# Multiple batteries in parallel



## Michael Glavin (Jan 2, 2009)

Multiple batterie packs wired in parallel to increase amp hour capacity?

Diodes were mentioned in another thread to prevent cross charging of batteries connected in parallel. 

Please share how you’re batteries are wired, charged and if their interconnected 24/7 or disconnected while charging or after use or what?

Thanks,
Michael


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## Greg Elmassian (Jan 3, 2008)

if you put one diode on the plus lead of each pack when running, that will do what you want. 

When charging, you will have to use a connection that does not go backwards through the diode. Of course, most packs need separate chargers... 

Regards, Greg


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## TonyWalsham (Jan 2, 2008)

Here is how I did it.










The pcb with the parts diodes etc was in the fuel tank of an SD-40. The two charge jacks were mounted one on each side in the holes where the fuel filler caps were.


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## Stan Cedarleaf (Jan 2, 2008)

Michael.. Here's a very simple diagram using individual A 3 amp diode. Or as Tony suggested, A 6 amp diode

The second image a battery setup for 2-21 volt Li-ion batteries using a DUAL-SCHOTTKY-RECTIFIER-25A-45V Diode. It's a bit more complex but works right nicely and was used for quick change batteries mounted in an LGB Box car. The batteries were changed through the door.


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## Greg Elmassian (Jan 3, 2008)

Tony, if I understand your circuit right, you have the ability to disconnect the common grounds when charging the batteries, and then reconnect when running. Do you do this through a special plug in the charge jack, or your charge jacks have the "Switch" to make/break the ground connections? 

Regards, Greg


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## Michael Glavin (Jan 2, 2009)

Greg, Tong and Stan, 

Thanks for the info; I completely understand the rudimentary method of sizing and wiring diodes into play... I’m interested in field practice and how modelers are actually executing the aforementioned deeds... 

I suppose my curiosity is in play as I alluded to previously in another thread I have done extensive testing with regard to cross charging flight packs specifically for RC aircraft. I found while it was a reality it simply was not a consideration for this application. I used many scenarios together with multiple lab quality DMM's, multiple battery chemistries and electronic loads and so fourth and realized it required notable voltage differences to effect cross charge and when you mixed in current consumption simultaneously it again wasn’t a concern (the actual numbers evade me at this time but they were insignificant). Aircraft represent a different set of typical operating parameters, batteries are only armed when the model is in flight, resting batteries are completely independent of one another, batteries are load tested before and after each flight, multiple fifteen minute flights are atypical and some use voltage regulators or sophisticated electronic power distribution boards which use multiple Schottky diodes. 

Trains are a different animal, simple diodes make sense as failure modes and electrical losses are not such a keen concern. However operational practice or system design seems key to mitigate the need for protection from cross charging, shorts and the like. 

I like Tony’s battery board it simplifies things to some extent. I’m going to build a battery trail car soon and am looking for a pre-fab board which provides all the goodies mounted to include provisions for multiple batteries (might have to make my own or combine goodies). Tony I looked at your site you offer some nice gadgets… 

Regards, 
Michael


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## Stan Cedarleaf (Jan 2, 2008)

Wonderful, Michael. Sounds like you have a good handle on the situation already. Yes, the aircraft and railroad applications are quite different. 

I'm still using 2 - 12 volt 4.5 amp hour gel cells in series to 24 volts to running my larger diesels. They're inexpensive and have been running for me for up to 8 years.  

I've added Li-ions to power the smaller single and dual motor locomotives with very good results. Haven't ventured into the Poly's yet..


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## Bill Swindell (Jan 2, 2008)

I have used diodes to parallel battery packs on several locomotives. It works great.


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## kcndrr (Jan 7, 2008)

My simple diode setup does not attach to the Li-Ion battery but an addional connector, the diode connector is to the power feed. I use a terminal strip that I have CON-240 connectors attached to, with the diode in each set of these connectors, I then attach the output end of the batteries to each of the connectors to the terminal strip. The terminal strip collects all the power inputs as parallel setup and sends power to receiver. That way the batteries can just be unplugged and charged at any time. I also have the terminal strips setup for 4 individual battery inputs if I want that amount of power, one to four batteries and all I need to do is plug battery in. for this setup I just use the Aristo Li-Ion batteries or my AA battery packs. I don’t mix batteries.
Now 4 Aristo li-ion battery packs or 32 AA batteries take up room, so this setup is only used in trailcar setups.
KC


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## TonyWalsham (Jan 2, 2008)

Greg. 
I use 2.5 x 5 mm DC co-ax jacks. These are actually SPDT switches. Positive is to the pin. When you insert the charger plug it automatically switchs out the ground circuit. 

I use the same jacks, wired slightly differently, for the BIK-U3/6 install kits. They permit the same loco mounted jack to be used for charging, or as a port for an auxilliary battery source in say, a trail car. They do of course carry the full load current, but they are rated up to 5 amps. 

They can be used with any brand of Radio.


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## Greg Elmassian (Jan 3, 2008)

This is very cool Tony, looks like a perfect solution that helps neophytes (and experienced people alike) protect themselves from all the common mistakes, making a foolproof solution. 

Is there a part number for all the parts shown, so I could list the "kit" on my site and pictures (with your permission of course). 

This subject comes up all the time with the same questions, and people often go from step 1 (no diodes) to step 2 (diodes) to step 3 (more circuitry to be able to charge now the diodes are blocking the charge!). 

Regards, Greg


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## TonyWalsham (Jan 2, 2008)

Greg I don't make that double jack circuit as a kit. 
I envisaged them for big locos and did a few prototype pcb's, but, there was absolutely no interest in them. 
I really don't like them anyway as the protection diodes drop the useable voltage going to the on board controller. 

I believe that up to 5 amps the BIK-U kits are a better way of going about it. 











How to wire a BIK-U3/6 kit:

http://www.rcs-rc.com/PDF/Accessories/Instructions/Install_kits/BIK_U3_6v2.pdf

This is how to wire it if you want to save the cost of the kit.


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## Paul Norton (Jan 8, 2008)

We use a standard, four-pole double-throw, center-off, toggle switch (All Electronics part # STS-71) in our Evans power cars. A standard switch can handle the power of two lithium-ion battery packs in parallel.

 

Soldering loop terminals to the component wires made connecting them to the screw terminals on the switch easy. To make the wiring easier to understand, the 12 terminals were divided into three columns: the left for the battery pack charging plugs, the center for the battery packs, and the right for the TE receiver.

 

The battery charging plugs (All Electronics part # CON-240) mate with the Aristo-Craft, lithium-ion battery chargers. They were mounted on the bottom of the car next to the switch.

 

The loop connectors soldered to the plugs were fastened under the left column of screw terminals.

 
The loop connectors soldered to the Aristo-Craft, lithium-ion battery packs were fastened under the center column of screw terminals.

 
Loop connectors were soldered to the positive side (anodes) of two, 3 amp, 40 volt, Schottky diodes (All Electronics part # 1N5822S).

 

The diodes were fastened to under the two positive terminals in the right column of the switch. The positive input wire of the Aristo-Craft, 27 MHz receiver was soldered to the negative side (cathodes) of the diodes.

 
A jumper was made to connect the negative input wire of the receiver to the remaining negative terminals in the right column of the switch.

 
When the switch is toggled one way, the battery packs are connected in parallel through the diodes and the jumper to the receiver.

 

When the switch is toggled the other way the receiver is disconnected, and the battery chargers connected to the battery packs.

 
Our club members use these power cars to run large six-axle diesels and double-headers using an MU plug (All Electronics part # CON-240) that mates with the MU plugs on Aristo-Craft diesels.

 

There is an article on our club web site that details the construction of this Evans Power Car.


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## Paul Norton (Jan 8, 2008)

The wire colours from the center of the car should be red, black, red, black.


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## Michael Glavin (Jan 2, 2009)

Great information gentlemen. Thanks for sharing. 

Michael


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## kcndrr (Jan 7, 2008)

And for those of you who have no clue this is what I do. I do not charge my battereies in the railcar or loco. Too much wasted time for loco sitting waiting to be charged. This setup, well actually up to 4 ot them attached to a terminal strip for loco power makes it simple, plug in or unplug. Use as many batteries as will fit. You can see diode at end of black wire. 










Just put diode in con-240 connection to terminal strip. Then plug battery into this connection. Wah-la, done, power and diode protection and no complicated wiring circuts.

KC


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