Community Forums

jetman1 · 02-06-2025, 03:43 PM

I have a 2015 Phaeton 40 Ft with 80k miles. The engine start batteries are working great. Turns the engine over fast. Would it be smart to replace them or just wait till they start acting up. Thanks Dan Avilla Prescott AZ

Jim_HiTek · 02-06-2025, 03:56 PM

You likely have an AUX Start switch on your dash. This parallels the house batts with the starting batts momentarily to give an extra boost to start. Using that you can limp along with bad batteries for years as long as you're not boondocking too much. I did that for at least 6 years after mine were showing signs they needed replacing. As long as you service them, add water, clean terminals, and they don't develop internal issues, you can go many years beyond their useful life. Because I've done it back when money was tight but never suffered any from it, other than a bit of concern on occasion. I did carry a set of jumper cables and a nice charger with me at all times.

My opinion and I'm sticking to it.

Oh, I need to add that it's important that when when you're parked, you should use shore power to keep a float charge on them. I accomplish that by having the battery AUX switches for both the house and chassis batts on at all times.

Mark_K5LXP · 02-07-2025, 05:55 AM

Quote:

Originally Posted by jetman1

I have a 2015 Phaeton 40 Ft with 80k miles. The engine start batteries are working great.

What are the date codes on the batteries? If they're 2015 that's kinda pushing it and would replace at the next earliest convenience. If they're newer than 5 years old or so, don't fix what ain't broken.

Mark B.
Albuquerque, NM

garykk · 02-07-2025, 05:59 AM

Replace them. I just had one of our start batteries go bad while the coach is parked in our garage. I knew the battery was bad cause I could smell it cooking. WhenI checked it was hot. Must have finally shorted. The batteries were 6 years old.

txcpl · 02-07-2025, 06:00 AM

I replaced the chassis batteries in our 2014 Tiffin last year, as I noticed that they were not turning over the engine quite as quickly as in the past. I found the best price was from the Freightliner dealership. The chassis is 2013, so I got about as much time out of those batteries as possible.

SafariBen · 02-07-2025, 07:31 AM

As Jim said, you may have backup with the house battery boost, or you may be able to charge with the generator. I'm not a fan of replacing stuff that works, so I would hold off until you notice an issue. Check the temp of both batteries, one will start to get warmer than the other while sitting on a float charger, signalling that one cell is shorting out and you'll have trouble soon.

If you're planning an Alaska trip, or you would not feel comfortable using jumper cables as a last resort, then replacing 10 year old batteries would be a good step.

shepardmike · 02-07-2025, 09:06 AM

Every time you go to start your going to wonder. All you need is a cell to go bad and then the heat goes up and potential a big mess. Not a big expense, replace and have some piece of mind back.

W&L Dan · 02-07-2025, 10:06 AM

I would think if some cells in the start batteries die maybe the boost switch might not be enough if these are factory batteries they have more than done there job I would REPLACE them then no worries JMHO.

Soppy · 02-07-2025, 10:15 AM

I wouldn't bother replacing them till they show signs of getting weak. I'm using 17 yr old AGM batteries in my motorhome and several other pieces of equipment. They have no trouble starting my diesel equipment even in sub zero temps, so I'm not going to replace them. I have had new batteries fail in less then a year.

SafariBen · 02-07-2025, 11:40 AM

Quote:

Originally Posted by Soppy

...I have had new batteries fail in less then a year.

So have I, and that's a big part of why I'm reluctant to change something that's working fine.

Kendorado · 02-09-2025, 01:34 PM

IF you do change the batteries as a DIY project, make a jumper cable from the old batts to the new battts before you disconnect the old ones Otherwise you will lose your computer inputs.
Ken D.

Galvanizd · 02-09-2025, 03:28 PM

You're in Prescott, elevation about 5000 ft. Up until 10 days ago, I was in Payson, similar altitude. My point? How cold is it in Prescott? It was snowing when I left Payson. Cold puts a pretty good strain on the diesel batteries when starting, especially when they are nearing or at the end of their life. Used to have to plug in my block heater when I had a diesel, this time of year. In my experience, sometimes batteries give no warning other times you might get an indication of one going bad. One bad battery may pull the other one down. Battery life for me was 3 to 5 years. After 5 years, I figured I was on borrowed time. Gotta figure the battery cost but it's probably less than a fill up at the pumps. How are old are the house batteries? Might take a look at them also. For me , it's the cost of doing business, that being rving. Peace of mind. It's kinda like when to replace rv tires, varying opinions. But thats just me.

garykk · 02-10-2025, 05:57 AM

Quote:

Originally Posted by Kendorado

IF you do change the batteries as a DIY project, make a jumper cable from the old batts to the new battts before you disconnect the old ones Otherwise you will lose your computer inputs.
Ken D.

I guess that negates the chassis battery cutoff switch