Want to understand current between batteries in battery bank

[dsly]

Thank you!!

I will try to straighten you out.

Look at these two specs and pay attention to the weight of a T-105 and T-105RE. Get it? RE = Renewable Energy. The T-105RE has 5 more pounds of lead in them. The warranty is also different as the standard T-105 is 12/24 and T-105RE is 24/60.

As for putting your battery in the basement is just fine. Use FLA or AGM. FLA is not going to freeze assuming it is charged up and warmer than -40 F. If your basement gets below -40 F move to a warmer climate knucklehead.

Thanks for the great info! I did see most of that when I did my due diligence reading the Batteries thread before asking the question, but the important part was the news that the t105 is a hybrid, and I will check out the RE version.
And if it gets anywhere near that cold OUTSIDE, let alone in the basement, I'm outta here!

[Mike90250]

... Are FLA deep cycles safe to have in a basement?...

They do generate a bit of acid mist from the tops of the vent holes. Will it harm anything nearby ?
Some people can really smell the sulfur from the batteries, some don't.

What is on the floor if one of them leaks acid, will it ruin your furnace or something else?

Finally, Moving them in and out, do you have an elevator ? Figure about 5 years lifetime before you have to replace.

Hydrogen, most houses & basements, are leaky enough that there should not be much hydrogen buildup. But if you think you have a well sealed basement, you may want to consider some sort of ventilation requirements.

[Sunking]

Just discovered this site, and after spending many hours reading, I think I am way over my head. I think I'm looking for "Solar Batteries for Dummies".
What follows is what I was going to post....note one of the suggestions was T-105s. Obviously they are not a good choice. Can you point me somewhere that would explain why?

I will try to straighten you out.

There are 3 basic types of Lead Acid Batteries.

SLI (Starting, Lighting & Ignition aka cranking batteries). As the name inplies they are made to crank engines. They are designed to deliver very high burst of current (called CCA or Cold Cranking Amps) for a very short period of time and be quickly recharged by a alternator. To do they use as many thin spongy plates as they can cram into the battery jar to maximize surface area of the plates thus to lower the internal resistance as low as possible. That i sgreat for starting engines, totally unacceptable for cycle operation. Thin spongy plates do not hold up when cycled. The either dissolve or sulfate up very quickly. If pressed into cycle service you may only get 50 to 100 cycles and they are toast aka boat anchors. All SLI batteries have a dead give away specification of CCA. If you see a CCA and no Amp Hour spec rest assured it is a SLI battery.


Hybrid batteries are next in line and come with many Marketing names like Golf Cart, Marine, Marine Deep Cycle, Leisure, RV Deed Cycle, Floor Machine, etc... Hybrids try to be both Deep Cycle and SLI batteries. They have fewer thicker heavier plates to get some deep cycle properties, but not as thick and heavy as a True Deep Cycle. They do have a place in Solar applications where you need either high charge or discharge rates. The trade off is cycle life. YOu will get a lot more cycles than SLI, but not as many as true Deep Cycle.

Deep Cycle batteries have the thickest heaviest plates and not all deep cycle batteries are created equal. The thick heavy plates means a lot of cycles. Depending on how deep they are discharged and over all quality can last up to 5 to 7 years with 4 being typical. However like any battery characteristic there are trade offs. A true Deep Cycle battery cannot be charged up or discharged at rates higher than about C/8 on average.

OK there are 3 sub groups of Gel, AGM, and Flooded Lead Acid. I am not even going to bother with Gel batteries as they are not suitable for RE applications.

AGM despite claims are either SLI or Hybrid. However they are extremely useful in RE applications where high currents are demanded. By there very construction method makes them very low internal resistance which means high current application. Some AGM's can be charged and discharged at 1C rate. AGM is also very useful in mobile applications or extreme cold climates. However AGM has one major trade-off. They cannot last as long as a good FLA deep cycle battery. They also cost significantly more than FLA.

OK no wlet's talk about your Trojan t-105. They became popular in the early days because there was no market for deep cycle batteries. T-105 and L16 back in the days were about the only thing available and old habits die hard. The T-105 is a Golf Cart Battery. What does that mean? It is a hybrid. It is still useful today and would be my pick where I need high current and mobility and extreme cold are not an issue. They will last longer than a comparable AGM and less expensive.

As time wen ton and solar became more popular, battery manufactures started offering Deep Cycle Batteries. Even Trojan has met the demand. Look at these two specs and pay attention to the weight of a T-105 and T-105RE. Get it? RE = Renewable Energy. The T-105RE has 5 more pounds of lead in them. The warranty is also different as the standard T-105 is 12/24 and T-105RE is 24/60.

As for putting your battery in the basement is just fine. Use FLA or AGM. FLA is not going to freeze assuming it is charged up and warmer than -40 F. If your basement gets below -40 F move to a warmer climate knucklehead.

[dsly]

Why not Trojan T-105s?

FWIW I hope you did not get Trojan T-105 batteries.

Just discovered this site, and after spending many hours reading, I think I am way over my head. I think I'm looking for "Solar Batteries for Dummies".
What follows is what I was going to post....note one of the suggestions was T-105s. Obviously they are not a good choice. Can you point me somewhere that would explain why? Thanks for putting up with newbies!!

"I've been trying to set up a small solar system in my rural setting, and can't seem to get straight answers about batteries. I have 4x30watt solar panels delivering 2 amps each at 13-17 vdc (different brands). I have three of them (identical) running in parallel through a Sunforce controller 7 A., and use this to charge a set of PowerBoxes (2x800; 1x1000). I use these Powerboxes to run LED light strips, and small appliances when the power goes out (all too frequent in the country north of #7).
We have a wood burning insert in our fireplace that runs better when the fans are operated. It will heat the whole house with the fans. What I need is a set of batteries dedicated solely to running the fans in the fireplace.
I did some reading (I'm a complete amateur at this), and AGM deep cycle seemed to be the way to go, since the batteries would be in the basement. Then I read that FLA batteries have a much longer life, will do more cycles at a greater depletion rate, and are cheaper. Then I read that what I need are a couple of T-105 golf cart 6 v batteries run in series. The thinking there was that they are cheaper, more heavy duty, will put up with greater discharge rates, can discharge them farther without damage. Then I read that they have about half the life of a FLA deep-cycle.
So, I seem to have come full circle, and am none the wiser. Better informed, perhaps, but none the wiser. Does anyone have any suggestions? Are FLA deep cycles safe to have in a basement?
I have a small generator to run any appliance requiring more current, so this system is only to run the fireplace fans, and perhaps a few LED light strips.
Would really appreciate any suggestions from anyone who has tried anything like this, or has some knowledge of these systems."

[inetdog]

...using this type of wiring method, using the smallest amount of gauge required, wouldn't you need larger and larger gauges as each level progressed to the load on the bank? (Basically between 2 batteries you may be only pulling 25 amps, but when those two are ran in parallel with another 2 you have a 50amp total current draw for that level?)

Absolutely.
As I said earlier: ... then you can determine the differing amounts of current at each level by looking at how many batteries connect to the loads through the same piece of wire.

There is a lot to be said for using small enough wire connecting to the batteries themselves to allow it to be easily bent and arranged. But keeping that in mind, bigger is still better and the cost of short pieces of larger copper is not going to break the bank.

[billvon]

What I mean by this is, say for example I have a battery bank consisting of 6 total 12v batteries run in parallel (throw all the discussion of going higher voltage aside for the time being). If I have a 150amp current draw on the bank itself and its in an ideal wiring configuration allowing for even current draw between the batteries (im dreaming i know), wont there only be a total of 25amps being drawn from each battery only requiring a very small gauge of wiring between the batteries relative to the size of wire going from the bank to the load?

Yes. Under ideal circumstances.

And if so, say for example we take and up the 150amp current draw to 300 amps. Could you then run a second set of cables (in parallel to the first set of cables) on the +/- posts of the same gauge,same size as the first set of wires to handle the additional load?

Yes. Under ideal circumstances. Since often things that are not ideal happen (motor starting surges, reductions in temperature, cable failures, bad batteries etc) cables are typically sized larger than you need them to be in a perfectly balanced system that always sees a certain nominal load. Going bigger on wire gauge is one of the simpler things you can do to increase overall reliability and performance of a low voltage DC power system.

[woogerboy21]

If you look closely at the information on the smartguage site, you will see some examples of the different current flows for different wiring methods. The simplest is when you use a very large bus bar to connect the load and individual wires from the bus bar to each battery. In that case you are right that the individual battery wires only need to be large enough for their proportional share of the load...As long as the resistances of the bus to battery wires and their interconnections are extremely closely matched. You would be better off to assume that each battery wire might have to carry 1/3 of the total current at some point instead of just 1/6.
If you use the multiple level interconnect wiring shown at smartguage (which will only work for 2, 4, 8, 16 etc. batteries, not for 6) then you can determine the differing amounts of current at each level by looking at how many batteries connect to the loads through the same piece of wire.
The simple diagonal method with 6 batteries would have fairly uneven current flow between the end and center batteries and the different interconnect wire pieces.

I can see were when using multiple level interconnection wiring method you could not use 6 batteries. But using this type of wiring method, using the smallest amount of gauge required, wouldn't you need larger and larger gauges as each level progressed to the load on the bank? (Basically between 2 batteries you may be only pulling 25 amps, but when those two are ran in parallel with another 2 you have a 50amp total current draw for that level?)

It boils down to one simple Law of Physics Ohm's Law and Resistance. The current in in parallel path is dictated by the Resistance and Resistance only.

So then yes, assuming all things are equal (knowing though getting things equal is most likely not possible), you can make up for the extra current draw by simply adding additional channels of wiring to the bank rather than upgrading the entire wiring set. No?

[inetdog]

So I have been reading some of the items posted from links in this article (such as http://www.smartgauge.co.uk/batt_con.html) and noticed in there example they state some of the observed current draw being in the range of ~25amp between the batteries (different based on wiring configurations). I wouldn't consider myself an expert by far but from all the research I have done, many have always recommended that if you can use the largest possible wiring available between the batteries in the bank (even up to sizes such as 2/0 and even as large as 4/0) to handle sudden and large draws of current.

The question I have is, when wiring a battery bank up, will the current flow attempt to naturally even the current load out across wiring in the bank between batteries? What I mean by this is, say for example I have a battery bank consisting of 6 total 12v batteries run in parallel (throw all the discussion of going higher voltage aside for the time being). If I have a 150amp current draw on the bank itself and its in an ideal wiring configuration allowing for even current draw between the batteries (im dreaming i know), wont there only be a total of 25amps being drawn from each battery only requiring a very small gauge of wiring between the batteries relative to the size of wire going from the bank to the load? And if so, say for example we take and up the 150amp current draw to 300 amps. Could you then run a second set of cables (in parallel to the first set of cables) on the +/- posts of the same gauge,same size as the first set of wires to handle the additional load?

I understand that its simpler to just buy a gauge of wire that will handle the current load required, I am just trying to understand how the current in a bank works when wired in different fashions.

If you look closely at the information on the smartguage site, you will see some examples of the different current flows for different wiring methods. The simplest is when you use a very large bus bar to connect the load and individual wires from the bus bar to each battery. In that case you are right that the individual battery wires only need to be large enough for their proportional share of the load...As long as the resistances of the bus to battery wires and their interconnections are extremely closely matched. You would be better off to assume that each battery wire might have to carry 1/3 of the total current at some point instead of just 1/6.
If you use the multiple level interconnect wiring shown at smartguage (which will only work for 2, 4, 8, 16 etc. batteries, not for 6) then you can determine the differing amounts of current at each level by looking at how many batteries connect to the loads through the same piece of wire.
The simple diagonal method with 6 batteries would have fairly uneven current flow between the end and center batteries and the different interconnect wire pieces.

[Sunking]

I am just trying to understand how the current in a bank works when wired in different fashions.

It boils down to one simple Law of Physics Ohm's Law and Resistance. The current in in parallel path is dictated by the Resistance and Resistance only.

[woogerboy21]

So why such large gauge wiring in battery bank?

So I have been reading some of the items posted from links in this article (such as http://www.smartgauge.co.uk/batt_con.html) and noticed in there example they state some of the observed current draw being in the range of ~25amp between the batteries (different based on wiring configurations). I wouldn't consider myself an expert by far but from all the research I have done, many have always recommended that if you can use the largest possible wiring available between the batteries in the bank (even up to sizes such as 2/0 and even as large as 4/0) to handle sudden and large draws of current.

The question I have is, when wiring a battery bank up, will the current flow attempt to naturally even the current load out across wiring in the bank between batteries? What I mean by this is, say for example I have a battery bank consisting of 6 total 12v batteries run in parallel (throw all the discussion of going higher voltage aside for the time being). If I have a 150amp current draw on the bank itself and its in an ideal wiring configuration allowing for even current draw between the batteries (im dreaming i know), wont there only be a total of 25amps being drawn from each battery only requiring a very small gauge of wiring between the batteries relative to the size of wire going from the bank to the load? And if so, say for example we take and up the 150amp current draw to 300 amps. Could you then run a second set of cables (in parallel to the first set of cables) on the +/- posts of the same gauge,same size as the first set of wires to handle the additional load?

I understand that its simpler to just buy a gauge of wire that will handle the current load required, I am just trying to understand how the current in a bank works when wired in different fashions.

[Sunking]

Sunking, since I am powering a 12V lighting system with these batteries, do I have an alternative to my parallel battery connection?

Yes but it is too late now to ask. Like most folks you get in a 12 volt box. For 12 volt batteries requires 6 cells, and capacity is directly linked to wight and size. So when you get stuck in a 12 volt box the largest capacity you can find is around 50 to 300 Amp Hours. Now there are some 12 volt batteries that are much larger like those made for railroads but not suitable for renewable energy application.

Once you get out of the 12 volt box you soon realize they make 2, 4, 6, and 8 volt batteries up to 4000 Amp Hours. For example let's say you need 12 volts @ 1200 Amp Hours. You would look for 2 volt 1200 amp hour cells like the Rolls S-1590 battery. You would buy 6 of them and wire in series to get 12 volts.

Here is the link to one of the best batteries you can buy for RE application. Take a look and see what is out there. They have two series. The 4000 and 5000 series. The 4000 series is a 7 year battery, the 5000 is a 10 year battery. Scroll down to the botton and look at the graph of cycle life vs discharge depth.

FWIW I hope you did not get Trojan T-105 batteries.

[aerodyn]

Even if you cross wire as the article says, you are still going to have unequal currents. You cannot control the resistances to any degree of accuracy. It changes second by second. If you cross wire like the article states it will help, but not solve the problem. When you place batteries in parallel you sacrifice cycle life.

Sunking, since I am powering a 12V lighting system with these batteries, do I have an alternative to my parallel battery connection? I am just a novice, so I think that connecting them in series would produce a higher voltage than 12V. Would I then have to have some piece of equipment between the battery bank and the light system to step down the voltage?

[Sunking]

Sunking, thanks for the response. I wasn't trying to calculate anything, I was just concerned that the method I used to connect my batteries was not optimal. The article that Inetdog referred me to explained what I was asking. I had simply placed my clamp voltmeter around each battery connection and was surprised at how much difference the amperage was.

Even if you cross wire as the article says, you are still going to have unequal currents. You cannot control the resistances to any degree of accuracy. It changes second by second. If you cross wire like the article states it will help, but not solve the problem. When you place batteries in parallel you sacrifice cycle life.

[inetdog]

Inetdog, thanks much, that article is exactly what I needed to know.

You are welcome. Just keep in mind what Sunking said, namely that all of the neat computer solutions and equations in the world will not match the real world if the batteries are not 100% identical. Not just same make and model but same age and maintenance status.
This is one reason that high voltage series strings of batteries are used for systems that do not make direct use of the low voltage DC.

[aerodyn]

When batteries are in parallel there is no way to calculate how much current is flowing in any one string which is why you should not connect batteries in parallel. The current depends completely on internal battery resistance and connection/cable resistances all of which are dynamic and constantly changing.

Sunking, thanks for the response. I wasn't trying to calculate anything, I was just concerned that the method I used to connect my batteries was not optimal. The article that Inetdog referred me to explained what I was asking. I had simply placed my clamp voltmeter around each battery connection and was surprised at how much difference the amperage was.