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Thread: Inverter batteries

  1. #11
    Senior Member Endurance's Avatar
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    12 volts vs 24 or 48 volts

    If all of your loads were going to go through an inverter and come out at 120 volts, having a 24 volt or even a 48 volt battery bank would be a no brainer. Like some of the other posters here, I thought if I ever had the chance to change to a higher voltage battery bank, I would do it. The higher the voltage, the smaller wires you can use. There is a little efficiency gain if your inverter is going from 48 volts DC to 120 volts AC. The biggest advantage is that your battery bank has more series connections and fewer parallel connections. I will try to add more about parallel connections in a future post.

    I had my chance to jump from 12 volts last month. I had to replace my inverter/charger and therefore had free reign to buy whatever I wanted. Going to a higher voltage bank all sounded good until I started considering all of the things I had to do to have a higher voltage battery bank. All of my lighting (interior and navigation) is 12 volts. I have a 12 volt unit that uses UV light to kill bacteria and viruses in my drinking water. I have both entertainment stereo systems and a marine radio that are 12 volts. Even my TV and VCR are 12 volts. I added up all my 12 volt loads and figured I would need to plan for 50 amps to run everything that operated on 12 volts. In theory, you can tap ¼ of a 48 volt bank or ½ of a 24 volt bank to supply 12 volts. But in practice, that can cause battery bank imbalances. Battery bank imbalances are a big deal. They can dramatically shorten battery life.

    I considered separate battery banks. But for two banks, you need two chargers, two monitoring systems, and a lot of wiring. It gets complicated.

    I considered using a DC to DC converter to drop 24 or 48 volts from a battery bank down to 12 volts to use. But for 50 amps, a converter was running about $600. The manufacturer rated it with a lower operating temperature than the 110 degrees I often see on my lake. By the time I found a DC to DC converter that would reliably convert 24 or 48 volts to 12 volts at higher temperatures, I was looking at a $1,000 converter. I even considered using an MPPT solar charge controller to drop voltage from 48 to 12. But they aren’t cheap and not really tested or made for what I had in mind.

    In the end, I decided to make the choice to stay at 12 volts. It didn’t have so much to do with money as it did with simplicity and reliability. I never know when my life might depend on things like nav lights, water purification, and a marine radio. I want as few things as possible between those devices and their power source. Fewer “things” means fewer things to break. I go to my boat to play, not to work on things. So given the choice, I have a 12 volt battery bank.

  2. #12
    Member Frantically Relaxing's Avatar
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    Does anyone have any info on the technology involving newfangled batteries? Such as the new Lithium Iron Phosphate batteries that have come out? I'm not sure of the current technology, BUT, I bought one of these for my Honda Goldwing last spring. The lead-adid battery for this bike--



    --- weighs 14 pounds, the one in the pic costs $93 (I pay slightly less for what Walmart sells), I rarely get more than a year's service from them.

    The L-I battery I bought:



    -- weighs less than 2-1/2 pounds and is about 1/3 the size, it's height is about 1/2" more than the THICKNESS of the LA battery. It came with a piece of foam the same size as the stock battery, with a hole in it to fit the new battery.

    It looks and even feels like a toy, but this battery started my Goldwing better than any LA battery that's ever been in it. The rub is the cost, I paid $148 for it. But if the thing lasts just 2-1/2 years (it's warranted for 3 years) It'll save me money vs what I pay for LA batteries. And fwiw, I've always removed the batteries for winter, keep them from freezing, and trickle charge them 2 or 3 times over the winter. Doesn't matter. Life span on 7 batteries since I've owned this bike has varied from 7 months to just over 18 months once. Usually they work good for the summer, and come spring I get maybe a week's use.

    I'm betting the new battery works just fine come spring. But we'll see.

    That all said, I just think it would be wonderful if such batteries were available for boats and RV's for inverter use. As far as I know there's no gasses from charging(?), and geez, the weight savings would be tremendous...
    1988 SkipperLiner 53x14
    1995 Tracker Party Cruiser 32 *for sale*
    2003 Chaparral 260 SSI
    2000 Allegro Bus 40' DP

  3. #13
    Senior Member Endurance's Avatar
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    FR, a friend of mine that lives about half way between us replaced his Lake Powell house bank with Lithium Ion batteries. So far, the results have been mixed. Because you can draw a Lithium bank down to almost zero rather than the 50% or 60% that you can do with lead-acid batteries, the claims about replacing an 800 Ah bank with a 400 Ah bank were true. They were astoundingly expensive, but if the new batteries last as long as they're supposed to, they will be cost effective in the long run. One of the two batteries in his bank went bad within a year. The seller stepped up and swapped out both batteries in the bank. My friend was having a few more issues when I last talked to him, but he wasn't sure if that was his battery bank or his charger. I am really grateful to people like my friend and early buyers of hybrid cars who act as beta testers for the rest of us.

    I wouldn't be surprised to see the day when we laugh that we carried lead around in our boats. But I am thinking we're not there yet.

  4. #14
    Member Frantically Relaxing's Avatar
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    I've heard that the "lion" batteries, or some of them anyway, can be pretty fickle about charging and mininum/maximum voltage values...
    1988 SkipperLiner 53x14
    1995 Tracker Party Cruiser 32 *for sale*
    2003 Chaparral 260 SSI
    2000 Allegro Bus 40' DP

  5. #15
    Senior Member easttnboater's Avatar
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    I was in Sam's yesterday - "Duracel" 6v golf cart batteries - $81 each with speedy caps. I am sure they are made by Johnson Controls.

  6. #16
    Senior Member Stmbtwle's Avatar
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    Check the amp-hour rating. Not all golf batteries are the same. If they won't tell you, there's a reason.
    She's a tired old barge but she's paid for... http://s71.beta.photobucket.com/user...24993.pbw.html

  7. #17
    Senior Member easttnboater's Avatar
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    Here are the specs:

    20 amp hour rate:215
    5 amp hour rate:157
    6 amp hour rate:156
    BCI Group Size:GC2
    Contents:ONE EACH
    Minutes at 25 amps:395
    Minutes at 75 amps:105
    Volts:6

  8. #18
    Senior Member Stmbtwle's Avatar
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    215 is a pretty good battery. Some are only 190 or less.

    A few years ago I bought a couple of "everstart" batteries from Wally World, for my canoe. There were no specs on the battery and the service department couldn't tell me either, nor could I find them on the 'net. I still don't know. They were OK for the canoe (cheap), but I wouldn't put them in the houseboat.
    She's a tired old barge but she's paid for... http://s71.beta.photobucket.com/user...24993.pbw.html

  9. #19
    Senior Member Endurance's Avatar
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    To some extent, how you plan to tie all your batteries together can influence which batteries you buy. You can connect batteries in series, in parallel, and in series/parallel.

    Two batteries in series look like this:

    Batteries in series add voltage but leave amp hours the same. Two 6 volt 200 amp hour golf cart batteries in series will have 200 amp hours at 12 volts.

    Two batteries in parallel look like this:

    Batteries in parallel add amp hours but leave voltage the same. Two 12 volt 100 amp hour batteries in parallel will have 200 amp hours at 12 volts.

    Series/parallel connections are just adding the two connection types together. It is what most of us have in our battery banks. Four batteries in series/parallel look like this:

    Wiring two sets of two golf cart batteries like the picture above is like adding two very large 12 volt batteries together for more amp hours. Four 200 amp hour 6v batteries wired like the picture above would give you 400 amp hours at 12 volts.

    If you want a 12 volt battery bank but need more amp hours, you just keep adding parallel connections until your bank has enough amp hours to meet your needs. Eight golf cart batteries in series/parallel look like this:



    If the batteries in the above picture are 200 amp hour 6 volt golf cart batteries, the bank will have 800 amp hours at 12 volts.

    In theory, series and parallel connections should both be good and allow you to connect things the way you want to use whatever batteries you can afford and lift. But in real life, series connections are good and parallel connections are a necessary evil. The problem with parallel connections is the wires that go from battery to battery to connect them to each other. They are called jump wires. Each jump wire has a little resistance. To keep that resistance to a minimum, jump wires should always be at least as big as the main battery leads. With the right size wires, jump wire resistance is not much of a problem with batteries in series because all of the current has no choice but to flow through all the batteries in the series. With parallel connections, the electricity follows the path of least resistance, which will be the battery closest to where you connect your main lead. To minimize this problem, you should always pull positive from one end of the battery bank and negative from the other. These steps minimize battery imbalance, but the more parallel connections the worse your imbalance problems.

    Four 6v golf cart batteries in series/parallel connections are no problem because each set of two batteries has a main lead attached to it. That keeps the two sets in balance. You can even go to six golf cart batteries in three parallel sets of two batteries and things will stay in pretty good balance. But beyond that causes problems.

    My battery bank has eight golf cart batteries. That means four parallel sets of two batteries, which is too many. I am not as dumb as I look, though, because when I last bought batteries, golf cart batteries were so much cheaper on a $/amp hour basis that I went ahead with eight golf cart batteries knowing my parallel connections would shorten their lives a bit. Times change, though. Bigger batteries like L-16 size are getting to be more in line with golf cart batteries. When I next have to buy batteries, I might end up with four L-16 batteries to give me the same amp hours and voltage with half the parallel connections. It will depend on how battery prices go.

    I hope this helps. Good luck on your purchase.
    Last edited by Endurance; 11-14-2012 at 04:29 PM.

  10. #20
    Senior Member Stmbtwle's Avatar
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    Another problem with the parallel connections is that if one pair goes bad, it will pull the others down with it.

    Endurance what would be your opinion of rotating the pairs, say annually, like you do tires? I would keep the same batteries paired together, just rotate the pairs.

    How do the prices of L-16s compare with golf batteries these days (per amp hr)? Last time I checked they were much more expensive, and then there's the installation problem (they're HEAVY). Every time I replace batteries I consider L-16s, and every time I end up with golf batteries.

    Those parallel connections are one of the reasons to consider the high-voltage inverter.
    She's a tired old barge but she's paid for... http://s71.beta.photobucket.com/user...24993.pbw.html

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