Inexpensive battery monitoring

[sternwake]

There are programmable amp hour counting battery monitors, like trimetric and victron and several others. All of these require all the ground cables pass through a large Shunt placed inbetween battery - and ALL loads or charging sources.

The Shunt is a precise resistor that drops voltage across it. The more voltage drops the more amperage.
Almost All these shunt based higher quality  battery monitors, up until recently, were in the 200+ dollar range.

This pricetag is enough to dissuade many.  Most can get by with a simply voltmeter and some regular observations of how the voltage drops during use and rises when charging.

For such minded people, i recommend a voltmeter with several decimal places, then they can turn on small loads like leds lights and see the voltage go from  say 12.678 to 12.675, see their compressor fridge fire up and voltaqge instantly drops from 12.678 to 12.467 and slowly drops while the compressor runs, when it shuts off voltage will rebound.  Pretty easy to get a general idea where the battery is at, and notice when it is either undercharged or underperforming.
https://www.ebay.com/itm/DC-0-33-000V-0-...SwnI9cZQIa

It is also nice to know the size/amperage of the DC load, or charging source affecting the battery voltage.

I have been using inline wattmeters, that have a load and source side, input and output side, and only read current flow in one direction.  Some of these have proven to be significantly less accurate than hoped, but are still useful especially when using the same meter to compare loads at different times. These wattmeters have many clones/versions and can be as low as 6.77$ slow boat from china or 70$ for the original 'watts up' wattmeter.

https://www.amazon.com/GT-Power-Analyzer-Consumption-Performance/dp/B00C1BZSYO/ref=sr_1_2?keywords=wattmeter&qid=1568623125&s=electronics&sr=1-2

https://www.ebay.com/itm/Digital-Monitor-LCD-Watt-Meter-60V-100A-DC-Ammeter-RC-Battery-Power-Amp-Analyzer/352603854530?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D40719%26meid%3Daf375f4c2d3446ee842386b1eefafa3b%26pid%3D100005%26rk%3D6%26rkt%3D12%26mehot%3Dag%26sd%3D123897808516%26itm%3D352603854530%26pmt%3D1%26noa%3D0%26pg%3D2047675&_trksid=p2047675.c100005.m1851

I put 45amp  anderson powerpoles in input and output and it makes it easy to hook inline on any charging source or load. i have started my engine through a pair of these wattmeters in parallel.
These wattmeters are imperfect, some way more accurate than others, some have been inaccurate junk.  Seems to be luck of the draw. Many of them seem inable to perform simple math. Like 1.42 amps for precisely an hour should read 1.42 Ah consumed/delivered, but some of these will instead read 1.62AH.

Some others read accurately, if one uses their own timer and not the timer on the wattmeter itself. I have one wattmeter that reads 55 minutes and 40 seconds when my stopwatch reads 60 minutes precisely.

So While I really like the Peak/surge amperage and wattage and minimum voltages that these wattmeters record, their amp hour and watt hour figures are to be taken with a grain of salt until verified with other ammeters voltmeters and a timer.

Shopping for a better easy to hook inline product I find nothing that fulfills all my desires, but my search revealed many other meters and battery monitor products. most of which are relatively inexpensive.

Some of these will not count amp hours(AH) or watt hours(WH) both into or out of the battery, and the product description might not make this clear.  Some of these use a shunt, some use a hall effect sensor which might or might not be large enough internal diameter to pass a single positive or negative battery cable.

Some of these battery monitors have bluetooth, and Wifi.  The bluetooth is so no wires have to go between the display and the shunt/hall effect sensor meter current measuring portion.

I know a lot of people want something telling them how much battery they have used like a fuel tank but the trimetric/victron, balmar smartgauge tyope of proiducts being 220+ dollars is unpalatable.

i have no experience with the products linked below, but I think the fact they products such as these have recently become available, and recent politics has not yet stopped their availability or affected their price, that members here might want to dabble with them.

Here is one product I just ordered, basically to put on the output of my Meanwell power supply for counting current in one direction.  I will provide more details when I set it up and use it.

https://www.ebay.com/itm/50A-100A-Voltag...Fx0ncyeQTA

This one is a bit larger and has a remote  thermocouple to read celcius remotely.
https://www.ebay.com/itm/DC300V-100A-Digital-Voltmeter-Ammeter-Volt-Meter-Battery-Capacity-Power-Tester-g/162851077490?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D40719%26meid%3Ddbe4f014831b40b392289b8cd1ef68a3%26pid%3D100005%26rk%3D3%26rkt%3D12%26sd%3D264288477006%26itm%3D162851077490%26pmt%3D1%26noa%3D0%26pg%3D2047675&_trksid=p2047675.c100005.m1851

https://www.ebay.com/itm/Power-Supply-Energy-tester-Charger-Ammeter-DC-Voltmeter-Current-Power-Meter/283606884878?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D40719%26meid%3Ddbe4f014831b40b392289b8cd1ef68a3%26pid%3D100005%26rk%3D12%26rkt%3D12%26sd%3D264288477006%26itm%3D283606884878%26pmt%3D1%26noa%3D0%26pg%3D2047675&_trksid=p2047675.c100005.m1851

https://www.ebay.com/itm/0-200V-LCD-Display-DC-Battery-Monitor-Voltmeter-Current-Tester-for-RV-Solar-Car/123897808516?epid=23033951229&_trkparms=ispr%3D1&hash=item1cd8e28684:g:8TIAAOSwC~tdXOev&enc=AQAEAAAB4BPxNw%2BVj6nta7CKEs3N0qWIjq1NpGNjLkE8HHsY67HERgXscJvF5IIjTMvgzeT9bSr8DwnopCk%2BdFzRrtpo3ZEkKPi2YEl0jyczOXCaNFh5sXhHOLKu4GbaD5AwgCR748ov9Ue4Qvya%2BhxQTpqTuSb9aHZ9l4fJy7XuWeVrm%2FAm1UOTH7Dgw%2B0m9xBB3AaQRicazdZ78sh9JuBkjO9Kk8D4%2FvaO4xh8lh85cDSj9WZHBVBqhREgNT54FQDcm6Ril3TSPdzbvVjvwEFU%2FZkt7n9s4hgGuqYK%2B1QjavWS3rUmrG1J2knlMj5hSbHZAvsztR2cNQPC106qL%2BISu1XzeRenQ%2BKr4In9h4NAJqO%2FgRrPWUfvRVVwkHSp3pKpalL0yodziVk74FUBIgg0JT0XKzkBQcZKmDuiggiPWokES%2B%2FjLKSm6%2BMJsL5kDbnqyir6vMxKlZPkYIpFmvcrmAJgDO7TuGBFjoiNn2dupnb%2BWUUmFlfeSPKpb5Ar8xKuGeaxOza6QqtrNuYhZOqBtodakDs2VQdzd6CwoXpFTqraaqCUTmtfOjb4w7ytnHl8i8OafHvcaqR%2BFGIPFsfCnV7QY2CzId5xZSL%2FsSoVXU0DlW6RxV9PgQLCirmGawNq7D9ulw%3D%3D&checksum=123897808516f23457a774284059b8967c20c21cea11

This one is more a battery monitor for counting current into and out of a battery.

https://www.ebay.com/itm/Wireless-Battery-Monitor-Meter-DC-120V-300A-VOLT-AMP-AH-SOC-Remaining-Capacity/173058142084?epid=16010907719&hash=item284b11af84:g:O-cAAOSwgmtaQ~wF

https://www.ebay.com/itm/300A-wireless-D...SwuINbTRYm

https://www.ebay.com/itm/DC-Digital-Volmeter-Ammeter-Multimeter-Voltage-Ampere-Watt-Coulomb-Capacity-NEW/173684369374?_trkparms=aid%3D333200%26algo%3DCOMP.MBE%26ao%3D1%26asc%3D40719%26meid%3D984885c6a0b64783802197b361b167a6%26pid%3D100008%26rk%3D2%26rkt%3D3%26sd%3D233279112702%26itm%3D173684369374%26pmt%3D1%26noa%3D0%26pg%3D2047675&_trksid=p2047675.c100008.m2219

https://www.aliexpress.com/item/32957990278.html?spm=a2g0o.productlist.0.0.77ca63f4cjPuLE&algo_pvid=e7350ecc-ba49-46e1-a1ac-9b1d1f10711a&algo_expid=e7350ecc-ba49-46e1-a1ac-9b1d1f10711a-1&btsid=8f60a152-701f-44f4-adf3-e2248c0e858e&ws_ab_test=searchweb0_0,searchweb201602_8,searchweb201603_52

https://www.aliexpress.com/item/32821731871.html?spm=a2g0o.productlist.0.0.77ca63f4cjPuLE&algo_pvid=e7350ecc-ba49-46e1-a1ac-9b1d1f10711a&algo_expid=e7350ecc-ba49-46e1-a1ac-9b1d1f10711a-0&btsid=8f60a152-701f-44f4-adf3-e2248c0e858e&ws_ab_test=searchweb0_0,searchweb201602_8,searchweb201603_52


Anyway a battery monitor no longer has to be a 200$+ investment.  None should be trusted to be 100% accurate, not even the 200+ dollar ones. I cannot vouch for the accuracy of the product links above but I would say greater than 85% when set up properly and reset regularly when the batteries are known to be truly fully charged.