I need to protect my 48V batteries from too deep a discharge. However, the batteries also need to supply more than 100A at peak. Can I use two use Smart Battery Protect 48V-100A in parallel (the output connecting to my load)? Thanks.
asked
Two Battery Protectors in Parallel
Using a BP-220 is the more straightforward approach.
edit: oops. 220 not viable because of voltage limits. Might need to think about a heavy duty VSR if your peak loading is sustained > 30seconds.
See following thread
for a bit more info on associated risks of running 2 units in parallel
What kind of loads are you supplying?
I'm reconfiguring my battery packs from 24V to 48V to drive a larger inverter. 6kW. My battery pack will range from 40V at 10% to 48.8V at 100%. the 48V-100A will get me 4000W to 4880W so I'm significantly short if I want to run at capacity, or even fairly close.
So, 30kWh lithium battery back will be connected to the inverter. It is the only load it will be carrying. The charging circuit does not go through the battery protects; they are used purely as extra insurance the battery are never discharged below 40V.
Thanks,
Dale.
Hi @drsulak
Inverters, or other capacitive loads should not be connected to a Battery Protect. they should be switched by remote connection.
Connecting an inverter to a battery needs pre-charging, and switching without pre-charge results in -very- high current, easily 10x the normal maximum load of the inverter.
Therefore inverters should be hard-wired (with appropriate fusing) to the batteries. or if they really have to be disconnected, a pre-charge circuit is to be used.
Yes, I know. I do the pre-charging, and a remote soft start. I currently have a 24V system with a single BP220. I also have sensors, and other interfaces that give me real time and web-accessible data. The system has been running for six months; mostly charging my cars multiple times a day (L1 charger, though), but also running my fridge as a test. The signle BP220 has worked perfectly. But now it's time to grow capacity. Can I run two 48V-100A battery protects in parallel?
I get the EE stuff. I regularly work with switching thousands of amps. But I want to get this project done without spend too much time building something from the component level, if I can avoid it. So, assuming a well behaved system where I am supplying power to a well behaved load, can I connect two in parallel, *or* are the battery protects not matched well enough such that current flowing through each will not be split sufficiently and so I need to go with a different solution for protecting my batteries at the higher current?
Thanks.
Dale.
Victron didn't spec them to operate in parallel, so you may not get the answer you seek from the source.
My guess is that you are going to need to fuse both BPs anyway, in order to prevent a cascade or timing failure from causing the second BP to fail short.
Once you add fuses, I suspect any variance will be noise and the current will be relatively balanced.
You should really consider just using a contactor. It will make the system simpler and more reliable, and you will have fewer components.
It's still unclear to me why you can't just program your inverters to shut down at low V. They already have the appropriate hardware inside to do this, I should hope. You state they're the only thing you're going to protect on this circuit.
I wouldn't do it. Use a contactor instead. Plan on a precharge mechanism for the times when you need to start the battery back up. (Use a lightbulb, if you like.)
BP was designed for simple DC loads with no inrush component. It also fails closed, which is the exact opposite of what you want.
