Battery Minder Tender Maintainer charge/discharge behavior

For 2 weeks, you don't need anything. Just make sure the lights are off and all of the interior lighting is also off. I left my 04 for almost 4 weeks and had no problems starting it when I got back.

 

Are you sure its *discharging* or just ramping back to 0.15 amp?

My VDC Battery Minders will charge at around 1 amp max. Once float charge is acheived, they usually go down to 20 mA or less. The maintenance mode will introduce high frequency pulses to desulfate the battery

 

First off, the "Prius Battery" in this case is nothing different than any other car has. Think of it as a starter battery that doesn't have the same current demands put on it. We're talking about the Aux battery here - and the only thing "different" about the Prius is the traction battery which we're not talking about in this thread.

That said... I've done quite a bit of research on chargers/maintainers. And I've found a product that I'm thrilled with. Silly to have to mention that I have no ties to this company, etc... but I guess I should. Excuse the "Extreme" name... here's the product:
XC Xtreme Chargers | Xtreme Charge

This is the company that makes them:
http://www.pulsetech.net/

As you can imagine, our military has quit a few vehicles that sit around waiting for somebody to attack us. MANY of them are sitting around on these chargers. This product was created for that use, and the military is their biggest customer. And the great news to me is that this tech is now being built into cars at the OEM level. It turns out that just throwing a "dumb" charge into a lead battery only gets you so far. But anyway... you can research any of that. My experience with these chargers (I have three of them) is fantastic.

The Xtremecharge unit doesn't just keep your battery topped up, the charger makes them better with use. And that's not just ad copy. I have confirmed it several times. While I can't tell if the batteries in my EV or Prius have improved, I can certainly tell that the batteries in my lawn equipment have! I had a 12V lead battery in my string trimmer that would run the thing for about 10 minutes max. This battery was toast. After two weeks on the charger, it ran for 25 minutes - enough to complete my whole lawn - and it wasn't dead. The charger that I've used on that battery has now paid for itself. I'm doing the same for my electric mower with similar results.

And for those of you with Optima batteries - good news. These units are actually optimized for Optima charging/maintaining. The company determined that Optimas were the hardest batteries to treat correctly, and they focussed on those. Turns out that what's good for the Optimas is also great for every other type of lead acid battery.

So now that I sound like an infomercial, I'll shut up. I don't usually brag on a particular product like this - but truly I'm sold on the Xtreme charger stuff. I have pigtails on the Prius and EV battery, so I can just plug the charger in whenever it is parked. As the Prius is so rarely driven (and the battery is so hard to get to) this has been VERY handy.

 

Well, that's odd behavior. I have no idea if it will actually harm a 12vdc battery. My VDC Battery Minders do NOT behave that way

 

Sounds like my Battery Minders. These sort of chargers really do work, I had much better battery performance with the tractor and work truck at my hobby farm

 

I've used Battery Minders. They work great to keep the battery from sulfating and discharging. The Xtreme Chargers do more, though. Where the Minders slow the aging of the batteries, the Xtreme makes them (at least in some significant ways) younger!

Every time I read my posts here, I sound like a shill. Fortunately I've been around long enough for folks to realize that's probably not true.

 

I should plug myself into one. I would love to rejuvinate my tired, cranky, middle-aged body

 

If you use a quality DMM - eg a Fluke that is generally accepted as having calibrated results - and are reading 12 vdc, that is essentially dead. With new batteries that I have left on the VDC until they had a week or so of desulfation applied, then disconnected 48 hours to allow surface charge to go away, I recorded 12.9-13.1 vdc

It wouldn't hurt to desulfate a battery like yours. Don't expect magic though, sounds like that battery has had it.

 

Yeah, what Jay said. Measuring without load is a bit sketchy. When you plug in the Xtreme, the first thing it does is test the battery under load to determine if it can help it. I've brought back some surprisingly dead batteries now. Stuff that was going to the recyclers, and has now been put back into service.

 

First,

2 weeks is not enough to worry about, assuming you battery is in good health. That said two things happen. The first is that lead/acid batteries do have a self discharge that can range as high as ~1-2% per day. Any flooded lead acid battery that is left un-recharged below bout 80% state of charge will be damaged quickly due to lead sulphate hardening on the plates, permanently reducing capacity. In the solar business we suggest that batteries never be left more than about 3 days under 80%.

Second,, and perhaps more important, the Prius 12vdc battery is subject to considerable "Phantom loads", including smart key, radio/stereo memory, alarm system etc. The best suggestion is to turn the smart key off which will reduce this parasitic drain.

More than two weeks and I would consider small ~2-5 watt 12 volt (nominal) solar panel charger. Most tiny battery minders with a 500mw panel are too small to even keep up with the parasitic loads, much less the self discharge. Panels larger than ~5 watts have the potential to over charge the small batttery, and shouldn't be used with out a charge controller to limit upper voltage.

As for the final voltage, a battery charge/charge controller will limit charging voltage to ~14.6 volts normally, for absorb voltage. Float voltage should be somewhat less. These absorb and float voltages are subject to some variation with temperature, and most solar applications have a temperature probe to adjust the voltage as the battery temp changes.

The biggest issue with batteries that are left on some charging system indefinitely is that they boil dry, exposing the plates and destroying the battery. If the charge current (amps) or voltage is too high this can happen quite quickly. A small 5 watt panel should keep the Prius battery up to snuff without risk forever,,, just check the water now and again.

For anyone that is interested,,,the following links have more information re: batteries than most of us wish to know:Deep Cycle Battery FAQ
Car and Deep Cycle Battery FAQ, Battery Manufacturers and Brand Names List, and

Icarus

 

Measuring battery voltage to gauge battery condition is largely a fools errand. The problem is that the only way to accurately gauge a batteries condition with voltage alone is to do it when the battery is at rest,, neither charging nor discharging, and ideally after the battery has sat ~24 hours at rest, difficult to do in most cases. Even then, voltage will only tell you part of the story. Because a battery will show 12.7 vdc (full charge) doesn't mean squat in terms of it's ability to deliver power from that battery.

Two best tests are a specific gravity test of the acid with a temperature corrected hydometer, testing every cell (once again at rest) followed by a load test with a specific load over a specific time, followed by another voltage/hydrometer test.

In the real world you know if your battery is going south if it won't hold a charge very long, but the trick is to anticipate failure so that you won't get stranded. In the Pv solar world we work hard to keep our batteries in known good conditions, since one bad cell in one battery can destroy the entire string in a few weeks,, or months at most. A $4000 battery bank can be reduced to scrap pretty quickly if it isn't tended to.

Icarus

 

I agree, but you have to start somewhere.

The best way to gauge battery health is to do a load test

 

I have been gone for 6 months and let my 2006 attached to a battery minder. I hope it keeps the starter batter charged. Can i expect any problems when i start the car next week? If it does start, i plan to keep it running for at least 30 minutes to get the rest of the electronics set or reset. Any comments?

 

If you properly hooked up the Battery Minder, and it was kept plugged in all the time, the 12 vdc battery should be fully charged and desulfated. The big NiMH traction battery may have lost some charge but should be ok

The gas engine may briefly run roughly, but usually with fuel injection, they will start right up. I would go for a 30 minute drive and then have the oil changed