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87 Oddy

Accuracy of Battery Meters

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Does anyone have any Insight as to which particular battery monitor will give you accurate ah, time remaining, % charge, etc. Without spending 300$ for the xantrex battery monitor?

 

Also will this 35$ one work just as well?

Any info will be helpful, I enjoy this aspect of toyotahome performance upgrades so I will spend the $ if necessary but 300$ is to much for me...

Screenshot_20191022-033310.png

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Bit of over kill a nice volt meter would tell you all you need to know.

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I have an LED one that I purchased on eBay for like $15 and works just fine.  I have a Renogy Wanderer solar charge controller with bluetooth and an iPhone app and when I check battery charge using that, it always shows the same voltage as my $15 eBay volt meter, so....

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I plan on doing some extended boondocking so I need to know things like ah remaining, percent of charge, time remaining a current consumption. 

Is there a battery monitor that will show these things accurately for 50$ or less?

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Which of the parameters that you list is not met by the one in the photo you posted above?

BTW, can you share the make and model?

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8 hours ago, 87 Oddy said:

Is there a battery monitor that will show these things accurately for 50$ or less?

I installed a $25 battery monitor and it's been working great for me.  Here's a link to one like the one  I have:

https://www.ebay.com/itm/161129449019

Looks like this:

image.png.52d11158f2b2d9da57f9f43a81e4365f.png

Mine came with a 100A shunt.  With these cheap meters you have to make sure it can actually measure/use both charge and discharge current.  Some only measure discharge and they are not very accurate.  (there are meters very similar to the one I have without the "charging" label/indicator - don't buy one of those).  I've been very pleased with mine and I did test the accuracy of the volt meter and current meter and for a $25 it's dang close to correct.  Perfectly fine for RV use. 

Install is not simple as you have to do the wiring correctly and add the shunt in the correct place to make it work.  Instructions that came with it are bad but I found some better ones online.  It's not rocket science to use but you do have to take the time to learn how to calibrate it.  Periodically you have to reset it to be 100% at fully charged.  All that said I find it to be very handy to monitor the battery and read out the current I'm using with individual appliances.    It not only tells you how your battery is doing but it helps you ID the devices that are draining it too.    

I think the key to finding one that would be functional on the cheap is to make sure it includes a shunt (100A is good), measures both positive and negative (charge and discharge) current and has some decent reviews.  For example the one WME linked to seems to fit the bill and I suspect that it will work fine for him when he hooks it all up.

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10 hours ago, 87 Oddy said:

I plan on doing some extended boondocking so I need to know things like ah remaining, percent of charge, time remaining a current consumption. 

Is there a battery monitor that will show these things accurately for 50$ or less?

Yes voltage will tell you % of charge the other are too variable to be accurate.

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On 10/27/2019 at 6:33 AM, Derek up North said:

Which of the parameters that you list is not met by the one in the photo you posted above?

BTW, can you share the make and model?

No it appears to have them all. That's why I used it as an example of what I need for under 50$. My question is will it be accurate. And what's the difference between that and a 200$ monitor?

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On 10/27/2019 at 12:24 PM, AtlantaCamper said:

I installed a $25 battery monitor and it's been working great for me.  Here's a link to one like the one  I have:

https://www.ebay.com/itm/161129449019

Looks like this:

image.png.52d11158f2b2d9da57f9f43a81e4365f.png

Mine came with a 100A shunt.  With these cheap meters you have to make sure it can actually measure/use both charge and discharge current.  Some only measure discharge and they are not very accurate.  (there are meters very similar to the one I have without the "charging" label/indicator - don't buy one of those).  I've been very pleased with mine and I did test the accuracy of the volt meter and current meter and for a $25 it's dang close to correct.  Perfectly fine for RV use. 

Install is not simple as you have to do the wiring correctly and add the shunt in the correct place to make it work.  Instructions that came with it are bad but I found some better ones online.  It's not rocket science to use but you do have to take the time to learn how to calibrate it.  Periodically you have to reset it to be 100% at fully charged.  All that said I find it to be very handy to monitor the battery and read out the current I'm using with individual appliances.    It not only tells you how your battery is doing but it helps you ID the devices that are draining it too.    

I think the key to finding one that would be functional on the cheap is to make sure it includes a shunt (100A is good), measures both positive and negative (charge and discharge) current and has some decent reviews.  For example the one WME linked to seems to fit the bill and I suspect that it will work fine for him when he hooks it all up.

Good recommendations. I have looked at the monitor you posted a pic of and it looks like it would do what I want, it's just so cheap is why I hesitated.

Here's the one Ive decided on. It's brand new from Renogy, I've had nothing but good experiences with them, I had the 200watt solar starter kit on the 87 Oddysey, and im now running their 2000 watt pure sine wave Inverter in the 91 Warrior. It's 89$ on eBay.

Screenshot_20191108-040747.png

Screenshot_20191108-040755.png

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Also on a side note... My battery bank has gotten out of control in the toyotahome! Im obsessed with how long and how well I can boondock it. I've currently got 4 225ah 6v batteries in series parallel hooked on series with 2 140ah 12v batteries for a total of 6 batteries @ 730ah!

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What in the world are you using that needs that much current in a tiny motorhome?  How big a hit did you take on fuel usage?

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Wow close to 400 LB of batteries. I often then go a week or more with no power with 2 Group 24's and a 100 watt panel never had low batteries even when it rains. Replace all of the lights with LED's put an accumulator on the pump, use the stove to cook not a microwave make coffee the same way turn the heat down, a tiny 150 watt inverter will run a computer and charge a phone at the same time etc. Even run a small flat screen TV. You can store a lot more energy in a 20 propane tank than 10 batteries. 

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On 11/9/2019 at 6:03 AM, Maineah said:

Wow close to 400 LB of batteries. I often then go a week or more with no power with 2 Group 24's and a 100 watt panel never had low batteries even when it rains. Replace all of the lights with LED's put an accumulator on the pump, use the stove to cook not a microwave make coffee the same way turn the heat down, a tiny 150 watt inverter will run a computer and charge a phone at the same time etc. Even run a small flat screen TV. You can store a lot more energy in a 20 propane tank than 10 batteries. 

You make a valid point about the energy in propane. Im just experimenting for the first time with off grid power production, storage, and monitoring there of. And im enjoying it!

 

I've got 4 of these 6 volt = 450AH

 

And 2 of these 12 volt= 280AH

My house converter/charger is the PG 4645 which puts out 45 amps charging, although I've noticed on my surge protector that it's pulling 10 amps from shore power. Does that sound correct? Obviously it can't pull 45 amps from a 20 amp shore circuit I guess it must amplify the charge somehow. I'd love to know how much the batteries are taking in at any one minute. 730 AH/45 amp = 16.2 hrs to charge the whole bank! Im aware that's not how it works and would take longer to get to 100%. That's why I need a good solar setup. Right now I try and run the Predator 2000 2-3 hrs. each day to keep the voltage between 12.2-12.8.

Screenshot_20191108-170145.png

Screenshot_20191115-225936.png

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Mind you the converter is a factor of about 10 so a 10 amp 12 volt load translates to 1 amp AC 120 volt load.

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6 hours ago, Maineah said:

Battery charge chart

I have not found a simple voltage reading to be a reliable way to determine the state of charge.  In my experience this chart is only relevant if the battery is at a state of equilibrium, which of course it never is when you want to measure it. The chart works fine if you always let the battery sit for an hour or so before reading though...  If you charge and then immediately measure, it's an artificially high reading. If you have a heavy draw and then read, it's artificially low.  It's a fine way to get a really general estimate but I prefer the current reading via shunt battery monitor as it is really accurate regardless of draw or equilibrium.  Only issue with these is that you have to calibrate and reset the 'full' reading periodically.   

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Batteries will have a static or float charge it can be high13+ but once it is loaded it will (if the battery is good) drop back to 12.7 quickly  that being a fully charged battery from there it's voltage will drop as the charge is consumed. A good battery will rebound once the load is dropped how far it does is the state of charge. A shunt is used as a current draw device not voltage. No current draw no reading unless it is a load. I often refer to them as toasters because it is a classic resistive load. It is a good test of a battery that's suspect but in general use voltage is all you need.

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