toxictoad said:
The two wires that come from the lock are the same thickness as the as the wires that connect to the charging socket and also the power out. They then connect to thinner wires and to the bms/battery.
If any part of the wiring is thin, then there is no high current in it, as the thinnest stuff in a series connection determines what all of it can handle.
So you could just cut the thin wires and connect them together and it would permanently keep the BMS on. The disadvantage of doing this, rather than having a switch there, is that the output is *always* live, and you have no way to turn it off to work on it, and you may need a precharge circuit to connect it up to your controller without having sparks happen. If you put a switch on it, then you can turn it off for connections and disconnections, and storage. Also a slight extra layer of security, I suppose.
I don't know if the key is the connector but I'll try and get into it and see what's going on.
I don't know what you mean by "key is the connector"?
I asked about the fuse because I've watched a dozen or more videos watching people make batteries and none of them added a fuse.
That's because most people building stuff (of any kind, for anything) do it the cheapest easiest way they can, *and* they assume they already know everything there is to know about what they're building and what could possibly go wrong, ever.
This is hardly ever true. :lol:
Stuff you buy from a manufacturer, if that manufacturer follows good practice (or has scared lawyers) will use safety devices to prevent really serious disasters. This is really the only reason to even use a BMS--to prevent serious problems leading to fires, from overcharging or overdischarging cells in a pack to the point that they simply can't handle it anymore. (the conditions leading to that are numerous, which is why a BMS can be complicated).
A fuse is there to protect the pack from *external* problems, like say if the main wires from the pack's output run underneat it and it bounces on them all day long...eventually wearing thru the insulation and allowing them to touch each other. A fuse would blow and prevent current flwoing thru the wires at the short from heating the wires until the insultion catches on fire, and then the cell wrapings, and then the cells, and then your house, etc.
Lots of possible things that could cause that general chain of events...but a fuse as close to one of the battery outputs as possible (mine are right at the actual output terminal of the most positive cell, in the packs on my trike), will stop all of those things. It can't stop a problem inside the pack...but it will stop one from outside it. A circuit breaker can also do this, but is much larger and more complex and more expensive. (it has other advantages to make up for this, but only if you need them).
As the wires to the charging socket will be cut, do I have to reconnect the same socket? Is it safe to remove the socket connector from the battery and the charger and use XT30 connectors to charge it?
You can use any connector you want to...but you must make absolutely sure you retain the same polarity, or you can instantly destroy your charger, and potentially your BMS. Whatever connector you use, I reocmmend one that has built-in strain relief, especially if it is a solder-type connector instead of a crimped one, because soldered wires eventually break at the point where the solder ends and the flexible wire begins. Also, without strain relief, pulling the connectors apart almost always involves pulling on the wires at least a little (even people that say they never do that...still do that
).
As far as I can tell it is only silicone that's holding it in place and not a lot of it so I'll go easy on removing what I can.
You can only see what's on the end. But if it is like some packs that have been disassembled and pictured on ES, the glue was smeared all over the cellls before they were slid into the casing...so they are then thoroughly glued into place and literlaly can't be removed without cutting up the case or damaging the cells (or both).
I have no idea about what batteries are in there...I only thought 18650's were used :?
There are a number of kinds of cells used in ebike packs. Some are pouches, some are prismatic (little boxes), some are cylindrical, some are other shapes.
Generally anything that's from cylindrical cells is obvious, by the shape underneath the shrink wrap. If you can't feel them under there (presumably you've got an idea what they'd feel like under a wrapping), it's probably something that needs the metal casing to keep the cell integrity.
I have sent a message to the seller so I'll wait a while before doing anything more.
THe seller probably doesn't have a clue, and will tell you whatever you want to hear.
They buy a box with stuff in it that costs a certain amont, and they charge enough to make a profit in selling it. The profit is the only part they care about, so it makes no difference to them what's inside the box, and so they don't have any understanding of what the differences are in any of the stuff that might be in it. (regardless of waht the "box" is--battery, controler, light, t-shirt, rainbows and unicorns, etc etc). A very very very few sellers might have some idea what's inside, but almost no seller of any product cares...and even if there's someone at the ocmpany that does care, and know, they are almost certainly not the people answering questions from their websites and phone numbers and emails.
They're unlikely to just tell you they don't know, however...so like most salespeople, they'll make something up that sounds good...or just parrot back to you what you said.
Aplogies if I sound pessimistic...but I've been around a while, and have seen quite a lot of stuff go wrong (made some of it happen myself, mostly just analysed what ahppened to others). And I have gotten fairly decent at failure analysis of some types of systems, based on theory and on actual observed failures over the decades. :/
