### Author Topic: battery bank charging  (Read 23517 times)

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#### hnash53

• Guest
##### battery bank charging
« on: January 17, 2007, 03:15:25 PM »
I have purchased sixteen 12-volt deep cycle batteries, each with 134 amp-hours @ 20 hr rate.  I plan to wire two sets of 8 batteries each in parallel to increase my amp-hour capacity, and then to wire these sets together in series to increase the voltage to 24 volts.

My question:  Can I still charge this bank of batteries with my 12-volt windturbine, my 12-volt solar panels, and my 12-volt battery charger?

Hal Nash
Wyoming

#### MountainDon

• Guest
##### Re: battery bank charging
« Reply #1 on: January 17, 2007, 08:02:09 PM »
Quote
I plan to wire two sets of 8 batteries each in parallel to increase my amp-hour capacity, and then to wire these sets together in series to increase the voltage to 24 volts.  Can I still charge this bank of batteries with my 12-volt windturbine, my 12-volt solar panels, and my 12-volt battery charger?

#### MountainDon

• Guest
##### Re: battery bank charging
« Reply #2 on: January 17, 2007, 08:46:43 PM »
Quote
Quote
I plan to wire two sets of 8 batteries each in parallel to increase my amp-hour capacity, and then to wire these sets together in series to increase the voltage to 24 volts.  Can I still charge this bank of batteries with my 12-volt windturbine, my 12-volt solar panels, and my 12-volt battery charger?

First it doesn't matter one iota where the charging power is coming from as far as the battery/batteries is/are concerned. In charging a nominal 12 VDC battery the voltage during different charging phases can run as high as 15 volts, typically from 13.6 to 14.2 or so. So a 24 VDC battery system would require from about 27.2 volts up to 30 volts. So trying to charge a 24 VDC system with 12 volts will not work.

However, your 12 VDC (nominal) solar panels can be connected in series instead of parallel to provide higher voltages (2 = 24, 3 = 36, etc.) You didn't state how your panels are wired, but I assume they are in parallel because you called them 12 volt. However (there's always a catch), if you run them in series or series and parallel to provide the 24 VDC output you may need a new charge controller. Some controllers are adjustable or prongramable. Some are not.

Using the battery charger faces the same problem, good for charging a 12 volt battery but not 24 volts.

As for the wind turbine I'm not very familiar wind wind generators, I do know their regulation system differs from that used in solar systems. However, unless the manufacturer has allowed for converting the output from 12 to 24 volts by rewiring something in the unit, you face the same problems as above.

Not to belabor the problems you face, there's another point, which may be moot since you already have the sixteen 12 volt batteries. Some alternative energy "experts" are of the opinion that layering more than three parallel sets of battery strings is not advisable. Some don't even advise going or two layers, and others don't seem to have an opinion. I think those guys (without a strong opinion) just want to sell batteries and don't really care what happenes a few years down the road.

For what it's worth, and this is just my opinion, formed after using a multitude of batteries, different types, voltages, etc. over more than  30 years in RV applications, I would not go over two parallel layers. Just my opinion.

Here's a link explaining the potential problem...    http://www.thesolar.biz/Keeping_batteries_alive.htm

I have experienced the "lazy string" problem in large RV battery banks. (my RV's have always had more batteries than most as I tend to like to really get away from it all in a big way, for days at a time, and are loath to run my genset, yet I love my conveniences, microwave, furnace, etc. Kinda schizo, but that's me. See there I go off topic again....   )

To those recommendations on that link, I would add another thing or two to do to help achieve maximum battery life.
1. use highest quality cabling using mechanically crimped connectors. A properly made mechancial (crimped by machine or proper crimping tool) is superior to a soldered connection because (A.) solder has higher resistance than copper wire and (B.) high temperatures required to solder large cables invariably burns the insulation on the cables. Use the largest diameter cable, like 4/0

2. Instead of connecting the parallel strings with more 4/0 cable connect each parallel string to a solid copper bus bar of sufficient ampacity. A good copper bus bar will have way lower resistance than the series connecting string of cables. This will help eliminate that potential problem area. A good source for copper connecting products is Storm Copper    http://www.stormcopper.com/    They have all sorts of copper connection products and the bus bar material can be obtained blank for a drill it yourself approach to save a little money.

« Last Edit: January 17, 2007, 08:56:15 PM by MountainDon »

#### glenn-k

• Guest
##### Re: battery bank charging
« Reply #3 on: January 17, 2007, 11:49:41 PM »
I don't know how much power you are going for, Hal, but there are some decent 12 volt to 110 inverters out there.  You could just run it all 12 volt using the buss like Mountain Don mentioned.

It requires heavy cable on the low voltage side as Mountain Don mentioned.

There may be some step up regulators now too.

Low voltage is not very efficient so cable sizes get large and expensive.

You can charge the groups of 12v separate, but its a real hassle keeping things even close to balanced and batteries will give you a lot of trouble.  I played that game when I first started.
« Last Edit: January 17, 2007, 11:52:36 PM by glenn-k »

#### hnash53

• Guest
##### Re: battery bank charging
« Reply #4 on: January 18, 2007, 06:55:33 AM »
Glenn and MountainDon,

Thanks for your input.  I'm new to this game, and it seems that everyone has their own rules of the game that they play by.  I've gotten different answers from different sources.

Maybe it would be easier to string all 16 batteries in parallel @ 12volts and a shit-load of amp-hours.  Then all my charging sources would be fine...solar, wind, dc generator.

Glenn, you said you started out with batteries but sounds like it became a headache.  What are you getting at?  In a totally offgrid location, what other solutions are there?

Thanks, guys...appreciate the info.  Don...schizo is OK.  Everyone is schizo...just some of us are honest enough to admit it!!

#### glenn-k

• Guest
##### Re: battery bank charging
« Reply #5 on: January 18, 2007, 08:14:21 AM »
I didn't make that real clear did I.  I started out with a group of mixed batteries - car batteries -deep cycle- some charged too much - some not enough -  I'd try to charge the low ones by them selves to even them out with the rest, but some of them may have had other problems anyway.  I was constantly fooling with them.

I finally went to 12 L16's - 6v 375 ah and series'd 4 then paralleled the 3 groups for my 24v system.

I think you are right in your case - you have the stuff for a 12 v system - use it.  I have no question that the bus bar Mountain Don is talking about is the best way to go.  I'm not doing that but have always thought it would be easier than the cables and jumpers and stuff I'm using.

You will find that terminal ends are expensive if making your own cables.  I buy heavy entrance cable then smash copper tubing of the appropriate size over it then drill a hole through it to bolt it.

You could get the buss bars then run all the batteries to the buss bars as probably the best way of doing it.  Paralleling 2,4,8 etc. then paralleling them on the bus has a bit more risk of losing a battery here and there through connections and if they all go to the bus it is easier to work on a problem one than to pull one out of a group to clean terminals etc.  Smaller cables can be used to the buss - if you stack a bunch then cables have to vary or use oversize throughout - things get more complicated.  24v systems can use smaller cables than 12 but you need to work with what you have.  I also started out 12v but switched to 24v when I got my 24v wind generator.

All in all, they still require checking every so often for problems.
« Last Edit: January 18, 2007, 08:19:05 AM by glenn-k »

#### MountainDon

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##### Re: battery bank charging
« Reply #6 on: January 18, 2007, 12:07:58 PM »
Quote

You will find that terminal ends are expensive if making your own cables.  I buy heavy entrance cable then smash copper tubing of the appropriate size over it then drill a hole through it to bolt it.
I must admit to having a couple connector ends like those Glenn. I went the slightly more elegant route and squished the bejeebers outa the copper tubing with a 20 ton hydraulic press.     They might not meet NEC code, whaddaya think?   :-/  Not too worried about that myself, but it's something one should keep in mind if one is trying to jump thru all the hoops.

Here's a link of interest for some of the more reasonably priced UL listed connectors I've found.    http://www.solarseller.com/quick_cable_copper_cable_lugs.htm    that's direct to their copper lug connector page. Lots of other interesting stuff as well.

I also use a red spray coating on the connections, it seals the connections so they don't corrode as easily. Marketed with the Exide name on the can I have. Smells like lacquer.

#### glenn-k

• Guest
##### Re: battery bank charging
« Reply #7 on: January 18, 2007, 12:23:27 PM »
In the sprays, they have a cleaner also but baking soda and water does quite well on most of it.  I use the Red spray too when I've done an especially nice job and want to reward myself by making it look pretty.

I usually smash the copper tubing with a hammer - I squish it together pretty tightly.  For special effects I sometimes use the ball peen end.
« Last Edit: January 18, 2007, 02:29:45 PM by glenn-k »

#### MountainDon

• Guest
##### Re: battery bank charging
« Reply #8 on: January 18, 2007, 05:44:17 PM »
Quote
I don't know how much power you are going for, Hal, but there are some decent 12 volt to 110 inverters out there.

There are many good brands, one that I like (I have one of their units in the RV) is Exeltech     www.exeltech.com    Their MX series is expandable in 1000 watt increments up to darn near anything. That is as long as your battery cables are up to the power demands. Not cheap but then none of the good pure sine wave units are. Unless they're Chinese and in my view a lot of them are suspect.

One source for them is   http://www.nwpwr.com/products/inverters/mx_series.htm
« Last Edit: January 18, 2007, 05:45:14 PM by MountainDon »

#### hnash53

• Guest
##### line losses through long cables from wind turbines
« Reply #9 on: January 19, 2007, 03:43:56 PM »
[size=14]You guys seem to know a bit about all this Alt Energy stuff.

Give me some good news, eh?

Thanks.

Hal[/size]

#### MountainDon

• Guest
##### Re: line losses through long cables from wind turb
« Reply #10 on: January 19, 2007, 04:19:09 PM »
Ok. You can sort this all out yourself; go here
http://www.countryplans.com/cgi-bin/yabb2/YaBB.pl?num=1168907350

There you will find several different links to voltage drop calculators. All except the last one are web based utilities. They vary a little in how they are used but basically you fill in the blanks and it gives an answer.  The variables involved include:
1.  system voltage
2.  maximum amperage through the conductor
3.  length of cable (some use a one way distance (ie from turbine to where the controller / batteries are), and some use the two way distance (ie 80 yards from turbine to batteries = two way distance of 160 yards))
4. size or gauge of cable (AWG = american wire gauge)
5. voltage drop or loss expressed as a percentage or as a finite number.
6. some of the calculators also allow for a choice between copper or aluminum cable. copper is best for havimg lower resistance, aluminum may be cheaper even if you have to use a larger size cable. Check the \$\$. Also I believe if you bury the cable you must use copper... even if in a conduit in the ground, conduit is considered wet and moisture results in a corrosion problem with aluminum)

You would want to keep the voltage drop to a maximum of 2% if at all possible; 3% is not too bad. Just a sec...  :-/that's correct when we're talking about power from solar (photovoltaic) panels. They are not too efficient to begin with so we want to keep as much power as possible. For a wind turbine system in a well producing area I imagine you could go to 5% or so loss. Like I said, I'm not well versed in the wind power area. ....if I could harness my farts, tha'd be a really powerful energy source....

I'm not sure how well versed you are in electrical "nuts and bolts", so I'll mention a few things. There is resistance to current flow in any wire/cable. The thicker the cable the less resistance. If you raise the voltage for a given number of watts the amps decrease... 12 VDC at 10 amps = 120 watts    AND  24 VDC at 5 amps = 120 watts (amp-hours) So for a given length of cable you would need a larger cable size to push the 120 watts at 12 VDC as compared to 24 VDC. Wire/cable size is measured in AWG, and the [highlight]smaller the number, the larger the cable[/highlight]. When you get down to 1 AWG the numbering changes and you go to  1/0 awg, then 2/0, 3/0, 4/0 etc.

So if your turbine is 80 yards from the batteries, that's 80x3 = 240 feet. You have 12 VDC. What is the max amperage output of the turbine? Let's use 10 amps as an example. What's the size of your cable? Let's use #4 AWG for an example.

Using the calculator at   http://www.nooutage.com/vdrop.htm    let's see the results...   Uh-oh that comes out with a 12.4% drop. Too much wasted energy.  If we go up one wire gauge size to #2 AWG.... then it's a drop of 8%, still high.  You can play around with different wire gauges, amps, volts and distances to see how it all relates.   This voltage drop thing is one reason I previously mentioned wiring the solar panels in series  play with the calculators and if you have further questions, I'll try to answer them.

I hope I helped lift the fog a little. G/L

« Last Edit: January 19, 2007, 09:16:31 PM by MountainDon »

#### glenn-k

• Guest
##### Re: battery bank charging
« Reply #11 on: January 19, 2007, 04:31:05 PM »
What he said.

Low voltage  losses are heavy in small cable.

Do you know the model of your wind generator or maximum output?  We could tell you more from there if we know that.

As Mountain Don said, if you lose it all in your cable, it does nothing to charge your battery.  It helps to think of it like water.  A short small hose will put out quite a bit of water, but as it gets longer and longer you come to a point where water will no longer flow.  Your batteries are your bucket.  If the hose is long it must be large to still carry the same amount of water as the small short one and be able to fill the bucket.
« Last Edit: January 19, 2007, 04:38:34 PM by glenn-k »

#### MountainDon

• Guest
##### Re: battery bank charging
« Reply #12 on: January 19, 2007, 04:38:06 PM »
Quote
Do you know the model of your wind generator or maximum output?  We could tell you more from there if we know that.
I'd be happy to run the numbers for you.   I assume the wind turbine is already in place and you have used it with a smaller, older battery?? If so do you know the cable size you have as well?

And ya'll can call me Don, instead of the longer MountainDon.... I don't own much of that mountain anyways
« Last Edit: January 19, 2007, 04:41:51 PM by MountainDon »

#### hnash53

• Guest
##### Wind generator specs
« Reply #13 on: January 20, 2007, 11:18:31 AM »
I am building a "home brewed" wind generator as shown at the following link:

http://www.lookout2000.com/windpower/

It is using a 12V car alternator with pulley system to generate 60amps for a total (theoretical) of 720 watts.

This is the unit I am describing in all of my questions to you.

I'll check out the links to try and understand line losses.

Thanks, Don and Glenn.

#### MountainDon

• Guest
##### Re: Wind generator specs
« Reply #14 on: January 20, 2007, 12:08:01 PM »
Quote
I am building a "home brewed"
Hal, I am a big fan of home brewed stuff myself. I have 4 gallons that'll be ready in a few days....   Ooops, that's the other forum       I'll post some numbers for you later today some time

#### benevolance

• Guest
##### Re: battery bank charging
« Reply #15 on: January 20, 2007, 01:32:24 PM »
I just wonder why not try to utilize the high amp altenators that are 90 amps instead of merely 60....

I junked out a firetruck one time and it had a 200 amp altenator on it....Wouldn't this be a better base to build the wind generator on?

#### MountainDon

• Guest
##### Re: battery bank charging
« Reply #16 on: January 20, 2007, 01:48:35 PM »
Okay here goes my 2 cents worth.  The CHART below has amps and watts at 12 VDC in the left hand column, wire size (AWG) across the top. The values inside the chart represent the calculated voltage drop in percent. The chart is assuming a transmission distance of 240 feet one way direction.

I've included the AWG 10 column only for comparison purposes, that is the largest size wire you normally would find in the house wiring AC circuits, like for a range or dryer, NOT an incoming supply line.  All your other house AC circuits would be either 12 or 14 gauge, even smaller size wire.

How often the generator will get up into the upper ranges is something I don't know. But you can see that even with the 4/0 cable, that's about the largest cable you'll find, the losses get kind of high. That percentage number is how much of the produced energy is going to waste heating your cables. Sizing the cable down around to #4 or #2 cables sizes has a tremendous amount of  power going to waste. Those larger cables, 2/0 and 4/0 get to be rather pricey when you're looking at two 240 foot lengths, one positive and one negative. I had a quick look at a local supplier of battery cable in bulk; 500 feet of 4/0 is \$2873.00 and 500 feet of 2/0 is \$1053

More to come.....

« Last Edit: January 20, 2007, 02:40:38 PM by MountainDon »

#### MountainDon

• Guest
##### Re: battery bank charging
« Reply #17 on: January 20, 2007, 02:06:39 PM »
More...

Note that was for battery cable and does not meet NEC code. I couldn't check for NEC approved 4/0 and 2/0 cable but they're probably more money.

ALL may NOT be lost though. [highlight] ANOTHER IDEA:[/highlight] If you are going to attempt to build a wind generator yourself using that one in the link as a guide why not subsitute a 24 VDC alternator from some vehicle or machine with a 24 VDC electrical system? I have an old Toyota Land Cruiser (Canadian issue) diesel with a 24 VDC electrical system, including alternator and stater. Yes, that would be more expensive than the GM style alternator shown in those plans.  The GM are as common as mouse turds and cheaper as a result. At 24 VDC you would have one-half the amps for the same watts. [12 VDC @ 40 amps = 480 watts. At 24 VDC the 480 watts is achieved with a current of only 20 amps] That will cut the required conductor size down by about 2 wire sizes. Run one of those calculators to see. Here's one example tho'...
12 VDC suppling 480 watts for 240 feet over 4/0 cable gives a 12.8% drop in voltage, but changing to 24 VDC equals a drop of only 6.4%.... double the voltage = half the voltage drop.... OR with 24 VDC, 480 watts, 240 feet and smaller (cheaper) 1/0 cable a drop of 10.4%.   That's a little less drop for much cheaper cable.

On the downside, using 24 VDC for the wind gen and the batteries gets you back to the incompatibility between your other 12 VDC charging systems, solar and generator.

« Last Edit: January 20, 2007, 02:43:41 PM by MountainDon »

#### MountainDon

• Guest
##### Re: battery bank charging
« Reply #18 on: January 20, 2007, 02:19:29 PM »
[highlight]YET ANOTHER IDEA![/highlight]  If the batteries were located right there at the wind generator your cabling needs for a 12 VDC system would be minimized. What you would have to do though is install your dc to ac (pure sine wave) Inverter(s) up there as well. Then you'd run 120 VAC (240VAC?) to the cabin. The higher voltage power would require less in cable size and cable cost. Of course as with nearly every upside change there's a downside. The 120 VAC power cables are more dangerous if in the air overhead and they fall.

An off topic aside, but a safety thing..... 12 Volts is generally not as dangerous as 120 Volts as fas as electrocution goes. You still have to be careful with 12 and 24 VDC battery systems but you are less likely to be elctrocuted. The danger point is reached at about 48 VDC. Oh, but of course a mistake can blow up a battery and that is an experience we can all do without.

Back to topic... Another downside to the remote batteries is that batteries don't like the cold anymore than I do. If they were up on that windy ridge and the cabin is NOT, I guess the batteries would be sitting there in an unheated box assuming whatever the ambient air temp is. You can easliy loose half you rated battery capacity from cold.  They don't like too much heat either. Batteries like the same temperature range as people.

I've worn out my two fingers, that's all for now
« Last Edit: January 20, 2007, 02:46:50 PM by MountainDon »

#### MountainDon

• Guest
##### Re: battery bank charging
« Reply #19 on: January 20, 2007, 02:24:33 PM »
Quote
I just wonder why not try to utilize the high amp altenators that are 90 amps instead of merely 60....

I junked out a firetruck one time and it had a 200 amp altenator on it....Wouldn't this be a better base to build the wind generator on?

IF the gen and batteries were closer together, that could be advatageous.

My Jeep and RV have 175 amp and 160 amp alternator/welders respectively supplying the juice, but that's another topic.
http://www.premierpowerwelder.com/specs/ppwspecs.html
Their showers are pretty nifty too
http://www.premierpowerwelder.com/underhood/underhood.html
« Last Edit: January 20, 2007, 02:33:20 PM by MountainDon »

#### hnash53

• Guest
##### Re: battery bank charging
« Reply #20 on: January 20, 2007, 03:40:39 PM »
Below is a quote from http://www.hydrogenappliances.com/powerpmas.html  :

[size=12]"...standard automotive alternators are usually putting out 40 to 50 volts into the 12 volt battery in your car. That's right! It won't harm the battery AS long as the battery is not FULL. It can take high levels of charging voltage no problem. A lead acid battery will easily buffer high input voltages.  It is normal to charge batteries with much more power than their output ratings. Only start worrying when the battery is fully charged and THEN any additional power must stop coming into it or must be dumped to keep the battery cool and from producing explosive hydrogen gas.

To make a long story short a 12 volt battery that is being charged with a wind turbine putting out 50 volts will still only read "12 volts" to a volt meter proving that the high voltage power is easily being swallowed up by the big lead plates of your battery." [/size]

[size=14][/size]So according to this, if I have an alternator that does not have a regulator on it (i.e. an externally regulated one but without an external regulator attached) I can put out more voltage than 12 volts and therefore I could experience some line loss but still have enough valuble wattage arriving at my battery bank.

I could regulate my battery bank with a device seen here:  http://www.hydrogenappliances.com/batteryregulator.html

It dumps any excess charging that arrives at my battery bank to some kind of heat sink, such as a 12 volt water heater inside the cabin.

Benevolence, your comment sort of goes along with what I am proposing above.  Your thoughts welcome.

Thanks, all.

A battery is basically a BIG capacitor in electronic terms. Once your batteries are fully charged you must THEN stop putting any additional power into it!

#### MountainDon

• Guest
##### Re: battery bank charging
« Reply #21 on: January 20, 2007, 04:01:16 PM »
Quote
I could regulate my battery bank with a device seen here:  http://www.hydrogenappliances.com/batteryregulator.html
It dumps any excess charging that arrives at my battery bank to some kind of heat sink, such as a 12 volt water heater inside the cabin.

Right. Wind and hyro power systems use that sort of diversion device for the power not needed to charge the batteries. Cab be used to heat water or air.

#### MountainDon

• Guest
##### Re: battery bank charging
« Reply #22 on: January 20, 2007, 04:01:39 PM »
Quote
if I have an alternator that does not have a regulator on it (i.e. an externally regulated one but without an external regulator attached) I can put out more voltage than 12 volts and therefore I could experience some line loss but still have enough valuble wattage arriving at my battery bank.
No argument there, but I believe that if you move the regulator down to where the batteries are there are then 4 wires involved between the alt and the reg. Not sure if they all have to be whatever max size is indicated by the max current flow.  :-?
« Last Edit: January 20, 2007, 04:26:05 PM by MountainDon »

#### Amanda_931

• Guest
##### Re: battery bank charging
« Reply #23 on: January 20, 2007, 05:23:36 PM »
I gather that the first rule of off grid with batteries is:

[size=16]Everybody screws up their first set of batteries.[/size]

(I only have one in the trailer, and supposed to have an inverter.  But if the I leave it on all the time it will overcharge the battery--might have worked better with two--but that first--"deep cycle boat type" really didn't last very long--and I'm not all the way off grid--part of the problem, actually)

Now, with the inverter broken, I hook up a battery charger every couple of days,, or when my meter says I'm at the 75% level.

Don't know if I've really learned my lesson yet, though.

I've had a little experience driving (and charging) electric forklifts though.

#### MountainDon

• Guest
##### Re: battery bank charging
« Reply #24 on: January 20, 2007, 05:44:17 PM »
Amanda, if that trailer is a standard RV type of trailer and you are using the equipment that came with it, then that is the problem. Most RV's, except for newer and upscale models come with a combination charger / converter that is supposed to keep the battery full from the "shore" power AC you plug in to. Those invariably don't put out enough power to charge a really low battery, nor do they shut off so as to not overcook the battery. More than one battery might slow doen the overcharging, but in the end toasted batteries are the result. I killed a couple batteries when I got my first RV. I now use a separate charger from Iota. It does throttle right down to just enough to keep the batteries at full but not overcooked.

The 75% figure you mentioned... do you mean you recharge when the battery is still 75% full, or that it's 75% empty.  If you aren't letting the battery go below 75% of a full charge that's Great. If you're going down to 75% discharged that's not nearly so good. A 50-50 deal; 50% deal is much better with respect to battery longevity. But I know from experience it's difficult at times to keep the charge above 50% without it seeming like you are always putting the battery on and off charge. That's why I went to four six volt batteries when I toasted my second battery within the first two years. That was a long time ago. Batteries have been better to me since then because I was better to them.

I've never driven a fork lift before, but would think you need one to move one of those giant batteries around. From what I've heard in an AE situation they can easily be completely function after a quarter century of use.

Best thing for any battery, deep cycle or not, is to never go below 50%. And the shallower your discharge the longer the life. Going down to
« Last Edit: January 20, 2007, 05:46:38 PM by MountainDon »

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