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Get Powered Up! Certified Energy Manager Jeff Yago answers your alternative energy questions

Wondering about a great new energy-saving device
you found on the Internet? Then CLICK HERE!

Sorry. Jeff no longer answers questions online.
This will remain as a searchable
resource for all BHM website visitors.



Archive for the ‘6 volt’ Category

 

Charging 6 volt batteries in a series

Monday, June 15th, 2009

Jeff

I have a 36 volt (6 6-volt batteries) Cushman golf cart.

Can I bypass the old charger and use a 6-12 volt battery charger to charge these six 6 volt batteries wired in a series? If so where do I put on the + and – cables? One on the first battery and one on the last battery in the series?

Thank you for your time

Tom
Indianapolis

Tom,

I am not sure why you want to do this but I am going to assume the on-board 36 v charger is dead, and you have this other charger around but it is a 72 volt charger (6 x 12)??.

My first suggestion is call or stop by a used golf cart outlet.  There is usually at least one in all larger cities having several golf courses.  They have tons of these used chargers around and will either give you one or sell you one very cheap since many people are paying to have these old carts re-furbished for use in RV parks and they usually include a new charger with each cart sold.  Be sure to get the right model as many of todays golf carts use six (6) batteries @ 8 volts each which require a 48 volt charger.

If your charger is really a 72 volt charger designed to charge six (6) batteries of 12 volts each, then you cannot use it.  It is possible to use a 12 volt charger and connect to two batteries at a time in series which makes 12 volts.  You would connect to the positive and negative of each set of 2 batteries, then move to the next set of 2 until all 3 sets are charged, or you could use a 6 volt charger (some 12 volt chargers have a 6 volt switch) and charge them one at a time the same way, but do not connect a higher voltage charger to a lower voltage battery set.

Good luck,

Jeff Yago

 

Wiring batteries

Tuesday, April 28th, 2009

Hi Jeff,

I wanted to thank you ahead of time for you assistance.

We are going to have an off grid solar panel system. Is it possible to wire two 6- volt batteries together both parallel and series to get double the voltage and double the amperage? If not, what are your recommendations?

Thank you so much,

Jenelle Sherstad

Jenelle,

You can wire two 6-volt batteries in series to make 12-volts. You can also wire two 6-volt batteries in parallel to double the amp-hours. But if you wire the same two 6-volt batteries both ways, you will get a lovely cloud of smoke from burning plastic insulation, lots of fire, and chunks of burning copper wire flying through the air. This is because you will be making a dead short from the positive to negative terminals on both batteries.

Either use four batteries, with each pair wired in series, and then the 2 pairs wired in parallel, or buy a really good fire extinguisher.

Good luck,

Jeff Yago

 

Wiring 8 6-volt batteries to get 24 volts

Wednesday, February 11th, 2009

Hi Jeff.

I hope you can help me on this.

I need to know how to wire 8 Trojan T-125 6 volt batteries to get 24 volts.

Thank you.

Orlando

Orlando:

First take four (4) batteries and connect the positive of the first to negative of second, and so on down the line.  This requires 3 cables, so you should end up with 4 batteries in a line with an empty positive terminal on one end and an empty negative terminal on the other end.

Now do this all over separately with the other four batteries.

Place these two separate “strings” of batteries side by side.

Now connect the positive terminal of each separate “string” to each other — thats positive to positive.

Now connect the negative terminal at the other end of each “string” to each other –  negative to negative.

Finally, when you connect this battery set to an inverter or other load, be sure to connect at the opposite corners from each other.  This means, if you connect the positive load cable to the positive post of the first row of batteries, you connect the negative to the negative post of the second row of batteries.  This balances the electrical flow so each “string” of batteries will have the same length of path for the electricity to travel, which forces all batteries to receive the same charge and discharge.

Remember to NEVER connect the positive to the negative of the same battery as this is a dead short and will let all of the smoke and fire escape from inside the battery!

Good luck,

Jeff Yago

 

Charging a 6 volt battery with a 12 volt solar panel

Sunday, February 1st, 2009

Hi Jeff,

I recently built a small alt-e project with my daughter.  It’s a shelf with a 6v van and a couple of led lites for over her bed.  It’s powered by a 6v 36 amp-hour battery in an ammo can under her bed.  I have a 4.5w, 300mA Coleman solar panel intended for trickle charging 12v batteries.  It charges at about 17v.

Am I right in thinking that with a system this small and with a current that low that I can use this panel with this battery without frying wire or battery, or should I hold out to find a panel that charges at 8v.

Steve Sonntag MD

Steve:

In an emergency you could temporarily re-charge a 6 volt DC deep discharge battery with a 12 volt solar array, but I would not make this a permanent connection for the following reasons.  This Wal-mart solar charger was designed to trickle-charge a large 12 volt battery, and does not have a built in solar charge controller, which is available as an option from the manufacturer.  Supplying a higher voltage to a wet cell deep discharge battery is typical for periodic equalize charging, but it sounds like you have a sealed deep cycle battery.  If that is the case, over-charging from a high charging voltage will dry out a sealed battery and these cannot be restored.

Also, without a solar charge controller between the battery and the solar module, you have nothing to prevent battery charge from discharging back through the solar module, although this small solar module may contain a blocking diode to protect from this.  You may be able to remove the backing from this solar module and “split” the string into two groups of 6 volts, since many solar modules are made up from separate strings of individual cells like Christmas string lights.  Find the wiring point between two equal sets of cells and cut this wire, then tie the positive side to the positive output wire, and tie the negative side of the cut to the negative output wire.  Now you will have a 6 volt nominal solar module.  Keep in mind that many commercial 12 volt and 24 volt modules have internal junction boxes set up to allow you to do this with these larger units.

If all else fails, buy a 12 volt battery, fan, and light.  They are probably easier to find than 6 volt units anyway.

Good luck,

Jeff Yago

 

Battery voltage drop

Tuesday, December 16th, 2008

I have a solar system (4-100 watt panels, voltage regulator, 6-6volt deep cycle batteries wired in series and parallel ( a battery “pack”), a low power and high power (3000/6000 watt Vector Inverter with soft start technology)).

This system is at my cabin which I use only 10-15 times/year for 4 days at the most per visit.

I use the low power (400 watt inverter) for lights, radio, a small TV and other miscellaneous needs and don’t use much power from the low power inverter. In fact the blower internal to this inverter rarely comes on and I have never had a problem getting enough power out of the battery “pack” to supply my low power needs.

I use the high power inverter for my well pump only which draws high current ( i.e. 60 amps a.c for about 1 second) at start-up and then for 2-3 minutes of a 12 amp a.c. current draw, till the pressure tank is full. I estimate that I start the well pump anywhere from 3-30 times per visit ( over a period that might range from 2-4 days and thus often get a solar charge during this time).

Lately the battery “pack” will support the high current draw at 12 volts (measures above 13 volts at these attempts) without dropping below the 10.5 volt minimum required by the inverter for only 1-2 times to start the well pump. After 1-2 times of starting the well pump the battery pack voltage drops to about 12.4 volts and when I attempt to start the well pump, the voltage drops below the 10.5 volts required by the inverter and the inverter goes into a fault mode. The batteries seem to have enough capacity right after they have experienced a charge cycle from the solar panels and the voltage from the combined 6-6volt battery “pack” above 13 volts.

I suspect the batteries need to be replaced even though the specific gravity of all cells in all of the batteries measures above 1.270. The batteries are about 5.5 years old.

Considering my application, where I don’t use the batteries frequently and probably don’t run them down to less than 60-70 % of full charge, what type of batteries would you recommend? Deep cycle, marine, automobile? 6 or 12 volt? Any other recommendations?

Thanks for any advice you can give me.

Dave Keese

Dave:

I suspect what you have is a battery bank that has out-lived its usefulness. When batteries get old or have had too many long periods of low charge, they develop a “false” charge. The old plates become covered with calcium buildup which insulates the lead from the acid and reduces the charge capacity of the battery which is like making it smaller. With no load connected to batteries in this condition, the meter can read a fairly high voltage and make you think the battery is fully charged. This same problem can also make the solar charge controller think the batteries are full and will stop the solar charging. However, as soon as you connect a large load the voltage will drop in only a few minutes to the level of a discharged battery due to the limited capacity of the built-up plates.

Taking a voltage reading of a battery that is not supplying power and one that is under heavy load will both give you a false voltage reading.

The more accurate voltage reading is when the battery is under a small load. Normally a specific gravity reading is more accurate, but you would need to check every cell as one or more could be really low and causing the rest of the cells to never reach full charge.

The old lead-acid deep cycle battery is still the lowest cost battery you can buy (although all battery prices have recently increased about 40% due to world-wide lead shortages) and they are very forgiving of over-charging, which only causes some water loss. Since your cabin is empty for many days each month and the system is not providing any power, you may want to consider a deep-cycle AGM sealed battery. However, remember a sealed battery must be charged with the correct charger settings or you can boil out the moisture and it cannot be replaced.

Time to buy batteries!

Jeff Yago

Jeff,

Thanks for the response. Since you didn’t really indicate what type of batteries (deep cycle, deep cycle marine, or automobile) I suspect you are advising deep cycle even though I have a very high current demand for a short period and probably don’t discharge the batteries below 75-80% each time I go to my cabin. I also assume there is no advantage in using 6-6 vol batteries or 6-12 volt batteries to form my 12 volt battery bank. Am I correct in these assumptions?

Thanks again,

Dave Keese

Dave:

I would only use deep cycle batteries and yes, there is a big difference between using 6 volt and 12 volt batteries. Almost all deep cycle 6-volt batteries like golf cart and L-16 sweeper batteries have double the thickness in their plates since the 6 volt battery only has 3 cells yet takes up the same physical base size as a 6 cell 12 volt battery.

Most “deep cycle” 12 volt batteries are usually the RV/marine type, which are much heavier than a car battery which is why they are called “deep cycle”, but they are about half the capacity and life of a golf cart or L-16 “deep cycle” industrial battery. I would not use the lighter weight 12 volt batteries in this application, and if you need a sealed battery, the 6-volt golf cart battery is also available in a sealed version.

Good Luck,

Jeff Yago

 

Battery Charging Rates

Sunday, October 12th, 2008

Jeff,

I would like to know what amp/hour(ah) charging rates are optimal for different types of 12V and 6V batteries used in solar applications. For instance, do marine deep cycle batteries (heavier plates) require a slower re-charge rate as opposed to a 6V golf cart battery vs a car battery (lighter plates)? What would be a typical amp break point between what is considered a slow charge vs a fast charge (2-7,10, 20 amps?)

I currently use a 12V 70ah wet lead acid battery and have been trickle charging it with a 1.5 amp charger when on a power grid (ac) and I currently have 20 watts of solar panels on my pickup shell (1-15w, 1-5w) producing, theroetically in optimal conditions, about 1.3 amps with a controller. I typically use my system just for DC lights, a car radio and a couple of DC charging units for my cell phone and my laptop and want to be able to keep it topped off in a 24 hour cycle.

This is my original system and I am looking now to upgrade my battery bank to 2-6V golf cart sealed batteries and maybe add an additional panel to beef up the charging rate.

I have been on the road for a year and have another four before I settle down into “old age.” My needs and wants are few and I’m just enjoying the journey.

Bill

Bill:

Sounds like you have been trying some interesting things with your vehicle.

For most charging applications using non-sealed lead-acid type deep-cycle batteries, most battery and charger manufacturers recommend a maximum charge rate of C/5 for a battery almost discharged until it reaches about 80 to 85% charged, then back down to a C/10 rate. This means you take the total amp-hour rating of the battery, say 220 amp-hours (typical golf cart battery) and divide by 5 giving 44 amps for a maximum charge rate to start with. This limit is an “average” and takes into account how a battery will get very hot if charged too fast, while trying to reduce the re-charge time as much as possible. Since your RV type battery will have a lower C value, its charge rate will be lower. Of course if you are using a trickle-type charge with a very low charging rate, it will never be able to reach these maximum charging rates for either battery type.

Hope this helps,

Jeff Yago

 

Back-up power for off-grid

Saturday, September 6th, 2008

Dear Jeff,

Having recently bought some land in Missouri that is located out the the sticks and very much at the end of the power grid. I have pretty well deduced that I will need some back up power.

Recently I have discovered the backwoodshome.com website and a number of your articles. As one who is not totally familiar with alternative power like wind and solar, everything I read seems only to confuse me more.

With interest I have read about l-16 industrial batteries for a battery bank in some articles. In an article about adding a solar cell to a truck camper a RV/marine battery is recommended. Since RV/marine batteries are easy to find and will take to repeated charging wouldn’t they be logical choice for a battery bank vice the harder to find L-16?

I have noticed too that with wind power most often suggested is a dc wind generator that requires upwards of 6 or 7 knots of wind to operate. In searching around I have found a source for a AC wind generator that begins operation in the sub 7knot range. AC generators have to best of my knowledge a big advantage over DC generators and that is in size of the cable between the transmission line from the tower to the battery bank. An ac generator can use a standard ac power cord and suffers no loss in current between the tower and batteries.

I have to admit that my understanding of the way a ac generator works is taken from the following website: http://www.tlgwindpower.com/default.htm On the opening page there is a photo of a customer using 9 ac wind generators on his farm in Wisconsin. Although wind power as such is confusing to me I believe that this ac system must be quite good or the farmer who had added to it and bought these generators would not be doing so if they weren’t efficient.

Perhaps you can give some insight into battery banks and DC versus AC generators in a future story. Also the battery bank issue of l-16 versus marine batteries is very confusing to a novice seeking information like myself.

Any information you can provide along these lines would be greatly appreciated.

Thank You

Keith McElroy

Keith:

Lots of questions! Actually you are talking about “L-16″ batteries, not “I-16″. When I suggest using an RV/Marine battery, you will find that it is for a small 12-volt DC system that does not have a large load that would fully discharge it each day. These batteries are much heavier duty than a typical car battery, and most have re-combiner caps and do not need to add water. However, they will NOT hold up to a daily deep charge/discharge cycling like a solar powered home or cabin. For these larger loads and system sizes, the lowest cost battery designed for a heavy charge/discharge cycling each day is a 6-volt golf cart battery ( T-105 size). These are less than $100, and can be found at most big box stores during the summer months. They are about the same size as a car battery, but because they are 6-volt, the plates are very thick and very heavy.

For a 12-volt system you will need two 6-volt batteries wired in series, and for larger systems you will need 4, 8, or 12. When you start getting above 8 batteries of any size, its better to switch to a larger amp-hr battery and stay less than 16, as this can cause problems with un-even charging and dis-charging when you have multiple strings of parallel batteries.

I think you are caught up in the AC or DC debate as a marketing ploy. There is no engineering difference in the amount of wind it takes to turn a wind turbine based on AC or DC output voltage. Wind energy is a “cubic” function of the area of the blades, and below around 7 MPH I think you will find most small-scale generators will not provide any real power, although the blades might turn. There are now both AC and DC wind turbines and each has its advantages, but only in wiring and additional equipment that will be required.

A 24 or 48 volt DC output wind turbine is very easy to add to an existing solar-power system, and some models have built-in charge controllers and can be hooked directly to the batteries. Yes, this will require a larger wire size since the voltage is lower, but the ease of wiring is its real advantage. Also, unless you are talking about some huge wind machine on a 150-foot tower, the difference in wire costs would most likely be less than 50 cents per foot for the larger wire caused by using a lower voltage DC model. An AC wind turbine can use a smaller wire size since the voltage is higher, and these are usually designed for grid-connect systems without batteries. There are a few other issues, but you cannot say an AC unit works better than a DC unit having the same size and blade design, and the reverse is also true.

Good luck!

Jeff Yago

 
 


 
 

 
 
 
 
 
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