Hi! Im fiftteen and is wondering which battery i should get for 1800w brushless motor. I have a supermoto body im installing it on but i need a battery for around 120 dollar with charger since im fifteen and broke. Are those blue batteries 48v 20 000-100 000 mah battery good? Or should i serie connect 4 lead acid battery 12v 12 ah? Ive heard lead acid battery dont last long thats why... appreciate quick answers.
Which "blue batteries"? You'll need to provide a link to the specific ones you're considering, because color is not an indication of anything other than color.
And there are *many* different kinds of batteries that come in some form of blue color.
EDIT: I see you linked this one
Elcykelbatterisparkcykel 48v 100Ah 18650 Li-ion batteripaket 13 Series 3 Parallell + Laddare : Amazon.se: Bygg, el & verktyg
amzn.eu
which claims to be one hundred thousand mah, which is 100Ah. There is ZERO chance that it has that much capacity, so since that's a lie by the seller, you should assume everything else they say is also a lie, to be safe, and never buy anything from them at all.
Same thing for any other such seller.
Generally if a battery seems cheap for what it says it is, it's almsot certainly not what it says it is, and the seller is untrustworthy. That goes for most of the cheap batteries out there.
Most of the cheap ones also don't have proper protections, are built poorly of crappy cells (too often are actual recycled garbage cells), and are a fire waiting to happen. (and if they don't burn, they will certainly not do what they say they will, and won't do what they *are* capable of for very long before fading away or having any of a number of problems).
A good battery is likely to cost two or three times what the rest of the bike and motor / etc does.
I'm not sure where you can get a good safe lithium battery for the money you have, because most of these are going to come from outside your country, and you'll have to pay import taxes / duties and various fees.
If you can save up before buying one you'll be better off and safer.
If you can't, SLA is an option, as long as you charge it back up as soon as you stop riding (don't let it sit discharged, unlike other batteries they age faster when discharged) it can last a little longer than otherwise. But they're often only good for 50-100 complete discharge cycles from full to empty, and you'll only get about half the capacity it says.
Some people have wired up their own batteries from other types of battery packs that can be a little cheaper, but it's something you need some experience and knowledge to safely do, and will take quite a bit of reading and research to learn the things you'd need to know, to do this without much risk of fire. I started out not knowing a thing about batteries, and destroyed a number of them (thankfully no fires from them) in the process of learning what I know now, and watching others destroy theirs (too often *with* fires, some of which destroyed their bikes, or even burned up their homes!) here on the forum and elsewhere as they learned, teaching me even more.
Whatever battery you get, with an 1800w kit, if you use 48v, that's going to require almost 40A from the battery anytime you're actually using that 1800w. So you need a battery that can supply 40A, and that's going to take a good one. If you can't get a good one, you'll need a big one so the current is shared between more parallel cells (say, 13s8p or 14s8p at least, more "p" = better for both current and capacity).