Comparison
of 3 existing Battery types
Prepared by: Pete Steinke, Oct/2006
IMPBA# 19541S NAMBA# 102
In this document I will compare 3 currently available Battery types to establish a guideline on how to integrate new battery chemistries into a voltage based standard from the current cell count/sub-c size based standard used by IMPBA an NAMBA
It does not propose mah limits on new cells
It was done in hopes of integrating new cell technology into racing while maintaining fair, rule based racing.
It is clear to me that the existing nimh cells are considered expendable items by a large majority of racers. The benefit often(not always) going to the racer who is willing to expend them fastest. The new cells have shown promise in extending cycle life and reducing cell costs while maintaining the performance and even increasing it over the current racing setups.
Combining cell types fairly is wrought with what ifs. In an ideal racing world there needs to be certain rules to maintain fair competition between racers. Fuel type rules are common and we see many different examples of this ie: Gas vs. Nitro vs. Electric. Sub-C cells have been the electric fuel standard of racing for over 20years. We are at crossroads of rechargeable battery technology and need to consider using these new cells. The racers are demanding it!! We can no longer base our rules on cell count/sub-c size. We need a Voltage based system. Here is my attempt.
|
Class
|
Nimh |
M1 |
Lipo |
Max
Voltage |
|
M |
4
cells |
1S |
1S |
6
Volts |
|
N |
5-6
cells |
2S |
2S |
9
Volts |
|
O |
7-9
cells |
3S |
2S |
12
Volts |
|
P |
10-12
cells |
4S-5S |
3S-4S |
17.5
Volts |
|
Q |
13-18
cells |
6S-7S |
5S-6S |
25
Volts |
|
S |
19-24
cells |
8S-10S |
7S-8S |
35
Volts |
|
T |
25-32
cells |
11S-12S |
9S-10S |
45
Volts |
This chart is based on the “at rest voltage” of a fully charged pack. This will be the easiest way to tech packs. There is no counting cells. Put a meter on a fully charged pack. Done!! It’s simple and we don’t need to rewrite rules or test cells under load.
I tested Nominal, I tested under load and after many hours of analyzing data I believe this guideline to be the best option for allowing new and future rechargeable battery technologies into Fast Electric Boat Racing.
The
Proof is in the numbers!
The Following charts were created from the 14 Amp discharge
data using the first 250 seconds of a 499 second discharge. They show the actual
and average voltage drops from real numbers not manufacturers Nominal Voltages.
The data backs up my observations while testing these different cells in actual
boats. We see that in 6 cell
classes the average voltage drop difference between the 3 is less then .2 volts.
We see that as the Cell count/Voltage goes up the shortcomings of the
NiMh cells become apparent. Yet
still the Nimh can compete!!! Here’s an example.
32 cells
Nimh at Max Voltage of 1.4 volts
per/cell= 44.8 volts minus projected 5.17 volts gives us 39.63 volts to race with
10S Lipo
at Max Voltage of 4.2 volts per/cell= 42 volts minus projected 1.06 volts gives
us 40.94 volts to race with
12S M1
at Max Voltage of 3.6 volts per/cell= 43.2 volts minus projected 2.08 volts
gives us 41.12 volts to
race with
Looks
like some good Racing!!!
Here’s the numbers showing some tested
and projected differences in voltage drop.
LOU