How long will a battery last? - Page 2 - Fiberglass RV


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Old 05-24-2016, 11:31 AM   #15
Raz
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I have said it before, and here it is again... I really like having my TriMetric TM-2030 battery monitor. It tracks my battery usage and helps me budget my power usage to get the most out of the battery and keep it well maintained (not over discharged). You can get an idea by doing the math on the power draw of various things, and how long they are in use. But thats just an estimate. The TM-2030 is easier and more accurate. (About $200 if you DIY install however).

PS. Reading voltage is not a great way to measure battery charge, largely because you want to know the state of charge when you are using the battery (or have used it recently). Using a hydrometer is the best way (and no doubt even better than the TM-2030), but its a PIA and you always run the risk of spilling acid.
We disagree here. These monitors were designed with large solar in mind. The smallest shunt is 100 amp. For folks using s single battery you are operating in the bottom 10% of the range. With a 1 millivolt per amp resolution accuracy at fractions of an amp, is doubtful. Unfortunately, when folks spend $200 on a battery monitor they wish to believe. Now folks that run an inverter, that's a different story. Still, spending $200 to get every ounce out of a $100 battery. There is a lot of snake oil on those solar sites.

After you charge with your panel a number of times you can get a pretty good idea how its going with a multimeter. Remember, they don't just read voltage. Raz
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Old 05-24-2016, 11:32 AM   #16
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New TVs (LED types) do not draw much power. I installed a 32" LED/HD Sony in my travel trailer...standard A/C powered. It only consumes 57 watts. I only watch it when plugged into campground electric or when my generator is running. I could run it off a simple 12volt inverter but television viewing is not that important to me. If you boondock a lot invest in a small inverter generator, they are quiet and will simplify your life. State campgrounds limit generator use to about two hours in AM and two hours in PM to keep the peace...most only permit quiet inverter type generators.
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Old 05-24-2016, 01:04 PM   #17
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We disagree here. These monitors were designed with large solar in mind. The smallest shunt is 100 amp. For folks using s single battery you are operating in the bottom 10% of the range. With a 1 millivolt per amp resolution accuracy at fractions of an amp, is doubtful. Unfortunately, when folks spend $200 on a battery monitor they wish to believe. Now folks that run an inverter, that's a different story. Still, spending $200 to get every ounce out of a $100 battery. There is a lot of snake oil on those solar sites.
..
While I do respect your opinion (because it is apparent that your really know this stuff), I think there is more science behind the Bogart Engineering products than most so I would not lump them in with the solar snake oil crowd.

But you got me wondering so I just now ran a little experiment. I put a digital multi-meter in series with a LED bulb, powered by a 12 VDC outlet in the Scamp.

The digital meter read 102.5 mA with the LED on.
The TM-2030 readings showed an increase of .09 (90 mA) filtered* and .11 (110 mA) instantaneous with the LED on.

Perhaps this margin of error at very low levels will add up, but will also be less with things like a 1.5 – 3 amp draw from a fan. Bogart makes this claim: “With 100A/100mV shunt 0.00-300 Amps, resolution 0.01 Amp. ±1% ± least significant digit.”

But accuracy and cost effectiveness aside, the thing I really like about is the convenience. Just push a button a few times and get all sorts of readings. I don’t regret buying it at all. It would be a good test to compare the TM-2030 value of percent battery charge against a hydrometer reading, but since I like convenience and hate acid burns , I will leave that for another time.

Second would be the knowledge that its about impossible for me to unexpectedly end up with a dead battery, especially while boondocking in the middle of nowhere.

Maybe I like it so much because I paired it with the SC-2030 solar charger. Just one of the things I like is that in this config it tells you when there is spare solar power available, and you know that you can charge phones, etc. without even drawing from the battery (or at least drawing less because it is supplemented with solar).

Actually I do have a issue with my setup. I cannot for the life of me get a good spec sheet on the battery. I had to take a sawg at the capacity and more than any other variable, that one probably limits the accuracy for me. The next battery will be from a manufacturer who provided decent documentation.
-----------------
Methodology notes:

Everything in the camper was off except for a propane detector (rated at 75 mA but not measured) and the TM-2030 which uses about 30 mA when display is on (according the published specs).

The TM-2030 readings with the LED on were .21 and .20 (with the two values alternating but more often on .21). The filtered value was .20 (200 mA). With the LED off the reading was .10 but the filtered value was .11.

* Filtered values are an “average value” taken over 140 seconds and the figure used by the monitor to avoid monetary fluctuations in the data. For my measuring I allowed for five minutes with the LED both on and off before reading the filtered value.
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Old 05-24-2016, 02:25 PM   #18
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There are lots of very clever people doing very clever things. I'm sure some work for Bogart. My point is that the single battery RV market is not their target audience. While to monitor the charging of a battery all you really need is a multimeter you seem to be having fun building a system and learning a lot. I'm sure you won't let me discourage you. When I was teaching I would set up 5 very expensive meters all measuring the same source. All would read slightly different. Electrical is the sloppiest of the engineering disciplines.
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Old 05-24-2016, 02:48 PM   #19
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we got a deep cycle gel cell lasts a lot longer than old deep cycle batter was worth the extra cost, it has no holes can be mounted on side even no fumes
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Old 05-24-2016, 03:07 PM   #20
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There are lots of very clever people doing very clever things. I'm sure some work for Bogart. My point is that the single battery RV market is not their target audience. While to monitor the charging of a battery all you really need is a multimeter you seem to be having fun building a system and learning a lot. I'm sure you won't let me discourage you. When I was teaching I would set up 5 very expensive meters all measuring the same source. All would read slightly different. Electrical is the sloppiest of the engineering disciplines.
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
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Old 05-24-2016, 04:55 PM   #21
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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
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single battery RV market
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Old 05-24-2016, 05:37 PM   #22
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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.
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Old 05-29-2016, 01:29 PM   #23
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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


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Old 05-29-2016, 01:49 PM   #24
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nice unit Joe....

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
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Old 05-29-2016, 03:23 PM   #25
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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:


I have not received nor tested it.
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Old 05-29-2016, 03:25 PM   #26
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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)
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Old 05-29-2016, 11:43 PM   #27
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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.
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Old 06-12-2016, 12:28 AM   #28
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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.
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