Alternators Not Charging - Big Mystery to Me

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catalinajack

catalinajack

Guru
Joined
Nov 16, 2011
Messages
3,585
Location
USA
Vessel Name
Catalina Jack
Vessel Make
Defever 44
Here is what I have.

1. Two Lehman 120s, each with a 100 amp Balmar controlled with a Balmar regulator.
2. Two banks of four golf car batteries wired to a Off-Port-Starboard-Both switch.
3. Alternator output wired directly to each bank.
4. Output controlled by Balmar Centerfielder.

Here is what is happening.

1. Alternator output to each battery bank tested with Fluke clamp-on meter is around 70 amps each.
2. However, both my Victron BMV battery monitor and my Magnum Energy battery monitor, with the engines running of course, show a discharge of 60 amps, the house load. I would think with 70 amps x 2 going into the batteries, the monitors would show a net positive.
3. When I turn off all loads AC & DC), the monitor shows -0- with the engines off AND with both engines running.
4. With the engines off, the voltage is 12.7
5. With the engines on the voltage is 13.2.
6. When I switch to shore power and the charger comes on, the monitors both show a positive 125 amps, bulk charging.
7. Batteries at 65% SOC.

Gentlemen, any ideas? I am at a loss.
 
You say there’s 70 amps running to the batteries but it’s showing a 60 amp loss. Where are the shunts measuring the current? What path does the alternator send its current to the batteries?
 
No great insights (electrics are not my strength), but a couple questions just to understand what you are seeing:

1. 12.7v at-rest. For FLA, this is close to fully-charged, no? The Trojan T105 spec-sheet shows 6.37v as 100% (12.74v for series-pair). Not sure why the SoC is showing 65% unless the initial parameters were not input correctly.

2. Has something changed? Has this system been in place for a while and is now operating differently?

3. On Shore Power, how long does Bulk Charge/125A persist before going to Float? Are you seeing close to 15V in Bulk?

I hate issues like this. I once delivered a boat from San Diego to Ilwaco (Columbia River) and had to stop in Oxnard to troubleshoot a wonky charging system. Never did get it figured out.

Good luck - following with interest.

Peter
 
Are there two shunts? Exactly where are they? There should be one and only one cable on the battery, going to the shunt. Everything else should be on the other side of the shunt. You say:

3. Alternator output wired directly to each bank.
Click to expand...

If that is correct, and they are not wired through the shunts, then you will not see their charge current on the battery monitors.
 
****3. Alternator output wired directly to each bank.**** Are the shunts wired so ALL the current, to and from each bank MUST go through them. A common fault is missing some of the loads so they don't register either discharging or recharging.
THe Exception would be the starter motor circuit. Not normal to wire the starter motor through the shunts due to the very heavy load and the very short time needed..


****2. However, both my Victron BMV battery monitor and my Magnum Energy battery monitor, with the engines running of course, show a discharge of 60 amps, the house load. I would think with 70 amps x 2 going into the batteries, the monitors would show a net positive.**** Per above if there is a problem with the shunt being bypassed then I can see this happening. THey are picking up the discharge but missing the recharge so not showing the 10 amp actual charge rate.

Any wiring that goes directly to the battery neg. is a bypass of the shunt and a bypass preventing the monitor from taking into account the difference between the discharge and the recharge currents. Again ignoring the starter motor circuit.


One other thing that occurred to me as typing this is how are the engines grounded? If a lot of the loads are tied to the engines they may be using the engine/starter as a bypass. Use you clamp meter on the engine grounds to check for this. THere might be a wee bit of current but it should not be carrying very much. Normally in this case only the engine related sensors for the guages and such engine only related currents.

Start with that to ensure the shunts are being used correctly and the engine grounds are not being used as a bypass to the shunts.
 
I agree that it sounds like the alternator current is bypassing the BVM and Magnum shunts. If the alternators share the engine's negative, or the starter negative, it is likely bypassing the shunts.
 
7. Batteries at 65% SOC.

As said if the standing voltage is around 12.7 the battery is fully charged.
Did you just notice this or did this start after you worked on the charging circuit?
I agree if the alternator charge is going directly to the battery it is feeding info to the shunts in reverse and the 60 amp is net discharge after the battery takes 10 amp.
 
You can learn a lot if you put a DC clamp meter on the cabling from the alternators. That will tell us with certainty that the alternators are working. But I agree with C-lectric and others. Somehow the alternator outputs are bypassing the shunts.

Jim
 
JDCAVE said:
You can learn a lot if you put a DC clamp meter on the cabling from the alternators. That will tell us with certainty that the alternators are working. But I agree with C-lectric and others. Somehow the alternator outputs are bypassing the shunts.

Jim
Click to expand...
Agree... the 13.2V with engines running also sounds suspect / low. Alt output should be around 14.2V?
 
twistedtree said:
I agree that it sounds like the alternator current is bypassing the BVM and Magnum shunts. If the alternators share the engine's negative, or the starter negative, it is likely bypassing the shunts.
Click to expand...
TT, and others, the answer may, indeed, be the alternator negative wiring. I failed to mention that they are wired directly to the battery banks. Thoughts?
 
C lectric said:
****3. Alternator output wired directly to each bank.**** Are the shunts wired so ALL the current, to and from each bank MUST go through them. A common fault is missing some of the loads so they don't register either discharging or recharging.

THe Exception would be the starter motor circuit. Not normal to wire the starter motor through the shunts due to the very heavy load and the very short time needed..





****2. However, both my Victron BMV battery monitor and my Magnum Energy battery monitor, with the engines running of course, show a discharge of 60 amps, the house load. I would think with 70 amps x 2 going into the batteries, the monitors would show a net positive.**** Per above if there is a problem with the shunt being bypassed then I can see this happening. THey are picking up the discharge but missing the recharge so not showing the 10 amp actual charge rate.



Any wiring that goes directly to the battery neg. is a bypass of the shunt and a bypass preventing the monitor from taking into account the difference between the discharge and the recharge currents. Again ignoring the starter motor circuit.





One other thing that occurred to me as typing this is how are the engines grounded? If a lot of the loads are tied to the engines they may be using the engine/starter as a bypass. Use you clamp meter on the engine grounds to check for this. THere might be a wee bit of current but it should not be carrying very much. Normally in this case only the engine related sensors for the guages and such engine only related currents.



Start with that to ensure the shunts are being used correctly and the engine grounds are not being used as a bypass to the shunts.
Click to expand...

As to "Any wiring that goes directly to the battery neg. is a bypass of the shunt and a bypass preventing the monitor from taking into account the difference between the discharge and the recharge currents. Again ignoring the starter motor circuit.", I should have noted that I changed the alternator gronds to run directly to the battery banks. Formerly, they were wired to the engines.

If this is the problem to where should I ground the alternators?
 
As others mentioned if they don't go to a buss bar or power post and one wire through the shunt to batty Neg it won't get counted by the shunt/monitor.
Multi Neg cables are usually run to a buss bar with one cable to shunt and them to batty Neg.
 
With the battery monitor shunt installed, you need to pretend the battery's negative terminal doesn't exist anymore. The battery gets connected to the shunt. Period (starter motor negative could be the only exception). All other connections go to the shunt including your alternators. Connecting anything directly to the battery defeats the purpose of the battery monitor's shunt.
 
I have a somewhat tangential question on installing a shunt - in a camper-van vs a boat. For automotive installations, many/most accessories are grounded to the nearest chassis ground, not back to the negative post on the battery (though the battery is also grounded to nearby chassis ground).

If the shunt is installed on negative cable near house battery, would the chassis-ground accessories bypass the shunt? Or is it all one happy circuit despite the chassis grounded appliances?

Thanks in advance (as I said, not my strong suit).

Peter
 
mvweebles said:
I have a somewhat tangential question on installing a shunt - in a camper-van vs a boat. For automotive installations, many/most accessories are grounded to the nearest chassis ground, not back to the negative post on the battery (though the battery is also grounded to nearby chassis ground).

If the shunt is installed on negative cable near house battery, would the chassis-ground accessories bypass the shunt?

Thanks in advance (as I said, not my strong suit).

Peter
Click to expand...


If it does not go through the shunt -- it has bypassed the shunt.
 
mvweebles said:
I have a somewhat tangential question on installing a shunt - in a camper-van vs a boat. For automotive installations, many/most accessories are grounded to the nearest chassis ground, not back to the negative post on the battery (though the battery is also grounded to nearby chassis ground).

If the shunt is installed on negative cable near house battery, would the chassis-ground accessories bypass the shunt? Or is it all one happy circuit despite the chassis grounded appliances?

Thanks in advance (as I said, not my strong suit).

Peter
Click to expand...

In that case, you connect the battery to the shunt and the shunt to the negative cables that go to the vehicle. It's always the same, battery to shunt, shunt to vehicle/boat/fusebox/anything. Nothing connects to the negative terminal of the battery except the shunt. If the battery is also driving a starter that can be an issue and the solutions vary depending on your particular starter and shunt.
 
sbman said:
In that case, you connect the battery to the shunt and the shunt to the negative cables that go to the vehicle. It's always the same, battery to shunt, shunt to vehicle/boat/fusebox/anything. Nothing connects to the negative terminal of the battery except the shunt. If the battery is also driving a starter that can be an issue and the solutions vary depending on your particular starter and shunt.
Click to expand...
Up in #11, OP states

"I changed the alternator gronds to run directly to the battery banks. Formerly, they were wired to the engines"

If he returns alternator grounds to the engine, would be on the "other side" of the shunt, correct? Similar to my chassis ground? Thinking a out it, not sure how you'd isolate an alternator to permit moving ground, but so be it.

Thanks for bearing with me. Thread has been very helpful.

Peter
 
catalinajack said:
As to "Any wiring that goes directly to the battery neg. is a bypass of the shunt and a bypass preventing the monitor from taking into account the difference between the discharge and the recharge currents. Again ignoring the starter motor circuit.", I should have noted that I changed the alternator gronds to run directly to the battery banks. Formerly, they were wired to the engines.

If this is the problem to where should I ground the alternators?
Click to expand...

I did not know there are alternators that have a negative ground post. All I have seen ground to the engine body. However a ground wire can be added to a mounting post bolt to enhance/ensure the negative has a solid connection.

You have bypassed the shunt, there is your problem. As I said earlier the shunt is now sensing power in reverse direction thinking it is coming from battery, when it is from alternator directly. (actually also through engine block the shunt must be getting confused)
Move that wire to other side of shunt.
 
mvweebles said:
Up in #11, OP states

"I changed the alternator gronds to run directly to the battery banks. Formerly, they were wired to the engines"

If he returns alternator grounds to the engine, would be on the "other side" of the shunt, correct? Similar to my chassis ground? Thinking a out it, not sure how you'd isolate an alternator to permit moving ground, but so be it.

Thanks for bearing with me. Thread has been very helpful.

Peter
Click to expand...

Some alternators have a separate ground with their own ground terminal, some starters are made that way as well, the units on my Detroit are both setup that way. This makes it easy to hook up the grounds as needed instead of having to setup everything to flow through the engine block.
 
Every last one of you were correct. I moved the alternator grounds to the negative busbar AFTER the shunts. Monitors now show current from the alternators to the batterries. THANKS!
 
catalinajack said:
Every last one of you were correct. I moved the alternator grounds to the negative busbar AFTER the shunts. Monitors now show current from the alternators to the batterries. THANKS!
Click to expand...
Do you also now see 14+V when charging / alt running?
 
Bacchus said:
Do you also now see 14+V when charging / alt running?
Click to expand...
I discharged overnight while at the dock down to 55%. Started engines. Alternators charged at 100 amps (combined) at 1,000 engine RPM. Voltage at 12.9. Batteries began taking a charge immediately. Turned off engines and went to shore power. Charger putting out 125 amps, 13 volts. Since both charge sources are charging at virtually the same voltage, I believe all is well. Alternator output voltage should ramp up over time during the bulk charging period but I won't know for certain until we go out for an extended cruise.
 
Yesterday morning my house battery was at 12.1 before engines started for a 3 hour trip. The graph shows alternator charging at 13.3-13.4 during this time. Amp started 60, dropped to 30 (this not graphed, just observed).
On shore power the inverter charger was 13.7-14.2 (fridge/freezer load on).
The charger is 3 stage before it goes to float at 13.5 which is what it is doing this morning.
 
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