Monitoring batteries without current sensors?

[Ken Cross]

Is it possible to monitor battery state of charge without a current sensor? I currently just monitor voltage (down to .01 volt resolution) but I've not seen a battery monitor system that doesn't measure current. Here's one:

http://www.defender.com/product3.jsp?path=-1|328|2289954|2289950&id=2388351

Ken

 

[LeslieTroyer]

Maine Sail has a write up on the Balmar Smartgauge. My takeaway is he thinks they are much better for casual boaters than the coulomb counters that are out there. They are also available on his store - marinehowto.com

Les

 

[Maine Sail]

Is it possible to monitor battery state of charge without a current sensor? I currently just monitor voltage (down to .01 volt resolution) but I've not seen a battery monitor system that doesn't measure current. Here's one:

http://www.defender.com/product3.jsp?path=-1|328|2289954|2289950&id=2388351

Ken

The SmartGauge is actually quite accurate for SOC but does not give you any information other than SOC and voltage:
SmartGauge Testing & Evaluation
https://marinehowto.com/smart-gauge-battery-monitoring-unit/
Typical shunt based Ah counters are far tougher to keep accurate than most people think, thus they are rarely, if ever, accurate for SOC but give you lots of other useful information.
Making Your Battery Monitor More Accurate

 

[Benny17441]

It is possible. Understand that battery monitors can be necessary for a boat running sophisticated electronics. You would want to protect those units and the expensive batteries as well, but for the average coastal cruiser in a 20+ year old boats running OEM electronics with a basic battery bank learning to read a digital voltmeter is all that may be necessary. When I say learning to read a voltmeter I mean learning to interpret what a particular reading represents under a given situation. Learning many times requires comparing a reading to previous ones taken in similar situations. It also requires an understanding of how batteries work. Taking voltage readings of a battery that is not at rest will yield skewed readings but if we know what is happening we can compensate and come to a "good enough" voltage figure for our purpose. Using your mind and your memory you can quickly and rather adequately adjust voltage figures to a very useful level; it can at a glance alert to a problem. The method requires practice to maintain mental capacity and agility. "if you don't use it you loose it"

 

[Sumner]

....Taking voltage readings of a battery that is not at rest will yield skewed readings but if we know what is happening we can compensate and come to a "good enough" voltage figure for our purpose. Using your mind and your memory you can quickly and rather adequately adjust voltage figures to a very useful level; it can at a glance alert to a problem. ...

Has worked fine for me on our trips...

The top meter here is amps in tenths and the bottom is volts in tenths.

Sumner
==============================================================
1300 miles to The Bahamas and Back in the Mac...
Endeavour 37 Mods...
MacGregor 26-S Mods...http://purplesagetradingpost.com/sumner/endeavour-main/endeavour-index.html
Mac Trips to Utah, Idaho, Wyoming, Canada, Florida, Bahamas

 

[Crazy Dave Condon]

In layman's terms to see how the battery is holding up, first look at how old it is. Secondly, for the small boater if standard marine battery, a simple tester that you stick into each cell how it is fairing up as to holding a charge or the one you attach to each post which is a little more pricey. It is not only the charge but also can the battery still be charged.