What are the best batteries for the money?

blue

My brother wants to build a new solar system in Puerto Rico. I was wondering what type of batteries are the best. The last I heard 6 volt golf cart batteries are the best because they have thicker longer lasting plates.  He's is thinking about 25 hundred watt system at 24 volts. Is there a good brand name out there for lead acid batteries?

mcgivor

There may appear to be many brands of batteries but in reality the number is limited, well known premium brands will generally cost more, offer longer warranty with customer support, lower cost batteries sold under store labels are probably  manufactured by one or more companies and some names like "Interstate Batteries" are just marketers of batteries made by others, Johnson Controls in this example. The thickness of the plates will largely be reflected in the weight, buying premium for the first install may not be the best choice because often they fall due to overestimated expectations and lack of understanding, just an opinion of course.

Below is an excerpt from a website which may be of assistance. 

To identify the manufacturer, ask the dealer or check the battery's Material Safety Data Sheet (MSDS). The manufacturer's code number on the battery will also identify the manufacturer. For differentiating quality, features or warranty periods, battery manufacturers will sometimes have product lines within a trademark or brand, for example, Bronze, Silver, Gold, Platinum, Titanium, Premium, Heavy Duty, Commercial, Standard, Plus, Turbo, Calcium, Classic, Maintenance Free (MF), etc. They will also contract with other manufacturers to build and private label batteries to complete their product lines, for example, specialty batteries, that are not economically feasible to build themselves. Motorcycle batteries are listed in the Powersports starting classification and motive, traction, standby, stationary, solar, and Valve Regulated Lead-Acid (VRLA) AGM and Gel Cell. Sealed Lead-Acid (SLA) batteries are classified as deep cycle batterie

stmar

When we bought our place the sysytem was in place so I embarked on a learing curve. My battery experience: Golf cart 6 volt FLAs that the owner had wedged into an interior closet. Luckily, in hindsight, got hit by lightning and it brought out all kinds of weaknesses in the system. Replaced and repositioned the bank, bought 4 Lifeline 12 volt AGMS which I used for 10 years. They were still going strong but I figured they were near their end. After some research and experience I went with 4 Lifeline GPL16 6 volt 400ah AGMs and that was my battery journey so far. Lifelines are more expensive than most competitors but their specs are robust.

Dave Angelini

The absolute best battery you can get is the one that is locally sold and backed-up by a reliable local seller!

BB.

If this is his first time at solar... Golf Cart Batteries are a great training set. Pretty forgiving, and if he kills the first set (over discharging, too much loads with too few solar panels, forget and leave loads on during bad weather/kids visiting and leaving everything on, etc.), they are relatively cheap to replace (many of us have killed our first battery bank or two).

Measuring/understand his loads is important (as is having no shade/power lines/trees that prevent full sun from hitting the array).

If he wants to run a refrigerator, that is really the dividing line between a small and cheap system (something like 1,000 WH per day), and a medium size system that supplies ~3,300 Watt*Hours per day or more.

A 2,500 Watt system does not really tell us how big the battery bank. What is needed is the Watt*Hours per day energy usage to design the battery bank. And will he have a backup genset (for bad weather, if he needs more power for tools to repair his home, etc.)?

Doing paper/back of the envelope designs is cheap. Building out a system that does not meet his needs (or the parts don't work well together)--Expensive.

-Bill

blue

Thanks so much. That's a lot of information. I take it 6volt GC batteries are not necessarily better. I will have to get with him to decide how many WH per day he needs. My system has 15 hundred watts of solar and I have 8- 12 volt everlast dc29 max's, they are made by Johnson. maintenance free from Walmart running at 24 volts with a 2 year warranty. It says 114 ah each. I paid $99 each they weigh 65 lbs. I see a Lifeling gpl 31T 12 volt battery 105 ah weighing 69 lbs for $398 with a 1 year warranty. Which is the better deal?

blue

In protecting my batteries for longevity I calculate the amount of charge I have at night before I go to bed. If the voltage is 25 or higher I seem to be fine in the morning running above 24.2 or higher. I run a fridge and ceiling fan during the night. I have noticed at time it reads a little below 24.2 but when the fridge cuts off it will go back up to read 24.3 or so. It is my understanding that the best soc reading is under no load with no sun is that correct. 24.2 should be 50 percent which is as low as I want to go. Would someone weigh in on this for me? I do not use to much during the day and voltage usually runs up to 30 or 31.3 and moves into float for a while each day excluding full clouded days. I was told I might expect 8 years out of the batteries. 

westbranch

Do you check the Voltage of each battery. at 50% DOD you are using them heavily.. You don't want to have an unbalanced string...

blue

I check from time to time with a hydrometer. But the reading I am talking about comes from the epever 60 amp mppt controller. It states the battery voltage present, high, and low for the day. I thought I read a chart that approximated the life of batteries with the daily state of discharge. I believe it said if you don't go below 50% daily you could get 8 years.  What is your opinion of how low is safe?

blue

How do I prevent an unbalanced string?

softdown

Batteries will likely be warmish in Puerto Rico. Typical battery life is 4-8 years. In a warm environment, I'd expect closer to 3-6 years.

Warranties are nice but we all pay for the yahoo's who murder their batteries then cash in on the warranty. Plus warranties are not always backed. 

Pretty easy choice here. Golf cart batteries likely offer the biggest bang for the buck. Especially for the newbie.

mcgivor

blue said:

How do I prevent an unbalanced string?

This is the standard issue, must read web page which saves much explanation  
http://www.smartgauge.co.uk/batt_con.html

Estragon

> @blue said:
> How do I prevent an unbalanced string?

Wiring such that all battery resistances are equal, and checking the parallel connection from each battery/string periodically with a clamp-on DC (not AC) meter while charging in bulk.

With 8 x 12v batteries, you presumably have 4 pairs (series strings) in parallel, for ~450ah. Using GC 6v (~225ah) batteries, you would have 2 parallel strings of 4, for about the same capacity. Fewer strings in parallel is easier to keep balanced.

Also, with 12v, you have 6 cells x 8 batteries = 48 cells total. With 6v GC, you'd have 3 cells x 8 batteries = 24, half as many to check and water.

westbranch

if you detect a  bad cell (12V batt.) charge it separately  overnight with  a good charger  and then do a REFESHING  charge on the whole bank  (see Life Lines recommendations for max voltage for AGMs) .  NEVER do an EQ charge on AGMs! 

I set the ABSORB to the max for my aging AGM battery..

If you go back to FLA's then you would just charge up the bank till it gets to Float and then set it for an EQ. charge.  Please read the manual ans do a manual EQ under your watchful etes as you should monitor the temps and gassing of each cell.  Too hot ? TERMINATE the EQand t

Estragon

@blue said "check fron time to time with a hydrometer" so I assume flooded. The problem with using EQ to deal with a balance issue is the underlying issue remains. The EQ is hard on lower resistance strings to get high reststance strings fully charged.

BB.

From a energy view point, a 12 volt @ 110 AH battery is identical (in stored energy) to a 6 volt @ 220 AH battery:

• Energy (Watt*Hours) = Volts * Amp*Hours = 12 volts * 110 AH = 1,320 Watt*Hours
• Energy (Watt*Hours) = Volts * Amp*Hours = 6 volts * 220 AH = 1,320 Watt*Hours

However, if you wanted to store 2x that amount of energy, you would use 2x 12 volt @ 110 AH batteries in parallel, or 2x 6 volt @ 220 AH in series.

Why I like 2x 6 volt series configuration. You have 6 cells to check water levels on, and no balancing of current with parallel connections (and as you add more parallel connections, you really should use a fuse/breaker per parallel connection--More hardware and $$). Also it is very easy to see the health of each battery (6 volts across each battery). With 2x 12 volt batteries in parallel, both batteries have the same voltage and it is more difficult to do a quick sanity check on your bank.

Note that the 12 volt @ 110 AH and 6 volt @ 220 AH batteries are pretty much the same size and weight.

I like to suggest that ~2-3 parallel strings of batteries is the maximum I would aim for... Use larger AH batteries ( you can get 2 volt cells that are >>>1,000 AH). Fewer cells to check, fewer parallel strings, fewer electrical connections, easier to maintain:

https://www.solar-electric.com/marine-rv/batteries-and-accessories/deep-cycle-batteries.html?nav_battery_voltage=2+Volts

Temperature wise... Warm/hot batteries cut their life dramatically. The engineering equation is for every 10C (18F) increase in temperature, there is a factor of 1/2x less (aging) life (75F battery vs 93F, your 8 year bank would last ~4 years). So--If you can have batteries in a cooler/shaded room, or even in a cool basement--It can help a lot (proper ventilation and safety practices is important too).

-Bill

blue

Again thanks so much. What a great simple explaination for balancing. I have method 2. Method 3 looks easy and worthwhile to achieve. 2 more wires and two posts to attach to. Not sure where to find the post. Must be called a battery terminal post?

blue

Thanks I understand the 6 volt reasoning now. Had never heard of 2 volt batteries before.it would take 12 to reach 24 volts. Not sure of availability in pr. Shipping is expensive.

BB.

And that is the issue with batteries (particularly Lead Acid)--What is available and how much it costs at your location... Sometimes you have to make do with what you can get.

-Bill

Photowhit

blue said:

Thanks I understand the 6 volt reasoning now. Had never heard of 2 volt batteries before.it would take 12 to reach 24 volts. Not sure of availability in pr. Shipping is expensive.

In truth all lead acid battery/cells are roughly 2.1 volts. What is called a 6 volt or 12 volt 'battery' is actually a string of battery/cells each with it's own reservoir of electrolyte that must be checked independently of each other. The reason 6 volt 'batteries' have 3 caps and 12 volt 'batteries' have 6 caps.

MrM1

blue said:

Again thanks so much. What a great simple explaination for balancing. I have method 2. Method 3 looks easy and worthwhile to achieve. 2 more wires and two posts to attach to. Not sure where to find the post. Must be called a battery terminal post?

You might consider something like this.  Very robust.

https://smile.amazon.com/gp/product/B075XCLRZ4/ref=oh_aui_detailpage_o09_s00?ie=UTF8&psc=1

Estragon

> @blue said:
> Again thanks so much. What a great simple explaination for balancing. I have method 2. Method 3 looks easy and worthwhile to achieve. 2 more wires and two posts to attach to. Not sure where to find the post. Must be called a battery terminal post?
>
>

My "posts" (where the two equal length wires meet to parallel two strings of L16s) are just a bolt, washer, lock washer, and nut. It works fine for a couple of strings. With more than a couple, a flattened copper pipe with holes drilled could get the job done.

Estragon

6v GC batteries are commonly used for boat house banks. If your brother is near marinas, etc. in PR, there is likely to be a supplier who gets them in bulk.

softdown

MrM1 said:

blue said:

Again thanks so much. What a great simple explaination for balancing. I have method 2. Method 3 looks easy and worthwhile to achieve. 2 more wires and two posts to attach to. Not sure where to find the post. Must be called a battery terminal post?

You might consider something like this.  Very robust.

https://smile.amazon.com/gp/product/B075XCLRZ4/ref=oh_aui_detailpage_o09_s00?ie=UTF8&psc=1

"These hefty 4-post 3/8" studs busbars have 3 additional #8-32 screws for small connections,"  Is this really designed for ~4/0 cables? 

Whether or not we really need to use 4/0 is another topic. Even 2/0 is not far behind.

blue

Thanks I understand the 6 volt reasoning now. Had never heard of 2 volt batteries before.it would take 12 to reach 24 volts, not sure they co

blue

Thanks busbar is the word I was looking for. Anybody want to take on the 50% soc issue. How low do you go? How do you calculate where your at? Am I right about the best reading being at night with no load ?

MrM1

softdown said:

MrM1 said:

blue said:

Again thanks so much. What a great simple explaination for balancing. I have method 2. Method 3 looks easy and worthwhile to achieve. 2 more wires and two posts to attach to. Not sure where to find the post. Must be called a battery terminal post?

You might consider something like this.  Very robust.

https://smile.amazon.com/gp/product/B075XCLRZ4/ref=oh_aui_detailpage_o09_s00?ie=UTF8&psc=1

"These hefty 4-post 3/8" studs busbars have 3 additional #8-32 screws for small connections,"  Is this really designed for ~4/0 cables? 

Whether or not we really need to use 4/0 is another topic. Even 2/0 is not far behind.

I believe they would work. I have a pair.  I bought them at the start when I thought I might get 8 6v batteries in 2 strings for my 24v system.  I am also using 4/0 cable,  and even though I never used them, it appears there would not be a problem.  the voltage / amp spec of the busbar would be fine.