Solutions for camping power? which battery/charging method?

[Silver_pig_gq]

Hi all,
Just trying to figure out the best battery/charging method to use on a two week camping trip coming up. below is what i could gather from what ive read on the internet, just wondering if i have it right?

So.... to work out total amperage usage per day>

1. evakool fridge drawing 2 amps/hour for 24 hours (will be turning it off overnight)
= 2x24 = 24 amps

2. portable 12v boombox drawing 5 amps/hour when turned up loud for 5 hours +
3 amps/hours when on low volume for 10 hours
= (5x5)+(3x10) = 55 amps

3. Two inverted camping fluros drawing 1.8 amps/hour each for 6 hours a night
= (6x1.8 )x2 = 22amps

SO, total amperage usage per day is 24+55+22 = 101 A/H's.

The battery i will have is an optima d31a which claims to have 75 usable amphours and i was planning to have either a solar panel or generator running a battery charger putting 10 amps an hour into the battery. so if i run the charging method (solar or genie) for 10 hours a day ill have 100ah's being put back into the battery.

My main question is with 101 A/H's of draw per day, is that going to damage a battery with a total capacity of only 75 A/H's? even if i have the charger hooked up to it?

or am i better having two batteries with a total usage of 150 A/H's so i can safely draw the full days usage out of the batteries and not drain them completely?

also is there another form of charging better then a 200watt solar panel which only works when its sunny or a noisy generator?

[DamTriton]

Go the two bateries if the stated AH of the battery is a useable 75.

Normally not all of the stated AH of the batteries is available for use, ie a 100 AH battery is only really good for ~60 AH in real use, and attempting to wring the last bit of energy from the battery past that point shortends the useable life of the battery (number of charge-discharge cycles).

Look at going LED for lights as they are a lot lighter on the power requirements. A 3 watt LED is about as bright as a 20 watt incandescent light or 8 watt flouro.

[mike_nofx]

Just think out loud here (well... in text)

But why switch off the fridge? The fridge compressor will cut in and out to maintain temperature, so its not constantly pulling amps. Switching it off over night will make the temp increase from say 3deg to 6-7deg and when you turn the fridge back on it will pull full amps to cool back down, possibly losing any benifits from switching it off.

I have a 35L waeco which i run off a century deep cycle (75ah i think) and it runs for 4 days easy. With a solar panel i reckon it could run basically forever.

As for stereo and lighting, why not a battery stereo? sounds like your current stereo uses too much power for a camp trip?

and led lighting?

[Silver_pig_gq]

Ive never been a fan of LED lighting due to it being voltage depended. i.e as soon as the battery falls below fully charged they start to dim, whereas fluros (as long as there started) stay bright untill theres simply no juice left in the battery. plus ive allready spend 200 bucks on camping fluros! I was planning on using an optima battery as the heart of the system, mainly because they claim a 75ah capacity and you can fully discharge the battery without damaging it. but if you guys are suggesting two batteries to have more then the required A/H's per day in reserve then maybe one good battery isnt the best option. i can get 105A/H lead acid deep cycles for 150 bucks new, should i just grab two of those for a combined A/H of 210?, which leaves me with 105A/H's + (if you use the state of discharge as 50%.)

[Silver_pig_gq]

Oh and the turning the fridge off i figured would work out better for consumption. as it draws 2 amps an hour overnight (total 10 to 12 hours, work on 10) thats a saving of 20AH's overnight then when i turn it on the most it would draw on the normal cycle (3000rpm) is 2.8 AH's and would only take maybe 2 hours to get it back down to temp so in theory only using .8ah's x 2 (1.6) more (as it would be running normally for the first two hours regardless if i turned it off or not), saving me 18.4amps. Are my calculations wrong?
and the stereo is pretty much a car headdeck knocked together in a mdf box with a set of speakers, and i Cant go without my beats!

[DamTriton]

Ive never been a fan of LED lighting due to it being voltage depended. i.e as soon as the battery falls below fully charged they start to dim, whereas fluros (as long as there started) stay bright untill theres simply no juice left in the battery. plus ive allready spend 200 bucks on camping fluros! I was planning on using an optima battery as the heart of the system, mainly because they claim a 75ah capacity and you can fully discharge the battery without damaging it. but if you guys are suggesting two batteries to have more then the required A/H's per day in reserve then maybe one good battery isnt the best option. i can get 105A/H lead acid deep cycles for 150 bucks new, should i just grab two of those for a combined A/H of 210?, which leaves me with 105A/H's + (if you use the state of discharge as 50%.)

Most LED panel lights and even a lot of single LED's come with a switchmode regulator (techie term) to drive the LEDs that drives them, and these effectively iron out the voltage going into the LED so it is run at full efficiency. This accounts for most premade panels accepting a large voltage range input (typ 9-28V) without loss of light output (actually an issue to design around if you WANT to dim them), and why even LED torches will not dim until the very end of battery life.

[drivesafe]

Hi silver, is there any specific reason for using Optima batteries?

If there is the option to use other types of batteries, for a lot less money you could add a 100 Ah battery ( of any type ) and give yourself a larger bank.

There is a problem with any increase although it may not cause you any inconvenience, the more capacity you have AND USE, the longer you need to run your generator.

[fatassgq]

What drivesafe has said is exactly right and catches a lot of people out.

I have found for most 4wding camping in the weekend to week range a 100ah agm or thereabouts is best. Too much amp hrs and you think 'wow this is great I can run all my gear for ages without recharging.' Then when time comes to recharge you are stuck as the alternator will never put enough back into a large bank (especially wet cell style) and if the sun ain't up you are not putting charge in with a panel and you can only carry so much fuel for your geny.... and that is if you are even allowed to use it where you are or the neighbours don't crack it over the noise.

AGM's seem to accept charge a bit better(faster) than most deep cycle style batteries and are not as sensitive as gels.

jmo

[drivesafe]

Hi jmo, when charging with an alternator, there is an advantage to using some types of AGMs, and silver’s Optima is by far one of the best batteries for rapid charging and can be charged with everything available from an alternator. You do have to be careful though, most AGMs, like Fullriver AGMs, are actually current limited, for both charging and discharging.

BUT, when using an battery charger or solar panels, there is no advantage, because there is a limited current available while charging, and AGMs will charge no quicker than good old fashion flooded wet cell deep cycle batteries.

[Silver_pig_gq]

My reasoning behind choosing an optima is pretty much because of ONE: the warranty (2 years) and TWO: so far to my research they are the biggest deep cycle (75 ah) i can get the still fits a standard N70ZZ battery tray.

BUT.... lately ive been confused by alot of battery mobs i ring about the SOD or state of discharge of a battery. optima states you can take 100% out of there battery (75ah) and i thought everything else you could only take 50% before causing damage. but opon asking, ive been told you can discharge a battery to anywhere between 15% to 75% SOD.

so if the optima reps reckon i can get 75 usable ahs out of there battery its worth while getting, if (at 50% SOD) a standard 105 ah wet cell will only leave me with 52.5 usable ahs. BUT, if i use the sod as 15% (as ive been told by at least two battery shops around brisbane) i can get 89 uable ahs out of the wet cell, meaning i get more then the optima.

Does anyone know the correct State of discharge for a sealed wet cell type battery AND a sealed agm or similar?

[Silver_pig_gq]

woops..... i mean Depth of discharge (DOD).

[drivesafe]

Hi silver, there are different safe depths of discharge for different types of batteries and just to confuse the issue further, there are different safe depths of discharge for the same battery, depending on intended use.

I’ll give you a rough idea of what I mean.

All batteries will supply the maximum amount of energy over their life span if you cycle them to around 65% SoC.

If you live in the back of beyond and depend on batteries for your main power supply and have banks of them then cycling them to 65% State of Charge ( SoC ) everyday will give you years of use from each battery.

This type of use is fine if you use your batteries EVERYDAY.

If you go camping every weekend then you need to keep the cycle rate at no lower than 50% and again you will get many years of use from your battery.

If you only go out once a month, the same battery can be cycled to 30% SoC and will still give you many years of use.

Silver, do you get the picture. The more often you use your battery, the less power you should draw from it.

Now while you can cycle an optima to 0% SoC it will still shorten it’s life.

Whereas, with a flooded wet cell battery, just cycling once or twice to 0% could stuff the battery but by using a bigger flooded wet cell battery, say a 120 Ah and only cycling it to 40% SoC, your will probably get more years out of it than you will out of an Optima which is continually cycled to 0% and the 120 Ah flooded wet cell battery will be heaps cheaper.

It all comes back to how often you plan to use your set up.