Power usage?

[pyemaster]

Hey guys,

I'm looking to sort out my power arrangements for when I'm camping / in the bush. The plan is to get a decent 1000CCA dual purpose leisure battery to:

A) provide power for everyday camping in the evening (predominantly LED lighting, music and charging phone/tablet).

B) be used to start the truck should the main batteries ever go flat (they shouldn't).

My plan then is to charge the leisure battery each day through either a roof-mounted solar panel (if stationary on site), or a smart charger working through an inverter off the cigarette lighter (if driving during the day).

My issue is I have no idea how much my expected usage will take out of the battery each evening...

The 3 things it will be doing:

- Powering two of these for lighting (though they'll be on a dimmer switch, if that makes any difference??): https://www.amazon.co.uk/gp/aw/d/B01...=AVEFNIEDS5OE4

- Charging a portable Bluetooth speaker

- Charging a smartphone / tablet.

So (thanks for getting this far!) with the above needing a few hours of charge from the leisure battery each evening, how much energy will they collectively use, and with that in mind, what size leisure battery would I need?

Thanks guys!

Owen

 

[IdaSHO]

Hello Owen,

It doesnt sound like you have much need for 12V, however,

To get real numbers you will need to provide amp draw ratings for each device, amp hour battery capacity of each device, and how many hours of each day the system will see such draws.

Only then will you know exactly how many amp hours you are using.


Also, your link to the lighting doesnt seem to work.

 

[PIC4GOD]

I'll echo what IdaSHO said about getting a better understanding of you power needs based on AH rather than CCA. CCA means nothing when it comes to the intended purpose.

Your best bet is a deep-cycle battery that way it can be drained and charged without damage to the battery. I use mine for a fridge and various camera equipment and went with a 100AH battery that is charged with an ArkPak.

 

[jonyjoe101]

leds dont use much power, The ones I have on my van (supernight) uses about 2 amps and light up the rear of my van. tablets use about 2 amps or less and speaker also about 1 amps. It depends how long each night you will run your lights etc.

I myself have 2 agm batteries that I use, a kinetik khc2000 (102 ah) and a smaller fullriver ( 28 ah) both are powerful enough to crank over a v8 but I use them as house batteries, the fullriver is mainly a backup and is small enough that in a emergency can replaced the starting battery and be used there fulltime.

Just make sure you dont run your battery below 12.1 volts, thats usually 50 percent on a agm or flooded battery. 12.7 volts is full. The more times you go below 12.1, the less your battery will last.

My advice is get at least a 100ah agm if you have the space, it best to have too much power than not enough, you can power your lights all night long and it will still have power to jump you if you need it. But for your current needs a 50ah battery would be about right.

 

[pyemaster]

Thanks for your comments guys, just to clarify a few things, the Ah rating of the leisure battery I was looking at was 110, this I was hoping would be enough to provide LED lighting, charge a phone/tablet and power a small speaker for probably no more than around 4-5 hours per evening.

I mentioned the CCA figure for its (hopefully rare!) back-up use to start the 3ltr turbo diesel engine of my Hilux. The truck has two starting batteries as standard which together I believe give 700CCA normally.

This was the battery I was looking at - https://www.tayna.co.uk/Numax-CXV31MF-P3694.html

It mentions it is 'wet' technology, not sure if this is good or bad though?

The LED lights (hopefully a working link now) are these - http://www.amazon.com/Eyourlife-Waterproof-Driving-Lights-Spotlight/dp/B00Q81D1Q0

Verkstad, as regards solar charging on the move, nope, you're absolutely right, it could be trickle charged by solar when travelling too, I guess I mentioned the smart charger / inverter route as more an alternative option.

Jonyjoe, thanks for giving a rough idea of the amp draw for the items I've listed, is there a simple way of calculating amp draw ratings and amp hour battery capacities?

Thanks guys, I'm so easily confused with all this!

Owen

 

[ripperj]

Amps is current flow(movement of electron).

Volts is basically difference in charge(how positive or negative as referenced to something)

Amps X volts is power in watts

A auto battery has about 12v DC between the positive and negative posts, depending on its state of charge( full charged is 100%)

Amp-hours (your battery you say has 110) is amps(current) with respect to time. If you could actually go to zero without damage (can't even get close), your battery would put out 110amps for one hour, 55 amps for two etc.
Reality says you only want to get to about 1/2 your capacity. (depends on battery)

Idasho means you need to figure your loads in amps, and then how long you plan to run them in hours, and do the math to figure how many amp hours per day you will use.


This is a real quick overview and I don't have time now to give more detail, but I can check back tonight. Hopefully this will get you started
Some of your loads are small, 500mA is .5amps (.001 amp is one milli-amp)


Sent from my Passport

 

[pyemaster]

So on a rough calculation of:

Tablet / phone - 2 amps
2x 20w LED lights - 2 amps each (4 amps in total)
Speaker - 1 amp

7 amps total, running for max 6 hours per day.

Would this mean a total of 42 amp hours? (7 amps x 24 hours, divided by 4 to get the figure for 6 hours.)

If I have a 110 amp hour battery (and they don't like going down beyond 50%) this would mean I would have 55 amp hours to play with each day.

If my expected usage of 42 amp hours is then accurate, I should be okay as it would only be dropping a 110Ah battery down to around 60% of its capacity for each 6 hour period?

Owen

 

[DiploStrat]

Bad Idea!

My plan then is to charge the leisure battery each day through either a roof-mounted solar panel (if stationary on site), or a smart charger working through an inverter off the cigarette lighter (if driving during the day).

As noted - a properly set up solar charger will work when you are driving.

Your you may want to reconsider your other ideas. Assuming a 100Ah battery, down 50Ah every night, you will need on the order of 55-65Ah to recharge.

-- You won't get that from a cigarette lighter.

-- Worse, an inverter will lose around 10% of its capacity.

-- And if you don't use an inverter/charger, but rather an additional AC "smart" charger will lose at least another 10% converting back to DC.

Install a decent relay based system and a 75Ah charge will be easy whenever you drive. With lead acid batteries you will still want some form of solar charger to complete the long absorb stage. If you vehicle's charging system does not run at a high enough charging voltage, then look at battery to battery chargers by CTEK or Sterling Power.

 

[pyemaster]

Thank you for your reply, so if I'm to go down the CTEK charger route for charging the leisure directly off my car battery (when driving), would something like this be correct? It says it can handle up to 110ah batteries:

http://www.amazon.co.uk/CTEK-MXS-5-0-Temperature-Compensation/dp/B00FC42HAA?th=1&psc=1

Secondly, to recoup the circa 40amp hours I'll be potentially losing each evening the following day by solar, is there an easy calculation to work out what size panel I'd need?

Owen

 

[DiploStrat]

You are really moving into an area where you should do some serious research. Immodestly, I would suggest that you download a few of the documents from my website - they cover this in much detail and include links to other sites which cover this even more comprehensively. (Links in my Signature.)

That said:

-- Most modern vehicles already have fine battery chargers that run at the 14v+ needed for AGM or FLA batteries. Don't spend extra money on kit that you may not need. Chris Gibson has lots of good information here: http://www.smartgauge.co.uk (The UK narrowboat community spend a lot of time worrying about this stuff.) I use an intelligent (also known as a voltage sensing) relay on my truck. I like this one for smaller installations, but I am not sure you can get it in UK: https://www.bluesea.com/products/7610/SI-ACR_Automatic_Charging_Relay_-_12_24V_DC_120A Bluesea makes other models that include a switch for self-jump or cut out: https://www.bluesea.com/products/7620/ML-ACR_Automatic_Charging_Relay_-_12V_DC_500A Also available for 24v. Smartguage do the same thing with their SmartBank: http://www.smartgauge.co.uk/smartbank.html Readily available in UK

-- If you have determined that your vehicle's charging really cannot produce adequate voltage, then you may be in the market for a B2B, a battery to battery, or DC-DC charger. Sterling Power, also a UK company, have many models available: http://sterling-power.com/collections/battery-to-battery-chargers

-- I am rather partial to two CTEK products:

D250S Charger: http://www.amazon.co.uk/C-Tek-D250S...TF8&qid=1459516517&sr=1-1&keywords=CTEK+D250S

SmartPass Intelligent Relay: http://www.amazon.co.uk/C-Tek-Smart...TF8&qid=1459516517&sr=1-2&keywords=CTEK+D250S

The CTEK products are expensive, but they do several things:

-- The 20A D250S assures that the absorb stage reaches full voltage, even compensating for some voltage drop.
-- The D250S includes a small MPPT solar controller, which may obviate the need for a separate solar charger.
-- The SmartPass allows a direct relay connection, which boosts your charge rate during the bulk stage up over 80A. (Very nice) And, unlike most diode based B2B, it allows the solar charger to maintain your starter battery - very important if your vehicle sits between trips.

The usual rule of thumb is that you want 100w of solar for every 100Ah of battery. In full sun you can get just over 5A from a 100w panel. Expect less in cloudy Blighty, but remember that UK summer days are endless.

Final note: Remember to wire the whole mess up with appropriately sized cables; they won't be small.

Second Final Note: I don't know most of the brands on your battery site, but I use Lifeline AGM batteries. They are way more expensive, but they are true, deep cycle batteries and stand up to the heavy use of air conditioning and induction cooktops.

Hope this helps a bit. None of this is hard, but it can get a bit complex. The good news is that if done correctly, you can basically forget about things and simply let the magic happen.

 

[pyemaster]

Thank you so much for your lengthy post, this is a great community.

I will start to try and get my head around some of this, I'm unsure to what end I'll need/not need some of the things you mention, but will keep doing my homework.

I think the last time we saw a full day's sun was in about 1998.

Owen

 

[DiploStrat]

...

I think the last time we saw a full day's sun was in about 1998.

Owen

I've seen it both ways. Have a wedding in Devon this July, so I am packing sunshine, just to be safe.

A neighbor of yours in High Wycombe has a very nice, small solar set up on his truck camper. You might reach out to him for real world advice for the UK. Start here: http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/25777668.cfm

 

[pyemaster]

Great I'll check that thread out, thank you. If you'd like any local advice on your trip in the summer let me know, very happy to give you a few tips!

Owen

 

[DiploStrat]

Thank you. We are spending the first night in Andover (member of the party has never seen Stonehenge) to recover from the flight. The rest of the time is with family in Devon. (Arrrrh!)

 

[pyemaster]

Okay so forgive my maths, but if a tablet/phone draws 2 amps, two 20W LED lights 4 amps and a portable speaker 1 amp (7 amps in total), this total multiplied by 12V (because it's a 12V battery) equals 84W. This, multiplied by 6 hours (maximum time used per evening) amounts to 504 watt hours?

So this would take a 120w solar panel 4.2 hours to charge this amount? Can it be as simple as that or am I totally way out / missing something!

Owen