6 ms·

Thanks for the comment! The one capacitor I put seems to be enough for my needs for now :) But it's great to hear what's the correct thing. > I'd put another 0

by majke 14y ago

Thanks for the comment! The one capacitor I put seems to be enough for my needs for now :) But it's great to hear what's the correct thing. > I'd put another 0.1uF close to the input of the regulator, and another 100uF across the battery. Interesting. I (naively) thought that a capacitor near a LiPo battery is illegal as you're not allowed to charge the battery directly. I thought when the battery power drops a capacitor will be doing exactly that. Can you explain why that's untrue? Update: in other words: What's the difference between putting a capacitor near the battery and "charging"?

mindslight 14y ago
Well I'll just first disclaim that I don't have any design experience with Li-Po batteries, although reading about them I don't see any odd requirements. The guideline to not "charge them directly" is in contrast to say lead-acid batteries, which you can simply hook up to an appropriate voltage supply and let them sit indefinitely ("trickle charging"). To the extent that you need to worry about it, the voltage on the two will be the same. The battery power only drops as you're drawing current. The point of the capacitor is to smooth out changes to the load by supplying current "first". Your capacitor will never get "more" charged than the battery somehow. The main difference versus "charging" is that you have no external energy source. From a slightly more advanced perspective, the reason for the capacitor is to smooth out the (possibly bidirectional!) transient loads on the battery. It's quite possible that your "inductive buzzer" (depending on how it's driven) is actually backfeeding a little current through the arduino and onto the supply rails. Your battery will never be overcharged this way because any such energy came from the battery itself, but smoothing out the spikes with a capacitor eases the stress on the battery. In fact, I'd be surprised if the arduino board didn't have a decent-sized capacitor immediately on its supply lines, and this is part of the reason.
moreati 14y ago
This is limited electronics knowledge, plus conjecture. Buyer beware: - Direct (unmanaged) LiPo charging is to be avoided because the cells react so violently to overcharging. - Compared to a LiPo cell even a 100 uF capacitor contains essentially zero energy. The capacitor won't overcharge the LiPo, because it would almost immediately expend the charge it stored

by majke 14y ago

mindslight 14y ago

Well I'll just first disclaim that I don't have any design experience with Li-Po batteries, although reading about them I don't see any odd requirements. The guideline to not "charge them directly" is in contrast to say lead-acid batteries, which you can simply hook up to an appropriate voltage supply and let them sit indefinitely ("trickle charging"). To the extent that you need to worry about it, the voltage on the two will be the same. The battery power only drops as you're drawing current. The point of the capacitor is to smooth out changes to the load by supplying current "first". Your capacitor will never get "more" charged than the battery somehow. The main difference versus "charging" is that you have no external energy source. From a slightly more advanced perspective, the reason for the capacitor is to smooth out the (possibly bidirectional!) transient loads on the battery. It's quite possible that your "inductive buzzer" (depending on how it's driven) is actually backfeeding a little current through the arduino and onto the supply rails. Your battery will never be overcharged this way because any such energy came from the battery itself, but smoothing out the spikes with a capacitor eases the stress on the battery. In fact, I'd be surprised if the arduino board didn't have a decent-sized capacitor immediately on its supply lines, and this is part of the reason.

moreati 14y ago

This is limited electronics knowledge, plus conjecture. Buyer beware: - Direct (unmanaged) LiPo charging is to be avoided because the cells react so violently to overcharging. - Compared to a LiPo cell even a 100 uF capacitor contains essentially zero energy. The capacitor won't overcharge the LiPo, because it would almost immediately expend the charge it stored