Getting started

Topic: Getting started (Read 1019 times) previous topic - next topic

Getting started

April 15, 2019, 07:06:21 pm

Situation. Having trouble starting the engine without the assistance of the house batteries. ie to get the rig started I have to push the booster button. Had mot check the chassis batteries, they looked good. They mot found loose battery connections made the needed corrections it worked great for a while now the starter is sluggish with the same problem. Had a repair shop look at the situation replaced the starter and two weeks later it doesnot want to start. Any ideas? Your valued opinions are appreciated.

Re: Getting started

Reply #1 – April 15, 2019, 07:27:47 pm

Who is "mot"? What is the year and model of your coach? Someone with the same year and model may know something that others do not. How old are the starting batteries? What is their voltage? Are you running this coach every day?
It sounds like your starting batteries are weak, or have bad connections. If the coach is sitting there are parasitic drains on the starting batteries. What did the repair shop say? A new starter is not the place to start.

Re: Getting started

Reply #2 – April 15, 2019, 07:38:13 pm

Quote from: Dakota Slim – April 15, 2019, 07:27:47 pm

Who is "mot"?

"MOT" probably refers to Motorhomes of Texas.

Re: Getting started

Reply #3 – April 15, 2019, 07:43:32 pm

MOT = Motorhomes of Texas.

Starting issues are frequently caused by poorly charged start batteries. They have a number if parasitic loads and unless you have a charger specifically charging the start batteries they will run down over time. As built our coaches do not charge the batteries when the coach is plugged in. This is followed by bad cables or connections. And finally you need to make sure your alternator, isolator and charging system are working correctly.

Replacing the starter when the batteries are having problems gets you a new starter without solving the problem.

Re: Getting started

Reply #4 – April 15, 2019, 07:47:06 pm

A new starter is definitely not the place to start. You should never have to use the boost switch unless it's an emergency. Age of batteries? Pull and clean terminals and posts. Flatten cable ends with a file so they make 100 percent contact with other mating surface. Never a bad idea to have an extra ground cable close to the start/engine batteries. Did the cable get put back correctly on the starter? Keep batteries charged at 13.10-13.50 volts during the off season with a trickle charger. If you can't do that, disconnect batteries at the batteries, not the switch. While 12.7 volts is close to what a battery should be if not being charged, 12.3 volts and lower starts to sulfate the battery and will shorten it's life.

Check voltage with a digital voltmeter AT the battery. If the engine does not turn over quickly, checking cranking voltage with someone else at the wheel.

Which engine do you have? 8.3 Cummins? 8.3 should have two start batteries, M11 three start batteries. We have three and it always has turned over like a top even in cold weather with 24 series batteries. No faster with our new 31 series but more CCAs in reserve for freezing weather.

Pierce

Re: Getting started

Reply #5 – April 15, 2019, 08:00:37 pm

In the great scheme of things batteries are inexpensive. They're also suprisingly delicate. It doesn't take very many deep discharges to ruin a starting lighting and ignition battery's ability to hold a charge.

For what it's worth trying to stretch a bad battery can destroy a starter motor.

Re: Getting started

Reply #6 – April 15, 2019, 08:25:43 pm

Before just THROWING parts at is, well worth doing a proper DIAGNOSIS.

With even an inexpensive digital voltmeter, you can quickly narrow down the culprit.

If voltage as measure at the chassis batteries drops substantially when trying to start, you need to have the batteries load tested.

If voltage as measured at the chassis batteries does not drop substantially but starter sounds like low voltage (slow to turn over),
use our voltmeter between positive terminal of the battery and starter positive to see if there is any voltage drop, which would indicate issues with connections or cable. Do the same between negative terminal and good, clean engine ground.

THEN fix what is wrong!

Re: Getting started

Reply #7 – April 15, 2019, 09:49:09 pm

"You should never have to use the boost switch unless it's an emergency."

I always use the boost switch to start to minimize amps and maximize volts for the high load of starting the engine. I thought that was the purpose of the boost switch. Once I've got the engine going, I turn off the boost switch. So what is the downside of using the boost switch in this way?

Thanks in advance,

George

Re: Getting started

Reply #8 – April 15, 2019, 09:53:52 pm

Actually, I can see BOTH sides of this.

Yes, you should not need to use the boost switch to start, as the chassis batteries should be capable of starting the engine by themselves.

BUT, I happen to agree with George on this. How can you have too little a voltage drop/too many amps of power applied to running the intake manifold heater (most engines) and the starter. That is how I do it, even with excellent batteries in both banks.

Re: Getting started

Reply #9 – April 15, 2019, 10:08:31 pm

X2 on the boost sw when starting. More volts and amps are always good. 😎👍🌵

Re: Getting started

Reply #10 – April 16, 2019, 01:19:18 am

Quote from: George Hatfield – April 15, 2019, 09:49:09 pm

"You should never have to use the boost switch unless it's an emergency."
I always use the boost switch to start to minimize amps and maximize volts for the high load of starting the engine. I thought that was the purpose of the boost switch. Once I've got the engine going, I turn off the boost switch. So what is the downside of using the boost switch in this way?
George

OK, I've owned lots of diesel cars, a diesel RV plus a bus conversion. None had boost batteries. Our fire trucks used two 8Ds to start but no other "boost" battery. Our Perkins sailboat engine had just an engine battery (always want a chance to say how much I hated it from the day it was new).

The big fault of having a boost battery and using it each time you start is you never really know what condition your starting batteries are in. Easy to have the 12 volts until you put a load on the batteries. So why not just have enough batteries to the job originally? If it does not turn over quickly and start, the number or type of batteries in sufficient. So, the boost switch when used each time is nothing more than a crutch, giving a false sense of security in the starting process when it actually may be masking a problem.

Our U300 has three start batteries and originally spun the engine over quickly in warm or freezing weather. When I went to 31 series, it was not because it didn't spin fast enough or slowed down, I just wanted more CCA plus the 31 series was less expensive for the same brand of battery.

If any coach spins ANY faster with the boost switch on, something is wrong with either the batteries or the cables, possibly even both.

And finally, if our Detroit is starting fine and spinning just as quickly as with the boost switch on, why in the world would I want to change things? I have a huge margin at almost 3000 CCA without a need for more.

The boost switch is there for an emergency, use it for that.

Pierce

Re: Getting started

Reply #11 – April 16, 2019, 08:34:43 am

Brand new at this. Appreciate your patience.
mot is Motor Homes of Texas
2002 42 foot U320

Re: Getting started

Reply #12 – April 16, 2019, 08:36:06 am

Quote from: Tom West – April 16, 2019, 08:34:43 am

Brand new at this. Appreciate your patience.
mot is Motor Homes of Texas
2002 42 foot U320

Tom,

There was a learning curve for all of us. Some of us just have more "time invested"!

Re: Getting started

Reply #13 – April 16, 2019, 09:00:01 am

So Tom, have you been able to glean any logical plan of attack from this thread? Putting the "Proper Use of Boost Switch" controversy aside for the time being, you need to do some battery and starter circuit testing with a multimeter. Do you feel like you know what to test, and how?

We don't want to insult your intelligence by being too specific, but sometimes it's not clear exactly where to start and what steps to follow.

Re: Getting started

Reply #14 – April 16, 2019, 09:06:18 am

Did'nt want to throw a wrench in the mix,Jim at the ladies driving school was telling the pupils to Always use the boost switch,I
kinda agree more with Pierce,keep the start batteries in good shape and save the boost for when you really need it.

Re: Getting started

Reply #15 – April 16, 2019, 09:45:15 am

Good points on both sides.

Totally agree that always using the boost switch can lead to an owner not identifying weak start batteries.

Not sure that leads to the conclusion that one should not use the boost switch when starting.

Perhaps a better answer is to occasionally start without the boost switch (think of it as a homemade load test) OR have them load tested periodically (free at most all places that sell batteries).

I still feel the smaller the voltage drop to engine electronics, transmission electronics, intake manifold heater and starter the better!

Re: Getting started

Reply #16 – April 16, 2019, 11:09:10 am

I would agree that using the boost switch to supplement the start batteries and reduce voltage drop etc is a good idea. I'm not sure if it's still a good idea for those of us with Lithium house batteries, which are not recommended for use as starting batteries. Maybe the shared load wouldn't be an issue for them, or would it?

Re: Getting started

Reply #17 – April 16, 2019, 12:39:53 pm

If the house batteries are lower than the starting batteries wouldn't using the boost switch have a negative effect on voltage/amps going to the starter? Just curious.

Re: Getting started

Reply #18 – April 16, 2019, 12:47:35 pm

Quote from: Dakota Slim – April 16, 2019, 12:39:53 pm

If the house batteries are lower than the starting batteries wouldn't using the boost switch have a negative effect on voltage/amps going to the starter? Just curious.

Of course.

But, you have voltage at both banks from the driver's seat: dash gauge is chassis battery. Audit is house battery.

Re: Getting started

Reply #19 – April 16, 2019, 01:19:00 pm

As I posted I think it's germain to this thread that the blue sea auto combiner has a start sense post to auto disconnect the battery banks under the starters load. Obviously for a reason

Re: Getting started

Reply #20 – April 16, 2019, 01:27:14 pm

Quote from: Caflashbob – April 16, 2019, 01:19:00 pm

As I posted I think it's germain to this thread that the blue sea auto combiner has a start sense post to auto disconnect the battery banks under the starters load. Obviously for a reason

And, I suspect the reason is to protect the relay/combiner from extreme high-amp loads. Is there not an override such that you can manually combine them for starting???

Re: Getting started

Reply #21 – April 16, 2019, 02:19:10 pm

I have the non-auto combining version of the Blue Sea 500 amp remote relay combiner with which I replaced the boost solenoid. I inadvertently

started the coach with the the chassis batteries disconnected when installing the chassis battery monitor. It spun up and started as usual with just the house bank feeding the starter circuit through the Blue Sea relay. I was horrified when I realized what I had done, though there was no apparent damage to the system. Still, it was nice to know it is possible... Though there is plenty of cranking amps in the house bank (four times what the chassis battery has), running it all through a long run of three ought cable, a zero voltage drop 240 amp Sterling isolator and the 500 amp Blue Sea relay definitely gave me pause!
Don

Quote from: wolfe10 – April 16, 2019, 01:27:14 pm

And, I suspect the reason is to protect the relay/combiner from extreme high-amp loads. Is there not an override such that you can manually combine them for starting???

Re: Getting started

Reply #22 – April 16, 2019, 03:38:59 pm

Quote from: Don & Tys – April 16, 2019, 02:19:10 pm

I have the non-auto combining version of the Blue Sea 500 amp remote relay combiner with which I replaced the boost solenoid.

Don,
Based on your informative reports, I replaced our boost solenoid with basically the same Blue Sea ML relay. I wouldn't worry a bit about sending all the cranking amps your batteries can muster through that unit, since it is rated for 10 seconds of cranking at 2,500 Amps!

Blue Sea Systems 7701 Solenoid ML 500A 12V RBS

Re: Getting started

Reply #23 – April 17, 2019, 12:39:00 pm

As I have always had a boat with starter and house batteries with a combining switch for emergencies I have always regarded the boost switch as just that - an emergency source of power. I start with the starting batteries only except when the batteries are low for some reason and occasionally to test the boost switch system.

Keith

Re: Getting started

Reply #24 – April 17, 2019, 04:45:11 pm

My comment about the auto connect was that the engine start batteries true condition might be covered up by auto connect. Not the amp loads

Affiliate Notice