Battery charger

[Bohemian scout]

This is my battery. I need a charger so I can keep my battery charged while my van is sitting for awhile. Could someone please recommend a few in mid range prices? I'd really appreciate it.

 

[MrAlvinDude]

A battery maintainer, for when a vehicle is just sitting there for some time.


This one seems to be recommended by the Interstate company themselves
https://www.amazon.com/Battery-Tender-021-0123-Junior-Charger/dp/B000CITK8S



If you want something cheaper, try out this one
https://www.amazon.com/DZT1968-Motorcycle-1300mAh-long-lasting-Maintainer/dp/B071NZ73ZF

With this one, I would monitor the battery voltage (using a multimeter) to make sure it does not go higher than somewhere around 13.8V to 14.2V

Once it is determined that it does not over-charge the battery, it can be just be rechecked with a multimeter every so often, like every two weeks or once a month.

 

[John61CT]

You should buy a charger that will properly take care of the banks you will buy in the future, not just what you have now.

Avoid overly "smart" ones with automated pulsing "desulfating" and equalizing routines that can't be disabled.

Avoid cheap "garage style" units designed for, undemanding Starter battery usage.

Good units for the RV industry are confusingly called "converters". ​Progressive Dynamics is a good mfg.

I prefer marine quality myself, Sterling ProCharge Ultra and ProMariner Pronautic P.

You could even use an adjustable straight power supply, but only if you are manually monitoring the charge process, you can't just set it and forget it, like a good automatic charger. Also make sure its current is overrated for your bank, or it has good current overload protection. Mean Well is a good brand, as is Samlex.

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The larger the AH of the bank, the higher its amps capacity needs to be. No problem with using one that's oversized for your current, temporary battery.

One that allows you to adjust the setpoints, create a user-custom charging profile, will allow you to use whatever battery chemistry you prefer in the future: FLA vs AGM or GEL, or ideally one day get away from lead and step up to LFP.

Temperature compensation is important for the more sensitive lead chemistries, ideally via a dedicated sensor wire.

______
If you just want something cheap and "good enough" for that battery you have now, look on Craigslist or eBay for something over 8A, 15A would be better, and google for the specs sheet and/or user manual.

You should be able to find something for under $100 that way.

 

[John61CT]

Note that a low-amp Float charger is fine for keeping a full bank topped up, counteracting the 3-6% self-discharge every month.

The ones Alvin links to are around 1A.

But completely unsuitable for getting a 50% discharged deep-cycle bank back up to 100% Full overnight.

30A would be the lowest I'd recommend for even the smallest and cheapest true deep cycling bank.

 

[tx2sturgis]

All you need to maintain the battery while it sits is one of these:

https://www.walmart.com/ip/6-12-Volt-1-5-Amp-Maintainer/13005742

I have one and it works fine.

 

[tx2sturgis]

Here is my Speedcharge (actually a battery maintainer) hooked up to a motorcycle battery. 

Very simple, no settings, just hook up the battery clips, and plug it in. I've had it for a few years. 

Suitable for larger batteries too.



There are literally hundreds of these little smart chargers on the market, and most of them are well under $50.

Here is another one I own, keeping another battery in good shape:

 

[MrAlvinDude]

I know I probably should not do it but.....
this combination seems to be an interesting solution to simply maintaining a battery, while a car/van is just sitting there. 

https://www.amazon.com/LIYUDL-Controller-Battery-Intelligent-Regulator/dp/B072KNC978
https://www.amazon.com/ECO-WORTHY-Module-Battery-Charger-Camping/dp/B00FF1KEMI



Here with a video example of setting it up.

 

[Bohemian scout]

I know I probably should not do it but.....
this combination seems to be an interesting solution to simply maintaining a battery, while a car/van is just sitting there. 

https://www.amazon.com/LIYUDL-Controller-Battery-Intelligent-Regulator/dp/B072KNC978
https://www.amazon.com/ECO-WORTHY-Module-Battery-Charger-Camping/dp/B00FF1KEMI



Here with a video example of setting it up.

Yes, very interesting in fact that was awesome! I actually understood the set up and feel I could do that. Not sure if I will yet because of not knowing where to place the solar panel but...I wouldn’t have to plug in a charger and since I park on the street, that’s important. Thank you !

 

[tx2sturgis]

You have to park on the street? And it's going to sit there for awhile?

Well ok that changes the answer a bit.

Maybe what you want is one of those little solar battery trickle chargers that sit on the dashboard and get some sunlight thru the windshield.

 

[MrAlvinDude]

... because of not knowing where to place the solar panel but...

Well, in the video, Adam just placed it inside of a window. And like tx2sturgis also mentioned, then it could perhaps simply be placed in the front window, or any other window of the van, and preferably a window facing south. 

A disadvantage of placing it behind glas of a car, is that some car windows actually have light filters built into them (invisible filters) that limits the functionality of a solar panel.  But it depends on the solar panel, and the particular window, as not all vehicle windows are constructed the same. 

At one time I did however try this out in my own car, and for that window and that panel, everything worked out just fine. 


But like I said, it is just an idea, so there might be some kind of alternative to needing to run a wire to the van, or to move the battery from the van to the garage, and hook up the maintainer system in the garage.

 

[Bohemian scout]

Yeah, I live in downtown Tulsa and don’t have a garage, well actually I do...a garage apartment which I live in! I park on the street across from my place so can’t use an extension cord either. That’s one reason why I want solar, when I’m not on the road I need my battery to stay charged up. When I am on the road I want to be able to dry camp in one place for as many days as I want to. I run a 18 qt dometic fridge and a 12 volt van. Maybe in the future I will want to power more 12 volt stuff but for now that’s it. I like the idea of a small portable solar that gets sun from my window. It would have to be my back door because I have to park facing north. I suppose I could remove the battery and bring it to charge but ...

 

[tx2sturgis]

Miss Bo, how much time in weeks or months will the van sit without being driven?

If it's just a week or two, you have nothing to worry about IF the battery has zero loads on it and is fully charged.

You could unhook everything from that battery to 'air-gap' it. This will limit the discharge to 'self discharge', which is not much, especially in cold weather. You could also use a small inexpensive battery disconnect switch.

If the van is undriven for a month or more, you DO need to find a way to keep it charged.

 

[MrAlvinDude]

I like the idea of a small portable solar that gets sun from my window. It would have to be my back door because I have to park facing north. 

How big are your back window(s)? 

The suggested (10W) panel is 0.5 x 10.1 x 14.9 inches (at $1.99 per watt)


Here is another option, it is 0.6 x 9.3 x 13 inches, but is only 5W (at $3.98 per watt)
https://www.amazon.com/ECO-WORTHY-Portable-Battery-Charger-Batteries/dp/B015ZGDYII



This one is 1.9 x 8.2 x 10.4 inches, and also only 5W (at $3.10 per watt)
https://www.amazon.com/ECO-WORTHY-Polycrystalline-Panels-Module-Charging/dp/B00OZC19AY


This is physically small, it is 0.1 x 5.7 x 5.7 inches, and 3W (at $3.99 per watt)
https://www.amazon.com/Sunnytech-250ma-Module-System-Charger/dp/B00Z2XC3B4
This one comes without wires attached, so they would need to be soldered on, and that is it entire own story. Not difficult or expensive, no that we have USB soldering irons, but still probably an unknow skill. 


Because it is behind glass, and not at an optimal angle, I would choose to use a 10W or higher watt panel, that fits in the back window. 

Preferable I would glue it to the roof, but that is again an entirely different story.  For now, it just needs to fit in the back window. 


So looking at the one task at hand: making sure that the battery will stay topped off, while parked for some time. In the particular spot it has, then the size of the back window sets the limit in size for the solar panel.
And for a solar panel to work, the entire panel needs to be able to fit in the window, with no areas of the panel being shaded more than the rest of the panel. 


And by the way, this is the charger model that Adam Welch used in his video
https://www.ebay.com/itm/SJ3A-Solar-Panel-Charger-Controller-Regulator-PWM-12V-3A-LW/182286295381
and this one is only about $5. It is a max 3A, PWM-style controller (meaning it can max do a 36W panel) 



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On a completely different note! 
A 10W panel, placed on the roof, would collect a maximum of 10W / 12V = 0.83A which is 0.83Ah each hour it is placed in the sun.  Perhaps it only collects half that, because it lays flat on the roof, that would still be 0.41Ah of energy collected each hour. 

In January there is sun in Arizona for about 10 hours a day.  So a 10W solar panel, could possibly collect between 4Ah to 8Ah per day, on a fairly sunny day. 


If your fridge motor needs to run 20 minutes every hour and uses 7 amp when running, for the fridge to stay cold, 
that is  20 / 60 hour  x  7A = 0.25Ah per hour to keep the fridge running.   
From Bob's video, it seems that his dometic fridges needs to run much less than 20 minutes every hour, in order to keep cold. But lets just say that your fridge actually needs 0.25Ah an hour, in order to keep cold. 
That would be 24h x 0.25Ah = 6Ah per day, to keep the fridge running. 



Or in other words, a 10W solar panel placed on your roof, while you are parked, in Arizona, in January, might actually be able to keep your fridge running. 
Or can at the very least delay your need  to get the battery charged by driving the van. So rather than needing to drive it once or twice a day, to keep the battery powered enough, then you might only need to do half of that. 
 

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But I am allowing myself to get side tracked. So back to the task of keeping the battery topped off while the van is parked for an extended period of time.

 

[frater secessus]

A battery maintainer, for when a vehicle is just sitting there for some time.

This one seems to be recommended by the Interstate company themselves
https://www.amazon.com/Battery-Tender-021-0123-Junior-Charger/dp/B000CITK8S

I've got a 1.5A and .75A Battery Tender;  both are great for holding a maintenance charge.  Got the bigger one for $5 at a garage sale.    I put it on whatevers not being used:  tractor, scooter, bike, truck, whatever.

 

[user 37446]

well I had to delete my entire reply cause I read pg 2 where Scout says he has to park across the street, thus no use for an ac powered battery charger it seems.

I had read up on the smaller (30 watt or less) panels that could be placed on the dash or propped up in a window for recharging. Unfortunately my Prius has dark tinting and the windshield is shaded as well, so none of them would work for me. Hopefully you have clear glass somewhere for the smaller panels. Just a note, I don’t think the 10 watt size will do anything amperage enough for you due to charging inefficiencies behind auto glass. Better choice might be the 20-30 watt ones, still affordable and even a $10 PWN controller on a 30 watt panel would likely be cheap enough. The one shown below only generates 1.6 amps... Here’s an example from Amazon: https://www.amazon.com/Monocrystall...=2025&creative=165953&creativeASIN=B01M9B6RQI

25 Watts Monocrystalline Newpowa High Quality 12v Mono Solar Panel Module
20W < 25W < 30W Rv Marine Boat Off Grid
4.4 out of 5 stars 19 customer reviews | 28 answered questions
Price:$39.97 Free Shipping for Prime Members
In Stock.
Want it Tuesday, Nov. 28? Choose One-Day Shipping at checkout. Details
Sold by Newpowa America Inc. and Fulfilled by Amazon. Gift-wrap available.
Maximum power (Pmax): 25W
Voltage at Pmax (Vmp):17.2V
Current at Pmax (Imp): 1.45A
Open-circuit voltage (Voc)：21.6V
Short-circuit current (Isc)： 1.6A

 

[willprowse]

You should look up the safe charging amp spec for that battery and buy a charger that provides that much power

 

[MrAlvinDude]

On a completely different note! 
A 10W panel, placed on the roof, would collect a maximum of 10W / 12V = 0.83A which is 0.83Ah each hour it is placed in the sun.  Perhaps it only collects half that, because it lays flat on the roof, that would still be 0.41Ah of energy collected each hour. 

In January there is sun in Arizona for about 10 hours a day.  So a 10W solar panel, could possibly collect between 4Ah to 8Ah per day, on a fairly sunny day. 

Here is a link to frater secessus' excellent post, on how to do a more specific calculation of how much solar power is likely to be harvested from a solar panel placed flat on top of a roof. 
https://vanlivingforum.com/showthread.php?tid=27940

As I understand the information given in that post, it is true that the sun is up for about 10 hours in Arizona, in the month of January, but the average full-on-sun is much less.
More specifically it seems to be closer to 3.25 hours, on average, for the month of January. Named "Full Sun Equivalent ". 

Then there are losses.
Because of being layed flat, and not tilted. Loss because of heat build up in the solar panel. Losses in the charge controller. Pushing energy into the battery also looses a bit, compared to what can again be taken out of the battery. 
For more details, see  frater secessus' excellent post

The conclusion is however, that a system consisting of a 10W solar panel, layed flat on the roof, connected to a cheap PWM controller, is likely to collect and store 1.65Ah (or 21Wh) into the battery , on an average day in January in Quartzite,  Arizona. 
So, not much to speak of. 


I also see that I did a typo on the fridge power need, in my previous post.
As 20 / 60 hour  x  7A  (is actually) = 2.3Ah, for the fridge to run for 20 minutes. 


Just thought I would leave this updated info in this thread, if someone were to read it at a later date. 


21Wh is more like what it takes to charge a smart phone once or perhaps twice.

 

[Bohemian scout]

Finally got around to getting the battery charger. I bought a battery tender jr. at Home Depot for $19.98. My reading on the multi meter was 12.5 before I hooked it up. I was able to park in the driveway of the big house and plug in the battery charger. I will keep it checked out. It’s suppose to automatically switch to storage/maintenance mode when fully charged. Eventually I will get a 100w or so solar panel to mount on the roof (think I’ll get a rack first) then maybe a portable solar unit for shade camping. Thanks for everyone’s replies.