I don't know of anything specifically to do that; there are plenty of analog multiplexers that can be set to cycle thru the inputs or be addressed by an MCU, but haven't seen one that would "know" which input was in a specific state to then latch to that one.I'm thinking it might be best to try and trick the BMS a bit. I need to monitor 7 batteries, if any one of them goes high the load needs switching off.
A simple pic with a/d on it could monitor all the batteries and the set a digital potentiometer to the average, if one starts to run away just feed the BMS that temperature via the digi pot then the BMS will always see the hottest battery if there's a problem?
Do you think that would work on?
Is there anything that does that available?
If not I'll have to make it, I can't afford a
Cheers Geoff
You could use a JBD contactor based BMS. Then use a contactor capable of whatever current is required.My inverters are 5kw each X3 so a 15kw system.
I don't expect to draw much more than a 10kw peak, but each inverter 'can' draw a maximum of 100A at 48 volts.
The BMS is a daly 300A BMS, which I thought could handle 300A peak 150A constant, I'm running quite a few motors on this, the bigger ones are all on inverter drives so fairly soft to start.
Anyone suggest a BMS that would be suitable?
Can't safely run them in parallel because if one doesn't turn off the other one takes all the current, bypassing the one that's off and then overloading.I had wondered about using 2 in parallel ?
If you need to pass high current both ways then you probably will have to use a contactor type; all the FET based units I know of use far fewer FETs (or lower capability ones) on the charge port, whether or not they are common or separate C & D ports (because most cells used only handle a small proportion of charge current vs discharge).It will be a bit different to a ev BMS as I also plan for up to 15kw solar input so ideally need 300A either way, I think this makes it difficult for a contactor BMS as charge and discharge port are shared?
Your ideas look good.View attachment 343848View attachment 343847View attachment 343845View attachment 343846
It's arrived!
I've ordered a 500A contactor that can break 2000A at I think 900v so should be up to the job, looks like should be quite easy to bypass the contactor on board give me a more heavy duty setup.
Got me thinking I could use some relays on the contactor coil line to give me a way of building in a few fail safes. Emergency stop button for one, battery over temperature as this bms only has sensors for 2 batteries.
How much current can I push into these batteries CATL li ion 190aH (2.8345kwh/3.7v/4s) 2x 14s which gives me 380aH total.
My chargers can top out at 300A (solar/generator) but there will always be a load , I'm stood by it charging for first time at 120A and a bit nervous! Everything is nice and cool .
At the moment I have charge voltage at 58v (4.14) is this about right or should i drop it.
Protection at 4.2v
Discharge protection at 3v.
Am I near right?
Thanks Geoff
It should only be 2-4 watts, if it's done correctly.because I'm always thinking about the constant power draw required to keep the contactor coil activated
Considering that they came from a car I would say at least 1C or 380A. You can probably charge with higher currents. The limiting factor would be heat, inside the EV they were most likely water cooled.How much current can I push into these batteries CATL li ion 190aH (2.8345kwh/3.7v/4s) 2x 14s which gives me 380aH total.