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Charging 12V Batteries: Best Practices

Alan Knight — Sun, 11 Sep 2011 18:33:26 +0000

This is a guest article written by Alan Knight, one of the more frequent contributors to this website.

What Happens to Batteries when you Overcharge them?

Do not attempt to charge a 12v battery with anything other than a 12v charger, whether it is a flooded unit, Sealed Lead Acid (SLA), gel or AGM. SLA and AGM batteries require a charge rate of about 1/10th of its Amp-hour rating. If you charge at a higher rate the battery can build up excessive heat and start to ruin.

In a Gel unit, airways will form over time in the gel silica. The gel hardens when it gets too hot and once it hardens it has a reduced ability to transform soft lead sulphate back to sulphuric acid thus reducing the surface area that the plates contact with the electrolyte. This means less of the plate can take part in the discharge - recharge chemical reaction.

An AGM battery will over heat and expel the electrolyte. The electrolyte transforms into gas and is able to escape through the one way valve and reduce the unit to scrap as it boils due to no liquid to cool it down.

A flooded unit will also overheat and buckle the end plates. This is clearly visible through a bulging on the side of the unit, although this will take a few months of constant over charging to achieve as batteries charging voltages are graded to a minimum and not a maximum.

What Type of Battery Charger Should You Use?

Use a three or five stage charger which incorporates an automatic 15v-16v equalization charge and your battery will last for years longer than its warranty. Stay away from the cheap 4-6 Amp chargers since these are unregulated and can destroy your battery very quickly.

When charging allow the electrolyte to mix by bubbling. Contrary to some literature, this is not the sign of a defective battery. It is the reason that there are vents on batteries - to allow any gas pressures that may build up during the process to escape without causing any explosions.

Don’t Spend Money Needlessly: 10 Tips That Will Help You Maintain A High-Quality, Long-Lasting Tent

Sun, 11 Sep 2011 08:30:19 +0000

This is a guest article written by http://hubzz.net - a gear review site offering personal and quality reviews of various items.

When you’ve decided to go camping for the weekend…whether it’s in your own backyard or out at the lake, you need a tent that can give you both comfort and protection from the outdoors. Now, if you want the tent your purchased to last a lifetime, there are some things you need to know to keep it looking its best… at all times.

10 Tips To Caring For Your Camping Tent To Have It Last a Lifetime

1 – Purchase A Quality Tent

The first thing you need to do is purchase a high-quality tent. One such durable tent is the Eureka Titan Family Tent Review, which is made of high-quality material and has lots of pioneering features. Why Eureka? It makes tents for, not just families, but the military as well. If you’re looking for a good quality tent, you can’t go wrong with Eureka.

2 – Setting Up The Tent The Right Way

Once you have purchased your high-quality, top of the line tent, it’s time to practice on setting it up… right. Be sure you carefully read the instructions that come with the tent. Once you do this, take time out to practice setting it up. It’s important you do this before camping. Why?

By practicing beforehand, you’re not caught outside in nasty weather trying to set it up. Learning about it ahead of time ensures that you do know how to set your tent up. Tents that have not been properly set up have an increase chance of tearing.

3 – Staking The Tent…Whatever The Weather Or Geography

Be sure you have the stakes that will fit the geographical area that you’ll be camping in. For instance, rocky soil, sandy beaches and snow each have a staking requirement. You should also make sure that all stakes have the right amount of tension. If not, a big gust of wind and rain can rip or tear apart a tent that’s not been properly staked.

4 – Place A Cloth/Tarp On The Ground

Make sure you use some type of cloth under your tent to protect the bottom of it. The ground cloth will protect the cloth from sticks, stones and rocks. It also helps to keep the water out. You want a ground cloth that’s smaller than the tent of the floor but only slightly smaller. If you get one that’s bigger than the tent, you increase the chances of the tent getting wet.

Bear in mind that the ground cloth is additional layer to the floor, which can make laying or sitting down more comfortable for you. A tent cloth is cheaper than purchasing another tent. If you want your tent to last, you’ll need a tent cloth to do so.

5 – Sun Protection

It’s important to note that your tent’s fabric will break down because of the sunlight. So, if you’re looking to protect your tent from long-term exposure, you’ll need to do a few things:

A – Set the tent up in a shady area (if you can find one).
B – Protect the tent using a tarp.

6 – Keep A Clean Tent

If you’re looking to prolong your tent’s life, you need to keep it clean.

A – Keep it closed so dirt and insects won’t get in.
B – Use another tarp to keep the floor covered.
C – Don’t wear shoes inside your tent.
D – Have a dustpan and wisk-broom to clear out leaves, dirt and other things that get inside.

7 – Carefully Clean The Tent

To keep your tent clean and in good shape, you should read your tent manufacturer’s instructions to find out what you need to do is keep it clean. The majority of tents can be washed by hand using just cold water. Make sure you air dry it. You may be tempted to wash it using your washing machine or drying it with a clothes dryer. However, these machines can ruin the tent.

Remember, your tent isn’t the only thing that needs to be cleaned. You should also wash off the stakes, poles and ground cloth too. Again, cold water and air dry.

8 – Keep The Tent Dry

Before you go and store the tent, be sure it dries out completely, regardless of why it got wet. If moisture is caught inside the tent, mildew, mold and odors can become trapped. Mildew can weaken the tent fibers and damage the waterproof coatings.

If you do have to leave before it dries out, leave the tent bag unzipped to dry out. When you arrive home, be sure to take it out immediately to wash and leave it to air dry.

9 – Storing the Tent

You want to make sure that your tent stays in a cool, dry place. Never place the tent on a garage floor since chemicals can damage it. Be sure the tent stays inside its bag at all times. You should have separate bags for your tent and stakes.

10 – Protect The Tent Poles

You can maintain the poles strength and looks because spraying them down with silicone lubricant. You don’t want to scratch your tent poles so be careful. Poles have anodized coating on them so the metal stays protected from all kinds of weather elements. If this gets scratched, the poles will rust.

Essentially, if you take careful care of your tent, it can last you a lifetime. The most important tip you can remember is to read the owner’s instruction manual so that you protect your investment to last your lifetime.

How to Make 36 Volts from 12 Volt Batteries

Robin — Tue, 06 Apr 2010 03:13:17 +0000

Recently George asked in the comments on our article about connecting batteries in series and parallel at the same time how he could make 36 volts from 12 volt batteries, while at the same time make the capacity (amp hours) add together so that each 12 Ah cell would combine to make at 36 Ah total battery. Here is what he wrote:

I have three 12V12Ah batteries. I need 36V36Ah.Is the following thought correct ?

I connect all the plus together, then all the minus together. The result is: in parallel I would have 12V and 36Ah.

Then I connect from first battery plus to second battery minus and from the second plus to the third battery minus. This would be series and I achieve the 36V.

Thanks for your help Robin.

And the answer is no, it doesn't work quite like that. In isolation George is correct. If all he wanted to do is make 36 Ah at 12V then his first idea would work. Three 12 volt batteries in parallel makes 12V @ 36 Ah. And then if he took those three batteries, disconnected them, and reconnected them in series like in his second idea, he would have 36V, but only at 12 Ah.

But if you need to do both at the same time, it gets a little more complex. Take a look at the article and study the diagram. In the example we needed 24 Volts and 200 Ah. We had four 12 Volt batteries, each with 100 Ah. We took two batteries in parallel to make one big battery with 12 V @ 200 Ah, did it again to make another big battery with 12 V @ 200 Ah, then took those two batteries and put them together in series to make 24 Volts at 200 Ah.

George, what you need to do is get (brace yourself) ... NINE batteries. Take three of them, put them together in parallel to make one big battery with 12 Volts and 36 Ah, then do it twice more to make 2 more BIG batteries at 12 Volts and 36 Ah. Take all three of your big batteries, and put them together in series to make a HUGE 36 volt battery, with 36 Ah. Like in the last article, I've drawn a simplified diagram that shows how to do it.

So this might seem a bit much, especially since you're only working with 36Ah in total. You're probably better off just buying three 12 volt batteries with the minimum capacity you need - you could also look into getting a 36 volt cell as well. Either way, the concept above stands. I hope this is useful to you.

24 Volt Load on an Existing 12 Volt System with a Battery Selector

Robin — Wed, 24 Mar 2010 03:39:07 +0000

We received a question from Michael Correale today asking for some help on wiring his 24 volt horn to his 12 volt boat electrical system. Here is what he wrote:

Ok, I am that guy who had to go and buy the 24 volt horn for my boat with a pre-existing 12 volt system. I am unsure how to get 24 volts to the horn switch without sending 24 volts to everything and frying a lot of $$$$ in electronics.

My idea is this: I would take a hot and ground directly from each battery and run it to the horn area. At this point I would connect the positive from one to the negative of the other leaving the other ground to be the 24 volt connections. My main issue is (considering that it will work) can the 24 volts go to the other stuff on my boat when the switch is on both batteries.

Michael, it's a good question. The answer is NO, DON'T DO IT!

If you have two batteries right now with a battery selector switch, such as a Blue Sea Systems 9001E shown in the image above, you cannot do what you're asking. The battery switch is designed so that you can choose to run 12 volts from either battery, or 12 volts from both batteries. In this case the switch connects the batteries together in parallel. The negatives on your batteries will already be connected together.

If you were to take the positive from one and the negative from the other and connect them, while at the same time the negatives from both batteries are connected (or at least both connected to ground) then you will short one of the batteries out. This will very quickly melt your battery, or melt the wires, or... melt something!

A better approach would be to install a transformer to step up the voltage to 24 volts from 12. These can be fairly cheap at an electronics store, but since you are in a marine environment it's worth getting a more expensive one designed to withstand the corrosion.

Alternatively, you could always go buy a 12 volt horn! And Michael, if you are still reading and I've somehow missed your point, clarify it below in the comments and I'll take another stab at it. Thanks for asking!

Expedition Travel Laptops for Under $1000

Robin — Fri, 22 Jan 2010 07:31:51 +0000

Yesterday freegeographytools.com (a great resource if you're interested in mapping, GPS, and GIS applications - they offer a lot of insights and opinions on various free software) wrote the first article in a series on building an inexpensive GeoPad. They are defining a GeoPad as a small touchscreen computer, field ready, loaded with built-in GPS tracking, navigation, and data collection software, as well as GIS utilities. It's a great idea, and while there are products on the market designed specifically for this, they are quite pricey. The point is to find and build something for under $1000.

Their series focuses on applications designed for professionals and hobbyists looking for a field workstation. But I see the application extend to the expedition traveler - a lot of similar needs, along with a few others. Let's talk about finding the right laptop - the core of the system.

The Specifications: What an Expedition Laptop Needs

While the field professional needs things like a durable computer, no cables, and long battery life, the overland traveler has a few other uses for an expedition laptop - email, blogging, costing spreadsheets, photo storage, video storage, and maybe even video editing. It's something you want to mount in a car or at least have easily accessible when driving. You want to take it to the internet cafe, update your emails at the campfire, transfer photos from your camera by bluetooth, drag it on a canoe with you up the Amazon river...it's got to be durable, and rugged, and reliable.

So combining the features of a GeoPad and an Expedition class laptop I get

rugged, waterproof, dustproof, drop proof
touchscreen (digitizer style - read this post on the difference)
convertible tablet/clamshell style
WIFI
built-in GPS (no annoying cables)
long battery life
at least 120 GB hard drive (for you photos and videos)

The Panasonic Toughbook CF-18

The Panasonic Toughbook is listed as the first choice on the Free Geography Tools post, but quickly dismissed due to it's prohibitive cost (a new tablet Toughbook CF-19 starts around $3000, and then you add the options like integrated GPS). But I disagree. If you lowered your standards just a bit, you can find a the previous Toughbook tablet computer model, the CF-18 on eBay for around $600 USD.

It would come with a touchscreen and WIFI, and be in pretty decent condition. Many of the models have upgraded hard drives (they came stock with 60 GB back in the day) and if you look hard enough you'll find one with Bluetooth and if you're really lucky, built-in GPS.

But don't spend too much time trying to find all of that in one computer. Instead get a model in good condition with an upgraded hard drive. There are lots of those available. Then jump over to CustomToughbooks.com and buy one of their GPS/bluetooth upgrade kits for $175 USD and install it. You'll get a modern GPS module, much better than the stock ones that came with the CF-18, and you'll get the bluetooth as well. The downside is you'll need a bit of handywork to install the GPS module, but the installation documentation is available on the CustomToughbooks website and it looks fairly straight-forward.

The CF-18 is slow: Will it work?

It's a valid point. The CF-18 came with a 900 to 1.2 Mhz Pentium M processor, quite slow by today's standards. It will be happy running Windows XP, but don't try running Vista. I'm not sure how well Windows 7 will work but my guess is it would be too much for it. And you'll have to forget video editing. Well, not forget it, but expect to take a long time waiting for your scenes to render. Large photo editing would be a problem too, but storing and viewing photos and basic tasks available in standard photo album software should be no problem.

For emailing, working with spreadsheets and blogging - no problem. Mapping and GIS? Also a snap especially for field work. Data collection, mapping, and navigation don't need much processor speed.

Other Ideas?

Feedback, experiences, questions - always welcome! If you've got something to say, do so in the comments section below. In the meantime, take a look at some current eBay auction listings fro CF-18 Toughbooks. If you're keen on buying one, take a look at our article on Buying Used Panasonic Toughbooks. It gives you some good pointers on what to look for, especially from eBay auctions.

Panasonic ToughBook CF 18 11Ghz 512MB 40GB WiFi GPS U
787.99

Panasonic Toughbook CF 18 MAXIMUM 320HD WARRANTY DVD RW GPS
995.00

THIS WEEKEND ONLY PANASONIC TOUGHBOOK CF 18 FULLY RUGGED TABLET GPS BLUETOOTH
941.23

THIS WEEKEND PANASONIC TOUGHBOOK CF 18 RUGGED TABLET GPS
941.23

THIS WEEKEND PANASONIC TOUGHBOOK CF 18 RUGGED TABLET GPS 2
941.23

THIS WEEKEND PANASONIC TOUGHBOOK CF 18 RUGGED TABLET GPS 9
941.23

Topographic Maps of Brazil: Who Uses Them?

Robin — Mon, 07 Dec 2009 05:33:03 +0000

One of our recent customers to purchase our South American Topographic Maps Series 2 which covers almost all of Brazil (as well as most of Peru and parts of Bolivia) had a few questions for us after downloading the 124 maps from the OverlandResource.com client download center (you can do the same by purchasing the maps here). The following is a transcript of the emails (edited for clarity):

Hello. I have just purchased the South America Topographic Series 2 and I am having a few problems. I started to download what appears to be part 1 of 3. I had to stop part way through and when I tried to continue it went straight to part 2. I have now successfully downloaded part 2. Do I need to download part 1 and 3 as well or are they the same as I've already got? My second problem is that I don't have any index to the maps or any software with them. I've also tried opening the .MAP files but my computer doesn't recognize them. Please can you help with this?

What the Maps Cover and How to Use Them

The customer purchased Series 2 of the South America map series so there was no need to download the other Series 1 and 3.

Series 1 covers latitudes 12 North to 4 South
Series 2 covers latitudes 4 South to 22 South, (this is the one he purchased)
Series 3 covers latitudes 22 South to 56 South.

To index the maps you need to have software such as OziExplorer (http://www.oziexplorer.com) or Fugawi (http://www.fugawi.com). But really, as I've noted in previous posts, download and get to know OziExplorer. The .map files are created by and for OziExplorer. They are really just text files that contain all of the information to place the images of the topo maps in the correct coordinate space.

This software will read the .map files and georeference them, index them, and make it easy to navigate, view, and zoom between the maps. It will also add GPS capability to them (only useful when you're actually in South America.)

Back to the Title: Who Needs Topo Maps of Brazil?

I received a final email, and here is what he said:

Thank you very much for the very quick response. I've been living in Brazil for the past 3 years, visiting here for 6 years altogether, and it's almost impossible to get a decent map. I'm trying to run a paragliding guiding business so I'm hoping these will be very useful.

According to Steve, it is hard to find good detailed maps of Brazil. Hopefully the packages we sell are use to him. I took a look at his paragliding website, and wow does it ever look like fun! So on a side note, if you're going to Brazil, check out his site and look him up.

Steve can be found running his paragliding business XCBrazil.com in Bairro de Lourdes, Brazil.

Translating Russian Topographic Maps using the OziExplorer Names Database

Robin — Mon, 07 Dec 2009 04:54:57 +0000

I thought I'd write down an email exchange I had with a recent customer who purchased one of our South American Topographic Map series. As you can read on the download page, the maps are in Russian, and normally not of much use to us English speakers. To remedy that we provide a database of geographic names that can be overlayed on the maps through the use of OziExplorer's Names feature. This is not one of the most widely known features of OziExplorer, so it is no surprise that we get questions on it from time to time.

Here is a copy of the emails so that you can also benefit, edited for clarity:

G'day Robin,

One question I have is the maps I have looked at so far don't have the english translation in red as have the maps on the website. It would be very handy to have the translated version if possible.

The English translation only works within OziExplorer. OziExplorer has a names feature built into the software that will load a database of names and place them on the map at the correct coordiates. The coordinate and name information is all stored in the database. This database is included in the download.

Download OziExplorer

If you purchase one of our map sets, make sure you've got OziExplorer. It will add huge value to the maps. You can download a trial/demo version here at the OziExplorer website. After you install it you will have 2 options to run - either the shareware or the trial. Choose the TRIAL version. You should be able to use all the minimum features to view the maps with the names. For full functionality you will have to purchase the software from them. The email chain continues:

G'day Robin, I'm still having trouble with the english names coming up. I have the latest Oziexplorer ( 3.95.4s ) installed and get the maps up OK but then I'm not sure what to do next to bring up the english translation. Hope you can help. Kindest regards.

Using the Names Feature in OziExplorer

In OziExplorer on the menu bar on the top is an icon called "Name". Click it and a side pane opens up. Click the "load" button and navigate to the south american .names files that came with the download. It defaults to installing the names files to c:\oziexplorer\name search.

Select the country name file that you're interested in, and load it.
Load the map you're interested in looking at.
On the Name sidebar, check the "On Map" box. This will filter the list of names to only the ones that are on your map. The names list is really long, since it's for a whole country.
To display the names, press the button on the names sidebar that has a while empty circle in it. The names will plot on the map.

There's also a really detailed help section on how the names work within OziExplorer - it's worth your time to give it a read and understand how all of this works.

Also note that the names files have different types of information as shown on the Feature Code pull-down. You can further filter what shows up on the map by selecting a specific feature code, including Cities or Towns, Administrative Regions, Hydrographic Features, Vegetation, or Roads and Rail.

Which Battery Post Do You Connect First: Positive or Negative?

Robin — Sat, 12 Sep 2009 03:38:25 +0000

Someone came here the other day looking for the answer to this question - which battery terminal should you connect first. It's a great question. We're talking about automotive batteries, and whether you connect the positive terminal or the negative terminal first.

You've got the hood open to your car, you've just done some electrical work of some kind and the batteries disconnected. Now it's time to reconnect them, and you want to make sure you continue to work with the best and safest practices.

The Short Answer

The short answer? Connect the positive first and the negative second. This way you eliminate the risk of creating a short while you're connecting them. If you want to be sure then read below for the caveats - there are situations where this doesn't apply and/or you can damage equipment. In the meantime, for most of us, here's an explanation of why:

Short Circuits in Car Batteries are BAD!

Imagine you've connected the negative first, and now you're on to the positive side. You slip the battery clamp over the positive terminal. Maybe there's a tiny spark as your radio memory draws that tiny bit of power. But no worries, that little spark has so little current running through it that nothing happens. Next you take your half-inch wrench or 12 mm or whatever it is wherever you live. You start tightening the clamp tightly to the post. As you turn the wrench around it comes close to the body of the car and suddenly the wrench slips off the nut and slams against the body while still touching the the positive terminal.

Don't try this at home kids! If a circuit is completed (it might not due to the insulative properties of the car paint) but if the circuit is completed you'll have a great spark show on your hands, and the point of greatest heat will loose. You could melt a hole in your car body, you could melt the battery post (most likely being the softest metal), you could melt and deform your wrench, and of course you could burn yourself.

For most of us, I think we can agree this situation sucks. If you had not connected the negative terminal first, then the body would not be connected to the battery system, and the short would not have been possible.

Connection Sequence of a Car Battery

The car body is connected to the negative terminal, the negative terminal is connected to the positive terminal (and in between has harnessed the electrical potential in the battery), the positive terminal is connected to the electrical system, and each item in the system is connected to the car body. This is a complete circuit.

In the short circuit example above you actually "shortened the circuit". You cut out the electrical system, and just connected the battery straight to the body. If the negative terminal was not connected, then the circuit would have remained incomplete, and you would not have had a short.

Clear? If not, ask in the comments section below and I'll try to clarify. And the moral is connect the positive first, then connect the negative. Go ahead and slip with the wrench all you want when connecting the negative - it's already connected to the car body, and you won't create a short circuit.

The Caveats

Here are a few reasons why you might connect the positive terminal first rather than the negative terminal.

You've got a positive ground vehicle. Like an older Series Land Rover - yes you know who you are! The electrical systems in those cars are backwards to most of the rest of the cars in the world. Yes, the English had their reasons. If you've got a positive grounded car, then just do it in the opposite way.
You've got equipment that needs the ground to be connected last. There are some pieces of specialized electronics (poorly made I'll admit) that need to be connected in a certain order or they blow internal fuses. If you've got them, you probably know all about it and you also probably curse yourself for not spending a bit more on a better engineering product!

Any more? Leave a comment below if you know of any!

What is an Amp Hour and How to Calculate Battery Capacity

Robin — Wed, 26 Aug 2009 05:23:07 +0000

An Amp-Hour (ampere-hour, Ah) is a way of describing a battery's capacity - how long it will run before it is drained down. But I can be be more specific: the amp-hour rating for a given battery is the maximum amperage that can be drawn continuously until the battery is completely discharged, flat, empty, drained, dead, over a specific time period.

How Are Amp Hours Determined?

Battery manufacturers complete tests on their batteries to give them an Amp-Hour rating. A typical time period for a test is 20 hours, but it varies - batteries are tested over different periods, such as 24 hours, 75 hours, even 100 hours. But as you'll see below, a 100 Amp-hour battery tested over a 100 hour period (i.e. 1 amp drawn for 100 hours) will not have the same capacity as a 100 Amp-hour battery tested over a 20 hour period (i.e. 5 amps drawn for 20 hours). It turns out that if you drew 1 amp continuously from the 20 hour test battery, it would last for 110-120% longer than on the 100 hour test battery. I'll (try to) explain that later.

Let's Do an Example Calculation

Suppose you have a 100 Amp-hour battery, tested over a 20 hour period. 100 Amp-hours divided by 20 hours = 5 amps. That means that the battery manufacturer claims the battery can sustain a 5 amp load for 20 hours until the battery is completely dead.

That's great, but now put it into realistic terms. For starters you don't want to drain a battery to it's completely flat, empty, dead state as it will significantly reduce the life of the battery. A good rule of thumb (battery type depending) is that you should only drain a battery down to 40% of it's original capacity, or in other words you've only got 60% of the battery to use. This number should be stated by the manufacturer in the documentation.

Back to the 100 Ah, 5 Amp load example: We said you had 20 hours of time when drawing 5 amps, but in fact you only have 60% of that time, so 20 hours x 60% = 12 hours.

Up until now, what we have said is true because we have used the same amperage over the same time period at which the battery was originally tested (20 hour rate). So what if you took your 100 amp-hour battery, but wanted to draw 10 amps from it until it was at the safe discharge level (60%)?

Do the math: 100 Ah / 10 Amps x 60% = 6 hours, right?

Wrong.

The More Amperage You Draw, the Lower the Battery Capacity

That's right, the effective amp hours available drops with the more amps you draw. All of a sudden that 100 Amp-hour battery is not what it says it is. Ok, back to the numbers, lets try to keep this clear:

Using the 100 Ah, 20 hour test battery, at 5 amps draw, you get the full 100% of the battery rating (that's how the battery was tested in the first place, so you should get all 100%!). But step up the amperage to 10 Amps, and you will lower the capacity of the battery by about 10% (or 90% remaining).

That makes 100 Ah x 90% = 90 Ah / 10 Amps draw = 9 hours x 60% (max safe discharge number) = 5.4 hours. And that's quite a difference from the 6 hours you thought you had.

Where Did I get the 90%?

I'm going to stop here and leave you hanging - except to say that there's a relationship defined called Peukert's Equation, and that's where the approximate 90% comes from. The Peukert Equation quantifies the above phenomenon so that you can predict how much time you'll actually have on a battery given a specific discharge rate.

What's Next - How About A Helpful Tool?

My guess is that if you're still reading this your about ready to start figuring out how many batteries you need, and you could really use a little help with the calculation. You might have gone to the Wikipedia site above to investigate what Peukert had to say, but exponents aren't really your thing, and you can't find your calculator anyway.

Connecting Batteries in Series and Parallel at the Same Time

Robin — Fri, 14 Aug 2009 05:53:39 +0000

A few days ago Larry Amato from Amato Consulting replied to our previous article that describes how to create 24 volts from two 12 volt automotive batteries. He continued our thought process by showing that you could take four automotive batteries and connect them in both series and parallel at the same time to achieve a 24 volt battery bank with double the capacity of a single 12 volt battery.

His application was for a solar installations where capacity is usually important, along with a typical requirement for 24 volts which is a common voltage on solar panel systems.

He describes how to do it using a matrix - I had to take a pencil to write it down to follow what he was saying. Then I had to think about it for a bit, so I figured some you might have had to think about it for a bit too...hence this article. I'll try to give some more detail to break it all down. Here is what he said:

My need was 24VDC power with 200 amp hours.

I purchased 4 each 12VDC AGM 110 amp hour batteries. Picture the 4 batteries in 2 rows (R) x 2 columns (C).
1) R1C1 positive is connected to R1C2 positive.
2) R2C1 negative is connected to R2C2 negative.
3) R1C1 negative is connected to R2C1 positive.
4) R1C2 negative is connected to R2C2 positive.
5) R1C1 positive and R2C1 negative provide 24VDC power with 220 amp hours.

I take the R1C1 positive and R2C1 negative and run through a 24VDC Photovoltaic Charge/Controller which is connected Solar Panels with output to my various 24VDC devices including Programmable Controller, Instrumentation, and Spread Spectrum Radio.

Like I said, you need to draw it out. And for your benefit, I've done that (click to enlarge):

On the left is what Larry describes, and on the right is what I would have done. I've gotta say, Larry's way is WAY better. Less wires, less complex. So let's talk about it.

"My need was 24VDC power with 200 amp hours"

24 volts from 12 volt batteries: if you read our last article then you know that when you connect batteries in series, the voltages add together. So Larry took two of his batteries and connected the positive and the negatives together. Then he did it for the other pair. On the diagram, each pair is vertical - the negative of a top battery is connected to a positive of the battery directly below it. And so now there are two 24 volt battery banks, side by side.

On to the second criteria, 200 amp hours.

It's pretty tough to find an automotive battery that stores much more than 100 amp hours. In this case Larry found some 110 amp hour AGM batteries. But how do you get 200 amp hours? I describe this in detail in the last article, and if you've read it you know that if you connect batteries in parallel the amperages add together.

And so he added the amperages of the two battery banks together by connecting the positives on each bank and connecting the negatives on each bank. Presto, 100 amps plus 100 amps is 200 amps.

Lastly by taking a lead from the positive and a lead from the negative, he's got a 24 volt system, with the full capacity of 200 amp hours in reserve. On the image above you'll see what I call "our method". While it does the same thing, it's more complex, and after seeing how Larry does it, I'm converted. See if you can follow the differences - but really, they each do the same thing.

A few paragraphs ago I mentioned the AGM batteries that Larry purchased for his application. AGM battery - what is that?

What are Advanced Glass Mat Batteries?

AGM stands for Advanced Glass Mat, and is a type of deep cycle battery. Battery types is a whole other article that we need to write, but if you are reading this and you care to contribute, go ahead and leave a comment below. Hey, if you want to write a full blown article and give some good detail on what an Advanced Glass Mat battery is, go to our article submission page and do so - we come with benefits!

On to the second criteria - 24 volts. You also know from the last article that when you connect batteries in series, the voltages add together. So Larry then took his two 12 volt battery banks, and connected them together in series - in other words the negative of one bank to the positive of the other.