monitoring depth of discharge

Shadowcatcher · January 2012

I pick up my Lifeline 150AH AGM battery Monday and will be monitoring DOD with a digital volt meter, BUT.
To get a true reading we are told you need to wait X period of time before measuring (I have seen up to two hours mentioned). Yet if you are using it...

Thomas · January 2012

Re: monitoring depth of discharge

I have seen two charts
one for running%
one for cold %

niel · January 2012

Re: monitoring depth of discharge

that will only give a rough indication of battery soc and if the battery has lost capacity it can fool you at times. real capacity is measured with a load test. thomas is right that there is 2, but the at rest voltage after 3 or more hours is a better indicator.

Shadowcatcher · January 2012

Re: monitoring depth of discharge

The difficulty in this situation is in an RV the battery is almost never at rest, it is either charging or it is discharging and the goal is to keep it from going below 50%. The Lifeline web site says 12.2V

stephendv · January 2012

Re: monitoring depth of discharge

There is a battery monitor that works based on the battery voltage and computer models that's supposed to be quite accurate: http://www.smartgauge.co.uk/

Thomas · January 2012

Re: monitoring depth of discharge

Is there such a measure as depth of charge? Or is this yet another complictad new idea that is old hat here? like 12v20a change to 24v10a charging?

BB. · January 2012

Re: monitoring depth of discharge

State of Charge (SOC). 0% SOC is empty battery. 100% SOC is full battery.

Depth of Discharge (DOD). 0% DOD is dead battery. 0% DOC is full battery.

-Bill

niel · January 2012

Re: monitoring depth of discharge

that's dod not doc for the record.

Jim45D · February 2012

Re: monitoring depth of discharge

Shadowcatcher: I for one can relate to what you're saying concerning monitoring your battery's DOD in a RV. Getting to my batteries is not a quick task. Although I did monitor them with a volt meter at first. Finally, I went with the Heart Interface Link 1000, (to my knowledge no longer available). It can be a hassle. I found a chart several years ago, that I copied, re-typed, laminated, and keep by my Link monitor for cross reference. (See below). There is a battery monitor at NAWS, by Trimetric. There are two versions, and one is made especially for RV's. Attractive too. Also priced right. It will tell you all you need to know concerning your battery SOC, DOD, Amps used, + more, etc.
You're right on the 12.2 being 50% discharged. I have followed this chart faithfully, and never went wrong.

It start's as thus:

VOLTAGE % CHARGE
12.75

100
12.70

95
12.65

90
12.60

85
12.55

80 * Happy Medium
12.50

75 * Happy Medium
12.45

70
12.40

65
12.30

55
12.25

50 ** Half Done
12.20

45 Start Charging, or go to bed, turn everything off.

This chart has alway's stayed in perfect alignment with my monitor. The numbers also align with a volt meter.

icarus · February 2012

Re: monitoring depth of discharge

You have to realize that while the voltage chart is useful, the numbers are only meaningful if the batteries have not been und load (or recharged) for a couple of hours,, kind of he'd to do while using the battery at the same time.

Tony

Thomas · February 2012

Re: monitoring depth of discharge

There is this feature on some chargers/meters, time since the last full charge.(I do not have one) I think this relevant to the state of charge/discharge discussion . If your volts just do not seem to reflect the charts per cent then I think the charts per cent must come from freshly maintained batteries. I think that even in full summertime load running batteries daaily only between 12.4v and 13.8v is good without setting a day for full charging, and night. One off grid would need a whole alternate battery bank for this Ideal

Jim45D · February 2012

Re: monitoring depth of discharge

I do realize that he may have to wait for proper settlement. But, he did mention his installation was in a RV. Unless he disconnects his batteries, which he probably can't, then....that's the next best senario. In my particular installation....I have to open the door when the charger disconnects, remove the steps to gain access to the batteries, disconnect one of the leads, replace steps, (not an easy task) wait....remove steps again, take reading, replace step assembly, and go from there. With a monitor he would have a approximate reading as to where he stands with the discharge rate. Most people don't have to go through those particular steps. I do. His could be in a compartment outside, It's still a hassle either way. With a monitor and the chart to compare with he'd get a rough idea as to what his battery, (batteries) are doing. Simply with a glance.

Shadowcatcher · February 2012

Re: monitoring depth of discharge

Fortunately RV covers a lot of territory and this includes our 6X10 Grasshopper design teardrop trailer. The battery is easily accessible as it is in the tongue box. In a reply that seems to have disappeared I stated that one of the big problems is places to put things particularly electrically related and a Trimetric takes up a good bit of room in an already crowded area. I am I think going to install a Victron BMV 600S battery monitor only requires a 2" hole, simpler setup and from what I can see easier for my brilliant but mechanically challenged wife to understand.

Attachment not found.

Blackcherry04 · February 2012

Re: monitoring depth of discharge

Jim45D, I like your Idea after 30 years of having every meter and battery monitor ever made I have found a simple LED volt meter and your type chart I am good to go. No buttons to push and no hassles. Digital gauges are available on E-bay for $15 with 1/2 inch digits that you can read from 50 feet away. Generally on a RV / Boat your only charging back to 80-85% and completely recharging some other time, all the monitors seem to get confused and out of sync.

monitoring depth of discharge

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