Three (yes three) batteries in the rear compartment

Riwright · 02-03-2012, 01:55 AM

I bought a 3124KS with two Costco 12V Deep Cycle Group 27 batteries installed. One is inside the front kitchen cabinet. The second one is in the large rear compartment.

The rear compartment battery is not recessed like some I have seen. I know it was added later, not sure if it was done by the owner or the dealer. There is a secured battery box on the floor of the rear compartment close to the driver's side wall.

I have a CPAP (runs on 12V) that consumes 25AH for a night's use. I am installing a third auxilary battery (another of the same type, but newer) and a converter that will be dedicated to the CPAP.) I am worried about a situation where the propane heater or other loads will draw down the house batteries causing the CPAP to fail during the night. With a battery dedicated for CPAP use I won't have to worry about that.

I have Honda generator and plan to recharge each day.

I think I have the wiring worked out, but I do have some concern about weight. I know some are carrying two batteries in that rear compartment. I would like to move the forward battery back there as well and just have all three of them lined up. That front position is a pain to get to for watering and having the batteries separated like that makes wiring more complex.

Is this crazy talk? Do I need to do anything to distribute the load better or re-enforce the floor?

scrubjaysnest · 02-03-2012, 06:08 AM

You might want to search cpap on some of the other RV sites.

I can't say about the floor.

If you are going to purchase a separate converter you might look at the Samlex ones. They are pricey but give the user much more control.

Our heater only draws 3 amps, 30 Ah for 10 hours. This shouldn't be a problem.

Trojan makes an SCS225, 12 volt 130 Ah battery, again pricey but better suited for the cpap then a dcm 27 battery as very rarely do you see a DCM27 with higher then a 95Ah rating.

Just some thoughts.

02-03-2012, 09:29 AM

You can probably have a full charge on all batteries when leaving anywhere that has full hookups.

However, from what I have read around here, it is not viable to use any generator to fully charge a battery. You can achieve 80 percent charge pretty quickly, but that last 20 percent will take a lot of extra time.

Perhaps someone else will jump in and comment on my theory.

**Bill** · 02-03-2012, 11:50 AM

Quote:

Originally Posted by PopBeavers

You can probably have a full charge on all batteries when leaving anywhere that has full hookups.

However, from what I have read around here, it is not viable to use any generator to fully charge a battery. You can achieve 80 percent charge pretty quickly, but that last 20 percent will take a lot of extra time.

Perhaps someone else will jump in and comment on my theory.

Wayne -

If you charge your battery using the generator's "battery charge" connection, you may be right. Its charge rate is limited to something like 8-amps, which won't fully charge in a short time.

A better approach is to plug the TM's AC power cord into the generator. This fires up the TM's on-board converter, which charges the battery at a much higher rate, just as if you were hooked up to shore power.

Bill

02-03-2012, 12:36 PM

Quote:

Originally Posted by Bill

Wayne -

If you charge your battery using the generator's "battery charge" connection, you may be right. Its charge rate is limited to something like 8-amps, which won't fully charge in a short time.

A better approach is to plug the TM's AC power cord into the generator. This fires up the TM's on-board converter, which charges the battery at a much higher rate, just as if you were hooked up to shore power.

Bill

As I understand it, for a three stage charger, like the converter in the TM running from the 120 volts on my generator:

1. charging up to 80 percent will take an hour or two.
2. charging that last 20 percent will take more than a day.
3. After that, stage three is just a float.

This is assuming that you are using a 3 stage converter/charger. With only two stages I am not sure how it works out.

It is not economically viable to burn gas to run a generator to supply 120 volts to the TM converter so that you can charge that last 20 percent of a battery.

scrubjaysnest · 02-03-2012, 03:09 PM

popbeavers,
You are correct, the tests I ran on my WFCO 8955 showed it took two and half days to reach float stage with no load on the camper battery. Mine now has its own breaker which is off normally. As I have mentioned before we went from April until September dry camping with only the TV to charge the TM battery(s). This is why I am looking at the Samlex as a replacement. The only down side I see for the Samlex is price, that and the word smiths would have you believe it is 4 stage. That last is the latest in AD hype.

**Bill** · 02-03-2012, 05:54 PM

Right you are, Wayne. My point (and I thought yours) was that charging a battery with a generator is no more or less viable than charging with shore power, provided that you use the TM's onboard charger to do it. The generator's built-in charger will not do it.

Bill

02-03-2012, 06:12 PM

Several years ago on a different forum there was a discussion about the most economical way to keep batteries charged when camping for extended periods of time, meaning years in the boon docks.

The consensus was that solar was too expensive to do the job by itself. A fuel powered generator was cost effective until stage 1 was completed, at around 80 percent. After that it was burning fuel way too fast compared to the charge you would get.

So the final answer was to run the generator in the morning until stage one was complete. Then shut down the generator. Then use the solar panels to add what ever you can get from them. That may get you up to 85 percent. maybe more.

**ShrimpBurrito** · 02-03-2012, 07:27 PM

I don't think you have to worry so much about the strength of the floor as you do the lever effect exerted on the frame aft of the axle.

If you typically travel with the gray tank empty, I don't think it's that much of a stretch to say you'd have no problems with a 3rd battery. I say that because I often travel with 2 Trojan T-105s (I think they are 65 lbs each) with a full gray tank (which is at least 160 lbs with 20 gal). So with 3 batteries and an empty tank, you'd weigh less than me.

I doubt another 65 lbs would push me over the edge, but you have a 3124, and the battery compartment is presumably further aft of the axle, which means more stress is placed on the frame. I seem to recall reading here about someone who cracked the frame back there, but I do not recall the circumstances. Maybe they were carrying alot of weight on a rear hitch or something, I don't know. You might search a bit to find that thread.

If I were in your shoes and kept that rear compartment pretty much empty besides the batteries, that would certainly make me feel alot more comfortable, absent any further consideration.

Dave

Riwright · 02-05-2012, 02:22 AM

Thanks for the info. The member who suffered a frame crack was Digger. Here is the thread:

http://www.trailmanorowners.com/foru...highlight=weak

He responded to a PM and told me that he carried two 6 volt batteries as well as a Honda 2000 in the rear compartment. The frame bent when he ran over a couple of Alaskan frost heaves doing 40-45 mph.

The thread also has a photo of the frame where it cracked. There is a hole cut to give access to the axle bolts. I crawled under my TM and I don't see that same hole over the axle. You can see my frame here:

http://www.flickr.com/x/t/0091009/ph...ht/6821691477/

You may need to zoom in to see it.

I think I would be OK. The frame doesn't look like it has the same flaw and the roads in SoCal are pretty smooth. I had to google "frost heave" to find out what it was.

I'll try to attach the picture of my frame to this message.