Forums

Charging a marine battery

Started by W. eWatson May 23, 2012
About 3 months ago, I purchased a deep cycle marine battery (12v) from 
Costco. It probably weighs 60 pounds. The application I intended for it 
is slowly proceeding, and I haven't used the battery at all. Any 
suggestions for charging it? I'll check the voltage tomorrow. It may not 
need it yet.

That reminds me, the June issue of Consumer Reports has an article about 
using an inverter with perhaps such a battery to keep the refrigerator, 
sump pump, lights and electronic chargers. They tested two inverters, 
Sears and WallMart.  The arrangement is not going to be as useful as a 
generator, but it could be handy for short term power outages. One could 
use a car battery to act somewhat as a generator.
On Tue, 22 May 2012 22:45:34 -0700, "W. eWatson" <wolftracks@invalid.com>
wrote:

>About 3 months ago, I purchased a deep cycle marine battery (12v) from >Costco. It probably weighs 60 pounds. The application I intended for it >is slowly proceeding, and I haven't used the battery at all. Any >suggestions for charging it? I'll check the voltage tomorrow. It may not >need it yet.
Charge it like any other lead-acid battery. It shouldn't need charging after only three months but it's not a good idea to leave L-A batteries to self-discharge. They prefer a float charge.
>That reminds me, the June issue of Consumer Reports has an article about >using an inverter with perhaps such a battery to keep the refrigerator, >sump pump, lights and electronic chargers. They tested two inverters, >Sears and WallMart. The arrangement is not going to be as useful as a >generator, but it could be handy for short term power outages. One could >use a car battery to act somewhat as a generator.
This is often done for sump pumps (a DC powered pump is a better idea), where a few hours can mean the difference between a dry and flooded basement. I don't think it's of much use for a refrigerator, though. With the door closed, they should stay cold for 24hrs or so, anyway. A car-battery-sized deep-cycle battery has a useful capacity of perhaps 50AH, so that's only 600WH. If you do this, be sure the inverter cuts out early enough to save the battery. They don't like to be run down to zero. A sump pump is a different deal because a flooded basement is worse than a ruined battery.
On May 23, 10:59=A0am, "k...@att.bizzzzzzzzzzzz"
<k...@att.bizzzzzzzzzzzz> wrote:
> On Tue, 22 May 2012 22:45:34 -0700, "W. eWatson" <wolftra...@invalid.com> > wrote: > > >About 3 months ago, I purchased a deep cycle marine battery (12v) from > >Costco. It probably weighs 60 pounds. The application I intended for it > >is slowly proceeding, and I haven't used the battery at all. Any > >suggestions for charging it? I'll check the voltage tomorrow. It may not > >need it yet. > > Charge it like any other lead-acid battery. =A0It shouldn't need charging=
after
> only three months but it's not a good idea to leave L-A batteries to > self-discharge. =A0They prefer a float charge. > > >That reminds me, the June issue of Consumer Reports has an article about > >using an inverter with perhaps such a battery to keep the refrigerator, > >sump pump, lights and electronic chargers. They tested two inverters, > >Sears and WallMart. =A0The arrangement is not going to be as useful as a > >generator, but it could be handy for short term power outages. One could > >use a car battery to act somewhat as a generator. > > This is often done for sump pumps (a DC powered pump is a better idea), w=
here
> a few hours can mean the difference between a dry and flooded basement. =
=A0I
> don't think it's of much use for a refrigerator, though. =A0With the door > closed, they should stay cold for 24hrs or so, anyway.
It's hard to get the beer out of there with the door closed though. :^) A car-battery-sized
> deep-cycle battery has a useful capacity of perhaps 50AH, so that's only
Say, where did you get the 50AH figure? I've always wanted some 'ball park' number for the capacity of my car battery. But I could never find any information. George H.
> 600WH. =A0If you do this, be sure the inverter cuts out early enough to s=
ave the
> battery. =A0They don't like to be run down to zero. =A0A sump pump is a d=
ifferent
> deal because a flooded basement is worse than a ruined battery.
On Tue, 22 May 2012 22:45:34 -0700, "W. eWatson"
<wolftracks@invalid.com> wrote:

>About 3 months ago, I purchased a deep cycle marine battery (12v) from >Costco. It probably weighs 60 pounds. The application I intended for it >is slowly proceeding, and I haven't used the battery at all. Any >suggestions for charging it? I'll check the voltage tomorrow. It may not >need it yet. > >That reminds me, the June issue of Consumer Reports has an article about >using an inverter with perhaps such a battery to keep the refrigerator, >sump pump, lights and electronic chargers. They tested two inverters, >Sears and WallMart. The arrangement is not going to be as useful as a >generator, but it could be handy for short term power outages. One could >use a car battery to act somewhat as a generator.
A typical car battery would be 80AH. That's 4 amps for 20 hours, not 80 amps for one hour. As the load increases (more amps) the Peukert factor comes into play and there are diminishing returns. Don't expect to get the battery's rated AH capacity with a large load. There are also the losses associated with excessive discharge of lead-acid batteries. For maximum life, the battery should never be discharged below 50%. That means your 8AH battery can only deliver 40AH and have reasonable life (perhaps 3-5 years). You're now down to 4 amps for 10 hours. At a real-world load of say 5 amps to power a 60 watt laptop using a DC-DC converter to convert 12 volts to the 17-19 volts most laptops require (5 amps * 12 volts = 60 watts), the 80AH rating drops to 75AH, so the 50% level is about 37AH which would give a little over 7 hours (37AH/5amps = 7.4 hours). When you add an inverter to get AC, you're losing some power to the inefficiency of the inverter (depending on design, type, and load efficiencies can run 80-95%). For an example, I'll use 90%. Say you have an AC device that uses 400 watts. With a 90% efficient inverter, you would need 400/.9 = 444 watts from the battery. 444/12 = 37 amps. At that load, the battery's AH rating drops to about 40AH, so the 50% level is 20AH. 20AH/37amps = .54 hours or about 32 minutes. That's not much time for whatever appliance you were thinking about powering. Bigger loads (fridge, etc) require proportionally more current from the battery and deplete it even faster. There's a reason alternate energy homes have battery bans rated in the hundreds of amp-hours. There is some rounding in the numbers, but they are realistic. I don't have a solar farm, just spent some time doing the calculations. If I cut enough trees to provide a full day of sun on the roof, I'd need to double the size of the solar farm to handle the additional heat load. The cost of tree removal plus doubling the number of solar panels keeps the project from being an economically sound propsition. Want to do your own calculations? There's an Excel spreadsheet here: http://www.otherpower.com/images/scimages/5410/peukert_calc.xls There was an online calculator here: http://green-trust.org/peukert/ but it seems to be down today.
On 2012-05-23, W. eWatson <wolftracks@invalid.com> wrote:
> About 3 months ago, I purchased a deep cycle marine battery (12v) from > Costco. It probably weighs 60 pounds. The application I intended for it > is slowly proceeding, and I haven't used the battery at all. Any > suggestions for charging it? I'll check the voltage tomorrow. It may not > need it yet.
don't leave it sitting on a concrete floor, the temperature difference between floor and ambient can lead to stratification in the electrolyte which can accelerate self-discharge. eg: raise it off the floor on some blocks of wood. -- &#9858;&#9859; 100% natural --- Posted via news://freenews.netfront.net/ - Complaints to news@netfront.net ---
On Wed, 23 May 2012 09:11:16 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

>On May 23, 10:59&#2013266080;am, "k...@att.bizzzzzzzzzzzz" ><k...@att.bizzzzzzzzzzzz> wrote: >> On Tue, 22 May 2012 22:45:34 -0700, "W. eWatson" <wolftra...@invalid.com> >> wrote: >> >> >About 3 months ago, I purchased a deep cycle marine battery (12v) from >> >Costco. It probably weighs 60 pounds. The application I intended for it >> >is slowly proceeding, and I haven't used the battery at all. Any >> >suggestions for charging it? I'll check the voltage tomorrow. It may not >> >need it yet. >> >> Charge it like any other lead-acid battery. &#2013266080;It shouldn't need charging after >> only three months but it's not a good idea to leave L-A batteries to >> self-discharge. &#2013266080;They prefer a float charge. >> >> >That reminds me, the June issue of Consumer Reports has an article about >> >using an inverter with perhaps such a battery to keep the refrigerator, >> >sump pump, lights and electronic chargers. They tested two inverters, >> >Sears and WallMart. &#2013266080;The arrangement is not going to be as useful as a >> >generator, but it could be handy for short term power outages. One could >> >use a car battery to act somewhat as a generator. >> >> This is often done for sump pumps (a DC powered pump is a better idea), where >> a few hours can mean the difference between a dry and flooded basement. &#2013266080;I >> don't think it's of much use for a refrigerator, though. &#2013266080;With the door >> closed, they should stay cold for 24hrs or so, anyway. > >It's hard to get the beer out of there with the door closed >though. :^)
When the power's out, you're better off going down to the pub. It's much more fun and you have to drink up the tap beer before it spoils.
>A car-battery-sized >> deep-cycle battery has a useful capacity of perhaps 50AH, so that's only > >Say, where did you get the 50AH figure? I've always wanted some >'ball park' number for the capacity of my car battery. But I could >never find any information.
Experience. The information is available.
On 5/24/2012 2:23 AM, Jasen Betts wrote:
> On 2012-05-23, W. eWatson<wolftracks@invalid.com> wrote: >> About 3 months ago, I purchased a deep cycle marine battery (12v) from >> Costco. It probably weighs 60 pounds. The application I intended for it >> is slowly proceeding, and I haven't used the battery at all. Any >> suggestions for charging it? I'll check the voltage tomorrow. It may not >> need it yet. > > don't leave it sitting on a concrete floor, the temperature difference > between floor and ambient can lead to stratification in the > electrolyte which can accelerate self-discharge. > > eg: raise it off the floor on some blocks of wood. > >
It's been sitting on a table.
On 5/23/2012 9:47 AM, news@jecarter.us wrote:
> On Tue, 22 May 2012 22:45:34 -0700, "W. eWatson" > <wolftracks@invalid.com> wrote: > >> About 3 months ago, I purchased a deep cycle marine battery (12v) from >> Costco. It probably weighs 60 pounds. The application I intended for it >> is slowly proceeding, and I haven't used the battery at all. Any >> suggestions for charging it? I'll check the voltage tomorrow. It may not >> need it yet. >> >> That reminds me, the June issue of Consumer Reports has an article about >> using an inverter with perhaps such a battery to keep the refrigerator, >> sump pump, lights and electronic chargers. They tested two inverters, >> Sears and WallMart. The arrangement is not going to be as useful as a >> generator, but it could be handy for short term power outages. One could >> use a car battery to act somewhat as a generator. > > A typical car battery would be 80AH. That's 4 amps for 20 hours, not > 80 amps for one hour. As the load increases (more amps) the Peukert > factor comes into play and there are diminishing returns. Don't > expect to get the battery's rated AH capacity with a large load. > > There are also the losses associated with excessive discharge of > lead-acid batteries. For maximum life, the battery should never be > discharged below 50%. That means your 8AH battery can only deliver > 40AH and have reasonable life (perhaps 3-5 years). You're now down to > 4 amps for 10 hours. > At a real-world load of say 5 amps to power a 60 watt laptop using a > DC-DC converter to convert 12 volts to the 17-19 volts most laptops > require (5 amps * 12 volts = 60 watts), the 80AH rating drops to 75AH, > so the 50% level is about 37AH which would give a little over 7 hours > (37AH/5amps = 7.4 hours). > When you add an inverter to get AC, you're losing some power to the > inefficiency of the inverter (depending on design, type, and load > efficiencies can run 80-95%). For an example, I'll use 90%. Say you > have an AC device that uses 400 watts. With a 90% efficient inverter, > you would need 400/.9 = 444 watts from the battery. 444/12 = 37 amps. > At that load, the battery's AH rating drops to about 40AH, so the 50% > level is 20AH. 20AH/37amps = .54 hours or about 32 minutes. That's > not much time for whatever appliance you were thinking about powering. > Bigger loads (fridge, etc) require proportionally more current from > the battery and deplete it even faster. > There's a reason alternate energy homes have battery bans rated in the > hundreds of amp-hours. > > There is some rounding in the numbers, but they are realistic. I > don't have a solar farm, just spent some time doing the calculations. > If I cut enough trees to provide a full day of sun on the roof, I'd > need to double the size of the solar farm to handle the additional > heat load. The cost of tree removal plus doubling the number of solar > panels keeps the project from being an economically sound propsition. > > Want to do your own calculations? There's an Excel spreadsheet here: > http://www.otherpower.com/images/scimages/5410/peukert_calc.xls > > There was an online calculator here: > http://green-trust.org/peukert/ > but it seems to be down today. >
Just measured the voltage. 12.6. What sort of charger should I consider to keep this one happy when it's not in high use?
"W. eWatson" <wolftracks@invalid.com> wrote in message 
news:jphti3$1s4$1@dont-email.me...
> About 3 months ago, I purchased a deep cycle marine battery (12v) from > Costco. It probably weighs 60 pounds. The application I intended for it is > slowly proceeding, and I haven't used the battery at all. Any suggestions > for charging it? I'll check the voltage tomorrow. It may not need it yet.
I've had a motorcycle battery hooked up to an Optimate maintenance charger for about 3 years - it gets to deliver cranking current every blue moon when the one in the motorcycle is found to need charging. There are various competing brands - do a web search.
"W. eWatson" <wolftracks@invalid.com> wrote in message 
news:jplrpa$aum$1@dont-email.me...
> On 5/24/2012 2:23 AM, Jasen Betts wrote: >> On 2012-05-23, W. eWatson<wolftracks@invalid.com> wrote: >>> About 3 months ago, I purchased a deep cycle marine battery (12v) from >>> Costco. It probably weighs 60 pounds. The application I intended for it >>> is slowly proceeding, and I haven't used the battery at all. Any >>> suggestions for charging it? I'll check the voltage tomorrow. It may not >>> need it yet. >> >> don't leave it sitting on a concrete floor, the temperature difference >> between floor and ambient can lead to stratification in the >> electrolyte which can accelerate self-discharge. >> >> eg: raise it off the floor on some blocks of wood. >> >> > It's been sitting on a table. >
If you leave it to eventually self discharge it will sulphate and be a write off. If you leave it on float charge "forever" it'll either gas itself dry or become "lazy". If you don't do anything else - charge it once per month, better still make it do a bit of work before each recharge.