That’s important when turning a board on and energizing it, but aren’t most chargers just simple barrel jacks? Those don’t have any form of resistor on them.
Oh didn’t see the charger part. The spark is caused by a difference in voltage. If the charger is plugged in, the voltage difference is smaller (let’s say a maximum of 9 volts on 10s between a 42v charger and a battery at 33v).
Right, but is that spark a problem? I don’t usually see people doing anything with them, but I’ve also seen plenty of blackened charge ports as well.
If the voltages are similar there shouldn’t be a spark. I forgot to say this in the last message. If the charger is plugged in there shouldn’t be a spark
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@Evwan this statement is kinda true but doesn’t tell the whole story.
@frankthedragon the spark when plugging the ESC into the battery is caused by “in-rush current.” The ESC has a large bank of capacitors that, when connecting them to power, want to fill up to full capacity ASAP (think milliseconds). That massive rush of current happens in the millisecond that the connector makes contact, and since there is momentarily a massive rush of current going through an extremely small surface area on your connector, it sparks.
As Evan explained, an XT90S connector has a resistor built into it that limits the in-rush current, forcing the capacitors to charge more slowly, so no spark happens.
Now to tie it back to your original question about charge ports. Your charger also has capacitors inside of it (at least, most of our chargers do). If your charger is un-plugged from the wall and you plug it into your board, you will in fact get a spark at the charge port on your board. It’s the exact same phenomenon of in-rush current, basically the capacitors in your charger sucking a massive amount of current from your board’s battery for a moment until they are full.
The reason that we dont need an XT90S or any other type of antispark charge port is because you can easily mitigate the risk of sparking by simply plugging your charger into the wall before plugging it into your board. This allows the charger to fill it’s own capacitors from the wall power, rather than from your battery. Then when you plug it into your board, there should be no spark.
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Hey there! I just upgraded my board to a 12s, and I only have a 10s charger at the moment, the 12s is coming sometime later this week. I is it safe to charge with the 10s charger? It has a Bestech BMS in it as well. I figured it wont get to full charge but I want to be safe it wont hurt anything.
It’s only gonna charge it to 42v if the BMS even accepts the voltage. 42v is close to dead. There’s no point I’d recommend buying the right charger and just wait.
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When chargers are in action their voltage “moves” to match the pack voltage, so a 12S charger is only at 50.4V when it’s basically not charging. You can see this in action by sticking a multimeter across the discharge port while charging and watching the voltage creep up to the full voltage.
With that in mind, I’m fairly sure no BMS is gonna care if your charger voltage is below 50.4 (because it’s supposed to be most of the time) as long as it’s not so low that current flows out of the battery into the charger. Open to corrections though
Anyone know why battery resellers add these kinds of extra stickers to their cell? Is it for ease of knowing what cell it is when sorting them or something?
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I’ve heard it’s for shipping/customs purposes, but dont quote me on that.
@Battery_Mooch probably knows.
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Have a look here it has a really good database of most cells, hope it’s not but whenever I see a sticker like that i expect the worst.
Never not found a cell there
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Yeah that was my initial expectation too, but I peeled back the sticker on one of them and it appears to be the cell I ordered (and I’ll probably peel them all off when I make my pack) . I think @BenjaminF might be right on this one.
I ordered from bulk battery, which from what I’ve read is a reputable seller so Im not expecting any surprises here 
(hopefully)
Best bet is to buy a charger and test it. Its pretty cheap, it tests capacity and IR, low IR means high current output. 20/30 ohms. If you look on aliexpres at cells they have actuall readings of cells and it shows their I/R
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In my experience those stickers dont indicate anything bad about the cells. As long as the cell wrappers under the stickers are all correct, then I dont think there is any reason to assume the cells are bad.
I usually do, just so that my glue can get a better grip on the cells rather than just sticking to the sticker lol.
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@BenjaminF is right, they’re for complying with shipping regulations, especially for the EU. They are added by the distributor/reseller, not the manufacturer, and can be ignored and removed. They don’t have anything to do with the original cell quality, where the cells came from, or the condition of the cells.
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@Battery_Mooch can you help me with a dc-dc converter recommendation?
So far i tried:
(It’s working great and provides 12V as you can see…)
And a variation of this thing that got melty in my box at minimum brightness (0.26A x2)
I just want something that won’t try to burn my lights or my board down, and provide 12V 2A without struggling.
So far i only found this
https://uk.rs-online.com/web/p/isolated-dc-dc-converters/7972703/
But the price is a bit tough to swallow, even worse considering i may want 2 for good measure
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feelsbadman, I have those exact ones
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How do they work for you?
And what loads do you put on them?
If I remember right those don’t perform and aren’t designed to run without a minimum load! It should be in the datasheet as a minimum current draw (most likely) or a minimum output resistance. If you’re a nerd there’s a very fun video that goes through some of the nuance of BECs here, it also explains why running these things at higher input voltages like 12S can be tricky:
If you’re not a nerd but do for some reason have access to individual resistors, put something in the region of a 1kΩ on the output and measure the voltage there to see if it really is goosed
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It was working, it gave 11.71V out. Put both lights at minimum brightness and it was fine, then started stepping up one of the lights. I think i got to 3/4 stage (so around 800mA + 260mA still low light) and it suddenly shut down both. Retried, reconnected, then it popped the fuse on my input wire. Replaced the fuse, read voltage out, surprise surprise 49V.
Seller is sending a replacement tomorrow but i have a feeling the model is just the first one (that almost melted at half amp) but potted in epoxy
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