Thursday, April 28, 2011

Re: [Electric Boats] Re: How do you measure how much battery life is left whlile you are out sailing?

 

                                 Battery Load Voltage vs. DOD
Below are listed the 1 hour, 8 hour, 20 hour and 120 hour load voltages during the discharge
cycle from full charge to 100% discharge to 1.75V/cell or 10.5V (6 cells) at 25°C (77°F).
         DOD (%)          1 hr. Rate       8 hr. Rate       20 hr. Rate      120 hr. Rate
            10              12.23            12.60             12.65            12.69
            20              12.16            12.51             12.55            12.58
            30              12.07            12.39             12.42            12.45
            40              11.96            12.25             12.28            12.32
            50              11.83            12.11             12.15            12.18
            60              11.70            11.98             12.02            12.05
            70              11.55            11.79             11.83            11.88
            80              11.38            11.59             11.61            11.65
            90              11.15            11.32             11.34            11.40
            100             10.50            10.50             10.50            10.50
Please note that these voltages are averages and will vary slightly from battery to battery even
of the same rating. They are, however, a good indicator of state of charge and can be used
when setting low voltage alarms or disconnects for a Concorde AGM battery. Other battery
types or manufacturers voltage vs. DOD may be substantially different. The data is for newer
batteries with relatively few cycles. An older battery will measure a lower voltage for a given
DOD.

I got this from lifeline batteries  website..Should be close for AGMs
Richard


From: Arby bernt <arbybernt@yahoo.com>
To: electricboats@yahoogroups.com
Sent: Thursday, April 28, 2011 5:31:15 PM
Subject: Re: [Electric Boats] Re: How do you measure how much battery life is left whlile you are out sailing?

 

Hi Brett,
You can measure the realtime capacity of a wet battery by measuring the specific gravity of the electrolyte. Loaded or resting will not matter. AGM's are a bit tougher. Harbor Freight offers an electronic tester that uses high frequency loading to measure the battery response. I don't know if it will measure realtime capacity under load, but it will show the capacity at rest.

Let the EB list know how it works out.

Be Well,
Arby

--- In electricboats@yahoogroups.com, "m8trixman" <pb@...> wrote:
>
> What is the best way to measure what percent of battery life is left while you are out motoring?
>
> Thanks for taking the time to chime in on this question...
>
> Brett
>



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