Murdered Battery Bank

zozomike · January 2013

Battery bank design,
I have murdered my first set of batteries, so could use a bit of guidance in replacing them. While I am not without fault in this, the actual blow was by a charge controller failure while I was away for a couple of months, leading to serious overcharging. Fortunately someone was stopping by adding water, but did not understand the controller issue, so two months of boiling hastened the demise. The system is 12 ea Solar World 165s in 4 strings to feed an MX 80 and 12 each CR225 batts. Followed by a VFX3524. 4 of the batts had such low sg readings that I have eliminated that string and limped through the winter on the remaining 8. I am in a pretty good sun area, Southern Mountains of New Mexico, but often have some cloudy microclimate. Today for example blowing snow most of the day, overcast all but 2 hours so only collected 193 AH-4.9 KW per the MX80
Anyway, please check my calculations on battery sizing, and tell me what I have missed here. My calculated ( and measured ) use is 4090 per day, 80+ percent of that during the day for tools etc. very little night use except a few cfls and a laptop or sometimes a tv. Using a freezer converted to Refrigerator and that never comes on at night.

So 4090/24v=170AH/.9 ( inverter)=189/.75 ( battery)=252/.5 (DOD) =616*2 ( days of autonomy) =1009Ah Batteries. ( had 900) Sound right?

Another issue is I have never been able to get the inverter to accept my 6.5 kw Robin generator, and have been trying to get a pro to help with that but the area is a bit remote. Always receive an error msg Consequently I suppose the batts never received a full charge in winter, though summers rock! Will have to solve that soon. It seems to me my solar wattage may be a bit light for the winter, but hope you can comment.

westbranch · January 2013

Re: Murdered Battery Bank

Do you have some SG readings on the remaining batteries?
what were the charge parameters? Absorb V and time? Float V?
What did the CC do that you describe as 'failure'?
How are you charging now?

too bad about the batteries...

Sun Dog · January 2013

Re: Murdered Battery Bank

If you are using about 4kWh/day then a 1000Ah @ 24V bank seems workable to me. What type of error message was your inverter giving you? Perhaps you have an under or over frequency output issue or an under or over voltage issue.

niel · January 2013

Re: Murdered Battery Bank

zozomike,
firstly, there's no such thing as an mx80. do you mean fm80?
how do you know the cc failed? what was the failure on the cc?
your calcs may not be right on, but should work barring any bad weather or seasonal slumps. it won't hurt to add a bit more in pv, but i'll leave that up to your call as you know what you've been getting there.

westbranch,
i'd be pretty sure that the sg won't matter too much here as i suspect the electrolyte dipped well below the plates many times and they sulfated. i do hope that was distilled water that was being added too.

Photowhit · January 2013

Re: Murdered Battery Bank

Well I'm not sure about your figures or where your at in needing autonomy...

From what you've said, you had 12 - 6v 225 amp hour batteries in 3 strings for 675Ah battery bank? or did you have 16 and are now down to 12? but you say you now have 8 batteries 2 strings would be 450Ah battery? Very confusing.

Are you saying that today was a bad day in New Mexico and you collected 193Ah at 4.9 Kw(this gives an average charging voltage of 25.3, kinda scary) That's a pretty good 'bad day' I might not worry much about having more than a days storage above 50% capacity if that is what your saying...

If I follow your calculations your saying you need 185 Ah (at 90% Inverter effeciency) each day, I'm cool with that.

Then are you saying you need 252 Ah for the charging ineffiecencies? I can buy that, but you are using most of you energy during the day, so by load shifting your effectivly not needing to store as much wattage.

The you found 252/.5 = 616? I get 504 I guess this is for max discharge of 50%?

Then your multiplying X2 for for 2 days autonomy and you get back on track 504x2=1008Ah

I think you get back to the same numbers I would use, you primary use is during the day, I would call this 1 days autonomy or enough to recover after drawing the battery down to 50% after a 0% charging day in 2 days but, I think your 2Kw array should have about 5 hours of solar isolation in winter on average so it can make avalible about 5 Kw of wattage using a simple 50% calc through put calc. so I'd look at a slightly larger array.

I don't think I would go with more than 3 strings of batteries, so I might stick with what you have designed at 3 strings and increase your array a bit to help charge on those not so good days.

FWIW a not so go day here is a couple amphours and glad to have that! Rained all day today, don't think I would have harvested much more than that (I'm off line right now).

vtmaps · January 2013

Re: Murdered Battery Bank

zozomike, part of the problem is that you have parallel battery strings. As the batteries age and diverge in their electrical characteristics the charging current will not be equal in each string. A downward spiral ensues and soon you will have one string discharging into another string.

The battery bank is only as good as its weakest battery, and that weak/defective battery will drag the rest of them to its level.

--vtMaps

zozomike · January 2013

Re: Murdered Battery Bank

Wow, thanks for the attention!
Yes the number of battery strings was an error on my part and am really wanting to reduce that, indeed am interested in the forklift type of battery or a single string of large 6 volts. Sorry yes of course it is FM 80 and the way i knew it was toast was it did not power up at all, and when I sent it to Outback they gave me a new one with no questions or explanations. (oh and the floor was covered with battery acid)
As to my numbers, the 193 AH/4.9 KW was the daily stat on the FM80, and yes it was a miserable day, but had a 2 hour clearing at mid day. reading back through the last 30 days it has varied between 2 kwh and 12 kwh collection per day. As to my calculations, I just used a formula I found Xantrex had published, since I am way too ignorant to be doing this without adult supervision.
1. Average amp hours per day 4090/24=170AH
2. Divided by inverter efficiency 170/.9=189AH
3. Divided by battery efficiency (usually 0.75) 189/.75=252
5. Divided by Depth of Discharge (usually 50% remaining) 252/.5=504
6. Multiplied by days of autonomy 504/.5=1008 I chose 2 as most of my need is daytime
7. Battery bank size required 1008 or have I misused the formula?
As to the size of the existing bank, it is now 2 strings of 4 each CR225, and before was 3 strings for a total of 12 each, maybe I do not understand because 4 x 225 seems to equal 900, not 675?? what am I misreading?
As to the generator interface with the VFX3524, yes I checked the frequency and voltage input, and adjusted the idle to get those within the spec I found in the Outback literature, that was all I could think of.
One of the challenging aspects of my place is that my work often carries me out of state for 6-12 weeks at a time indeed just returned from working hurricane Sandy.

Blackcherry04 · January 2013

Re: Murdered Battery Bank

If you had electrolyte coming out of the batteries it was from the batteries being sulfated and the plates trapping Hydrogen / Oxygen. This trapping is causing displacement of the electrolyte.

I'd stick with cheap Sams $86 batteries each till you get all your issues settled especially if you cannot monitor them.

NorthGuy · January 2013

Re: Murdered Battery Bank

If you leave your batteries unattended for a long time without a generator auto-start, then eventually you get few cloudy days in a row and your batteries will get completely discharged. Most people would agree that if this happens, your batteries will die. The only way to prevent this is to have a solar array that even on a bad cloudy day produces enough to support all your loads. If you're away, your loads may be small enough for this, but you need to make sure.

zozomike · January 2013

Re: Murdered Battery Bank

Good points, had not thought of going to cheaper batts, will consider that. yes when away the loads are tiny, BTW is there any sort of meter one can buy to install after the inverter to tabulate daily total use of AC?

vtmaps · January 2013

Re: Murdered Battery Bank

zozomike wrote: »

As to the size of the existing bank, it is now 2 strings of 4 each CR225, and before was 3 strings for a total of 12 each, maybe I do not understand because 4 x 225 seems to equal 900, not 675?? what am I misreading?

One battery is 225 ah at 6 volts.
Two batteries in series is 225 ah at 12 volts
Four batteries in series is 225 ah at 24 volts

Two parallel strings of Four batteries in series is 450 ah at 24 volts.

--vtMaps

Rybren · January 2013

Re: Murdered Battery Bank

As to the size of the existing bank, it is now 2 strings of 4 each CR225, and before was 3 strings for a total of 12 each, maybe I do not understand because 4 x 225 seems to equal 900, not 675?? what am I misreading?

Serial Strings add the voltage, but the current remains the same. so... 1 string of 4 x 6V, 225AH = 24V @ 225AH

Parallel Strings add the current, but the voltage remains the same. so... 2 strings of 24V @ 225AH = 24V @ 450AH

In your earlier example, you had 3 strings of 24V @ 225AH so that works out to 24V @ 675AH

Photowhit · January 2013

Re: Murdered Battery Bank

zozomike wrote: »

Good points, had not thought of going to cheaper batts, will consider that. yes when away the loads are tiny, BTW is there any sort of meter one can buy to install after the inverter to tabulate daily total use of AC?

Any shunt based battery monitor should work for you, the Trimetric has been an industry standard, and others are out there at about the same cost. Link is for the monitor only if you use an Epanel you already have a shunt, if you need a shunt and wire there's a kit for about $50 more somewhere.

Might be good to get a handle on your over all use, before you made any battery choices. I like the forklift battery idea and went that way myself. ...but as a primary daytime user, you might be fine on a couple strings of Golf cart batteries or a single of L16 size batteries and a bit more array for the marginal days.

Others have given the info on battery ah ratings for strings. Save your batteries! Sams club charges a $15 core charge on batteries, though they will take car batteries as exchanges.

zozomike · January 2013

Re: Murdered Battery Bank

Thanks for all your comments, and thanks for not calling me a dumba.. on the Battery AH issue, even though I was. I do want to get a real use average rather than my calculations of use, I have used the killawatt on most of the loads but daily use varies so I will order a Trimetric or some such tonight. As to daily use while away,( mostly spring/summer)- That I can calculate, and it is < 400w plus whatever the inverter might use. just a couple of small daytime pumps to keep the fish and plants in the indoor 2000 gal pool happy, and the chest refrigerator kicking on rarely if never opened. So I think my solar will keep up with that, clear/cold day today and it is 2 pm and taken in 7kwh already.

Vic · January 2013

Re: Murdered Battery Bank

Blackcherry04 wrote: »

If you had electrolyte coming out of the batteries it was from the batteries being sulfated and the plates trapping Hydrogen / Oxygen. This trapping is causing displacement of the electrolyte.

Well, Bc, when I read of the electrolyte having run onto the floor, my thought was that the water refill was probably to too high a level (and perhaps done with low PV input), and the "boiling" caused enough gassing and perhaps additional heat to displace the electrolyte out of the cap vents, but unrelated to suplhation.

IMHO, would not expect too much reversible sluphation to exist on batts that are boiled every day, and would expect gas bubbles to escape in time (to be replaced with new ones) Difficult to guess just exactly what happened with the CC, but too bad about the CC and batteries, but good of OB to have replaecd it. YMMV, Good Luck, Vic

westbranch · January 2013

Re: Murdered Battery Bank

write down all your findings and then add them up, you probably will be surprised... Actually it is better to start with a list of what you 'think' you have and then start measuring... and see just how much more you find that isn't on the first listing.

hth

Blackcherry04 · January 2013

Re: Murdered Battery Bank

Vic wrote: »

Well, Bc, when I read of the electrolyte having run onto the floor, my thought was that the water refill was probably to too high a level (and perhaps done with low PV input), and the "boiling" caused enough gassing and perhaps additional heat to displace the electrolyte out of the cap vents, but unrelated to suplhation.

IMHO, would not expect too much reversible sluphation to exist on batts that are boiled every day, and would expect gas bubbles to escape in time (to be replaced with new ones) Difficult to guess just exactly what happened with the CC, but too bad about the CC and batteries, but good of OB to have replaecd it. YMMV, Good Luck, Vic

I guess since neither one of us were there, we'll have to guess. Your two theories have merit, not worth nit picking about, chicken or the egg. Could be a combination of all.

zozomike · January 2013

Re: Murdered Battery Bank

yes, well as I do not understand the circuits of the FM 80, and as it was dead upon my arrival, I assumed that it had fried in a way to still allow unregulated dc to the batts. In that case they could have been seeing over 90 volts, so I figured I was lucky they had any charge instead of being bits of shrapnel. I guess the fuse would have blown if that was the case however. I looked at the suggestion to go for cheap deep cycles, but do not understand how to approach 6-700AH 24v bank with 12 volt 115AH batteries and keep the strings below 3. Thanks though

inetdog · January 2013

Re: Murdered Battery Bank

zozomike wrote: »

but do not understand how to approach 6-700AH 24v bank with 12 volt 115AH batteries and keep the strings below 3. Thanks though

You can't. That simple.
You can use 230AH six volt batteries, putting four of them in series and then paralleling two strings to get closer.
Or you can use 345AH four volt batteries, use six of them and put two strings in series to get more than you need.
Or you can go whole hog and use 12 690AH 2 volt batteries, putting all 12 of them in one series string.

There are lots of other combinations, but those use batteries of approximately the same power capacity each as you mentioned.

In real life, if you look at RE batteries, you have a lot more choices to make it happen.

If you already have all the 12 volt 115AH batteries you need, your best bet would be to go to 48 volts instead, so that you only need 300-350AH.

zozomike · January 2013

Re: Murdered Battery Bank

Yes, thats the way I figured it, just someone in the thread suggested them. Thanks, i will be going with larger AH batts and fewer strings

Photowhit · January 2013

Re: Murdered Battery Bank

zozomike wrote: »

yes, well as I do not understand the circuits of the FM 80, and as it was dead upon my arrival, I assumed that it had fried in a way to still allow unregulated dc to the batts. In that case they could have been seeing over 90 volts, so I figured I was lucky they had any charge instead of being bits of shrapnel. I guess the fuse would have blown if that was the case however. I looked at the suggestion to go for cheap deep cycles, but do not understand how to approach 6-700AH 24v bank with 12 volt 115AH batteries and keep the strings below 3. Thanks though

I don't see any reference to 12v 115aH batteries, Sams club and Costco sell 6V 220Ah Golf cart batteries for around $80 each + $15 core charge, They will take an auto battery in exchange usually.

The problem with going to a 48V system is replacing the inverter, not cheap. I really wouldn't look at replacing your batteries until you know your loads.

I had said something about getting a handle on your loads, but wasn't thinking about your primary use being during the day. Much of your use will be ahead of the shunt so you may not get accurate readings on daily use with the Trimetric, since your converting close to directly from the panels and reducing the charge going to the batteries, likely the reason you could see so much incoming Ah on your Charge controller but have an average charging voltage at 25.3V(I think that's where you were at). Can you measure a complete cuirut with a Kil-A-Watt meter?

zozomike · January 2013

Re: Murdered Battery Bank

Hmmm, as to using the Killawatt P4400 Ive got, I will have to puzzle how to use that to measure total use. A few of the circuits have just one load on them like the refrigerator, and I've done that. I will have to go to a Sams I guess, I called Costco Albuquerque and all they have in supposedly deep cycle it the aformentioned 12 volt, 115AH. Anyway I had just ordered the Trimetric from NAWS. Probably need it anyway. Still think the best option is a forklift batt like yours. Just have to be sure of the size and learn how to enclose and temp control it outside. Anyone have experience with GB Industrial batteries? free shipping, certainly not the Quality of the Crown, but would save a couple grand considering the shipping to my area.
I JUST WANT TO SAY HOW AMAZED AND GRATIFIED I AM AT YOU FOLKS TRYING TO HELP HERE.

Photowhit · January 2013

Re: Murdered Battery Bank

That's who I used, too short a time to know yet, just a couple years. Alls well so far, thit isn't getting enough work as I purchased another place. Don't beleive them if they tell you all taxes paid quote, they don't pay state sales tax! lift gate truck was $200 extra I think. Had mine made with flags rather than plug since they couldn't figure out what the appliance side of the battery was and quote me a price on a cord for that...

Also be aware that the lift gate truck might be 55 feet long! they couldn't get closer than 12 feet from my battery box, making for a long afternoon moving the battery into the box. Somehow I figured a small box truck. The shipping is by freight not GB's doing.

Ralph Day · January 2013

Re: Murdered Battery Bank

I have a Subaru (Robin) 5kw diesel generator. The voltage regulation is not performed by any fancy electronic method but old fashioned, bullet proof condensor type vr(if I recall correctly). It's really intended for robust loads like construction equipment, but would operate with my Xantrex 4048. It's frequency control is strictly speed controlled, so to get it down to 62hz unloaded (so the inverter would lock on) I had to rig a throttle control for it. just a long bolt fastened to the floor plate and pushing up on the throttle/cut off lever. Worked fine. Never use it (more money than sense at the time. Try selling a $5K generator when you can buy new for $1500).

If you have a K-W meter plug it in to the genset's output and see what the freq and voltage are like. |It could be that the inverter can't lock on. The old lightbulb load might help with inverter aquisition.

Ralph

zozomike · January 2013

Re: Murdered Battery Bank

Cool-- Thanks Photowhit, glad to know you chose them, as for me, I'm up a windy dirt road that freight trucks will not touch, so I will have it dropped at the hardware in town and have a small backhoe with slip on forks I can handle it with. NM forgives sales tax on solar applications so will work that out with the vendor. Looks like your cabin system is about the same size as my whole shebang. I did not know they sold cables also? I will begin some discussions with them. Want to add a watering system also, seems like a must given my parapatetic life style.
Thanks also Ralph, I had used a multimeter, checking the frequency but the Killawatt will be much simpler, Looked at your project, wow!

Photowhit · January 2013

Re: Murdered Battery Bank

Well I don't know if they do either, but they can make them, they do for the batteries, which standard come with and Anderson(?) connector unless you ask for something different. Something I didn't find out until after the sale, though I was specific in my intended use is that they make a battery specific to renewable enegy use. Might be worth finding out more about it/them.

Nice to have the equipment to move the battery around. 1100 lbs will be a pain even mounted on a pallet for a long distance on a backhoe. The battery is tall and skinny, if you can arrage it perhaps you can meet them at end of the road, though $200 can buy a lot of diesel, though if they can move it in the truck you could pull it off the back. So you wouldn't need the lift gate.

mike95490 · February 2013

Re: Murdered Battery Bank

Ralph Day wrote: »

I have a Subaru (Robin) 5kw diesel generator. The voltage regulation is not performed by any fancy electronic method but old fashioned, bullet proof condensor type vr(if I recall correctly). It's really intended for robust loads like construction equipment, but would operate with my Xantrex 4048. It's frequency control is strictly speed controlled, so to get it down to 62hz unloaded (so the inverter would lock on) I had to rig a throttle control for it. just a long bolt fastened to the floor plate and pushing up on the throttle/cut off lever. Worked fine. Never use it (more money than sense at the time. Try selling a $5K generator when you can buy new for $1500).
If you have a K-W meter plug it in to the genset's output and see what the freq and voltage are like. |It could be that the inverter can't lock on. The old lightbulb load might help with inverter aquisition. Ralph

I have a 6hp single cylinder 650rpm listeroid diesel engine, driving a ST generator head. The ST head has no regulator, but instead, has a fancy (crude) "harmonic winding" that self regulates to almost the desired voltage. The frequency wobbles a bit, from 62 - 58 hz, but the XW has a wide enough acceptance range, that it's had no trouble locking on, and charging batteries from it.
Attachment not found.

zozomike · February 2013

Re: Murdered Battery Bank

Hate to keep this open too long, but as I have decided to go with the forklift battery and watering system, will have to put that outside the shop in a new enclosure. A friend suggested I retain 4 of my best cr225s as a backup in case of catastrophic failure of the GB Industrial battery, I was thinking to install those in the same enclosure and use the Magnum Energy Smart Battery Combiner to keep them charged, does this sound like a brilliant idea or just dumb redundancy?

BB. · February 2013

Re: Murdered Battery Bank

It is over kill/dumb redundancy until if/when you need it.

-Bill

Vic · February 2013

Re: Murdered Battery Bank

Hi zozo ,

An auto-watering system CAN deprive the person responsible for batt maintenance of valueable information -- just how much water each cell is using. AND, some of these systems make measuring SG difficult, or perhaps more messy. Have not followed the design refinements, but this was the case for some systems.

If the watering system does make SG measurment more difficult, and therefore done too infrequently, this could cause the bank harm.

The healthiest battery systems I've seen are those where the maintainer of the batts is directly involved in monitoring water useage, Voltages, SGs, aromas, cleanliness etc.

Just my thoughts. Good Luck! Vic

Murdered Battery Bank

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