Tfisher309 said:
I have a 50ah battery that can supply 150a continuous and 300a peak and a controller that can handle 120a continuous and 200a peak.
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My battery maker suggested a 150a circuit breaker between the battey and controller. This sounds too small. Shouldn't it be at least 200a?
Depends on the breaker. Each one will be rated for a certain amount of overload current for a certain amount of time (usually a curve on a chart). A breaker wont' pop instantly once it goes past it's rated current; it takes time for this to happen, so if your controller peak currents are short enough, it will not pop the breaker. But if there is a chance the peaks could last longer than the breaker "timeout" and pop while you're trying to accelerate in traffic, it could leave you with no power to do anything and you're left at the mercy of the rest of traffic, which could have unfortunate results. Or other things may happen to pop the breaker, depending on your riding conditions, terrain, etc.
The main thing is to ensure your battery and wiring isn't damaged by overcurrent--if the battery has a BMS it should shutdown it's output if current exceeds it's maximum for longer than it is capable of. The breaker is there in case that doesn't work or the load is beyond what it or the wiring can handle.
I have a 72v dc to 12v dc converter for my lights. Can I run my lights directly off of this converter or should I have a small 12v battery between the converter and lights?
Depends on the converter, and your specific needs.
If the converter is rated for more current than you will ever need for the lights, then it will run them fine. If you have incandescent lights, it may take significantly more current at turn-on than during running, so you may need twice the converter capability than with all LED lights, for instance.
Note that if you're using automotive lighting, your converter needs to be 13.6v nominal output to provide the same voltage the lights are actually intended to run on. (they'll be noticeably dimmer at only 12v). Most automotive lighting will run on up to about 14.4-15v safely, sometimes higher, but 13.6 is the nominal voltage of the typical car lighting / starter "12v" battery.
If you're going to use a battery, too, it should be of similar voltage. A 4s LiFePO4 works well for this (but a 4s non-LiFePO4 doesn't).
To have a battery between them, if the battery is to be charged by the converter under any conditions, ever, the converter must be a CC/CV type (like an LED PSU, like the Meanwell HLG or ELG series, etc), or it will shutdown (or fail) when connected to the battery if the battery is below the converter's output voltage. So if the battery is there so that if the converter shuts off (like your traction battery runs out but you still want lights working), then if the battery drains down significantly lower than the converter's voltage, the converter has to supply a lot more current than normal to try to charge it, so if it doesn't operate like a charger does (most can't) it will just shutdown at best, until the excessive load (battery) is removed.
To avoid that and just use a plain converter you'd need to recharge the battery separately before powering the system back on, under the conditions above.