Bought 2 new Interstate SRM-24 group 24 RV/Marine batteries a few months ago. I have used the MH 4 times on trips lasting from 3-6 days. Never going below 40 amps before recharging. The rating is 85ah each. The batteries have been on the Intellipower charge wizard converter/charger for 6 days and advanced thru the 3 stages to float. They should be fully charged when I began my test.Based on the amount of amps drawn so far, the corresponding voltage indicates a higher % of consumption from ah capacity Example:Ran some lights and fans, at point whereXantrex Battery monitor showed 17.3amps consumed. overnight rest with no draw, the voltage at batteries was 12.54v = 85%17.3amps is 15% of 120ah not 170ah as advertisedContinuing test Drew off to total of 30 amps rest batteries for 4 hour, no draw30 amps consumed voltage at batteries is 12.45v=75%30 amps equal 25% of 120ah again.Final test drew off total of 60 amps rest batteries for 4 hours60 amps consumedVoltage at batteries is 12.25v=50%60amps equals 50% of 120ah again To further check batteries SOC, I removed them and tested SGResults of SG were 1.189Confirms battery ah capacity is 60ah each, not 85ah.The SOC from voltage figures come from the flyer that came with the batteries RV/Marine Deep Cycle batteriesThe temperature here in LA is in the low 80's. So temperature isn't reducing my ah capacity.Any thoughts? If I take them back where I bought them, they will say they are fine.

85 AH is a lot for a group 24. Not seeing it in the chart for SRM 24. 60 AH sounds closer to what I've seen on Interstate group 24. Maybe at a very low rate of consumption......https://www.interstatebatteries.com/content/product_info/marine_f.asp

Good work on measuring your capacity and noticing what is going on.They never got completely recharged at the times they were ever at 14.4 (when they need 14.8) so now they are sulfated and below capacity. You need to do a lot of work to "recover" them using a charger that will go to near 16 volts.Read up on "equalizing" since that is the same technique you need to use for a "recovery" desulfation.BTW the terminology for capacity or usage is Amp-Hours (AH) not amps, just so you don't confuse everybody.

Per Interstate site:Marine/RV Dual-Purpose battery,With both CRANKING and DEEP CYCLE capabilities.It is not a deep cycle battery that would deliver the power for boon-docking.

tpi- it was a high rate of consumption at about 8amps using 3 fans and a couple of lights.

Hi,The bank may well be showing progressive capacity loss. If you are lucky a couple of equalization charges may recover the missing amp-hours. This is what is balanced and best for twin twelve volt batteries.As it often doesn't cost a dime more to do this, I think it is worth the trouble.If you wish to understand the "why" surf here:correctly interconnecting multiple twelve volt batteriesOthers may say it doesn't matter--but unless there is a compelling reason to not optimize charging and discharging why not do it the best possible way?Here is a video of 3 twelve volt batteries that have been wired in an unbalanced manner for 2 years. They have been equalized. The test shows how CCA has been adversely affected.unbalanced for 2 years

House batteries not up to ah rating | Good Sam Community

199 Replies

NinerBikes
Explorer
May 11, 2015
Water cool a Honda Generator and put a common rail HPFP and injection system on it, and you can add a lot more efficiency to that motor, perhaps another 40 or 50%. I am lucky to squeeze 25 or 26MPG's out of a 3.6L gas Touareg, 33-35 is the norm for the 3.0L TDI diesel, once properly warmed up, which usually takes a 12 to 15 mile freeway drive for all the systems to get close to proper operating temperatures. Once all systems are up to operating temp, there is no comparison. Diesel, all the way. No soot, no stinky odor, nothing. Then we can talk about torque under load, also. Hard to beat a stroker motor that is under bore long stroke from square bore /stroke.
MEXICOWANDERER
Explorer
May 10, 2015
South of the Rio Bravo is intense industrial. Not saying CARB did not help. What I AM saying is that the last time I spent in Lozenges the breeze quit and things went ugly. The same for the Bayarhhea and Santa Rosa. When the good old fashioned 100F days made a delayed encore so did yellow-gray skies and eye-watering smog.

The Rio Grande valley has been infamous for pollution since the 1920's. Back then it was charcoal and firewood cooking fires. PEMEX has set mandatory regs for all gasoline to contain MTBE for the region - year round. It's a natural smog trap.

The "Vocho" was one of the worst polluting machines on the face of the earth. No air cooled engine ever made can hold a comparison to a water cooled engine in emissions or economy. Water cool a Honda generator and add direct fuel injection via ECU and you're talking 30-35% increased economy. Not practical but useful as an example.
NinerBikes
Explorer
May 10, 2015
DAS26miles wrote:
They are topped off. SG 1.275-1.280 on all cells. Resting Voltage coming down now, last checked was 13.9v. Equalized for 2 hours twice, 16.0 volts and amps started at 1.2 and dropped to .1 amp.

Something tells me you are screwing up the batteries on purpose to get out of the house and away from the wife so you can monkey with batteries instead.... ;) Especially on Mother's Day. :S

Maybe it's a plan to get a bigger motorhome. Devious!
DAS26miles
Explorer II
May 10, 2015
They are topped off. SG 1.275-1.280 on all cells. Resting Voltage coming down now, last checked was 13.9v. Equalized for 2 hours twice, 16.0 volts and amps started at 1.2 and dropped to .1 amp.
NinerBikes
Explorer
May 10, 2015
It's almost 4 pm, what happened.
DAS26miles
Explorer II
May 10, 2015
NinerBikes, it's equalizing now!
NinerBikes
Explorer
May 10, 2015
Twist the knobs up and equalize those batteries already.
DAS26miles
Explorer II
May 10, 2015
Wow! Looks like a sunny day with a high of 82 degrees. Let's break out the panels! Happy Mother's Day!
NinerBikes
Explorer
May 10, 2015
Mex, I can assure you the emissions in my 2013 VW Touareg TDI are less than in my 1967 VW Beetle. I know it for a fact, because I'd get 27 to 28 MPG in my 1500 cc beetle spewing NOX everywhere, it being a very hot running air cooled motor. I got 2 back to back 37 MPG tanks in my 2968cc 5000 # AWD SUV Touareg over the last two fillups, and most fillups see 32 to 35 mpg any day that the temps are above 70F, which is the majority of the time.

You can not even smell the diesel exhaust on my Clean Diesel Touareg TDI, which runs on ULSD that is 7ppm or less sulfur. You can thank CARB for those changes forcing manufacturers to clean up their act, as well as the petroleum industry. The exhaust treatment on my Clean Diesels would make your head spin. I choose to believe that it has made a difference, I live in the dirtiest air valley around. And I also took a trip down to Big Bend National Park in April, and saw how crappy the air is, as well as visibility that's drifting northwards out of Mexico, where pollution standards are lax.

Those same breathing pains I had as a kid and a young adult came back to me in force the 3 days I spent in the Rio Grande River Valley, right next door to Mexico, with a 5-8 mph breeze blowing out of the south.
landyacht318
Explorer
May 09, 2015
I've been getting some June Gloom Marine layer in Sandyeggo, yet still been getting 7 to 8 amps at 11AM from 198 watts, where as full sun would be 10 to 11.5 amps this time of year.

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House batteries not up to ah rating

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