Another Starting Battery post

[sailr4]

I'm sure this has been asked and discussed before, but my searches have come up empty.  If I have Four 6V batteries, do I have a need for a starting battery?  I just changed over from two group 31's and a starting battery.  The group 31's were so bad that I did have need for starting battery. I see so many posts about adding starting batteries to a 450 AH battery bank.  Why?

Rob

[mark_53]

Hi Rob, I think the simple answer is so you can start your engine quickly if your house bank is depleted or shorted for some reason.  You can use that full 450ah for all the house functions you desire without fear of not being able to start your engine.  The start/reserve battery is isolated from the house bank and can also provide emergency house loads.  Also, it is important to be able to start quickly in an emergency.  You don't want to be fiddling with jumper cables as your drifting towards trouble.

[Braxton]

The nature of the current draw for cranking the engine is fairly different then the what is typically expected of a house battery bank.     Cranking the engine takes a lot of power for a short duration.   Many house type batteries have difficulty putting out enough power quickly enough to crank an engine.   This can be true even if the bank has enough overall capacity.   Without you stating what type of 6V batteries you have it's hard to say whether you will have issues or not.   

Cable gauge and lengths also factor into this.

It may be that when your batteries are new things will be fine but as they age they will have trouble giving enough output to get the engine to turn.   This happened on my boat.   The PO had installed 4 deep cycle gel batteries in two identical banks.   When everything was new I was able to use either bank as the starting bank or house bank just fine.   As things aged neither bank would reliably crank the engine.   I switched to 3 deep cycle batteries for a house bank and a dedicated starting battery.   Viola!   Life is now beautiful, my house bank has more capacity, the engine cranks reliably and flowers now spontaneously sprout out of my ...,    well you get the idea.

So, you may not need a starting battery but eventually you will probably be happier with one.

[sailr4]

Makes sense.  For the record, I have four Trojan T-105's.  My starting battery is relatively new and I am trying to decide if I want to mount it by the engine or not. It used to fit in the battery locker, however, four Trojans...  The next question: Can I use my Echo charger with such a long distance between house and start?  I have read that larger wire is needed, but I have also read that too long of a run will cause the start battery to be seen as full when it is undercharged.

Rob

[Braxton]

Mounting the starting battery next to the engine is ideal.   The closer the better.

I'll decline to answer the charger question, I'll let the real experts weigh in on that one.

[mainesail]

#1 No one should ever be regularly discharging a suitable house bank for a C-34 below 50% SOC or approx 12.2V under average house loads. If you do that regularly, do yourself a favor and stop. Your engine will start reliably every time provided the bank is in good health and the system wiring is appropriate.

Any properly sized deep cycle house bank for a C-34 that can't start the motor at 50% SOC is:
A) Beyond dead
B) The system wiring has major issues

Starting these diminutive engines is cake walk for a deep cycle house bank. IMy systems are regulary starting MASSIVE John Deer's, Cummin's and Cat's on commercial fishing boats very often using four series/parallel 6V golf cart batteries. My commercial fishermen who have switched to 6V vs. 4D's or 8D's are amazed at the longevity they are getting and the cost less. I even have a number of them who fish year round and still crank Cummin's, Deer's & Cat's using 4 6V batteries with ease.

#2 If you don't know your system wiring inside and out a dedicated starting battery may be a good thing to provide start isolation from instruments. While voltage transient damage to instruments is rare a lot of this depends upon how the boat is physically wired. A few days ago I measure an 19V spike on an improperly wired N2K power drop. While it is very doubtful that caused he issues the spikes cna actually go higher than that especially when the boat is haphazardly wired.

#3 I have about 30 or 40 cases I can point to where owner wished they had a reserve or starting battery. In nearly every case, power or sail, the dead battery event cost HUGE money in towing and in one case a grounding on the rocks. Some of these were due to internal shorts, some due to forgetting the 1/2/BOTH was set to BOTH, some cases dead alternators. In many cases just ignoring or being ignorant of house bank behavior and ignoring signs the batteries were toast. I even had one instance where the battery cable chafed through a negative and melted the house bank wiring to the point that the wiring was no longer usable. The current was so high the battery switch literally welded to position #1 and the owner gave it a huge twist and broke the weld. He taped over the negative, removed the house bank positive and switched to #2. Despite the awful smell, he was back in business thanks to a start/reserve battery. He now has fuses. BTW the smell of burned wiring lasted for many months...

Don't forget the reserve nature of these banks. In a good cruising boat electrical system design there are always redundancies. The start battery should not just be though of as a start battery but a reserve/start. I had a customer sailing off shore to Bermuda from Maine when his house bank shorted internally. I had warned him not to take the batteries off-shore in the condition they were in. He gambled and lost. Fortunately the "reserve/start" battery was also a deep cycle, I did this as part of the system design, though he opted for one battery as opposed to two, and while light on capacity it got them to Bermuda in one piece, all be it very, very tired. Old Auto VonPilot did not want to work for very long with only 100Ah's of capacity so it was a long slog in 25+ knots hand steering.. When he got to Bermuda his batteries cost 4.5 times what they would have in Maine and he also lost hundreds in food when they shut down the fridge.

#4 In a perfect world no one would ever discharge below 12.2V and they would replace the bank when it started to show signs of not holding voltage quite as well or as long. Sadly we don't live in a fairy tale world we live in the real world where folks assassinate batteries on a regular basis.

[Jon W]

Sailr4,
   Since you asked us, I reccommend a reserve battery, with a proper electrical system. I have 4 T-105's and a maintenance free flooded reserve battery. All primary cables are 1 AWG. The reserve battery can be used to start the 25XP, or run critical house loads in an emergency. My reserve is under the fwd cushion in the salon. The echo charger is in the middle of the reserve and 4 t-105's. The 25XP starts immediately on either house bank or reserve bank. As I recall, adding the reserve battery next to the engine requires more switches to gain any benefit.

[Ron Hill]

Rob : Unless you stay on anchor for days at a time with out running the engine/no solar and use AC hair dryers and AC coffee pots - 450AH in your 4 T105s should easily start your engine.

The biggest problem in starting is poor wire connections from the batteries to the starter.  It's the poor connections not the #4 size wire. 
Just remember you are only starting a 23hp engine, not a 230hp engine!!

A few thoughts

[Noah]

i used to crew on a nice race boat with a 3 cylinder Ferryman diesel that came with a hand crank! Never had to use it but...just thought I'd share...

[sailr4]

Thanks for all the replies and thoughts.  I had the standard "two battery bank plus starting battery" before I upgraded to the four 6v. Now Im debating finding a spot for the start battery.  I will eventually get around to it, but Im pretty sure that my bank will start the engine.  @Ron, I definitely have connection issues.  I need to redo all the terminals.  @Noah, I had a hand crank on my old volvo M6b. Only time I needed it, it was too cold to use it. SMH.

[kable]

The PO of my boat had 4 group 27 Costco batteries.  Two of them setup on switch A and the other two setup on switch B.  I thought that was really over kill, 2 big batteries for the "starting battery".  Then after some testing I was surprised that the house lights/electronics etc. seemed to run off both A and B.  So the PO must have practiced the routine of run on A, switch to B to start, run on B, back and forth etc.

Anyway, what I ended up doing (for now) was replacing all the batteries (they were 10 years old but still testing good, he equalized every other month etc. religiously checked water levels etc.) and this give me about 400 amp hours, but of course you only want to ever use 50%, so 200 amp hours.

I figure 200 amp hours is a lot based on my usage and unless there is a problem, I really doubt I will go past this.

Now, of course, I should assume there will be a problem.  For now, I purchased one of those small jump start units that theoretically jumps a V8 about 10 times before needing a new charge.  Will need to figure out how to directly hook this up to the starter w/ out quickly draining the entire thing into my 4 empty batteries.  Still not sure how the glow plugs would work.

Guess I am living a bit risky for now.

[Stu Jackson]

kable,

A little noodling around in the Electrical Systems 101 topic will be time worth spending.

Here's one that discusses the differences between the "old school" two equal house banks compared to the "new school" (i.e., past 1980s!!!) school of thought.

Largest House Bank 101 (by Nigel Calder)

http://c34.org/bbs/index.php/topic,5807.msg45046.html#msg45046

Even so, many builders, including ours, continue to deliver new boats with old school equal banks, with no true deep cycle batteries.

OUCH!   

[Bobg]

I have 4 t105 6 volt batteries  as my house bank, I just got off the hook after 4 days, my house bank started my engine after one overnight,  I run my fridge some led lights and watched a movie via my 1750 inverter, after 2 days the house bank wouldn't start my engine, I have a victron battery monitor and the state of charge was around 57, my house bank is around 6 years old, time for new ones?

Thank my lucky stars for my dedicated start, (reserve) battery, which is located behind my engine, I would defiantly recommend a dedicated reserve battery

[Jim Hardesty]

Thank my lucky stars for my dedicated start, (reserve) battery, which is located behind my engine, I would defiantly recommend a dedicated reserve battery

I have left the original factory set-up with the 2 big batteries, don't remember the size.  I only spend a couple of days at a time away from dock plugs.  One battery always has lasted and started.  I do carry a portable jump starter.  Have used it to start other boats, not Shamrock.  My question is where would be the place to attach the battery clips if I do ever need it?  I'm thinking clip the negative to the battery, positive to the on-off switch on the other side.  That would keep sparks from the battery area.  I've never tried it. 
Thanks,
Jim

[Bobg]

I also carry one of those small jump starters from crank, I have one in my car and my boat, never used it on my boat but many many times on my car, tractor, lawn mower, ect. I just install it on my battery, i do understand your concerns of sparks on a boat, these small jump starters are amazing, they will jump start a car when the battery is so low that nothing works on the car.  I also carry a honda 1000 generator, maybe overkill, but I get piece of mind.  I did think my 4 T 105's should have lasted more than 2 days on the hook with just the fridge, and some led lights, can't advise where to put the positive lead, I would just put it on the battery, but, I'm don't think main sail would though