benrogers
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Post by benrogers on Aug 26, 2014 10:56:58 GMT -8
As an electrician this is kind of embarrassing but when I take the battery off the trailer and to the basement what is the best way to charge it and keep it charged?
I can pick the right battery for my needs and can pick the right set of solar panels but when it comes to the maintenance of charging on my bench I'm kind of lost.
All help appreciated!
Ben
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Post by bigbill on Aug 26, 2014 13:54:01 GMT -8
Buy a quality battery maintainer and plug it in, it will supply a minimal amount of current to keep the battery at full charge without causing excess build up on the plates. Most will require the battery to be charged first then it will keep it at full charge.
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John Palmer
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Post by John Palmer on Aug 26, 2014 15:09:41 GMT -8
Ben, It's better to ask. BigBill is exactly correct with his answer.
The "reason" you will "want to do this" is because the plates inside the battery will sulfate if it not kept fully charged all the time. Think of sulfated plates "as having rusted coating on them" that electricity cannot penetrate.
If you think about it, your daily driver car's charging system is working all the time the engine is running, and the regulator keeps it from overcharging your battery. But batteries used in recreational vehicles (motorcycles/atv's/jet ski's/snowmobiles/camping trailers/hot rods, etc.) that get used infrequently have a very short life due to the sulfate coating on the lead plates. You will increase the life of your RV battery dramatically by leaving it on a Battery Tender all the time it is inactive. It takes a tender of about 2.5M in size to work good. Many of the cheap HF tenders are only .25MA. You can buy generic brand quality 2.5MA tenders for under $40 at any large electronics store. Battery Tender JR's are about $65.
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benrogers
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Post by benrogers on Aug 26, 2014 16:22:24 GMT -8
Will the tender charge the battery then maintain it or do I need two different pieces of equipment?
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John Palmer
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Post by John Palmer on Aug 26, 2014 17:10:52 GMT -8
Will the tender charge the battery then maintain it or do I need two different pieces of equipment? You need size of "2.5MA", it will do both. |
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benrogers
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Post by benrogers on Aug 27, 2014 4:41:13 GMT -8
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John Palmer
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Post by John Palmer on Aug 27, 2014 8:27:47 GMT -8
Well.......did you notice it says item is UNAVAILABLE?
I see several red flags, not a brand name and it's still $60 bucks, it cannot be 3500MA, it might be 3.5MA, so it's miss labeled (IMO).
Why try to reinvent the wheel. If you want to spend $60 bucks just buy a Battery Tender JR. (Brand name, and Model name) and be done with it. Hard wire it into your trailer battery at the fuse panel and plug it into a 110v receptacle, then forget it. It will do all the thinking and charge when ever it's necessary.
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benrogers
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Post by benrogers on Aug 27, 2014 8:52:46 GMT -8
John,
I can't always have the trailer plugged in is the problem. I was planning on just setting the battery on my workbench since it will also be an external battery.
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John Palmer
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Post by John Palmer on Aug 27, 2014 9:42:22 GMT -8
John, I can't always have the trailer plugged in is the problem. I was planning on just setting the battery on my workbench since it will also be an external battery. Buy two, one for the trailer, and one for the work shop.
One single work shop tender will maintain multiple batteries, if wire parallel.
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benrogers
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Post by benrogers on Aug 27, 2014 10:17:01 GMT -8
So let me lay this all out.
I have a 1.6 amp roof exhaust fan in the trailer. This is the only thing we are powering via DC.
1.6A * 8 hrs = 12.8 AHrs
Purchase a 100 AHr battery which gives me 50 AHr at the 50% threshold
55 watt solar panels to recharge the battery.
55 W / 12 V = 4.58 A
My region is 6 hrs of charging time
4.58A * 6 hrs = 27.48 AHrs in a charging period
Make sense so far?
We will only be camping on shore power once a year in the Adirondacks. Not sure it's worth buying a tender or just a 120 VAC to 12 VDC converter on a switch.
Now the part I'm confused about is that I've read you have to have a fully charged batter for a tender to work properly. Is that true? Is the Battery Tender Jr. a charger and tender all in one?
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John Palmer
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Post by John Palmer on Aug 27, 2014 18:23:37 GMT -8
A Battery Tender JR. will charge a low battery, it's just a small "smart charger" and will take a long time to get the battery to 100%, but it will get there eventually.
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benrogers
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Post by benrogers on Aug 28, 2014 6:19:43 GMT -8
Thanks John!!
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cowcharge
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Post by cowcharge on Sept 24, 2014 11:49:50 GMT -8
I would add: Your solar panel probably puts out more than 12v (probably more like 18v), so your calculated charging amps from the panel is probably a bit optimistic. And the charge controller also puts out higher than 12v, so you need to divide the watts by whatever its charging voltage is to get the true amperage into the battery. Wet battery manufacturers recommend charging at 14.8 volts. An RV converter doesn't go that high, so it takes forever to get the last 10% into your batteries. Depending on your solar charge controller, you might not get 14.8 either, so you might not make the most of those six hours. If you're using a sealed battery, they charge at a lower voltage to prevent gassing, so you can use less than 14.8v. But match the charger with the type of battery to get the most juice into the battery in the least time. And don't skimp on wire size (as I'm sure you know, bein' an electrician), I used 6 gauge from the roof to the controller and 4 gauge from the controller to the battery. And go by the battery manufacturer's charging voltage specs, NOT the charger mfgr's specs or the salesman's assurances. Here's a great article about RV solar systems, written by a full-timer who doesn't even own a generator. It's long but well worth the read: handybobsolar.wordpress.com/the-rv-battery-charging-puzzle-2/ |
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