Alternators in parallel

[landonshaw]

I have a MD2040-d VOLVO PENTA with two alternators. I thought one went to the starter bank, port side, and the other to the house bank, alternator on starboard side of the engine. Dealing with other issues I made a diagram of the wiring system and found that a positive wire comes off of the house bank to the port side alternator. It's negative side is connected to the negative on the other alternator, starboard side of the engine. It's positive terminal then goes back to the house batteries. They are both12v 60 amp alternators. I have 12v systems on the boat.

Is this an issue? Would it be better to have one run to the house bank and the other to the starter bank.

I have a switch connecting the house to the starter to keep it charged.

Thoughts.


Sent from my iPad using Cruisers Sailing Forum

[Polux]

Originally Posted by landonshaw

I have a MD2040-d VOLVO PENTA with two alternators. I thought one went to the starter bank, port side, and the other to the house bank, alternator on starboard side of the engine. Dealing with other issues I made a diagram of the wiring system and found that a positive wire comes off of the house bank to the port side alternator. It's negative side is connected to the negative on the other alternator, starboard side of the engine. It's positive terminal then goes back to the house batteries. They are both12v 60 amp alternators. I have 12v systems on the boat.

Is this an issue? Would it be better to have one run to the house bank and the other to the starter bank.

I have a switch connecting the house to the starter to keep it charged.

Thoughts.


Sent from my iPad using Cruisers Sailing Forum

I had that on a previous boat also with a Volvo Penta and the second alternator was an option by Volvo. I believe it is also your case?

The kit had not only an alternator but a regulator/distributor that took care of the distribution of the charge between the two banks. If you have only an extra alternator without a regulator, then you need one unless the new alternator comes now with an integrated regulator.

[landonshaw]

Yes the alternator was an extra the the previous owner put on. The instruction sheet shows a connection directly to a bank without being attached to the other alternator.


Sent from my iPad using Cruisers Sailing Forum

[landonshaw]

Integrated regulator and alternator.


Sent from my iPad using Cruisers Sailing Forum

[Polux]

So if it is an original Volvo-Penta kit with an integrated regulator and mounted according with Volvo-Penta instructions I don't believe you will have any problem with it.

Anyway if you want to have a more effective system you can mount a bank controller that will send the charge to where it is needed first, giving always priority to the starter bank, something like a Pronautic, but I don't think you will really need it.

Hands-On Sailor: New Tools for Managing Your Battery Bank | Cruising World

That was more than 10 years ago and I am not sure what was mounted on that system on my boat, if a battery regulator or a bank distributor. It was done by a very good professional and I knew that he was doing the best in what regards efficiency.

Edit:

Sorry about that, my memory is not what it used to be. it was defenitively a charger distributor and Volvo Penta has them as accessories. When I saw the object I recognized it ;-)

http://www.volvopentashop.com/Roysto...%2F2783%2F2847

[landonshaw]

Thank you. Do not have that. Only have two 60 Amp alternators with built in regulators wired in parallel. Both going to the house batteries. Yesterday just put in a manual connection so that I can charge the house alone or the house and starter.

My wind gen and solar go to the house bank only. I will go with this and look at the other equipment. Maybe when back in the states I will purchase and bring back. Thank you for your help. Aloisius, Dave


Sent from my iPad using Cruisers Sailing Forum

[Polux]

Originally Posted by landonshaw

I have a MD2040-d VOLVO PENTA with two alternators. I thought one went to the starter bank, port side, and the other to the house bank, alternator on starboard side of the engine. Dealing with other issues I made a diagram of the wiring system and found that a positive wire comes off of the house bank to the port side alternator. It's negative side is connected to the negative on the other alternator, starboard side of the engine. It's positive terminal then goes back to the house batteries. They are both12v 60 amp alternators. I have 12v systems on the boat.

Is this an issue? Would it be better to have one run to the house bank and the other to the starter bank.

I have a switch connecting the house to the starter to keep it charged.

Thoughts.


Sent from my iPad using Cruisers Sailing Forum

No, certainly not, your house battery bank is much bigger than the lonely battery for the engine starter but if you want to maximize the system you should consider to mount a distributor. The one from Volvo Penta is not that expensive.

[smac999]

I would run one to the start bank, and put an ACR between the house and start bank so both alts can charge the house when needed. but gives redundancy if the ACR fails as the start battery should always be getting power too.

[btrayfors]

If I understand you correctly, you now have two separate 60A alternators both with internal regulators and both running directly to the (single?) house bank. And, you have fitted a switch which allows connection between the house bank and the start battery. Is this correct?

If so, the present system will work OK, though the two alternators may "fight" a bit as voltages rise in the house batteries. Generally this is OK, as by then the batteries will have a limited ability to accept charging current anyway.

Rather than a manual switch, my preference would be for a voltage follower device like the Xantrex EchoCharge or the Balmar DuoCharge. These are completely automatic, and provide necessary charging to the house battery to keep it topped up. No need to switch anything.

By the way, start batteries require very little charging to keep them topped up. It typically takes far less than 1AH (yes, less than one amp-hour) from the start battery to start the engine.

Bill

[Polux]

Originally Posted by btrayfors

---

Rather than a manual switch, my preference would be for a voltage follower device like the Xantrex EchoCharge or the Balmar DuoCharge. These are completely automatic, and provide necessary charging to the house battery to keep it topped up. No need to switch anything.
...
Bill

Volvo Penta has a a dedicated bank charge distributor for that set up (two alternators) as an option that does exactly that and it is not expensive.

[Maine Sail]

Originally Posted by Polux

Volvo Penta has a a dedicated bank charge distributor for that set up (two alternators) as an option that does exactly that and it is not expensive.

Volvo re-labels a Sure Power Diode Isolator. Diode isolators are a very antiquated manner in which to charge batteries that have a number of issues when compared to a VSR/ACR/Combiner, Echo Charger, Duo Charger or a DC battery to battery charger.

Unless Volvo can provide a method of externally sensing the banks then a diode isolator will result in a voltage drop across the diode of -0.6V to -1.0V depending upon rate of charge and this can result in chronic undercharging and lead rather rapidly to unhealthy batteries..

If you run one alt to the start battery, and have no parallel ability, then the vast majority of the time that alternator is simply dead weight providing a couple amps at best to the already fully charged starting battery. This would be wasteful...

By using a combing/paralleling relay (VSR/ACR/Combiner), one that is activated & deactivated by voltage, you can wire one alt to the house and one to the start and the current from both alternators will flow where it is needed.

This will decrease bulk charging times for the house battery bank but there will be slight voltage variances when approaching absorption and one alt will shut down before the other. This is not a big deal as it will just kick back in if voltage drops a bit and they will ping-pong their way along until one alt is all that is necessary to maintain the absorption voltage. The big gains will come during bulk charging with both alts providing all the current they can muster.

Alternatively both alts can be fed to house bank then a smaller combing relay or Echo or Duo or battery to battery charger could be used to charge the starting bank. This would give the most even voltage sensing performance but the gains would be small. If going this way an Echo, Duo or B2B can be used but if going the other way, one alt to each bank, a bi-directional VSR/ACR/combiner should be used.

I would not suggest just letting that alt to sit there and deliver 2-3A as that is a lot of wasted potential energy.......