Calculating Amp and Usage Draw

[satorizero]

Hello, my first post here, but have viewed many other posts to help me.

This is my setup:
600w total solar (I think its in series, its technically not my system so am learning still)
Outback Flexmax 60
6 Lead Acid Group27 batteries, in 3 parallel strings of 2 batteries each in series, ~100Ah each = 300Ah
Trace 4024 inverter/charger
Generac LP3250

A little more info before my question:
We had the system installed by a "professional" of 30+ years, so after fixing his battery connections and replacing all 10 batteries with 6 "reconditioned ones", we are here.
We are trying to power the following things. Lets assume we are using them all at once, I just want to know how long they will last.

1 laptop, power block says "100V 1.5A" and "19V 3.42A"
1 laptop, power block unknown yet but lets just double the one above
1 9.9w LED bulb
1 53w ac halogen bulb
1 unkown ac bulb, lets double again
3 1141 dc bulbs

The calculation I made is as follows, but this is the first question with it: "am I calculating amps correctly"

(some are rounded up)
1 laptop 3.42 A (I chose that because supposedly laptop use around 65W, which it totals using that amperage, 19V x 3.42A)
1 laptop 3.42 A
1 LED bulb 0.089 A
1 53w bulb 0.44 A
1 bulb 1 A
3 1141 1.5 = 4.5 A

Total - 12.869 amps (lets say 13)

So, having 300Ah total, and wanting to only use 50% DOD, we have around 150Ah usable capacity.
150Ah/13A = 11.53 hours run time.

Thats my calculation.

Unfortunately, we are using power too fast.
I think its either:
#1 We are using more electricity than I know of
#2 The batteries are 20Ah (meaning really ****ty and not 100Ah)
#3 Or my calculations are incorrect

Id like to assume the batteries are in good condition and that we are using less power than I stated.
So I would like to first tackle calculations.

~ For everything, we are going DC, to AC, then to DC/AC again.
Laptop are DC -> AC -> DC (right?)

~ So, do I calculate amp draw using DC or AC?

~ How about my 9.9w LED bulb?
It says ON the bulb 9.9w, 0.089A, 120VAC
My power coming in is around 110V!, does that change things?
Arent LED's dc? If so that means theres a converter in the bulb, so its going DC -> AC ->DC as well?
How do I calculate it all if I dont know whats using AC and whats using DC?

I know using DC or AC will dramatically change the amp usage calculation. Please help.



(Recap:
~ assuming batteries are good. Are reconditioned good? If not, then how low would a 100aH battery go to upon reconditioning?
~ do I use DC or AC calculations? or both?
~ also, the owner wants to buy (as many batteries as it takes to add on), all my research says running more than 4 parallel strings wil imbalance things, but how bad? Is it worth trying to talk out of?)




Thank you in advance! The more solid info the better

[sensij]

It will be easier if you think of everything in power:

Laptops = 65 W * 2 = 130 W
1st LED = 9.9 W
AC Halogen Bulb = 53 W * 2 = 106 W
1141 bulb = 18.4 W * 3 = 55.2 W
Total = 301.1 W

At 24 V, that is 301.1 / 24 = 12.5 amps. There are some conversion losses that will make this number higher... I'm not sure what rule of thumb to use, but let's say 50% covers it... 1.5 * 12.5 A = 18.75 A.

If your 300 Ah batteries were healthy, and you run to 50%, that is 8 hours.

I have no idea how you could parallel three pairs of batteries in a way that would keep them balanced.

Edit, edit: I misread your battery type, ignore the following, since you don't have AGM's
Edit: Also, your array is undersized. 600 W / 24 V = 25 A (on a perfect day, not counting conversion losses). 300 Ah / 25 A = 12, which means you have at most C/12 charge current. Those AGM batteries would want a higher charge current than that... C/5 is a decent target. See this thread for more information.

The combination of the undersized array and the battery wiring probably means your assumption of good batteries is false. I would guess the batteries are shot.

[Sunking]

You start by totaling watt hours used in a day. Amp hours are meaningless until you determined watt hours and system voltages. Once you do that then you design and I bet you will find you went way off the beaten path.

Watt Hours = Watts x Hours
Watts = Voltage x Current. At the voltage and current the device uses, not what the name plate says.

Once you have your daily watt hours useage, next comes your solar insolation tables for the worse time of year where it will be used. Once you have your numbers read this and draw it up.

[inetdog]

Watt Hours = Watts x Hours
Watts = Voltage x Current. At the voltage and current the device uses, not what the name plate says.

And, especially for motor loads like refrigerators or some energy efficient lighting like fluorescents and LEDs, even the measured amps time the measured volts is not what the real power consumed it. It can often be less by as much as 50%. Which is why buying an actual energy/power meter like the Kill-a-Watt (TM) is a good investment for planning. It will let you run your refrigerator or computer all day and give you the total energy instead of having to count the minutes on and off through the 24 hour period.

[satorizero]

Thank you guys for the (quick) responses

I do know what Sunking and inetdog are saying, im aware of what formulas to use in the sense you guys say it. I was just confused by what formula is used if the system converts between AC and DC so much... so according to sensij, none of that matters... only what matters is the total watts that the devices claim to use. (Yes of course having a watt meter is a great way to know, but I left mine in another state and have yet to buy one :P )

So im trying to do it with real calculations, even if theyre not perfect... I wanna know how close I can get, which is pretty damn close to what sensij got minus the efficiency losses :0

Some things that werent directly answered by one (or more) of you guys, and some clarifications:
#1 My calculations say im only using 150Ah due to not wanting to go below 50% of the capacity, so wasnt sure if sensij got that, or if im missing something.
#2 Sensij said he wasnt sure how I could balance 3 strings of batteries, I wasnt sure if the intention was "I dont know how" or "I dont think you can", so I kinda needed that touched on a bit more.
#3 I wanna give info on the solar array: all the issues with it, they still fully charge the batteries within 4 hours of sunlight, at whatever the FM is set at by default (the Trace is set at 15 amps charging when using the generator). So my point is, the charging of it isnt part of my questions, its mostly about after theyre completely charged
#4 Sensij assumed the batteries are shot... but we bought them like 4 days ago, from a company that reconditions them... so if the assumption is that theyre shot, id like to know why that conclusion was made..
#5 Im adding up watts, and determining how long that'll last by dividing amp hour capacity by amp use, I think thats a correct forumula yes?

So far what I get form the responses, is that I should just use whatever it does say on the name plates (because my voltage fluctuates), and add it all up and ignore if its dc or ac... idk...

So thank you again you guys, but please feel free to take some extra time if you have it, to clarify deeply and concisely (I can follow along ).


p.s. thank you again Sunking, I know your every knowledgeable because ive seen your posts allot here, and I will rethink what calculation I use... but I got extremely close to what sensij got by using my amp hour formula.. so im confused if my formula was wrong or not.

[Sunking]

Thank you guys for the (quick) responses

I do know what Sunking and inetdog are saying, im aware of what formulas to use in the sense you guys say it. I was just confused by what formula is used if the system converts between AC and DC so much... so according to sensij, none of that matters...

No that is not what he is saying. For a battery system efficiency is 66 down to 50%

[satorizero]

Before you guys answer... on the flip side I did do watt hours before...
I WAY overshot by saying that we use 300w total (which is crazy because theres no way were using even half that)

So lets say I wanna use 300w as long as the batteries can last... well, how long should it last?
I get 8 hours in many of my calculations...
we're only lasting like 4 hours on full charge.

[Sunking]

Before you guys answer... on the flip side I did do watt hours before...
I WAY overshot by saying that we use 300w total (which is crazy because theres no way were using even half that)

So lets say I wanna use 300w as long as the batteries can last... well, how long should it last?
I get 8 hours in many of my calculations...
we're only lasting like 4 hours on full charge.

Impossible to answer because you have not given any information to answer. How much gas do I use in 4 hours? Can you answer that? Why can't you answer?

300 watts x 4 hours = 1200 watt hours.
Battery Capacity in WH = Battery Voltage x Amp Hours. So how long will 300 watts last. You tell me, I don't have a clue becaus eyou have not given any useful information. What I can tell you if you use 1200 watt hours in a day using a 12 volt battery will take a 12 volt 500 AH battery.

[satorizero]

Lol, im trying to get you to answer to help me

According to the formula you just said, 24V x 150Ah = 3500 WH for the batteries

So that means 3500WH / 300W = 11.6 hours...

which again, comes back to why are we only lasting 3-4 hours?

What info are you missing? Help

[sensij]

What info are you missing? Help

The answers to your questions would come from diagnostic equipment and reference material that I guess you don't have. Watt meters to get actual power consumption instead of guesses and fudge factors based on equipment ratings. Clamp on current meters to see how balanced your battery bank is. Battery manufacturer / part / model numbers to see what the recommended charge and discharge cycles are. What "reconditioned" means according to whoever sold the batteries to you, and how damaged they might be from their history prior to that.

Edit: Also, add to your load list another 16 W for the inverter.

[satorizero]

Thats a good answer.... then no calculations matter until that is known..

[sensij]

Thats a good answer.... then no calculations matter until that is known..

Mostly, but regardless of the condition of the batteries today, the setup you have described is not conducive to a long life for them. If they aren't the problem yet (a big if), they will be sooner than you'd like, I think.

Edit: Where did you get 15 A as an appropriate charge current when running the generator?

[satorizero]

Im aware that the battery life can be compromised, knowing why you say that would help though

And yea, well then really none of my questions could be answered because we all conclude it should last 8-10 hours and im only getting 3-4, so idk what to say haha.

And the 15A settting on the Trace (which is only on when generator is on), was set from its default 30A... which I just assumed was way too high for a charge, partially because the batteries were boiling out sprinkles of liquid...

p.s. the owner of the system told me today he could care less about the batteries... so again, my questions only pertain to how much time I can get out of the setup in its current setting, and how to calculate it... which seems impossible to get close to accurate.

[sensij]

Being out of balance will shorten the life. I had misread your battery type earlier and edited my post, but 30 A should not really have boiled 300 Ah of battery, that is only C/10. Are these gel batteries?

Edit: How do you know they are fully charged? What is the resting voltage you get?

Also, in full disclosure, if Sunking and Inetdog are part of the "A team" of battery troubleshooting, you have to work pretty far down the alphabet to get to me. I try to help where I can though, and I'm sure someone will jump in if I lead you too far astray.

[satorizero]

Being out of balance will shorten the life. I had misread your battery type earlier and edited my post, but 30 A should not really have boiled 300 Ah of battery, that is only C/10. Are these gel batteries?

Also, in full disclosure, if Sunking and Inetdog are part of the "A team" of battery troubleshooting, you have to work pretty far down the alphabet to get to me. I try to help where I can though, and I'm sure someone will jump in if I lead you too far astray.

No no, I appreciate everything you say trust me, the more responses the better

And they are for sure Lead Acid batteries...
Idk, maybe im missing something here... they were boiling, maybe charge amps arent all that they need to boil, but its voltage charge is normal default on it :/
Ah well..

So yea