fisherman
Well-Known Member
I have a split charging system and want to change to twin alternators, one for the engine start, the other for services. How should I wire the second one?
Alternator circuit
- Thread starter fisherman
- Start date
halcyon
Well-Known Member
Depends on the split charging system, and what you want to achieve with it when you have two alternators fitted. Do you want both alternators to charge service bank, provide cover if you loose an alternator ?.
Brian
Brian
Juggler7823
Well-Known Member
In my experience 2 alternators are more trouble than they are worth involving a large amount of high current wiring and switching. I suggest you try a larger current single alternator or adding an alternator controller such as the Adverc or Sterking to get more current out of your existing alternator.
pohopetch
Active Member
The simplest system is to have one alternator wired to the house batteries (the larger output one - usually the extra alternator) and the other one to the start battery (usually the standard engine alternator and lower output). Use a simple "Both" switch between both sets of batteries (that parallels them when on)and this is normally off. No split charge system is required and if one alternator or regulator fails just switch on the "both" switch and both sets of batteries will get charged from whichever alternator is working. The wiring is then very simple and there is less to go wrong.
Having both alternators charging the same bank of batteries at the same time, and getting anywhere near the sum of the two alternators output current, depends on their regulators being adjusted. Otherwise, in essence one alternator brings the battery voltage up and the other one sees the high voltage and will not output its full current (its actually more complicated than that).
The usual reason to install a second alternator is because the standard engine one is not big enough to charge the house bank effectively, so the second alternator is usually a high output one and this should be the one connected to the house bank. We have a standard Yanmar 80 amp alternator as the engine one, and a 120 amp Bosch low rpm alternator as the second one. Our house bank is 440 A hr. When the external regulator failed on the big alternator in the middle of the pacific last year the "both" switch kept things going for a month until we got another regulator.
Cheers
Peter
Having both alternators charging the same bank of batteries at the same time, and getting anywhere near the sum of the two alternators output current, depends on their regulators being adjusted. Otherwise, in essence one alternator brings the battery voltage up and the other one sees the high voltage and will not output its full current (its actually more complicated than that).
The usual reason to install a second alternator is because the standard engine one is not big enough to charge the house bank effectively, so the second alternator is usually a high output one and this should be the one connected to the house bank. We have a standard Yanmar 80 amp alternator as the engine one, and a 120 amp Bosch low rpm alternator as the second one. Our house bank is 440 A hr. When the external regulator failed on the big alternator in the middle of the pacific last year the "both" switch kept things going for a month until we got another regulator.
Cheers
Peter
halcyon
Well-Known Member
For interest, since 1983 we have been suppling systems to charge 3 banks from two alternators, both alternators charging the service bank, and to date we have had no problems. Both alternators can charge all 3 battery banks, providing automatic alternator redundancy.
The problems these days is trying to charge more amps than the batteries can absorb, you hit a high voltage quickly, and one alternator cuts out. But then the batteries are only taking the output from one alternator, so you are not loosing anything, but you are gassing batteries badly.
Brian
The problems these days is trying to charge more amps than the batteries can absorb, you hit a high voltage quickly, and one alternator cuts out. But then the batteries are only taking the output from one alternator, so you are not loosing anything, but you are gassing batteries badly.
Brian
fisherman
Well-Known Member
I'd better start again. At the moment I have one 40 amp alternator charging two banks (engine start and service) via a blocking diode. My maximum consumption is 34 amps. While hauling gear at low revs I tend to lose power. Fitting a larger alternator is not the answer, as none give any more charge below about 900 revs. The diode takes out about 1.5 volts, and It is suggested that there are issues concerning which bank the alternator is sensing. I thought it would be easier to fit the second, identical alternator, rather than the Adverc. What I am fuzzy about is how to wire it up, re warning lamp and sensing wire. The alternator has pos, neg and sensor terminals.
VicS
Well-Known Member
Simple
Do away with the diode splitter (It should only lose 0.7 volts though). Wire the output of one alternator to one battery, if it is battery sensed then it must be wired to the same battery as the sensing, if it is machine sensed it wont matter which.
Wire the output of the second alternator to the other battery, sensing as well if it is battery sensed. Connect the terminal for the warning light (Possibly labelled S) to a warning light and then to the same connection on the ignition switch as the existing warning light.
I know this is not what you are asking but a VSR or the X-Split in place of the diode splitter will eliminate the volts drop that the diodes cause. Battery sensing should as well
What you are proposing may not solve your problem but a fancy alternator regulator might.
Sorry have not read all the previous answers, should have I know.
Consider changing the pully ratios to make the alternator(s) turn faster, but take care not to exceed their maximum revs.
Do away with the diode splitter (It should only lose 0.7 volts though). Wire the output of one alternator to one battery, if it is battery sensed then it must be wired to the same battery as the sensing, if it is machine sensed it wont matter which.
Wire the output of the second alternator to the other battery, sensing as well if it is battery sensed. Connect the terminal for the warning light (Possibly labelled S) to a warning light and then to the same connection on the ignition switch as the existing warning light.
I know this is not what you are asking but a VSR or the X-Split in place of the diode splitter will eliminate the volts drop that the diodes cause. Battery sensing should as well
What you are proposing may not solve your problem but a fancy alternator regulator might.
Sorry have not read all the previous answers, should have I know.
Consider changing the pully ratios to make the alternator(s) turn faster, but take care not to exceed their maximum revs.
halcyon
Well-Known Member
Diodes are a big problem.
What size battery bank do you have ? a resonably sized one should supply power for hauling nets, and you should not need to rely on the alternator. I suspect that the diodes are reducing your charge, the net hauling is running down the batteries and you now have sulphation and surface charge. Thus little power for net hauling.
I would say get rid of the the diode splitter, repace it with a relay splitter, get the batteries bench charged, and check the voltage on the alternator. Then if short of power still possibly larger battry bank, and / or larger output, higher voltage alternator.
How far south are you ? that is from Falmouth. PM me the battery size and alternator spec, I have to see Bob at LSUK, he is envolved with the Falmouth boats, and see what he thinks if you like.
Brian
What size battery bank do you have ? a resonably sized one should supply power for hauling nets, and you should not need to rely on the alternator. I suspect that the diodes are reducing your charge, the net hauling is running down the batteries and you now have sulphation and surface charge. Thus little power for net hauling.
I would say get rid of the the diode splitter, repace it with a relay splitter, get the batteries bench charged, and check the voltage on the alternator. Then if short of power still possibly larger battry bank, and / or larger output, higher voltage alternator.
How far south are you ? that is from Falmouth. PM me the battery size and alternator spec, I have to see Bob at LSUK, he is envolved with the Falmouth boats, and see what he thinks if you like.
Brian
Chris_Robb
Well-Known Member
Also sounds like the wiring might be a little substandad if he is loosing 1.5 volts. Clean all terminals or replace wires with heavier....
William_H
Well-Known Member
Yes I second the idea of a VSR rather than diodes. The VSR puts all the batteries in parallel when the engine is running (charging) with no volt drop. So your winch should be drawing from all batteries and the alternator.
The alternator could be given a smaller pulley or a larger one on the engine to increase alternator RPM at idle. However you must accept that the alternator will run very fast at cruise RPM which may destroy it.
Before you fit another alternator you should fit an ampmeter either permanently or temporarily on the alternator to see just what the alternator is doing. Is it delivering a good current? It will only deliver its rating 40 amps at high engine revs and into a load like your winch or lights. (not as battery charging) It is possible your alternator is tired/ faulty not delivering enough current.
To answer your question. The alternator has a power output. This comes via diodes from the stator winding and connects directly to the battery +ve via a safety switch. Current can not flow back into the alternator on this wire when engine is not running.
The negative of the alternator will be via the body of the alternator.
The remaining wire goes via a switch and warning lamp (3watt 12volt) to battery positive. This wire carries current into the alternator to provide initial excitation. The lamp will glow indicating current flow into the field coils. When the alternator starts to produce power internal diodes will generate its own excitation power and the lamp will go out. This wire must be disconnected with the switch when the engine is not in use as the current will flow lighting the lamp and discharging eventually the battery. This switch is often part of the ignition switch on petrol engine or called an ignition switch eroneously on a diesel.
There are many variations on alternators these seem to be the usual car alternator connections. Assuming it has an integral regulator.
good luck olewill
The alternator could be given a smaller pulley or a larger one on the engine to increase alternator RPM at idle. However you must accept that the alternator will run very fast at cruise RPM which may destroy it.
Before you fit another alternator you should fit an ampmeter either permanently or temporarily on the alternator to see just what the alternator is doing. Is it delivering a good current? It will only deliver its rating 40 amps at high engine revs and into a load like your winch or lights. (not as battery charging) It is possible your alternator is tired/ faulty not delivering enough current.
To answer your question. The alternator has a power output. This comes via diodes from the stator winding and connects directly to the battery +ve via a safety switch. Current can not flow back into the alternator on this wire when engine is not running.
The negative of the alternator will be via the body of the alternator.
The remaining wire goes via a switch and warning lamp (3watt 12volt) to battery positive. This wire carries current into the alternator to provide initial excitation. The lamp will glow indicating current flow into the field coils. When the alternator starts to produce power internal diodes will generate its own excitation power and the lamp will go out. This wire must be disconnected with the switch when the engine is not in use as the current will flow lighting the lamp and discharging eventually the battery. This switch is often part of the ignition switch on petrol engine or called an ignition switch eroneously on a diesel.
There are many variations on alternators these seem to be the usual car alternator connections. Assuming it has an integral regulator.
good luck olewill
fisherman
Well-Known Member
Sorry, the hauler is hydraulic off the engine, it's the fact that the engine is only running at low revs means the batteries start to drift down after a while, particularly at night with lights as well.
Smaller alternator pulley is not good, it tends to cripple the belts.
A second alternator has the added benefit of, well, a second alternator in case of failure.
Smaller alternator pulley is not good, it tends to cripple the belts.
A second alternator has the added benefit of, well, a second alternator in case of failure.
fisherman
Well-Known Member
[ QUOTE ]
Also sounds like the wiring might be a little substandad if he is loosing 1.5 volts. Clean all terminals or replace wires with heavier....
[/ QUOTE ]
Thought of that and doubled the wires, no different. Wiring is 70 amp, about 4 metres long. I did have some success by wiring the service bank direct to get past the loss in the diode (I think it was about 1 volt actually). Changing the Maxsea PC to a 24v psu instead of 240 helped as well.
I think I would have the original engine/control panel as supplied, with a completely separate service system, plus a 'bridge' switch. Complex automatic or manual switching systems are not good news:- this is a fishing boat where every action has an equal and opposite malfunction.
Also sounds like the wiring might be a little substandad if he is loosing 1.5 volts. Clean all terminals or replace wires with heavier....
[/ QUOTE ]
Thought of that and doubled the wires, no different. Wiring is 70 amp, about 4 metres long. I did have some success by wiring the service bank direct to get past the loss in the diode (I think it was about 1 volt actually). Changing the Maxsea PC to a 24v psu instead of 240 helped as well.
I think I would have the original engine/control panel as supplied, with a completely separate service system, plus a 'bridge' switch. Complex automatic or manual switching systems are not good news:- this is a fishing boat where every action has an equal and opposite malfunction.
VicS
Well-Known Member
[ QUOTE ]
Smaller alternator pulley is not good, it tends to cripple the belts
[/ QUOTE ] Larger engine pulley then?
Smaller alternator pulley is not good, it tends to cripple the belts
[/ QUOTE ] Larger engine pulley then?
fisherman
Well-Known Member
[ QUOTE ]
[ QUOTE ]
Smaller alternator pulley is not good, it tends to cripple the belts
[/ QUOTE ] Larger engine pulley then?
[/ QUOTE ]
Another set of problems there, plus over running the alternator at speed. I know of an installation using a AC9 alternator with a pulley the size of a cotton reel. Don't know if there's a connection (!) but there was a fire.
[ QUOTE ]
Smaller alternator pulley is not good, it tends to cripple the belts
[/ QUOTE ] Larger engine pulley then?
[/ QUOTE ]
Another set of problems there, plus over running the alternator at speed. I know of an installation using a AC9 alternator with a pulley the size of a cotton reel. Don't know if there's a connection (!) but there was a fire.
halcyon
Well-Known Member
A small bodge, get a battery isolator switch, and wire between the alternator input to the blocking diodes and the output to the service battery. You can now try by-passing the diode and volt drop, and connect the alternator direct to the service bank. Watch were the alternator sense comes from, if remote regulator it may be engine battery, if so swop to service bank. If sensing from engine bank this is not helping your current problem either, swopping over may well help.
It would be usefull to have some voltages though, batteries off load, on charge, and when hauling, also battery bank size.
Brian
It would be usefull to have some voltages though, batteries off load, on charge, and when hauling, also battery bank size.
Brian
fisherman
Well-Known Member
I've sent a PM. As above, I connected the service bank to the common on the diode and it helped. I checked all voltages with a multimeter, can't remember figures. Once the alternator is up to speed I can see the ammeter go to 30 amps or so then drop back to register the actual output as the batteries pick up. As I turn things on or off the ammeter goes up and down. It is between the diode and the battery bank. Similar on the start side.
VicS
Well-Known Member
[ QUOTE ]
over running the alternator at speed
[/ QUOTE ] I did draw attention to that when I suggested it earlier.
Anyway I answered your original question, which was how to wire the second alternator in my post that begins with the word "Simple" I do have reservations as to whether the two alternators system alone will solve your problems but what is wrong with the instructions I offered.
I answered your question, now get on and do it!
You cannot completely separate the two because both warning lights have really got to be supplied from the same "ignition" switch but you can fit the bridging switch between the battery banks if you wish.
over running the alternator at speed
[/ QUOTE ] I did draw attention to that when I suggested it earlier.
Anyway I answered your original question, which was how to wire the second alternator in my post that begins with the word "Simple" I do have reservations as to whether the two alternators system alone will solve your problems but what is wrong with the instructions I offered.
I answered your question, now get on and do it!
You cannot completely separate the two because both warning lights have really got to be supplied from the same "ignition" switch but you can fit the bridging switch between the battery banks if you wish.
