power meter in Scamp

[ourscamp]

Has anyone put a Power Meter in their 13 ft Scamp? Is it worth the effort to just monitor the battery Voltage?
Thanks!

[cdamen]

I installed a voltage monitor right on the top of the battery cover. The gauge is water proof . Just drill hole the correct size and mount it up tight. I used protected spade connectors if I want to disconnect. Now every time I walk by the front of my Scamp I can see what my voltage is. The meeter was purchased thru ebay for $9.00.

[stevebaz]

I have a couple of cigerrette like power sockets in my trailer. I use a push in digital voltage meter when I want to check battery charge. That works fine for me, but I have only one battery to deal with and 2 small solar panels to fill the charge when not hooked up to AC power. I check battery charge in the morning and again when the solar runs out of daylight. I just have to know daily if my solar is keeping up.

[lisantica]

I don't have one yet, but I certainly want to get one.
Just today I was charging the battery with my solar panel and thought it would be nice to have one of those gauges.

[gordon2]

If you are going to use only voltage to read the state of charge of your battery you should do it correctly. It is still not the best way but its better than nothing. One of the problems with only reading voltage it that you must not use the battery at all for some time to get an accurate reading (unless you have way to do load testing), and who does not want to use your battery for hours just to get a fair measurement? It kind of defeats the purpose of having the battery. My preference is to use a recording amp meter that reads current going in to and out of the battery through a shunt.

One of the standard essays that we refer people to is:
The 12volt Side of Life (Part 1)
See the "Testing your batteries" section.

[Franswa]

a recording amp meter is the best/accurate way to monitor battery voltage/use...

but without going to that expense/complexity a volt meter is a good place to start understanding what is happening to your system as you use and create power from your solar system

unfortunately a three digit panel meter will give you very limited information...I very much recommend doing a little more searching and finding a FOUR digit panel meter. I have used both and the amount of information you can get from a 4 compared to a 3 is almost like "night and day"...you can "see" if you're gaining or losing and how fast....

also with a four you can see when the voltage stabilizes (giving you your state of charge) after shutting off a substantial power draw...and that only takes a few minutes...not hours...

doesn't cost very much more....just harder to find/source

a recording amp meter used to be on my wish list but after using the 4 digit meter for two seasons and getting used to how it behaves/works I am not going to bother....I have all the information I need...for me anyways

once I got a 4 digit meter I reused the 3 digit by putting it on the panel circuit (between the panels and the controller)....it turns out to be pretty handy there...but that's another story

[Franswa]

also with a four you can see when the voltage stabilizes (giving you your state of charge) after shutting off a substantial power draw.

after shutting off a substantial power draw...OR a substantial power generator (your panels or battery charger)

[lisantica]

Would this product be adequate?
https://www.amazon.com/gp/product/B0...f_rd_i=desktop

[Franswa]

I'll say !!! that thing is beautiful....measures use (amps)....and the shunt is built in.....I'm impressed

it's a huge step up from the 4 digit voltmeter I was suggesting.....

(46 bucks in canada...I might have to get one)

[Franswa]

46 bucks was for TWO !!!....LOL

[lisantica]

I think I am going to order it, the 20Amp one. They have other Amp ones, hope this is the right one.
I will need to order wire too, correct?
Do you know which gauge of wire to order?

[gordon2]

Originally Posted by lisantica

Would this product be adequate?
https://www.amazon.com/gp/product/B0...f_rd_i=desktop

Assuming that your Scamp has a 20 amp fuse at the battery then the wiring should all be rated for at least 20 amps, so the 20 amp meter with built in shunt should be OK. The 50 amp version gives you some safety margin on current capacity and more importantly, the shunt is separate which makes it easier to install and perhaps even safer. Apparently the 20 amp version only accepts up to 12 gauge wire so if you want to use 10 it wont work but I am guessing 10 gauge wire on the 50 amp shunt would be no problem. And the 50 amp meter comes programmed for the 100 amp shunt so you have to enter the new value into the meter or it will read incorrectly.

Apparently these meters only measure load and not charge. So you can know how much power is coming out of the battery but not how much is going back in. If you start with a fully charged battery and are using your battery with no charging source then you can track how discharged it gets with a reasonable degree of accuracy, but once you start charging (from converter, tow veh, etc) you will have to go back to basic voltage measurement to estimate the state of charge (with all the requirements and limitations that entails). The (quite a bit more expensive) Trimetric meter reads and records current in both directions and displays the state of battery charge as a percentage (among other information). You get what you pay for.

I would be concerned about the quality of this item from China but face it, everything now days is from China and the reviews are quite good. There are some negative comments about the quality. Some seem to be product defects but a few are people who don't know what they are doing.

And yes, you will need wire, connectors, perhaps addition fuse(s). This is not something that should be installed by someone who is not familiar with safe RV-DC wiring practices.

[gordon2]

Perhaps something like this might be better since it reads current in both directions:
https://www.amazon.com/DROK-Multimet...ews/B01M5CWR2P
But the reviews are not as good, and apparently the meter adds a noticeable parasitic load on the system (one comment was 1/2 amp!) - maybe the screen is always on. I provide that link only as a place to start looking for better options of which there are many.

[Carl V]

I installed this one in my trailer:
G.T.Power Watt Meter & Power Analyzer for RC Helicopter - Black - Free Shipping - DealExtreme
Amazon also sells it but DX was much cheaper.
Very accurate, you can look it up on Youtube.
Only measures power in one direction (discharge OR recharge).

[gordon2]

Originally Posted by Carl V

..
Only measures power in one direction (discharge OR recharge).

Yes I should have said that and not load only (even though that is almost always the way it is used in an RV). So you can get two and have one measure discharge and the other measure charging. And as a bonus, you also get twice the parasitic load and loss.

[Franswa]

that looks really good....but, man!, I'm having a little trouble understanding how I would be wiring this thing in and not blow anything up (meter probably).....given my technical knowledge (minimal to none when we get to measuring instrumentation)....

would be really nice though...and at a very good price to boot !! I'll have to think about it....

[lisantica]

Originally Posted by Carl V

I installed this one in my trailer:
G.T.Power Watt Meter & Power Analyzer for RC Helicopter - Black - Free Shipping - DealExtreme
Amazon also sells it but DX was much cheaper.
Very accurate, you can look it up on Youtube.
Only measures power in one direction (discharge OR recharge).

Thank you for posting about this product, it gets some very good reviews on YouTube, I have one in route.

[Carl V]

It can also be panel mounted if you remove the internals from the plastic case, which is what I did.
The true purpose of this meter is to monitor battery performance for RC models, it is very popular with the RC crowd. There are many other meters based on the same logic board, and this file will give you a lot of info on how to use it, wire it, or even modify it:
http://www.rc-electronics-usa.com/do...ser_manual.pdf
Main link: "Watt's Up" Watt Meter and DC Amp Meter Support & Downloads

[lisantica]

Thank you Carl V. Good information!

[Franswa]

thanks a bunch for the additional info in the VERY GOOD link....it convinced me to pull the trigger.....I already had an account with DX...used them before.....and it was so cheap, I ordered TWO!.....LOL

as far as measuring only from one side....I don't think that will be much of an issue.....as long as I have battery voltage I'll have my state of charge (with batteries "at rest")....how fast the batteries are being charged is not a big concern to me

thanks again....I owe you a beer....F