# DC current limiter

Discussion in 'Misc Electronics' started by Kamus of Kadizhar, Jan 22, 2004.

Is there a currrent limiter that can limit 12VDC to < 60 amps?

I have a situation with a deep cycle lead-acid battery where the 60 amp
breaker trips when charging. I'd like to limit the current to reasonable
levels and have continuous charging rather than spikes of > 60 amp
current, breaker trips, resets, spikes, etc....

--Kamus

2. ### Thomas C. SefranekGuest

You can make a current limiter for any current.
But, There is a voltage burden in doing so.

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3. ### Roger GtGuest

in message

What are the cause of the spikes, what is the peak
value (if known) and how long do they last?

This is part of an RV charging system. There is a 60A breaker followed by
a solenoid. When the engine is off, the solenoid is open and the starter
battery is isloated from the RV battery.

The problem comes in when the RV battery is depleted and you start the
engine to charge it. The solenoid closes and the engine starts to charge
teh RV battery. The current is greater than 60 A, so the breaker trips.
It resets autmatically, but trips again and again until a series of these
short cycles charges the battery enough so that less than 60 amps is
required for charging.

The problem is that some sort of breaker is needed; loads on RV batteries
can be 100A or greater for short times (like when using a microwave) and
you really want to isolate the car alternator from having to deal with

A battery isolator introduces a voltage drop (0.7 V or so) so I'm trying
to see if a current limiter of some sort exists that does not have a
current drop like that.

--Kamus

5. ### Thomas C. SefranekGuest

Current drop like what? Did you confuse the voltage drop for a current
drop?
Current limiting is inherently a voltage drop!

6. ### Watson A.Name - Watt Sun, Dark RemoverGuest

He could put a low resistance across the breaker, say about 1 ohm.
That would allow about a dozen amps to flow even when the breaker is
tripped. What would make a cheap low resistance? Well, how 'bout a
car headlamp? They're not expensive and they're easy to find. You
might consider going to a junkyard to buy a sockete for it.

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Fat finger typo.
Well, yes. But I guess I'm looking for some sort of "intelligent" current
limiter - one that gets out of the way if the current is less than 60 amps.

I've found a DC-DC charger that might work; I'll contact the manufacturer.

8. ### Ross MacGuest

There are battery isolators that have almost no drop..
Here is one you might consider... http://www.hellroaring.com/nodiode.htm
Just do a google search and you will find others such as MasterVolt....Happy
RVing.....Ross