[solarEVstudent]

So this is not a car but it is the same concept. I am working on a solar powered boat for a competition and am looking at batteries. We are limited to 100 lbs of lead acid batteries so i am trying to get the most power for the weight. I was wondering what the difference between a cheap battery and a more expensive battery is? For example the 35 amp hour Mighty Max battery(a cheap Walmart brand), https://www.mightymaxbattery.com/p3421769/ml35-12-12-volt-35-ah-sla-battery.html, weights 23 lbs and is only around $65. The Enersys Genesis G26EP has 28 Ah, http://www.enersys.com/WorkArea/DownloadAsset.aspx?id=492, and is over 2 times more expensive but appears to have less Ah/capacity and weighs about the same. Why is this? I assume the enersys is a better battery but it does not appear so.

Some more information is that I am trying to chose batteries (24 volt configuration) to run a 2 hour endurance race and then a pack for a 300 meter sprint race (36 volt configuration).

 

[john61ct]

Are you **required** to use lead, no lithium allowed?

Thin-plate 'starters' will be lighter than deep-cycle, usually spending more money on lead is for longevity, which you don't care about.

 

[solarEVstudent]

Are you **required** to use lead, no lithium allowed?

Thin-plate 'starters' will be lighter than deep-cycle, usually spending more money on lead is for longevity, which you don't care about.

That is correct we are required per competition rules to use lead acid batteries, no more than 36 volts, and under 100 lbs.

 

[Duncan]

The batteries that you have referenced have thick plates - and will be heavier for the power output and the energy stored
BUT they will last longer

For your application "lasts longer is worthless" - you need to look at thin plate "starter" batteries
They will be cheaper and lighter

 

[Sunking]

With Pb batteries (lead acid) there are 3 types out there..

SLI (starting-lighting-ignition) are typically Lead Calcium alloy made with very thin sponge like textured plates to maximize surface area which reduces the battery Internal Resistance. The plates DO NOT extend to the bottom of the jar to allow space for corrosion and debris to settle in the bottom preventing shorted out plate. SLI batteries are made to deliver very high short burst of currents to crank and engine, and then recharge very quickly. They should not be used for cycle applications. If forced into cycle service they will be dead after 50 to 100 cycles. Less than a year. With each cycle you shed plate material and thin plates do not have much material to spare. SLI batteries are only specified with CA, CCA, and MCA. They will not have an Amp Hour rating.

Deep Cycle batteries typically use Lead Antimony plates. The plates are very thick, heavy, and fill the jar. They are made to be deep cycled. Maximum life is obtained if you limit discharge to 50% DOD. The thick heavy plates allow for hundreds up to a few thousand cycles. It is the thick heavy plates and Lead Antimony that give them deep cycle ability. A true deep cycle battery will NOT have any CA, CCA, or MCA spec because of their higher internal resistance does not allow high amounts of current to be delivered without severe voltage drop. You will only see a Amp Hour spec and maybe a Reserve Capacity (RC) specified in minutes @ 25 amps.

Hybrid batteries try to be both SLI and Deep Cycle. There plates can be either Lead Calcium or Lead Antimony, or pure lead. There plates are not as heavy and thick as Deep Cycle, but thicker and heavier than SLI. Hybrids have all kinds of catch marketing names like Golf Cart Batteries, RV Batteries, Leisure Batteries, Marine Battery, Trolling Motor Battery and the list goes on. They can deliver fairly high amounts of current required to start an engine, but not as much as SLI batteries. They can be cycled but do not have the cycle life of a true Deep Cycle battery. The dead giveaway you are looking at a Hybrid battery is they will have both CCA, CA, and MCA ratings plus Amp Hour and RC ratings.

So back to your question. If AH ratings are equal, but one battery is heavier then the other, is because it has more lead in it with thicker and heavier plates. The heavy one will have more cycles and cost more. You get what you pay for.

 

[Duncan]

Hi Sunking
For this application 50 to 100 cycles would probably do!

I can't remember from the USA but in the UK and here in NZ starter batteries ARE sold in Amp hours

For this starter batteries are probably the way to go

 

[john61ct]

Hybrids have all kinds of catch marketing names like Golf Cart Batteries, RV Batteries, Leisure Batteries, Marine Battery, Trolling Motor Battery and the list goes on.

IMO many GC cells, both in usage and form factor, meet true deep cycling standards, and at least by reputable actual manufacturers are accurately labeled and cycling lifetime vs DoD stats can be compared to their other lines.

Of course starter batteries for fossil fuel golf carts are just starters.

 

[Sunking]

IMO many GC cells, both in usage and form factor, meet true deep cycling standards, and at least by reputable actual manufacturers are accurately labeled and cycling lifetime vs DoD stats can be compared to their other lines.

Don't kid yourself. Trojan Battery is one of the largest, oldest, and most reputable battery manufactures out there. The T-105 is well known as the best Golf Cart battery in the world. Trojan also makes a T-105RE deep cycle battery. RE = Renewable Energy. Same form factor as the T-105, but if you look at the specs the RE has 5 pounds more lead in them and cost more. They cannot be used in a golf cart or EV as that will void the warranty. Noir would you want to use them in a Golf Cart or EV because they cannot deliver the very high currents a GC and EV demand in acceleration.

The RE carries a longer warranty and significant longer cycle life. Additionally the Trojan famous L16 line-up (floor machine battery) also come in a RE lineup.

 

[john61ct]

Well there isn't really a black and white line here, and note I am coming from a House bank POV, not EV. And of course many golf car's use fossil fuel, I'm not talking about Starters or "dual use" rated for cranking.

Obviously the Sam's Club (also Batteries+) Deka/East Penn GC2 for $180 a pair 12V 215AH isn't as GOOD as a Trojan, but it's heaps better than anything at Walmart.

Someone who swears by Rolls/Surette may well sneer at a Trojan. RE is better sure, "more deep cycle" than the industrial scrubber line, but that doesn't IMO put the latter in the same category as a G27 "marine" from big box retail.

In fact I'd like to hear about a **better VALUE** true deep cycle than that Sam's GC2, for an RV or boating user who KNOWS he's going to have to abuse the bank, often goes below 50%, no room for more cells, hot engine compartment, rarely gets to 100%. . .

A cheaper pseudo DC G31 from Walmart will get murdered even quicker, but going upmarket is likely throwing scarce build money away.

For me personally, a good trusted manufacturer, and anything believably rated over 500 50% cycles, qualifies as "true deep cycle", it's just that there is a bottom tier as well as the top-shelf and middle ranges, just like any market niche.

I'm not sure if Maine Sail would agree with me where to draw that line, but I think his rant here http://www.pbase.com/mainecruising/deep_cycle_battery makes some good distinctions.

You are of course free to draw **your** line wherever you like.

 

[Sunking]

Someone who swears by Rolls/Surette may well sneer at a Trojan. RE is better sure, "more deep cycle" than the industrial scrubber line

Hold on there I like and spec both, plus a host of others. It is application specific. Both Trojan and Rolls have entry level, mid level, and high end level batteries. When you sort them out, they are pretty equal except when you get to the High End. Trojan High End line is Industrial line up and Rolls is series 5000. The Trojan IND series is the only battery that holds up to the rigors of IEC 61427 test protocol backed with an 8 year warranty. No Lithium battery can stand up to that standard, and no other PB manufactures dare to be tested to 61427 by an independent lab.

In fact I'd like to hear about a **better VALUE** true deep cycle than that Sam's GC2, for an RV or boating user who KNOWS he's going to have to abuse the bank, often goes below 50%, no room for more cells, hot engine compartment, rarely gets to 100%. . .

OK that is easy. That would be US Battery, Trojans competition. They make a good battery that is easier on the wallet. Sam' Wallyworld and other store brands are mostly made by Interstate Battery.

Thing is you are going to get exactly what you pay for. A great example is the T-105 vs T-105RE. The T-105 cost roughly $120 to $140 depending on location, and the T-105RE cost $145 to $170. Now one might think since they are are exactly the same specs at first glance and the T-105 is a better value is dead ass wrong. The T-105 is a 2-year battery, and the T-105RE is a 5-year battery. Now you might think you are just paying extra for the warranty, but you are not. The RE has 10% more lead and Trojans T2 Carbon Plate Technology which makes them better suited for PSOC operation.

Comparing a Store brand GC battery to a T-105 is like comparing a LFP Chi-Com POS Calb or Winston battery to Kokam or A123. There is no comparison. You get what you pay for.

 

[riba2233]

Hi Sunking
For this application 50 to 100 cycles would probably do!

I can't remember from the USA but in the UK and here in NZ starter batteries ARE sold in Amp hours

For this starter batteries are probably the way to go

Yep, in europe they also have Ah ratings.

 

[jerronem4]

I would also choose a battery that has thin plates to save some weight, and it is less pricey.