Help choosing new batteries

palausystem · December 2015

The Surrette batteries are on their way out after about 7 years. Looking for FLA about 340Ah. Considering US battery US 305HC XC2. Only has a 1 year warranty. Cost is a concern. This one is about $210. The supplier is close by, 10-15 day lead-time.
Anyone have experience with this type? Or other recommendations? All of the "RE" types seem to be either AGM or closer to 400Ah. (and pricey).

BB. · December 2015

Sounds like you did OK on the Surettes (7-8 years is doing pretty good).

How many parallel strings (if any) are you planning one?

-Bill

vtmaps · December 2015

I have Interstate L-16 batteries... they have several distributors in VT. They are make by US Battery. I am familiar with a dozen or so systems that use them and they seem to run 6-10 years in off grid use.

US Battery makes several sizes of 6 volt battery. In each size they make a "HC" version (high capacity). I'm not exactly sure what gives the HC version the extra capacity... it might be higher SG of the electrolyte.

On the advice of a couple of installers in my area that I trust, I did not get the HC version. They say it doesn't last as long. I do not have personal experience relevant to this issue... I am spreading rumors on the internet

--vtMaps

Vic · December 2015

The US battery, US 305HC XC2 appears to be a Floor Scrubber type battery, and weighs-in at about 96 Lbs, which is a bit light for an L-16 Deep Cycle battery.

These Scrubber batteries are usually in the low-cost end of many battery manufacturer's lines.

Agree with vtmaps, that these may not be the best battery for off-grid RE applications. Seems that many manufacturers DO increase the SG of the electrolyte to get a bit more Capacity, and this is generally detrimental to battery life. However, this particular battery has a stated target SG for a complete charge at 1.270, which is moderate, IMO.

Looking at the Cycle Life verses Depth Of Discharge, have never seen any manufacturer ever spec cycles to less than 90% State Of Charge (SOC) ... Those curves imply a nominal battery life of about 275 YEARS, for very slight discharges on a daily basis, IIRC ... Simply INCREDIBLE!

If this is the battery that you can afford, you seem to have few choices. And, if carefully attended to, a bank of these batteries may well last for 2 - 5 years, depending ... just guessing.

Good Luck, Vic

Dave Angelini · December 2015

vtmaps said:

I have Interstate L-16 batteries... they have several distributors in VT. They are make by US Battery. I am familiar with a dozen or so systems that use them and they seem to run 6-10 years in off grid use.

US Battery makes several sizes of 6 volt battery. In each size they make a "HC" version (high capacity). I'm not exactly sure what gives the HC version the extra capacity... it might be higher SG of the electrolyte.

On the advice of a couple of installers in my area that I trust, I did not get the HC version. They say it doesn't last as long. I do not have personal experience relevant to this issue... I am spreading rumors on the internet

--vtMaps

The OP should use the "XC" version from US. The 2V and 6V have been excellent and they are made for your order. This can take longer but if long life is the goal and not cost, they are pretty hard to beat. The Surrettes have been fine of late but I did have a bad spell with 3 of my clients. Terrible service from them at that time but they have replaced the BOZO that was doing customer disservice.

palausystem · December 2015

BB: I currently have two 400 Ah strings of 8 batteries each at 48 volts. 800Ah total. I only have 3.1 Kw of panels and so am trying to get a smaller battery this time as we only use about 5.5 or 6 Kwh per day. Does this sound sensible? Last year I was involved in a discussion here and some posters were suggesting that 800Ah was way too much for those panels and said I only need about 500 Ah battery bank but I am a bit hesitant to go that low. I'm thinking 680Ah might work. What do you think?

palausystem · December 2015

Dave Angelini said:

The OP should use the "XC" version from US. The 2V and 6V have been excellent and they are made for your order. This can take longer but if long life is the goal and not cost, they are pretty hard to beat.

Dave - I think you mean the US REL L16XC (many others use the 'XC' in the name).
My issue is partly trying to get a smaller battery - that one is 400Ah as are most of the "good" batteries. I need one in the 340Ah range but I certainly don't want one that will only last 2 years. But in that range it seems like "scrubber" batteries are all there are to choose from. If I got 7 years from the Surrettes on too few panels (see my previous post) then maybe I should stick with the 400Ah.

palausystem · December 2015

Can't seem to find Interstate L-16 on the internet. Did US battery take over that role as VT Maps suggested?

Dave Angelini · December 2015

The difference in 400AH and 340AH is just math and not really noticeable. You had good luck before, why change?

softdown · December 2015

Here you go: http://www.ehow.com/list_7540891_interstate-l16-battery-specs.html

palausystem said:

Can't seem to find Interstate L-16 on the internet. Did US battery take over that role as VT Maps suggested?

softdown · December 2015

According to: http://www.ehow.com/list_7540891_interstate-l16-battery-specs.html

The HC variant weighs ~8 pounds more. I don't see a higher SG contributing nearly that much weight in that volume of space. Perhaps the plates are a bit thicker and/or of a superior alloy (higher concentration of lead)? Interesting that the higher SG argument would cause the lower life argument that has been presented. Perhaps all three.....higher SG...thicker plates....higher concentration of lead?

I have been called an idealist a few times.........I consider juicing a batteries specs by increasing the SG to be dishonest unless there is a warning to that extent. Otherwise, 99.9% of the consumers are going to believe they are getting a superior battery. Instead....they are getting a lower life.

Shoot...consumers think they are making "informed decisions" if they compare the CCA ratings of a battery. I presented the real world of "CCA versus deep cycle" on a board. My argument was ignored.....by almost everybody. I think one viewer gave it a "blue star"....probably for its length.

In the world of batteries.....size and weight means more than many other things. A lot of people get fooled by select tweaking, and misunderstanding, of Ah (and CCA) ratings.

vtmaps said:

I have Interstate L-16 batteries... they have several distributors in VT. They are make by US Battery. I am familiar with a dozen or so systems that use them and they seem to run 6-10 years in off grid use.

US Battery makes several sizes of 6 volt battery. In each size they make a "HC" version (high capacity). I'm not exactly sure what gives the HC version the extra capacity... it might be higher SG of the electrolyte.

On the advice of a couple of installers in my area that I trust, I did not get the HC version. They say it doesn't last as long. I do not have personal experience relevant to this issue... I am spreading rumors on the internet

--vtMaps

706jim · December 2015

While not exactly along the same lines as solar batteries, I installed a set of two Sears group 27 Die Hard batteries in my powerboat. These are used 6 months of the year and sat in the boat for the six winter months. Both were shot after three seasons. I replaced the Die Hards with lower capacity group 27's and they lasted at least 10 seasons.

My point?

Getting a higher rating out of a given case size means that there are probably more but thinner plates to get the surface area needed for an impressive Ah or CCA rating.

Using this same logic, I recently replaced my solar batteries with the lower Ah Trojan L16's (370Ah) hoping for increased life over other models with ratings of up to 550Ah.

Time will tell!

BB. · December 2015

The first question to ask--Is what is a success for you?

I.e., a $2,000 battery bank that last 7 years or a $1,000 battery bank that lasts 5 years. From a price point of view, the "cheaper/smaller" bank is more cost effective. From a maintenance point of view, you are replacing batteries more often. What is most important for you?

I will do the math--But frankly that is just a starting/sanity point. Brand quality, how much of a pain checking/servicing 24 cells in one string vs 48 cells in two strings, above comment about life, etc. are those questions that others here (who live off grid) can answer better than I (on grid/not a battery engineer engineer).

6 kWH per day, assume 2 days of "no sun", 50% maximum.

6,000 Watt*hours * 1/0.85 ac inverter eff * 1/48 volts * 2 days storage * 1/0.50 max discharge = 588 AH @ 48 volt battery bank nominal

If you go with a 688 AH @ 48 volt battery bank and aim at 5% to 13% rate of charge:

688 AH * 59 volts charging * 1/0.77 panel+controller derating * 0.05 rate of charge = 2,639 Watt minimum array
688 AH * 59 volts charging * 1/0.77 panel+controller derating * 0.10 rate of charge = 5,272 Watt array nominal
688 AH * 59 volts charging * 1/0.77 panel+controller derating * 0.13 rate of charge = 6,853 Watt array "cost effective" maximum

A 3.1 kWatt array is on the small side for a full time off grid home and this size battery bank. Of course it depends a lot on where you live (hours of sun per day, by season) and your power needs (not much in the winter, etc):

http://solarelectricityhandbook.com/solar-irradiance.html

3,100 Watt array * 0.52 off grid system eff * 4.0 hours of sun (reasonable winter sun for many areas) = 6,448 WH per day

So, if you live in a reasonably sunny area, a 3.1 kW array should meet your needs for 9+ months of the year. And you have been living with the system for 7 years--happily? During winter/bad weather, you may have to run the genset a bit more to avoid going much below 50% state of charge during bad weather... But with a less costly battery bank, you perhaps can justify hanging more panels?

I don't want to disregard your experience--It is very important--Look at what you have learned over these last 7+ years--What would you like to see different (less genset run time, save money on battery bank, 1 string and 1/2 the number of cells+cables to maintain, use more power, run large well pump/shop tools, etc.)?

More or less, a 10% difference in numbers (AH capacity, solar array wattage, etc.) is a "don't care" amount of difference. A 2x difference is "care".

Changing from an 800 AH to 680 AH battery bank, you probably would hardly notice and differences because of AH capacity (brand, model, battery type, will be more of a difference).

-Bill

palausystem · January 2016

softdown said:

Here you go: http://www.ehow.com/list_7540891_interstate-l16-battery-specs.html

Thanks for the link but it's not on any Interstate website I can find.

palausystem · January 2016

Dave Angelini said:

The difference in 400AH and 340AH is just math and not really noticeable. You had good luck before, why change?

That's a good question. I thought 7 years for the Surrette was not so great. I was hoping for 10. I thought it was due to not enough panels to battery size and thus more deficit cycling. So trying to bring battery size down even by 120AH seemed like a good idea.

But you and others seem to think 7 years is pretty good so...

Certainly swapping out the bank at 5 years or less would be no fun at all...

palausystem · January 2016

vtmaps said:

I have Interstate L-16 batteries... they have several distributors in VT. They are make by US Battery. I am familiar with a dozen or so systems that use them and they seem to run 6-10 years in off grid use.

Do they look like this: http://usbattery.com/products/6-volt-batteries/us-re-l16-xc2/

From what I can see It looks like the 6v L16 type 'premium' batteries come in about 400Ah. Not less. A GC (golf cart?) style 'premium' (RE designation) battery from US battery is 242 Ah. So if I'm shopping for a 6v 'premium' battery it looks like I'm pretty limited in my Ah choices.
Is that your understanding? I mean, it seems like if I want the good one I'm stuck with 400Ah.

And thanks to BB for running those numbers and giving me some things to think about.

Would like to hear what others think about an 800Ah battery and 3.1kWH array in SF Bay Area... is it "OK".

vtmaps · January 2016

palausystem said:
Thanks for the link but it's not on any Interstate website I can find.

The Interstate web site is for consumers, and the L-16 size batteries are considered industrial. Here's a page that shows Interstate's L-16 sized batteries, the UL16 and the UL16HC.

by the way, Interstate does not make batteries... the batteries they sell are made by a number of manufacturers and can change at any time. Currently their L-16 size batteries are made by US Battery. Interstate's strength is their distribution network. The only reason I deal with them is because they will sell me a US Battery L-16 close to where I live.

I have found their industrial battery support technicians to be useless in discussing RE use of their batteries. They do not understand the RE charging profiles (bulk, absorb, float), and use the terms 'bulk' and 'absorb' differently than we do in the RE business.

You will get better info about Interstate's UL16 and UL16HC from US Battery's website than from Interstate's.

--vtMaps

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