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Old 06-01-2015, 09:37   #46
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Re: Need dedicated starting battery?

Go for it. I've had a similar system for years and i like it very much. I don't have a generator either, just a solar system. If you're observant you will never run your batteries so low that you can't start your engine whenever you want. In the meantime you will have:
- More house bank capacity
- Longer battery life (because you won't be discharging your house bank so far on each cycle, and the battery voltages (assuming they are all the same age, make, capacity etc.) will all be the same at the beginning of a charge cycle)).
- Simpler electrics, because now you don't need an isolator or anything to charge your house bank separately from your starting bank.
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Old 06-01-2015, 12:59   #47
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Re: Need dedicated starting battery?

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Originally Posted by skipmac View Post
Maybe playing with semantics here but starting an engine is a very large current draw, say 100-150 amps for a typical sailboat engine. However, the total amp hours used from your battery is not much since the draw only lasts for a few seconds.

Another issue is the voltage. Even if you have a huge house bank with lots of amp hours, if the bank is partially discharged and voltage is low you might have trouble starting the engine. Also I don't think it's good for the long term health of a starter motor to run it on low voltage.

I do agree that an 8D is not the best fit for starting your engine. Something smaller rated for cranking instead of deep cycle would be much better.
You are correct, Skipmac, and I mispoke. The overall draw is high but with the short duration the actual amp hours used are quite low. That's what MS's short video demonstrated as I recall.

In my case I actually do have a small (G24) additional batt. that is used solely for starting my generator. It is also a Lifeline AGM (like the 3 8D's), and it's rated at 870 CCA (when new obviously, now 5 yrs. old). My service manual calls for a starting batt. that has 400-600 CCA so theoretically this small Group 24 could also start my engine. I also have a manually activated relay that ties the house bank in if need be for starting purposes. So not much to lose really by using the 3rd 8D as part of the house bank vs. having it dedicated solely to engine starting.

Figuring out how to best configure the two engine alternators for this new set-up, however, will be more challenging for me. As of now, one charges only the engine start batt., whereas the other charges only the two house batts. Both charging circuits bypass the switches so further investigation is needed. No wiirng diagram either which is a bummer.
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Old 06-01-2015, 14:53   #48
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Re: Need dedicated starting battery?

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Originally Posted by Exile View Post
You are correct, Skipmac, and I mispoke. The overall draw is high but with the short duration the actual amp hours used are quite low. That's what MS's short video demonstrated as I recall.

In my case I actually do have a small (G24) additional batt. that is used solely for starting my generator. It is also a Lifeline AGM (like the 3 8D's), and it's rated at 870 CCA (when new obviously, now 5 yrs. old). My service manual calls for a starting batt. that has 400-600 CCA so theoretically this small Group 24 could also start my engine. I also have a manually activated relay that ties the house bank in if need be for starting purposes. So not much to lose really by using the 3rd 8D as part of the house bank vs. having it dedicated solely to engine starting.

Figuring out how to best configure the two engine alternators for this new set-up, however, will be more challenging for me. As of now, one charges only the engine start batt., whereas the other charges only the two house batts. Both charging circuits bypass the switches so further investigation is needed. No wiirng diagram either which is a bummer.
Well, like I said, just semantics or sorting the terminology.

No wiring diagram is a bummer, especially if you have to trace wires running through bulkheads and conduits and under the floor.

If you're fighting with this issue I bought a cheap gadget at Harbor Freight that lets you trace wires. You connect one gadget to the wire which injects a signal into the wire then you take a handheld wand which whines when it's next to the wire with the signal. Very handy.

Two alternators could be tricky. Good or bad it's not an issue for me since I only have one at a time (but have two spares in the locker, one an emergency, internally regulated, one wire alternator).

Connecting alternator output directly to batteries bypassing the switches is I think the best way to do it. Prevents someone from accidentally disconnecting the alternator output from the battery while charging which can fry the diodes.
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Old 06-01-2015, 15:51   #49
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Re: Need dedicated starting battery?

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Originally Posted by skipmac View Post
Well, like I said, just semantics or sorting the terminology.

I actually think the language is quite important, esp. at my (low) level of knowledge & experience with electrical systems. I have enough trouble understanding it all, so maybe I can at least improve how I communicate about it! Thanks for catching that.

No wiring diagram is a bummer, especially if you have to trace wires running through bulkheads and conduits and under the floor. :bang head:

Agreed, although I've slowly been applying labels each time I'm working on it or investigating, and am getting a better handle on where things go. My ultimate goal is to create my own wiring diagram. Handy to have around to say nothing of what I'll learn in the process.

If you're fighting with this issue I bought a cheap gadget at Harbor Freight that lets you trace wires. You connect one gadget to the wire which injects a signal into the wire then you take a handheld wand which whines when it's next to the wire with the signal. Very handy.

Thanks for the tip. I had considered buying a similar device made by Fluke, but it's pricey. Figures good ol' HF would have a cheap alternative. Thus far I've been using my meter, a set of alligator clips, and a long wire, but it's a PITA.

Two alternators could be tricky. Good or bad it's not an issue for me since I only have one at a time (but have two spares in the locker, one an emergency, internally regulated, one wire alternator).

Once I figure out exactly what I have and how each circuit runs, my plan is also to duplicate my alts. so I have spares. Thus far I haven't been convinced I need to upgrade to an externally regulated Balmar, etc. but that could change.

Connecting alternator output directly to batteries bypassing the switches is I think the best way to do it. Prevents someone from accidentally disconnecting the alternator output from the battery while charging which can fry the diodes.

That's what I've read and have been told. Each of the three batt. banks (house, eng start, gen start) have their own switch for the consumption (semantics?) side, but both the alts. & the charger feed each bank directly (if that makes sense). To make things a bit more complex, the switch for the house bank is a 1-2-ALL so you can switch b'twn. the two batts., although I always leave it in ALL.
Anyway, the investigation shall continue! Thanks for your feedback.
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Old 07-01-2015, 09:51   #50
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Re: Need dedicated starting battery?

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Anyway, the investigation shall continue! Thanks for your feedback.
Sounds like you are on the way to getting your system sorted out. It can certainly be complicated and confusing, especially if you don't have a lot of experience in electrical systems. I have an EE degree and I sill have to think hard about certain things and come onto the forum for advice. Of course the fact that my main interest was IC design and digital logic doesn't really help me much.

There are several good threads on the best way to set up your basic battery, charging and switches. CF member Stu Jackson has posted links to some excellent wiring diagrams and discussions from Maine Sail.

I chose a slight variation on the setup. That setup has one house bank feeding a 1-2-Both switch to feed the DC panel. In my system I have the house bank wired to 2 position on a switch to the starter, so primary start battery is 1, house bank for a backup is 2. If the house bank dies I have a jumper I can connect in a couple of minutes to use the start battery for emergency house power. My logic is I would more likely have an urgent, emergency need to start the engine than an emergency to run the lights or chartplotter.
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Old 07-01-2015, 10:35   #51
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Re: Need dedicated starting battery?

We do have the advanatage of being able to pull start the motor if needed but...

We've known a number of people with a dedicated starting battery that was accidentally parralleled and both banks were dead.

This debate reminds me of the argument about transatlantic planes needing 4 engines but the vast majority of new transatlantic planes have 2 engines and old timers are horrified that they must be dangerous.
- If you put together a reliable electrical system and take care of it, there is little risk of not being able to start the motor.
- If you skimp on the system and ignore it, the extra backup may be fully justified.
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Old 07-01-2015, 17:39   #52
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Re: Need dedicated starting battery?

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This debate reminds me of the argument about transatlantic planes needing 4 engines but the vast majority of new transatlantic planes have 2 engines and old timers are horrified that they must be dangerous.
Well they do seem to be dropping like flies these days...
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Old 07-01-2015, 18:41   #53
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Re: Need dedicated starting battery?

Quote:
Originally Posted by skipmac View Post
Sounds like you are on the way to getting your system sorted out. It can certainly be complicated and confusing, especially if you don't have a lot of experience in electrical systems. I have an EE degree and I sill have to think hard about certain things and come onto the forum for advice. Of course the fact that my main interest was IC design and digital logic doesn't really help me much.

There are several good threads on the best way to set up your basic battery, charging and switches. CF member Stu Jackson has posted links to some excellent wiring diagrams and discussions from Maine Sail.

I chose a slight variation on the setup. That setup has one house bank feeding a 1-2-Both switch to feed the DC panel. In my system I have the house bank wired to 2 position on a switch to the starter, so primary start battery is 1, house bank for a backup is 2. If the house bank dies I have a jumper I can connect in a couple of minutes to use the start battery for emergency house power. My logic is I would more likely have an urgent, emergency need to start the engine than an emergency to run the lights or chartplotter.
Yes, I've read a number of helpful threads from Maine Sail, Stu Jackson, and have gotten generous advice from Bill Trayfors among others. I've been told that my system is fairly "customized" and thus departs from the many set-ups I've read about. The other thing I need to stay mindful of is that its present configuration has worked very, very well over the past 7 years, and if nothing else I'd like to not disrupt it. The other reality is that my refrig system runs either off an engine drive or 110v from shore power or genset, so the only significant draw off the batts. under sail is the AP. So once I figure out how everything works, I need to take a systemic approach to determine whether it's really worth moving the 8D eng start batt. over to the house bank.
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Old 07-01-2015, 19:09   #54
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Re: Need dedicated starting battery?

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Yes, I've read a number of helpful threads from Maine Sail, Stu Jackson, and have gotten generous advice from Bill Trayfors among others. I've been told that my system is fairly "customized" and thus departs from the many set-ups I've read about. The other thing I need to stay mindful of is that its present configuration has worked very, very well over the past 7 years, and if nothing else I'd like to not disrupt it. The other reality is that my refrig system runs either off an engine drive or 110v from shore power or genset, so the only significant draw off the batts. under sail is the AP. So once I figure out how everything works, I need to take a systemic approach to determine whether it's really worth moving the 8D eng start batt. over to the house bank.
I'm sure you've heard this one, "If it ain't broke, don't fix it". A good policy most of the time.

There are exceptions (like airplanes, better to fix them before they break) but always think carefully before messing with something that's working to "make it better". Don't ask how I know this.
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Old 07-01-2015, 19:17   #55
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Re: Need dedicated starting battery?

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I'm sure you've heard this one, "If it ain't broke, don't fix it". A good policy most of the time.

There are exceptions (like airplanes, better to fix them before they break) but always think carefully before messing with something that's working to "make it better". Don't ask how I know this.
I hear ya! Besides, I have plenty of other systems to work on that are broke! Or will be soon if I don't tend to them.
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Old 09-01-2015, 03:26   #56
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Re: Need dedicated starting battery?

55 posts so far and only #22 suggesting what I think us the best solution - fit a very small Red Flash AGM start battery.

Ours is 37Ah that starts our 56 HP Yanmar engine in one second, taking less than 1Ah. It has been lying on its side under the floor for ten years and is still working perfectly.

These units are so small there is always somewhere you can fit and forget.
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Old 09-01-2015, 04:24   #57
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Re: Need dedicated starting battery?

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55 posts so far and only #22 suggesting what I think us the best solution - fit a very small Red Flash AGM start battery.

Ours is 37Ah that starts our 56 HP Yanmar engine in one second, taking less than 1Ah. It has been lying on its side under the floor for ten years and is still working perfectly.

These units are so small there is always somewhere you can fit and forget.
Are they available in the states?


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Old 09-01-2015, 07:15   #58
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Re: Need dedicated starting battery?

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Well they do seem to be dropping like flies these days...
But how many are due to multiple engines failing?

Do you tie two chains off to the same anchor in case one fails?
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Old 09-01-2015, 07:37   #59
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Re: Need dedicated starting battery?

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Are they available in the states?
Google didn't find a US source for the Red Flash but I have heard of similar technology in the states but don't remember any brand names. I think they are used in race cars and other applications where weight is a factor.

Sounds good but there must be some downside or everyone would use them. I'm guessing they aren't cheap. Maybe reserve cranking capacity is limited so if you have trouble starting your engine you run out of juice? Voltage drop?
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Old 09-01-2015, 07:59   #60
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Re: Need dedicated starting battery?

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Are they available in the states?


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No they are not. The most cranking capacity in a small form factor for lead acid in the US are the Odyssey TPPL AGM batteries. I install an awful lot of the Odyssey PC925.. It weighs just 26 pounds and can deliver 500 cranking amps at 32F.... Northstar also makes TPPL AGM's but does not offer a battery like the PC925..

If you can fit a larger battery, such as a group 27 or 31, this is always advised so that in the event of a failure of the house bank, you can isolate it and switch in the starting battery to serve through the emergency.. An Odyssey PC925 is only 28 Ah's.... An Odyssey PC2150M (group 31) is 100 Ah's...
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