House batteries replacement

[Chance]

Originally Posted by jtyphoid

Is it possible that 6V batteries having half as many, larger cells than 12V batteries of equivalent case size allows for a cell design that tolerates deep discharge better? I'm wondering if this is why golf carts generally use banks of 6V batteries instead of 12V batteries.

I believe the reason for 6-Volt is probably much simpler. A typical 48V golf cart carries around 500 pounds of batteries, so 8 X 6-Volt all in series places each battery size in range of a Trojan T-105 at about +/- 62 pounds.

If you went with 12-Volt batteries, they’d have to be around 125 pounds each (which is a bear to lift) or you’d have to go with 2 strings of 4 X 12-Volt, which adds extra wiring and battery costs.

Some retrofit as well as new golf carts that go with lithium batteries have 4 X 12-Volt batteries in series. But we know lithium weighs a lot less (specific energy density is much higher).



By the way, I just learned that some battery manufacturers are starting to make smaller-size 48V lithium batteries that can be connected in parallel in large numbers as required to meet stored energy needs. I’ve been very interested in 48V for RVs thinking that’s the future, and having 48V individual batteries would not only add redundancy (versus 4 X 12V in series) but also makes it easier to expand battery bank capacity. And the combined peak current capacity seems to be a bit higher too because the built-in BMS doesn’t limit current as much.

[Beau388]

Originally Posted by jtyphoid

Is it possible that 6V batteries having half as many, larger cells than 12V batteries of equivalent case size allows for a cell design that tolerates deep discharge better? I'm wondering if this is why golf carts generally use banks of 6V batteries instead of 12V batteries.

Golf carts use group GC-2 6 volt flooded lead acid batteries because CG-2 is the cheapest deep cycle battery made (based on weight/amp-hr). 36 volt golf carts use 6 of them and the cheep (relatively) 48 volt ones use 8 of them. The more expensive golf carts use the 4 group 31 AGM deep cycle batteries and the really expensive golf carts ($15,000) use 4 100 amp-hour lithium iron phosphate batteries. The chemistry is the same for all lead acid batteries, so the more lead per dollar in deep cycle is what you want. For example - two 6 volt 68 lb 6 batteries (225 am-hr each) is almost equal to two 66 lb 12 volt batteries (105 amp-hr each).

[16ACE27]

The 8 volt golf cart batteries are feeling shunned.

[jtyphoid]

Originally Posted by Beau388

Golf carts use group GC-2 6 volt flooded lead acid batteries because CG-2 is the cheapest deep cycle battery made (based on weight/amp-hr). 36 volt golf carts use 6 of them and the cheep (relatively) 48 volt ones use 8 of them. The more expensive golf carts use the 4 group 31 AGM deep cycle batteries and the really expensive golf carts ($15,000) use 4 100 amp-hour lithium iron phosphate batteries. The chemistry is the same for all lead acid batteries, so the more lead per dollar in deep cycle is what you want. For example - two 6 volt 68 lb 6 batteries (225 am-hr each) is almost equal to two 66 lb 12 volt batteries (105 amp-hr each).

I understand that the chemistry is the same, but I'm wondering if design considerations like plate thickness, spacing between plates, free space beneath plates for sloughing, etc., make it easier to design for deep cycling if the individual cells are bigger. Some things scale up or down in size better than others.

[ellenov]

Originally Posted by ducksface

I don't want to turn this into a religious discussion of 6v vs 12v.

Here's the stance:
I already own TWELVE six volt batteries.
I have done the mockup battery from cardboard. It's in the thread in my signature.
I have found a place to easily put four of them in a spot you can throw a rock and hit and remove in about five minutes. I have already built a place to put four more for a total eight. Pictures are in my signature thread.

I've done the research, weighed the benefits, put in the time.

The six volt thing is a pretty basic hoax. It didn't used to be a hoax. Before there was anything but wet cells it was a fine path to take if you didn't have room for one large 12v but could find two spots for two smaller six volt. It was the only reason then, it's the only reason now.

The six volt myth has been dispelled by people smarter than I.
The 'don't set a battery on concrete' myth hasn't been a fact since the late sixties when they quit making batteries with tar bodies.
The 'magic' required for electricity to get through the plastic bodies now used is not from this dimension. Once said out loud, it makes sense. I use this as sense spoken out loud.

It's disputed.
I have $1,800 of six volts about to go into my greenhouse as a solar power and heat bank instead of into the rv.

Buying one or two lithium type batteries is much more sensical now. They're twice the draw(the reason to have 2 six volt batteries) in the same space as a 12v wet cell(the six volts take up twice the space)

Just thoughts from someone not only with the resources, but someone who already owns the batteries and has the fabrication skills.

(I have those 6v batteries because I got rid of two golf carts but kept the new/newish batteries and monster sized battery cables.)

I was wrong about putting in the six volts just because I had them. They add no value over a same amperage 12v except you can stash pairs in a smaller space each instead of needing a big space for the bigger 12v. For instance one 6v can go over each wheel well instead of a 2xbigger 12v over one wheel well.
There is no other value to them other than multiple small spaces being utilized.

A cell is a cell is a cell is a cell. That's the bottom line. There is no 6v cell. There is no 12v cell. They are called cells because they are groupings of 1.5v(+-ish) cells into battery. A 6v has the same cells as a 12v but one has twice as many of the same cells, the same size cells, the same voltage cells, just packaged as twice as big. There are percentage differences of far less than 3 percent in a laboratory setting. An rv is not a laboratory setting.

So do it or don't, it adds no value and deletes no rv level value except utilization of space.

From my research 6 volt golf cart vs 12 volt are not apples to apples. There are a lot more plates in a 6 volt than a 12 volt and plates mean energy. Two 6 volts are equal to four 12 volts because of their increased plates. Our two 12 volts did not perform as well as the two 6 volts we have connected to each other.

[Chance]

Originally Posted by jtyphoid

I understand that the chemistry is the same, but I'm wondering if design considerations like plate thickness, spacing between plates, free space beneath plates for sloughing, etc., make it easier to design for deep cycling if the individual cells are bigger. Some things scale up or down in size better than others.

Your assumption is indeed valid, but it makes very little difference.

I’ve compared the stored energy on a per-pound basis for various batteries within a model (so as to be otherwise apples to apples) and the difference is usually a few percent at most. You can also see what you’re talking about when comparing the industrial sizes of say Trojan batteries where the cell size can vary a lot. Making a 6-Volt battery twice as large mostly doubles its capacity. Same for a 12-Volt. The kWh capacity per pound is fairly a flat line. There’s a little variation, but not enough for me to worry about.

[Chance]

Originally Posted by ellenov

From my research 6 volt golf cart vs 12 volt are not apples to apples. There are a lot more plates in a 6 volt than a 12 volt and plates mean energy. Two 6 volts are equal to four 12 volts because of their increased plates. Our two 12 volts did not perform as well as the two 6 volts we have connected to each other.

I’m certain you’re wrong if comparing similar batteries. Please show specs of the 6V and 12V batteries you keep referring to where two 6V equals four 12V.

I don’t mean to argue with you, but misinformation should be questioned to help others. And if you’re right, we’ll all learn a valuable lesson.

[Beau388]

Golf carts have unique demands of electrical power - First they must be rugged - (not all carts stay on the path), Second they must be able to deliver 200 amps (at 48 volts) for at least 5 minutes. Lastly, they must be rechargeable in 8 hours or less and stand up to at least 400 discharges (a years usage). All this dictates the batteries construction plate thickness, separation and depth of individual cell. There are several GC sizes and voltages with the GC-2 being the old standard. That said not all deep cycle batteries as suitable for a golf cart. Textron (E-Z-GO) says the have about 80,000 golf carts at 1,350 golf courses. 6 or 8 batteries per cart is 480,000 to 640,000 per year. Here at my retirement village, the electric golf cart is the primary transportation for those of us in independent living. There are 242 houses and nearly every house has a golf cart, from the lowly TXT to the Express Elite. One of my neighbors has a 2019 E-Z-GO Express S4 Elite with fiber glass enclosure with sliding doors, leather seats, turn signals, horn, surround sound digital FM and Sirius-xm, windshield wiper, electric heat and a huge under dash squirrel cage fan. Of course there are an assortment of Club-Car and Yamaha carts.

[16ACE27]

Originally Posted by ellenov

From my research 6 volt golf cart vs 12 volt are not apples to apples. There are a lot more plates in a 6 volt than a 12 volt and plates mean energy. Two 6 volts are equal to four 12 volts because of their increased plates. Our two 12 volts did not perform as well as the two 6 volts we have connected to each other.

The number of plates PER CELL is higher in a 6 volt battery, but the total number of plates in an equal size 12 V Vs 6 V battery are equal, so the total energy each battery stores is equal.

Like Chance, waiting for your documentation to the contrary.

[Wolf8U]

I wish I had time to really research, all things batteries, but I'm still at work trying to get the printer going again for shields and mask.

My batteries are seal wet, 12 volt, 4 in all, and opened the compartment yesterday and it sounded like meat sizzling in a pan. So I know they need replacement. I always hear of stinging 6 volt batteries to make a 12 volt, but I don't recall anyone talking about the same with 12 volt. This was bought used last year by us 2016 Hurricane 34F 1800 inverter, So we're thinking of just updating to lithium and figure out how to set up for solar in the next year or two. 50 amp rig.

So now after the rambling, how would you all proceed?

Thank you in advance,
Mike

[cmills1334]

Originally Posted by Carlmatt

I increased the battery size to 31series batteries and added a third battery in the shoe box located to the right of the battery box. It helps, but it is not perfect. I still run out of battery capasity. The residential fridge is the problem- it sucks a lot of energy.

Does your fridge “ make a Clunk Noise when starting while only using battery power”? Mine does.
What model of Inverter do you have? Call me at 303-884-5884. CARL

have a 31w did the same with 3 12volt and mine makes a clunk too