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Jason Cortell
306 Kimball Hall
Ithaca, NY 14853
jbc2@cornell.edu
Phone: 607-255-7108
Fax: 607-255-2011
Battery data and care for Biorobotics Lab robots
Introduction: Three different batteries will be discussed here. The original MWB robot
(originally the Marathon Walking Brain, later the Marathon Walking ‘Bot) is equipped with 14V
nickel metal hydride batteries. The first version of Ranger used 11.1 V lithium ion batteries, set up
with six cells per pack – three pairs of parallel-connected cells in series. These have overcurrent,
overcharge, and over-discharge protection, but no charge balancing circuit. The more recent
Ranger incarnations use 25.9 V lithium ion batteries, setup up with seven series-connected cells
per pack. The circuitry in these also includes a charge balancing system.
Warning: Lithium-ion batteries must not be discharged to too low a voltage, nor charged
to too high a voltage. For our cells, as of this writing, the usable range is 3 to 4.2 volts. Multiply
by the number of cells in series to get the battery operating voltage range. Very bad things can
happen if you go outside this range. Below, and they can’t be safely charged again. Above, and
lithium metal forms, causing explosions or fire. See photo below of an overcharged battery. (From
http://green.autoblog.com/2007/08/29/video-dont-overcharge-your-lithium-batteries/)
Lithium-ion battery voltage drops significantly as the cells discharge. Below is a graph of
discharge voltage vs. capacity in amp-hours. Note how little is left after the voltage drips below
about 3.6 volts. You should not make a practice of draining the batteries to the point where the
automatic protection kicks in; there is little to gain in operation time, and the batteries can be
damaged. If they are discharged to the point of auto-shutdown, be sure to recharge them
immediately.
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Jason Cortell
306 Kimball Hall
Ithaca, NY 14853
jbc2@cornell.edu
Phone: 607-255-7108
Fax: 607-255-2011
11.1 volt six-cell lithium-ion battery packs:
Now used for the RC steering controller. These were originally used on the Ranger robot, but at a
fully-discharged voltage of only 9, they could not drive the 12V motors on the robot to their full
capability. Unfortunately, the motor controllers used then could handle only 14 V max, so using
higher-voltage batteries was not immediately an option. A 15V switching regulator module was
purchased to give a steady 15V regardless of battery charge, but the motor controllers were
replaced before it could be installed and tested (thus allowing new 25.9 V batteries to be used).
Storage: if lithium-ion batteries are allowed to discharge below 2.5 or 3 volts per cell, they cannot
be safely recharged. Therefore, periodic recharging is required.
The approximate model we have is described as follows by batteryspace.com, the supplier:
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Jason Cortell
306 Kimball Hall
Ithaca, NY 14853
jbc2@cornell.edu
Phone: 607-255-7108
Fax: 607-255-2011
Li-ion 18650 Battery: 11.1V 4800mah (53Wh) battery module with PCB (4.32)
Sale Price: $82.95
In Stock
Part Number: LCH3P2S3R2WR
Product ID # 2211
*
High quality 11.1 V Li-Ion rechargeable battery made of six pcs High quality Sanyo/LG/Other Top
Brand Korea 2400mAh cylindrical 18650 cells with PCB and polyswitch for full protection ( 3S2P)
*
The battery pack is wrapped by black PVC shrink tube
Voltage
Capacity
Protection
Voltage: 11.1V (working) 12.6V ( peak) 7.5V ( cut-off)
4800 mAh ( 53 wh)
* One PCB (10A) installed with the battery pack and protects the battery from
o Overcharge
(>12.6V)
o Overdischarge (< 7.5 V)
o Over drain
(> 10 Amp)
o Short circuits
* One 7 Amp polyswitch installed to limit max. discharging current at 7 A and to protect wrong
polarity
Prewired
6" length 18 AWG wire installed on the battery pack
Max. Discharging Rate
7 Amp limited by polyswitch
Dimensions
2.1" x 1.4" x 2.5" inch (Width x Thickness x Length)
Weight
10.2 oz ( 290 g )
Smart Tips
* You may choose our 1.5A Universal Smart Li-Ion battery charger + the connector adaptor to
recharge this battery pack. The estimated charging time is 4.5 hours
* Need similar size Polymer Li-Ion pack? Please click here to order seperately.
* Need a connector? Please find one here
Applications
* Perfect for building 10.8V battery pack for RC toy, robots, and DVD external battery.
* Ideal for replacing batteries of 12V HID ( 10 - 13W ) bike light and diving lights
Warning
* Li-Ion battery may be exploded if mis-using. We are not responsible for any damages or losses
caused by misusing (included but not limited to: mis-charging, mis-discharging, any changes of
this battery pack, mis-assembling batterypacks) .
* Always charge battery with attention. Battery pack shall be placed on a fire-proof place to
avoid any accident
* Please check battery polarity before plug battery into light. Never make wrong polarity
connection.
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Jason Cortell
306 Kimball Hall
Ithaca, NY 14853
jbc2@cornell.edu
Phone: 607-255-7108
Fax: 607-255-2011
Charging: To charge with the MRC Super Brain 989 charger, start by plugging the charger into a
15 volt power supply, 3 to 5 amps. Get the polarity right (also for the battery connection). Set the
charger to LiPo mode (for 4.2V max lithium polymer and lithium ion batteries), 4800 mAhr, 3 cells
(3 x 3.7V = 11.1V), and a charging rate of about 1.5 amps. The charging rate can probably go as
high as 4.8 amps (1C rate) if needed, check the data sheets. Start charging.
To charge with the Graupner Ultramat 12:
1) first plug it into a 12 to 14 volt power supply, 3 to 5 amp capacity.
2) Check that the battery chemistry selection is right (Lithium, LiIon) If the battery chemistry
shown is not Lithium (LiIo or LiPo), hold the program/mode button down for a second or so to
change the battery type. Once it says Lithium, press it again briefly to select the lithium type (Io =
ion, Po = polymer) using the +/- keys.
3) From the LiIo Manual (charge) option, select C:4800 mAh using the +/- keys.
4) Connect the battery (watch polarity!).
5) Battery check: Hold down the enter/start button for a second or so until the “Battery check”
message is shown. It should report finding 3 cells.
6) Start charging: press the enter/start button again briefly. The display should show various info,
including the amount of charge delivered.
25.9 volt seven-cell lithium-ion batteries: These batteries from batteryspace.com
have seven 2600 mAh cells in series. Up to seven of these seven-cell batteries can be connected
in parallel on Ranger as of May 2011, for a total of 49 cells.
As listed on batteryspace.com:
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Li-Ion 18650 Battery: 25.9V 2600mAh (67.34Wh, 4.2A rate) battery module with PCM (5.46)
Sale Price: $134.95
In Stock
Part Number: LCH4S7R1WR-2P
Product ID # 3338
* Note: This battery pack has been upgraded from the one with two pin universal connector.
charge terminal.Please click here to view picture of battery pack with two pin charging terminal
* 25.9V 2.6Ah Li-Ion Battery pack is made of 7pcs High quality Sanyo/LG/Other Top Brand
Korea 2600mAh Li-Ion 18650 Cell with PCM(10A limited), and packed 7 in series
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Jason Cortell
306 Kimball Hall
Ithaca, NY 14853
jbc2@cornell.edu
Phone: 607-255-7108
Fax: 607-255-2011
* Wrapped by heavy-duty Heat shrink tube
Voltage
Capacity
Protection
25.9 v (working) 29.4 V ( peak)
2.6 Ah (67.34wh)
18 V ( cut-off)
* One PCM(10A limited) is installed in the battery pack to balance charging and protect battery
module from
o Overcharge
(> 29.6 V)
o Over-discharge ( < 16.1V)
o Over drain ( > 10 Amp)
o Short circuits
o Must wait min of 30 minutes after battery is fully charged to allow the pcm to perform
balance function on all the cells within the pack.
* One 4.2 Amp polyswitches installed to limit max. discharging current and to protect wrong
polarity
Pre-wired
* Charge / discharging terminal: 6" wire of 18 AWG wire without connector
Max. Discharging Rate
4.2 Amp limited by one polyswitches.
Dimensions (LxWxH)
5.3"(135mm) L x 1.4"(35mm)W x 2.9"(74mm)H
Weight
14.4 Oz (410 grams)
Smart Tips
* You may use 1.2A Smart Li-ion battery charger to fast charge the pack via only charging
terminal with 2.6 hrs charge time.
o Must connect to battery with correct polarity by Connector Adaptor: from 2 pins Female
Universal to Clip., which come together with charger )
+
Red clip = Positive
+
Black clip = Negative
o Batteryspace.com will not be responsible for any damage caused by misuse.
* Optional for Fire Retardant Bag: 295mmx230mmx75mm.Please click here to buy separately.
* If you connect two of these modules in parallel, you can build a 25.9V 10.4 Ah Battery pack with
a 8.4 Amp discharge rate.
* You can connect this battery to DC-DC regulators to provide 3V - 24V output
* Need a connector ? please find one here
Applications
* Replace 24 V NiMH battery pack with much lightweight
* RC robot and RC aircraft with higher energy needs
Warning
* Please note this battery is for R&D use only and NOT for individual customers. We are not
responsible for any damages or losses caused by misusing (included but not limited to: misuse,
any changes of this battery pack, mis-assembling batterypacks)
* Please never discharge the battery pack beyond its Max. rating
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Jason Cortell
306 Kimball Hall
Ithaca, NY 14853
jbc2@cornell.edu
Phone: 607-255-7108
Fax: 607-255-2011
Note that these batteries have a “charge balancing function,” in addition to the
overcharge/overdischarge/short circuit protections of the 11.1 V batteries. This has a couple of
implications:
A) Battery drain: the charge balance function (or something on the board for this battery) draws a
constant small current. This will discharge the battery beyond repair if the battery is not recharged
periodically. They must be charged every couple of months, or they will be ruined. In
addition, do not leave them in a fully-discharged state for even a couple days, or they may not
recover.
B) Post-charge rest period: After charging, allow the battery 30 minutes to balance before using it
or plugging it into the robot.
C) The batteries must be charged individually, unlike the 11.1V batteries which could be charged
while connected in parallel to the robot. To make this a bit easier we have four specialized 25.9V
“smart chargers.”
Charging with the “Smart Chargers”:
First, make sure you have the right charger and the right connector. It should specify that it is for
a 25.9 V Li-ion battery. Then plug it into the battery (which must be disconnected from all other
batteries, and attached only to the charger). A red light indicates charging. A green light may
mean that the battery is charged, but with several of the batteries this appears not to be true; the
charging appears to have stopped while the battery is not up to full charging voltage.
These charge at 1.5 amps, so a 2.6 amp-hour battery will take something like two hours to
become mostly charged, and another hour or two to top off to the full 29.4 volt charge.
Charging with the MRC Smart Brain 989: To charge with the MRC Super Brain 989 charger,
start by plugging the charger into a 15 volt power supply, 3 to 5 amps. Get the polarity right (also
for the battery connection). Set the charger to LiPo mode (for 4.2V max lithium polymer and
lithium ion batteries), 2600 mAhr, 7 cells (7 x 3.7V = 25.9V), and a charging rate of about 1.5
amps. The charging rate can probably go as high as 2.6 amps (1C rate) if needed, check the data
sheets. Start charging.
The Graupner Ultramat 12 does not go to a high enough voltage to charge 7 cells in series. An
adjustable DC power supply can be used in some cases, but you must limit the voltage to 29.4
volts, and the current to 1.5 amps. Do not try this if you don’t know how, or are unwilling to check
things first with a voltmeter. Don’t rely on the power supply displays.
Connecting batteries in parallel, and attaching them to the robot:
Disconnect each battery from the robot before recharging it.
Warning: All batteries must be at the same voltage before connecting them to the robot (in
parallel)! Otherwise, large currents can flow as some batteries discharge into other batteries.
Allow the battery to rest after charging for at least 30 minutes, then measure its voltage. After
charging, this should be between 29.0 and 29.4 volts. Match battery voltages to within +/- 0.05
volts of each other. (I don’t actually know what happens when they aren’t, but nothing bad seems
to happen at this level of variation.)
14.4-volt 12-cell nickel metal hydride batteries (on MWB robot):
This battery was originally intended for a Roomba, but we separated it into two 6-cell pieces to
balance the weight on the robot better. So now they look like something the TSA would be very
unhappy to let on board an airplane: cylinders and wires wrapped in black duct tape.
The battery stays connected to the robot while you charge it, but electrically isolated. Obtain
some suitable color-coded banana plug cables (red = plus, black = negative), and plug a charger
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Jason Cortell
306 Kimball Hall
Ithaca, NY 14853
jbc2@cornell.edu
Phone: 607-255-7108
Fax: 607-255-2011
to the banana jacks on the front of the robot. Be sure the toggle switch is in the center (off)
position while you do this. When you are ready to start the charger, move the switch to the bottom
(the charge position, down toward the robot’s feet). The up position turns on power to the robot.
Either the Graupner Ultramat 12 or the MRC Super Brain 989 charger can be used. Don’t try to
charge this with a regular power supply.
Charge settings: The battery is 14.4 volt nominal, with 12 cells of about 2.8 amp-hours each.
The charge current should be no more that 0.5 amps. Although the Roomba itself can charge its
batteries faster than that, it relies on a temperature sensor to know when they’re done. So expect
a full charge to take six hours or more.
Charging: To charge with the MRC Super Brain 989 charger, start by plugging the charger into a
15 volt power supply, 3 to 5 amps. Get the polarity right (also for the battery connection). Set the
charger to NiMH mode (nickel-metal hydride), 2800 mAhr, 12 cells (12 x 1.2V = 14.4V), and a
charging rate of about 0.5 amps. This should be as easy as selecting the correct profile number, if
it hasn’t been erased. Press the start button.
To charge with the Graupner Ultramat 12:
1) first plug it into a 12 to 14 volt power supply, 3 to 5 amp capacity.
2) Check that the battery chemistry selection is right (NiMH). If the battery chemistry shown is not
nickel-metal hydride, hold the program/mode button down for a second or so to change the
battery type.
3) From the NiMH Automatic (charge) option, select C:2800 mAh using the +/- keys.
4) Connect the battery (watch polarity!).
5) Battery check: Hold down the enter/start button for a second or so until the “Battery check”
message is shown. It should report finding 12 cells.
6) Start charging: press the enter/start button again briefly. The display should show various info,
including the amount of charge delivered.
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