Flooded cell 12v battery rating label numbers

noteven · February 3, 2017

Need a hand deciphering battery capacity. My new to me rig has 2 new 12v flooded cell batteries that were supplied by the seller. My other rigs have had 2x T105 6v batteries in series - I am a 12v battery newbie.

I think they may be 200 amp hour batteries but I don't know what the labels mean. The battery labels have these numbers and words:

Part: DC27 - I think is Deep Cycle Group 27?

Rating (CA): 715

Rating(CCA): 575

Rating (RC): 200

What is my safe useable amp hours from these 2 batteries?

Thanks

Lou Schneider · February 3, 2017

"Reserve Capacity (RC) is the number of minutes a fully charged battery at 80 o F (26.7 o C) is discharged at 25 amps before the voltage falls below 10.5 volts. To convert Reserve Capacity (RC) to Ampere-Hours at the 25 amp rate, multiple RC by .4167"

200 x .4167 is 83.74 amp-hours. Call it 85 amp-hours.

Note this is an approximation because amp-hours are measured at the rate it takes to discharge the battery over a 20 hour period while RC specifies a fixed 25 amp discharge. For an 85 amp-hour battery the C/20 rate is 4.25 amps.

https://www.pacificpowerbatteries.com/aboutbatts/deep%20cycle%20battery%20faq/dcfaq4.html

noteven · February 3, 2017

Thank you Lou

Yarome · February 5, 2017

Lou is correct. If this is a new rig, I would try and see if your dealer would take those back and give you a credit toward an upgrade or toward other merchandise (ie., vent covers, hoses, etc). They sound like (with those stats) standard automotive type starter batteries and very ill suited for an RV.

Apples and oranges to the T105's you're used to.

If the dealer won't take them back for some type of compensation, personally, I would just use them for core exchange credit and pick up a couple of golf cart 6v batteries from your local costco or sam's club. Still not quite your T105's, but a cost effective alternative if you don't do much dry camping.

noteven · February 5, 2017

Hi Yarome -

Keep in mind I are a 'lectrical dummy.

- the trailer is used. I don't think the dealer would install 12v starting batteries - the pallet of generic rv dealer branded batteries mine came from said "Deep Cycle" on the sign... these batteries will run my rig overnight in 25F weather - (edit) - parking from 5 pm to 8 am in the dark - batts measure 12.7 something parking, 12.38 - 4 v in the morning...(end edit)

- roaring the furnace, lights on, charging 12v devices, etc. No inverter. I know, I know... how do I survive...?

- T105 batteries do not fit the current battery compartment - too tall.

- I asked about 2 current technology lithium ion batteries that will fit at a solar place. He told me the price. After I got up I sez to the guy, "That's a lot of beer and pizza... :blink: " times that by Canadian dollar factor...why, I could buy another motorcycle... ...

- It looks like a single 8D 12v might fit the compartment. Maybe that will give me more that 85 amp hours of useable capacity I get from these 2?

What's the advantage to parallel 12v battery banks vs series 6v again?

I am just now investigating a solar kit to augment the generator.

Prefer dropping anchor in the boonies vs serviced rv lots.

Yarome · February 6, 2017

12.38 - 4 v in the morning...(end edit)

It looks like a single 8D 12v might fit the compartment. Maybe that will give me more that 85 amp hours of useable capacity I get from these 2?

Prefer dropping anchor in the boonies vs serviced rv lots.

It's quite possible they might be marine/RV hybrid deep cycles, but they are certainly on the lower end if they are. Typically, a hybrid deep cycle will be more in the 95-110ah range. Better than starters but still a far cry from a true deep cycle battery (like your Trojans).

12.38V.. so that puts you in around the 65% SOC (state of charge) by morning. That's probably fine if all you do is overnight and have a charge source every day. "dropping anchor in the boonies" though would be a problem unless you're running a generator a good 2 hours+ a day (based on a 4000w generator. Double that for a 2000w portable).

A single 8D deep cycle would likely give you around 125ah of usable capacity (@50% SOC). That would be a marked improvement over the 2-12v you have now. You could probably squeeze out a 3 day 2 night dry camp if you're judicious with your energy consumption.

Typically, (before I get slammed.. I'm saying "typically") a 6v deep cycle will have heavier/better quality plates. That translates to being able to handle heavier constant loads and a higher charge rate. That equates to basically a longer lifespan under regular charge/discharge cycles. That being said... if they don't fit.. they just don't fit. No getting around that unless you're willing to relocate your battery bank.. or.. lower the bottom of your existing compartment.

noteven · February 6, 2017

I carry a Honda 2000i & the trailer has a fancy charger converter (Charge Wizard something or other...) ... but I prefer the quiet....

I was thinking a battery relocate project might be in order...those 6v batteries are 6 years old now and still going when needed in the camper...

Ray,IN · February 11, 2017

What's the advantage to parallel 12v battery banks vs series 6v again?

The advantage is how they are connected. 12V batteries connected in parallel mulitply the amperage X number of batteries. 6V connected in series to create 12V does not multiply amperage, it remains the amperage of 1 6V battery.

This website created by mark Nemeth, The 12V side of life is an excellent tutorial on the subject.

Lou Schneider · February 11, 2017

What's the advantage to parallel 12v battery banks vs series 6v again?

You have it backwards - a pair of series wired 6 volt batteries have several advantages over a pair of parallel connected 12 volt batteries.

With 12 volt batteries connected in parallel, the current divides between them with only part of the current going in and out of each battery. The amount of current each battery gets while charging is determined by the resistance in series with the battery (does one battery have a connection with slightly more corrosion than the other?), the length of the battery cables (longer cables have more resistance) and the condition of the batteries themselves (older batteries take more voltage to fully charge and produce less voltage under load).

Unless both batteries and all their connections are perfectly matched, one 12 volt battery will "work" harder than the other - getting more charging current and contributing more current to the load when they are discharged.

A pair of series connected batteries (two 6 volt batteries) have only one way for current to flow through them. All of the charging current flows through all of the cells, likewise they all contribute equally to powering a load. This means the two batteries will inherently stay better balanced than a parallel connected pair of 12 volt batteries. A slightly bad connection won't change the balance between the batteries.

A pair of 6 volt batteries have half as many individual cells than a pair of 12 volt batteries. For any total amp-hour capacity, the 6 volt cells will be twice as large as the individual cells in a pair of 12 volt batteries. Deep cycle batteries need big, thick plates to allow long, slow discharge and the larger cells give a definite advantage to the pair of 6 volt batteries.

As far as amperage adding in parallel but not in series, 6 volt batteries start out having at least twice as many amp-hours as a similarly sized 12 volt battery. So you'll wind up with equal or better total amp-hours using a pair of 6 volt batteries versus using a pair of 12 volt batteries.

Tom_M · February 12, 2017

In hopes of simplifying this, if one 12 volt battery is 85 amp-hours, two in parallel yields 170 amp-hours.

oldjohnt · February 12, 2017

In hopes of simplifying this, if one 12 volt battery is 85 amp-hours, two in parallel yields 170 amp-hours.

Tom, that's correct in theory. Of course, however, it requires a perfect balance in connections and cables and resistances for maximum balancing. As noted batteries in series adds the voltage but amp hours IS NOT ADDITIVE, while in parallel it is. For those who don't think connections and cables and cable resistances makes a difference as far as balance in charging and discharging, take a look here:

http://www.smartgauge.co.uk/batt_con.html

In nearly 40 years of RV sales and use I have used auto starting batteries and quasi deep cycle so called RV Marine Batteries sold at Walmart and finally true deep cycle golf cart batteries such as Trojan T-105 in series and parallel and series parallel and I must advise True Deep Cycle batteries for RV use connected per Smart Gauges advice linked above IS THE BEST. I'm NOT getting into Flooded Lead Acid versus AGM versus Lithium in this discussion, just connections.

Still, if budget concerns matters (sure does for me) a person can use what he has until such time an upgrade is due.

John T