Best Way To Keep Batteries Charged

nighthawk87 · 02-16-2018, 02:08 PM

What’s the best way if you store your trailer in an area that doesn’t have access to 110v?

During the trip the generator will charge to 90% and ideally one can leave at 90% charge. Do you just leave in storage at 90% and charge back to 100% by bringing the trailer home the night before and plugging it in? I would think it’s bad for the battery to sit at 90% charge.

I have read it’s good to charge back to 100% every 10 discharge cycles or so.

Could pull the batteries each time and take hoe to charge but that’s backbreaking.

Any ideas? I can’t be the only one with this issue. Or am I the only one who has thought it through and cares?

lefoster · 02-16-2018, 02:12 PM

I have a small solar panel that hooks to batteries and has kept them charged. also have a disconnect switch on them, so things in trailer don't pull on them. obviously you need sunlight where you are storing your trailer.

bankr63 · 02-16-2018, 03:38 PM

A small portable solar panel (40W) that I pop onto the roof of the TT in the storage yard. This keeps the battery topped up and ready to go all summer long.

nighthawk87 · 02-16-2018, 03:46 PM

Quote:

Originally Posted by bankr63

A small portable solar panel (40W) that I pop onto the roof of the TT in the storage yard. This keeps the battery topped up and ready to go all summer long.

Would you mind sharing a link to the one you have? Does it have a charge controller?

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bankr63 · 02-17-2018, 04:48 PM

Sure,

The panel I have is Coleman branded in Canada, but I'm fairly certain it is not branded Coleman in the US, although I have seen what appears to be the same panel and controller on Amazon.com, just with a different brand. I would take a look at the photo at Canadian Tire here Coleman 40W Folding Solar Panel | Canadian Tire and compare to what you find online at Amazon.

This is solid (non-flex, crystalline) panel and works well for us. I get great sun at the storage lot so don't have to move it, it slides right into the storage bay on top of my bins, and it is easy to move around the campsite when wilderness camping to keep it in the sun. I just used a couple of zip screws to attach the controller (included) to the side of my battery box, with the leads hanging out the lid.

And don't let the price scare you. These are regularly on sale at 70% off; a bit less than C$90.00 - about US$70.00

ETA: couldn't find it on Amazon this time, but there are ton on eBay right now, pretty much all shipping from Canadian sources.

GrumpyDad · 02-17-2018, 06:14 PM

90% isn't terrible for storage. Guess it depends on the voltage that translates to.
I also store my trailer where it doesn't have 110v power, so I'm sure my batteries are less than 100% when I park it usually. I disconnect the batteries and don't worry too much. I am quite careful about plugging it into shore power at home overnight before I leave for most trips though.

If for some reason I suspect the batteries aren't fully charged, I do run my generator on day 1 of a trip. If I have started with a full charge I usually wait until day 3.

ALJO · 02-17-2018, 07:12 PM

a wet battery looses approx. 1% of its storage capacity a day, so you can count the days for re-charging. A dead battery will freeze and if it goes below the 11.9 Volt mark for a longer time, the hold charge quality of the battery will go down.
The saying: 'maintain it or loose it'

nighthawk87 · 02-17-2018, 07:45 PM

What’s a good deal/place to get a 100W solar panel and charge controller that I can expand up to 400w at a later time?

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Parcany · 02-18-2018, 08:44 PM

When parking our travel trailer for months I installed a disconnect switch. I just flip the switch when parking and when I go back could be months I close the switch and the batterys are still charged. Then when I would take the trailer home I would plug it in and charge the batterys up.

GrumpyDad · 02-19-2018, 03:17 PM

Quote:

Originally Posted by Parcany

When parking our travel trailer for months I installed a disconnect switch. I just flip the switch when parking and when I go back could be months I close the switch and the batterys are still charged. Then when I would take the trailer home I would plug it in and charge the batterys up.

This is a very commonly used strategy and it works great for most people.

Bilz · 04-20-2018, 01:24 PM

Somewhere on this site there was a post of a chart that showed voltage compared to % of charge. I did a search but came up with nothing but a lot of other great information about batteries and solar panels. What a great resource this place is. Anyone remember this chart?

andrewat · 04-20-2018, 01:41 PM

I just disconnect the positive terminal when I put it in storage. Some day I'll install a switch. But for now, I just disconnect it altogether. When I go to get the trailer, I don't bother with tightening it down with a wrench. Hand tight is plenty tight.

bdreinv · 04-20-2018, 02:46 PM

We are in Arizona did Solar couple years ago, works fantastic. Never wonder about batteries anymore! Thanks

dennis b · 04-20-2018, 03:51 PM

Best way? Keep it plugged in! otherwise I use my solar suitcase.

CampNow · 04-21-2018, 10:33 AM

Quote:

Originally Posted by Bilz

Somewhere on this site there was a post of a chart that showed voltage compared to % of charge. I did a search but came up with nothing but a lot of other great information about batteries and solar panels. What a great resource this place is. Anyone remember this chart?

Don't have a link to a full chart at the moment. However, for most RV'rs the most helpful (and important) voltage to percent of charge (or state of charge) values to know is 50% and 100%. 50% state of charge is typically the lowest voltage you want to discharge your batteries to before recharging. Commonly accepted voltage for 50% state of charge is approx. 12.20 volts, and approx. 12.70 volts for 100%, for most wet-cell batteries. Some charts will show slightly higher voltage, some slightly less. To get the most accurate (percent/state of charge) voltage reading, you should 1) turn off all 12 vdc lights and appliances, and 2) wait a few hours after disconnecting or turning off any converter or charge devices. Otherwise, you won't get an accurate voltage reading.

RichR · 04-21-2018, 01:51 PM

Here is a very much shared website about 12 volt power " The 12 Volt Side of Life". It is a very good source to bookmark and keep for future reference:
The 12volt Side of Life (Part 1)
And part 2:The 12volt Side of Life Part 2

There is a chart in Part 1 that shows the level of charge by the voltage. 12.0 Volts is the lowest voltage limit before charging is required to help maintain the maximum life of the battery.

CampNow · 04-21-2018, 08:52 PM

Quote:

Originally Posted by RichR

Here is a very much shared website about 12 volt power " The 12 Volt Side of Life". It is a very good source to bookmark and keep for future reference:
The 12volt Side of Life (Part 1)
And part 2:The 12volt Side of Life Part 2

There is a chart in Part 1 that shows the level of charge by the voltage. 12.0 Volts is the lowest voltage limit before charging is required to help maintain the maximum life of the battery.

I disagree.

First off, the author of this article (in Part 1) states, "If a battery is discharged to only 50% each cycle, it will last about twice as long as if it is cycled to 20%." This concurs with the commonly accepted practice of not discharging a wet-cell battery below 50% SOC to ensure maximum life of the battery.

Secondly, the author uses two State of Charge (SOC) charts in Part 1. I found the first SOC chart (in color) confusing and misleading. He/she qualifies the first SOC chart by stating: "This chart is designed to be used when monitoring a battery under load." The first chart states a battery with a 50% SOC should read 12.06 volts while under "load". To my knowledge, the load is not defined for this first SOC chart. Battery voltage can fluctuate dramatically depending on the severity of the load. Without knowing the exact/specific load on a battery it is NOT possible to determine SOC with any accuracy using just a voltmeter.

Thankfully, a number of paragraphs later, the author uses a second SOC chart (in black and white) and this time explains how to check SOC using a voltmeter (and hydrometer) . . . with no load. This chart concurs with the most commonly accepted practice of using ~12.2x volts as a reference for 50% SOC with no load to ensure maximum life of the battery---not 12.00 volts . . . or 12.06 volts with an undefined load.

A well written article with the exception of the first, misleading, SOC chart.

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