How long will a battery last?

[Raz]

Originally Posted by gordon2

I get all your points and have no arugment with them.

But about targeting...(or perhaps I should call it marketing instead of targeting by design)

... while the products might not be designed primarily for the RV market, they did add the suffix "RV" to one of the models because it has a different box, meant to be surface mounted in a.. you guessed it... RV

Not RV market but

single battery RV market

.

[gordon2]

Originally Posted by Raz

Not RV market but .

'Ahh yes, I must have missed that.. so we can revisit this when I get my pair of golf cart batteries? Or not.. I think the horse is dead now.

Except I just got a 50 watt semi-bendable panel. Lots to discuss there. I know there are a lot of reasons not to use this type of panel and a lot of considerations if you do (I've done some homework) but I want to give it a try anyway. The light weight and mounting options drew me in. Again, the cost might not justify it (almost the same cost of the standard 100 watt poly panel for a 50 watt panel), but it will be fun to try it out.

[Joe Romas]

May I suggest something less expensive like under $10 like one of these?
I currently have a older version of one of these that you program your battery's amp hour rating and it keeps tract of your usage and gives a remaining life.
It also shows current usage in amps and gives current voltage.
also shows charging voltage when the converter is connected to shore power. It has two buttons and one shuts off the display.
Unlike most of these it has an internal shunt and I'm planning on getting a newer unit.
DC 0 600V 200A Voltmeter Ammeter LCD Panel Amp Digital Volt Gauge Meter 12V 24V | eBay

UPDATE: I just ordered A new one that has an external shunt along with remaining % of battery amp hours. It was $36 but the external shunt that can be by the battery gives more flexibility in mounting. My current one has same the same features but use an internal shunt.

http://www.ebay.com/itm/DC-0-90V-0-1...id=p5731.m3795


Joe

[Franswa]

I would have been tempted if I'd seen it earlier....

but as things stand now I find the 4 digit voltmeter gives me some/enough information as to the state of charge and also a pretty good idea (rough) of how many amps I'm "spending" using this or that....

when "all you got" is between 12.6-7 and 12.2.....two digits after the decimal point is a good thing

and pictures....just because I can.... (1997 BF 17C

[Carl V]

Here's what I went with:
Makerfire® High Precision G.T. Power RC Watt Meter and Power Analyzer 130 Amps - - Amazon.com



Displays actual volts, amps, watts.
Computes Ah, Wh
Memorizes amp peak, watt peak, min voltage.

This thing is designed mainly for RC enthusiasts, they use it to monitor their battery and motor performance. Maybe not for the RVer with large battery setups, but for single deep cycle users like me, it certainly does the job. Very popular monitoring tool among those using big solar arrays. Pretty good accuracy, as tested in this video:

https://www.youtube.com/watch?v=Lxv9Rozs774

I have not installed mine yet, but I did try it and it works just as advertised.
Virtually no significant difference with my digital multimeter.
I saw that the LED lights I'm replacing my halogen bulbs with will draw 120mA, versus 1.45A for the halogen.

And to monitor the AC side of things, I went with this:
5.5 x 3cm LCD 2-in-1 Dual-Display 3-Digital AC Voltmeter Ammeter Meter - Black (AC 80~300V) - Free Shipping - DealExtreme

I have not received nor tested it.

[gordon2]

Any meter that shows your power usage is better than just guessing. Any meter that shows your TOTAL power usage over some period of time is even better. And a meter that tracks power used and power replaced, both over some period of time, and tells you the net result, is better still. It comes down to budget many times, with convenience being an influence also.

(unless of course it is such cheap Chinese crap that it catches fire)

[Bluetang99]

Originally Posted by gordon2

Any meter that shows your power usage is better than just guessing. Any meter that shows your TOTAL power usage over some period of time is even better. And a meter that tracks power used and power replaced, both over some period of time, and tells you the net result, is better still. It comes down to budget many times, with convenience being an influence also.

(unless of course it is such cheap Chinese crap that it catches fire)

Yes I will definitely have to invest in one of those meters. I don't plan to boondock much but for the days we do decide to get a non powered site, the meter will be good too not have to be guessing how much battery we have left.

[Bluetang99]

Well so far this is what I came up with:
Reading light 250ma
Dinette light 850ma
Porch light 100ma
TV is 2.5 amps

Based on these i calculated roughly 4 amps. Right now I have a group 24 battery rated at 80 amp hours, but if I can only use 40 hours of that battery then I'm looking at approximately 10 hours of constant use if everything is on? If that's the case I'm hoping we don't get stuck in inclement weather all day and drain our battery in a few hours.

But realistically even if we have the TV and a light on for an hour or two a day it should last us a good couple of days. The battery has a 12 month replacement on it which is good.

[John in Michigan]

Rob,

Your battery capacity analysis is correct assuming:

(1) the amperage draws you listed are all at 12 volts DC
(2) you are discharging a lead acid battery down to 50% (12.1 volts resting)

-John

[gordon2]

Originally Posted by John in Michigan

Rob,

Your battery capacity analysis is correct assuming:
..

Except that you probably will not use the lights and TV as much as you figured (unless maybe you have a trailer full of people). I know you were looking at the worst case scenario (all day rain), but my 24 hour use in summer (as an example), would sometimes be as little as this:

One LED light for 1-2 hours: .5 - 1 AH
One smaller LED for 1 hour: .25 AH
Laptop (TV) 2 hours, dim screen: 4 AH
No porch light use or furnace, and assuming no fan use.
Total: 4.75 to 5.25 AHs, or about a week for your grp 24 battery.

I often substitute a tablet for the laptop, so that reduces the consumption even more. If I need the Fantastic Fan then that is around 1.5 amps, about the same as the electrical draw on a furnace, so that will draw down a battery much faster. A moderately sized solar panel can often keep up with this however and extend your time days or weeks (or more).

PS, Your Dinette light sounds high for a LED.. is this a double fixture? I have a double fixture over my stove and found that after taking one bulb out there was still plenty of light, and of course half the power draw.

[John in Michigan]

Rob,

I agree with Gordon that your dinette light power consumption estimate might be high. I use #1156 LEDs for interior lighting. They consume about 120 milliamps per bulb. Depends on what lighting products you are using.

I also agree with Gordon's comment that your actual consumption may be much lower than you assume. I have a 36 AH AGM battery. I only use lights a few hours per day and stretch battery power to 5 days. I tested my setup at home by starting with a fully charged battery, turning on lights a predetermined amount of time per day and running the propane detector 24 hours per day. I checked battery voltage each day for five days. I was able to confirm that the battery would last 5 days (staying above 50% charge). Then I went camping!

-John

[Bluetang99]

Originally Posted by gordon2

Except that you probably will not use the lights and TV as much as you figured (unless maybe you have a trailer full of people). I know you were looking at the worst case scenario (all day rain), but my 24 hour use in summer (as an example), would sometimes be as little as this:

One LED light for 1-2 hours: .5 - 1 AH
One smaller LED for 1 hour: .25 AH
Laptop (TV) 2 hours, dim screen: 4 AH
No porch light use or furnace, and assuming no fan use.
Total: 4.75 to 5.25 AHs, or about a week for your grp 24 battery.

I often substitute a tablet for the laptop, so that reduces the consumption even more. If I need the Fantastic Fan then that is around 1.5 amps, about the same as the electrical draw on a furnace, so that will draw down a battery much faster. A moderately sized solar panel can often keep up with this however and extend your time days or weeks (or more).

PS, Your Dinette light sounds high for a LED.. is this a double fixture? I have a double fixture over my stove and found that after taking one bulb out there was still plenty of light, and of course half the power draw.

That's what I got from the specifications at superbrightleds. It's a 21 1/2" led bar with 12 1 watt LEDs. It basically can be used as the main light for the camper as it lights up the whole trailer, but it doesn't need to be ran if I'm conserving battery.

The reading light I have installed is a multi chip led also and gives out plenty of light too at a much lower current draw.

[gordon2]

Originally Posted by Bluetang99

That's what I got from the specifications at superbrightleds. It's a 21 1/2" led bar with 12 1 watt LEDs. It basically can be used as the main light for the camper as it lights up the whole trailer, but it doesn't need to be ran if I'm conserving battery.
.

Silly me, I just assumed you were talking about a single replacement bulb. Thats not bad for light for the entire camper... sounds like something I have been thinking of doing.

[Bluetang99]

Originally Posted by gordon2

Silly me, I just assumed you were talking about a single replacement bulb. Thats not bad for light for the entire camper... sounds like something I have been thinking of doing.

No problem. My camper came without any electrical what so ever so everything had to be redone. I might add some of those rgb led strips to the ceiling at some point in time but just mainly for fun.

I will eventually get one of those stand alone 12v fantastic fans so that will eat up some battery too but so far the reviews say it's not bad on power.

[Uplander]

Think....GENERATOR....all problems solved.

[gordon2]

Originally Posted by Uplander

Think....GENERATOR....all problems solved.

Thats so true! One problem solved!


(and a lot more created).

[Gordon in Idaho]

Think...OVERBUILD...most problems solved.

I know...math can be fun. But trying to determine your daily electrical needs might be a daunting task. There are so many factors involved, that one day's usage is rarely the same as the last. My suggestion is to jump in and prepare for the most current draw that you can imagine, and then some more. Whatever you can fit and afford is what you should have. The initial investment isn't that great, and the freedom from worry is priceless. That said, I do check the volts, amps and hours often. Because it's fun.

If you really want to get economical, use dimmable LED's.
Don't run your furnace blower all night. Rig a handy switch that lets you turn it on as you need it (like 5 minutes before you emerge from your warm bed).
Don't use an inverter if you can help it. Most everything that you need can be operated on 12 volts.
If you use a 12v fridge, keep it as full as possible.
So, that's just my approach, and it's been successful. You should do whatever works for you. That's the beauty of having your own little playhouse.

Gordon

[Franswa]

Think...OVERBUILD...most problems solved.

The initial investment isn't that great, and the freedom from worry is priceless. That said, I do check the volts, amps and hours often. Because it's fun.

Don't run your furnace blower all night. Rig a handy switch that lets you turn it on as you need it (like 5 minutes before you emerge from your warm bed).

Don't use an inverter if you can help it. Most everything that you need can be operated on 12 volts.

You should do whatever works for you. That's the beauty of having your own little playhouse.

[Bluetang99]

Originally Posted by gordon2

Thats so true! One problem solved!


(and a lot more created).

For now if we kill the battery I will just use jumper cables to the car and run it for an hour. Maybe in the future we'll get solar or a generator.

It's crazy how much some places around me are charging for full hookups. Anywhere from almost $50 to $80, while a primitive site with no hookups is $20.

[Bluetang99]

Quick question for you electrical experts. If I want to install a voltmeter can I splice it into any 12v circuit or does it have to be installed between the battery and pd4045 fuse panel?