So I've been looking for an LDO for my WeMos D32 project that runs on batteries. I'm planning on hooking up two 3.6V LiFePO4-batteries onto the board's battery connector but to my understanding, it can handle up to max 6V whereas those two batteries will deliver as much as 8.4V when fully charged. To my understanding, I need a 5V LDO voltage regulator for this.
I've done some digging and found several options and the previously recommended AMS1117-5. Though the issue with all these is that they either a) don't provide enough current (need at least 500mA I think?) and they consume a lot of current which isn't ideal.
Does anyone know any easy 3-pin LDO that could withstand the 8.2-8.4V, output 5V and ~500mA, relatively affordable and "easy" to get from like banggood and whatnot, while still consuming low currents (uAs and not mAs)? I'm pretty new to electronics so I'm not sure if this is simply a compromise I have to make (i.e. go with the AMS1117-5) or?
vaj4088:
A three pin LDO linear regulator is still going to waste a lot of power. A buck regulator may be preferable.
It's mainly cus I thought 3 pins is more simpler and I wouldn't need to ponder about where to connect the other ones. I'll give those a look though. Thanks!
Perhaps something like
Geekcreit® 5A XL4005 DC-DC Adjustable Step Down Module Power Supply Converter
would work if properly adjusted but the specs do not provide any low power information. The chip is about 90% efficient but the other parts used can bring the efficiency way down.
Wawa:
Why LiFePO4 (~3.3volt).
The board is designed for a single LiPo (~3.7volt) battery.
Leo..
The LiFePO4 battery I've been considering buying has a 3.6V typical output voltage so I figured if I had two I'd still get the board's LDO to convert it to 3.3V while giving me double the mAh. But I'd simply need an LDO of my own to make the board withstand two batteries. And I understood that LiFePO4 lasts slightly longer and they're a lot safer than LiPos.
Charging voltage of LiFePO4 is AFAIK ~3.6volt, but they quickly drop to 3.3volt when used, and stay there.
You could connect the LiFePO4 directly to the 3.3volt supply pin, bypassing the built-in regulator.
Charging (more than 3.6volt) could be a problem though.
Two batteries in series with a linear regulator last equally long as one battery.
Charging two cells in series is usually more complicated.
Wawa:
Charging voltage of LiFePO4 is AFAIK ~3.6volt, but they quickly drop to 3.3volt when used, and stay there.
You could connect the LiFePO4 directly to the 3.3volt supply pin, bypassing the built-in regulator.
Charging (more than 3.6volt) could be a problem though.
Two batteries in series with a linear regulator last equally long as one battery.
Charging two cells in series is usually more complicated.
Did you consider a powerbank.
Leo..
Ohh, I see. I thought they'd go up to 4.2V and then drop to regular 3.6V. Glad you corrected me on that one.
And actually, just when I had posted my reply to you I started wondering if I should utilize my powerbank. It's a 3.6V 16000mAh so I reckon that'd be far better. My only concern was that USB is supposedly 5V, so would that mess up the USB-port's voltage regulator?
I don't know if it would work for this type of battery, but it might be possible to use two batteries in parallel connected directly to the 3.3V pin of the D32. That would give you extended battery life without wasting any power in a regulator. But I don't know about charging. Are you going to build in a charger, or just replace the batteries as needed?
Most powerbanks have a minimum current requirement to keep them from shutting down. Also, most don't let you continue to power the device while recharging them. You would need to do some testing.
ShermanP:
I don't know if it would work for this type of battery, but it might be possible to use two batteries in parallel connected directly to the 3.3V pin of the D32. That would give you extended battery life without wasting any power in a regulator. But I don't know about charging. Are you going to build in a charger, or just replace the batteries as needed?
Most powerbanks have a minimum current requirement to keep them from shutting down. Also, most don't let you continue to power the device while recharging them. You would need to do some testing.
I was going to hook the board to a USB charger and it'd recharge the batteries. That was the idea anyway but if powerbank works then probably better off with that than more expensive and complex LiFePO4s.
Oh I didn't even consider those things. The powerbank does work while also charging it but I need to check the minimum current requirements since that would be an issue. Thanks!
Wawa:
WiFi boards draw enough current to keep most powerbanks on.
I have a 5000mAh powerbank, which keeps my WeMos D1 mini running for 36 hours.
Leo..
Ah. Very nice.
Is that even during deep-sleeps? I forgot to mention that I'm planning on using deep-sleep and also having my 2.8" LCD on hibernation unless awoken by touch. It hopefully makes the current consumption under 0.1mA but I'm guessing that's fine as well.
Unless I've got the wrong part, it looks like the Lolin D32 already has a built-in battery charger and voltage regulator. You would just connect a regular lithium ion or LIPO battery to it, and it will run off that. Then you just plug in USB when you need to recharge. You could even use something like twin 18650 batteries in parallel, and it should still work. So in effect it has a built-in powerbank, with no minimum current requirement.