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Dedicated Starter Battery or All Deep Cycle

14K views 58 replies 29 participants last post by  cshrimpt 
#1 ·
Hello...Mike here from NJ...I have a question regarding batteries. The previous owner of my new to me Pacific Seacraft 37 had 4 Lifeline Deep Cycle batteries that are due for a refresh. One battery is on "Bank 1" which is dedicated for starting and three batteries are on "Bank 2" or the house batteries. My question is, should I purchase a purposely built starting battery for cranking or should I purchase four deep cycle and crank the engine with a deep cycle battery on Bank 1.
The engine is a Yanmar 4Jh2E and fire right up. Funny thing is, the deep cycle battery on Bank One is the battery giving me some trouble. It will not hold 13.5 v for long and discharges rapidly. I wonder if all these years of using a Deep Cycle battery for cranking killed it?
 
#2 ·
You can find lots of threads on this from people far more knowledgeable than me, but I have read them all, and I would only use one of two options for a small auxiliary sailboat with no generator and no electric windlass.

1) One bank of deep cycle batteries you use for everything. Keep things simple and just have one bank. Use it for everything. The only downside of this is if you somehow discharge your bank deep enough to not start your engine, you would need outside help. This is of minor concern if you are reasonable conscientious, staying in the US, and have towing insurance.

2) One bank of deep cycle for the house bank, and a single cranking battery for starting the engine. This is the option I use, just because we wander off the beaten path again. It is more complicated, and more expensive to install, but worth it to me for the extra safety. I have never actually needed this yet, but might someday. Probably not.
 
#4 ·
Really depends on the starters amperage draw and size of the battery. Have used group 27 deep cycle batteries for start batteries on 20-30hp diesels. Deep cycle batteries never an issue though could be that a Group 24 battery would have sufficed so battery was minimally stressed. Have heard some people have had issues with start batteries on larger diesels with not enough amperage burning up starters. Deep cycle batteries are designed for long discharge at moderate levels. Start batteries are designed for short duration high amperage discharge. If your diesel doesn't have a particularly high amperage draw, deep cycle work fine.

Batteries won't hold 13.5 volts for any length of time once off the charger. Static voltage for a lead acid battery is 12.8 volts, plus or minus. Under load a battery will show lower voltage but recover quickly once the load is removed.
 
#5 ·
Until recently, I had the same set up. I decided to go with a dedicated starting battery and house bank. After a bit of research, I removed the old battery switch and installed a Blue Sea add a battery system. This system seperates the banks but allows you to switch to an emergency position should your starting battery die. The install was relatively easy. I did relocate the switch to the bulkhead on the port side of the engine compartment. I can turn it on very simply by lifting the hinged access door. It also takes that very ugly switch off the bulkhead inside the cabin. The system cost around $125.
 
#6 · (Edited)
Do we really need a start battery? I say no... i have always used my BAT 1 House to start the enginw with no issues, for the batteries nor the starter.

Although when I overhauled my battery set up a couple of years ago, I installed a house bank (BAT 1) and a starting battery (BAT 2), I have never needed the start battery. With a "jump start battery pack" aboard as a back up for the back up... if I did it again I doubt I would bother with a "start battery". I would probably just have two house banks and the jump start pack or just one house battery set up and the jump start pack.

As mentioned, consider the battery cable size, and CCA for your engine.
 
#11 ·
Do we really need a start battery? I say no... i have always used my BAT 1 House to start the enginw with no issues, for the batteries nor the starter.

Although when I overhauled my battery set up a couple of years ago, I installed a house bank (BAT 1) and a starting battery (BAT 2), I have never needed the start battery. With a "jump start battery pack" aboard as a back up for the back up... if I did it again I doubt I would bother with a "start battery". I would probably just have two house banks and the jump start pack or just one house battery set up and the jump start pack.

As mentioned, consider the battery cable size, and CCA for your engine.
I have one large house bank and in lieu of the original start battery I installed a couple posts for a jump start battery pack, keeping the original 1/2/both switch in place. If I ever have a flat house bank, I can start the boat by switching to the "start battery" and connecting the jump start pack.
 
#7 ·
1- 13.5V is surface charge

2- How is the start battery benign charged?

3- What are the charge voltage settings for absorption & float.

4- Lifeline batteries, by design, are both deep cycle capable and intended for starting.

5- Using a deep cycle battery for cranking a small aux engine will not harm it and in most cases, when properly charged, they will outlast a starting battery even when used for starting engines. They will also perform reserve duties better.
 
#8 ·
Many thanks for the recommendations. I'll go ahead and replace both banks with deep cycles. This is what the previous owner had set up so I'll continue the tradition. What sparked my curiosity is the weakness of the deep cycle battery in Bank 1 (starter bank). It will drop down to 8.5 volts but quickly jump to 13.5 once the charger is switched on. Definitely shot and will need replacing. The charger by the way is a charger/inverter combo. Thanks again!
Mike
 
#9 ·
Mike
So the reason I went from a setup similiar to what you are proposing to do to one with a one large bank (in my case 4 Trojan T105 golf cart batteries) for the house and a separate starting battery (Optima) was that it made no sense to deep cycle only half the house battery capacity if I split up the bank into 2 banks and left the switch on Bank 1 or Bank 2.

You could do Rain Dogs option 1 by leaving the switch on All or put the house bank on Bank 1 and a starter battery on Bank 2 for Rain Dogs option 2. But there are better ways to wire it and to charge the starter battery (using a DC-DC charger fed by the house bank).

Best
Marc Hall
Crazy Fish - Maintaining, Upgrading and Sailing a Crealock 37
 
#10 ·
:wink

Yes, you do need a starter battery for the engine. And yes, using a deep cycle battery as a starter battery may have contributed to early failure.

Deep cycle batteries are designed to do exactly what the name says. Starter batteries will give more amps (cold cranking amps) in a short burst, then be recharged by the running engine.
 
#12 · (Edited)
:wink

Yes, you do need a starter battery for the engine. And yes, using a deep cycle battery as a starter battery may have contributed to early failure.
This is simply not true for the situation being discussed here.

Deep cycle batteries are designed to do exactly what the name says. Starter batteries will give more amps (cold cranking amps) in a short burst, then be recharged by the running engine.
Trojan Battery disagrees with this premise, as does Lifeline, the maker of the battery in question.

I will mention this once again....

There is;

NO NEED FOR USING A STARTING BATTERY ON SMALL AUX SAILBOAT DIESELS.

Why?

**Flooded starting batteries are lower quality batteries, cheaply produced with lesser quality components. The exceptions would be AGM or GEL batteries.

**They are 1000% not necessary for this application

**Because they are starting batteries they do very, very poor service when called upon as a reserve or emergency battery where you may need to cycle them.

I would not advise anyone wasting money on a starting type battery, or even a dual purpose battery, for a sailboat AUX engine. In nearly every installation I have come across deep cycle batteries, on small aux engines, outlast starting batteries consistently.

Any good quality deep cycle battery will start a small diesel without so much as breathing heavy. It will last longer and can be used as an emergency back up battery without damaging it.

But hey don't take my word for it....;)

"Trojan Battery:

Q: Can I use my deep-cycle battery as a starting battery?

A: Deep-cycle batteries can be used for engine starting but starting batteries should not be used for deep-cycle applications. A deep-cycle battery may have less cranking amps per pound than a starting battery, but in most cases a deep-cycle battery is still more than adequate for the purpose of starting an engine."


Why waste your hard earned money on a cheap starting battery when you can get ample double duty out of a deep cycle product?

I have deep cycle batteries starting 300HP + engines and they do so with ease. Heck I used to start my 6 cylinder Cummins, in February, with a pair of golf cart batteries. Many of my commercial lobstermen have switched to deep cycle golf cart batteries and they are getting, on average, double the life compared to the 4D or 8D starting batteries they used to use.

You can always buy a dual purpose or starting battery but you are really buying a fairly low quality product.

Once again the Lifeline battery in question is designed as both a starting and deep cycle battery.
 
#14 ·
Madmike: Listen to what Maine Sail says.

It sounds as if you have 4 deep cycle batteries on the boat, one of which is dedicated as a start battery. If I were in your shoes, I would use 4 batteries as ONE house bank. This will give you the most usable amp hours and your Yanmar is stupid easy to start. Combining all 4 batteries will increase your usable amp hours by 25%, which makes a lot more sense than having a 1/4 or your battery capacity doing nothing except for the 15 seconds it takes to start each time you head out.

That is the setup that I have with my current boat. 4 x 6 volt deep cycle golf cart batteries in one bank. I have a Yanmar 4JH4E. The system works great. While you are at it, I would also suggest that you read through many of the articles Maine Sail has written and use that information to maybe update the way your electrical system is setup if needed.

If I was going to keep my boat (I am not. It is for sale), I would add a small start battery charged with an echo charger. I don't need it, but it would be relatively cheap insurance. I don't think you need it either and will get much more utility from having a larger house bank.
 
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#15 ·
Exactly... RC is a highly respected and experienced marine technician. I take his commemts with a high level of respect and his knowledge about marine related topics is always spot on, like many of the long time professional contributers here, he offers professional knowledge at no cost, simply to help others.

In fact, my battery installation was much determined by a few generous consultations with him. The guy knows his sheet! :)
 
#16 ·
One advantage of having a separate starting battery (regardless of battery design) is that it isolates the heavy starting current / voltage transients from your house bank and electronics. I have a large AGM house bank, as well as an echo-charged AGM deep-cycle starting battery.
 
#17 ·
I was wandering through my local warehouse store a few days ago and noticed a very small (about the size of a paperback book) lithium "jump start battery". Comes with jumper cables, A/C and 12 v chargers. About $65.

I wonder if keeping one of these in storage would eliminate the need for a separate starting battery? Just use a single bank for everything, with one of these for the unlikely event that the bank is drawn down.
 
#18 ·
I've long kept a larger, heavier (but still very portable) SLA-technology jumper battery onboard (and sometimes in my car) for similar purposes. I've seen the tiny lithium ones, but I still don't trust them yet. Too many fires in high-discharge situations (the Hoverboards are just the latest of many issues). It's one thing to have a fire outside, but inside a confined space like a boat is just a terrifying thought. Both technologies come out of China and thus questionable quality, but SLA is more proven, and companies like Black and Decker can't just fold up shop and disappear, so they have more incentive to ensure good quality control (whether SLA or lithium).
 
#20 ·
I second the second bank and echo charger. Our system is comprised of 4 Trojan wet cells as our house bank and one AGM deep cycle for a start battery. This setup has worked flawlessly in the 4 years we've had it, the last two years full time cruising.

We replaced the 1/2/both switch with an on/off/emergency switch. When switched to ON the house batteries are connected to the house loads and the starter battery is connected to the starter. The Emergency position connects them together to allow the house batts to start or the start batt to power house loads. We went with a 100 amp hour deep cycle for the starter because we wanted a backup for our house loads. Consequently, at anchor our overnight amp discharge is around 40 amp hours, and well in the capability of this battery. During the day the solar panels (425 watts) charge us back to full and keep us topped up until the sun sets. When sailing we use more amps but could trim back our usage if needed.

All of our charging sources (charger, alt, solar, wind) are wired to the house bank. The starter batt is charged via an echo charger and charges only when one of the other charging sources is active, so it does not drain the house at night. We went with an AGM for the start battery because it is located inside the cabin under the chart table seat, and I didn't want to worry about battery venting there. The echo charger is programmable so that it can charge a dissimilar battery type, negating that concern. Per the instruction manual, I added an optional on/off switch to the echo charger and turn it off occasionally when the sky is overcast and I need every amp I can get to charge the house batts.

We monitor both banks with a Xantrex Link Lite meter and the start battery is always topped up.

Again, I have been extremely happy with this setup and it has worked great while cruising.
 
#21 · (Edited)
We replaced the 1/2/both switch with an on/off/emergency switch. When switched to ON the house batteries are connected to the house loads and the starter battery is connected to the starter. The Emergency position connects them together to allow the house batts to start or the start batt to power house loads.
It sounds like you have the Blue Sea Dual Circuit Plus battery switch.

Please be careful when choosing the "emergency" position because your only option is to parallel both banks. This switch can't isolate a bad bank while powering from the other bank, it can only combine/parallel banks.

Combining a good bank with a bad bank, that may have an internal short, can serve to actually wipe out both banks.

If you must use the combine position please ensure that your dead bank is not dead because of an internal failure, dead short etc. before choosing the "combine" position..
 
#25 ·
When I upgraded my electrical system a couple of years ago, I retained the 1-2-Both-Off battery switch and added a Blue Sea battery combiner. The battery switch is left on the house battery and it starts the engine and then the alternator charges the house battery, and through the combiner, keeps the other battery topped off. Should the house battery get low and unable to start the engine, a simple change of of the battery switch to the other fully charged battery allows starting the engine. Simple and no worry about the low (or bad) house battery draining the other one. I like the redundancy and simplicity.
 
#26 ·
...I retained the 1-2-Both-Off battery switch and added a Blue Sea battery combiner. The battery switch is left on the house battery, and it starts the engine....
If I start the engine with the house battery, the voltage drops to maybe 10V as the starter draws 150A (hard to tell, it doesn't last long, and the digital displays don't have time to settle) and the chartplotter and radar both stop and reboot. To me this is unacceptable. When all hell has broken loose and I need to start the engine, the last thing I want to do is wait for my electronics to re-start. For that reason I use a group 24 battery to start the engine on a separate circuit from the three group 31 batteries that supply the house.

I have a Pacific Seacraft 34. The stock battery arrangement (wheel steered) is two group 27 batteries in the port cockpit locker. I have the tiller steered version which has room for two more batteries on a shelf where the wheel steered versions have a quadrant. Two of my group 31 batteries fit in the port cockpit locker without any modification, the third group 31 is on the shelf where I can access it through a cutout at the foot of the quarter berth, and the group 24 (a spiral wrapped battery) is on the inaccessible side of the shelf. The alternator and solar panel charge the house battery, and a Xantrex Echo Charge looks after the engine start battery.

I have been looking for a single switch to replace the stock 1-2-Both switch for this arrangement. Until MainSail brought up the possibility of a start battery internal failure that resulted in an internal short, I thought I had a solution. Now I'm not so sure.

Bill Murdoch
1988 PSC 34
Irish Eyes
Irish Eyes to the Bahamas
 
#28 ·
In reference to "IRISH EYES" comment on the why the electronics shuts down on starting with 3 group 31 for a house bank.

We experience the same problem the voltage does drop to 10 v on starting, the house bank is 2 group 31 batteries, the engine is a 4JHE Yanmar. The AGM Lifeline batteries are 3 years old.

I will be looking for a loose connection this spring as we are not on the boat now.

Any comments would be appreciated.

George
S/V SACHEM
 
#29 · (Edited by Moderator)
Interesting discussion. On my Pacific Seacraft there's a Blue Sea Systems panel with separate on-off switches for house and start battery banks, plus a crossover switch if needed. I've never needed to use the cross over because all of my batteries (4 house, 1 start) have always been normal. I put this down to a very precise and effective charging system (including, but hardly limited to, a solar panel, of course) that keeps the batteries happy. I say this because I think one key is to have a good charging system before worrying too much about switches. If the charging system isn't very good, you'll definitely need some way to use both banks for starting. Having a precise charging system is also less costly, especially if you use expensive types of batteries.
--
 
#30 ·
Since, after 7 years, I'm replacing my batteries, this thread is very helpful. My boat had the conventional 12v starter battery (bank 1) and two 6v house batteries in parallel (bank 2). After reading this thread, I'm thinking I should replace the starter battery with a 12v deep cycle and use the 'Both' setting on my battery selector switch pretty much all the time. Is that right? Then they get equal depletion? I can't complain about getting 7 years out of the last set, but I'm a stickler for optimization. I'm starting a 30HP diesel, BTW.
 
#31 ·
After reading this thread, I'm thinking I should replace the starter battery with a 12v deep cycle and use the 'Both' setting on my battery selector switch pretty much all the time. Is that right? Then they get equal depletion?
NFW, the 'Both' selection should be used for charging if you don't have a charge splitter and that's the only time. The purpose of the start battery is so that you always have a fulll charge state battery to start the engine when needed. When you go to 'Both' and have a bad cell in your house bank or some other failure of that bank, the start battery will discharge into the bad bank leaving you with both banks discharged, BTDT. Forget equalizing the use of the two banks of batteries unless you can't live without doing it.

FWIW, if you ever get into a depleted battery situation but still have some amps left, it takes way less effort to turn over an engine with the transmission in gear if the boat is sailing. The water passing over the prop will try and turn the engine over so much less amperage required by the starter motor when trying to start the engine.

Not a bad idea to have a deep cycle battery as your start bank since it will better serve as the only battery in an emergency situation. It would probably be a group 24 or 27 12v battery which is nowhere near the capacity of a series wired 6v GC batteries. So be aware the start battery will not have the amperage capacity of the house bank and run out of juice way faster if you ever need to use it as a house battery.
 
#32 ·
I like the plan for 2 banks, but both being used as house banks, as needed, and switched.
I don't like the idea of one isolated start battery of some different design, with different needs.

I think this is either over-thinking or trying to plan ahead for neglect.

Is the start batt your dedicated 'life raft' for your engine?
 
#33 ·
I've always only used it to start the engine. I do feel like I'm over thinking it, especially since I only use the motor sparingly. I just want to get the most out of these things. So, I'll go deep cycle for both, use bank 1 while underway, bank 2 all other times (coastal cruiser and racer).
 
#35 ·
I have a nagging suspicion that "dual battery banks" were a creation of 1960's marketing and sales. You know, "Our boats have a dedicated emergency starting battery!" and people bought into that because it sounded like a good idea.

Except, everything costs money and SLI batteries are way cheaper than real deep cycle batteries. And besides, they are "STARTING" batteries so they seem right for the job. With two or three times longer warranties as well!

But the awkward truth is that any deep cycle battery ($$$) will typically have enough capacity to be used as an occasional starting battery. People got deluded by salesmen trying to save $50 on a boat (hey, people will by the boat that is $50 cheaper) and an urban myth got established.

The same way that fusible link wires used to be standard, even though they always have been a fire hazard compared to proper fusing.

And the myth of needing a "start" battery, persists. Even when one large bank or two equal banks has been long-proven more effective, and devices like a "Battery Buddy" (low voltage shutoff) are easily installed to ensure the battery always has enough power remaining for an engine start.

Myths die hard. I know this because my Kraken tells me there are absolutely no dragons where the chart said "HERE BE DRAGONS" and he's spent years and years in those waters.
 
#37 ·
Yeah start only batteries are a myth till you need them. Learned about the 'Both' switch position draining good battery into bad battery the hard way after a long weekend on the hook. Luckily the wind finally came back and was able to get home. Two equal sized battery banks would be fine if you have the realestate to dedicate to them. Have never had a boat where I could fit two banksTakes a of golf cart batteries. Doubly so in current boat where the house battery bank is 4 gc batteries. Adding the two more GC batteries to bring total to over 400 amp to feed the greedy reefer meant I had bulid a battery box in the engine room for the group 27 deep cycle engine battery. Yes, deep cycle batteries of adequate amperage will start a diesel engine no problem. Anyone who relies on one bank of batteries is cruising for a big disappointment. The jumper batteries are a solution but still have to be stored somewhere. Do have the dual use advantage as long as you remember to take it out of the car when you go sailing.
 
#41 ·
I guess we're in the minority- single house bank that also starts the main.

Though it is a 1040ah bank, with 5 charging sources (one of which being honda 2000 suitcase), so low battery power isn't usually a big concern.

I think segregated start battery is critical only if you have a small house bank or limited recharge options. In that case a dedicated start with acr tied to the house would be a good solution.
 
#42 ·
What you say is OK as long as nothing malfunctions to drain down your whole bank. The purpose of isolating the starter battery is to minimize the chance of losing your ability to start the motor in the event of a parasitic load, without the need for having a generator and other remote capable charging sources.

Another viable backup is a jump starter battery, but you need to keep that charged also.
 
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