Comments on: Batteries lead an isolated life

By: Rod

Rod — Thu, 26 Mar 2009 22:42:17 +0000

have you considered the impact of the drop out voltage on the longevity of the primary battery?
I’ve seen anything from 12.5V to 12V for the drop out voltage. At 12V the SOC is anything from 10% to 50% depending upon the battery type and which set of figures you believe. The cycle life drops dramatically the deeper the discharge. I suppose it then becomes a cost/benefit calculation between battery life / depth of discharge and size of the battery bank.

PS had to start my vehicle today but I checked before I started it, the isolator was still activated over 40 hours after I last shut the vehicle down. That’s a fair bit of wasted power keeping a solenoid active.

By: me2

me2 — Thu, 26 Mar 2009 22:11:02 +0000

In regard to the isolator parasitic current – this is why many manufacturers use several small relays in parallel (Traxide, TJM etc) rather than the single large relay like Redarc. It is a significant draw on it’s own.

By: Rod

Rod — Thu, 26 Mar 2009 02:04:46 +0000

I’ve been making some observations regarding my installation with a voltage sensitive isolator.
The power consumed by the solenoid is significant. mine measured at ~0.8A. Not a problem when the alternator is running but if you have a low drop out voltage, say 12.5V, and not much of a load and/or a lrage capacity of battery then it can take a significant period of time to discharge to 12.5V.
In my case, as I write, it has been nearly 24 hours since the engine stopped and the solenoid is still operational. ~19Ah of load just keeping the solenoid active.
Two possible solutions, increase the drop out voltage to, say, 12.8V or make the solenoid driver smarter and reduce the holding current once it has actuated.

By: Scott

Scott — Sun, 06 Jan 2008 07:32:16 +0000

problem solved