Powerwerx 12v HVD/LVD/Timer for lead acid and lifepo4

PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
This review is for the 12v Powerwerx ITS-12 and APS-12 timer / lvd's.

Essentially both are designed for emergency vehicle use to prevent a load from killing a battery when the ignition is off. They are available directly, or sometimes through amateur / ham radio outlets. While it is designed specifically for lead-acid, the timer actually makes it very convenient for lifepo4, which is the reason I got it... read on...

The ITS-12 (which I own and tested), incorporates an HVD of 16v, a selectable LVD of either 11.0 or 11.4v, and additionally has a voltage sensing timer, which can vary from 2 minutes to 12 hours, once the battery drops to 12.7v. It handles 35A continuous and is potted, aside from the connectors. So you'll either time out, or hit the LVD first.

NOTE: Some other units of the ITS-12 have an LVD spec of 10.9 to 11.3v, so you may want to verify which series in the line you are getting if going low to 10.9v is important to you. My manual was listed with a date of 3/7/2013, but perhaps there are two different models or a model update?

The APS-12 is similar, although there is no LVD, and handles only 25A. I have not personally tested this one. Your lvd is just the timer.

Neither requires any "sense" wiring. Just a simple two-terminal in and two-terminal output. There is an AUX connector if you need to override the timer or lvd for some reason. I'm not using that. Two led's show the current status of the switch. As measured on my Fluke multimeter, this protection costs me about 150ma in normal use. I did not verify the stated 4-5ma under standby.

The timer/lvd settings are done via a rotary switch, which was a real pleasure compared to some other switches I've tried that required some funky programming by tapping jumpers and counting led flashes, or using magnetic swipes.

So yes it seems to work, although I have NOT tried to force a 16v shutdown, nor subjected my battery to an lvd event of 11.4v. Perhaps I'll find a junker and use that. I was more interested in the timer shut off.

While not specifically designed for lifepo4, we can put the timer to great use. The existing high and low voltage disconnects are too extreme for lifepo4 - although it is better than nothing - some damage will occur if you rely on the disconnects - timer to the rescue! What I'm talking about here are large prismatic 4S packs, consisting of cells from GBS, Winston, CALB, Hi-Power and the like.

What is really great is the timer that starts at 12.7v, which is just a smidgen under 80% DOD. Once it hits, the green light flashes, and your timer setting clocks out, and the unit turns off. However, you will most likely want to consider adjusting the timer from the default of 2 minutes to possibly 15 minutes depending on how much current you are pulling.

Example: With my 20ah GBS battery and a load of about 0.075C (1.5A), the timer would duly start near 12.71v (green led flashes) and eventually times out, but the batteries revived after a short rest to about 12.77v, unit fires back up, and the timeout cycle would begin again. Each time as more capacity is diminished, the off interval lengths increased, about 10 times! I think I'll be changing the timeout to 15 minutes under this load to help keep it from waking up and staying shut off - which it eventually did. Obviously this will not be a problem if I'm around with all the gear shutting off abruptly as an alarm. :)

Update *** I have since gone back to the minimum of 2 minutes. At 15 minutes, the cells revived enough to cause 3 consecutive wakeup periods resulting in a larger discharge (45 minutes additional) rather than having the many multiple, but smaller time periods of activity before the cells no longer revived enough to cause a timer reset. ***

So thumbs up for lifepo4 with the timer setting. While not perfect for lifepo4, it is easy to wire and configure, and will do the job of an lvd based on time just fine. The extremely low lvd in the ITS-12 designed for lead is better than nothing I guess, but you don't want to go down that far anyway. Highly recommended for portable or light-duty use and for those like me who don't need to rely on a full-bore bms system.

Solar hint for newcomers - just because a lifepo4 can go gown to 80% DOD to get the rated cycles from them, does NOT mean you should design your system around that. Stick to 50% just like with lead-acid. That way you'll have some built in autonomy and headroom for unexpected loads or bad weather. The Powerwerx switch should not be a dummy-light, but a backup against catastrophic accidental discharge.
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