Batteries
- Freddy
- Member
- Posts: 7301
- Joined: Fri. Apr. 11, 2008 2:54 pm
- Location: Orrington, Maine
- Stoker Coal Boiler: Axeman Anderson 130 (pea)
- Coal Size/Type: Pea size, Superior, deep mined
I learned something a few weeks back that I thought I'd share. I read this on a sire having to do with solar power and battery back up. I know some of us have two 12V batteries connected to an inverter as backup for our coal stoves. This is one of those "I never thought about it" things. We couple two batteries in parallel to keep the voltage 12 volts and get twice the run time. I have done this with other things in my life and probably have always done it wrong! Check out my diagram. You would think it wouldn't make a scrit of difference, but the fact is (and I proved it two weeks ago while on vacation), hooking them as in the "wrong", the lower battery gives about 60% power and the upper one gives about 40% . Hooked as in the "right" diagram, each gives 50%.
In real life I tried it both ways on my home made electric kayak. When the batteries were ready for recharge, the wrong way the lower was 11.0 volts, the upper was 12.1. Hooked the right was, they both were exactly the same at discharge. 11.9 volts once, and 11.7 the next time.
If doing more than 2 batteries, it get's complicated to do it right. Either find out, or email me if need be.
In real life I tried it both ways on my home made electric kayak. When the batteries were ready for recharge, the wrong way the lower was 11.0 volts, the upper was 12.1. Hooked the right was, they both were exactly the same at discharge. 11.9 volts once, and 11.7 the next time.
If doing more than 2 batteries, it get's complicated to do it right. Either find out, or email me if need be.
Attachments
- SMITTY
- Member
- Posts: 12525
- Joined: Sun. Dec. 11, 2005 12:43 pm
- Location: West-Central Mass
- Stoker Coal Boiler: EFM 520 Highboy
- Coal Size/Type: Rice / Blaschak anthracite
- Other Heating: Oil fired Burnham boiler
Good idea - that way your using both batteries together for more amperage - instead of the battery closest to the load doing most of the work with the second battery picking up the slack.
Makes sense to me.
Would also be better for charging multiple batteries that way too.
Makes sense to me.
Would also be better for charging multiple batteries that way too.
- Yanche
- Member
- Posts: 3026
- Joined: Fri. Dec. 23, 2005 12:45 pm
- Location: Sykesville, Maryland
- Stoker Coal Boiler: Alternate Heating Systems S-130
- Coal Size/Type: Anthracite Pea
Freddy's "right" diagram is only right if the cables paralleling the two batteries are identical gauges and lengths. If not, wiring it correctly is more complicated and beyond what is reasonable to do.
Could you please explain that a bit more?Yanche wrote:Freddy's "right" diagram is only right if the cables paralleling the two batteries are identical gauges and lengths. If not, wiring it correctly is more complicated and beyond what is reasonable to do.
hey fred just like a reverse return on a hw system
Just curious, wouldn't the only difference between the two ways of hooking up the batteries be the resistance of the cable between the two negative leads?
In other words, isn't it only the additional resistance of that short length of cable that would make a difference in the amount of current returning to the batteries?What don't I understand here?
In other words, isn't it only the additional resistance of that short length of cable that would make a difference in the amount of current returning to the batteries?What don't I understand here?
- mozz
- Member
- Posts: 1362
- Joined: Mon. Sep. 17, 2007 5:27 pm
- Location: Wayne county PA.
- Stoker Coal Boiler: Axeman Anderson 1982 AA-130 Steam
They are both correct. If you are measuring any difference between the 2 ways, your wires are not big enough or you have corrosion. Copper does not have enough resistance that the homeowner can measure, if he can then the wire if pretty long and too small a gauge. Measure the voltage under load and see what you come up with. I have to do "bonding" resistance measurements at work with a milliohm meter less than 10 milliohms.
- rockwood
- Member
- Posts: 1381
- Joined: Sun. Sep. 21, 2008 7:37 pm
- Location: Utah
- Hot Air Coal Stoker Furnace: Stokermatic
- Hand Fed Coal Stove: Rockwood Stoveworks Circulator
- Baseburners & Antiques: Malleable/Monarch Range
- Coal Size/Type: Lump and stoker + Blaschak-stove size
Correct.mozz wrote:They are both correct. If you are measuring any difference between the 2 ways, your wires are not big enough or you have corrosion. Copper does not have enough resistance that the homeowner can measure, if he can then the wire if pretty long and too small a gauge. Measure the voltage under load and see what you come up with. I have to do "bonding" resistance measurements at work with a milliohm meter less than 10 milliohms.
If conductors are the correct size it wouldn't matter where the load connects to the parallel connected batteries. Same would be true for the load (resistances) connected in parallel.
- Freddy
- Member
- Posts: 7301
- Joined: Fri. Apr. 11, 2008 2:54 pm
- Location: Orrington, Maine
- Stoker Coal Boiler: Axeman Anderson 130 (pea)
- Coal Size/Type: Pea size, Superior, deep mined
[/quote]
I think Yanche hit the nail on the head. It has to do with the length of the wires and how many connections each path takes. Every nut/bolt connection and it's mating surfaces makes resistance. I also think it has something to do with how wet cell batteries deliver power. It's not like power coming from a socket. I just know in my Kayak I am using 6 gauge copper where 8 ga is recommended. My wires do not get warm during use (except right next to my solenoid) . Hooking them "wrong" I get 45 minutes of use and the voltage of each battery after discharge is dramatically different. Connected "right" I get an hour of use and they discharge equally.
Yup, that's what I always thought....until I tried it after reading about it. I'll see if I can find the original info & post a link to it.mozz wrote:They are both correct.
Yanche wrote:Freddy's "right" diagram is only right if the cables paralleling the two batteries are identical gauges and lengths.
I think Yanche hit the nail on the head. It has to do with the length of the wires and how many connections each path takes. Every nut/bolt connection and it's mating surfaces makes resistance. I also think it has something to do with how wet cell batteries deliver power. It's not like power coming from a socket. I just know in my Kayak I am using 6 gauge copper where 8 ga is recommended. My wires do not get warm during use (except right next to my solenoid) . Hooking them "wrong" I get 45 minutes of use and the voltage of each battery after discharge is dramatically different. Connected "right" I get an hour of use and they discharge equally.
- Freddy
- Member
- Posts: 7301
- Joined: Fri. Apr. 11, 2008 2:54 pm
- Location: Orrington, Maine
- Stoker Coal Boiler: Axeman Anderson 130 (pea)
- Coal Size/Type: Pea size, Superior, deep mined
Heyyy! I found the original info ..... give it a read if you're interested.
http://www.smartgauge.co.uk/batt_con.html
http://www.smartgauge.co.uk/batt_con.html
- Yanche
- Member
- Posts: 3026
- Joined: Fri. Dec. 23, 2005 12:45 pm
- Location: Sykesville, Maryland
- Stoker Coal Boiler: Alternate Heating Systems S-130
- Coal Size/Type: Anthracite Pea
The link provided by Freddy explains it well. Method 4 is the simplest to extend to any number of batteries. If you don't understand it try replacing each short segment with a resistor in your mind. Now if you are loading the battery bank and you want to draw equal current from each battery, i.e. all the voltage drops across each resistor must be identical therefore the resistors must also be identical. Without a milliohm meter there is no practical way to measure the value of the resistances. Therefore you just make the conductors identical.Freddy wrote:Heyyy! I found the original info ..... give it a read if you're interested.
http://www.smartgauge.co.uk/batt_con.html
Decades ago I designed an spark ignition system for a hypersonic wind tunnel system. It used Navy surplus submarine batteries in parallel and series combinations. 100's of them. Battery current draw balance was critical. I don't remember the final voltage but it was thousands of volts. The test tunnel generated mach 5+ air velocity and thousands of degrees F. The heat came from the arc from the battery bank. The bank was housed in a 5000 sq. ft. warehouse. Air was compressed air stored in hugh surplus Navy gun barrels. They pumped for about a week to get the desired pressure and then released it all in 30-60 seconds at the same time the arc was heating the air. The noise was really, really impressive. Scaled models of guided missiles were what was being tested. The entire wind tunnel facility is long gone. Replace by computer simulations. Much safer, more accurate and cheaper.
- rockwood
- Member
- Posts: 1381
- Joined: Sun. Sep. 21, 2008 7:37 pm
- Location: Utah
- Hot Air Coal Stoker Furnace: Stokermatic
- Hand Fed Coal Stove: Rockwood Stoveworks Circulator
- Baseburners & Antiques: Malleable/Monarch Range
- Coal Size/Type: Lump and stoker + Blaschak-stove size
You've got me intrigued on this one. Tomorrow I will gather some information (hopefully with photos) and get back to you guys.....I have some perfect examples of large battery strings that I have access to and I will see how they're connected. I also know some knowledgeable people in this particular field that I will ask about this as well. Maybe I can teach them something for a change
- rockwood
- Member
- Posts: 1381
- Joined: Sun. Sep. 21, 2008 7:37 pm
- Location: Utah
- Hot Air Coal Stoker Furnace: Stokermatic
- Hand Fed Coal Stove: Rockwood Stoveworks Circulator
- Baseburners & Antiques: Malleable/Monarch Range
- Coal Size/Type: Lump and stoker + Blaschak-stove size
Well, these battery strings are connected in series and series/parallel so it's not the example I thought it would be.
This doesn't prove or disprove the "right/wrong" way to connect batteries but thought everyone would want to see these photos anyway.
This doesn't prove or disprove the "right/wrong" way to connect batteries but thought everyone would want to see these photos anyway.
- Freddy
- Member
- Posts: 7301
- Joined: Fri. Apr. 11, 2008 2:54 pm
- Location: Orrington, Maine
- Stoker Coal Boiler: Axeman Anderson 130 (pea)
- Coal Size/Type: Pea size, Superior, deep mined
WHOA! There's some nice batteries! What are they for?
The diagram shows 10 sets of 48 volts making 480. If they are all 12V batteries, the 10 sets must be four batteries in parallel (or 8, 6V). Those are the ones we'd be interested in seeing how they linked up.
I'd love to have seen the monster system that Yanche worked on. Can you imagine?
The diagram shows 10 sets of 48 volts making 480. If they are all 12V batteries, the 10 sets must be four batteries in parallel (or 8, 6V). Those are the ones we'd be interested in seeing how they linked up.
I'd love to have seen the monster system that Yanche worked on. Can you imagine?