To busbar or not to busbar

Wire will serve you fine, bus bars are a real pain to work with, you need insulated stand offs, and many things get in the way.

If you end up agreeing that for this number of batteries wire is better than busbar, be sure to look at the interconnection details found at http://smartgauge.co.uk/batt_con.html.

This is one of the rare instances of too much battery and not enough load! Forget the busbar to a parallel battery!

Ideally if you are cycling them, don't go much shallower than a 10% daily discharge, otherwise you are shallow-cycling them, and that's not good. And that is just for *ONE* 104ah battery. So that solves the busbar question - none is needed with only one battery.

For your power draw, use ONE 1040t battery, and treat yourself to an extra hour of load. Or brighter lights, what have you to get to the 10% DOD mark. Even at this small level, it is more likely your batteries will age faster than you'll ever see a payback in cycle life - especially in a cold clime like Alaska!

If you run at least the 10% DOD (aka 90% SOC), with only one battery, you'll still have 5 days of autonomy, so no problem there.

And, at very shallow depths of discharge, charging that up with a genny is very inefficient, as a light load for the genny just to do a quick top off is going to cost you in fuel. Save the genny charging for when you are down to your 4th day or so when it will run more efficiently with a real charging load placed on it.

The Concorde is a good choice, since you can easily hit them with 0.2C or more of panel current to get them charged quickly - so if you do it right, and with your small loads, you should be able to recover even under somewhat adverse conditions.

Moral - instead of using two batteries, spend the money going to the redundant battery on more panels instead for those days when it IS lights out for 2-3 days straight!

Of course if you change your load requirements significantly, then a rethink is in order. Fortunately for now you can really KISS the project.

Why would you parallel 2 12 volt batteries? No excuse for doing that. 24 volt is less expensive and more efficient.

Inetdog - thank you for the info. I was not clear in my original post, if I were to do this I would use 2/0 between battery lugs (short equal lengths) and use the busbar mounted on the wall acting as a distribution/interconnect point. These interconnects would connected to the batteries via 2/0 at a length of approx 3.5 feet. Probably does not change your point, just wanted to be clear.

PNJUNTION - thank you for the info. I will attempt to increase the load, a small fan would be good and should serve nicely for a load. Funny having to think about more load.

Sounds like I would be better served with two small chargers instead of the DLS 45, what do you think?

At what load level would combing the two batts be appropriare?

Sunking - I would rather go serial, better for the batts, more efficient, lower cost wiring. LED lights cost virtually the same. The ac batt charger is significantly more expensive and when replacing the batts I would either need two 12v or four 6v. The golf cart batts at an amp hour rate higher than 200 are pricey and for four it adds up fast. Two 12v 200+ ah batts are extremely pricey and that does not factor in freight. I am not arguing, serial is better, I am trying to explain my situation so if there are aspects I have not considered I can benefit from other's experience and wisdom.

Once I buy the 24v ac charger I am dedicated to 24v and the higher cost of battery replacement or expansion. Would serial give something in the range of 2x life span over parallel? I get that there are many more points of impact in a parallel system as far as keeping the bank balanced. Generally speaking would you expect a serial configuration to last 2x as long as parallel?

Thanks for the insight and the use of your experience. I can read and research all day long but none of that replaces where the rubber meets the road.

Mike90250 - thank you,. I appreciate the insight. Was wanting to keep things neat and organized with a minimum of taking off, putting back on for maintenance purposes. Having to rethink the busbar thing.

Or, if you know you won't be adding more load later, downsize to a single 840T. More money for panels.

The problem here is your location - in Anchorage you get what - about 30 to 45 minutes of solar-insolation per day in winter. This is when the panels can produce their rated output, and is different from sunrise to sunset hours.

You don't have much time, but fortunately your daily load is somewhat light.

So, an AGM like the Concord which can take initially accept far more current than a flooded can (limited to C/8), means that you can actually get that battery charged and stay out of a partial state of charge operation. Concord has some great docs from which you can calculate your panel needs based upon SOC vs recharge time - which in winter is only 1 hour at the very best.

The Iota sounds ok to me. Whatever you do, be SURE to have some sort of temperature-compensation going with the charge controller. That is, with a Concord that wants 14.4v absorb at 75F, that might have to be upped to 14.7v when near freezing. Automatic temp comp will take care of that for you. I think the Iota's aren't temp comped, but they claim that due to their charge algorithm it really isn't necessary - double check that.

I have a feeling that cash is burning a hole in your pocket. Let solar insolation hours, and your daily load do the talking before opening wallet.

Are you sure about that?

A DLS 27-25 averages $250, and a DLS 12-45 $175. FWIW a DLS 27-25 is larger than a 40 amp 12 volt model. Progressive RC has the Iota DLS-27-24 for $220. For your use, a 4-stage charge was complete waste of money with an AGM battery. For AGM all you need is 2-stage if you recharge with commercial AC power, just a very simple 1 stage is all that is required for solar or a generator. All you need for your application is an inexpensive RV or Marine Grade 24 volt 20 amp, or 12 volt 40 amp charger.

2/0 AWG and buss bars was another complete waste of money in your application. With your extremely small system and requirements, 6 AWG copper wire is over kill, now throw in two expensive buss bars, insulators, and termination hardware you have no need for. You are burning through money fast. Are you rich? You need to tap the breaks and learn what you are doing before opening wallet. Twp 6-volt 225 AH golf cart batteries would have cost you half that of the Concorde batteries and last twice as long.

Sunking - I have not purchased the charger, solar panels, wire, solar cc, load fuse panel or inverter yet. I have 4 Concorde PVX 1040T batts that were taken out of service after 3 years of service at a weather station on the Aleution Islands. Got them for $31.25 each. I have no misgivings, they may last year's or not. The copper for the buss bars set me back $10. The lugs for the buss bars come from recovered starter copper lugs, zero cost.

I am asking for advice prior to outlaying cash and apparently a good thing.

Your input on the wire made go back and do some calcs. I agree, 2/0 is overkill even with expansion built in. At the short distances I have 6g is good for 2% loss. If I build some expansion in 4G appears a good choice. Your input saved me some money there! Thank you

Would you have a recommendation on an AC charger? The batts will be housed indoors so extreme cold temps is a non-issue. What is your opinion on temp sensor on the batt?

PNjunction, The batts will be indoors but excellent point. Would you have a recommendation on an AC charger? Thank you for the advice.

You are welcome, that was what I was trying to do. Some people just don't get it. They want political correctness and want to be lied to. I am no liar or PC. If I hurt your feelings tough chit, get over it wussy.

You are in Anchorage right? I am not going to recommend a brand or model because it will likely not be available locally and be too expensive. What I will recommend is you visit local stores especially those who deal with a lot of Marine and RV products, and Anchorage should have a lot of Marine products. Since you are using a genny you want to minimize run time and fuel burn.
To do that means you need to do three things, and one you cannot do unless you have not bought the genny yet.

1. Size the charger for maximum Charge Current your battery can handle. If you have Concorde, If I remember correctly up to C/2. You need to double check that as part of your homework. I am not going to do it for you.

2. Do not use the genny until your batteries get to 50% DOD. Absord phase of charging, the last 10 to 20% is inefficient and slow. No reason to waste fuel charging every time your battery dips to 80 or 90% SOC.

3. Size the genny correctly so as to carry the load and battery charger. If the genny is too small you are SOL. If oversized to much is a waste of fuel and money. Genny's are most efficient when they are loaded to 70-80% capacity.

Good Luck

SK

No hurt feelings, I appreciate a straight answer. Life and my patience are too short to worry about PC. I honestly believe many of this country's problems stem from PC but that is a topic for a different forum.

About 200 miles south of Anchorage. There are a couple of Marine supply places around here so I will give them a visit.

Thank you for the insight and your time, both are valuable.