One Starting Battery For Two Engines?

[halcyon]

Forgive me for sticking my oar in here, but this seems to suggest that the starting current would, in an emergency, flow thru the VSR. I thought that they were only designed to carry a charging current (say up to 60-80 amps) not a starting current of several hundred amps.

Why what current do you want, 500 amp starter motor running currrent, 800/1000 amp starter current, stall current upto 2000 amp

Brian

 

[davidej]

Halcyion

I am thinking of the BEP vsr's which as far as I know will only handle a charging current.

I took a quick peep at your website and you offer a different type.

If these are designed to carry a much higher load, I withdraw my comments with an apology - as long , of course the OP isn't misled into thinking any old vsr will do.

 

[halcyon]

Halcyion

I am thinking of the BEP vsr's which as far as I know will only handle a charging current..

There are other VSR units that take a starter motor current.

It was just odd to me, even using a manual link switch, why you needed the blocking diodes that only created a problem. That is volt drop, possible need for alternator voltage boost, added failure points. While wiring alternators direct to batteries, gives simplicity, no volt drop, and best reliability.

A VSR can then cover the other aspects, but as you say must be the correct specification.

Brian

 

[nnyerges]

Back to basics ... below is an extract from DD 6/71 Service manual .... which you should consult before making any desicion on starting betteries.... and as you can see, there is a difference in recommendations pending on Operating environment and 12 or 24V systems...

At first did not understand the answer you just put me to question # 1. Now I see why.

ERRATA QUESTION#1:

1. In case of an emergency, if I need to use the battery to start the GENSET engines, can I leave the GENSET ON or Should I turn it off?

should say...

1. In case of an emergency, if I need to start the engines with the GENSET battery, can I leave the GENSET ON or Should I turn it off?

 

[nnyerges]

Brian (halcyon)

There are other VSR units that take a starter motor current.

You are right: VSR and ACR with supporting rating up to 500AMP continus, 1200 min cracking current and 2500 max., like the ML ACR of Blue Sea (http://bluesea.com/category/2/productline/388)

How about a battery for each engine (charged by the respective alternator) and use the house battery to start the genset. The house battery can be charged with two VSR and the two engines, or charged by the genset?

 

[nnyerges]

How about my new design, based on the three basic boat charging condition cases:

1. Cruising: I'll keep using my ISOLATOR (2INx3OUT) connected to the alternator of each engine. The outputs go to the starter battery, house battery and the third output, optionally the generator battery through a switch, to keep that battery charged, just in case that for some reason, do not count with both generators, which is quite unlikely, but can occur. Inverter / Charger OFF.

2. Anchored: Genset ON, as need it, charging his battery and connected to the house and starting battery using two ACR. Inverter/Charger OFF. Both ACR are going to be overridden by the engines starting ON switch, so both ACR's are disabled when engines are running (case 1), to prevent any issues of paralleling alternators.

3. ShortLine. Inverter/Charger ON for all batteries as need it.

NOTES:
1. Negative bus and other protections not show for simplicity
2. Optional two fuses or two ON/OFF switch or one OFF/1/2/1+2 selector switch, to avoir starter-solenoid shorts or failures
3. Optional In case of both gensets unavailable
----------------------------------------------
DIAGRAMS
----------------------------------------------

Original topic: Twin Engine + Genset + 3 Batteries Configuration
at http://www.boatinghowto.com/showthread.php?517-Twin-Engine-Genset-3-Batteries-Configuration

 

[halcyon]

How about my new design, based on the three basic boat charging condition cases:

Why do you keep fitting the diode splitter? that is dropping voltage and thus battery recharge level, unless you have battery sensed alternators, or fitting smart regulators.

There is no reason why you cannot have port and starboard engine batteries, plus service battery bank, then fit a twin VSR, we introduced them back in 1983, so well proven.

Brian

 

[nnyerges]

There is no reason why you cannot have port and starboard engine batteries, plus service battery bank, then fit a twin VSR

Yes, there is a reason. If you have read the original topic at the bottom of the diagrams (http://www.boatinghowto.com/showthread.php?517-Twin-Engine-Genset-3-Batteries-Configuration, you find out why not, but in short words, I can’t put my engines alternators’ in parallel and the ACR its going to put them in parallel and also the sense terminals.

If you have others concerns please let me know

Chears,
Nicolas

 

[hlb]

In practice, most boats have one battery, to start two engines, as once you have started the first one, there will be more than enough power to start the second.

 

[halcyon]

Yes, there is a reason. If you have read the original topic at the bottom of the diagrams (http://www.boatinghowto.com/showthread.php?517-Twin-Engine-Genset-3-Batteries-Configuration, you find out why not, but in short words, I can’t put my engines alternators’ in parallel and the ACR its going to put them in parallel and also the sense terminals.

We have been supplying twin VSR's to production boat builders since 1983, or 29 years, those systems are still working, and have caused no alternator problems.

You can believe what you wish, I can only speak from 29 years experience of twin VSR's.

Brian

 

[nnyerges]

Brian,

I never said otherwise, moreover, I am using two ACR’s in my new diagram, at the side of the GENSETS. Not which manufacturer you represent, but the fact is that among all manufacturers recommends this two examples connections:

The following case, the one that we are talking here, VSR/ACR manufacturers recommends contacting with the alternators/engine manufacturer before connection.

You can believe what you wish

It's not what I believe and what is most convenient: 1. using only one VSR/ACR between two alternators, it quite depends on the alternators and has no guarantees. 2. If already have using the ISOLATOR, and can spend in an ADVERC (http://www.ybw.com/forums/showthread.php?t=293830&highlight=Adverc ) monitor or any alternators sense manager that can give a safer way to duplicate charging power from both alternators.

Cheers

 

[dpb]

Have been thinking about this and similar post.
Whilst I can see the point of split diodes, VSR et al, they do seem to complicate things and have some expensive components involved.
So what would be wrong with, in a twin engine set up, have one engine with a single starter battery and the other with a single large as you like battery used for start and domestics. Just have a switchable connection between the battery banks in case one goes flat. I see it does not make best use of the alternator power available but it would work wouldn’t it?

Alternatively I liked the idea of one starter battery for both engines and one domestic battery. But I am unclear from reading the posts if this is as simple as it sounds. In the scenario described above, is it as simple as disconnecting the feed from the second engine battery to starter solenoid and connecting it to the first engine battery?

 

[BartW]

Alternatively I liked the idea of one starter battery for both engines and one domestic battery. But I am unclear from reading the posts if this is as simple as it sounds.

this is exactly what I have, and it is as simple as it sounds,
with a few extra's see post #2

 

[nnyerges]

Bart its right, it is as simple as it sounds. Bart's configuration (Post #2), its the most simple and it works. My final design (Post #26) have more extras, but with extra isolators, and acr's.

 

[dpb]

OK, I had studied those diagrams, so, final question....
In the second diagram of post 2, could the isolator / diode at the top be omitted so that the 'blue' cable from the left hand engine drops straight to the left most battery, with the 'blue' cable from the right engine going straight to the middle battery (I would not have the gennys etc in my set up.)
The point to me is that as I don't currently have advanced regulators (as far as I know) I avoid the diode voltage drop by doing away with it. I would just retain one of the switches A or B, probably on a solenoid switch to bridge the batteries if the starter one went flat.
Thanks for the explanations so far.

 

[nnyerges]

Yes, you can omitt the isolator and use the strb. alternator output to charge the engine battery and the port alternator to charge the house battery. You can also add two VSR/ACR to substitute the Isolator (as in the last diagram 2 of 3, on post #31). The diodes on the to right are just to control de ACR's overide, so if you dont have gensets, omitt all that area and those two ACR's.

 

[nnyerges]

I can only speak from 29 years experience of twin VSR's.

Brian,
At least you can give some explanations. Ok let’s assume that there is no problem having alternators in parallel. So, the following design works?:

 

[nnyerges]

Fit standard isolators to three batteries ( red flag type ), then fit a VSR between starboard engine and gen set battery, and a VSR between starboard engine and service battery. The VSR's be able to handle starter motor loading.

1. I prefer to keep the BS1,2 and 3 switch, so in case VSCR fails, you have a alternative manual way to parallel, without having to use auxiliary battery cable.

2. Now, about the vsr’s placement, you forget to mention that the port alternator is connected to the service battery and the genset have its own alternator to. The following diagrams shows 3 cases for placing two VSR’s. I haven’t show a 4th case with 3 VSR that will be ideal, but is expensive and really doesn’t give to much more advantage. So lest study just two VSR’s:

Case1: This is the way you suggest, the only drawback is when anchoring, the house battery doesn’t benefit of the genset alternators charging current and only depends on the inverter/charger.

Case2: Cruising and anchored, all batteries benefits from each engine and genset alternators. Cruising, each alternator is going to charge the corresponding battery, alternating as each side of the vsr voltage increase to the cut in voltage. Anchored, the genset can charge the service battery and also the starting battery if needed.

Case3: Perfect for anchoring, but the drawback is on cruising. If genset fails, the starting and house battery depends only from the corresponding alternator until one can fail (rare but can happened).

So at least my favorite configuration is Case2.

Nicolas

 

[halcyon]

1. I prefer to keep the BS1,2 and 3 switch, so in case VSCR fails, you have a alternative manual way to parallel, without having to use auxiliary battery cable.


Case1: This is the way you suggest, the only drawback is when anchoring, the house battery doesn’t benefit of the genset alternators charging current and only depends on the inverter/charger.

In the case of 1, you can get VSR's with manual override, so they can be engaged if all electronics fail.

In case 1, with gen set running, it will charge the engine battery via VSR 1, then service battery via VSR 2.

As I said, it's your boat, fit the system you are happy with, you have to use it.

Brian

 

[nnyerges]

Brian,

You are right, so that means that all cases 1,2 and 3 are acting the same way. I still preffer the case2, since it gives more priority to the service battery.

Thank you!