Battery Maintainer - Good/Bad/Ugly?

[Fallon]

You need a charge controller if you are using a solar panel that is permantly mounted. A low wattage panel will eventually end up killing your battery by overcharging it. It will take a while but it will hasten it's demise.

I've been happy with my BatteryMINDER on my beater infrequently used farm truck. I ended up getting a small tissue box sized panel to use instead of the big panel I got with the BatteryMINDER. The big panel was just to big & needed to be hard mounted. The small one is just suction cupped inside the windshield out of the way & portable if need be.

 

[1stDeuce]

Fallon, I won't say you're wrong about the charge controller, but it does not align with my experience...
A low wattage panel on a larger battery isn't capable of raising battery voltage to the point of needing to regulate it with a charge controller. You can put one on, and it'll keep the panel from drawing down the battery at night, but a small panel won't be able to raise the battery voltage to the point where the charge controller needs to regulate it. So in that case, a diode is much cheaper, and will do the same thing.

If your panel setup can can put out more than ~1 amp, or lots more, like with a solar power setup, where you're running the battery down and re-charging every day, then yes, a charge controller is necessary. But for a very small (10w or less for a normal car-sized battery) panels, it's not needed, as the panel isn't powerful enough to raise voltage to the point of harming the battery. (Or even to a "float" voltage, in the case of a 10W panel on a normal size CUT battery.) This is ONLY true for small panels on large batteries.

You can find formulas that tell when to use a charge controller online. They're usually published by places selling charge controllers, so they're very much biased toward needing one... They're based on Amp Hour capacity of the battery divided by panel max power amperage, and set a threshold number, below which you need a controller, and above which you're fine. My experience has been that using panel max power is VERY optimistic for a flat mounted panel, and where they set the threshold at about 200, I've found that the reality is that it should be more like 80-100.

To illustrate, I have a ~25Ah battery with a 5W (.3a max output) panel. It's at 83 by the online formula, so I should definitely buy a charge controller... But I've never seen voltage over about 13.4, even in the summer, in mid-afternoon when it's as high as it'll get... And I live in NM. A charge controller wouldn't do anything even if I put one on.

Unfortunately, many in the world of solar power still do calculations like the solar setup is capable of charging 24/7, and it's not, and I think that's where the ultra-conservative number of 200 comes from... If the panel was capable of getting to its max amperage, which it's really not going to ever hit, and charging 24/7, I can see the threshold going up, possibly to around 200 even. But solar power isn't 24/7, max power current never happens, and I'm not in the business of selling charge controllers.

 

[Fallon]

I killed a few jetski batteries with a 5 watt panel & no controller. They lasted less than 4-6 months until I stopped using the panel. Then I was getting 2+ years out of them.

Heard of several others with similar results.

 

[Snowback]

Y'all are awesome. Thanks for this terrific feedback from everyone. Very helpful and gives me great ideas.

Sorry about not being abundantly clear on the solar deal. Comments above are also correct on GPS as a tracking device in case the tractor decides to "walk" away...

Interestingly, it's that GPS unit that sends me the helpful reminders via email that battery voltage has dropped past a certain hurdle that can be set... That's very thoughtful, eh? ;-)

 

[1stDeuce]

I killed a few jetski batteries with a 5 watt panel & no controller. They lasted less than 4-6 months until I stopped using the panel. Then I was getting 2+ years out of them.

Heard of several others with similar results.

Yup. A Jetski battery is TINY. It's half the lawnmower battery I'm running with a 5W panel. But we're not talking about a Jetski, and battery size makes a HUGE difference to this conversation. I'm standing by what I said, but it's pretty easy to check voltage on a sunny day. If it's higher than 13.6 at 2 in the afternoon, then put a charge controller on it. I don't think that will be the case at all.


Snowback: The voltage reminder is better than nothing, but that's hard on the battery for sure. If you're worried about cooking the battery, go with a smaller 5W panel. Either way, it'll more than keep up with your GPS draw.

 

[Fallon]

The battery in my ski was the same size as in my riding mower. The battery in my buddies ski was significantly larger.

 

[Travelover]

This is a pretty silly argument. Duece is right that you don't need a controller for a 10 watt panel on a full sized battery, but if you are worried about it, just pop a few bucks and get one off eBay for $10 or so.

1A 2A 3A PWM Solar Panel Battery Regulator Charge Controller 12V/24V Auto | eBay

 

[s219]

There is a $20 Black & Decker battery maintainer at Amazon / Home Depot / Etc that was well reviewed across the internet, so I got two of them a few years ago. One has been in my generator shed for 3 years -- plugged in full time -- and continues to work well. The other I keep inside my shop to maintain any batteries I remove from boats/equipment in the off season. Generally Black & Decker stuff is garbage nowadays (their tools certainly are) but these battery maintainers got good reviews and I can confirm they work well.

Amazon.com: Black & Decker BM3B 6V and 12V Battery Charger / Maintainer: Automotive

 

[John_Mc]

Just posted this on another thread asking about solar chargers. BatteryMinder is a top-notch brand, and includes a desulfation circuit (which BatteryTender does not). They are not cheap, but they work very well. THey are smart chargers, and will not overcharge your battery:

Batteryminder makes some very good smart chargers which also include a desulfation circuit. I've never used their solar chargers, but have heard good things about them. I do own 4 of their non-solar models (including one for my aircraft - aviation batteries are EXPENSIVE to replace: hundreds of $) and have been happy with all of them. They are not cheap, but they are good.


BatteryMinder 5 watt solar charger
BatteryMinder 15 watt solar charger

 

[Fallon]

I've got the BatteryMINDER with desulfation & like it. Desulfating sounds like snake oil but isn't. Lead sulfide crystals end up insulating the plates over time eventually killing the battery as electricity can't make it in or out of the lead plates into the hydrosulferic (where the sulfur comes from) acid that is the electrolyte. If you blast them with their resonance frequency they tend to shatter.

I wouldn't recommend the 15 watt panel. It's just to big unless you are permantly mounting it to a canopy or cab roof. The 5 watt is fine to maintain a battery unless you are hoping to fully charge a battery in a dump trailer or something in under a few weeks.

Lots of wires with the Minder, at least how I have mine installed in my dash. A permanent out of the way install would be cleaner. I'm probably going to remove the little charge display LED box to reduce clutter as its not that useful.