alternative batteries for Monsterborg

Submitted by pablisch on Sat, 09/09/2017 - 20:28

Forums:

Hi, would it be ok to use a lipo battery in place of the 10xAA battery pack? Or are there any other recommended alternatives?

If lipo is ok, are there any particular you would recommend? including voltage and capacity. I was imagining a 4s lipo would be the right replacement.

Thanks,
Pablo

AlexFielder

Sat, 09/09/2017 - 23:07

I was wondering the same thing; I asked as much on the Kickstarter page.

I visited my local model shop here in Andover (UK) and they recommended a site called https://www.overlander.co.uk/ - I've not looked on there in too much detail but in theory if you can match the voltage required/provided by 10xAA batteries with one of their packs you'd be good to go.

According to the chap that recommended them, you can even ask for a custom build and they'll send it to you.

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piborg

Sun, 09/10/2017 - 14:14

You can use a LiPo, but there are some points you need to bear in mind:

  1. LiPos can be dangerous, if they get damaged they can cause a fire or explode!
  2. If you fit a LiPo underneath the MonsterBorg (where the AAs go) you will need something underneath to protect it from damage due to stones and other debris. I would recommend protecting it anyway so that flipping the MonsterBorg does not damage it either.
  3. A 4S LiPo would provide 14.8 V, remember to change all of our examples so the motors get the correct power.
  4. I would avoid any cheap or non-branded LiPos. Some are manufactured poorly and can present a fire risk.
  5. LiPos require special care when charging, make sure you buy an appropriate charger and do not exceed the charging rate for the battery.
  6. I would change the battery monitoring to the range of 12.8 V minimum and 16.8 V maximum to get a good battery charge display.
  7. LiPos should not be discharged below 3 V per cell. For a 4S LiPo this means you should stop using it once the power gets down to 12 V. Personally I would allow a little room for error and stop using the battery at around 12.8 V. If you made the change above this will be when the LED stays red even when stationary.

There is a great guide here all about LiPos and how to use them safely. It is a long read but better safe than sorry.

These are the power settings for a 4S LiPo:

# Power settings
voltageIn = 3.7 * 4        # Total battery voltage to the ThunderBorg (4S LiPo)
voltageOut = 12.0          # Maximum motor voltage

theborg

Sun, 09/10/2017 - 18:00

Is 4S Lipo required or is 3S enough (11.1V)? I noticed the Thunderborg specs say 7V-37V but is there an optimal value somewhere that should be the goal when planning the power supply?

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piborg

Sun, 09/10/2017 - 21:12

A 3S will work fine but there is a slight snag, the motors are designed to work at 12 V. This means that while everything will work the ThunderBorg will not be able to get the motors upto full speed. They will run at about 92 % speed from a 3S.

On the other hand the ThunderBorg can lower the output from a 4S down to 12 V. This means that the motors will be able to move at their intended speed. This is what the power settings in the script mentioned earlier are for :)

theborg

Sun, 09/10/2017 - 22:00

Thanks. I'm going to 3d print a housing for the battery to keep it safe.

Btw do I understand correctly that this little piece of code has the potential to fry the motors in case of a typo? I hope the 12V is marked somewhere on the motors in case I need to figure it out and don't have the examples near by :)

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piborg

Mon, 09/11/2017 - 10:02

You are unlikely to fry the motor by putting a bit too much power in. What will likely happen is that it will run faster but the motor itself will not last as long :(

The motors do have a sticker with 12V on them :)

mamue

Thu, 10/05/2017 - 12:41

If you set the power whit setMotorX( double ) to something below or equal 12/14.8 the motor will level the voltage. A 6V motor will most likely not burn at 12V provided that the output power is set to something appropriate (<=0.5).
I have ordered this one a few days ago: https://www.yuki-model.de/801055-brainergy-lipo.htm?shop=cn&SessionId=&a=article&ProdNr=801055&t=813&c=813&p=813 but didn't receive it so far.

cnobile2017

Sun, 10/29/2017 - 01:07

This is my setup for using Li-Ion batteries. I still need to protect the batteries better.

Images: 

mamue

Sun, 10/22/2017 - 12:45

You use a balancer? What Cells are you using?

cnobile2017

Sun, 10/22/2017 - 17:04

The batteries are LGABF1L1865, these are generally called 18650 batteries. Be forewarned that 18650 batteries come in many different mAh ratings these are rated at 3350mAh. The numbers in 18650 mean 18mm x 65mm and the zero means they are round, so it doesn't show on the battery since they are obviously round. See specs here: http://www.diypowerwalls.com/t-LG-LGABF1L1865-Cell-Specifications

I got the charge/discharge circuit here: https://www.banggood.com/4S-30A-14_8V-Li-ion-Lithium-18650-Battery-BMS-P...

This company also has great covered battery holders which I will be ordering myself. The one in the photo I already had but may swap it out for the covered one when I get it. I still need to find a safe place to put the circuit board, however.

seh7464

Wed, 05/23/2018 - 22:53

I'm interested in moving to 18650's but I have a question. These batteries are connected in series. So this charge/discharge circuit doesn't require removing batteries from series battery holder? Thanks ahead for any answer.

Steve

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piborg

Thu, 05/24/2018 - 23:05

You will need to be careful with the 18650 size batteries, they are generally Li-Ion / LiPo batteries and can be dangerous if they are not charged correctly!

Generally speaking it is NOT safe to charge LiPos connected in series unless the charger has some way of checking the voltage of each separate cell. This is what the smaller connector is for on typical LiPos. Since the battery holder only provides the main power connection you would need to add extra connections to each individual 18650 for charging. THIS CAN BE DANGEROUS IF WIRED INCORRECTLY, THERE IS A RISK OF FIRE AND EXPLOSION.

I would advise against trying to charge them in a holder at all, there are too many potential risks for mistakes. You should also follow any recommendations from both the battery and charger manufacturers.

seh7464

Fri, 05/25/2018 - 04:09

Thanks for info and the warnings. I'll probably just use an external charger designed for the task!

Steve

Neokey

Tue, 05/08/2018 - 19:22

Hello what 10x AA batteries can you recommend?

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piborg

Tue, 05/08/2018 - 21:13

We have found that GP 2600 work very well, we use them in the Formula Pi racing series and get about 3 hours of MonsterBorg driving from a full charge :)

We also use Eneloop AAs (1900 mAh) which do not last as long but they retain their charge when sat on the shelf. They get around 2 hours from a full charge running MonsterBorg.

Neokey

Thu, 05/10/2018 - 14:57

OK thanks. A question. Jessi or the new Strech? Which operating system do you recommend?

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piborg

Thu, 05/10/2018 - 16:37

Both versions of Raspbian will work fine with MonsterBorg, but I would personally suggest going with Stretch as it will be the version most people are now using.

The main advantage of using Stretch is that the latest copy will work with all available Raspberry Pis. Jessie does not support the new 3B+.

reestr_uk

Tue, 07/30/2019 - 20:22

Cognizant of all the warnings wrt protection of the battery, is using a lipo as simple as buying something like a 4S and then connecting it in place of the 10xAA batteries and changing the voltage on the scripts? I ask because I've just ordered a Mosterborg and trying to find a set of AA batteries and charger seems an arduous task, batteries tend to come in packs of 8. I'm not keen on using any AA batteries from the get-go if I can avoid it.

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piborg

Wed, 07/31/2019 - 14:23

Essentially yes, the scripts should just need the correct voltage settings and attach the LiPo instead of the battery pack. If you use the 9V style connectors then the power switch will work, if you use the V+ and GND screw terminals instead you will need to add your own power switch.

I would also strongly recommend you set the voltage monitoring levels on the ThunderBorg to match the LiPo as well.

Please read the Using LiPos - PROCEED WITH CAUTION post above carefully before doing this to be safe. The values listed in that post for both the scripts and the battery monitoring happen to be for a 4S LiPo.

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