Battery Tab Nightmare

Travis wrote to Online Radio Control Car & Truck Mechanic:

"I had read your blog from a post on Facebook and thought i'd give you an email to see if you had some ideas for me. I've been building my own battery packs latly and running into a problem. I have a Brushless Rustler VXL and Ive been having my battery packs fall part after running and bashing in the park. I have re-soldiered the tabs multiple times and they just don't hold. I've used my soldering iron, and even my friends who told me mine may not be hot enough. I went to the hobby store and they sold me solder with flux in it, and it kinda worked but again.... two out of five packs keep falling apart and I re did them all. What is the deal here? What am I doing wrong??"

Travis, AZ.


This one has plagued many people, and it's often due to a missed step. It seems to me that you have done your homework, used higher heat, and even included the much needed flux into the equation. What you may or may have not done is proper preparation. When you solder a battery tab it's a good idea to lightly sand each matching surface, this includes the battery tab (the side facing the top or bottom of battery) and the top and bottom of the battery itself. Having a rougher surface to bond to will make the solder and flux stick a lot better, rather than to a shiny smooth surface. Along with lightly sanding, use a small amount of cleaning alcohol or electric motor cleaner to cleanly wipe the soldering surfaces. Let dry and apply heat, and then add solder. Some people even "tin" (Tin- pre-applying solder to the tab, and then a small amount to the heads of the battery) before you heat and bond the two together.

Try this, and use some patents when waiting for the solder to dry before flexing the pack around. This will reduce the stress on the hot tabs and more likely hold during a rough landing, or other normal rough driving. Another thing is, are you using a battery jig or some king of battery alignment tool? building packs can be tricky to get all the cells lined up the right way and spaced properly. If you aren't using a battery jig, I strongly recommend it. Makes this process faster and easier.

-ORCCTM Tech.

Double Up

Kevin wrote to Online Radio Control Car & Truck Mechanic:

"I want to put two battery packs in my truck to make it go faster. How do I go about wiring it properly. My friend Aaron says it will only make my runtime longer But I wanted it to go faster. What does he mean two batteries will make me have longer run time??
I want to go FASSSST. Wiring HELP!!
-Kevin Ont,Can."

Straight to the point, OK I can deal with that. Kevin... you can actually put two battery packs in your truck one of two ways. Series, and Parallel. Let me show you.
First you should check if your vehicle can even hold two battery packs. Some vehicles are designed with dual batteries in mind, such as an HPI E-Savage or Traxxas' E-Maxx. Other vehicles may be designed around one battery pack, but you can easily find room for a pair of battery packs in a lot of other cars. Since you didn't enclosed what R/C you are running I can't give you more specific info on how to do this (for YOUR truck) but you can use your imagination on where one extra battery would fit in your car. Maybe piggy back onto the other? or on each side of the chassis.
Before you do ANYTHING! Check the Specs for the ESC you are using!!! You'll need to find the manufacturer documentation stating the maximum input voltage that it can handle. For two 7.2v 6-cell packs, you'll need an ESC rated at least 14.4 volts. (wired in series) For two 7.2v 6-cell packs (in Parallel), you'll need at least an input of 7.2V volts. but most sport ESC will have a max of 8.4v. If you run LIPO batteries, I would NOT ADVISE you to run more than one lipo in your car. One lipo is often better and more capable then two NIMH dry cell battery packs no matter the configuration. These methods are typically for non-lipo batteries. Besides, one draw back to these methods are twice the weight in your car. The lipo's are lighter and can offer you simular performance. If you can't afford new lipo's and a charger for yourself, this is always the cheap way to speed and run-time on a budget. But effective. Let's take a look at a diagram to see what all this is talk is about.



* Note: you may have to make a wiring harness to accommodate these type of battery configurations. If you make one of each you always have something on hand to bash around with.
Finally I need to tell you about one more bit of information. Not only does an extra battery make the car heaver and may not always increase performance, but in the "series" setup your run-time will go down faster than the single battery, and the parallel setup will give you a longer run-time than just the one battery. It's the give and take mentality. Hope this helps.

PS. Let me know what car/truck you want to do this in, and I'll be glad to give you some pointers.

-ORCCTM Tech.