You want your RC-car to be faster than the ones of your buddies? You want to drive longer? Want to accelerate faster? Then read on and be assured that our Beginners Guide to LiPo is your secret ticket to go faster than your racing buddies!
LiPo mysteries
You heard of the mysterious LiPo batteries? Heard that they make your ride go faster for a longer period of time compared to those nasty NiMH batteries that came with your latest RTR buggy or car? We are not going to bore you with the technology behind Lithium Polymer cells (tech nerds might be interested in this Link) but get straight in to the action and show you what to do to get a speed advantage with LiPo cells.
Do they fit?
First and foremost: LiPo battery packs are not a direct replacement for NiMH or the older NiCd packs although most manufactuers claim they are. Thanks to the dimensions used to create LiPo packs they most likely fit your car, truck or buggy but not your charger, the charging methods used and of course not the overall safety precautions! But let's do it step-by-step.
Picking the correct pack
Choosing the correct battery pack is as easy as 1-2-3. Most of the current LiPo battery packs of the countless manufacturers sport common dimensions meaning you can easily replace that gnarly NiMH pack with a super-duper LiPo battery. Many model manufacturers offer their own line of hop-up packs to switch from NiMH to LiPo with no problems. Often, when you look closely they offer some sort of 'hop-up' sections where they promote their products on their websites. Just have a look first and see what the model manufacturer has to offer. Most of the time you find optional battery packs very easy and you are also ensured that the pack(s) you buy fit your models chassis just right.
If you are not happy with what you found or the factory options do not fit your budget, have a look around the internet at the various aftermarket battery companies. Here you can find a vast amount of optional battery packs in every size, configuration and price range. When buying aftermarket packs make sure they fit your car! When you are looking for an optional pack for your RTR model, chances are that only LiPo batteries that resemble 'Racing packs' may fit. The so called Racing packs consist of two 'in-line' soldered stings of Sub-C-sized NiMH or NiCd cells. They are of an oval profile and often this is needed to suit the model's chassis or battery compartment. If your model sports such an oval shaped battery compartment you can either try to modify the chassis of your car or use Racing pack style packs like the LiPo Rocket Packs from Team Orion for example.
The next tricky part in choosing the correct pack are the overall dimensions of the battery. If the battery you want to replace is of the usual 7.2V Sub-C style than the alternatives are quite clear. You need a pack not longer as 140 mm, not wider as 46 mm and not thicker as 24 mm. These standard dimensions are featured by most battery packs and make swapping easy. If you need special batteries, for example for smaller 1/16 or 1/18 scale models than 85 x 29 x 17 mm are the numbers you need to take care of. But remember: what we tell here is just a rough guide line! Always double check with the actual batteries you use to make sure to order the correct items.
If you look for a battery pack to suit your monster or Short Course truck or even the new generation of 1/8 scale electric off-road buggies the choice is quite easy as these often have rectangular battery compartments. Just measure what the maximum dimensions of the battery compartment are (length/width/height) and have a go on whatever product suits your needs. When it comes to battery packs for the above models many manufacturers offer special solutions for trucks like the Traxxas E-Revo, Mini Revo etc. Again, just have a look around the specific websites and most of the time you will find what suits your needs.
Hard or soft?
Normally LiPo batteries come in two different forms: as soldered packs wrapped in shrink wrap or as so called hardcase packs that feature an outer plastic box to protect the cells.
If you just bash or race non-sanctioned races softcase (shrink-wrapped) packs are ok as long as you make sure that there is no possibility to damage them during use. Damage can be done by rocks, stones, wood and basically everything that you can find off-road. In this case hardcase packs are the way to go. When your model is equipped with an enclosed battery compartment shrink-wrapped are ok too.
What else?
Given you found the correct battery pack to suit your needs, make sure the speed controller of your model is 'LiPo-ready'. As It is fundamental for safety and durability of every LiPo battery not do discharge them below a level of 2.8V per cell always use a controller with build-in LiPo cut-off or an external LiPo cut-off module like the ones from Carson Model Sport (above in a Tamiya TamTech Gear chassis) or Team Novak (see below). Make sure external modules suit the battery packs you have as most of them only work with a specific number of cells. The Novak item for example is available for 2S to 4S (7.4 to 14.8V) packs.
External modules are looped between the battery and the controller and cut off power when the batteries voltage level drops below a specific value. The same applies to controllers with build-in LiPo cut-off. They either detect the number of cells once the battery is plugged in or you define the battery type by changing the parameters within the controllers software.
Next time
Now that you know what steps to take to switch from NiMH to LiPo batteries it's time to take care of charging and storing your investment. Stay tuned until next week when our Guide to charging and storing LiPo batteries hits your screen!
Links:
www.carson-modelsport.com
www.maxamps.com
www.teamnovak.com
www.teamorion.com
www.vampire-racing.com
