two batteries

[brian_bp]

... the Trojan T-105. For comparison purposes, their 200AH is about double the 105AH you get from Group 27 sized deep cycles

That's 200AH at 12V from two T-105, versus 105AH at 12V from one Group 27. Comparing apples to apples, a pair of T-105 in series have about the same total capacity at the same system voltage as a pair of Group 27 (e.g. Trojan 27TMH). The 27MTH set is about 5% lighter than the T-105 set; it seems reasonable to assume that the construction is similar (the Trojan 27TMH may not be the same as the department store's group 27 deep cycle), but I don't know about details such as space over the plates. I assume that's the comparison Don intended.

[48Rob]

I'm confused here

I understand the two battery setup well, as I have two 6 volt T-105's powering my trailer.
The confusing part is the 200 Amp hour number being tossed around?

If a T-105 is 105 Amp hours at 6 Volts, two of them (added together)would be 210 Amp hours...yet 200 is quoted?

However, we're connecting two 6 volt batteries to provide 12 Volts.
Does that not make 105 Amp hours at 12 Volts?

Rob

[Trackstriper]

Rob,

Your T-105's are rated about 225AH (20 hour rating) so Brian is correct on the total. You may be thinking that yours are 105AH due to the model number. I believe most of the standard 6V golf cart batteries are in the 200-225AH range.

[wlooper89]

Rob,

Your T-105's are rated about 225AH (20 hour rating) so Brian is correct on the total. You may be thinking that yours are 105AH due to the model number. I believe most of the standard 6V golf cart batteries are in the 200-225AH range.

This sounds correct to me. If a golf cart battery is rated for 200 AH at six volts then two of them in series should put out 200 AH at twelve volts.

Bill

[48Rob]

I understand now

Thanks!

Rob


...seems the boy that I bought the batteries from (at a battery specialty shop...) needs a little more training in the advice department...

[Alphacarina]

it seems reasonable to assume that the construction is similar (the Trojan 27TMH may not be the same as the department store's group 27 deep cycle), but I don't know about details such as space over the plates. I assume that's the comparison Don intended.

No, the basic construction is very different. Group 24 and 27 batteries were an exercise in trying to cram the maximum number of amp hours into the absolute smallest possible package and numerous compromises they made to that end greatly affects their lifespan - They wanted something you could easily carry down the dock, throw in the trunk and take hoome to recharge before your next fishing expedition. If you want a long life deep cycle battery, a group 27 is about the worst choice you could make. Some are better than others of course, but none of them are anywhere near as good as they could have been had they made the package larger

Most batteries die when the plates shed enough material that it shorts out the bottom of the battery cells. Since a Golf Cart battery was designed with only one thing in mind (that being the longest possible life, no matter the weight or the package size) they raised the cells another 1/2 to 34 inch off the bottom of the battery case (which makes it able to shed lots more plate material before shorting out anything) and then they also added another 1/2 to 3/4 inch at the top, so that the battery can lose a good deal of water before exposing the plates. Both of these improvements make deep cycles (below 50% of capacity) possible with less harm to the battery's life and they also make the battery a better performer when used on a vehicle which bounces around a lot and may stop in some very unlevel positions

A good golf cart battery will outlast a good group 27 deep cycle battery 2 to 1 even with less maintenance . . . . probably more than 2 to 1 if the 27's are connected in permanant parallel. Group 31 batteries are about in the middle - Fewer compromises were made in their construction than with the group 24 and 27 batteries, but they still fall well short of the venerable golf cart battery. Golf Cart batteries are an excellent choice in boats and RV's and any type of electric vehicle. They also make an 8 volt version which is very popular with the EV crowd. Slightly fewer amps than the 6 volt ones but every bit as robust in their contruction and it only takes 16 of them to make a 120 volt pack, where you would need 20 of the 6 volt version

I worked for about 20 years on Air Force equipment (ILS, TACAN, VOR and weather equipment) which use battery backup to run on when the power goes out and then another 15 years designing and installing battery systems in boats . . . . some of them very large boats with up to 1000AH battery banks. I've studied deep cycle batteries for most of my life. I'm a frugal guy who always likes to get his money's worth and nothing burns me up more than having to replace a battery which is only 2 or 3 years old. I've had banks of batteries in boats that I installed last 6 or 7 years . . . . they they come back to me when they need another set because I try to get them the best value for their dollar

Don

[brian_bp]

I was really just trying to clarify that the series/parallel comparision was between two T-105 (200+ A-h @ 2x6V) and two 27TMH or similar (2x105 A-h @ 12V)... not a comparison of a two-battery set with a single battery. Hopefully we have that straight now.

it seems reasonable to assume that the construction is similar (the Trojan 27TMH may not be the same as the department store's group 27 deep cycle), but I don't know about details such as space over the plates. I assume that's the comparison Don intended.

No, the basic construction is very different...

That's strange, since the pair of T-105 and the pair of 27TMH have virtually the same total volume and weight. There's no indication in the specs that a high A-h capacity has been crammed into one more so than into the other. If the Trojan 27TMH package is not filled with what it should be, what's in there... rocks?


The BCI group specifications are just sizes, not construction specs, so of course other models of Group 27 (and Group 24) sized batteries may be unsuitably constructed. As an obvious example, there are many Group 27 starting batteries, which would have great cranking current capacity (of no use in a trailer), lower A-h capacity, and poor durability in deep-discharge use. Even among deep-cycles, cheap consumer-grade Group 27 units should be common, while there would be little reason for anyone to make similarly cheap batteries in the GC-2 (golf cart, including T-105) size.

Don, are you comparing the T-105's to specifically the Trojan 27TMH model, or to other brands and types which happen to be Group 27 sized and deep-cycle rated? If a particular size and format suit someone's needs, then it would be good to know which specific brands and models are well-constructed.

[Alphacarina]

The BCI group specifications are just sizes, not construction specs, so of course other models of Group 27 (and Group 24) sized batteries may be unsuitably constructed

I thought so too . . . . but it appears you can make batteries all sorts of different sizes and still call them 'Group 27 batteries' if you stick some other alpha-numeric characters on the end of your '27' - This is sure news to me because I've always considered all batteries from any stated group to be of the same size . . . . why else categorize them in 'groups?'

Don, are you comparing the T-105's to specifically the Trojan 27TMH model, or to other brands and types which happen to be Group 27 sized and deep-cycle rated?

No - I wasn't. I was speaking of standard sized Group 27 deep cycle batteries . . . . and not this new oversized entry from Trojan. While Trojan is my favorite supplier of flooded wet cells, I've not kept up with their offerings in the Group 24 or 27 sizes because they just don't represent a good 'bang for the buck' for a boat or an EV - Comparing a pair ot the Trojans at $330 each with a pair of Golf Cart batteries would be a non-starter for anyone interested in the most power (or life) for the money - $660 for 230AH is just . . . . ridiculous. I had 4 Trojan L16's on my sailboat for that kind of money and they are almost 400AH per pair - 800AH for my double bank for that kind of coin . . . . . and they lasted 8 full years. I'm sure prices have gone up since I bought those . . . . but $660 for 230AH is just crazy money when compared to Golf Cart batteries

http://www.solardyne.com/trojdeepcycb1.html

A standard Group 27 is 12 inches by 6.5 inches by 9 inches and they usually are rated at 95 to 105 AH. The Trojan 27TMH is a full 20% larger than any standard group 27 and is rated at 115 AH - The highest rating I've ever seen on any 27. They made it bigger by 20% while only raising the AH capacity by 10% so it is possible they have left some additional room at the bottom of the case so it won't sulpahate quite as fast as a standard 27 does - For $330, I would certainly hope so

You can buy 2 Golf Cart batteries for much less than $330 and have twice the power and certainly a longer life. Unless you have a vehicle specifically designed for Group 27 batteries, I wouldn't even look twice if I was going for a $$$ to AH to lifespan comparison . . . . you're never going to win that contest with any Group m27, plus the 20% larger Trojan might not even fit where a 27 is supposed to in your vehicle

Don

[brian_bp]

The BCI group specifications are just sizes...

I thought so too . . . . but it appears you can make batteries all sorts of different sizes and still call them 'Group 27 batteries' if you stick some other alpha-numeric characters on the end of your '27' - This is sure news to me because I've always considered all batteries from any stated group to be of the same size . . . . why else categorize them in 'groups?'

I did notice some variance in size within a BCI group. I assume that the group sizing is "nominal", allowing some variation and only a guide for interchangeability in mounting. This issue shows up in cars, where some brands/models of a particular BCI group fit a particular car, but not all.

Don, are you comparing the T-105's to specifically the Trojan 27TMH model, or to other brands and types which happen to be Group 27 sized and deep-cycle rated?

No - I wasn't. I was speaking of standard sized Group 27 deep cycle batteries . . . . and not this new oversized entry from Trojan. While Trojan is my favorite supplier of flooded wet cells, I've not kept up with their offerings in the Group 24 or 27 sizes because they just don't represent a good 'bang for the buck' for a boat or an EV - Comparing a pair ot the Trojans at $330 each with a pair of Golf Cart batteries would be a non-starter for anyone interested in the most power (or life) for the money - $660 for 230AH is just . . . . ridiculous. I had 4 Trojan L16's on my sailboat for that kind of money and they are almost 400AH per pair - 800AH for my double bank for that kind of coin . . . . . and they lasted 8 full years. I'm sure prices have gone up since I bought those . . . . but $660 for 230AH is just crazy money when compared to Golf Cart batteries

http://www.solardyne.com/trojdeepcycb1.html

A standard Group 27 is 12 inches by 6.5 inches by 9 inches and they usually are rated at 95 to 105 AH. The Trojan 27TMH is a full 20% larger than any standard group 27 and is rated at 115 AH - The highest rating I've ever seen on any 27. They made it bigger by 20% while only raising the AH capacity by 10% so it is possible they have left some additional room at the bottom of the case so it won't sulpahate quite as fast as a standard 27 does - For $330, I would certainly hope so

You can buy 2 Golf Cart batteries for much less than $330 and have twice the power and certainly a longer life. Unless you have a vehicle specifically designed for Group 27 batteries, I wouldn't even look twice if I was going for a $$$ to AH to lifespan comparison . . . . you're never going to win that contest with any Group 27, plus the 20% larger Trojan might not even fit where a 27 is supposed to in your vehicle

Don

Thanks for the details, Don. The golf cart units seem to be popular because they are cost-effective, and that's certainly an important consideration.

So I think the summary is that the BCI group itself doesn't matter; it is total battery capacity and construction which matter. While the right characteristics can be had in many sizes, good choices are available and reasonably priced in the golf cart sizes (GC2), while available Group 24 and Group 27 units are more likely to be less suitably constructed.

[brian_bp]

The BCI group specifications are just sizes...

I thought so too . . . . but it appears you can make batteries all sorts of different sizes and still call them 'Group 27 batteries' if you stick some other alpha-numeric characters on the end of your '27'...

I didn't interpret the letters on the end of a Trojan model spec (e.g. the "TMH" of "27TMH") as some sort of variation on the BCI size; instead, I assume that it is simply the model designation, which sometimes happens to include the group size.

There are almost a dozen Group 27-sized batteries in the Trojan list which I downloaded from them, and where all say simply "27" in the "BCI Group Size" column, the fuller model designation is labeled "Type". The categories of product distingished by these model designations include

1. "deep cycle" [27TMX and 27TMH]
2. "valve regulated (gel)" [SG-90]
3. "Trojan marine/RV deep cycle" [SCS200]
4. "Trojan marine/RV starting" [27SM-100]
5. "Trojan marine/RV dual purpose" [27TMS and 27TM]
6. "Trojan marine/RV AGM dual purpose" [27-AGM]
7. "Minn Kota by Trojan deep cycle" [MK27DC]
8. "Minn Kota by Trojan dual-purpose starting/deep cycle" [MK27DP]
9. "Minn Kota by Trojan valve-regulated (AGM) dual-purpose starting/deep cycle" [MK27AGM]

(and that's just one manufacturer!)

All of the flooded-cell styles in Group 27 are 12 3/4" (324mm) by 6 3/4" (171mm) by 9 3/4" (248mm), but gel and AGM dimensions are a little different... and yes, every variation is bigger in at least one dimension than Don's standard of 12 inches by 6.5 inches by 9 inches... but then, when I searched web sites I found only another set of dimensions for Group 27 ( 12 1/16 x 6 13/16 x 8 7/8 ).

Where there are two models of the same general type and BCI size, in each case (e.g. 27TMX and 27TMH) the spec sheet shows them with the same case dimensions but different weights and capacities, so the variation is in the contents, not the case.

I guess all I'm saying is that the group number isn't much of a battery description, and isn't even a precise battery size description. Specific model selections such as Don's seem to me to be more useful information than guessing anything based solely on BCI group.

[wlooper89]

I agree that battery group size is not that useful for little trailer purposes. We are not always constrained by battery dimensions as might be the case for a car or other vehicle. I would rather think in terms of ampere hours and qualities such as whether it is deep-cycle and AGM construction. Then look at the physical dimensions and weight to see if it (or they) will fit.

Bill

[jamesm]

I have two of these..GPL 4CT batteries (2-6 volt AGM batteries) in my tounge box with a dedicated charger. Plus I am going to hook up my TV to charge the batteries as I drive. I'll get a pic tomorrow as its to late now. I have used the batteries only twice for weekend camping. They have lasted all weekend then when I put the digital volt meter on them it shows a full charge. I have a inverter that I use to run my laptop that I use to watch DVDs and I run lights. So not a lot of draw...but plenty of reserve to last a long time.






Here is a link to the specs on the batteries I use. http://www.lifelinebatteries.com/rvflyer.php?id=14

Here is the link to the charger I use.

I thought it would be helpful to see how the dual batteries can be set up.http://vdcelectronics.com/batteryminder_12248.htm