Roadtrek single cabin battery life expectation?

[VTPete]

Hi All,

I put a new deep cycle battery listed as 690 cold cranking amps and 101 amp hours in my '96 Roadtrek.

Yesterday I did a drain test, running only my fantastic ceiling fan on high.

To go from 12.3 volts to 11.7 volts took four hours.

The web says that motor draws 3 amps.

I'm curious if this feels about right? I can't figure out an easy place to install a second battery back there (lack of room.)

Thoughts?
-Pete

[BBQ]

.

You have drained too much.

[BBQ]

.

Deep cycle batteries do not usually give cold cranking amps.

Are you sure you have you have a deep cycle battery?

[booster]

There really aren't many true deep cycle batteries around in 12v versions, especially in wet cells which is likely what the OP got. They are almost all combo batteries.



Going by voltage is not very accurate, and even very much less accurate if you do the test wrong.


First you need to make sure the battery is totally full by either looking at the amps going to it at charge, or specific gravity if you have wet cells. A rested voltage of 12.8v with the surface charge removed will only be a maybe full indication. The OP started with a battery that was either bad, or quite discharged, so you can't really tell much.



Then do your rundown and when done remove all loads, everything, so no draw on the battery. Let it sit a few hours and take the voltage reading. Better is to check specific gravity to know the state of charge at the end.


If the OP got 11.7v with the fan still on in a wet cell, and maybe some other loads, that could have severely altered the results. There should have been only 15ah used, so something is amiss.

[VTPete]

The 11.7 volts was read under load. When I removed the load and rested the battery, it came up a bit. As for draining it too much, this battery is supposed to be capable of that without damaging it. And, I needed to know. I actually installed a low-voltage alarm as this isn't something I would routinely do.

I agree with booster that something is amiss. That's what I was really looking for; confirmation. The battery was fully charged to begin with and its resting voltage was 12.3. New battery, too. But, I *did* happen to get the cheapest battery available in town at the time and it's got pretty bad reviews. https://www.walmart.com/ip/EverStart...24DC/180350522

Perhaps you get what you pay for!
-Pete

Originally Posted by booster

There really aren't many true deep cycle batteries around in 12v versions, especially in wet cells which is likely what the OP got. They are almost all combo batteries.



Going by voltage is not very accurate, and even very much less accurate if you do the test wrong.


First you need to make sure the battery is totally full by either looking at the amps going to it at charge, or specific gravity if you have wet cells. A rested voltage of 12.8v with the surface charge removed will only be a maybe full indication. The OP started with a battery that was either bad, or quite discharged, so you can't really tell much.



Then do your rundown and when done remove all loads, everything, so no draw on the battery. Let it sit a few hours and take the voltage reading. Better is to check specific gravity to know the state of charge at the end.


If the OP got 11.7v with the fan still on in a wet cell, and maybe some other loads, that could have severely altered the results. There should have been only 15ah used, so something is amiss.

[booster]

Just a couple of points.


That is certainly a combo battery, so likely to be low water use construction. The low water use batteries usually don't come up quite as far in voltage or specific gravity as true deep cycle batteries. The Costco combo we use as as starting battery in our Roadtrek is lucky to get to 12.6v when very carefully charged, and maybe 1260 specific gravity.


The battery is listed at 44.5#, and is only a gp24, so there is no way it is 101ah at 20 hour rate. I would be surprised if it was actually even 60ah at 20 hour rate, which is the normal rating point.


You may want to pick up an Ezred hydrometer to check specific gravity, it you intend to stay with wet cells, they are nice and easy to use.


Finding good true deep cycle wet cell 12v batteries in a 12 gp24 or even gp27 is very hard to do. I think Crown still makes some, and they seem to be very good batteries, but expensive.

[Bud]

Hi Pete,

I use 2 of those in group 27 size, work well. Does not really matter in terms of an answer to what's happening, but I doubt a group 24 has anywhere near 101 amps measured in the customary way.

The image is for an agm battery, not 12v marine battery.

Bud

[booster]

I think the "maintenance free" is just the fact that it is a no/low water use wet cell, not that it is an AGM, in this case. It does still show caps on it.

[Joe]

I have a class B with 1 battery. Never saw a cranking amp on deep cycle. Have ran my fan all night and never put a dent in charge. Don't think u have a deep cycle battery.

[cruising7388]

Originally Posted by Joe

I have a class B with 1 battery. Never saw a cranking amp on deep cycle. Have ran my fan all night and never put a dent in charge. Don't think u have a deep cycle battery.

Concord Lifeline Batteries are one of the premier AGMs that have both a 20ah and a CCA rating. I've used one as a starting battery for years.

GPL-31XT - Lifeline Batteries

[Joe]

Must be something else draining battery then. I was shopping for 2 hours. Had fan on medium and ran refrigerator on 12 volt. Monitor still in green area when checked.6

[michaelingp]

Originally Posted by VTPete

Hi All,

I put a new deep cycle battery listed as 690 cold cranking amps and 101 amp hours in my '96 Roadtrek.

Yesterday I did a drain test, running only my fantastic ceiling fan on high.

To go from 12.3 volts to 11.7 volts took four hours.

The web says that motor draws 3 amps.

I'm curious if this feels about right? I can't figure out an easy place to install a second battery back there (lack of room.)

Thoughts?
-Pete

I can't say what the problem is, but it doesn't seem right. It's just arithmetic. Say the Fantastic is actually 3 amps (sounds about right). Your various sensors are probably about 1/3 amps. So, you're drawing 3.3 amps per hour. My Roadtrek had two 80 amp-hour batteries, but you only have one. So, if you go by the "don't discharge below 50% rule", you have 40 amps-hours to work with. Divide 40 by 3.3 and you should be able to go about 12 hours before your battery was down 50% (no load measurement of 12.0 volts).

Personally, I think you have a bad battery. You want to take a voltage measurement with zero load. Does your Roadtrek have a battery shutoff? If so, turn it off. Now put a test light across the battery for a short time to remove "surface charge" (if that even exists). Now measure the voltage. It should be at least 12.6 for a new, fully charged battery, and close to 12.7 would be better.

I doubt it's the charging system, but the next step is to put a good battery charger on the battery, again with the Roadtrek battery switch off. If you can't get that battery up to 12.6 I'd say the battery is bad and goes back to Walmart.