10 Posts
Jul 4, 2008 12:35 pm

I have 8 12V batteries parallelled togather with 105 amp hrs each. They are marine deep cycle batteries which I understand are not a true deep cycle battery.

My question is will I be much further ahead by purchasing 8 6V T-105's and stringing them together?
Will that give me more storable energy or less for the night time hours.

Please reply as I am new to the solar arena and don't want to spend the money unless it will improve my ability to store the capacity.  Thanks!
220 Posts
Jul 4, 2008 04:02 pm
Re: Batteries

hi david.
 all things being equal and they never are. the T105,s will increase your storage capicaty by 60ha. we would a little more info on what your goals are.
 if your goal is the cycle this size bank on a daily basis we are talking about a 2kw array!

all the best 73 dave
Jul 4, 2008 04:05 pm
Re: Batteries

All I can tell you is what I might do in your predicament.
More than likely I would use what I had for as long as I could, then move on to the true deep cycle battery.
For one thing I don't know the age or condition of the batteries your using now. I have used that type of battery before. I think the name was Stow Away. Bought them a Wal Mart. Even tried some 8D big rig cranking batteries. Nothing like those can compared to the Trojan T-105's. I got 8 years out of a set of 12 T-105's wired in series/parallel for 1320 amphours at 12 volts nominal. Of course I pampered them, not to mention I sized the bank 5 times higher than what I use each night and I would rotate them once a year.

I have to warn you about something on those T-105's though. Those offset terminals will break off. Then you have to drill and tap whats left and be careful not to over tighten the bolt in the soft lead.

Presently I am using 8 Surette S-530's in series/parallel for 1600 amp hours at 12 volts nominal. Which is about 6 times what I use each night. I am shooting for 20 years on these.
The biggest thing to remember is to recharge what was discharged as soon as possible. I sized my PV array to replace what I use each night (plus about 20% more) with one days worth of clear sky sunshine during the Winter months.
Equalizing is very important as well. Any time I go several days* without that sunshine, I always equalize them afterwards. A battery monitor, such as the Bogart 2020 is invaluable. A must have. I am sure you know about the distilled water allready and keeping everything clean, tight, and corrosion free.
If everything is sized right and the region you live in is moderate (no extremes) you can go without a back up generator.

* About 5 days, more if I know its going to happen and cut back usage
Jul 4, 2008 04:26 pm
Re: Batteries

Some reading material if you wish it.
10 Posts
Jul 4, 2008 05:17 pm
Re: Batteries

Ok, so I live really simple and I am off the grid with a hybrid system of Solar 480 watts with a Honda Generator and a small Wind Generator of 400 watts.
I am pioneering so to speak and solar is rare in my neighborhood so we have to pay for most advice.
I have been learning on my own by trial and error. So far I have been able to survive reasonably well. I live on my own and run a small refrigerator that consumes 150 watts when running, a television at 150 watts, and a laptop computer.

I have a limited budget and have been working this battery bank for one year but would like more storage for night time usage. Am I dreaming or can I do better with the Trojans or something better?

Or would I do better just saving my money? What would be a better way to go with my low end system for a stronger battery bank that would give me longer juice time through the night?
10 Posts
Jul 4, 2008 08:21 pm
Re: Batteries

Lets just say... When it comes to batteries, "I don't have a clue!"

All I know is that I am getting storage capacity but would like more if at all possible yet still have a balanced system that will be effecient.

Any ideas would be greatly appreciated and just curious to know what most of you would do with a small system such as mine to give me the best bang for the buck?   Thanks, Dave
220 Posts
Jul 4, 2008 08:31 pm
Re: Batteries

 gee david that sounds like a nice setup you have there. those loads are very reasonable. i figure you are at 3kwh a day tops. those pv modules should be putting away about 1500wh a day. i'm not counting the turbine if its the one i think it is. that leaves another 1500wh a day to be made with a short generator run. i have a feeling you are not topping off the banks at the end of each day? you should be able to make it through the night and then some. did this bank ever last the night? i would not drop a grand for those new t105's until i figure out why this one year old economy bank has let you down. we may be dealing with some less than ideal wiring methods.

info please.
 are these all dc loads? they should be in your case.
 are you inverting?-lots of uncalculated load if so.
 are you topping off at the end of each day with the honda?- you must.

all the best, dave.
220 Posts
Jul 4, 2008 08:41 pm
Re: Batteries

oops. you caught me between posts.

i'm gonna catch hell for this but i would not hesitate a minute in adding more new batteries of the same type to a one year old bank. there i said it.

all the best, dave
10 Posts
Jul 4, 2008 09:13 pm
Re: Batteries

Thanks Dave for the reply!

I am willing to try anything new for efficiency.

I am using a vector inverter for all ac loads. No DC in the shack. I have available electricity in the house when I wake up for coffee and toast but the cloudy days leave me with no play room.

How many batteries would you add and when you say to top off the load daily with the generator, how long should I run the gen for a "top off?"

Much appreciated!  Dave
10 Posts
Jul 4, 2008 09:37 pm
Re: Batteries

Dave, I will help cover you for your insight!
The battery bank is 9 months old to be exact.
So, with that saying, how many batteries would you add?  Dave
184 Posts
Jul 5, 2008 09:44 am
Re: Batteries

Since the existing batteries are less than one year old, I wouldn't hesitate to add more batteries of the same type.  That would be the least expensive route.  I've used the same type of battery, and true deep-cycle or not, they're pretty good for the money.

If you decide to build a new battery array, you might consider adding a switch so that you can connect bank 1, bank 2, or both.  That's what I did.  It is more work though.  I normally have the new bank switched in, and I have to remember to charge the old bank once in awhile.  Here's a diagram:

220 Posts
Jul 5, 2008 12:47 pm
Re: Batteries

ok now we are getting a handle on what you have. that vector inverter (using the vec050 as an example)advertises a 90% efficency but that is the power conversion efficency only- there is also a load from the cooling fan "super turbo cooling fan" gotta love those ad men. anyway that load is not counted in the efficency of the unit. its about 40wh. if we run the inverter full time thats about 1kwh a day!
 dave. i do hope you have gone over to solarjohns link and spent a few minutes, hours, days reading. he has a treasure trove of info there. go to his 3/28/07 posting and grab his battery soc chart. i lifted it the day he posted it (thanks john) you do have a multimeter? if not go buy two they are cheap. and with two you can cross reference if you don't believe the first reading. follow johns chart for topping off the banks with the honda. as far as adding any and how many new batteries to the bank goes thats for your pocketbook to decide but at fifty cents per amp hour they are a low cost and effective way to go. now here comes the sticky part of this post. if you have your bank wired like almost all the diagrams you see on the web you have what i call a "self amplified battery bank unbalancer circuit" built into your bank. what i would do is tie these batteries in pairs and pull from the cross corners with all the cable as long as the longest up to a central main busbar. then from the bus to the inverter. you want to sink and source all your power from that bus. you can pick up some real nice 200amp rotor switches for the strings of batteries coming up for less than five bucks a pop. that will end any battery balance issues and give you great control and monitoring abilities. check my gallery photos to get a visual of what i'm saying. also a good starting place for sizing your bus is a minumim one square inch of 1/4 bus plate (cda110) for every 80amps crossing it. fifty bucks will get you a 1/4 x 2 1/2 x 12 inch blank. bigger is better and you will want a good size to land all those big lugs. hope this helps.. please wait for some other comments from more expierenced re folks before ripping your system apart on just my advice. i'm experienced in power systems but still a newcomer to renewable energy.
all the best, dave
10 Posts
Jul 5, 2008 07:44 pm
Re: Batteries

Thanks Dave for the great info. Quite a loss with the inverter! Might have to look at other options to get me out of the hole!

Always appreciate the knowledge of others!


                     Thanks, Dave
Jul 6, 2008 06:49 am
Re: Batteries

I too, know about living on a tight budget. For 20 years I lived without any electricity at all.
Just when I thought all of my "tuffing it out" was over, the economy changed. The price of everything started going up and up. But living within my means has payed off in other ways. More and more I have been seeing lots of people having to get rid of a lot of there "big boy" toys. What was once under their shelters is now in the front yard with a for sale sign on it. At least I am not having to give up anything.
About "tuffing it out." If you do not have a battery monitor, such as the Bogart 2020, get one. Knowing exactly what is going on with your system is very critical to operating and maintaining it. As well, how to spend those precious few dollars on improving on the system to fit your needs.
Being able to, see, the amphours in and out. Knowing how the voltage fluctuates; hour to hour, day to day, month to month, and season to season can educate you about your system in ways that no thing or nobody ever could.
A battery bank can be a major investment. Sizing it to last for many, many years is imperative to say the least and you want be happy about the investment. That you made a good investment. The last thing I want to be sore about, year after year, is that I made a bad investment in a battery bank and judging by your posts, you feel the same way.
With a battery monitor, you can know exactly what your amphour needs are as compared to the amphours produced.
And don't forget our host Alt E Store.
220 Posts
Jul 6, 2008 12:11 pm
Re: Batteries

yes david, i concurr with thomas that a system monitor may be the best overall investment you could make at this point. real time information will give you an intimate awareness of whats happening with every component of your system. read, research, expierment. knowledge is power. you will become an expert on your system in no time and as a result of your new insight will have a more efficient system with greater capacity simply by default!

all the best, dave
10 Posts
Jul 6, 2008 02:29 pm
Re: Batteries

Much appreciated guys!

I added 2 batteries yesterday and did a 30-60 minute generator run to top it off last evening and actually woke up with a full battery bank this morning.

Beautiful thing!

I will look into buying the battery monitor very soon and as always... Thank you tons for your knowledge and help!

184 Posts
Jul 7, 2008 10:26 am
Re: Batteries

I agree that a battery monitor is a good investment, but I must confess that I haven't bought one yet.  I keep careful watch over my system manually, with a Digital Voltmeter.  I also use a data logger now and then.  I usually set it up to take battery voltage readings at 5 minute intervals.  After about a week, I download the information to my computer for display or printout. It is interesting to watch as the voltage begins to increase as the solar panels get morning sun, and watch it decline as the sun goes down in the evening.  I watch the effects of clouds, and of loads switching in and out.  Most importantly, I watch to make sure that my batteries are getting fully charged, and that they don't discharge too deeply.  It's easy to see when the charge controller switches to float mode.  I can also use it to monitor the voltage from my pv array, although that information is not as useful.  My data logger is not as accurate as the DVM.  You can find more information about the data logger I use at:


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