Protecting a battery charging voltage regulator from burnout when engine run w/o battery

[wh500special 2,168]

It's common for a battery charging voltage regulator/rectifier (RR) to burn out quickly if an engine is run without a battery in place.  Aside from disconnecting the AC input to the RR before running the engine w/o a battery, is there a way to "trick" the RR into thinking there is a charged battery present thus blocking the damage that may result? 

 

This for the little sealed RR units like we have on new small engines.

 

I don't want to put a load in place of the battery, instead I'd rather the RR think it's looking at a charged battery so it cuts back the current it's trying to send.

 

I am assuming that an appropriately sized capacitor between the battery leads could charge up to the output voltage  and then look like a battery to the RR.  But are there other/better/common ways to do this?

 

I'm guessing there is someone who has done something like this here.

 

Steve

[wh500special 2,168]

The overwhelming response to this indicates that there probably isn't a lot of interest in this problem or there weren't any ideas, but I did find a solution so am updating in case anyone is losing sleep over this.  I certainly was.

 

There are prepackaged protection modules available to keep the magic smoke inside the rectifier diodes when the battery is disconnected with the engine running:

 

Sterling APD

 

Balmar APM

 

When the battery is disconnected the voltage in the charging circuit will rapidly rise and the current will follow.  This smokes the rectifier diodes (usually).  When it hits a breakthrough voltage of about 16 volts (on a 12V system) a gate connects that clamps the voltage at 16V - thus limiting the current - and dissipates a little power to ground.  i don't know what's inside these modules but it's probably more sophisticated and predictable than my conceptual zener diode, capacitor, and resistor.  Or it could be something more sophisticated.

 

Anyway, I ordered a couple of these for my project for testing and anticipate them fixing my problem.  I'll know in a few months.

 

This question makes me wonder whatever happened to Chuck @Save Old Iron ? 

 

Steve

Edited January 9 by wh500special

[kpinnc 11,985]

17 hours ago, wh500special said:

This question makes me wonder whatever happened to Chuck @Save Old Iron ? 

 

 

Good point. He certainly knew electronic principles well enough to explain it in simple terms. 

 

Hope he is doing well!

[wh500special 2,168]

I doubt anyone was really waiting for an update on this, but thought I should close the loop here…

 

Purchased a few of the Sterling APDs (great customer service from the company owner/engineer in the UK) and did some experimenting on my test engines…start the engine, disconnect the battery, let it run for an hour under various loads and environmental conditions.  Shut down and reconnect battery then restart.  Check charging system function…

 

Success!   The protection modules did their job and the charging system remains functional.  Control samples run w/o the protection circuit suffered RR failure about half the time.  
 

Anyway, if you are updating to a lithium battery and are worried that a BMS disconnect might smoke your regulator it looks like these gizmos can save it.  
 

It appears that they clamp the voltage to a safe level. And they also give off one helluva spark when making the initial connection. Both of those things suggest a sizable capacitor lives in there…

 

Steve