please entertain more novice battery questions

[FJ and G]

I wish to combine several batteries (AA) for a critter. Should I run them in series or parallel?

Which way increases voltage?

 

Which way increases mAh?

 

These questions also are IMPORTANT for when I go to connect my battery charger so as not to exceed voltage and to also put the setting on correct mAh. 

 

Last question involves bundling the batteries. To run them in parallel, can I just add a copper strip and the top and one at the bottom (+ and -). And then ducktape the whole thing?

 

thanks 

[heinzm57]

Rechargable batteries have 1.2 V. The mah depends on the indivitual battery. You have to wire them in series.....plus to minus to plus....and so on. I use Sony 2800 mah. You can get them with tabs or cut your own from tin, and solder them to the ends.

Good luck

 

[TonyWalsham]

Rechargable batteries have 1.2 V. The mah depends on the indivitual battery. You have to wire them in series.....plus to minus to plus....and so on. I use Sony 2800 mah. You can get them with tabs or cut your own from tin, and solder them to the ends.

Good luck

 

Heinz.

Under no circumstances should you solder anything directly to the NiCd or NiMh cells.

The sustained heat required will damage the cells internally and shorten their life.
That is why the tabs are spot welded on with cells sold that way.
Spring holders are poor alternative for current draw of any more than 1-2 amps. 
Because the springs rely on a pressure connection to make a circuit, there is some resistance between the cell and the spring that over time will cause the spring connectors to loose tension and make the problem even worse.

Properly constructed battery packs using tabbed cells are the only really reliable way of battery powering.

But then I have only been doing this for 20+ years. Maybe not long enough to know what I am talking about.

[altterrain]

If you are going to make your own pack, I would get the pre tabbed cells. You have to be careful soldering them yourself as the heat can damage the cell. I have never heard anyone hooking up cells in paralell. Batteries in series will increase the voltage (1.2v per cell) You can get tabbed cells and pvc shrink wrap at allbattery.com .

 -Brian

[FJ and G]

thanks; so series is the way to go and while V will increase, mAh will remain the same. So if I'm using three 1.5V batteries, each 300 mAh in series, then once in series, V will equal 4.5 and mAh will still be 300 for the group (same as it was for each individual, assuming they are all same V and same mAh).

[heinzm57]

Tony,

I have soldered tabs on 6 packs now and never ruined a battery yet.

My dear friend: If you get the ones with tabs you still have to solder the tabs. If you were any closer i would give you a lesson in soldering.

But then I have only been doing this for 20+ years. Maybe not long enough to know what I am talking about.....I have been model railroading  since 1961, and let me asure you, i am still learning . Of course, one has to be willing to learn.

Heinz Mayr

[TonyWalsham]

Tony,

I have soldered tabs on 6 packs now and never ruined a battery yet.

My dear friend: If you get the ones with tabs you still have to solder the tabs. If you were any closer i would give you a lesson in soldering.

But then I have only been doing this for 20+ years. Maybe not long enough to know what I am talking about.....I have been model railroading  since 1961, and let me asure you, i am still learning . Of course, one has to be willing to learn.

Heinz Mayr

Heinz.

The advice from the battery manufacturers themselves is NOT to solder directly to the battery cells.  You must only ever use tabbed cells for the reasons I have previously stated.
Sure the cells will keep functioning but believe me they will be damaged internally such that the operational life, in terms of the number of re-charges, will be severely reduced.
The tabs are long enough so that the heat generated during soldering does not have time to get into the cell and damage it.

I produced the first "Glitch Free" battery R/C system for Large Scale locos in 1987. 
If you don't want to take my advice that is up to you.
I am only giving it from experience gained since then. 

BTW I have been model RR'ing since 1950 when my dad first introduced me to Hornby 00.

 

[heinzm57]

Re.: Tony

Well ,well, well......i did not know that my batteries are all damaged since i soldered tabs on them. Maybe i invented something new her.....my engines are running on thin air.

[TonyWalsham]

Re.: Tony

Well ,well, well......i did not know that my batteries are all damaged since i soldered tabs on them. Maybe i invented something new her.....my engines are running on thin air.

Heinz,
If you had read what I actually wrote you find I said they would still function. 
But the life span would be reduced.

If you wish to twist what I say merely to continue sniping at me feel free.

[altterrain]

thanks; so series is the way to go and while V will increase, mAh will remain the same. So if I'm using three 1.5V batteries, each 300 mAh in series, then once in series, V will equal 4.5 and mAh will still be 300 for the group (same as it was for each individual, assuming they are all same V and same mAh).

Only 300 mAh!

I don't even bother with batteries less than 2000 mAh. You'll find your run times with 300 mAh rather brief. Batteries of that capacity are designed for low draw applications like cordless phones not heavy metal japanese critters! My first pack was 1500 mAh and I found it rather unsatisfactory.

-Brian 

[mickeyls]

I am a little confused with the messages between Tony & Henzm57.   Are you talking about making your own tabs or using the one that already come with tabs ??? 

 

[FJ and G]

thanks, Brian, just using 300 as example. So I guess it will stay the same mAh regardless of # of batteries hooked up in series; only the V increases

 

Mick

 

making your own tabs. I think they are both correct (from what I could find in researching this) as it can be soldered but the heat has to be rapid or it will damage the cell
 

[TonyWalsham]

I am a little confused with the messages between Tony & Henzm57.   Are you talking about making your own tabs or using the one that already come with tabs ??? 

 

Henzm57 is saying it is OK to solder directly to the case of the cells. 
I am saying, according to the manufacturers of the cells, it is most certainly NOT ok to solder to the cases of the cells. 
It takes a relatively long time, compared to soldering to a tab, to bring the case up to a temperature hot enough to melt the solder properly.  This heat build up will damage the cells internally and reduce the life span in terms of how many recharges the cell(s) can accomplish.

There is no problem soldering to tabbed cells.  That is why they are made.

[piercedan]

You can cheat and get away with it for awhile.  I believe Tony and that the heat destroys the cells lifetime.  Most people that solder apply way too much heat and even with tabs, you should only solder the end far from the battery, keeping heat from the cell itself!!

 Note that batteries are checmical reaction devices and heat can cause explosions!!!  Check out the news about laptop batteries that have been recalled in the past year.

[hoofe116]

FJ:

Something you might want to keep in the back of your mind, before you string together a number of low-voltage batteries to get the voltage you want, is that the little critters have a nasty habit of dying a slow death. In the meantime, they can act like resistors and impede current flow from 'good' ones behind in the string. Or they won't take a full charge.

Someone more informed about train-specific batteries will have to carry on from here, but when I get to that point, I'll try to use the smallest number of batteries in series to get the voltage I want, or I'll use a semiconductor circuit as a voltage control to lower the voltage of a larger battery. That whole subject is an unknown to me.

You need to know the total current draw of your motor under load and any lights or control boards you are powering from the same set of batteries. That'll tell you what milliamp hour battery(s) you'll need.

A 'milliamp' is 0.001 amp or 1/1,000 of an amp. It used to be that car batteries were rated in 'amp hours', or the number of hours a battery would produce a given level of current. (Amps= current). I dunno how they do it these days, probably as misleadingly as possible. You will see that the heavier the current draw, the faster the battery discharges, and that the rate isn't linear. Thus, you want a reserve current capacity, i.e. something higher than what your total draw would be. Prob'ly no one runs their engine motors at full bore for very long, so it's not very critical, but if you do need a burst of speed, there should be enough battery capacity to provide it.

I have no experience with re-charging a string of series-connected (plus to minus to plus to minus) but I'd be a little wary of the ones in the middle of the string getting their fair share, so to speak.

But again, all my experience has been real-world, as opposed to hobby world. It sound like Allterrain has some good insights, I wish he'd weigh back in and comments just in case I've managed to confuse you. Or worry you. It ain't rocket surgury.

Les W.

[hoofe116]

I would not solder directly to a modern, small battery case, t'were it me. Just my worth. As for spring contacts being unsuitable for high current draw, I suspect that's correct. Use flat strips of contact brass, a special alloy used for heavy-duty apps. If you can still get it. Might look at tearing up some circuit breakers for the material in their contacts. There's high current material for you.

Les W.

[grandpopswalt]

Tony,

Thanks for the input. I've always known that heat, weather internally or externally generated,  is a battery's worst enemy. But I wasn't aware that the brief but intense heat applied to a battery while soldering was so detrimental to it's life cycle. Are there any statistics that you know of that predict just how badly a cell is compromised when soldered?

Now what the h_ _ _  am I going to do with the 50 3200mah NiMH non-tabbed cells I've got squirrled away.

Walt 

[TonyWalsham]

Walt.

My comments are based on my own experiences and the recommended practices for using batteries as described in the Sanyo battery service manuals.

Take your non tabbed cells to a battery specialist place and ask them to spot weld tabs on the each end of each cell.

[EMPIRE II LINE]

Personal input..... 

Just a thought, as to the fear of even overheating the tabbed batteries, couldn't you use a heat sink clip or something connected to the tab to dissipate the heat, hooked to the tabs between the solder point and the end of the battery, as you solder them ???? Or would that really even be a problem on the tabbed batteries ?

Byron

[hoofe116]

Personal input..... 

Just a thought, as to the fear of even overheating the tabbed batteries, couldn't you use a heat sink clip or something connected to the tab to dissipate the heat, hooked to the tabs between the solder point and the end of the battery, as you solder them ???? Or would that really even be a problem on the tabbed batteries ?

Byron

That would mostly depend on how good one is at soldering. As someone has already said, most people use too much heat. Or they try to solder with a dirty, untinned tip, don't use flux, etc, etc.

For most purposes a clip-on heatsink is good enough. For the truly paranoid, solder two suitably-dimensioned blocks of copper inside the jaws of a common alligator clip. This will make a very suitable heat sink for pennies. I imagine you could even bend two lengths of 12 ga solid bare copper wire back on themselves and solder one each to the upper and lower jaws of said clip. That'll give you plenty of heatsink (thermal absorption) capacity--unless you're using a 100 watt iron with a large tip.

Les W.

[castlebravo]

If you really want to learn about batteries go to a RC heli forum. As an RC heli pilot myself these guys know there stuff about batteries. In a gas heli a battery failure can send your bird flying who knows where. A 90 size heli with carbon blades could take an arm off or kill someone. These guys know there stuff. The short of this is yes, you can solder your own batteries but you better *** well know what you are doing and know how to test your pack after you are done. Knowing how to check the condition of your pack is a must for a heli. I like the guys at runryder.com  They can provide plenty of links on battery FAQ's

[Great Western]

The comment about rc aircraft by Caslebravo reminded me of a video I recently saw on one of the Intenet video systems.  The video showed a large model aircraft, around 8ft. or so fuselage length.

It crossed my mind, when watching the operator using his remote control system, what would happen if the aircraft lost signal and went beyond the range of its remote control.  With model controlled railroads there is no probelm usually in this area as the train is confined to the track.  The worst that can happen, I guess, is a derailment or wreck. 

[FJ and G]

Castle:

 

This the forum?

http://www.rchelimag.com/forum/ 

 

 On a link from one of the forum posts, I found this expensive battery:

http://www.centuryheli.com/products/productdetail.htm?currentid=441&prtnm=CNE5515

 

 

[FJ and G]

Soldering batteries from that site:

 

http://www.rchelimag.com/pages/howto.php?howto=20&page=1

 

[grandpopswalt]

I've done a lot of reading about this subject since this thread started. I am surprised by just how sensitive these batteries are to heat. Apparently the heat from soldering can damage the very thin plastic films inside as well as the seals that vent the cell. As Tony Walsham pointed out early in the thread, don't solder these batteries unless you really know what you're doing.

However, I've read about one modeler's technique that sounds plausible. He removes the tip from a 140 watt soldering gun and inserts two pointed heavy gauge copper wires into the gun. He puts a tin soldering tab on the battery surface and pushes it down hard with the copper wires and then pulls the trigger. The gun's output is about 1.5 volts but at 140 amps. That is enough to actually weld the tab to the cell. Supposedly this generates only very localized heat that does not get into the guts of the cell. I'm going to try this one of these days to see if it really works. If it does, this would be a really nifty, low cost spot welder.   

Walt