Batteries with different types of power ratings confusing

bgu1982 · July 2022

I bought three durecell 31 dcx marine/ deep cycle batteries and the power rating is different from other batteries I've had. Meaning my last batteries were 135ah. These new batteries don't rate it in ah's.

20 amp hour rate:100
Battery Electrolyte Composition:Acid
Battery End Type:Top Post
Battery Purpose:Deep Cycle
BCI Group Size:31
CCA at 0 degrees F:700
Freight Class:65
MCA at 32 degrees F:800
Minutes at 23 amps:205
Minutes at 25 amps:190
Polarity:Left Positive
Terminal Type:STUD/Post
Volts:1

Im having trouble comparing the two different batteries because the power ratings are different. I'd really like to know what the ah's is for the new durecell 31 dcx. Is posted the ratings it gave above. Thank you for any help

Photowhit · July 2022

bgu1982 said:

...rate it in ah's.
20 amp hour rate:100

Says right here...

They screw it up a little because Ad people don't get tech people to check their work.
Amp hours vary depending on the hours of discharge. Here's a chart of amp hour rates for a trojan battery;

Of course they could also be saying it can handle a 20 amp load for 100 minutes...
...but they do some of that farther down.

Personally do yourself a favor, if they allow returns if the plastic hasn't been removed...
...and you haven't removed the plastic terminal protectors. Return them and buy some golf cart batteries...

Typically, 'Marine' aren't true deep cycle batteries. Looks like you intend to have a bunch in parallel, a bad idea as they don't share load or charging evenly.

bgu1982 · July 2022

See that's what I mean. The top say 20 amp hour rate: 100

But farther down it says minutes at 23 amps:205
I don't understand what the actual capacity is. And I have three of them

I considered the golf cart batteries but the ah was double what the 12 v batteries are but two 6v batteries in series to make 12 v would equal about the same ah rating as two 12 v batteries but half the cost.

I have three of the durecell batteries connected in parallel with 6 inch long 2 awg wire interconnecting them. With the load and charging wire connected on opposite sides(pos-neg) I'm trying to figure out how much battery capacity I have. connections are tight.

bgu1982 · July 2022

That look ok?

Photowhit · July 2022

Lots to be discouraging about for me, I really don't want to be too discouraging. It should work for a while, shallow discarging will extend the life.

Things I will point out understanding it might help in the future;

Multiple strings create current sharing problems in charge and discharge cycles,
This site helps explain;
SmartGauge Electronics - Interconnecting multiple batteries to form one larger bank

Stacked connectors are always a bit difficult to keep tension through the stack. Holding your hand next to the or lightly touching them to see if they are heating up after a few minutes of heavy load, may indicate poor connection.
Things that can help is wiring the battery bank to a breaker with a bussbar to make your additional connections.
I think they also make terminal expansion things so you can do this at the battery terminal.

16016198jpg

Tinned copper like these would be best.

A flooded battery;
With these access points, and top starting battery mounts,

Would indicate this isn't designed as a true deep cycle battery.

If it's for weekend use you may be fine for a few years, if daily deep cycling could be as little as a single year. The good news is that this design is pretty much maintenance free!

FWIW - Looks like the batteries are also from different 'runs' with 2 different dates codes. Always nice to get them with the same date codes.

Hope I haven't been too discouraging! It's all a learning curve, we've all learned things as we go along.

BB. · July 2022

The marketing spec of "20 amp hour rate: 100" is not really the correct term.

Instead it is the 20 hour discharge rate and 100 AH capacity:

100 AH capacity / 20 hours = 5 Amps (for 20 hours from 100% to 0% state of charge)

For a home or cabin, we tend to use the 20 hour capacity as a good fit for how the batteries are used... Say 5 hours per evening, for 2x evenings (10 hours total) to 50% suggested planned discharge (10 Hours of "additional capacity = 20 hours).

For these ratings:

Minutes at 23 amps:205
Minutes at 25 amps:190

I would suggest reading these as (my guesses):

23 Amp discharge for 205 Minutes
205 minutes * 1/60 minutes per hour * 23 Amp discharge rate = 78.5 AH capacity (basically 3.4 hour discharge rate)
25 amp discharge for 190 minutes
190 minutes * 1/60 minutes per hour * 25 Amp discharge rate = 79.2 AH capacity (3.2 hour discharge rate)

As Photowhit posted (Trojan numbers)--The "faster" you discharge a lead acid battery, the lower "apparent" capacity they will have.

-Bill

bgu1982 · July 2022

So my old batteries on the lable said 135ah. These new batteries are bigger and have less capacity?. Because everybody seems to describe there battery capacity like 240ah. I just want to know what ah my battery bank is. If some says 240 ah battery capacity is that 240 hours at 1 amp?

I know I should have bought better batteries butm old batteries died quite suddenly and I have a refrigerator and stuff so if had little time to find the best deal and at $100 a battery I went for it. If they last a year then I'll just have to buy more. Next time I may go for the golf cart 6v batteries. Plus they are a secondary system I also have a ecoflow delta pro. So the marine/deep cycle batteries only usually get a shallow discharge daily.

bgu1982 · July 2022

Photowhit said:The good news is that this design is pretty much maintenance free.

Maintenance free? As in I don't have to check water levels ect?

mike_s · July 2022

For lead-acid, capacity is by far most often spec'd at a 20 h rate, unless specifically stated otherwise. So, a 240 Ah systems would provide 12 A for 20 hours. But, as already stated, those aren't "true" deep cycle batteries, they're a compromise between starting and deep-cycle. One clue is that in addition to Ah capacity, they spec CCA and MCA. That's common for "marine" batteries, which are also often used for RVs. They're fine if you want to run some lighting at night on an occasional basis. If you expect daily use, true deep cycle batteries will have a longer lifetime.

Photowhit · July 2022

bgu1982 said:

So my old batteries on the lable said 135ah. These new batteries are bigger and have less capacity?. Because everybody seems to describe there battery capacity like 240ah. I just want to know what ah my battery bank is. If some says 240 ah battery capacity is that 240 hours at 1 amp?

I can only go by what I see. A 12 volt 240 amp hour battery would likely weigh around 120-130 pounds.
I'm sure we could look for more info on these batteries, but the first line appears to state that they are 100 ah batteries.

Photowhit · July 2022

bgu1982 said:

Photowhit said:The good news is that this design is pretty much maintenance free.

Maintenance free? As in I don't have to check water levels ect?

Always good to check, but the recessed buttons to check would indicate that to me. More info in other thread.

BB. · July 2022

Lead Calcium does use little water when charged/floated at lower voltages (i.e., charging at 14.0-14.4 volts or so), and floated at 13.6-13.8 volts or so...

I had some "float chargers" that would still "boil" a battery electrolyte to below the plate tops inside of a year or so (car that was mostly sitting in garage, RV in storage). So checking electrolyte levels every few months would not be a bad idea--At least until you understand the "water usage" (or not). And using a hydrometer to measure Specific Gravity is a good method to ensure battery/cells state of charge.

-Bill

Batteries with different types of power ratings confusing

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