Cargo Trailer Camping Converting

[Sunking]

OK pretty safe to say your fridge is using 1 Kwh/day, plus fluff, 300 AH should work. At 300 AH will give you up to 1200 wh/day and 3 day reserve. You can go as high as 400 AH. .

[UrbanElite]

When the fridge is running its around 44 watts, so I'm shooting for 50 watts to be safe in my calculations. So far with 3 days and almost 11 hours on the counter, I have 3.423 kWh used.

Other than using some LED lighting on the inside and outside of the trailer that will be all I will be powering other than charging a couple phones, camera or some things like that. Right now we won't have a tv or anything.

So the LED lights I have for the the trailer is 4x 12v 8W bar lights and 4x 12v 2.2W,

[Sunking]

Mike I think we have that covered. The fridge consumers 50 watts, so a 500 to 750 watt TSW Inverter should work fine. I would not go any larger than a good 1 Kva TSW Inverter like Samlex SSW-1000-12A with Soft Start.

[Mike90250]

.....
Last piece of the puzzle is Inverter size. Inverter size is dictated by battery size. Assuming you use a Rolls Battery, they can handle up to a C/4 discharge. So if you have say a 300 AH battery is 300/4 = 75 amps, or 400 AH / 4 = 100 amps. That is a range of 750 to 1000 watt Inverter maximum. You can use anything smaller, just not larger.

This is where the "Theory" parts from Practice. Since you have a fridge, you need an inverter that can supply the required starting surge. A fresh, undersized battery can supply the 5 sec surge to start the fridge. BUT - you have to balance the large inverter's "overhead or tare" losses, against the rest of your system capacity. You can't just throw a 4Kw inverter in, say "I'll only use 300w of it, and starting surge will be duck soup". No No No - that 4Kw inverter will suck 60-90w just keeping the electronics warm, and if you throw 20w of Lighting on, you are sucking 80W+ from the oversize inverter. So you need to shop for a inverter that can meet your starting surge requirements (generally 6-10x running load, for 3-5 seconds), is not any larger than you need, and is a highly efficient, pure sine inverter, Sadly, my favorite, overbuilt, 12v inverter, Morningstar's SureSine 300, can't supply the starting surge for a fridge. It has very low self-consumption, highly efficient, and has 600w surge for 10 min. Some of the high quality 800w inverters can manage, and nearly all of the good 1-1.3Kw inverters can start a fridge - If the battery cables are sized (beefy enough - #4 or even #2) and the battery is in good shape.
But remember, it has to be enough of an inverter to start the fridge at 11pm, when the laptop is charging, the DVD playing, and the mood lighting is on. and too large and it flattens the battery from it's own self-consumption.

[Sunking]

So where are we at now for things I need to figure out?

Waiting for you to figure out your daily watt hour requirements. Once you know what the fridge uses, you need to estimate what else on top of that you will need. Example lighting, entertainment, and fluff. Some loads like charging a cell phone are so insignificant can be ignored. If you have lighting, determine how many watts total the lights use, then calculate daily watt hours. Watt Hours = Watts x Hours.

Add all the watt hours up, then calculate battery size. Hope it fits with your fixed panel wattage and charge controller limitations.

we know I have 2x 320 watt solar panels, I'm looking to stay in that 40A MPPT charge controller range, my fridge on average draws below 50 watts while running, and I would like to dry camp for 2 days without solar to be safe to camp over a weekend without a worry about weather.

Any other info im missing or going to need?

OK this is where you have limited your choices. Basically you have a 40-Amp battery charger. That dictates the minimum and maximum size battery it will support. You really do not have much choice and left with take it or leave it. The smallest battery is roughly 300 AH, and in a trailer with less than optimum tilt and orientation I would go no larger than about 400 AH. Assuming a 3-Day reserve capacity with 2-Day usable means your daily watt hour use is limited to 1200 to 1600 watt hours. Understand what that means? If your fridge uses that much or more, you have shot yourself in the foot. OTOH if your fridge only use say 800 wh/day, then you have a lot more to work with.

Last piece of the puzzle is Inverter size. Inverter size is dictated by battery size. Assuming you use a Rolls Battery, they can handle up to a C/4 discharge. So if you have say a 300 AH battery is 300/4 = 75 amps, or 400 AH / 4 = 100 amps. That is a range of 750 to 1000 watt Inverter maximum. You can use anything smaller, just not larger.

[UrbanElite]

I don't know about you but I'm more of a cheese guy on top of noodles, but that's a personal choice I guess.....

great info, I did enjoy reading that, that all makes way more sense how you guys get these numbers that I've been looking for. I can see now how from the start I would be missing a number and it's impossible to get the number without having all 3 or so numbers, (if my messed up wording makes sense to you).....

the last reply is great great to hear, I always heard not to go lower then 50%, so if I can go lower that will give me more time on my battery's for sure!

I will be using the system occasionally as I'm just camping on weekends, so I can use one of my chargers on the side of my garage once a month with shore power to equalize the battery's that wouldn't be a problem for sure.

So where are we at now for things I need to figure out?

we know I have 2x 320 watt solar panels, I'm looking to stay in that 40A MPPT charge controller range, my fridge on average draws below 50 watts while running, and I would like to dry camp for 2 days without solar to be safe to camp over a weekend without a worry about weather.

Any other info im missing or going to need?

[Sunking]

That's because you only use 50% of your battery correct?

No you are letting the butter slip of your noodles again. Your confusion is understandable. There are basically two types of Off-Grid Stand-Alone Battery systems.

1. Is Daily Use system used everyday 24 x 7 x 365. Example a home, a remote telemetry site, a flashing street light in the middle of no where.
2. A Part Time or Occasional Use system. Example a RV, trailer, camp site, or cabin.

Batteries are expensive and you want to get the most out of your money, and how and when you use them determines how long they will last. A Pb battery has both a Cycle Life vs Depth of Discharge time line, and Calendar Life. Whichever comes first. FWIW Calendar life is your warranty period.

In a Daily Use system you get the most bang for your buck out of your battery limiting discharge to 20% per day, or 5-day reserve capacity. You limit discharge to 50% so in practice gives you 2 to 3 day run time before you shut down and recharge with a generator. Follow that plan and your batteries should reach both end of Cycle Life and Calendar Life at the same time.

For a Part Time system like an RV, you are only using it 2, 3, or 4 days a week at most. That gives you more flexibility and options to work with. One option is you can withstand a deeper discharge than 50%, and still arrive at end of Cycle Life and Calendar Life at the same time. Reason is you discharge the batteries deeper. It does not make financial cents to use a 5 day reserve capacity to extend Cycle Life because you wil reach end of Calendar Life before Cycle Life. There is one exception to that. If you routing are limited to 2 or 3 days, then you can size to 5 day reserve capacity and forget about Solar. You just use an Isolator, and a Inverter with Built-In battery charger while parked at home base or RV Park

So you want Solar. That is fine. But you do not need to go to the expense of limiting discharge to 50% if you do not intend to be on the road everyday year round. You can discharge down to 20 to 35% SOC. A good number is 3-day Reserve capacity. That gives you 2 cloudy days of usable capacity before you need to shut down and recharge your batteries. That would mean either you have to wait for the Sun to return, and wait another 2 days to recharge before you power back up if you do not have an alternate power source like an Isolator.

The last piece you need whether it is a Daily use or Occasional use system is Pb batteries require a periodic Equalization Charge about every 30 days. Solar cannot do that. It takes up to 24 hours to equalize a battery. A Daily user like a home must have a generator for cloudy days and EQ charge maintenance, A Part Time or Occasional user like an RRV can do that at home with a standard AC powered battery charger.

[Sunking]

if I chose to go with a 6v system persay 225ah, that would be 450 ah of power correct?

No, some of your noodles still do not have butter on them yet.

Amp Hours is NOT POWER. Without a voltage specified AH means nothing by itself. Mathematically:

Amp Hours = Amps x Hours

Example if a load uses 5 amps for 10 hours it uses; 5 amps x 10 hours = 50 amp hours.

So how much power and energy is that? The question cannot be answered without knowing the voltage. Now if the voltage was 12 volts, then I can tell you:

12 volts x 5 amps = 60 watts of power.
60 watts x 10 hours = 600 watt hours of energy, or 12 volts x 10 hours x 5 amps = 600 watt hours of energy.

Make sure you know the difference between Power and Energy. Power or Watts is the rate in which energy is either being consumed or produced , Energy is the amount of work performed over a period of time.

Now back to your question. 6 V x 225 AH = 1350 watt hours.. For the same amount of energy at 12 volts is: 1350 wh / 12 volts = 112.5 AH. But here is an easier way to see the relationship. Lets use 3000 watt hours capacity be our common denominator. What are the Amp Hours required at various battery voltages.

3000 wh = 12 volts x 250 AH
3000 wh = 24 volts x 125 AH
3000 wh = 48 volts x 62.5 AH

As the voltage goes higher, amp hours go lower. That's the butter your noodles are missing.

Ill take a look look into that brand and see if I can get it anywhere around my area, only reason I was looking st the s550 and s290 is I get a very good deal on them and from what I have heard, read and you tell me they are very good battery's!

Rolls is good, Trojan is good, and US Battery are good. You asked for other recommendations, and I gave what you asked for. US Battery is good and should cost less than either Trojan or Rolls. Any of the three are good choices.

[littleharbor]

2 6 volt 225 Ah. batteries in series is 12 volt @ 225 Ah. Series wiring adds voltage, not amperage so you need 2 series wired strings to achieve both 12 volt and 450 Ah.

[UrbanElite]

You'll need 4, 225 Ah 6 volt batteries to achieve 450 Ah. @ 12 volt.

That's because you only use 50% of your battery correct?

ill have to look at the specs of the s290 and s550

[littleharbor]

You'll need 4, 225 Ah 6 volt batteries to achieve 450 Ah. @ 12 volt.

[UrbanElite]

Pardon me but that is what I have been trying to tell you from the start. Once you have completed your test with the fridge, you will have very accurate data to work with as the Fridge is the power hog, the rest is just minor. 300 Amp Hours.

Indeed you did, I just jumped the gun, it's very exciting you know, I'm sorry for that haha, with 300 amp hours, if I chose to go with a 6v system persay 225ah, that would be 450 ah of power correct?

Ill take a look look into that brand and see if I can get it anywhere around my area, only reason I was looking st the s550 and s290 is I get a very good deal on them and from what I have heard, read and you tell me they are very good battery's!

[Sunking]

Now back to the topic on hand, Like i said before I would like to be able to do 2 days of camping without power coming in from solar, as If I went out on a weekend and it wasn't very nice out I wouldn't have to worry about power all weekend, but if we were to go out for 4 days or so, and we could stay out there easy with 2 days of power, and if those days are nice the system will be keeping my batteries fully charged and every good day we had we just mean we could stay out a day longer too. I'm mostly doing 2-day trips, but there will be the odd 4-day trip I'm sure with my schedule.

So if we could keep the specs down a bit, I would like to save that money to put elsewhere in my trailer, or camping supplies. If I could stick with the 40A traccer MPPT, decent sized batteries and make it work to have a good system, that would for sure save myself money very fast.

Pardon me but that is what I have been trying to tell you from the start. Once you have completed your test with the fridge, you will have very accurate data to work with as the Fridge is the power hog, the rest is just minor fluff. Simple example let's say you measure the Fridge uses 1000 Watt Hours per day. Add 200 watt hours for the lights, gizmos, and fluff. If you want two days usable, you need to size the battery for 3 days. So 1200 Watt Hours x 3 = 3600 Watt Hour capacity battery. Required Amps Hours at 12 volts = 3600 wh / 12 volts = 300 Amp Hours.

I will give you another good battery manufacture to look at and see if available in your area. They are on about the same quality level as a Trojan RE Line or Rolls 4000 series. They are called US Battery and a direct competitor with Trojan. They make more 6-volt golf cart capacities than Trojan from 97 to 340 AH, and LR16 case from 360 to 380 AH. They even have a RE line up.They cost a little less than Trojan and considerably less than Rolls. They are the OEM for Yamaha Golf Carts, Trojan still rules EZ-Go and Club Car.

You are well on your way. Good luck

SK

[UrbanElite]

While I haven't ever used these they are a different alternative to drilling and bolting through your roof. I believe they mount with adhesive.

I know you can get some pretty strong adhesive, but I don't have a problem with drilling and mounting them to the roof cause it's there to stay and I don't have room to add more so I won't be moving them once they are mounted, but that would be a good alternative if you didn't want to drill

[littleharbor]

While I haven't ever used these they are a different alternative to drilling and bolting through your roof. I believe they mount with adhesive. Plastic solar roof mount.jpg