UPS batteries for grid-connected emergency battery backup - Use deep cycle or not?

[lkruper]

80% discharge for lead-acid can sometimes be unrealistic due to voltage drop. Beyond 50%, the voltage drop is enough that inverters and the like start to run hot and inefficient, some gear goes intermittent, displays flash, that kind of stuff.

In the early days, agm marketing was that they were good to 80% but in the real world, the voltage drop put everyone back to designing around no more than 50%.

Napkin calc: With 800 wh, and assuming a 12v cabin setup, (800w / 12v = 66.6a drawn total) that means at least a 120ah rated battery.

Many choices depending on how willing you are to maintain / replace them. But you want 10 years (possibly unrealistic under the best conditions) and have a genny to provide some real recharge after a deep-discharge event.

Personally, I'd recommend an Odyssey PC-2150 / 2250 agm for your load requirements stated at this time. BUT you MUST be able to accurately control the float voltage to satisfy the warrantee, which in this case is 13.5 to 13.6v. NOT 13.2, nor 13.8v !! That is a *single* Odyssey, not a bunch of lower capacity cells paralleled together. Odyssey's do well when put into standby service such as you desire IF you follow their charging regimen. You may not get exactly 10 years out of them due to simple aging, but if any battery can do it with proper maintenance, they will. Essentially the Odysseys are consumer level Enersys batts, which of course make high-end commercial setups, but even at the consumer level their high voltage under load and low internal resistance allows them to handle huge surges and so forth. Expensive, so be sure to get your load requirements right off the bat.

Make regular tests of the system, say once a year to 50% DOD.

Or you could use a bunch of starter batteries if you were willing to trash and replace them every so often. Choice is yours....

Thank you! I am very impressed with what I am reading in their manual (http://www.odysseybatteries.com/docs...M-002_1014.pdf). They don't seem to be overly concerned about the occasional really deep cycle and also bill this as having an 8-12 lifetime in standby mode.

I also like the fact that I can get them on Amazon and they offer Prime shipping. I would be inclined to buy their charger as well and see they make a 50A charger (although I am not finding it for sale anywhere... some saying it was discontinued).

[Sunking]

However, in an emergency I would want them to perform like RE batteries. I could live with less cycles ( because I won't need them) but would want those cycles to have the same effectiveness as RE batteries.

UPS batteries are high performance batteries. They can be be charged and discharged at much higher rates then a deep cycle. Their discharge curve is almost identical top deep cycle, they just do not sag like deep cycle. What you give up is a lot of cash and cycle life. They cost 2 to 4 times a deep cycle FLA and only last 1/10 to 1/5th as long. Instead a 1 Kwh battery costing $200 and lasting 1500 cycles you pay $$400 and get 150 cycles. But they will run circles around a deep cycle FLA for the first 100 cycles or 5 years whichever occurs first.

[PNjunction]

80% discharge for lead-acid can sometimes be unrealistic due to voltage drop. Beyond 50%, the voltage drop is enough that inverters and the like start to run hot and inefficient, some gear goes intermittent, displays flash, that kind of stuff.

In the early days, agm marketing was that they were good to 80% but in the real world, the voltage drop put everyone back to designing around no more than 50%.

Napkin calc: With 800 wh, and assuming a 12v cabin setup, (800w / 12v = 66.6a drawn total) that means at least a 120ah rated battery.

Many choices depending on how willing you are to maintain / replace them. But you want 10 years (possibly unrealistic under the best conditions) and have a genny to provide some real recharge after a deep-discharge event.

Personally, I'd recommend an Odyssey PC-2150 / 2250 agm for your load requirements stated at this time. BUT you MUST be able to accurately control the float voltage to satisfy the warrantee, which in this case is 13.5 to 13.6v. NOT 13.2, nor 13.8v !! That is a *single* Odyssey, not a bunch of lower capacity cells paralleled together. Odyssey's do well when put into standby service such as you desire IF you follow their charging regimen. You may not get exactly 10 years out of them due to simple aging, but if any battery can do it with proper maintenance, they will. Essentially the Odysseys are consumer level Enersys batts, which of course make high-end commercial setups, but even at the consumer level their high voltage under load and low internal resistance allows them to handle huge surges and so forth. Expensive, so be sure to get your load requirements right off the bat.

Make regular tests of the system, say once a year to 50% DOD.

Or you could use a bunch of starter batteries if you were willing to trash and replace them every so often. Choice is yours....

[lkruper]

i had a 145 ah telecom agm battery, it was a big heavy battery and I used it everyday connected to my 240 watt panel. Even though it worked performance was not good. Even with minimal use every morning it was reading 12.2 12.3 volts. i use it for about a year before I decided to upgrade to something better.

I replaced it with a kinitek kh2000, 102 ah agm. A smaller lighter battery. With the same use, this battery is 12.5 12.6 in the morning. A very big improvement. After a year of use the battery still reads 12.9 when its fully charged.

In a emergency, I dont think the telecom battery would provide enough power before dying out. They might be cheaper and because of there size and weight look like they are powerful but from my experience I would maybe buy one and see the performance before committing to buy a large qty.

The only reason I thought about UPS batteries, is because I had heard that it is not recommended to use them for RE applications. If the converse were true, then I wanted to investigate whether or not they would be a good choice for my application, which is grid-tied stable power but for emergency outages.

However, in an emergency I would want them to perform like RE batteries. I could live with less cycles ( because I won't need them) but would want those cycles to have the same effectiveness as RE batteries.

In looking online at some batteries advertised for Telecom/UPS it appears they are designed for fast response at higher amperages. One, MK, only gave performance up to 60 minutes. I would want my batteries to perform over-night. So it appears that I have eliminated these types of batteries for what I am trying to do.

Now I am wondering again, if a good compromise might be to get a good RE battery but spec it out to use 80% of capacity with the knowledge that I won't need that many cycles. I floated that idea here in the last few weeks on the basis of the %DOD/Cycle charts provided by the manufactures. However I was cautioned that even though the manufacturers gave that performance spec on their sites, one could not count on getting the advertised # cycles at the 80% discharge load.

[jony101]

i had a 145 ah telecom agm battery, it was a big heavy battery and I used it everyday connected to my 240 watt panel. Even though it worked performance was not good. Even with minimal use every morning it was reading 12.2 12.3 volts. i use it for about a year before I decided to upgrade to something better.

I replaced it with a kinitek kh2000, 102 ah agm. A smaller lighter battery. With the same use, this battery is 12.5 12.6 in the morning. A very big improvement. After a year of use the battery still reads 12.9 when its fully charged.

In a emergency, I dont think the telecom battery would provide enough power before dying out. They might be cheaper and because of there size and weight look like they are powerful but from my experience I would maybe buy one and see the performance before committing to buy a large qty.

[lkruper]

Put it to you this way and then you decide.

Telecom batteries are top notch high performance batteries and extremely expensive. Even if I needed a high discharge rate I would not use them new because of expense vs time, literally 1/2 to 1/3 the cost using something else better suited to the application. Telecom is on steroids and a special breed of battery. The are built to go fast, and fast cost money.

However if you have an application where you only need say 10 cycles a year, batteries at or below salvage value, and willing to take a calculated risk might work out for a year or two.

Allow me to guess. You know a guy who has access to salvage telecom batteries cheap right?

No, I have no contacts and have no knowledge of salvage telecom batteries. However I know I have seen battery replacements for UPS systems for sale and wondered if they would be better suited to my requirements than RE batteries.

For what I want, with the projected limited use of the batteries, I would like them to last 10 years, if possible.

However, if you are recommending salvage telecom as inexpensive and useful, I would consider them because I am told I will probably destroy my first set of batteries.

[Sunking]

Put it to you this way and then you decide.

Telecom batteries are top notch high performance batteries and extremely expensive. Even if I needed a high discharge rate I would not use them new because of expense vs time, literally 1/2 to 1/3 the cost using something else better suited to the application. Telecom is on steroids and a special breed of battery. The are built to go fast, and fast cost money.

However if you have an application where you only need say 10 cycles a year, batteries at or below salvage value, and willing to take a calculated risk might work out for a year or two.

Allow me to guess. You know a guy who has access to salvage telecom batteries cheap right?

[lkruper]

Perhaps "CANNOT" is a bit of of over statement, replce with "Should Not" be used for daily cycle service. For one simple reason, UPS and Telecom batteries were not designed daily cycle service, they are designed as Emergency Stand By service operating as Float Service. The batteries are designed for very high discharge rates. To get that you have to sacrifice cycle life. Pushed into cycle service you would be good to get 200 cycles.

However can you use them?

Yes now that you know

Thanks, Sunking.

What batteries should I consider for my application? Batteries that will sit charged except for "emergency" drills and when utilized may be used for one day or two weeks every couple years at the most?

[Sunking]

Perhaps "CANNOT" is a bit of of over statement, replce with "Should Not" be used for daily cycle service. For one simple reason, UPS and Telecom batteries were not designed daily cycle service, they are designed as Emergency Stand By service operating as Float Service. The batteries are designed for very high discharge rates. To get that you have to sacrifice cycle life. Pushed into cycle service you would be good to get 200 cycles.

However can you use them?

Yes now that you know

[lkruper]

I have heard it discussed that one cannot use UPS batteries for Renewable Energy storage because they are not designed for repeated cycling.

What about battery backup for emergency usage? Would UPS batteries have some sort of advantage over deep cycle batteries such as price or performance?

It is likely that if I put batteries in place to supplement the emergency generator at my cabin that I might want to add a battery bank just in case there is a prolonged outage (more than a few days). I think I can get my daily load down to 800 watt hours or so.

I have not had any power problems for 5 years and it is possible I might not have any for the next 5, but this is kind of like insurance.