Hey we recently picked up some new batteries from a honda prius and were wondering since the rules for batteries only give rough idea on what batteries are allowed we were wondering if these are allowed. They are rectangular and flat in shape with terminals on bottom sides; positive on one side with negative on opposite.Output is about 6.2 V per battery and we have roughly 30 batteries but only plan to use 2 in junction with one another to produce the amount of voltage we need for the bot…In conclusion just wondering if these things are legal or not with the battery rules and whatnot…Thanks! 
R31 should answer your question.
R31 The only legal source of electrical energy for the ROBOT during the competition, the ROBOT
battery, must be a non-spillable sealed lead acid (SLA) battery with the following specifications:
A. Nominal voltage: 12V
B. Nominal capacity at 20 hour discharge rate: minimum 17Ah, maximum 18.2Ah
C. Shape: Rectangular
2016 FIRST ROBOTICS COMPETITION || GAME MANUAL || Section — 4 Robot || V1 || PAGE 22
© 2015-2016 FIRST®
All rights reserved.
D. Nominal Dimensions:7.1 in x 3in. x 6.6 in (+/- .1 in. for each dimension)
E. Nominal weight: 11lbs to 14.5 lbs
F. Terminals: Nut and bolt style
Here are the requirements for the battery for the 2016 FRC Season from the Game Manual. . .
{The only legal source of electrical energy for the ROBOT during the competition, the ROBOT
battery, must be a non-spillable sealed lead acid (SLA) battery with the following specifications:
A. Nominal voltage: 12V
B. Nominal capacity at 20 hour discharge rate: minimum 17Ah, maximum 18.2Ah
C. Shape: Rectangular
2016 FIRST ROBOTICS COMPETITION || GAME MANUAL || Section — 4 Robot || V1 || PAGE 22
© 2015-2016 FIRST®
All rights reserved.
D. Nominal Dimensions:7.1 in x 3in. x 6.6 in (+/- .1 in. for each dimension)
E. Nominal weight: 11lbs to 14.5 lbs
F. Terminals: Nut and bolt style
Examples of batteries which meet this criteria include:
■ Enersys (P/N: NP18-12, NP18-12B, NP18-12BFR)
■ MK Battery (P/N: ES17-12)
■ Battery Mart (P/N: SLA-12V18)
■ Sigma (P/N: SP12-18)
■ Universal Battery (P/N: UB12180)
■ Power Patrol (P/N: SLA1116)
■ Werker Battery (P/N: WKA12-18NB)
■ Power Sonic (P/N: PS-12180NB)
■ Yuasa (P/N: NP18-12B)
■ Panasonic (P/N: LC-RD-1217)
■ Interstate Batteries (P/N: BSL1116)
Teams should be aware that they may be asked to provide
documentation of the specifications of any battery not listed above.
Batteries should be charged in accordance with manufacturer’s
specification. The battery charger output should not exceed 6 amps
and they must have the corresponding Anderson connector installed.
(Please see the FIRST Safety Manual for additional information.)
Additionally, batteries integral to and part of a COTS computing device or self-contained camera
are also permitted (e.g. laptop batteries, GoPro style camera, etc.), provided they’re only used to
power the COTS computing device and any peripheral COTS USB input devices connected to the
COTS computing device and they are securely fastened to the ROBOT.}
From the manual
R31 The only legal source of electrical energy for the ROBOT during the competition, the ROBOT battery, must be a non-spillable sealed lead acid (SLA) battery with the following specifications:
A. Nominal voltage: 12V
B. Nominal capacity at 20 hour discharge rate: minimum 17Ah, maximum 18.2Ah
C. Shape: Rectangular
2016 FIRST ROBOTICS COMPETITION || GAME MANUAL || Section — 4 Robot || V1 || PAGE 22
© 2015-2016 FIRST®
All rights reserved.
D. Nominal Dimensions:7.1 in x 3in. x 6.6 in (+/- .1 in. for each dimension)
E. Nominal weight: 11lbs to 14.5 lbs
F. Terminals: Nut and bolt style
Examples of batteries which meet this criteria include:
■ Enersys (P/N: NP18-12, NP18-12B, NP18-12BFR)
■ MK Battery (P/N: ES17-12)
■ Battery Mart (P/N: SLA-12V18)
■ Sigma (P/N: SP12-18)
■ Universal Battery (P/N: UB12180)
■ Power Patrol (P/N: SLA1116)
■ Werker Battery (P/N: WKA12-18NB)
■ Power Sonic (P/N: PS-12180NB)
■ Yuasa (P/N: NP18-12B)
■ Panasonic (P/N: LC-RD-1217)
■ Interstate Batteries (P/N: BSL1116)
Teams should be aware that they may be asked to provide
documentation of the specifications of any battery not listed above.
Batteries should be charged in accordance with manufacturer’s
specification. The battery charger output should not exceed 6 amps
and they must have the corresponding Anderson connector installed.
R31 states which batteries are and are not allowed on the robot.
Honda Prius?
and were wondering since the rules for batteries only give rough idea on what batteries are allowed
R31 The only legal source of electrical energy for the ROBOT during the competition, the ROBOT battery, must be a non-spillable sealed lead acid (SLA) battery
Prius batteries are lithium, not SLA… and even if they were allowed, how would you charge them? Certainly not with an SLA charger.
Hey thanks to all for the info we were aware of R31 just unsure of like the actuality of it due to aquiring these batteries from a unknown source and only able to tell it was from a Honda Prius.We did not know they were lithium so yeah that answers that.
Unsure if commentary about hybrids or just general confusion…
…but funny.
Most batteries from the prius will be NiMH unless you have the plugin model. The 2016 version has an optional lithium battery
The Honda Prius does not use NiMH 
One thing many may not know is that all the Toyota Prius cars also contain a small good old 12V lead acid battery… And the car will not start if it dies, even if the drive battery is fully charged. And of course it is a custom type that is only easy to get from Toyota themselves and costs $200. They might be referring to this battery.
I do believe that batteries are required by law or regulation or both to have the type and voltage and some other key identifying information marked on them. It would be on a label (if any exist) or printed on the battery in ink of some form.
That being said, the nominal voltage should have given you the first clue that they weren’t legal: R31A is pretty clear on only 12V being allowed.
Re-read the OP: