House Battery Question

[Mex-Busnut]

Dear Friends:

Please excuse my ignorance in these matters. Each Trojan T-105 6-volt battery gives 225 amp hours. So does two T-105 beatteries in series to produce 12 volts double the amp hours to 450 amp hours, or only double the voltage to 12 volts, with amp hours remaining at 225?

Thanks in advance!

[Lin]

In series, you double the voltage with the same amp hours. In parallel you double the amp hours, but stay at 6v.  No free lunch!

[Mex-Busnut]

Thanks, Lin!

Does "amp hours" mean how many amps for how many hours?

[Utahclaimjumper]

 Roughly speaking,,a 225 amps draw for 1 hour,, or 22.5 amps draw for 10 hours.>>>Dan
(remember that a 12 volt battery is depleted by 50% when at 12 volts)
(a lead acid battery in free air will lose 1 to 2 percent of its stored power PER DAY)

[Mex-Busnut]

Thanks again!

So here in Mexico, I can get the Trojan T-1275 batteries (12-volt, 280 amp hours) for about 15% more than a single T-105 (6-volts, 225 amp hours). I would be far ahead buying the T-1275?

I am looking at an initial bank of 2 or 12-volt batteries. I have a 3,000 watt inverter, and a 55-amp charger.

See T-1275 data here:

http://www.sader.com.tr/images/urunler/T1275_Trojan_Data_Sheets.pdf

[TedCalvert]

Dr mejicano loco para autobuses:

That's exactly it. Amperes for hours. At whatever voltage. Perhaps a more useful measure would volt x amperes x hours.  Like kiloWatthours.
¡Buen suerte!

Teodoro

[Mex-Busnut]

¡Muchas gracias, amigo Teodoro!

Mi inversor de corriente es de 12 voltios de entrada. Planeo agregar más adelante varios páneles solares a mi sistema.

My inverter is 12-volt input. I am planning on adding some solar panels later on.

[bevans6]

That Trojan T-1275 is a 150 AH battery.  The most commonly used rating is the 20 hour rating, and the link you posted shows 150 AH.  If your 225 AH 6 volt battery cost a notional $100, two would be 225 AH at 12v for $200, or 1.125 AH per dollar.  The T-1275 is 150 AH for $115, for 1.3 AH per dollar.  It depends on how much capacity you need, the price is not all that different, but the 12V battery, being a smaller battery, is a better deal if all you need is 150 AH.  There are other factors, like life cycle, ability to take a charge, etc, that might make the 6v T-105 batteries a better deal over several years of use, or if you needed more than 150 AH.  For the purpose of comparing, I consider the T105 size battery one half of a typical 8D 12 volt battery - half the capacity, half the weight, not quite half the cost.  That's why I use that size 6 volt battery, I use 4 to get 450 AH at 24 volts and I can lift the batteries without having to stretch and warm up first...

This is the actual battery I am using, it doesn't have an exact match to the Trojan line, it's kind of in between a T105 and a T-125.  http://www.usbattery.com/usb_us2200xc.html

Kilowatt hours is a better way to judge capacity, but no one does it.

Brian

[Ed Hackenbruch]

According to an info sheet that came with my solar panels, at 12.35 volts you have 75% charge. At 12.15 volts you are at 50% charge. At 11.95 volts you are at 25% charge.  At 11.85 volts you are below 25% charge and that is very bad for batteries. They say to try to not go below 50%.  I did not pay close attention to the voltage and the maintenance of my first set of batteries and had to replace them after 3 years. This set is twice as old and still going strong. I don't let them get below 12.2 volts and i check the water once a month. Same brand/size of batteries as the first set.

[TomC]

The easy way to figure your battery needs is to take your current amp hours and divide it by 2. So a 225amp/hr battery will actually have 112amp/hours. Divide that by 24 hours, and that works out to be a 4.7 amp continuous load-not alot. Good Luck, TomC

[Mex-Busnut]

I certainly appreciate all of your input for my ejumuhcation! I guess I am back to the T-105 batteries.

If your 225 AH 6 volt battery cost a notional $100, two would be 225 AH at 12v for $200, or 1.125 AH per dollar. The T-1275 is 150 AH for $115, for 1.3 AH per dollar.  

Brian

Wow, Brian! I wish I could buy my batteries for that price down here in Mexico! They are about 2,300 pesos each for the T-105. @ about 13 pesos per U. S. dollar, that works out to about U. S. $177.00 each!

[bevans6]

The math is more intuitively obvious if you start with $100, that's all.  But fwiw, my batteries cost $105 each, Canadian.  The advice is the same, though, start with what your needs are and work backwards from there to how to satisfy that need.  If you determine you need 300 ah, then two of the T-1275's are the better choice.  If you need 200 ah, the T-105's are cheaper.  Also take into account weight, size, cabling complexity, etc.  The reason "larger" batteries cost more per AH is usually because they deliver greater overall value in terms of performance on aspects other than AH rating.

Brian

[Len Silva]

When comparing the same type of battery, in this case lead acid deep cycle, you can be pretty confident in just looking at dollars per pound.

[Lin]

Just to add to what Len said, I have not heard of any magic batteries yet, so I generally consider weight to be a good comparative assessment of power.

[ccbmster]

Just put in four Trojan L16 H batteries a couple of months ago. 435 amp hours each and weigh about 125 pounds.  Cost me $305 each plus tax delivered and installed. Cheapest price I could find here in Southern California and the other places wanted more for them without delivery or installation.

These replaced some Trojan L16's that were 300 amp hours. So far, these new ones are one heck of a lot better investment than the old ones were.