 10amp plug at 10 amps, it will get hot and possibly fail. My point being that you should get a plug rated at least 30% higher than the demand you will place on it. I can run two of my chargers at 3 to 3 ½ amps each with the 10a plug and it will only get a little warm at most. If I run them at 8 to 10 amps, they get hot, REAL HOT at 10 amps (don’t do it).

Also make sure that any charger you use is designed to run at 12v and at up to 15v because your car’s alternator will put out up to 14.6v while it’s running and some chargers will not operate at voltages significantly higher than 12.0v.
 

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Pointes on soldering?

Batteries are on order and now I need to get me a soldering iron. I've looked around on ebay. Does it matter what kind of soldering iron I get? The cheap ones are the pencil type with about 30 watts and the more expensive ones are the gun type with trigger feed. What kind of solder should I be using? I got batteries with and without tabs. How do I use the soldering iron? I'm assuming I should practice on something else before trying to solder the batteries together.... Also, how do I attach the wires to the batteries? By soldering as well? If so, do I have to protect or cover the joint between the wire and the tab with something like electrical tape?

Thanks again for the wonderful help!
 

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Do It Yourself
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For soldering directly to cells, you want a higher than standard iron but a gun is not necessary. I have the type that is just the handle with replaceable elements. For this type of work, I use a 45W with a 1/4" chisel tip. You will want to rough up the surface of the cells to get good solder adhesion. It doesn't work very well on the smooth chrome plating. A few strokes on some sandpaper is fine. For solder, any electronics solder will work (I wouldn't recommend plumbing solder). Silver solder will be a bit stronger. Rosin core is easier to use. You might want to get some additional liquid or paste rosin flux. I would stay away from the acid flux (very corrosive) and stick with rosin though.

The key to soldering is good heat transfer. Everything should be clean, keep your tip clean, tin your leads, flux is your friend. Don't hold the iron on the cell too long. If it doesn't melt right away, it's not getting good heat transfer. Clean everything and try again. Good solder joints should be clean and smooth. You might find that you don't have enough hands to do this. I use a vise to hold the cells and forceps to hold the wire so I have my hands free to solder.

Depending on how you arrange your pack, you may or may not need to wrap the cells. You just want to make sure the cells aren't going to touch each other.

You might try to google up on soldering techniques before trying on your cells.

Good luck.
 

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some kind of hero...
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More Info...

Lots of really good info in this thread! A couple of suggestions for stuff I didn't see mentioned:

Protection - if you are making your own battery packs they need physical, electrical and thermal protection. The physical may be tape, heat shrink, waterbottles etc., but you may also find some other products useful. Really thin gasket paper is tough enough to insulate when soldering and prevent shorts. Parchment paper will also work. Electrical protection may be old-style fuses, or the resettable kind. Thermal protection is required to prevent cells from overheating and exploding. Two types of thermal protection are commonly used - one is resettable and the other self-destructs (before your battery does...). The thermal reset and overcurrent protection is available in a single package from various manufacturers, but I like to use the Texas Instrument Klixon type set at 70 deg. If you intend to rapid charge without cell temperature detection make sure you have the thermal protection! They cost about 2 bucks each, and you should order them when you purchase your batteries...

Build on...

:cool:
 

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Will the 2.5mm x 5.5mm plugs work on the old 6v NR lights also?

Homebrew said:
Digikey recently added a good single ended cable to their catalog.

2.5mm x 5.5mm right angle connector with 18 AWG cable part # CP-2200-ND

http://dkc3.digikey.com/PDF/T041/0253.pdf

While you are ordering, you might want to pick up some resettable fuses as well. I would probably use one of these:

part # SRP350-ND or part # SRP420-ND

http://dkc3.digikey.com/PDF/T041/1130.pdf
Will the 2.5mm x 5.5mm plugs work on the old 6v NR lights also?
 

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Yes...

The right angle male connector with twin wires fits perfectly into older NR lightheads, such as the Cyclops, Trail Rat, Digital Pro 6 etc. It would be all you need to wire up to a new homemade battery pack, as it's about 6 feet long.

Since this is bumped up, I'll take the opportunity to say "thanks Homebrew" for that Action Electronics link. They sell the same right angle connector with wires (the wire is 18 gauge; a little fragile, but probably OK), and they also have a few different styles of female connectors that are very handy for homemade setups.
 

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thats my red stapler
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408 Posts
Homebrew said:
The fuse is for overcurrent protection (shorts). The ones I mentioned are specifically designed for rechargeable battery packs and all comercial packs have them. They reset themselves after the overcurrent condition is gone. They don't have anything to do with charging. You could add a thermistor to your pack but your charger would need to be setup for delta T charge termination and then you would need a 3 pin connector. Some chargers like the Maha universal chargers have a thermistor external to the pack to prevent overcharging but mainly use other voltage detection methods for termination.

I spent 6 years as an electronics technician in the Marine Corps. I have since moved on to engineering, although industrial engineering not electrical. Then I spent too much time reading about this stuff on the internet while bored at work. It satisfies my technogeek urges and applies to bikes. What more can one ask for?
where is the overcurrent protection in existing packs? I currently have a nite rider classic that im rebuilding a battery for and was wondering where id find it and if i really need to add it. additionally, when soldering, what is the chance that the batteries can get damaged by overheating them while soldering?
 

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Derailleurless
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The stock fuse...

jimjo said:
where is the overcurrent protection in existing packs? I currently have a nite rider classic that im rebuilding a battery for and was wondering where id find it and if i really need to add it. additionally, when soldering, what is the chance that the batteries can get damaged by overheating them while soldering?
...might look like a flat solder connection between two cells, possibly with some white plastic on it.
 

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Do It Yourself
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There are two common types used, PTC resettable fuses and themostat circuit breakers. Both use different technology. PTC will heat up and increase resistance as current goes up for overcurrent protection then cool down and decrease resistance when the condition goes away. The thermostat senses heat and current and will completely break the circuit if either goes too high. These will also reset themselves.

PTC:


Themostat:
 

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thats my red stapler
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408 Posts
Homebrew said:
There are two common types used, PTC resettable fuses and themostat circuit breakers. Both use different technology. PTC will heat up and increase resistance as current goes up for overcurrent protection then cool down and decrease resistance when the condition goes away. The thermostat senses heat and current and will completely break the circuit if either goes too high. These will also reset themselves.

PTC:


Themostat:
what are those tabs you are using between the batteries??
 

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Do It Yourself
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jimjo said:
what are those tabs you are using between the batteries??
It's a commercial pack with spot welded tabs. These are the same tabs that are optional on cells when you buy them from Battery Station. I prefer to go without tabs and just use desoldering braid to connect adjacent cells. It's flat, comes pretinned and fluxed, and works fine.
 

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rohloff rich
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Homebrew said:
It's a commercial pack with spot welded tabs. These are the same tabs that are optional on cells when you buy them from Battery Station. I prefer to go without tabs and just use desoldering braid to connect adjacent cells. It's flat, comes pretinned and fluxed, and works fine.
Does it matter where the fuse or circuit breaker is placed? It just needs to interrupt the circuit, right?
 

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Do It Yourself
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rs3o said:
Does it matter where the fuse or circuit breaker is placed? It just needs to interrupt the circuit, right?
I'm not sure it matters but these packs have the PTC between the first two cells on the positive side and the thermostat between the last two cells on the negative side. You definitely would NOT want to have these devices in parallel between the same cells though. Other than that, I think it would be okay.
 

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some kind of hero...
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Series Circuit

rs3o said:
Does it matter where the fuse or circuit breaker is placed? It just needs to interrupt the circuit, right?
If the cells are in series and you are using an overcurrent device then you are correct that it doesn't matter where it goes. If you are using a thermal device it must be close or touching the cells to protect from high temperature. Paralleling the batteries requires protection on a 'pack' basis and steering diodes (as a minimum).

I'm looking at the pictures (and I really can't tell for sure), but it looks like the thermal (bullet shaped device) protector looks like a non-resettable one? :confused:

Cheers
 

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Do It Yourself
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airman said:
I'm looking at the pictures (and I really can't tell for sure), but it looks like the thermal (bullet shaped device) protector looks like a non-resettable one? :confused:
Could be but if it's gets to be 90degrees centigrade it doesn't matter much. I would MUCH rather the fuse pop than the cells.
 

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some kind of hero...
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You're absolutely right about the poping cells, but I'm confused why most of the stuff in the thread is focusing on overcurrent protection rather than the combo overcurrent/thermal resettable. I didn't think the PTCs offered decent cell protect for high temperature (75C +)... FWIW anyone using fast charge with the Sanyo cells should be careful about that...

Just comparing notes...

Thanks
 
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