After a week or so of inactivity my house batteries (two T-105's, less than 6-mo old), had 12.74 volts, and the cranking battery, (marine battery, 2+ years old), had 12.74 volts remaining. After cranking up the little yanmar, (2QM20H), I let it warm up at idle for 20 minutes and as usual the alternator was almost too hot to leave my hand on.... Upon checking the volts the house and cranking had 13.34 and 12.92 volts, respectively. The unit came with a high-output alternator, (90-amps output on a bench last year) and has a small diode installed on the brown wire, (sensor wire?). Is it possible that the thing is stuck on 'full on' and doesn't know enough to shut off? It has an internal regulator. What is the diode for? What can make a regulator go bad?....help. Will be taking it to a shop for another check-up, I guess....but it'd be nice to know what to expect the prognosis to be. (nothing found in the archives regarding 'overcharging'.) Hydrometer readings were generally consistant from cell to cell.
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Maybe you need an external regulator?
Most high output alternators use an external multi-step regulator. Usually internal regulators just set the output voltage. Also - can you check which battery bank is taking the heavy current?
Most high output alternators use an external multi-step regulator. Usually internal regulators just set the output voltage. Also - can you check which battery bank is taking the heavy current?
One thing...
When your alt is charging, it is common for the volt meter to exceed 13 volts. And once it is shut off will slowly drop to the "normal" voltage level of +/- 12.62 volts. The fact that the alternator is "hot to the touch" concerns me. I think you are correct to have it bench tested again. There may be some friction inside the alt causing it to get hot. It may eventually burn out and not charge at all.
When your alt is charging, it is common for the volt meter to exceed 13 volts. And once it is shut off will slowly drop to the "normal" voltage level of +/- 12.62 volts. The fact that the alternator is "hot to the touch" concerns me. I think you are correct to have it bench tested again. There may be some friction inside the alt causing it to get hot. It may eventually burn out and not charge at all.
Hot Potato
Paul, a high output alternator will typically run hot(too hot to touch) if it is putting out anything near max output.
Paul, a high output alternator will typically run hot(too hot to touch) if it is putting out anything near max output.
Overcharge Cont.
I SAY that it is internally regulated because that is what the shop proprietor said.....not because I know that for fact. If that is not the case....wouldn't I be cooking both banks all the time with no external regulator? The output goes from alternator to an isolator input terminal and then to both banks at once. (Will be carrying some distilled water soon to top 'em off...) Will also be getting a second opinion from another shop.
I SAY that it is internally regulated because that is what the shop proprietor said.....not because I know that for fact. If that is not the case....wouldn't I be cooking both banks all the time with no external regulator? The output goes from alternator to an isolator input terminal and then to both banks at once. (Will be carrying some distilled water soon to top 'em off...) Will also be getting a second opinion from another shop.
Alternator Size
Dale A 90 amp alternator feeding a 225 amp house bank seems a bit large for the load. Trojans are wet cells. Recommendations are for sizing the alternator amps at about 25% of the house bank amp hours for wet cells. Gel cells, which can accept more input, could go up to 40%. Also sounds like the regulator for the alternator is whacked. You should determine for sure if you have an external or internal regulator (in addition to "what someone told you"). That should be easy - trace the wires coming off the alternator. Where do they go? If they just go to the isolator and then the batteries, without anything in between, it would seem to be internal, in which case you have a different problem, whether it's working or not. Internal regulators are like ferroresonant chargers, they will eat your batteries alive. This is because they taper charge the batteries rather than using the smart three stage regimen. If so, you should serriously consider your need to invest in a smart three stage regulator, like Xantrex, Balmar, etc. All of the newer external regulators have a wiring harness from the back of the alternator to the regulator. Do you have one, or just the outgoing charging wire and a field wire? If your batteries were over 13.5 v after running your engine at idle for only 20 minutes, you need to consider first what the output voltage of the alternator was (it could be way too high), and also consider that when you're at cruising speed, the alternator will be going even faster. You really need to have it checked out. Another thing to consider is adding two more Trojans to get up to 440 amp hours on your house bank, in which case the alternator would be correctly sized for the house bank. Last thing is if you have isolators, get rid of them. All they do is reduce the actual charge getting to your batteries by at least a half a volt. Either use the battery switch smartly when charging or get either a combiner or echo charge unit, neither of which looses any appreciable charge (voltage) between the charging source and your batteries. Whatever investment you make in your charging equipment will be paid back almost instantly - looked at the price of batteries lately
? Good luck, keep us posted. Stu
Dale A 90 amp alternator feeding a 225 amp house bank seems a bit large for the load. Trojans are wet cells. Recommendations are for sizing the alternator amps at about 25% of the house bank amp hours for wet cells. Gel cells, which can accept more input, could go up to 40%. Also sounds like the regulator for the alternator is whacked. You should determine for sure if you have an external or internal regulator (in addition to "what someone told you"). That should be easy - trace the wires coming off the alternator. Where do they go? If they just go to the isolator and then the batteries, without anything in between, it would seem to be internal, in which case you have a different problem, whether it's working or not. Internal regulators are like ferroresonant chargers, they will eat your batteries alive. This is because they taper charge the batteries rather than using the smart three stage regimen. If so, you should serriously consider your need to invest in a smart three stage regulator, like Xantrex, Balmar, etc. All of the newer external regulators have a wiring harness from the back of the alternator to the regulator. Do you have one, or just the outgoing charging wire and a field wire? If your batteries were over 13.5 v after running your engine at idle for only 20 minutes, you need to consider first what the output voltage of the alternator was (it could be way too high), and also consider that when you're at cruising speed, the alternator will be going even faster. You really need to have it checked out. Another thing to consider is adding two more Trojans to get up to 440 amp hours on your house bank, in which case the alternator would be correctly sized for the house bank. Last thing is if you have isolators, get rid of them. All they do is reduce the actual charge getting to your batteries by at least a half a volt. Either use the battery switch smartly when charging or get either a combiner or echo charge unit, neither of which looses any appreciable charge (voltage) between the charging source and your batteries. Whatever investment you make in your charging equipment will be paid back almost instantly - looked at the price of batteries lately
? Good luck, keep us posted. StuSounds normal.
Unless you are cooking the water out of the batteries or voltage measured at the batteries with the engine running is over about 14.2 volts, I wouldn't worry about it. It is normal for a battery to show a higher voltage right after a charging source has been removed. Let it sit for an hour or put a small load on it for a few minutes, then check it.
Unless you are cooking the water out of the batteries or voltage measured at the batteries with the engine running is over about 14.2 volts, I wouldn't worry about it. It is normal for a battery to show a higher voltage right after a charging source has been removed. Let it sit for an hour or put a small load on it for a few minutes, then check it.
float voltage
I've understood the charging cycle to go as follows; when the engine first starts the alt. puts out a lot of juice than after the batteries are charged (time will depend on how low the voltage is) the alt. will lower its voltage to a float voltage. For this to occur you will need some type of voltage regulator, either internal or external. I have an older Balmer regulater with a Lestec high output alt. and with my regulater I have the ability to adjust the voltage with a small screw driver. When my banks are really low my initial 20 minutes or so (I've never actually timed it) will be around 13.8 - 14.0 volts.
I've understood the charging cycle to go as follows; when the engine first starts the alt. puts out a lot of juice than after the batteries are charged (time will depend on how low the voltage is) the alt. will lower its voltage to a float voltage. For this to occur you will need some type of voltage regulator, either internal or external. I have an older Balmer regulater with a Lestec high output alt. and with my regulater I have the ability to adjust the voltage with a small screw driver. When my banks are really low my initial 20 minutes or so (I've never actually timed it) will be around 13.8 - 14.0 volts.
Measure Current
Dale, What you really need to do is to measure the charging current into each battery. You will need to insert a shunt into the +ve lead to the battery and connect a meter across it. Make sure the engine is not running when you do this. Having measured one battery charge current repeat for the other. The voltages you report seem quite normal for batteries on charge and these could be the result of quite low charge rates of only an amp or so. It is a fair bet that if a previous owner went to the trouble and expense of fitting a high output alternator then you probably have a smart external regulator too. Look for an unusual box in the engine compartment with a name not Yanmar. Further you probably have a diode splitter in line with each battery. If the regulator does not have a voltage sensing wire to the house battery then the alternator's output will never attain sufficient voltage to fully charge the batteries. An old dodge is to fit a small diode in series with the voltage sense lead to kid the alternator that the battery volts are 0.7 V low and so it increases its output to compensate. This is exactly the voltage lost in the diode splitter so all should be well again. However, if this diode in the sense wire is the wrong way round then the alternator will bust its gut trying to charge the batteries, but the voltages will probably be in excess of 15 volts then and this is not good. Also the diode splitter will be very hot to touch too. This diode needs to be connected with its Anode on the +ve side of the diode splitter and its cathode towards the regulator. You may be able to see an arrow like symbol and this should point towards the alternator/regulator. It is normal for an alternator to run hot - particularly the high output ones. They are designed to operate in a hot engine space and will also pick up heat from the engine as well as internally. I would expect a case temperature of 85 - 90 degrees Celsius (185 - 195 F).
Dale, What you really need to do is to measure the charging current into each battery. You will need to insert a shunt into the +ve lead to the battery and connect a meter across it. Make sure the engine is not running when you do this. Having measured one battery charge current repeat for the other. The voltages you report seem quite normal for batteries on charge and these could be the result of quite low charge rates of only an amp or so. It is a fair bet that if a previous owner went to the trouble and expense of fitting a high output alternator then you probably have a smart external regulator too. Look for an unusual box in the engine compartment with a name not Yanmar. Further you probably have a diode splitter in line with each battery. If the regulator does not have a voltage sensing wire to the house battery then the alternator's output will never attain sufficient voltage to fully charge the batteries. An old dodge is to fit a small diode in series with the voltage sense lead to kid the alternator that the battery volts are 0.7 V low and so it increases its output to compensate. This is exactly the voltage lost in the diode splitter so all should be well again. However, if this diode in the sense wire is the wrong way round then the alternator will bust its gut trying to charge the batteries, but the voltages will probably be in excess of 15 volts then and this is not good. Also the diode splitter will be very hot to touch too. This diode needs to be connected with its Anode on the +ve side of the diode splitter and its cathode towards the regulator. You may be able to see an arrow like symbol and this should point towards the alternator/regulator. It is normal for an alternator to run hot - particularly the high output ones. They are designed to operate in a hot engine space and will also pick up heat from the engine as well as internally. I would expect a case temperature of 85 - 90 degrees Celsius (185 - 195 F).
D. Alexander
...not sure how to or where I'd come up with a shunt.... but here is other info. I previously recorded the voltages across battery terminals while idling and found both between 13.6 and 14.2 volts....not TOO high, I would think. This is after going through a battery isolator. If the previous owner had installed some nature of smart charge system it went the way of the trash bin when the yard stripped the wiring from the boat after a lightning strike....(a pre-purchase thing for me). There is one small diode in a brown wire which I have as a 'hot only with ignition' line...comes hot with the key 'on'. I understood that it was an 'exciter' thing...without which the alternator wouldn't....like, 'prime' the electrical pump, so to speak, and start generating current. It is not in the sense wire as I see it. Can you have these things reversed and not do large amounts of damage to things? My red 'sense wire' is run from alternator to the (house) battery side of the battery isolator... and as such should 'sense'. It may be that all is really well with the charging system. It was simply the heat of the alternator that got me concerned. It always starts and the batteries seem to charge up....hopefully not too much.
...not sure how to or where I'd come up with a shunt.... but here is other info. I previously recorded the voltages across battery terminals while idling and found both between 13.6 and 14.2 volts....not TOO high, I would think. This is after going through a battery isolator. If the previous owner had installed some nature of smart charge system it went the way of the trash bin when the yard stripped the wiring from the boat after a lightning strike....(a pre-purchase thing for me). There is one small diode in a brown wire which I have as a 'hot only with ignition' line...comes hot with the key 'on'. I understood that it was an 'exciter' thing...without which the alternator wouldn't....like, 'prime' the electrical pump, so to speak, and start generating current. It is not in the sense wire as I see it. Can you have these things reversed and not do large amounts of damage to things? My red 'sense wire' is run from alternator to the (house) battery side of the battery isolator... and as such should 'sense'. It may be that all is really well with the charging system. It was simply the heat of the alternator that got me concerned. It always starts and the batteries seem to charge up....hopefully not too much.
Dale
Understand your last. Best way to check for excessive charging currents is to buy one of those clip on ammeters sold in auto parts stores. They are all plastic and have a clip which fits over the lead to the battery, no need to disconnect anything. They are very cheap and horribly inaccurate, but they can always detect currents of a couple of amps or more- and this is all you really need to know to decide whether your system is in runaway mode. I would guess it is probably okay, but if you are still worried you will need a professional to check it out. I mean a "professional" not some helpful electrician guy from the yard. Good luck. Don.
Understand your last. Best way to check for excessive charging currents is to buy one of those clip on ammeters sold in auto parts stores. They are all plastic and have a clip which fits over the lead to the battery, no need to disconnect anything. They are very cheap and horribly inaccurate, but they can always detect currents of a couple of amps or more- and this is all you really need to know to decide whether your system is in runaway mode. I would guess it is probably okay, but if you are still worried you will need a professional to check it out. I mean a "professional" not some helpful electrician guy from the yard. Good luck. Don.
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