Quick battery quesion (battery rating)

[sipNgas]

Freightliner recently replaced 2 of my 4 deep cycle batteries with a different brand and slightly different rating. Not sure if that's an issue as I don't understand the rating system on batteries.

My original batteries were US Battery 1800 XC2. These appear to be rated at 208 Amp Hours (20 hour rate). The replacement batteries are NAPA 8144 rated at 225 amp hours (20 hour rate).

Is a "20 hour rate" a standard rating system to compare batteries? I noticed other ratings on the batteries (i.e. 120 mins @ 75 amps, etc.).

Can these two battery types/ratings be used together? The original batteries are 1 year old while the NAPAs are new.

Any info is appreciated!

[Mr_D]

If they are chassis (starting) batteries you need to look at the CCA not the amp hours over time.
You need a high discharge rate to start an engine. The CCA (Cold Cranking Amp) is the rating of that, the 20 hr rate would come into play if they were used for house batteries (low drain over a long time)
Our rig has 4 950 CCA no maintenance starting batteries. The house batteries are 4 12 V 8D AGM batteries.
Batteries are supposed to be replaced with the same type/size and age, but what you have will still work, just not as well. but you'll probably never notice the difference.

[TQ60]

On the surface the ah are more on the new which is better...but...

Google both batteries and get the datasheets for both.

Many use the 20 hour rate to get the highest number but in days past the 8 hour rating was commonly used.

Compare at 8 then 4 hour ratings using same end point voltage so you are using apples to apples comparison.

While you have the sheets read yhe one for your installed batteries 3 times then review your installed battery support system then read it again to determine where you need to measure voltages then measure your system voltages and determine if they meet the needs of your new batteries.

[sipNgas]

Thanks Mr D! I should have specified, it's the house batteries I'm referencing. And thanks for the info!!

Is it the "20 hour rate" that people post when they say their battery is, as an example, 125Ah? I've been reading quite a bit of battery postings and referring to a battery as xxx Ah seems to be the common terminology used. But is that the 20 hour rate or something completely different? Neither of my batteries have a specific Ah rating that I can find so I'm assuming (hate hate hate to assume) that the 20 hour rate is that number.

And a follow up question, if I have four 6v 208Ah (20 hour rate) batteries, 2 sets of 2 in series for a 12v system, does that mean I have a total of 416Ah?

So each set of 2 batteries in series adds up to 12v but the Ah remains the same. But for the Ah rating for the system, you add up the 2 parallel 12v battery pairs for a total of 416Ah. Voltage additive in series, current additive in parallel.

Am I way off on that or does it sound correct? Thanks for the help!

[sipNgas]

Originally Posted by TQ60

On the surface the ah are more on the new which is better...but...

Google both batteries and get the datasheets for both.

Many use the 20 hour rate to get the highest number but in days past the 8 hour rating was commonly used.

Compare at 8 then 4 hour ratings using same end point voltage so you are using apples to apples comparison.

Hi TQ, thanks for responding!

I found my answer at BatteryStuff Articles | Understanding Series and Parallel Battery Configurations

The 20 hour rate is definitely the Ah rating everyone is referencing. And 2 batteries in series retains the single battery Ah figure while adding the Ah figures for parallel connections gives me the total Ah available.

I'm trying to size up my batteries for a solar system and hate to assume anything. Thanks.