Battery FAQ

What are the best batteries?

There are no best batteries per se, but there are some that outperform others in their category.  The definition of best is a matter of preference:  What do you want to get out of your E-MAXX?  If you want gobs of power and decent runtime, you will need some good 2400 mAh NiCd packs.  If you want decent power and long runtimes, you will need some 3000 or 3300 mAh NiMH packs.  You also need to take into consideration what charger you have.  Only certain chargers can safely charge NiMH packs, so if you have an older charger, you may need to upgrade it before buying those high mAh packs you want.  Another thing to take into consideration is how many times you want to run your E-MAXX in one day.  NiMH packs can be charged and discharged repeatedly in one day as long as you let them cool before charging them.  NiCd packs on the other hand should only be discharged and charged once per day.

Once figuring out what kind of batteries you want, you need to look at brands.  Some brands to stay away from would be Radio Shack, Dynamite Sport, Peak Performance Power Maxx, Orion V-MAXX, and any other packs that do not specifically state that they use genuine Sanyo cells.  Packs that will work well in you E-MAXX include packs by Trinity, Ballistic Batteries, Team Orion, Dynamite, DuraTrax, etc. that specifically say they use Sanyo cells.  Besides Sanyo as a name brand of cell, Panasonic and Gold Peak (GP) are popular brands, though not so much as the Sanyos.

After you have picked the type of battery and brand of battery, you need to pick what assembly form you want you pack in, and what you want done to the pack.  By this I mean, do you want a stick pack where the cells are arranged end to end, or a side-by-side pack where the cells are arranged side-by-side (hence the name).  Side-by-side packs have lower resistance due to the thick copper-core battery bars they use to connect the cells.  When I stated above that you need to pick what you want done to the pack, I mean do you want the cells to be matched or unmatched; zapped or not zapped.  Getting matched cells means that the cells are tested and grouped with other cells that produced the same results.  In grouping similar cells, you are ensured to have all cells working together equally and thus you get longer runtimes and more power.  Zapping the cells increases the voltage so that they produce more power.  Zapping and matching are both preferable when buying packs, but remember that they come with a higher price than unmatched, unzapped packs.

Is one brand of battery better than another?

            Just as there is really no best battery, there is really no best brand.  Some brands are more popular than others, but they all have their pros and cons.  Some people resort to the low cost brands of batteries such as Peak Performance Power Maxx or Radio Shack.  Most of those people end up buying more expensive batteries after the low cost ones die.  Trinity, Orion, Ballistic, and other name brands all produce good matched and zapped battery packs.

How much runtime does the E-MAXX get?

            This question has a LOT of variables that affect the answer, and, therefore, one cannot just give a number and have it be definite.  Some factors that change runtime are type of motors, mAh rating of cells, brand of cells, number of cells, arrangement of cells, charge rate used, type of connectors, terrain, and driving style.  Of course there are many other factors, but these are the biggies. 

Type of motor- If you are running the stock Titans, you will most likely see better runtimes than if you are running modified motors such as the Trinity Monster Maxx series or Reedy BaddMaxx.  If you run brushless motors, you will most likely get better runtimes than with the stock Titans.

mAh rating of cells- As a rule of thumb, the higher the mAh, the longer the runtime.

Brand of cells- Typically name brand cells such as Sanyo, Panasonic, or Gold Peak will give longer runtimes than generic cells found in Radio Shack, Peak Performance Power Maxx, and Dynamite Sport packs.

Number of cells- The more cells you have, the higher voltage you supply to you motors, and the higher current draw you batteries will receive.  More current means less runtime.  Therefore running two 6-cell packs will achieve more runtime than running two 7-cell packs.

Arrangement of cells- Side-by-side packs tend to have a lower resistance than stick packs.  This means that in high current draw applications, less heat is produce by the pack; therefore less power is wasted and longer runtime is achieved.

Charge rate used- As another rule of thumb, the lower the charge rate, the longer the runtime.  If you charge you packs at 6 amps, you will get great punch and fairly short runtimes.  If you charge at 2 amps, you will have great runtimes and decent punch.

Type of connectors- The stock Tamiya style connectors are, in simple terms, junk.  They get a looser connection quickly with use and that gives them a high resistance.  This produces heat, which causes wasted power.  By installing “zero loss” plugs such as W.S. Deans 2-pin Ultra Plugs or DuraTrax Power Poles, you can reduce wasted energy and increase your runtimes.

Terrain- If you run on road with 6-cell packs and the stock motors, you can expect a discharge rate of about 15 amps.  When you go off-road, you can expect the discharge rate to increase to about 20 amps, and it will go up even more if you get into rough terrain.

Driving style- If you drive with a “lead foot”, or in this case, a “lead finger”, you can expect to have shorter runtimes than someone who is easy on the throttle.  It is doubtful that you need an explanation for that.

With all that said, you can determine a ballpark figure of what you runtime will be.  As stated above, when running 6-cell packs, the average current draw on road will be around 15 amps, and off-road will be about 20 amps.  There is a math equation you can use to figure out a maximum and minimum runtime to be expected based on you battery pack.  Take them mAh (milliamp hour) rating of you battery pack and divide it by 1000 (shift the decimal 3 places to the right) and that will give you the Ah (amp hour) rating of your pack.  If the pack is 3000 mAh, it will be 3 Ah.  Set that value equal to the discharge rate times a variable number of hours.  So, your maximum runtime formula will be:

Amp hour rating = 15 amps (x hours)

Your minimum runtime formula will be:

Amp hour rating = 20 amps (x hours)

Here is how to use that formula.  Assuming you are using 3000 mAh packs, the math you do will be as follows:

3000 mAh/1000 = 3 Ah

3 Ah = 15 A (x hours)

3 Ah/15 A = x hours

.2 hours = x

.2 hours ( 60 minutes/hour) = x minutes

12 minutes = x

3 Ah = 20 A (x hours)

3 Ah/20 A = x hours

.15 hours = x

.15 hours ( 60 minutes/hour) = x minutes

9 minutes = x

That is how you can get a basic idea of what you runtime will be using the mAh rating of your battery packs.  These values are not set in stone, but you can almost guarantee that your runtimes will not be greater than your maximum runtime value assuming that you run 6 cell packs with stock motors.  If you run 7-cell packs, expect your amp rates to be 17.5 A to 23.3 A.  If you do run 7-cell packs, you should use those amp rates to do the math above rather than the ones shown above.

Here are the ballpark runtimes for some popular mAh ratings of 6-cell battery packs:

1500 mAh-  4.5 to 6 minutes

1700 mAh-  5.1 to 6.8 minutes

2400 mAh-  7.2 to 9.6 minutes

3000 mAh-  9 to 12 minutes

What is cell reversal?

            Cell reversal is when you discharge a cell past its limit and actually cause the polarity of the cell to be reversed.  Once a cell is reversed, it is possible to correct the cell by applying a voltage across it the way you normally would to charge it, thus in opposition to the new polarity of the reversed cell.  This does not always work, but if it does, the cell will never function as it did originally.   That is why it is easiest to just not over-discharge you packs.  Be sure to never go below .8 volts per cell, since that is where most cutoff devices on dischargers stop.

What are series and parallel?

            Series and parallel are different ways of hooking cells or battery packs together to achieve a certain voltage or mAh rating.

In series, the voltage of the batteries is added together and the current supply is

the same as one of the batteries (ie. two 6 cell 3000 mah packs in series would

be 14.4 volts and 3000 mah).  Here is a diagram:

In parallel, the voltage of the batteries stays the same and the current supply is

added together.  Thus when you have two of the same mah rating batteries

together, the mah rating doubles (ie. two 6 cell 3000 mah packs in parallel would

be 7.2 volts and 6000 mah).  Here is a diagram:

Keep in mind that while you double the mAh rating by putting two packs in parallel, you also add weight to the truck.  While your runtime will increase, but it will not be double what you would normally get.  Also remember that you should not run packs in parallel unless they are matched, because otherwise they can finish discharging at different times, and the packs that die first will be run down too much.  In doing this you run a high risk of reversing some of the cells in that pack.