DC to DC converter question concerning amps provided vs amps needed on

[Spleeft]

I have an electric dog collar combo that I want to be able to charge off my RV 12v system. This dc to dc converter covenrts the required voltage ( 12v to 5v ) but provides 5 amps and all I need is 1 amp. DC to DC converter Can I use it without any damage to the dog collar and remote ? Here is a pic of the wall charger that cam with the e collar .

 

[nosys70]

electricity is not water.
with water, when you put pressure in the pipe, it will force its way through any hole it finds.
with electricity, it is not a push system, it is a pull system.
You created a demand on your side, and the electricity comes to you. No demand and no electricity flows.
So, when devices are rated, they show the maximum demand they can issue.
So your charger is asking 0.2A when on AC, that translate to an output of 1A under 5V.
So if you connect your collar to a DC 5V source, it should not require more than 1A (and probably well under).
and your duty is to make sure the source of energy is able to provide at least 1A (but it could be a multi megawatt nuclear power plant, it would make no difference.)
So you can take a 10A 5V power supply , it will never be asked more than 1A from the collar.
since devices work well when they are in use with the rating range , you will better use a DC converter that is able to deliver between 1-2 A, that limits the price, size , weight and loss in heating.
But if you want to take advantage of having one 5V source to connect not only the collar, but also charge your smartphone and other 5V devices, you could target a DC converter able to support 5-10A.
This is a strategy that can be your choice.
have one central power supply that provide 5V for everything that requires 5V, or use POS (point of supply) properly sized for each device.
This is something you find in modern cars.
Before , all was connected on the 12V from the battery and running at 12V.
With modern technology, lots of devices are running at 5V or even lower (from 1.5 to 9V).
so each device comes with its own DC/DC converter that is sized to supply just the load it is connected on.
it is cheaper on cabling and connectors.

 

[Spleeft]

Awsum, thnx , nosys70 !

 

[KauaiMolokai]

Great explanation nosys70. I agree with you completely.

But... in his case most likely the original charger performs 2 functions - it supplies power to charge the items he's charging, AND it limits the current sent to those items to 1 amp. I'm guessing that the items to be charged can accept much more than 1 amp, which they will get if he uses his 5 amp supply, but the internal batteries in these items will be damaged/destroyed by having 5 amps available to them. Its why you don't charge your car battery, if its discharged, with a 500 amp source. You limit the charging current provided by your charger to 2, 6, or 10 or whatever amps. Sure the battery would take 100+ amps, but it would boil and be ruined.

 

[Spleeft]

Thanks for the reply K,
Ive been searching Amazon and there are lots with varies reviews. Is there a "go to " brand for these?
Thanks for any help

 

[tictag]

You might want to consider buying a cheap buck converter board, a bit more DIY 'cause you'll need to DIY your own connectors, but most have both voltage and current configuration (i.e. CC/CV) and typically sub $10 delivered. Search Amazon for 'buck converter'. I have this one in my wishlist but I need it for a high power application (drone battery charging).

 

[Spleeft]

I found the batteries that are in the transmitter and receiver." Replacement Li-Po Battery 3.7 400mAh (2 hour charge time) ". So Ill be charging two of these at the same time ( transmitter and receiver collar ). The wall charger in pic actually splits to two male 5.5mm barrel plugs. what converter would be optimal? The 5v 1amp , correct? 3a or 5 amp could damage these batteries??

 

[kernel]

The collar has to have some kind of charge limiting. The plugins are all just dc power from a switching wall wart power supply. Some devices are crude but the thing should have protection and control.

 

[Spleeft]

The collar has to have some kind of charge limiting. The plugins are all just dc power from a switching wall wart power supply. Some devices are crude but the thing should have protection and control.

Thanks for the reply,
Are you saying that the remote and collar should already have protection and control, or whatever dc to dc converter I use should have protection and control?

 

[nosys70]

if the powersupply you use is a "charger" , meaning there is some battery management inside, then there si probably an indicator (even a basic LED) that will give the indication of the SOC. Red led for charging, Green when charged at worse.
this is the case for most electric bicyle for example.
but if the power supply is just a "dumb " power supply , like most smartphone have, you can take any , as long the voltage is ok and it will work.
I got dozen of 5V charger for my devices, and usually i pick any that is at hand , form 500mA to 5A and never get any problem.
Those using a special limiting charger usually have a special plug. (like my segway, electric bicyle, electric scooter, drill machine, cameras, and so on). Most device that have a non removable battery have the charging BMS included.

 

[Spleeft]

Or I could just buy one of these and install a cigarette lighter plug ! https://www.educatorcollars.com/5v-auto-charger-for-2015-300-and-400.html
thanks for the patience/replies.

 

[tictag]

If these devices are fitted with a LiPo battery I'll be willing to put my own money on a bet that they'll have their own charging and protection circuits. LiPo cells are intrinsically unstable and highly sensitive to over-charging and thermal runaway, hence the need for internal charging and protection. You'll see the protection board on the cell, it'll look something like this:



Another thing to consider is that the USB standard allows for 'negotiation' of charging parameters meaning that it is even further unlikely that a 'wrong' charger will cause problems.

If you wanted to be crazy-paranoid-safe, you could get a USB tester (I personally have this one, but much cheaper alternatives are available) and measure the charging parameters of your official charger, then replicate those exactly with a programmable charger/buck-converter.

In short, it is my opinion that any 5V supply will do you, whether that supply is only capable of delivering 1W, or 1GW. Other opinions are available!

 

[KauaiMolokai]

What a great thread! I learned a lot just from this thread alone. In fact I learn the most when I'm wrong ;-)

Awesome that you found what battery the devices have! I had no idea that Li-Po batteries were used in such small devices. Thanks for that.

And I agree, but its only my best guess, that if you have this level of sophisticated battery that it likely has its only built in "current limiter" of some sort.

No doubt you'll find out if you charge them with your 5A charging system. Please let me/us know how it works out. I was going to just watch this thread and see what the people smarter than me advised. Glad I opened my mouth.