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battery specific-gravity = AmpHour capacity?
does specific-gravity of a conventional lead-acid cell, linearly
measure its AmpHour capacity? If not, what exactly does it indicate with respect to the battery user's needs? |
wrote in message oups.com... | does specific-gravity of a conventional lead-acid cell, linearly | measure its AmpHour capacity? | | If not, what exactly does it indicate with respect to the battery | user's needs? It's proportional to % of charge. I doubt it is linear. See http://www.buchanan1.net/lead_acid.shtml |
On Tue, 11 Jan 2005 00:35:58 GMT, "NSM" wrote:
wrote in message roups.com... | does specific-gravity of a conventional lead-acid cell, linearly | measure its AmpHour capacity? | | If not, what exactly does it indicate with respect to the battery | user's needs? It's proportional to % of charge. I doubt it is linear. See http://www.buchanan1.net/lead_acid.shtml It is close enough to linear that some battery manufacturers provide coefficients and/or graphs of SOC vs SG and temp. It does of course require "calibration" to accomodate the actual acid/water proportions at fill and any loss/replacement. |
And you're talking about the specific gravity of just the liquid
electrolyte, of course, not the entire cell. |
On Tue, 11 Jan 2005 10:22:51 +0800, budgie wrote:
On Tue, 11 Jan 2005 00:35:58 GMT, "NSM" wrote: wrote in message groups.com... | does specific-gravity of a conventional lead-acid cell, linearly | measure its AmpHour capacity? | | If not, what exactly does it indicate with respect to the battery | user's needs? It's proportional to % of charge. I doubt it is linear. See http://www.buchanan1.net/lead_acid.shtml It is close enough to linear that some battery manufacturers provide coefficients and/or graphs of SOC vs SG and temp. It does of course require "calibration" to accomodate the actual acid/water proportions at fill and any loss/replacement. Battery terminal voltage is also an indication of specific gravity and SOC. R.F. |
On 16 Jan 2005 02:08:07 -0600, R. F. Burns R.F. wrote:
On Tue, 11 Jan 2005 10:22:51 +0800, budgie wrote: On Tue, 11 Jan 2005 00:35:58 GMT, "NSM" wrote: wrote in message egroups.com... | does specific-gravity of a conventional lead-acid cell, linearly | measure its AmpHour capacity? | | If not, what exactly does it indicate with respect to the battery | user's needs? It's proportional to % of charge. I doubt it is linear. See http://www.buchanan1.net/lead_acid.shtml It is close enough to linear that some battery manufacturers provide coefficients and/or graphs of SOC vs SG and temp. It does of course require "calibration" to accomodate the actual acid/water proportions at fill and any loss/replacement. Battery terminal voltage is also an indication of specific gravity and SOC. Apart from being temperature-dependent, terminal voltage is very dependent on recent charge/discharge history. Unless a known regime is implemented before measurement, OCV can be very misleading as a SOC indicator. |
On 16 Jan 2005 02:08:07 -0600, R. F. Burns R.F. wrote:
Battery terminal voltage is also an indication of specific gravity and SOC. AFAIR - no. But internal resistance of battery - yes. Best, Borek |
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