Scootdan said:
My motors and controllers are rated at 96v but I read that many people run a little more than the ratings with no problem. Many ebike motors and controllers are 48v but run 52v batteries.
The latter is quite a different thing than the former, because most of the stuff for 48v (13s) has 75v-80v parts in it, at least, and some 100v parts. For 13s (or 14s) even the cheap stuff doesn't usually have parts intended for only a few volts above it's fully charged voltage (54v (or 58v)), though that has been the case when 14s was not common, where they might have 60v FETs and 63v caps.
Are your controllers rated at 96v maximum? Or are they rated for a 96v battery pack? If the former, then you should not exceed that, because if it has only 100v parts in it, pushing past those limits may cause failure at any time and will probably happen at the worst possible moment (because those usually happen when pushing things to their max).
If the latter, then if it's based on the typical Ii-ion pack 96v / 3.7v = 26s; I'm not sure how common that would be (24s *is* common, but that would be an 88v (or 89v) pack, 100.8v fully charged, and it would need better than 100v parts (probably 150v parts) to ensure it has margin to prevent sudden catastrophic failure.
If you run at the ragged edge of what something is rated for, you run a high risk of sudden catastrophic failure. With controllers, the most likely failure parts are the FETs, whcih tend to fail shorted, which will then be shorting out your motor phases, which turns the motor into a giant brake...if you happen to be going fast in traffic when this happens, best case you may skid out and crash into whatever is in front of you; worst case you could endo and flip or you could skid out and get run over by traffic from behind. In other situations there are probably equally bad consequences.
People do it...but you should understand the risks--it could kill you, or someone else (as unlikely as it is...it is still possible).
I found a 100v lithium battery
Is that 100v fully charged? Or a "100v" battery? The former is really an 88v battery, as above. If the latter, that would be a 27s or even 28s battery, which would actually be up to 118v full charge.
Using a pack that high a voltage on a 100v controller would probably destroy it pretty quickly, if not instantly.
but now I hear lipo is more power dense,
If yo umean RC Lipo, it might be, but it is also frequently zero-QC (with notoriously catastrophic failure modes) and has a much shorter lifespan especially when used hard. Often rated much higher than it can actually handle realistically ("100c" for what might really be a 10c or 20c max real capability, for instance).
Your battery is the heart of your whole rig. If you don't build the system around the battery and it's capabilities, then you need to figure out what you want teh system to do for you, and what that system will take in power to do that. Then you should build a battery that is more than capable of supplying that power, with a good margin over that to account for aging over time, so it won't only be able to do the job you need when you first build it, and can continue doing it for the life of the vehicle.
Hopefully I can ride my big scooter as a docile under powered puppy until I see what kind of juice it might need,
Use the motor simulator at ebikes.ca to see what you actually need, in order to do the job you want this to do for you. Then you can figure out what it will need without having to buy controllers and batteries and such that don't do what you want over and over again until you eventually get something that does. Will save you a lot of time and money.
Hopefully I can get it some kind of street legal.
YOu'll have to check your locality's laws on DIY vehicles, and then on whatever relevant class it is covered by (if any--it may be of a type of vehicle, because of crappy legal wording and descriptions in the laws, that simply can't be allowed on the roads at all, or even be flat out illegal...for instance, there are places that recumbent bikes are not legally bicycles because the definition there specifies one must ride astride a saddle...and the 'bents typically don't use saddles...there are other such instances of wording that makes some commonly used things not legally what they actually are, and some actually made illegal by other parts of the wording).
I'd recommend doing this before you go further, so you don't end up with a ticket and your creation siezed / impounded.
