I have a robot that I’m currently powering via cable and mains adaptor. I need to power it by battery so it can roam around a room. I’ve looked at which batteries to get, and I guess I’m going to get something like a NiMH battery. LiPo sound like a good idea, except for the whole exploding/setting on fire thing, the robot will be left alone while charging and if I burn down the office no-one is going to be pleased. So I’m thinking of buying something like this NiMH battery for my robot:
The problem I have is how to charge the battery. The robot needs to “dock” and charge unattended, rather than have someone change it’s batteries manually so standard consumer battery chargers are out. I also need to get charging status somehow so I can get remote status / prevent the robot from moving off until the battery is charged so some sort of SPI/I2C interface will be needed (the docking station will be a Raspberry Pi).
It looks like there are chips out there to do this sort of thing, like the LTC1759 (and more):
LTC1759: http://www.linear.com/product/LTC1759 (from http://parametric.linear.com/smbus|i2c|spi_controlled_battery_chargers)
Unfortunately I have 0 surface mount skills, or confidence that I could make a circuit out of that that would work. Does anyone have any suggestions for boards that already exist that use a chip like this, or suggestions as to how I could handle the charging?
Thanks
Will
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I’d suggest you take another look at lithium, at the hard cased protected
cells. 18650 is the common size.
They are a quid or so each, 3000mah ish, 3.7v. They are protected during
charge and discharge, and there are super cheap modules available for doing
the charging, and boost convertors available for turning the 3.7v into 5v
for powering your electronics.
This is the power system I used for the pimelapse camera, works pretty well
for about 3 hours playing.On 13 Oct 2013 01:00, “Will Jessop” will@willj.net wrote:
I have a robot that I’m currently powering via cable and mains adaptor. I
need to power it by battery so it can roam around a room. I’ve looked at
which batteries to get, and I guess I’m going to get something like a NiMH
battery. LiPo sound like a good idea, except for the whole
exploding/setting on fire thing, the robot will be left alone while
charging and if I burn down the office no-one is going to be pleased. So
I’m thinking of buying something like this NiMH battery for my robot:
http://www.amazon.co.uk/4050-0004-Tamiya-4700mah-Rechargeable-Battery/dp/B00D75JY7U/ref=pd_cp_k_h_b_cs_1
The problem I have is how to charge the battery. The robot needs to "dock"
and charge unattended, rather than have someone change it’s batteries
manually so standard consumer battery chargers are out. I also need to get
charging status somehow so I can get remote status / prevent the robot from
moving off until the battery is charged so some sort of SPI/I2C interface
will be needed (the docking station will be a Raspberry Pi).
It looks like there are chips out there to do this sort of thing, like the
LTC1759 (and more):
LTC1759: http://www.linear.com/product/LTC1759 (from
http://parametric.linear.com/smbus|i2c|spi_controlled_battery_chargers
)
Unfortunately I have 0 surface mount skills, or confidence that I could
make a circuit out of that that would work. Does anyone have any
suggestions for boards that already exist that use a chip like this, or
suggestions as to how I could handle the charging?
Thanks
Will
Will…I think Bob is on the right track here. Lipo in a hard case when
treated correctly are perfectly safe. Ignore the charging requirements and
yes batteries can explode in a spectacular fashion. YouTube is littered
with examples of how it can go wrong but mobile phones are all powered by
lipo batteries and they are fine…
You haven’t mentioned your power requirements. When running your robot
tethered to the mains how much current is drawn and what is the input
voltage to the robot? It is also an idea to do a locked rotor
test…measure the current draw with the motors stalled as that is your
worst case condition for current requirements
Once you have your power requirements known then you can choose a suitable
battery technology based upon power, weight and running conditions. If you
do go down the lipo route then definitely get a hard case version. You will
then need a suitable charging circuit and probably a step up boost
converter to get the required voltage. All standard stuff when using
rechargeable battery technology.
Don’t be afraid of surface mount stuff. There is always a simple solution
or way of breaking out the contacts to make it through hole.
I’m very confident that between Bob myself and you we could get a suitable
solution working.
Cheers
AlexOn 13 Oct 2013 08:56, “Bob Clough” parag0n@ivixor.net wrote:
I’d suggest you take another look at lithium, at the hard cased protected
cells. 18650 is the common size.
They are a quid or so each, 3000mah ish, 3.7v. They are protected during
charge and discharge, and there are super cheap modules available for doing
the charging, and boost convertors available for turning the 3.7v into 5v
for powering your electronics.
This is the power system I used for the pimelapse camera, works pretty
well for about 3 hours playing.
On 13 Oct 2013 01:00, “Will Jessop” will@willj.net wrote:
I have a robot that I’m currently powering via cable and mains adaptor. I
need to power it by battery so it can roam around a room. I’ve looked at
which batteries to get, and I guess I’m going to get something like a NiMH
battery. LiPo sound like a good idea, except for the whole
exploding/setting on fire thing, the robot will be left alone while
charging and if I burn down the office no-one is going to be pleased. So
I’m thinking of buying something like this NiMH battery for my robot:
http://www.amazon.co.uk/4050-0004-Tamiya-4700mah-Rechargeable-Battery/dp/B00D75JY7U/ref=pd_cp_k_h_b_cs_1
The problem I have is how to charge the battery. The robot needs to
"dock" and charge unattended, rather than have someone change it’s
batteries manually so standard consumer battery chargers are out. I also
need to get charging status somehow so I can get remote status / prevent
the robot from moving off until the battery is charged so some sort of
SPI/I2C interface will be needed (the docking station will be a Raspberry
Pi).
It looks like there are chips out there to do this sort of thing, like
the LTC1759 (and more):
LTC1759: http://www.linear.com/product/LTC1759 (from
http://parametric.linear.com/smbus|i2c|spi_controlled_battery_chargers
)
Unfortunately I have 0 surface mount skills, or confidence that I could
make a circuit out of that that would work. Does anyone have any
suggestions for boards that already exist that use a chip like this, or
suggestions as to how I could handle the charging?
Thanks
Will
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Thanks Bob and Alex, I guess I’ll have another look at lithium 
As for the power requirements, that I’m uncertain of. The total connected components are:
- Raspberry Pi
- Raspberry Pi camera
- Cheap wifi dongle
- 2 6v motors
- At some point a stepper motor
- MotorPiTX board
The MotorPiTX converts 7.2v to 5v for the Pi using a regulator (I’m not sure which type) and passes whatever is put into it onto the motors.
I have a 7.2v 700mA power supply that works as long as I am only trying to run about two of those things at a time, I’ve not been able to measure the total power requirements, but I do know that I’m going to need everything running at once most of the time. I’m guessing there’s some equipment at the space that we can use to measure the total requirements. Can I put a couple of LiPo batteries in to get to 7.2v or extend the working time?
Thanks,
Will.On 13 Oct 2013, at 10:08, Alexander Lang alexanderlang1980@gmail.com wrote:
Will…I think Bob is on the right track here. Lipo in a hard case when treated correctly are perfectly safe. Ignore the charging requirements and yes batteries can explode in a spectacular fashion. YouTube is littered with examples of how it can go wrong but mobile phones are all powered by lipo batteries and they are fine…
signature.asc (841 Bytes)
you can connect LiPo in series, but it does make charing as a pair
harder as you have to check the charge status of each cell.On 13 October 2013 12:30, Will Jessop will@willj.net wrote:
Thanks Bob and Alex, I guess I’ll have another look at lithium 
As for the power requirements, that I’m uncertain of. The total connected components are:
- Raspberry Pi
- Raspberry Pi camera
- Cheap wifi dongle
- 2 6v motors
- At some point a stepper motor
- MotorPiTX board
The MotorPiTX converts 7.2v to 5v for the Pi using a regulator (I’m not sure which type) and passes whatever is put into it onto the motors.
I have a 7.2v 700mA power supply that works as long as I am only trying to run about two of those things at a time, I’ve not been able to measure the total power requirements, but I do know that I’m going to need everything running at once most of the time. I’m guessing there’s some equipment at the space that we can use to measure the total requirements. Can I put a couple of LiPo batteries in to get to 7.2v or extend the working time?
Thanks,
Will.
On 13 Oct 2013, at 10:08, Alexander Lang alexanderlang1980@gmail.com wrote:
Will…I think Bob is on the right track here. Lipo in a hard case when treated correctly are perfectly safe. Ignore the charging requirements and yes batteries can explode in a spectacular fashion. YouTube is littered with examples of how it can go wrong but mobile phones are all powered by lipo batteries and they are fine…
Ben Dooks, http://www.fluff.org/ben/ bjdooks@googlemail.com
Ok…just guessing but I think you will need a pretty high capacity battery
to power all that stuff. A 2100mAh battery would be a start. You will then
have to boost this to above 6V to power the motors and Pi and associated
kit. Rough guess this would power your kit for maybe two hours…then it
would need charging etc.
Bring all the kit into the space and we can wire it up and measure the
current consumption and then select the battery and the other associated
circuitry.
AlexOn 13 Oct 2013 13:25, “Ben Dooks” bjdooks@googlemail.com wrote:
you can connect LiPo in series, but it does make charing as a pair
harder as you have to check the charge status of each cell.
On 13 October 2013 12:30, Will Jessop will@willj.net wrote:
Thanks Bob and Alex, I guess I’ll have another look at lithium
As for the power requirements, that I’m uncertain of. The total
connected components are:
- Raspberry Pi
- Raspberry Pi camera
- Cheap wifi dongle
- 2 6v motors
- At some point a stepper motor
- MotorPiTX board
The MotorPiTX converts 7.2v to 5v for the Pi using a regulator (I’m not
sure which type) and passes whatever is put into it onto the motors.
I have a 7.2v 700mA power supply that works as long as I am only trying
to run about two of those things at a time, I’ve not been able to measure
the total power requirements, but I do know that I’m going to need
everything running at once most of the time. I’m guessing there’s some
equipment at the space that we can use to measure the total requirements.
Can I put a couple of LiPo batteries in to get to 7.2v or extend the
working time?
Thanks,
Will.
On 13 Oct 2013, at 10:08, Alexander Lang alexanderlang1980@gmail.com wrote:
Will…I think Bob is on the right track here. Lipo in a hard case when
treated correctly are perfectly safe. Ignore the charging requirements and
yes batteries can explode in a spectacular fashion. YouTube is littered
with examples of how it can go wrong but mobile phones are all powered by
lipo batteries and they are fine…
–
Ben Dooks, http://www.fluff.org/ben/ bjdooks@googlemail.com
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The problem I have is how to charge the battery. The robot needs to
"dock" and charge unattended, rather than have someone change it’s
batteries manually so standard consumer battery chargers are out. I also
need to get charging status somehow so I can get remote status / prevent
the robot from moving off until the battery is charged so some sort of
SPI/I2C interface will be needed (the docking station will be a Raspberry
Pi).
I think I’m missing something here - why wouldn’t a standard NiMH battery
charger work? I’m assuming you will need to build some sort of mechanical
docking connector, but with that done I would just buy a standard battery
charger, remove its connector and connect the charger to the docking
connector.
The problem I have is how to charge the battery. The robot needs to “dock” and charge unattended, rather than have someone change it’s batteries manually so standard consumer battery chargers are out.
I think I’m missing something here - why wouldn’t a standard NiMH battery charger work? I’m assuming you will need to build some sort of mechanical docking connector, but with that done I would just buy a standard battery charger, remove its connector and connect the charger to the docking connector.
The robot will be controlled by the public so I need to disable certain robot functions while the robot is docked and the battery is charging.
I’d also like to be able to get stats on charge time, and any other stats available remotely, the robot will be a few thousand miles away
Will.
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Bring all the kit into the space and we can wire it up and measure the current consumption and then select the battery and the other associated circuitry.
Are you going to be around tomorrow? I think I might come in for the afternoon / evening.
Will.
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Will, I’ll be in the hackspace tonight from six onwards
AlexOn 16 Oct 2013 00:20, “Will Jessop” will@willj.net wrote:
On 13 Oct 2013, at 15:14, Alexander Lang alexanderlang1980@gmail.com wrote:
Bring all the kit into the space and we can wire it up and measure the
current consumption and then select the battery and the other associated
circuitry.
Are you going to be around tomorrow? I think I might come in for the
afternoon / evening.
Will.
