Recent content by Davismltc

Mine is a 4s (12v) model: JBD-SP04S020-L4S-120A-B-U (v 1.0) The owner's manual they sent me says operating voltage is 14.6v max. I don't know about the 8s (24v) one.

I checked my JBD 120A rated BMS. Its FETs are NCEP40T17A rated at 40vdc (25*C) absolute max limit for drain-source voltage.

There's an Australian fellow on Youtube, "Offgrid garage", that has newer cells. He found running an active balancer all the time was causing more imbalance, as compared to only running one at the upper knee. I think it could also depend on how low the battery is utilized before recharging...

I ended up taking @crossy 's proposed solution a bit further. I had some PC boards made to make an easy build of it and added a couple more features. A miniature SSR can provide control to an active cell balancer at the upper knee of the cell charging graph. ON at (~3.40v/cell) and OFF at...

That's awesome! I only saw the specs on battery hookup. What's the power draw for the combined units together (e.g. the controller relay and contactor together)?

I did find DC-DC buck converters on eBay @ 2 for ~ $1.00 and plan to build the initial circuit with one of those, rather than a zener supply. I don't intend to have battery supply voltage drop below 12v, but will test it down to 10v. Input 3.2v~40v Output 1.25~30v Current 3A (max)

The contactor specs show this as a normally open contactor with relay coil resistance of 3.14 ohms. If the battery voltage is 13.8v for example, wouldn't this be drawing about 4.4 amps continuously to keep the contactor closed during normal battery charging/usage?

You might have a look at Crossy's solution to battery protection at post #191.

Thank you for the offer of assistance. I'll let you know if I need help. I agree it would be redundant and unnecessary to add this to any system if devices never failed. The sad truth is devices fail, and the results can be catastrophic.

I have a JBD BMS and was concerned that it would be subject to the same SCC failure. The specs on the JBD are pretty limited, and my goal is the same as the subject matter of this thread... a failure in the MPPT solar charge controller causing a BMS failure followed by battery failure. The...

What I'm finding on the crappy simulator is that for the Schmitt-trigger resistor thresholds to work at all, the op amp supply and its non-inverting input voltage divider both need to be sourced from the same voltage (e.g 9.1v). If I supply the op amp with battery voltage (14v) and connect the...

Thank you for the advice. I really appreciate it.

That'll be my next step. I don't have a lot of resistor values, etc., so the sim helps me narrow down what I need to acquire. Is it likely that the 7.5v 3.9mA output of the op amp is sufficient to turn on the SSR and allow decent PV panel current to flow? I've never used an SSR before. I...

I have a much smaller solar system on my camper. It has a single 4s LiFePO4 battery and two PV panels, with each panel controlled by its own SCC. I took a stab at modifying Crossy's schematic in the Falstad simulator for the lower voltages in my system. I'm just learning about electronics, so...

Thanks!! The relay in the picture has the name spelled "FOETK"... LOL