Battery cut off switch

[Pooneil]

Originally Posted by ko777

Do you know where to cut off the battery inside the trailer? Install a cut off switch inside, this way I could turn it off easily before sleeping. I will do this exercise during dry camping.

You do not want to cut the battery off when occupying the camper without considering the results. Cutting off power would disable the the propane detector and put you in potential danger.

The propane detector is a the main draw on the battery at night, if the furnace is not running. So rerouting the wire to leave it on while shutting off the no draw lighting and pump circuits off doesn't make sense to me. If you want to stop small parasitic draw from the stereo, use a switch just for that.

I know that some people do not use a battery at all, and that is their option, but I choose to use the safety devices installed in my camper.

[pgandw]

Originally Posted by D-mo

agree totally with Garbonz, what the point of having a two battery system if you are only going to use one at a time. Double it up .. and dont worry about the alternator ... I have never had any problems with my two deep cycles. Batterys are just receptacles for charge, and do not add any stress or strain on either an alternator or your trailers converter unless you have discharged them over the 50 percent level .. but in that case the batterys would last long in the first place ..

d-mo

I beg to differ. From my sailboat days and electrical work:

Operating a 2 battery setup:

Because batteries are never perfectly matched, there will always be some parasitic flow between them when paralleled. When under charge, this is usually acceptable.

Dry camping - use one battery until it reaches about 70% (for long life). Use the second thereafter. When charge is available, the decision to charge in parallel or singly is really going to depend on the relative charge states. If one battery is at 90% or better, and the other is less than 90%, the more discharged should be recharged singly until reaching 90%. Then recharge in parallel if desired.

Today's vehicles use processor-controlled alternators, just like the advanced converters in our campers. Paralleling 2 Size 29 deep cycle (the configuration I originally wanted) that are both down to 60% with the car battery will cause the electronics to put the alternator at max (could potentially cause a smaller vehicle alternator to overheat) and over-charging the vehicle battery. More importantly, the A122 wiring to the batteries and vehicle connection (and probably within the vehicle, too) is too light to carry even 25 amps of charge current for more than a few minutes. The voltage drops in the standard wiring from heavy currents will cause the charge voltages to be less than they should be, and a less than optimum charge rate.

Using one battery on the camper at a time avoids these issues, and keeps the second battery as a ready reserve. You are correct, the 1st battery should not be discharged to 50% (70% is about right unless dealing with true deep cycles) before switching to the 2nd.

I'm more paranoid than most because in my sailing days, having a battery in reserve meant you had a way to start the engine and/or get off radio calls. I had the 2nd battery installed on the camper so we would not have to cut a trip short due to insufficient battery to run the heater. Having the 2nd battery in reserve means that when I switch batteries, I am knowingly eating into my reserve.

In the camper scenario, something goes wrong (like forgetting to turn the fridge off DC - been there, seen that and the ruined battery at the start of a trip) and the battery is discharged prematurely. If the batteries are in parallel, I have no reserve to bail me out.

Fred W

[D-mo]

" I have never had any problems with my two deep cycles. Batterys are just receptacles for charge, and do not add any stress or strain on either an alternator or your trailers converter unless you have discharged them over the 50 percent level .. but in that case the batterys would last long in the first place .. "

d-mo

d-mo

[camaraderie]

One can choose how many cycles one wants to get VS. the pain of constantly recharging a deep cycle battery via this chart. NOTE that the 1000 cycles at the 50% discharge point is ARBITRARY...but the curve holds for wet cell deep cycle batts. If your only gonna cycle down 30% then you'll get almost twice as many cycles...10% = 5 times as many cycles. Personally I wouldn't put up with needing to re-charge at either of those points...my time is worth something. On the other hand...you can see that discharging much below 50% could start to get expensive.
Note that getting from 80 to 100% on a charger takes as long as getting from 20 to 80%.
Hope the chart is helpful as you make your own decisions about how deeply you want to discharge.
***************

The idea however that a Hyundai 130amp alternator can't replace 75 amps to a couple of group 24's is ludicrous at best. I too had a sailboat which I lived on full time for 6 years over 90% of the time at anchor and at sea. I had 1100 amp hours in a single house bank...batt 2 was my 110amp starter battery (Group 31). I had a four winds wind generator, 160 watts of panels, an 8KW Westerbeke diesel genset and a 120amp Balmar alternator on the engine.
Guess what...with batteries depleted...the alternator would fill em right up to 100% on my Xantrex monitor if I had to motor for the day.
I also had their 140amp charger with 3000wat MSW inverter which I ran from the genset.
Used about 150 amp hours a day and put back about 100 on average passively...& the balance with the charger.
So pardon me if I don't think you need to break your battery bank in two. What you need is a battery monitor that can tell you exactly what is going on with amp hours remaining and used. You have NO way of telling when you are at 70% (or 50%) otherwise since your voltage reading IN USE are not an indication of your remaining battery capacity.
S

[pgandw]

Originally Posted by D-mo

" I have never had any problems with my two deep cycles. Batterys are just receptacles for charge, and do not add any stress or strain on either an alternator or your trailers converter unless you have discharged them over the 50 percent level .. but in that case the batterys would last long in the first place .. "

d-mo

d-mo

I'm sure your report is accurate - for your specific circumstances. You don't say what size batteries you are using, nor what wiring. You are using a 4x4 truck, not a minivan, as the TV which means it likely has a different alternator and programming. You don't say how much dry camping, and how much the heater is running.

I gave my assessment of my tow vehicle and my camper wiring as reasons for using 2 size 24 batteries instead of a larger battery bank. I didn't look into the specs of the converter because I saw the wiring and my tow vehicle alternator as the limiting factors, and assumed the converter had excess capacity.

My using one battery at a time instead of always running the two in parallel further minimizes any issues from the trailer/vehicle wiring, programming of my minivan's alternator, and differences in the batteries.

Proper maintenance of a lead-acid battery is actually fairly complex, as simple Internet research will show. Which is why the camper converter has 3 distinct battery charge cycles, and why today's vehicle alternator is much more complex than the old 2 stage generators and alternators.

Will my methods give any better battery life than yours? There are too many other variables at work to say for sure. Bottom line: probably not enough difference to matter.

But I do prefer my one-battery-at-a-time option operationally, regardless of whether it increases battery life. I have seen too many camping trips ruined by discharging a single battery at the beginning of the trip. Things that have gone wrong (to friends as well as me) include accidentally tripping the break-away switch (mentioned in another thread here), batteries not charging while towing due to wiring/plug issues, and leaving the fridge on DC for a few hours after disconnecting.

Because I anticipate using the A122 dry camping for long weekends 3 seasons in the Colorado mountains, I wanted more battery capacity than the standard single size 24. The limitation on my old popup dry camping for more than a week at Lake Tahoe during the summers was battery capacity to run the heater. Some summers, the battery would last 10 days. Others, it was lower than I would like, and would need recharging before the end of the week.

That doesn't mean that you are wrong for doing it your way. I gave my reasons for disagreeing, and doing things a different way. Others can read what I have done, and why, and make up their own minds.

Fred W

2014 A122 (previous 2001 Coleman Westlake PUP later upgraded to single Size 27 Sears marine deep cycle)
2008 Hyundai Entourage (previous 1992 Ford Explorer)

[pgandw]

Some excellent discussion on batteries here. Caused me to think things through.

I went back and looked at my stock A122 wiring. The wiring to the battery is 10 gauge, which means it's rated for no more than 30 amps (approx), and at 30 amps will see some voltage drop over longer wire runs. Makes sense, with the converter rated at 30 amps.

Pushing more than 30 amps from the alternator back to the camper battery through the vehicle wiring, plug, and camper wiring is probably not a good idea - things will start to heat up. However, it's probably self-limiting in that the wiring voltage drop will cause the charge rate of the batteries to be lower. So there is probably no issue with running 2 size 24 batteries in parallel even in bulk charge status (15 amps each). However, 2 bigger batteries in parallel might be an issue, which is what the FR dealer was trying to tell me. Physical space is also limited to 2 size 24 batteries unless significant relocation work is done.

Adding the switch will allow me to turn the batteries off for storage (the original point of the post), run separately, or in parallel.

From the draw side, the load of concern is the furnace fan while dry camping. I need to look up fan specs and measure the duty cycle on our first few camping trips. I'm hoping that a single battery can go 2 normal nights or 1 very cold night without excessive discharge. If not sufficient, I'll have to look at a gas catalytic heater solution.

The whole goal of the A-Frame is to keep everything as simple and/or easily managed as possible to maximize desire on DW and my part to use the camper almost spur-of-the moment on weekends in the Colorado mountains.

We got the smallest model so it could stay in our garage and be towed easily. But the close quarters and minimal storage are not well-suited for a week-long stay.

We didn't bother with the awning/attached shelter because of the Colorado winds and the short-term stays.

I did go with the equalizer/anti-sway bars to make us feel comfortable while towing. So far, the difference and confidence in ride is more than worth the extra hitch-up and unhitch time.

The dual size 24 battery solution hopefully enabled our dry camp endurance to a long weekend in the mountains with minimal extra expense and hassle.

looking forward to camping very soon (snow forecast again this weekend)
Fred W

[ThunderRoad]

Last year I did a mod to add a cut-off switch for the stereo, so now my only real phantom power draws are the propane alarm and a tiny LED on a USB power outlet I added a couple years ago. I also added a Group 31 AGM battery to replace the crappy Group 24 that came stock.

At the end of the season, I let the camper sit unplugged for 3 weeks as a test. I then checked and the battery was still at 65% capacity. With LED light replacements as well, the only real power I use is if I run the furnace, and at the tail end of the season I was out for 4 days with the furnace running at night and I never ran out of power.

I think whole-system cutoff for aframes is kinda overkill. I've thought about adding one, even purchased it, but I know some time I'm going to forget to turn it on and it will cause some problems. Just hasn't been a priority.

My recommendation is to add a power cutoff for the stereo, replace your overhead and outside lights with LEDs, and call it a day unless you really want to go crazy.

[ko777]

Finally installed the cut off switch. It is installed right after the fuse holder.

Even when off, the lights in front works when TT is plugged to the TV, It looks like the power is split to the TT...maybe someone could explain this findings


Added a lighter female adaptor to connect the solar panel


While recharging the battery by the solar panel, the other two ports could be use for USB charging PDA

[ko777]

Zoomed in to see the part

[ko777]

I plan to camp at my friend's lot for a couple of days, then leave it there for a week or more. Hydro is off so the TT battery needs charging. If I leave my 40W solar panel charging the battery for more than a week, will it over charge it? The cut off switch will be off so the battery is not bring drained.

[rawlus]

It is unlikely that small panel could overcharge the battery, and the panel likely had built in circuitry to prevent it regardless.

[ko777]

Ok then...I'm testing with cut off switch set to off. Currently the TT battery voltage is 12.6, it will be recharged by a 40W solar panel, I'll check the voltage changes after a couple of days. Here is a pic of my setup:

After this test, I'll try with the cut off switch set to on...lol "on" means power to the TT. I want to find out if the battery drain is recovered by the solar panel.

[ko777]

Test 1: After 4 days solar panel charging, the TT battery was charged from 12.6V to 13.5V.

The next test is now set to determine if the 40W solar panel keep the battery charged with the cut off switch not active, so there is a small drain to the battery.

[camaraderie]

KO...unfortunately...that is NOT true...the battery cannot be charged to more than 12.7Volts. What you are reading is the CHARGING voltage from the panel OR the surface charge left by the panel.
The next test should be to remove the negative post wire from your battery entirely...measure the voltage within 10 minutes of removal...if it is at least 12.7 volts at the battery poles....then wait 24 hours then test the battery voltage at the poles of the battery again. If it is 12.6 or 12.7 you are in excellent shape. 12.4 or 12.5 beginning to lose measureable capacity. Less than 12.4 and you are on your last legs.
If it dropped immediately below 12.7V when you first measured, you did NOT get a full charge on it from the panel.
**********
A 40 watt panel ON AVERAGE should be able to pretty well keep up with about a 10 amphour drain per day from both parasitic loads and self discharge.
This works out around .3 amphours for self discharge + whatever you can measure as parasitic drain TIMES 24 hours. A clamp meter could tell you your amp drain in 5 seconds and you'd have some answers quickly. i.e. if your drain is .5 amps...then you're gonna use at least 12amp hours a day (.5 x 24 hours) and your 40 watts won't keep up.

[ko777]

Tested the voltage of the battery after several hours of no sun, 13V. Turned on the outside light for a minute, dropped to 12.8V, turned off the light, went back up to 12.9V.

[camaraderie]

Good...you have a surface charge...but batts are FULLY charged. Now do step 2 and remove negative post wire and test again in 24 hours...you should get a 12.6/12.7
Assuming all is well... you can try your next test or simply use a DC clamp meter to project your needs. You can even do that before you test the actual voltage in 24 hours if you have access to one.

[ko777]

Originally Posted by camaraderie

Good...you have a surface charge...but batts are FULLY charged. Now do step 2 and remove negative post wire and test again in 24 hours...you should get a 12.6/12.7

Your right the battery is fully charged, before the tests, it was already 12.6V before it was installed back to the TT. I will let this setup ride till the end of the week and disconnect the solar panel and activate the cut off switch. Test the voltage as you suggested 24 hours later. Hopefully the 40W solar panel can keep up with the battery drain.

[ko777]

Originally Posted by rawlus

It is unlikely that small panel could overcharge the battery, and the panel likely had built in circuitry to prevent it regardless.

BTW when I test the voltage this afternoon under the bright sun with the solar panel on, the voltage was 14.2V. It never went higher, so are you sure this will not over charge the battery if the sun is bright all day?

[ko777]

Originally Posted by camaraderie

A clamp meter could tell you your amp drain in 5 seconds and you'd have some answers quickly. i.e. if your drain is .5 amps...then you're gonna use at least 12amp hours a day (.5 x 24 hours) and your 40 watts won't keep up.

First time I heard about clamp meter, I'm ordering one:

I'm curious of what I get, where is the best place to measure it?

Can you measure how much amp the solar panel is pumping out with this device?

I got this link on how to use a clamp meter:

http://m.youtube.com/watch?v=nxhUwH70F_4

[camaraderie]

Couldn't check specs for the one you are ordering but make sure it does BOTH AC and DC amps...many of the really inexpensive ones don't...even thought they measure voltage both ways. The cheapest AC/DC amp clamp meters I've found are in the 50-60 buck range on Amazon.

As to where to use it...just clamp it over your red main battery wire to measure DC amps parasitic load...or the load of any particular piece of equipment when you switch it on.
When clamping...just make sure to clamp a SINGLE wire...not both the +/- . This is sometimes a problem with dual conductor AC wire...and this little device is what you can plug into...which effectively separates the wires to enable you to clamp without cutting!


Amazon.com: Auto ranging AC/DC Digital Clamp Meter: Home Improvement

The above link is for the meter I use now in case the one you're looking at is not ac/dc for amps.