One or Two start batteris for Twin Engine

[micheln]

Keeping with the simple theme, i have a battery for each motor. One switch each, on or off. Two motors and two generator. I dont gave to troubleshoot much if somethings not right.

 

[SteveK]

Both engines start on one battery.
Port charges start battery so always start it first. Starboard charges house bank.
have option to charge all batteries with both engines. No genset

 

[Bacchus]

Doug
A certainly appreciate being placed in the same class as Ski but I will never come close to his knowledge and experience. I'm willing to share as he does but that's as far as it goes!
I debated about putting my gen set back on my 3 bank shore charger when I combined the house. I was unsure of how good an idea it was to have a fairly large and a very small batty bank on a multi bank charger. Is it a good idea to continue applying charging V & A to a small quickly charged batty... especially an AGM?
I have read some that said its not a good idea and I have the ability to top off the gen batty periodically and parallel if needed - which I have never had to use in 8 yrs.
AGMs have very low self discharge and should hold charge over an extended time.
At least thats my rationale why I did what I did. There are lots of ways of doing this sort of thing and I don't think any one right or wrong.

 

[sdowney717]

Tiara boats for decades had twin engines starting off a single bank. They did add a twist to it, one engine alt fed the house bank directly. They did have a manual house/start cross tie in case you lose an alt or similar problem.

It made it a bit tricky to troubleshoot as many operators and techs did not understand the system.

One caveat: With one engine running, starting the second can really spike the amp output of the running engine alternator.

I kinda like the "use the house bank" for starting design. Keep gennie batt sep and if you poop the house bank so far you can't start mains, just run the gen and chgr/inverter a bit.

Many boats already start both engines off one bank as many operators leave the manual crosstie closed.

Simple is better!!! Been on way too many boats where over the years folks have added batts, inverters, switches, cables, etc... And no schematics drawn. Try to troubleshoot one of those and it gets confusing fast.

I have my system very similar to that. I use 1 start battery for both engines, and 2 house batteries. I have two 3 way battery selector switches, so I can combine or turn off batteries. The start battery is only used for starting and charge off the port alternator. The house bank charges off the starboard alternator. I put a combining continuous duty relay made for a golf cart I suppose, between the 2 battery banks. When either ignition switch is turned on, that relay activates, so all 3 batteries can start engines, basically gives it a boost if needed. I also have a helm switch to turn off the relay. I have one wire alternators, both alternators can run together when both engines are running to charge all banks.

I isolated the combining relay coil power using diodes (one way check valve for current) to keep from energizing the off engine ignition when turning on key for the other engine to on. Otherwise turn key on, would send power to the other engine that has key off. It works very well, been like this for years.

The alternators are both fused and send their output direct to their respective battery banks, not thru the battery selector switches.

Have seen no spiking currents on the ammeters, turn on the combining relay, ammeters show output drop on each alternator close to identical numbers, turn off and alternator are again independent. An advantage, the alternators can share the load, no more heavy loading house bank alternator while starter bank loafs. or vice-versa.

 

[StarChaser]

3 One for each engine, plus the Genset, 2 8D's for house batteries, 3 alterantors (1 on each engine). Saved my bacon once, (both mains down, & was able to start the Genset) and that was enough for me.

 

[oscar]

Lets see....... (from memory )

2- 32V banks consisting of 4 8VDC batteries the size of Ohio in series each. 1 pure start bank, one start/house bank. Two 32V alternators, one on each engine.
1-12VDC start battery for the generator. Charges itself, not used for anything else.
1-12VDC electronics battery with 120VAC charger.
2-12 DC in series for the 24V bow thruster with 120VAC charger.

The astute reader will note that the only batteries getting charged with engines running are the 32V banks. So if I want to make sure my electronics stay alive and my bow thruster is there for me on the other end I have to run the generator underway. I also don't have an inverter and the fridge is 120VAC.

So, there are some modifications coming.

 

[Flyguy1967]

On our previous boat boat and our current one, we used one battery (D-4 for the 165hp Perkins and D-8 for Cummins 6BTA). Never had an issue.

 

[Dougcole]

Doug
A certainly appreciate being placed in the same class as Ski but I will never come close to his knowledge and experience. I'm willing to share as he does but that's as far as it goes!
I debated about putting my gen set back on my 3 bank shore charger when I combined the house. I was unsure of how good an idea it was to have a fairly large and a very small batty bank on a multi bank charger. Is it a good idea to continue applying charging V & A to a small quickly charged batty... especially an AGM?
I have read some that said its not a good idea and I have the ability to top off the gen batty periodically and parallel if needed - which I have never had to use in 8 yrs.
AGMs have very low self discharge and should hold charge over an extended time.
At least thats my rationale why I did what I did. There are lots of ways of doing this sort of thing and I don't think any one right or wrong.

Thanks Don.



I was under the impression, possibly the mistaken impression, that my charger, a promariner Pro Nautic 50 amp, could send different loads to each leg.


I have considered adding a little trickle charger just to keep up the genset battery, but I haven't done that yet. Group 27's are pretty cheap.

 

[bayview]

I often thought about adding a small motorcycle battery with an isolating diode to support the electronics during engine start. never got around to it since the occasional interruption was not a big deal.

 

[obthomas]

I like simple. Two engines and a generator all separate, fuel, batteries and alternators.
my electric panel can switch to either of the engine batteries. My Starboard engine batteries are actually a house set and engine start combination. My charger is three bank and charges everything.

 

[FF]

In normal use , most anything will work. A huge house bank of deep cycle is probably the simplest to live with,and longest lasting.

The hassle is not starting when discharged 60% , the hassle is starting when down 100%.

Yes, it does happen , so the use of some sort of second batt is required.

How its wired in to be charged , and easily switched in for the start is the Question.

If your setup answers the Question , you are good to go.

 

[SteveK]

Lets see....... (from memory )

2- 32V banks consisting of 4 8VDC batteries the size of Ohio in series each. 1 pure start bank, one start/house bank. Two 32V alternators, one on each engine.
1-12VDC start battery for the generator. Charges itself, not used for anything else.
1-12VDC electronics battery with 120VAC charger.
2-12 DC in series for the 24V bow thruster with 120VAC charger.

The astute reader will note that the only batteries getting charged with engines running are the 32V banks. So if I want to make sure my electronics stay alive and my bow thruster is there for me on the other end I have to run the generator underway. I also don't have an inverter and the fridge is 120VAC.

So, there are some modifications coming.

I can get the 32 volt alternator to charge a 32 volt battery that is used for a 32 volt starter. Why a 32 volt house system?
Then it appears that the 32 V Alternators are feeding power to an inverter to feed 120VAC chargers.
You said by memory, if accurate seems like a odd setup to have 12, 24 & 32 volt systems.

 

[tozz]

All,


Just thinking about having a dedicated battery for each engine or a shared one for both.


As first, seems like separate make more sense, however, one is simpler.


In either case, you still have the house for a backup. Also, if one wanted more redundancy, use two batteries in parallel for either engine. And you could also hook them to the thrusters for thruster power.



Thoughts?

We have one for each engine and then the parallel to use house bank if an issue arises with the start batts. IMHO, depending on where/how you cruise, you can never have too much redundancy.

-tozz

 

[Ski in NC]

Many old larger boats were built with the whole DC system 32v. Large engines could not be reliably started with 12v starters, and at the time 32v was more popular than 24v.

Then over time larger engines started being built with 24v start as 24 is easier than 32v, just need two 12v batts in series. 8V batts used in series for 32v are big and expensive and not super easy to find.

Owners of these big old boats faced a dilemma. 32v accessories are hard to find and expensive. New electronics are almost all 12v.

So many of these boats kept 32v for starting, and started adding a bit of 12v stuff, usually piecemeal.

Really a pain in the but dealing with these. You could go 24v, but it does not help much as you still need 12v. Going with a series/parallel starting solenoid switch is one way, but those are not terribly reliable.

And wire size for 32v can be sized much smaller than 12v wire doing the same job.

Add a 24v thruster and now you have it: 12, 24, 32, 120, 240v all on the same boat!!!

 

[Pau Hana]

Many old larger boats were built with the whole DC system 32v. Large engines could not be reliably started with 12v starters, and at the time 32v was more popular than 24v.

Then over time larger engines started being built with 24v start as 24 is easier than 32v, just need two 12v batts in series. 8V batts used in series for 32v are big and expensive and not super easy to find.

Owners of these big old boats faced a dilemma. 32v accessories are hard to find and expensive. New electronics are almost all 12v.

So many of these boats kept 32v for starting, and started adding a bit of 12v stuff, usually piecemeal.

Really a pain in the but dealing with these. You could go 24v, but it does not help much as you still need 12v. Going with a series/parallel starting solenoid switch is one way, but those are not terribly reliable.

And wire size for 32v can be sized much smaller than 12v wire doing the same job.

Add a 24v thruster and now you have it: 12, 24, 32, 120, 240v all on the same boat!!!

Sounds like a Hatteras!

 

[SteveK]

Ski, but waiting to hear how the 32V alternators are used to charge 12V and 24V batteries besides a 120VAC charger. There are converters for instance. Also one engine can be fitted with a 12 or 24 alternator.

 

[oscar]

I can get the 32 volt alternator to charge a 32 volt battery that is used for a 32 volt starter. Why a 32 volt house system?
Then it appears that the 32 V Alternators are feeding power to an inverter to feed 120VAC chargers.
You said by memory, if accurate seems like a odd setup to have 12, 24 & 32 volt systems.

Hatteras originally were built as 32VDC and 120/240VAC (They weren't the only ones. Eventually 32V lost out to 12-24-48. Kinda like the VHS/Betamax thing if you remember)

Head pumps, water pump, bilge pumps windlass, lighting is all 32V. There was a small 32 to 12V converter for engine instruments.

PO added a bow thruster. Don't think a 32V version exists. So that's why the 24V system was installed. He also upgraded the electronics and improved the 12V system.

There is no inverter. Charging the 12 and 24V system is strictly through chargers and requires shore or generator power. He ran the generator pretty much all the time. It's 10 years old with 3000 hours.

There were 32V inverters available but they seem to have gone out of production and in any case they were $$$

My plan is to first convert the non-house 32V engine to 24V. I would require a starter, alternator and battery bank. I would then add a 24V inverter/house bank with an intelligent battery isolation manager. I could keep the 12V charger and run inverter AC through it when underway, although that's kinda goofy, or I could install a 24 to 12V converter and eliminate the 12V battery and charger

Then as 32V components die I would switch them over to 24 volt and grow the 24V bank until all is switched over and I convert the other engine to 24V.

With the proliferation of variable 12-48V LED's I am slowly changing over the lighting system to LED.

Some people rip it all out and start over, but my 32V system is in very good shape, and to rip out 3 head pumps, water pump, windlass and I forgot what else is a bit much for me.

 

[Mako]

How about no start batteries? I, and plenty of others, use our house bank to start the engines. So, sure, ypu have have starting batteries for redundancy but aall they do is add wiring, switches, and complexity. And, what if one of those switches go bad. No start?

I had that setup on my big boat.

4) 8D to starboard and 4) 8D to port.

Feeding two jimmies and two generators and two housebanks. Fifty years and none of us owners ever complained. And I suppose crossing the Pacific would be called “cruising remote areas”

 

[FF]

Folks that use a 12v house and a 24 v engine start can simply install a Vanner equalizer.

These are robust and usually trouble free. Used on buses/coaches for many decades.

They work by hooking to both 12v batts and taking a tiny bit from first one , then the other batt.

www.vanner.com › Battery-Equalizer-PB-6-01

With Vanner VoltMaster battery equalizers, the voltage between each 12 volt battery is balanced in a 24 volt series connected battery array. This arrangement equalizes the 24 volt battery system and avoids the over/under charge problems associated with other approaches to providing 12 volts of power.

vanner.com › battery-equalizers