24 versus 48 volt and panel array size

[Chewbacca]

I recently did a comparison of batteries on this forum compared to Costco and at $83.99 for a 6v 207AH battery that is said by Interstate to get 1220 cycles at 50% DOD, I came to the conclusion that they are the lowest cost in cents / kWh. That being said, their 1220 cycles may be a bit optimistic.

I was hoping someone on this forum had experience with the Trojan 2v battery they could impart.

[lkruper]

I agree that some of my batteries are 80% or less now, but I am not ready to cough up $1,488 for 9 extra hours of battery power. Solar is still saving me about $50 a month in air-conditioning grid charges. And yes mixing batteries is a bad thing, but they were cheap and big! I took the risk. The point is why buy the expensive trojan 2 volt battery? If they last 10 years they still aren't cost-effective over a 5 year Costco one. Batteries are a stupid way to store power anyways cost wise. It takes a huge number of them to power a typical house and then 5 or 7 years later you start over, and have to buy new ones. Not to mention the frickin maintenance! Now that this experiment has taught me, my future (dream) setup will use water pumped to a water tower or pond via solar panels to store energy and use a hydro generator to keep a relatively small battery bank at a constant voltage state. I haven't finished doing the math on that one though. How many gallons at what height produces... So, anyways if all I can power with virtually the same setup as the OP is a small ac unit. How is he going to power an entire house?

I recently did a comparison of batteries on this forum compared to Costco and at $83.99 for a 6v 207AH battery that is said by Interstate to get 1220 cycles at 50% DOD, I came to the conclusion that they are the lowest cost in cents / kWh. That being said, their 1220 cycles may be a bit optimistic.

[Chewbacca]

80%

So, my furry friend, how many cycles have you gotten from the Costco batteries at 100% DOD? Would that be every day for three years minus about 100? That's about 1000 cycles, and from what I have been told by the manufacturer (assuming you have Interstate Batteries from Costco) you should not expect more than 650 cycles at 80% DOD. However, that does not mean the batteries suddenly stop working. Batteries are considered time to replace when they reach about 80% of original capacity and then they will go downhill faster after that.

You may not know how your batteries are performing relative to new as you have quite a mixture of kinds of batteries as well as old and new together. I have been told that adding new batteries to old batteries also drags down the new ones to the level of the old ones.

Its good to get a hydrometer, BTW.

I agree that some of my batteries are 80% or less now, but I am not ready to cough up $1,488 for 9 extra hours of battery power. Solar is still saving me about $50 a month in air-conditioning grid charges. And yes mixing batteries is a bad thing, but they were cheap and big! I took the risk. The point is why buy the expensive trojan 2 volt battery? If they last 10 years they still aren't cost-effective over a 5 year Costco one. Batteries are a stupid way to store power anyways cost wise. It takes a huge number of them to power a typical house and then 5 or 7 years later you start over, and have to buy new ones. Not to mention the frickin maintenance! Now that this experiment has taught me, my future (dream) setup will use water pumped to a water tower or pond via solar panels to store energy and use a hydro generator to keep a relatively small battery bank at a constant voltage state. I haven't finished doing the math on that one though. How many gallons at what height produces... So, anyways if all I can power with virtually the same setup as the OP is a small ac unit. How is he going to power an entire house?

[lkruper]

Not exactly correct, but I was over-simplifying a rather disjointed process. I started with two banks of 4x6v and about 6 months later added another bank (because I could tell I was wasting a lot of sunlight) and a year later added another bank of costco batteries so I have had 4 banks of 4 six volt batteries since 2012. Then added the two used NAPA 12 volt batteries in 2013. Replaced one of those with a new one in 2014. Sometimes the solar doesn't get plugged in or vacations happen so we can subtract 200 from my original number of cycles (for the original two banks) and be a little more correct. When the inverter quits it is under load, so voltage jumps back to 21-22v pretty quickly afterwards, so whatever SOC that is. I just bought a hydrometer today, just need to learn how to use it now... You are starting to scare me... I have Zombie batteries!!

So, my furry friend, how many cycles have you gotten from the Costco batteries at 100% DOD? Would that be every day for three years minus about 100? That's about 1000 cycles, and from what I have been told by the manufacturer (assuming you have Interstate Batteries from Costco) you should not expect more than 650 cycles at 80% DOD. However, that does not mean the batteries suddenly stop working. Batteries are considered time to replace when they reach about 80% of original capacity and then they will go downhill faster after that.

You may not know how your batteries are performing relative to new as you have quite a mixture of kinds of batteries as well as old and new together. I have been told that adding new batteries to old batteries also drags down the new ones to the level of the old ones.

Its good to get a hydrometer, BTW.

[Chewbacca]

If you have the Interstate Costco batteries they are selling now, their customer service told me that they get 1220 cycles at 50% DOD and 650 cycles at 80% DOD. If I understand you correctly, you allow a 24v battery bank to get down to 19.1v, which is 1.6v per cell which is to drain them 100% every day for 5 years.

If I could ask for clarification, these are the same batteries you have had in continuous service for 5 years, draining to 0% SOC on a daily basis?

Not exactly correct, but I was over-simplifying a rather disjointed process. I started with two banks of 4x6v and about 6 months later added another bank (because I could tell I was wasting a lot of sunlight) and a year later added another bank of costco batteries so I have had 4 banks of 4 six volt batteries since 2012. Then added the two used NAPA 12 volt batteries in 2013. Replaced one of those with a new one in 2014. Sometimes the solar doesn't get plugged in or vacations happen so we can subtract 200 from my original number of cycles (for the original two banks) and be a little more correct. When the inverter quits it is under load, so voltage jumps back to 21-22v pretty quickly afterwards, so whatever SOC that is. I just bought a hydrometer today, just need to learn how to use it now... You are starting to scare me... I have Zombie batteries!!

[lkruper]

I am using the default acid/lead charging program on the Morningstar charge controller. The Power2go inverter allows drawdown to 19.1v under load before shutting off which happens daily so doing the math 365 X 5yrs = 1825 cycles. The batteries usually have about 23 volts by 6 am. At 2:40 pm with all six panel in full sun I am showing 27.1 volts with the 6k btu ac pulling a load.

If you have the Interstate Costco batteries they are selling now, their customer service told me that they get 1220 cycles at 50% DOD and 650 cycles at 80% DOD. If I understand you correctly, you allow a 24v battery bank to get down to 19.1v, which is 1.6v per cell which is to drain them 100% every day for 5 years.

If I could ask for clarification, these are the same batteries you have had in continuous service for 5 years, draining to 0% SOC on a daily basis?

[Chewbacca]

Charge

How many cycles at what % DOD have you gotten so far from your Costco batteries?

I am using the default acid/lead charging program on the Morningstar charge controller. The Power2go inverter allows drawdown to 19.1v under load before shutting off which happens daily so doing the math 365 X 5yrs = 1825 cycles. The batteries usually have about 23 volts by 6 am. At 2:40 pm with all six panel in full sun I am showing 27.1 volts with the 6k btu ac pulling a load.

[lkruper]

N

My setup is actually much worse than that. I have 4 strings of 6v golf cart batteries (costco) and 1 string NAPA 7266 commercial 12 v. (craigslist) running in parallel. Charged off 6 Sharp 240v panels 3 on east roof face and 3 on west. When new the batteries would last until 5 am now they are done at 9 pm. (part of the problem is the trees are bigger in my yard now) Running 6000 btu ac off 1500 watt power2go inverter and morningstar charge controller . Sole purpose of the solar panels is to cool the house exc in winter I run the kitchen/den circuit off it. Back to the OP I would say it depends how much he draws the batteries down. If he goes to work and turns out the lights, he should have 28-30 volts waiting for him at 6:00pm when he gets home. That should take care of the sulfate issue. No? I am by no means an expert.

How many cycles at what % DOD have you gotten so far from your Costco batteries?

[Chewbacca]

T-105 batteries

Perhaps, but are you putting six strings of four of those batteries each in parallel? In addition the OP did not have enough solar to properly keep them charged.

N

My setup is actually much worse than that. I have 4 strings of 6v golf cart batteries (costco) and 1 string NAPA 7266 commercial 12 v. (craigslist) running in parallel. Charged off 6 Sharp 240v panels 3 on east roof face and 3 on west. When new the batteries would last until 5 am now they are done at 9 pm. (part of the problem is the trees are bigger in my yard now) Running 6000 btu ac off 1500 watt power2go inverter and morningstar charge controller . Sole purpose of the solar panels is to cool the house exc in winter I run the kitchen/den circuit off it. Back to the OP I would say it depends how much he draws the batteries down. If he goes to work and turns out the lights, he should have 28-30 volts waiting for him at 6:00pm when he gets home. That should take care of the sulfate issue. No? I am by no means an expert.

[lkruper]

T-105's are fine. I have had mine over 5 years and they are starting to show their age, but still work. I only get 75% the discharge time out of them. I bought them from costco for $80 each. I don't know of ANY battery that lasts longer than 7 years when used daily. How many years do you get out of the L16RE-2V? Costco has the interstate golf cart battery for $83 +TTL.

Perhaps, but are you putting six strings of four of those batteries each in parallel? In addition the OP did not have enough solar to properly keep them charged.

[Chewbacca]

Golf Cart Batteries

Cheaper initially When they go dead from imbalance in 4 years and need to be replaced vs a proper battery that will last twice as long.
Maybe your installer is looking for recurring income every few years in battery replacement.

T-105's are fine. I have had mine over 5 years and they are starting to show their age, but still work. I only get 75% the discharge time out of them. I bought them from costco for $80 each. I don't know of ANY battery that lasts longer than 7 years when used daily. How many years do you get out of the L16RE-2V? Costco has the interstate golf cart battery for $83 +TTL.

[Sunking]

Ran some #s 12 Trojan L16RE-2V provides 26640 watt hours. At approx $400 each w/ shipping is $4800 (1110 amps * 2 volts = 2220/batt * 12 batteries = 26640, correct?) meanwhile 24 T-105 provides 32400 watt hours and they get them $140 each so $3600. So other than balance issues seems I'm getting more with the cheaper batteries. Everyone in community swears by the T-105s, even the guys that don't use this installer.

What you are experiencing is followers who only know 1 answer: 1 size fits all. That is all they know.

LISTEN my friend you need to quit being a Follower. You are being given horrible advice. Naptown, Mike, and myself are professionals not trying to sell you a damn thing. Think about it. FIRE your CONTRACTOR NOW. He is an idiot. Well maybe not an Idiot, just looking to get deep in your pockets every year which makes you an IGNORANT FOLLOWER. What he is recommending is STUPID. So are you a stupid ignorant follower or a leader looking for a better way?

Your whole system is mismatched. Nothing is designed to work with each other. What moron came up with this?

With a 1410 watt panel system can only support a 24 volt battery system of 480 AH (C/8) 720 AH (C/12). The moron has suggested a 24 volt 1350 AH battery or over twice what a 1410 watt system can support. If you do that with parallel batteries you will be replacing your batteries every year or two.

Another thing if designed properly based on a panel wattage of 1410 watts withing the range of battery it can support only gives you around 2.4 Kwh of daily power or about 30-cents of electricity. Taht means based on what you have had recomendation mean with 3 year battery replacement will cost you some $3?Kwh. You can buy it for 10 cents per Kwh. Design it correctly and you can bring that cost down to $1/Kwh over a 10 year life.

Do not be a fool and follow the pack of BAD advice you have been given.

[Naptown]

The point you and he are missing is that at that size battery bank either at 48V or 24V you do not have enough panels to charge the batteries.
your installer said you need a generator to knock the sulphate off the plates. Sorry but not going to happen. Pretty much if the batteries sulphate from a constant defecit charge no amount of generator or charger is going to help.What he was referring to was a generator to run an equalization charge which you will have to do constantly as the charge rate on any configuration of batteries at that size with the panels you have will cause the batteries to stratify. meaning acid on the bottom and water on the top. the charge rate as recommended by the battery manufacturer is to stir this up a bit during normal charging with an occasional equalization.
No matter how you cut it you either need twice as much panel or half as much battery.

[Mike90250]

More details.. to start will have 24 batteries .....

Run away, run away !
You are being fed a STORY concocted by an IDIOT. An idiot with electricity is more dangerous than a drunk behind the wheel of a school bus.

[Naptown]

That helps a lot! He mentioned would need a proper sized generator to provide backup plus powerful enough to also periodically burn the sulfate off the plates, guess that's why. Originally was going to save with a 120V AC inverter but the 240V accepts both 120 legs from the generator so can save on generator plus have inverter that can grow with my needs.

Ran some #s 12 Trojan L16RE-2V provides 26640 watt hours. At approx $400 each w/ shipping is $4800 (1110 amps * 2 volts = 2220/batt * 12 batteries = 26640, correct?) meanwhile 24 T-105 provides 32400 watt hours and they get them $140 each so $3600. So other than balance issues seems I'm getting more with the cheaper batteries. Everyone in community swears by the T-105s, even the guys that don't use this installer.

I've got to speak with him more about this 48V thing!

Cheaper initially When they go dead from imbalance in 4 years and need to be replaced vs a proper battery that will last twice as long.
Maybe your installer is looking for recurring income every few years in battery replacement.