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#1
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posted to rec.boats.cruising,rec.boats.building
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![]() "Pete C" wrote in message ups.com... On Jul 25, 10:46 am, wrote: Thanks for info. I started to read your technical section and the lights went out but will do more studying later. I've always liked the idea of a meter that showed amps in/amps out but never was able to figure out a method of outwitting the time necessary for the chemical changes to take place during the charging phase. Hi, Just google for 'battery conductance tester', that's basically what it is. Whether it's worth having or not IMHO depends largely on whether the prospective user knows little about electrics and isn't able to use a hydrometer. cheers, Pete. Pete, do you propose using a hydrometer everytime you want to know your state of charge? This could be a couple of times each day, or more. |
#2
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posted to rec.boats.cruising,rec.boats.building
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On Jul 25, 2:37 pm, "KLC Lewis" wrote:
"Pete C" wrote in message Pete, do you propose using a hydrometer everytime you want to know your state of charge? This could be a couple of times each day, or more. Hi, For those who know a bit about electrics and can use a hydrometer I would propose: Do an energy budget/audit. Size the battery bank for 40% DoD (depth of discharge) on a normal days/period of use Use the hydro to verify the above a few times as well as check the batts are getting fully charged. Use the hydro to check a few times that an exceptional days/period of demand doesn't draw the batts below 80% DoD Comments??? cheers, Pete. |
#3
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posted to rec.boats.cruising,rec.boats.building
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![]() "Pete C" wrote in message oups.com... On Jul 25, 2:37 pm, "KLC Lewis" wrote: "Pete C" wrote in message Pete, do you propose using a hydrometer everytime you want to know your state of charge? This could be a couple of times each day, or more. Hi, For those who know a bit about electrics and can use a hydrometer I would propose: Do an energy budget/audit. Size the battery bank for 40% DoD (depth of discharge) on a normal days/period of use Use the hydro to verify the above a few times as well as check the batts are getting fully charged. Use the hydro to check a few times that an exceptional days/period of demand doesn't draw the batts below 80% DoD Comments??? cheers, Pete. My own energy needs are quite modest. Nav instruments, VHF, stereo, running and anchor lights, computer (laptop), the occasional cabin light for short periods (converting to led units). No refer, no power windlass. Of course, I do need to be able to start-up the iron genny from time to time. My battery bank is 4 new-this-seasonTrojan T-105's and a 40 amp smart charger for dockside use. 2 US32 solar panels rated at 64 watts. Voltmeter always reads "top of the green" at 13 volts after dockside charging, bottom middle of the green after sailing for a day and anchoring out overnight with the anchor light lit. Engine starts right up like it has a fully-charged battery when weighing anchor in the morning. But translating this to "how much power do I have left?" leaves me paranoid. |
#4
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posted to rec.boats.cruising,rec.boats.building
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Hi,
If you're able to use a hydrometer, this FAQ tells how to relate battery 'SG' to state of charge: http://www.batteryfaq.org/ http://jgdarden.com/batteryfaq/carfaq4.htm http://jgdarden.com/batteryfaq/carfaq4.htm#soc Bear in mind 'state of charge' isn't a percentage of the battery's *rated* capacity, as they lose capacity as they get old or sulphated. State of charge is a percentage of the *actual* capacity of the battery, taking into account it's age and condition. To work out the actual capacity you need to compare the drop in state of charge to a known amount of charge used. So if drawing 1 amp for 10 hours (10 'amp hours') from a battery makes it's state of charge drop by 25%, the actual capacity is about 40 amp hours when it's fully charged. If the above battery then reads a 75% state of charge, then approximately 30 amp hours of charge are available until it's completely flat. (Though of course it should be recharged when the state of charge is around 50% or less) If the above is a bit too then try and get someone to explain it to you in person as it's a little difficult to do in a short posting. hope this helps, Pete. |
#5
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posted to rec.boats.cruising,rec.boats.building
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On Wed, 25 Jul 2007 10:35:06 -0700, Pete C
wrote: Hi, If you're able to use a hydrometer, this FAQ tells how to relate battery 'SG' to state of charge: http://www.batteryfaq.org/ http://jgdarden.com/batteryfaq/carfaq4.htm http://jgdarden.com/batteryfaq/carfaq4.htm#soc Bear in mind 'state of charge' isn't a percentage of the battery's *rated* capacity, as they lose capacity as they get old or sulphated. State of charge is a percentage of the *actual* capacity of the battery, taking into account it's age and condition. To work out the actual capacity you need to compare the drop in state of charge to a known amount of charge used. So if drawing 1 amp for 10 hours (10 'amp hours') from a battery makes it's state of charge drop by 25%, the actual capacity is about 40 amp hours when it's fully charged. If the above battery then reads a 75% state of charge, then approximately 30 amp hours of charge are available until it's completely flat. (Though of course it should be recharged when the state of charge is around 50% or less) If the above is a bit too then try and get someone to explain it to you in person as it's a little difficult to do in a short posting. hope this helps, Pete. Sorry Pete I cannot relate to the above, it is a far too simplistic. Here in the UK and I feel also in the US battery capacity is normally quoted at a 20hour rate. Therefore in the example offered above - 1A for 10hrs giving a 25% drop in "State of Charge" the actual original battery capacity would have been more like 35AH given a Peukert of 1.25 Ok I realise that you used the term "about" but we are talking major % differences here. To put the test another way are you saying that if the load had been 100ma for 100hours = 10amp hours your conclusions would have been the same? I would then suggest the battery's max capacity would have been 22Ah. -- Richard Nb "Pound Eater" Parkend G+S "Governments are like Nappies, they should be changed often." (For the same reason) |
#6
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posted to rec.boats.cruising,rec.boats.building
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On Jul 26, 7:51 am, Electricky Dicky wrote:
Sorry Pete I cannot relate to the above, it is a far too simplistic. Here in the UK and I feel also in the US battery capacity is normally quoted at a 20hour rate. Therefore in the example offered above - 1A for 10hrs giving a 25% drop in "State of Charge" the actual original battery capacity would have been more like 35AH given a Peukert of 1.25 Ok I realise that you used the term "about" but we are talking major % differences here. Very good point, to get a good comparison of actual to rated capacity you'd need to discharge at a 20hr rate. So for a 40Ah battery this would be 40(Ah)/20(hours) = 2 amps. cheers, Pete. |
#7
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posted to rec.boats.cruising,rec.boats.building
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On Wed, 25 Jul 2007 11:04:43 -0500, "KLC Lewis"
wrote: "Pete C" wrote in message roups.com... On Jul 25, 2:37 pm, "KLC Lewis" wrote: "Pete C" wrote in message Pete, do you propose using a hydrometer everytime you want to know your state of charge? This could be a couple of times each day, or more. Hi, For those who know a bit about electrics and can use a hydrometer I would propose: Do an energy budget/audit. Size the battery bank for 40% DoD (depth of discharge) on a normal days/period of use Use the hydro to verify the above a few times as well as check the batts are getting fully charged. Use the hydro to check a few times that an exceptional days/period of demand doesn't draw the batts below 80% DoD Comments??? cheers, Pete. My own energy needs are quite modest. Nav instruments, VHF, stereo, running and anchor lights, computer (laptop), the occasional cabin light for short periods (converting to led units). No refer, no power windlass. Of course, I do need to be able to start-up the iron genny from time to time. My battery bank is 4 new-this-seasonTrojan T-105's and a 40 amp smart charger for dockside use. 2 US32 solar panels rated at 64 watts. Voltmeter always reads "top of the green" at 13 volts after dockside charging, bottom middle of the green after sailing for a day and anchoring out overnight with the anchor light lit. Engine starts right up like it has a fully-charged battery when weighing anchor in the morning. But translating this to "how much power do I have left?" leaves me paranoid. And you have 450AH available ;-) I have customers who live on their boat with less than that! Paranoid is a bit OTT but aware is sensible. -- Richard Nb "Pound Eater" Parkend G+S "Governments are like Nappies, they should be changed often." (For the same reason) |
#8
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posted to rec.boats.cruising,rec.boats.building
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On Wed, 25 Jul 2007 08:17:40 -0700, Pete C
wrote: On Jul 25, 2:37 pm, "KLC Lewis" wrote: "Pete C" wrote in message Pete, do you propose using a hydrometer everytime you want to know your state of charge? This could be a couple of times each day, or more. Hi, For those who know a bit about electrics and can use a hydrometer I would propose: Do an energy budget/audit. Size the battery bank for 40% DoD (depth of discharge) on a normal days/period of use Use the hydro to verify the above a few times as well as check the batts are getting fully charged. Use the hydro to check a few times that an exceptional days/period of demand doesn't draw the batts below 80% DoD Comments??? 99% of my customers would not know what a hydrometer was 99% of my customers have no idea what their audit is 70% do not care 30% want to be able to look at something to tell them whether to charge or not cheers, Pete. -- Richard Nb "Pound Eater" Parkend G+S "Governments are like Nappies, they should be changed often." (For the same reason) |
#9
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posted to rec.boats.cruising,rec.boats.building
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On Jul 26, 7:58 am, Electricky Dicky wrote:
On Wed, 25 Jul 2007 08:17:40 -0700, Pete C wrote: For those who know a bit about electrics and can use a hydrometer I would propose [stuff snipped....] 99% of my customers would not know what a hydrometer was 99% of my customers have no idea what their audit is 70% do not care 30% want to be able to look at something to tell them whether to charge or not Exactly! E-X-A-C-T-L-Y! If they knew a bit about electrics and could use a hydrometer, they wouldn't be your customer, as they woundn't need professional help, would they? cheers, Pete. |
#10
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posted to rec.boats.cruising,rec.boats.building
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![]() "Pete C" wrote in message ps.com... On Jul 26, 7:58 am, Electricky Dicky wrote: On Wed, 25 Jul 2007 08:17:40 -0700, Pete C wrote: For those who know a bit about electrics and can use a hydrometer I would propose [stuff snipped....] 99% of my customers would not know what a hydrometer was 99% of my customers have no idea what their audit is 70% do not care 30% want to be able to look at something to tell them whether to charge or not Exactly! E-X-A-C-T-L-Y! If they knew a bit about electrics and could use a hydrometer, they wouldn't be your customer, as they woundn't need professional help, would they? cheers, Pete. It takes me about 10 - 15 minutes to check all of the cells in my bank. This is with the boat sitting calmly at the dock. I would much prefer not to have to open those cells with the boat in motion, sloshing battery acid around. If a meter will give me reasonably accurate information, which I can verify from time to time with a physical check of the electrolyte when it can be done safely, so much the better. |