I am shopping for deep cycle batteries and have been trying to compare types & lifecycles to others. The West Marine Product advisor states that manufacturers consider on cycle from a full charge discharged to 10.5 volts. My question is, when does that happen? Does it reach 10.5 volts at 50% of AH capacity or at 0%? For example, on a 100 AH battery that was discharged to 10.5 volts and you had one of those fancy Heart monitors or something similar on your system, what % is that battery used up at 10.5 V? I'm assuming 100% of the AH are used up in the lab if they wait for 10.5V between charges to determine cycles. Any electrical techs or "tweaking" types out there who can shed some light? Tim Boston, MA
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Hi Tim, lots of opinions on your topic...
IMHO, a fully charged 100 amp battery should read about 12.3-5 volts on your volt meter after a 30 minute rest with no draw. Generally, (emphasis on generally) when a battery is drawn down to 12 volts, you have consumed about 50 amps and many consider it flat and time to recharge. I've taken mine down to 11.5 volts and they still delivered power, albeit less strong. My rule of thumb is to recharge when they get to the low side of 12 volts, or 11.8 at their lowest. I've always considered a cycle when the battery has not been connected to a charging device for some period with some draw, then has been recharged. If you draw down a deep cycle battery below 10.5 volts often it will shorten their life. The other factor to consider is that many of your 12 volt appliances are designed to run on 12 volts with some minimal range on either side. Terry
IMHO, a fully charged 100 amp battery should read about 12.3-5 volts on your volt meter after a 30 minute rest with no draw. Generally, (emphasis on generally) when a battery is drawn down to 12 volts, you have consumed about 50 amps and many consider it flat and time to recharge. I've taken mine down to 11.5 volts and they still delivered power, albeit less strong. My rule of thumb is to recharge when they get to the low side of 12 volts, or 11.8 at their lowest. I've always considered a cycle when the battery has not been connected to a charging device for some period with some draw, then has been recharged. If you draw down a deep cycle battery below 10.5 volts often it will shorten their life. The other factor to consider is that many of your 12 volt appliances are designed to run on 12 volts with some minimal range on either side. Terry
Tim, Batteries are a good thing to learn
about! There is a lot to learn! There is also alot of opinions. You are going to be smashed with battery info. Good reference.. Nigel Calders boat maintenence. He has a great battery section! A battery is 100% charged when the voltage is about 12.72 after about 1 hour off the charger. A battery a 50% is when the voltage is about 12 to 12.25 volts when at rest for a period of time. It is recommended that you not discharge a battery below 50% if your want to get the most out of the battery. If you continually use the battery below 12 Volts, it will not recover to full charge like it would if only discharged to 50%. There are many other important things to know about a battery and how to keep them performing. A full charge when charging is one of the important things. The battery is something that books are writen about. Terry, I was typing when you posted. Hope I didn't step on any toes... r.w.landau
about! There is a lot to learn! There is also alot of opinions. You are going to be smashed with battery info. Good reference.. Nigel Calders boat maintenence. He has a great battery section! A battery is 100% charged when the voltage is about 12.72 after about 1 hour off the charger. A battery a 50% is when the voltage is about 12 to 12.25 volts when at rest for a period of time. It is recommended that you not discharge a battery below 50% if your want to get the most out of the battery. If you continually use the battery below 12 Volts, it will not recover to full charge like it would if only discharged to 50%. There are many other important things to know about a battery and how to keep them performing. A full charge when charging is one of the important things. The battery is something that books are writen about. Terry, I was typing when you posted. Hope I didn't step on any toes... r.w.landau
Chart
Here is a little chart that I got from somewhere. Who knows where, or how accurate, but it is neat to have. 12.60+ Volts = 100% charge 12.55 V = 93.7% 12.50 V = 87.5% 12.40 V = 75.0% 12.30 V = 62.5% 12.20 V = 50.0% 12.10 V = 37.5% 12.00 V = 25.0% 11.90 V = 16.7% DONT go below 11.9
Here is a little chart that I got from somewhere. Who knows where, or how accurate, but it is neat to have. 12.60+ Volts = 100% charge 12.55 V = 93.7% 12.50 V = 87.5% 12.40 V = 75.0% 12.30 V = 62.5% 12.20 V = 50.0% 12.10 V = 37.5% 12.00 V = 25.0% 11.90 V = 16.7% DONT go below 11.9
I found some articles
I was looking into some of this on my own a little while ago. The first I like. It doesn't fully explain all the concepts it identifies that affect battery performance, but it explains what it needs to nonetheless. The second is oversimplified, but I like the analogy.
I was looking into some of this on my own a little while ago. The first I like. It doesn't fully explain all the concepts it identifies that affect battery performance, but it explains what it needs to nonetheless. The second is oversimplified, but I like the analogy.
Article the Second
(as it would be called in the Constitution, so I can sound fancy...er...just click on the link)
(as it would be called in the Constitution, so I can sound fancy...er...just click on the link)
Depth of discharge vs. number of cycles....
As several other posters pointed out, there is an inverse relationship between how deep you discharge your battery and how many times you can do it. Turning to Nigel Calder's indespensible 'Boat Owners Mechanical and Electrical Manual', we see that for AGM cells, %discharge Life Cycles 10% 3,100 25% 925 50% 370 80% 200 100% 150 Other battery types (gel, wet-cell) are similar. Discharging/charging a battery damages it and deeper cycles cause more damage. The damage is mainly calcification or 'clogging' of the plate material during deep discharge/charge cycles, because that is when you use the electricity stored in the deeper recesses of the plates, and the charging process is imperfect, leaving un-charged plate material to get 'clogged'. At 10% discharge, you are mainly pulling electricity off the surfaces of the plates, so the battery will last a LONG time. The other inevitable killer of batteries is that each time you discharge/charge them, a little bit of plate material falls into the bottom of the battery. Sooner or later it builds up and touches the plate, shorting out the cell - most car batteries die this way. Bottom line? Forget 10.5 volts, use 12.2v (50%) as your floor. Keep your batteries fully charged while in the slip using a smart charger, keep them clean and topped up with distilled water, and don't forget an equalizing charge monthly if you're not sailing. (Even a short sail will do what an equalizing charge does, which is to 'stir' the electrolyte in the cells, which tends to settle to the bottom because sulphuric acid is heavier than water). And most important: don't wait till your batteries don't work to care about them..... unless you are good at either hand-cranking a diesel engine or sailing into your slip.
Batteries are fun, and a lot more complex than they look. Cheers, Bob
As several other posters pointed out, there is an inverse relationship between how deep you discharge your battery and how many times you can do it. Turning to Nigel Calder's indespensible 'Boat Owners Mechanical and Electrical Manual', we see that for AGM cells, %discharge Life Cycles 10% 3,100 25% 925 50% 370 80% 200 100% 150 Other battery types (gel, wet-cell) are similar. Discharging/charging a battery damages it and deeper cycles cause more damage. The damage is mainly calcification or 'clogging' of the plate material during deep discharge/charge cycles, because that is when you use the electricity stored in the deeper recesses of the plates, and the charging process is imperfect, leaving un-charged plate material to get 'clogged'. At 10% discharge, you are mainly pulling electricity off the surfaces of the plates, so the battery will last a LONG time. The other inevitable killer of batteries is that each time you discharge/charge them, a little bit of plate material falls into the bottom of the battery. Sooner or later it builds up and touches the plate, shorting out the cell - most car batteries die this way. Bottom line? Forget 10.5 volts, use 12.2v (50%) as your floor. Keep your batteries fully charged while in the slip using a smart charger, keep them clean and topped up with distilled water, and don't forget an equalizing charge monthly if you're not sailing. (Even a short sail will do what an equalizing charge does, which is to 'stir' the electrolyte in the cells, which tends to settle to the bottom because sulphuric acid is heavier than water). And most important: don't wait till your batteries don't work to care about them..... unless you are good at either hand-cranking a diesel engine or sailing into your slip.
Batteries are fun, and a lot more complex than they look. Cheers, Bob
Yup, that's why they write books and
have the Internet. Try the Ample Power Primer, and Calder's Boatowner's Manual is a must (even if you find a way to read it at a bookstore), but it's still the best $50 you can spend on your boat. Here's the link: www.amplepower.com Download and read the Ample Power Primer and save us all a lot of typing! Oh, in addition to the voltage, to measure capacity, you'll need to evaluate the specific gravity if they're wet cells.
have the Internet. Try the Ample Power Primer, and Calder's Boatowner's Manual is a must (even if you find a way to read it at a bookstore), but it's still the best $50 you can spend on your boat. Here's the link: www.amplepower.com Download and read the Ample Power Primer and save us all a lot of typing! Oh, in addition to the voltage, to measure capacity, you'll need to evaluate the specific gravity if they're wet cells.
Jared...
your voltage chart for a 12 volt wet cell battery is good to go for readings taken with a digital voltmeter. One could also use the cells' collective specific gravity readings to determine the percentage of charge, but it's a whole lot messier (but does allow you to find a bad cell when a battery won't hold a charge).
your voltage chart for a 12 volt wet cell battery is good to go for readings taken with a digital voltmeter. One could also use the cells' collective specific gravity readings to determine the percentage of charge, but it's a whole lot messier (but does allow you to find a bad cell when a battery won't hold a charge).
Peter I liked your first article
One of the big problems when using a voltmeter to indicate battery condition is that the battery must have been at rest for an hour or more. The first article that you posted shows how you can use a voltmeter to indicate condition of a battery, even if it is charging or discharging (provided you know the charging or discharging amperage). I had not seen these curves before. Thanks for posting!
One of the big problems when using a voltmeter to indicate battery condition is that the battery must have been at rest for an hour or more. The first article that you posted shows how you can use a voltmeter to indicate condition of a battery, even if it is charging or discharging (provided you know the charging or discharging amperage). I had not seen these curves before. Thanks for posting!
Thanks for the posts guys!
Thanks for all of your replies. I do own Nigel Calder's Electrical and Mechanical manual and have read it about 5 times now and every time I pick it up, it always seems "new". Maybe I have reached my "equalization" or got a little overwhelmed with information overload with all the technical stuff I've been reading latey. I agree many people never get to the root of their electrical problem and just throw more money at it. I want to start off right with this boat by getting help from friends to install a voltmeter and/or basic monitoring system. Once that's done, then I feel I can spring for the top of the line batteries. Tim
Thanks for all of your replies. I do own Nigel Calder's Electrical and Mechanical manual and have read it about 5 times now and every time I pick it up, it always seems "new". Maybe I have reached my "equalization" or got a little overwhelmed with information overload with all the technical stuff I've been reading latey. I agree many people never get to the root of their electrical problem and just throw more money at it. I want to start off right with this boat by getting help from friends to install a voltmeter and/or basic monitoring system. Once that's done, then I feel I can spring for the top of the line batteries. Tim
Get a good monitor....
and then you'll have what you need to take care of your good batteries and stuff when you buy them. I've lusted after a Xantrex Link Monitor, but it's still down the list of 'boat bucks gobblers', and I don't really need it for the sailing I get to do these days. Some day. Cheers, Bob
and then you'll have what you need to take care of your good batteries and stuff when you buy them. I've lusted after a Xantrex Link Monitor, but it's still down the list of 'boat bucks gobblers', and I don't really need it for the sailing I get to do these days. Some day.
Cheers, Bob- Status