I'm trying to build an arduino based basic circuit that needs a battery backup. I have a 12V supply that is not reliable.
I have a boost buck converter with current limiting and voltage adjustment pots. Can I install it to output 3.6V at 1A max (battery specs for charging), have it directly connected to the battery and have arduino monitor the battery voltage continuously so I can cut off charging using a mosfet or relay at something like 3.4V to be on the safe side.
And then I am planning to add 2 schottky diodes at the output of battery and my 12V input, connect them together and add another regulator to 3.3V to drive arduino. I assume this will ensure that if the 12V supply is present, it will not discharge battery in any way but in case of a power outage, the battery diode will forward bias and supply the necessary current.
The regulator modules have their own Schottky diodes and filtering capacitors so I'm mostly concerned if this is an appropriate solution? I could not find a decent charger IC module for the battery here in my country so this is what I came up with.
I'd probably have a relay into the battery charger defaulting to off state and trigger charging if I sense the battery voltage is lower than a threshold. The battery has a BMS too so I guess it will protect from overcharge and discharge even if I do not do that.
Thanks for the schematics! You could incorporate the relay part too.
In principal it looks doable but without technical data, datasheets for the parts, no definite reply is given.
When using Li based battery's "guess" is not good enough, a mistook can cause a very hot fire which would destroy your work area and possibly the building it is in. Spend some time researching the batteries you plan on using, be sure you understand how they need to be charged etc. There is a reason they are not allowed in airline checked baggage in the USA and many other countries. They must be placed in the carry on baggage. This states spare batteries and I am assuming if they are not in an approved device they will be considered spare.
Emphatically NO
...
Some "web" literature suggests that LiFePO4 can be charged to the 90%+ value with simple constant voltage (current limited.) These posts must be read carefully to understand the constraints and are based on the fact that common LiFePO4 cells never product pure lithium metal; thus the explosion/fire risk is minimized ... never goes to 0%, so safety protocols must remain in effect.
Uh, not sure why not. Will use a boost buck 3.3 fixed output converter with input range from 2.5v to 16v. Should step up or down according to input. Am I missing something?
I sincerely can not find anything other than the good old CC / CV details and charge graphs. Even went through some datasheets for lifepo4 chargers detailing the working principle and it looks like they do act like a basic cc / cv boost converter.
You are absolutely right though, that’s why I wanted to verify if I am missing something.
Would you guys suggest any other chemistry that might be easier to work with? I don’t have a space constraint and it is not required to be portable. Maybe sealed lead acid or something like that would be safer to work with?
I'm an EE but when dealing with rechargeable batteries, I opt to use modules designed specifically for the battery chemistry. I survived my youth and crazy motorcycle days; I do not want to be taken out by a iffy battery charger
The more I read though, more I’m convinced this is a simple process for Li Ion I am a computer engineer myself so I guess I tend to look at the algorithm in isolation without much regard to many external factors possibly affecting the charging process.
I ordered a dedicated powerbank module that can work with LiFePo4 series (IP2368) which can charge a pack from usb c sources with all the protection built in.
But then again, these ICs tend to favor full charge over battery health as the charge parameters show that it wants to quickly top up the cells as voltage drops and it might not be the best for my setup.
I am a computer engineer myself so I guess I tend to look at the algorithm in isolation without much regard to many external factors possibly affecting the charging process.