Wiring for 16 6 volt batteries

bmet · August 2011

Re: Wiring for 16 6 volt batteries

I am sorry that I don't have a computer tool that can illustrate the series connection. With your parallel example there are 4 pairs of wires(8 total cables) being combined. in a series example there are 5 wires.

Cariboocoot · August 2011

Re: Wiring for 16 6 volt batteries

Perhaps this will make it clearer. It's a bit small.

Note that battery fuses should be on the positive wires between the strings of batteries and the bus bar (long red line).

mike95490 · August 2011

Re: Wiring for 16 6 volt batteries

Well, I think you are crazy for planning a 16 cell / parallel system @ 24V. I'd strongly suggest you consider the move to 48V for this project, and consider L-16 400A batteries, just 2 parallel strings

You will need 4 fuses, one on each string, and they have variable resistances too.

But, golfcart batteries are cheap, so maybe it's a good starter set, but you can still do that in 48V. 8 batteries in series, 2 parallel banks, much easier to manage.

mike95490 · August 2011

Re: Wiring for 16 6 volt batteries

bmet wrote: »

The upper part of that illustration, since it is from Smart Gauges' diagram, illustrates a parallel connection. You have continued their example by keeping those 4 groups all wired in parallel, giving you 3600AH at 6V. To achieve 24 Volts, these 4 groups need to connected in series. If I remember the battery FAQ, the interconnecting cable between the 4 groups needs to be able to carry the total current of each parallel set.

I think your reading of the picture I'm seeing, is wrong, the one I see, is 4 banks of 4, which is 4, 24V strings

(Whoops) I COMPLETELY mis-read that. each group of 4 is wired in parallel. If they were in series, you'd have 24V strings.

Maybe I should go home from work now

Cariboocoot · August 2011

Re: Wiring for 16 6 volt batteries

mike90045 wrote: »

I think your reading of the picture I'm seeing, is wrong, the one I see, is 4 banks of 4, which is 4, 24V strings

In the diagram Kefalonianman supplied, the four batteries in each "string" are connected in parallel (+ to +, - to -) and each string is in parallel - giving 4000 Amp hours @ 6 Volts.

Got to agree with Mike about the power vs. system Voltage; you're looking at a 10 kW hour potential here, and that is better suited to 48 Volts.

solar_dave · August 2011

Re: Wiring for 16 6 volt batteries

Kefalonianman wrote: »

It is , this is the one that was recommended as the best configuration am I right that this gives me 900 amp/h

Thanks paul

It gives you 6 volts not 24 if I read it right.

oops late to the party!

Kefalonianman · August 2011

Re: Wiring for 16 6 volt batteries

I am having a dilemma I have been looking at some of the formulas on here and concluded the following can anyone confirm I am right

I have a 900 amp h battery system and from the formulae I am going to need approx 3400 watts of power to maintain my system is only 2000 at the moment what would be the consequences of running this system as it is or do I need to eliminate 8 batteries and reduce to 450 amp h and if I did this how do I maintain the other 8 so they do not die.

Or can I wire it differently using all 16 batteries to create 450 amp h

In need of some direction as new to all this and want to get my system to run efficiently

Many thanks in advance

Kefalonianman · August 2011

Re: Wiring for 16 6 volt batteries

Mike

Changing to a 48v system would solve my battery problem but I have two turbines which run and their own charge controllers at 24v

How would I adapt these to work at 48v there are from wind energy 7
Paul

mike95490 · August 2011

Re: Wiring for 16 6 volt batteries

If these are the low hight case batteries, you might get away with lower than recomended charging amps. If they are the tall L-16 cases, you won't have enough power to properly bubble and stir the electrolyte. You might need to run a genset once a week to assist charging them.

And you will have to watch your loads, if you pull 60ah, but only replace 55ah, on a regular basis, it may take 2 weeks to bleed the batteries down low enough to find you have a BIG problem (all batteries ruined).

Kefalonianman · August 2011

Re: Wiring for 16 6 volt batteries

Mike

At the moment I am running on 8 and only have two turbines and 4 * 110w panels the batteries last 7 hours before they get o the recharge volts of 23.9 I presume with the added solar and batteries I will probably recharge ever two days would this be feasible

Paul

Kefalonianman · August 2011

Re: Wiring for 16 6 volt batteries

Mike

Forgot to mention they are t105 Trojans

Cariboocoot · August 2011

Re: Wiring for 16 6 volt batteries

Your math is correct:

900 * 0.10 = 90 * 29.6 = 2664
2664 / 0.77 = 3459 watts

Right now you have eight * 185W = 1480 Watts total. You plan to add six * 185W bringing the total array size to 2590 Watts.

If you run the formula in reverse you get:

1480 Watts * 0.77 = 1139 / 29.6 charging Volts = 38.5 Amps potential peak current. That's 4.2 %, below the minimum for 900 Amp hours. (If anyone is wondering: multiply the expected current (38.5) times 100, then divide the result by the total Amp hours (900) to get the percentage.)

For the full expected array you get:

2590 Watts * 0.77 = 1994 / 29.6 charging Volts = 67.3 Amps potential peak current. That's 7.4% and will work, providing your load draw at the same time doesn't exceed 2% (18 Amps). Most of the time it's unlikely to, as that would be 432 Watts.

Remember: charging isn't not going to be maximum Voltage at maximum Amps for the whole time. It will start out low, and as the sun comes square on the panels their output will go up increasing the Amps. As the batteries charge their Voltage will come up and the Amps will taper off.

Mike mentioned the tall case batteries appetite for current and that is true. But these are T105's and they can get by on 5% net charge rate potential. Until you get the rest of the panels installed, watch them carefully - especially the SG. If you're getting a full Absorb cycle every day and spending some time in the Float stage they'll be fine. If not, once a week charge up with the generator just to be sure.

There's no way to include all the batteries and have it come out as 24 V & 450 Amp hours, but you could divide the bank in two and use a battery switch http://www.solar-electric.com/basw1300amp.html to change between the two halves. Just don't get confused about which one is charged and which one isn't.

Kefalonianman · August 2011

Re: Wiring for 16 6 volt batteries

Thats excellent news as it going in the right direction and if I add another 6 next year I am ok to do this and improves the system more.

Can I ask a generator question, at the moment I use mains to recharge my batteries and at about 2.2 to 3 kw to charge it defeats the object of producing,

How often should you charge your batteries and can I use the xantre to automatically do this whether they need charging or not as I am way some times 3 months at a time or would I be better getting a genie on a timer system and do they do diesel ones as I have a large diesel tank in the garage

What do you think the cost savings are from a genie to mains if any

Many thanks again you have all been very helpful

Paul

Cariboocoot · August 2011

Re: Wiring for 16 6 volt batteries

Paul;

I don't know what they charge you for electricity there, but usually grid power is far cheaper than generators or solar. Off-grid solar is ten times the price of utility power here. The general rule is: "Got grid? Use it!" But if the grid price is absurdly high ( over $0.50 per kW hour say) or unreliable then the solar/generator choice makes more sense.

Some inverters can automatically start some generators based on a pre-programmed low Voltage setting. But unattended generators can be troublesome - like running out of fuel or not starting for some other reason when no one is around to fix it. The grid power is probably a more dependable choice, even if it's 'undependable'.

In your case you're probably better off buying an Iota charger like this http://www.solar-electric.com/ioen40amp24v.html and plugging it in, leaving it connected. Such a unit would keep the batteries up as needed, working with the solar. Downside is the cost, especially as you might need two chargers to keep that big bank "happy". Also I don't know if they are available for your grid power, which is probably 230 VAC 50 Hz not the 120 VAC 60 Hz we use over here.

Photowhit · August 2011

Re: Wiring for 16 6 volt batteries

Kefalonianman wrote: »

How often should you charge your batteries ...Paul

You should be charging when the wind blows and the sun shines, the charge controllers should make sure the batteries are not over charged. You should have no ploblem using energy while the batteries are charging.

Also while it is fine to add new panels to old(though you might want to be sure they are like panels) adding new batteries to old tends to be problematic.

Kefalonianman · August 2011

Re: Wiring for 16 6 volt batteries

Photo whit

Thanks for your reply, but youhave confused although very easy on this subject as I am new,

So when the sun is shining midday I should charge my batteries and then at night when no su. Use my batteries

Is that what your saying, also would 2st or 3stage charge and do It every ay or every two days

Paul

Cariboocoot · August 2011

Re: Wiring for 16 6 volt batteries

We're all confused. If we were any more confused we'd be the Canadian Senate!

Obviously you can't charge from solar when the sun doesn't shine.
Obviously you can't charge from wind when it doesn't blow.
Obviously you must use battery power when neither sun nor wind is present.

Kefalonianman's concern was with leaving the batteries unattended and not knowing if there would be sufficient sun/wind to keep them charged against loads that would continue running in his absence, since the system is a bit marginal on charging anyway. For those circumstances he wanted an automatic back-up charging system powered by grid or generator that would be available just in case the solar & wind didn't manage to keep up.

Anybody unconfused now?

Kefalonianman · August 2011

Re: Wiring for 16 6 volt batteries

Sorry to go on with this one, I see the uderstanding but my Charge will only flow from the solar if it is higher then the batteries.

So if charging in midday sun and my batteries are say 27 volts I am losing the nennifit of the sun if my batteries were only 25

Am I looking this wrong ........or do I need the basics in solar

Forgot to mention 2 stage or 3 stage best

Paul

BB. · August 2011

Re: Wiring for 16 6 volt batteries

Using 12 volts (just double the numbers for 24 volts):

Battery charging: ~14.5 volts
Battery equalizing: ~15-15.5 volts
Vmp-panel STC : ~17.5-18.0 volts (ideal PWM or low end of MPPT charger)
Voc-panel STC : ~21 volts or so... (Vmp and Voc move together)

Yes, the Vmp of the panel (Voltage maximum power) needs to be higher than the battery voltage in order to get current to flow. And Vmp falls as panels get hot (leaving black panels cooking on roof--they tend to be "warm" during the middle of the day).

Voc on cold days (and below freezing especially) causes the panel (open circuit) to be high, which can damage charge controllers (cold panel, battery bank full, no charging current needed).

For a place with high/low temperatures (mountains, deserts, etc.), you can get almost a 2:1 range (Voc-cold:Vmp-hot ~ 30 volts:15 volts).

Batteries themselves, have some "natural voltage points:

Resting voltage: ~11.6 to 12.7 volt is, roughly dead to full at 77F/25C (battery voltage runs higher as temperature drops)
Charging voltage: will increase to ~14.2-14.8 volts (depending on battery type and charger set point between "bulk" and "absorb" -- this is the point from where the battery accepts all the current the charge controller can output--to when the battery charger starts limiting voltage to set-point. Charging current will slowly drop until ~1% of battery capacity rating). This declining charging current will last around 2-4 hours or so.
Float voltage: around 13.2 to 13.7 volts or so... Charging at this voltage will keep battery bank charged without over charging/damaging the battery bank.

So, for your 24 volt system, we would expect your Vmp-array to be around 35 volts STC (standard test conditions). If your Vmp-array is different than 35 volts--there can be issues.

Too low, you will not properly/quickly recharge your battery bank.

Too high, you will "waste" power when using a PWM controller. But, it will charge OK (as long as Voc-cold is not too high for your controller).

MPPT type charge controllers (much more expensive) can take high voltage Vmp/Voc arrays and efficiently "down convert" from high voltage/low current to low voltage/high current to charge the battery bank (sort of like an AC transformer that takes 120 VAC and can charge your 12 volt battery bank).

You have many options here (solar array configuration, charge controller type/size, battery bank configuration, inverter configuration, etc.)... There are no black and white answers here.

What we really try to help you do is to identify your needs (loads, watts, watt*hours, etc.) and help you configure a system (on paper) that will meet your needs (and your bank account).

Also--as you go through the detailed design--you will start to learn about your system and understand better how to maintain and debug your system as needed (where to connect a volt meter and what the readings mean).

-Bill

Cariboocoot · August 2011

Re: Wiring for 16 6 volt batteries

Kefalonianman wrote: »

Sorry to go on with this one, I see the uderstanding but my Charge will only flow from the solar if it is higher then the batteries.

So if charging in midday sun and my batteries are say 27 volts I am losing the nennifit of the sun if my batteries were only 25

Am I looking this wrong ........or do I need the basics in solar

Forgot to mention 2 stage or 3 stage best

Paul

There I believe you're talking about two different things.
Yes, charging Voltage has to be higher than battery Voltage. This is not likely a problem because "24 Volt" panels actually have a Vmp around 35 Volts; more than enough to supply the necessary charging when the sun shines brightly upon them.
The other thing is that as batteries charge they don't need as much current; the Voltage comes up, the current goes down. This is a diminishing need for the total potential Watts the panels can produce in full sun. That's when we get in to load shifting; the process of deliberately running things when the batteries are charged and the sun is full so that you can make use of the Watt hours that otherwise would go "unharvested" if you were only charging batteries.

Are we getting closer to clarity?

As for 2 stage vs. 3 stage charging, I favour 3 stage for FLA batteries. That's Bulk/Absorb/Float. Equalization is something to be done only on an "as needed" basis in my opinion, although some battery manufacturers recommend a regular EQ regardless.

Kefalonianman · August 2011

Re: Wiring for 16 6 volt batteries

Lot of information there ton take in .. Thks

Can I start by saying I did a 3 stage charge last night and it has charged then switched to float at 26.6 and stayed there constantly and it is drawing 400 watts from the mains to run the load I.e 400 watts

If I was to leave the machine like this I presume when the sun comes up or wind blows it will continue to add to the float charge up to the cut off point, but does the float stay on continuously as I don't understand how the batteries would ever meet the recharge valve of 23.9

Going back to BB

I have the following setup at the moment

Equalize 31
Recharge 23.9
Bulk 28.7
Absorb 28.7
Float 26.6

As its a holiday home usage is generally around 200 - 250 but when here 400 -500 unless wife's using hairdryer or Hoover lol

I do have the xanxtrex 60 a controller which is not connected up yet and my new panels say 32.7 on the back and are to be connected in two series rows of 4

My wind controller starts to heat up the element when voltage is too high and this is done at about 28

As I am not here can I ask how you would use the system, my aim is to get the other 12 panels fitted and then purchase a solar pump for my pool as at the moment this runs on 3 phase direct from grid

Many thanks

Paul

BB. · August 2011

Re: Wiring for 16 6 volt batteries

Hi Paul,

If you have a grid connected power and an AC powered battery charger--your batteries will never go through a recharge cycle unless you draw more power than the batteries can supply.

I am wondering a bit about the 23.9 volts (11.95 volts ref @ 12 volts)--That is fairly well discharged resting state--and probably pretty down there when measuring a battery under load. It might be better to start recharging at 25.2 (12.6) volts or a little lower--Basically below the resting voltage of a fully charge battery bank.

Also, what is the recommended charging voltage (bulk/absorb transisions) for your batteries. Flooded cell tend to be higher voltage than AGM/Sealed batteries.

For AC power, charging them at a lower voltage is probably fine. For solar, charging them at a higher voltage will probably charge quicker and capture more solar power from the panels (before throttling back for absorb).

-Bill

Kefalonianman · August 2011

Re: Wiring for 16 6 volt batteries

So can you tell me how i should have the system setup as at the moment with it in float all mynloads are coming from the mains And I believe the xantrex does not share current when in float stage

Should I use grid support and at what voltage would you set

And if I set the recharge to 25 I think the system would be recharging ever coup,e of hours maybe different when I connect the other solar up would have to try and see

Would it help if I send you my setup and also figures in the xantrex inverter

Paul

BB. · August 2011

Re: Wiring for 16 6 volt batteries

Just post them here... Also, you can create a "signature" that has your setup in it... Makes it easier for us to keep track (you will need to "Show your signature" in your next post (below the posting/edit window)--then it will automatically show in all your new postings.

-Bill

Kefalonianman · August 2011

Re: Wiring for 16 6 volt batteries

Inverter enabled
Search mode disabled
Grid support enabled
Charger enabled

Low batt cut out 22.5
Loco delay 10 sec
High batt cut off 35
Search watts 50
Search delay 2 sec

Batt type custom
Eqlz support enabled
Eqlz voltage 31
Bulk voltage 28.7
Absorb 28.7
Float 26.6
Batt temp -28mv/c

Batt cap 440 ( others not connected yet)
Maz chg 35%
charge cycle 2stage
Batt temp warm
Recharge 23.9
Absurd 180

No charge block times

Hope this helps paul

Kefalonianman · August 2011

Re: Wiring for 16 6 volt batteries

Just connected up first 4 panels and at 8:40 am they were producing 114 v will have 8 panels installed by tonight and we can look at setting up the system with the correct figures hopefully

Wiring for 16 6 volt batteries

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