I need a linear shunt regulator to protect a battery from over voltage from a charger.
It is to blow a 3 amp fuse if the charger is at 14.4 volts and feeding more than 3 amps.
Start regulating at 14.2 to 14.4 volts, handle 3 amps at 14.4 volts = 44 W continuous but more likely the fuse will blow.
I would prefer a surge current capability of >50 amps. There is a lot of energy in the battery.
I can add an external power transistor/FET/MOSFET if necessary.
Any suggestions.
My SCR crowbar is getting way to complicated. A simple suggestion would be welcome but is not the reason for this forum.
(The charger is a switcher being fed with 170 v DC hence my concern about destroying an expensive LiFePO4 battery)
Welcome to the Digi-Key TechForum bunge.pjp!
I do not see a Linear Shunt Regulator, that matches, in our system.
Maybe one of the engineers can add to this post, with some recommendations.
It’s not entirely clear what the precise objective is here; is this to be part of a battery-mounted protection/management system or an add-on to the charger circuit? Strictly for faulty-charger protection or serving double duty as a discharge short protection? Approaches may vary depending, and on what else is involved.
That said, I’d suggest stepping back with a beverage and doing some critical thinking about how you’ve framed the problem; you started by asking for a regulator to protect a battery from a faulty charger, which seems an unnecessary complication; under normal circumstances the regulatin’ is going to be done by the charger, and under fault conditions things are likely to go very rapidly into the weeds, rather than lingering on the edge of the road for any length of time.
With that in mind, there’s a lot of purpose-built battery protection ICs on the market, which could probably simplify things for you. If you’re worried about faults exceeding the maximums of those ICs, their use would probably widen the operating window for an auxiliary crowbar circuit to about 15v, rather than 0.2.
Thanks for the reply.
I was looking for a shunt regulator with 14.4 volt output and at least 10 amp capacity. It would not be normally active.
I could not find any shunt regulators searching DigiKey. Obviously I used the wrong words. The last time I used a shunt regulator was in the '80s (last century)
This is why a simple SCR crowbar does not work. It blows a 3 amp fuse without getting into details.
It is the turn on voltage using a mechanical switch (you know, ON/OFF toggle switch,with a snubber across the contacts) of my LiFePO4 “Smart Battery” which has outsmarted me.
Purple trace, ignore the yellow. The 20 volts fires the crowbar. A Gel battery works fine.
Clamping that ringing may destroy the battery. I need to talk to the manufacturer.
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I was trying to keep it simple. The charging voltage is 200 volts DC coming down 300ft of twisted pair to an ROV. About 30 volts will be lost to resistance. (maybe 400Hz AC and rectified if I can find the components and have the space)
These smart batteries can be killed with overvoltage. I don’t trust the step down charging regulator.
I doubt if there is anything commercial that will do this but I can adapt a shunt regulator, or make one.
This century, shunt (and series) regulators are usually just referred to as linear voltage regulators, or just linear regulators (as opposed to switching regulators).
