Life expectancy of house and chassis batteries in a DP

[Scottro]

Our batteries in our coach are about 3 1/2 years old. Went to start the generator this morning after the coach has been sitting for about 4 to 6 weeks and it didn’t have enough cranking power to start. I don’t have a battery tester at my disposal right now. How long generally do those batteries last?

 

[Mark_K5LXP]

There's more to it than just battery age. A battery that's been discharged won't have any power no matter how old it is. Generally batteries don't die, they're killed by improper use or storage and at 3-1/2 years that's pretty young to be giving up. New batteries might initially resolve the symptom of batteries being discharged but if you don't discover what's killing the batteries you have, you're destined to repeat the process. You don't need a special "tester" for storage batteries, just some loads in the coach, a $10 voltmeter and a clock can reveal storage capacity. This test will come after you figure out if there's something drawing them down, or if they're not being properly charged between uses.

Mark B.
Albuquerque, NM

 

[Gary RV_Wizard]

As Mark says, age is probably not the main factor here. In a late model coach your generator probably starts from the chassis battery and it must be low on charge. Could you start the coach engine? It's not unusual for a modern coach loaded with amenities to discharge it's batteries if left unused for maybe as little as 2-3 weeks. Did you try the Auxiliary Start switch, the one that couples the house battery bank to the chassis batteries for this starting in this sort of situation?

Generally, chassis (engine starting) batteries probably last 5-7 years. House batteries vary more with both type and usages, so they can be anywhere from 2-10 years, but 4-7 is most common.

 

[Utclmjmpr]

Always remember that a battery does NOT CREATE anything,,, it merely stores energy that you placed in it for that purpose... If you ( or others,) take out more than you put into it, it will be like a bucket with a hole in it..>>>Dan

 

[Scottro]

Gary, yes the main engine fired right up without hesitation. To get the generator started I did use the battery booster option and it immediately fired up as well.
So if I’m understanding correctly, it’s possible there may not be a problem as far as something drawing off the batteries or discharging the batteries when it’s in storage? This could be just a normal thing from sitting?

 

[Mark_K5LXP]

Lead acid batteries do suffer from self discharge but at a very slow rate. 6 months is a typical duration between maintenance charges during storage. Many RV's do not completely turn "off" despite the implied function of the "disconnect" switch. So for an otherwise "good" house battery to discharge in the period of 4-6 weeks implies it either wasn't charged to begin with, or there's a small load present that's discharging it. A simple multimeter will reveal any discharge occurring.

Mark B.
Albuquerque, NM

 

[Gary RV_Wizard]

It's not uncommon for there to be a drop in the battery voltage available at the generator starter vs the battery itself. This can be due to the wire length & distance or corrosion at the connections. A difference of 0.5v can mean no start at the generator while the main engine starts ok..

 

[Kirk]

In a late model coach your generator probably starts from the chassis battery and it must be low on charge.

When did that start happening and what RV? I have never seen a motorhome that did not have the generator wired to start from the coach batteries.

To get the generator started I did use the battery booster option and it immediately fired up as well.

Which demonstrates that your generator, like all that I have worked on, does get starting power from the coach batteries and not from the chassis battery. But that doesn't address the questions that you asked. It could be that your coach batteries are starting to fail, or if you have not serviced them it also may be that you need to add distilled water to bring electrolyte to the proper level. It is also not uncommon for something to draw down coach batteries while sitting unused. Does your coach have a battery isolator and was it in use? A period of 4-6 weeks is pretty short for that much discharge, but it can happen. With the coach batteries fully charged, do they start the generator easily as they did when new?

 

[John From Detroit]

How long do batteries last? Where do you live
Mine (Live in MI winter in SC 8-9 years
Arizona 2-3 if you are lucky

(heat is the killer)

Also depending on the coach 2 weeks can be a long time.

The good news... DEEP CYCLE batteries like the GC-2 Golf car battery.. MAY recover from a deep discharge.

MARINE/deep cycle.. less likely to do so

Starting battery toast.

 

[Scottro]

Gary…it’s sounds as though there may be nothing wrong necessarily,possibly just a normal process of the batteries draining from sitting for a extended period? Or am I misunderstanding?
Also,yes the main engine started without an issue, so I did pair them together with the booster and the genset started without a problem.

 

[Scottro]

Thank you everyone. We are camping now and having in and out internet problems, so it seems I’m responding and other posts are coming in that were written before I responded. Sorry for overlaps.
Kirk you had asked what year our coach was…it’s a 2014 Winnebago Forza. The batteries(both chassis and house) are all June of 2018’s. I’m still not sure if I’m clear if this just may be a normal discharge situation. Sorry for confusion. Also we are in Central Florida.

 

[Scottro]

Also, I do not know of a battery isolator on our rig, but I do shut the inverter switch to the off position located under the house in the rear compartment. I also of course shut off the battery switches in side the coach when storing it. I have not tried starting the generator sine we started camping as we are on full hookups. I’ll try after we unhook. I will also do a battery service asap. I have not checked the water levels.

 

[Kirk]

,possibly just a normal process of the batteries draining from sitting for a extended period?

It is important to understand that a battery is not at 100% up to the end and then suddenly fails but they actually slowly degrade with age. A battery that is 3 1/2 years old would at best be at perhaps 80% of it new capacity and may well be lower than that. The only way to know that is to take the battery out and get it load tested by one of the places that sell batteries. Pretty much all of them have that service and do not charge for it.

I also of course shut off the battery switches in side the coach when storing it.

If you have switches that are labeled as battery switches they most likely are battery isolation switches. If so each switch would cause a solenoid to open the circuit to a battery. With 2 of them, most likely 1 is for the chassis battery and the other for the coach batteries. An easy test to would be to turn them off and see if you have inside lights. Or with the lights on, operate the switches and see if the lights go out.

 

[Gary RV_Wizard]

Gary…it’s sounds as though there may be nothing wrong necessarily,possibly just a normal process of the batteries draining from sitting for a extended period?

Correct. And if there is a problem, it may be some extra overhead in the wiring to the generator starter.

As Kirk explained, 3.5 yo batteries are surely a bit tired and have less than their original capacity. Whether that is 80% or 60% depends on how they've been used and cared for, but they should have some years of useful life left. However, if your feel you need to have the full original capacity available, replacing now is an option.

The normal situation for house & chassis batteries is "isolated", i.e. the two systems are normally kept separate. They are only connected together, i.e. "not isolated", under specific circumstances and doing that connection (or not) is what the "battery isolator" does. Perhaps it should be called the battery un-isolator? The Auxiliary or Emergency start switch is a manual override of the isolator, telling it to connect rather than isolate. Other components in the coach automatically trigger the isolator to connect when appropriate.

 

[decaturbob]

Our batteries in our coach are about 3 1/2 years old. Went to start the generator this morning after the coach has been sitting for about 4 to 6 weeks and it didn’t have enough cranking power to start. I don’t have a battery tester at my disposal right now. How long generally do those batteries last?

if lead acid, 3-5 years at best and you have to stay on top with keeping them charged and the fluid level maintained. Gel cell types will last in a similar range but no issue with fluids.