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Topic: ISM450, do you really need 3 starting batteries? (Read 901 times) previous topic - next topic

ISM450, do you really need 3 starting batteries?

Is there any technical necessity for there to be 3 starting batteries on an ISM450?

Yeah, I know more is better when it comes to starting amps, but is there any other reason?

The reason I ask is that one of my starting batteries (Optima Blue Top) has gone south.  I disconnected it and just left the two good (supposedly) batteries hooked up.  Coach starts fine without boost on.  Everything seems to work fine.  When I bought the coach last year, the previous owner said the batteries were only a few months old.

Being cheap and getting pretty tired of forking out $$$$ every time I turn around, I'm tempted to just leave it this way until the other two batteries go south.

Any opinions?

Jim
Jim McNeece
2003 U320 40'
2017 Chevy Colorado Tow

Re: ISM450, do you really need 3 starting batteries?

Reply #1 –
Jim

After stretching my 2 Redtops much longer than I should have, I now know that letting the system go to low voltage is much more a problem than just starting.  On my trip from OK to NAC, low voltage caused my Allison tranny to act up.  I thought I would be stranded 3 times when I tried to accelerate and just got noise from the engine.  Tranny was blinking, so I took it out of gear and then put it back in- worked.  When I finally got to MOT- they put Keith Risch on it and all the problems were due to low voltage.

From now on, I will check batteries and make sure they are good and holding a charge.  Could have saved me some $$$
if I had done it sooner.

You choose what is best for you.

Good luck Jim

Ted
Ted & Karen
2001 U270 36' - sold after 12 years full timing

Re: ISM450, do you really need 3 starting batteries?

Reply #2 –
Under warranty if that new, check with dealer to see date stamp and warranty
Tim Fiedler    2025 LTV Unity MBL on Order
2000 Chevy Tracker 2 Door Convertible 4WD Now lifted 4.5"
1985 Citroen 2CV6 Charleston
Murphy Rebel on wheels with 175HP Titan
Cessna P337
1980 48' Westport MY (!/4 Share)

Re: ISM450, do you really need 3 starting batteries?

Reply #3 –
Quote from: Jim McNeece –
The reason I ask is that one of my starting batteries (Optima Blue Top) has gone south. 

Do you know why you have the Optima Blue Top batteries? The Blue Tops are designed for marine use and have two sets of battery terminals. Also, the Blue Tops with a dark-gray case are starting batteries, while the ones with the light-gray case are dual purpose (starting and deep-cycle) and have a lower cranking-amperage capacity. Therefore, they are not as well suited as those with a dark-gray case. I suspect the Blue Top batteries are more expensive than are the Red Tops, and so if you are going to replace your batteries with more from Optima then I think the Red Top batteries would be a better choice.
David and Carolyn Osborn
1995 U320C SE 40' Build 4726 Feb 1995
FMCA 147762
Motorcade 17186

Re: ISM450, do you really need 3 starting batteries?

Reply #4 –
Mine has 4 starting batteries, still do not understand why as they seem to have been factory installed when I replaced them with 4 Red Tops.
On a positive note.... the old girl really turns over.....
Rick & Deborah Webster
2002 3610 U320 #5964
2014 Jeep Wrangler Sahara JKU- 'Copperhead'
Richland Chambers Lake, East Texas

Re: ISM450, do you really need 3 starting batteries?

Reply #5 –
I think the ISM requires 1800 amps to start. Your batteries are probably 900 each and the boost is 100 amps.  SO you have enough with two but the issue is if it is cold out or they are getting weaker then you will need the third.
2025 Wanderbox Outpost 32 on F600 Expedition Motorhome
2015 Born Free Royal Splendor on Ford 550 nonslide version  for sale
Former Coaches  covering. 360,000 miles
1999 34 U270
2000 36 U320
2001 42' double slide U320
2018 Jeep Rubicon

Re: ISM450, do you really need 3 starting batteries?

Reply #6 –
Quote from: John S –
I think the ISM requires 1800 amps to start. Your batteries are probably 900 each and the boost is 100 amps.  SO you have enough with two but the issue is if it is cold out or they are getting weaker then you will need the third.

I believe that is the bottom line, margin for marginal conditions,  I ran my ILS400 with only two for a time when the third went bad, and it was fine.  But the remaining two were healthy (they lasted another five years) and it was summer.
Tom Lang K6PG (originally  KC6UEC)
and Diane Lang
2003 38 U295 build 6209
2016 Jeep Grand Cherokee Summit Ecodiesel
still have tow-ready 2006 Acura MDX 
Temple City, California
Motorcade 16681 California Chapter President
SKP 16663 member of SKP Park of the Sierra, Coarsegold California
FMCA F071251
Retired electrical and electronic engineer

Re: ISM450, do you really need 3 starting batteries?

Reply #7 –
Motors like starters draw more current with voltage drops, and more current can damage motor's windings, especially over time. More batteries mean more amperage available to help prevent voltage drop.

Cold weather reduces battery voltage, and batteries my not always be at maximum for every start, like after starting several times or having to crank longer. So extra reserve may be a blessing when needed.

May even start with one battery, but with a greater voltage drop, and maybe not every time.

Can't have too many batteries.

Re: ISM450, do you really need 3 starting batteries?

Reply #8 –
Quote from: Barry & Cindy –
Motors like starters draw more current with voltage drops, and more current can damage motor's windings, especially over time. More batteries mean more amperage available to help prevent voltage drop.

Cold weather reduces battery voltage, and batteries my not always be at maximum for every start, like after starting several times or having to crank longer. So extra reserve may be a blessing when needed.

May even start with one battery, but with a greater voltage drop, and maybe not every time.

Can't have too many batteries.

All the more reasons to use the boost switch.
Tom Lang K6PG (originally  KC6UEC)
and Diane Lang
2003 38 U295 build 6209
2016 Jeep Grand Cherokee Summit Ecodiesel
still have tow-ready 2006 Acura MDX 
Temple City, California
Motorcade 16681 California Chapter President
SKP 16663 member of SKP Park of the Sierra, Coarsegold California
FMCA F071251
Retired electrical and electronic engineer

Re: ISM450, do you really need 3 starting batteries?

Reply #9 –
A problem of pulling high starting current through a boost solenoid is that 90% of these solenoids cannot repeatedly handle all those amps without self-destructing over time and not being useful when it is really needed.

Boost solenoids are not a replacement for having adequate starting battery power.

Re: ISM450, do you really need 3 starting batteries?

Reply #10 –
Yes. 
"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: ISM450, do you really need 3 starting batteries?

Reply #11 –
From the ISM Operation Manual. 

Minimum Battery Requirements:
At  0 Degrees F: 1800 CCA, Reserve Capacity 640 amps
At 32 Degrees F: 1280 CCA, Reserve Capacity 480 amps

Since Group 31 Blue Top Optima's have 900 CCA's at 0 degrees F, 2 meet the minimum requirement.  Of course, boost adds some extra, but then CCA's probably decrease with age (?).  So 2 could fall short of the needed CCAs in really cold weather.

So the answer to my question is "It depends on the temperature."  For us people who avoid cold weather, 2 batteries will be just fine.  For those who have to travel in really cold weather, better to have 3.
Jim McNeece
2003 U320 40'
2017 Chevy Colorado Tow

Re: ISM450, do you really need 3 starting batteries?

Reply #12 –
A side note to this issue. I am in the process of replacing my Optima yellow tops with red tops, but ran into an unforeseen problem when we discovered that the OEM connectors are threaded. However, the red tops have slick posts in lieu of threaded studs, so I have to buy some adapters for the red tops. So just a headsup for anyone thinking of replacing yellow tops with red tops.
Royce & Denise, MC #17410
'01 U320 4220 ISM450 Build #5895 SOLD
Toad: '10 Honda CR-V

Travel makes one modest. You see what a tiny place you occupy in the world. - Gustave Flaubert

Re: ISM450, do you really need 3 starting batteries?

Reply #13 –
The redtops come with post and screw in as well.  Mine work on the post and I have three batteries.
I just made sure I replace with the one which are there now.  This way I can clean the post and the cables and reinstall back as is.  DAN
Dan & Shirley Stansel
2002 U295 4020 AGDS Build#6054
Towing Buick Enclave & M &  G Braking
Emerald Bay, Lake Palestine, Texas
MC# 16650

Re: ISM450, do you really need 3 starting batteries?

Reply #14 –
Look for the military style terminals, not the cheap auto version.  I had issues with auto style terminals after replacing my start batteries.

Best of luck.

Ted
Ted & Karen
2001 U270 36' - sold after 12 years full timing

Re: ISM450, do you really need 3 starting batteries?

Reply #15 –
Have three yellow tops
Mike
2001 U320 4010 Build 5878 (Gus)
Wrangle Unlimited Toad
Nacogdoches

Re: ISM450, do you really need 3 starting batteries?

Reply #16 –
Having three start batteries reduces the current on the cell to cell connectors making them less likely to fail. Also extends the life of the starter especially in winter weather.

Next time lose the the expensive colored top batteries and use 3 Duralast 34 series or even better, 31 series batteries. Johnson Controls makes excellent batteries with several brand names. Much easier on the wallet with equal reliability. Read battery forums for comparisons.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: ISM450, do you really need 3 starting batteries?

Reply #17 –
Quote from: Pierce & Gaylie Stewart –
Having three start batteries reduces the current on the cell to cell connectors making them less likely to fail. Also extends the life of the starter especially in winter weather.

Next time lose the the expensive colored top batteries and use 3 Duralast 34 series or even better, 31 series batteries. Johnson Controls makes excellent batteries with several brand names. Much easier on the wallet with equal reliability. Read battery forums for comparisons.

Pierce

Wayne here mentioned a difference of one to two complete battery cabling and connections redoes per year from the outgassing from non sealed batteries.
"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4
 

Re: ISM450, do you really need 3 starting batteries?

Reply #18 –
I have 3 red tops for start and when low temperatures like 20 boost is required. I changed my house 3 8d agm 04  and one of the termanls fell off with  4x 4d agm
I'm so impressed with the capacity that I'm going to make a rack to hold 2 over and under for my start. I know one thing about starting  diesel engines it requires cc amperage and to much is not enough. Go buy a starter and see if it is cheaper than the battery's and tow bill. Oh yea you will have to buy batteries at the the same time.  I buy lots of battery's for my job. This month alone I bought  6 group 31 screw post 1100 CCA batteies. In my home I want agm. So you decide I know money is a factor. Good luck
99 U320 40
97 Jeep wrangler toad
Now full time 8 months
Starting a new brick and wood home
Chattanooga, Tn