View Full Version : Inverter batteries

11-08-2012, 11:16 AM
I found some very good discussions on inverter batteries in the old forum. The posts are all several years old and I'm guessing things have changed some. We need to replace our batteries in the Spring and would appreciate any advice. We currently have 6 - 6V lead acid batteries. Should I replace with same? Someone mentioned golf cart batteries, what about those?

11-08-2012, 11:53 AM
I think the "golf cart" batteries are just like what you have - 6V lead acid, but I may be wrong. When we purchased our first HB I replaced the house batteries. I researched and got lots of different opions on what are the 'best" batteries to get. After much reading, we settled on good old inexpensive "golf cart" batteries from Costco (same can be found at Sam's Club or maybe even Walmart). $60 each. They have had heavy use for 6 years and still going strong.

11-08-2012, 01:27 PM
You probably found my old post about my batteries then. My inverter can be set up to accommodate several different types of batteries from lead acid to AGMs. I settled upon AGM deep cycle batteries which ran me $125 each installed with custom 4 gauge wiring. I bought a total of 8. Our boat will go all day on the batteries as long as I leave the stupid rope lights off - those things lika-da-juice!

If you're in the middle TN area, the guy I bought them from is in Murfreesboro and will likely sell them at whole sale price. PM me if you're interested.

11-08-2012, 01:28 PM
I have twelve 6v golf cart batteries for my inverter. A lot of people like AGM. I just don't see the cost difference being worth it. Go to Sams or Costco, treat them nice (check water levels, do not discharge them too deep), and they will last 4-8 years.

11-08-2012, 08:15 PM
You need to do some research on batteries. First, batteries are divided by type, starting and deep cycle. Starting batteries are used for starting engines and powering some equipment, Deep cycle batteries are "house batteries". They are used to power most of the DC appliances, and run some AC appliances through an inverter. The 6 V batteries mentiond are deep cycle, sometimes called golf cart batteries because they are commonly used on golf carts. You will find there are people who swear that 6V batteries are the best way to go, and others who say 12V deep cycle batteries are the best. Actually neither is right ( hear the yelling in the background?)

They awful truth is there is no best. You need to buy batteries that suit your needs. Plus that there is no "best brand" . Almost all batteries sold in the USA are made by a handful of companies. The two biggest are Johnson Controls, and a company in China called Guangzhgou (SIC)t. Almost all of the batteries sold here are made by those two and third party labeled and sold as everything from CostCO and Walmart, to Sears Diehard. The only real difference is the price. There are some made here and sold under the makers name. For instance Interstate and East Penn
For more info see:
Batteries, Everything You Need to Know. http://newboatbuilders.com/docs/BatteriesEverything.pdf
Car and Deep Cycle Battery FAQ http://www.batteryfaq.org/
Batteries: http://newboatbuilders.com/pages/electricity3.html

Advantages to 6V: smaller, readily available. Last about 6 years if properly maintained
disadvantages: you have to buy twice as many batteries, Weight

Advantages 12V; Readily available, you don't need as many batteries, also lasts about 6 years if properly maintained
Disadvantages: bigger than 6V, cost, weight

What you need to watch out for is "marine Batteries" which are typically sold at Walmart, K-mart, West Marine, and many other places. These are often sold as Deep Cycle but are not true deep cycle. 6V batteries are true deep cycle batteries. True deep cycle 12V batteries cost more than the "Marine Batteries". Marine batteries are actually combo deep cycle/starting batteries that have both thin plates for starting and thick plates for deep cycle. True deep cycle batteries have very thick plates.

11-09-2012, 08:08 AM
I run 4 ALPHA CELL premium gel 165 GXL- 12 volt. They are used by phone companies for standby use. They are a little pricey but, have an 8+ year life. Some phone companies change them out every year and we have a source to obtain them.

11-09-2012, 11:15 AM
I run 10 Sams Club 6volts. They were the best bang for the buck and Amp hours.

11-09-2012, 11:28 AM
Just make sure your charger will accommodate the types of batteries that you choose.

11-09-2012, 01:51 PM
There ARE better batteries out there than golf batteries, but they are hard to come by and EXPENSIVE. I agree with JTAlberts, golf batteries give you the best bang for the buck.

11-11-2012, 10:12 AM
8 - Costco 6 volt golf cart batteries. I have built my system piece by piece, currently have 550 watts of solar but will upgrade this winter to 750 watts feeding a 60amp output morningstar charge controller. Batteries feed a 2,000 watt Xantrex inverter. I two wish I would have gone 48 volt, and I may yet. I plan on upgrading to a 3,000 watt inverter in the near future.


11-11-2012, 04:27 PM
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.

Frantically Relaxing
11-12-2012, 12:57 PM
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...

11-13-2012, 03:33 PM
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.

Frantically Relaxing
11-13-2012, 10:05 PM
I've heard that the "lion" batteries, or some of them anyway, can be pretty fickle about charging and mininum/maximum voltage values...

11-14-2012, 06:02 AM
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.

11-14-2012, 07:13 AM
Check the amp-hour rating. Not all golf batteries are the same. If they won't tell you, there's a reason.

11-14-2012, 11:47 AM
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

11-14-2012, 12:01 PM
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.

11-14-2012, 03:35 PM
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.

11-15-2012, 05:01 AM
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.

11-15-2012, 12:09 PM
You raise a good point about one battery pulling down the whole bank. It is a good idea to use a multimeter once in a while to see if all the batteries in a bank are the same voltage. If one is bad, replacing it is a good idea even though the new battery will now die at the same time as the rest of the batteries in the bank.

I've never rotated batteries because, in my case, moving an entire battery bank increases the chances of my doing something stupid like dropping a wrench onto a live battery or breaking a battery case while torquing down terminal bolts. If you ever have reason to take out a battery bank anyway, rotating would be a good idea.

Instead of rotating batteries, it might be a better to put the time into using a more advanced method of making parallel connections. Bus bars on positive and negative are still in their infancy, but they solve problems of jump wire resistance. I think we'll see more of them. Here are a couple of examples:



The trick with bus bars is that the cables from the batteries to the bus bars have to be identical length. You also need a fuse on the positive side of each paralleled battery or battery set. The fuses look like this:
If you want to parallel four batteries (or four sets of two batteries) there is a way to do it that keeps all of your cable resistance the same for the whole battery bank. It is method 4 in the attached link: http://www.smartgauge.co.uk/batt_con.html

L-16 pricing suffers from the "Walmart problem." If you are comparing apples to apples, L-16s and GC2 golf cart batteries from the same vendor will be the same or nearly so on a cost per amp hour basis. I last compared Fulll River brand AGMs and they were within a penny per amp hour of each other. Problem is, you can't stop by Costco or Walmart and pick up a large L-16 industrial battery like you can a golf cart battery. Try as they might, the brick and mortar stores that sell batteries like L-16s can't compete with the Walmarts of the world. The golf cart batteries from Costco or Walmart still work out cheaper per amp hour than where you have to go for an L-16.

There is weight. Golf cart batteries at about 65 pounds aren't that bad. I can lift a 115 pound L-16 by myself, but would lots rather do it with a friend holding the other side.

11-15-2012, 08:19 PM
Problem with the multimeter is you'll probably have to disconnect each pair and let them sit for a while before testing. Otherwise the remaining good batteries will try to charge the bad one. However checking water level frequently is a good place to start.

We had a thread a while ago about trying to come up with a way to remotely monitor each battery in the set... but I'm not sure if anyone actually came up with anything that sounded like it would work.

I can't see much improvement with the bus bar, all the leads going to the bus would have to be the same length and this would just add more wire and resistance. I tried having cables made up once with 3 cables crimped together at one end, but it wasn't really satisfactory. I think just keeping all the connections clean, tight, and coated with anti-corrosive is about as good as any.

I thought about the fuses too, thinking that if a battery went bad the fuse would blow and disconnect that set, but the fuses have to be such high amperage that I'm not sure they'd ever blow. For an inverter each pair of batteries would need say a 100a fuse; even more if the bank is to be available for emergency starting. And if one fuse did blow, the additional load on the remaining pairs would probably cause those fuses to go, too, leaving you DIW. I tried it once but eventually removed them. I do have an external fuse for the inverter, one for the house load, and one for the pumps and emergency equipment which are on a separate circuit.

11-19-2012, 04:01 PM
I remember the monitoring system thread. I think we all decided that a multimeter didn't tell you anything about the parallel batteries, but gave valuable information to compare the voltages of the two 6 volt batteries with series connections to each other. If that's right, as long as you have at least some serial batteries, a multimeter should give good information to compare two batteries in the series sets to each other, even if the batteries are still connected. Maybe that's another reason to favor series connections over parallel connections.

The goal of a bus bar system is that all of the parallel connections have identical resistance. The up side of that is that things stay equal. The down side is that some of the cables are longer than they need to be. If the bus bar is near the center of the battery bank, the parallel cables are all about half the length of the battery bank. That yields shorter cables for the batteries that are farther away than the half way point, but does result in longer cables for the other half of the bank. It shouldn't be that much worse in terms of overall resistance and would give a huge improvement in balancing batteries.

Fuses would indeed be a pain if you had to use a house bank to jump start an engine in a pinch. You're also right that the individual battery fuses won't protect against charge differential between batteries in a bank. The fuses are just there to comply with ABYC rules that require a fuse within 7 inches of the battery for wires that aren't in conduit. It is possible that some surveyors would treat the bus cables like jump wires that don't need fuses. Maybe Ike could tell us more about that.

11-19-2012, 07:18 PM
You guys are REALLY getting anal about this. I n the real world a few inches difference on short cables doesn't mean Diddly Squat. To me. the installations appearance is important. Over length cables create a visual mess.