Balmar alternator fire

[goboatingnow]

Originally Posted by MerMike

I can offer some insight, having just installed 2 drop-in LFP batteries with a 100A Ample Power alternator. I also have the MC-614 with temperature sensor. It's bolted to the back of the alternator and AL1 was set for 90° C.

After an hour of motoring I took a thermographic image of the alternator and it was eye-opening. The hottest part of the alternator reads 246°F, well above the 90°C setting.



I've been told that temperature can break down semi-conductors.

I reduced the setting to 70° C and the temperatures lowered to a reasonable level.

My takeaway is that the Balmar temp sensor does work, but it's not necessarily measuring the hottest point in the alternator.

Yes this is interesting , realistically an externally mounted temp sensor needs serious derating to be equivalent to internal temperature. The thermal latency in the case can mean early on the internally are initially way hotter then the external surfaces.

[DeValency]

Originally Posted by s/v Jedi

I still have a bad feeling about the temperature sensor. OP confirms it has a sensor but not that it has a sensor on the alternator rather than the battery, connected to the correct pins on the regulator (for the alternator temp sensor rather than battery temp).

What is sure is that it failed. So there are two failures: whatever caused the fire and another one with the system that should have prevented it to escalate into actual flames.

This is around my thoughts here. I didn’t see in the former posts of the OP if:

- the alt temp sensor AND external regulator were replaced with the new alternator 1.5 years ago. If these are of the former alternator it may explain a repeated malfunction.

- not sure it is a good idea to charge the AGM starter battery from the LFP house bank, even with a dc-dc charger (that wouldn’t do much anyway in such setup except isolation, if it is an isolated dc-dc charger). We usually do it the other way around: from the starter AGM battery to the LFP via dc-dc charger - this is the safest way to eliminate any alternator overload.

- The battery isolator should also be checked for possible malfunction/partial shortcut… (I didn’t read if there is one?) - but also related to the charging schema: charge the LFP house and Starter SEPARATELY through the battery isolator (FET, not the lousy diode based) and use a DC-DC charger on the LFP line if you’re not 100% in trust of your programmable external regulator. Personally, I would always prefer a first line protection by limiting the alternator current output, regardless the external regulator.

- and finally, a poor insulation or something else creating a shortcut before the fuse could be the repeating cause for burning two alternators.

[In The Mood]

I would be loathe to write this off as a coincidence that you have two back to back alternator failures, both resulting in fires.

If there was a previous fire, were all the adjacent wiring and connectors checked when the first alternator was replaced? I assume the wire was properly sized, proper insulation temp (105c) and derated for use in an engine room. Also properly derated if it was bundled with other wires.

If this has happened twice, and given the demand on the alternator with lithium batteries, I would check or even replace all the wiring to the alternator. Excessive heat from both the latest and the previous incident could have unseen impact on wiring, connectors and even adjacent wiring.

If the Balmar regulator was present in the previous fire as well I would certainly inspect/replace the harness for this as damage may have occurred.

[CelestialMelody]

I would second a suggestion above, reach out to Balmar support. I gave found them to be very responsive.

[svkatface]

Happened to us. Belt was too tight. Also rigged blower to push air on alternator.

[BoatBumm]

Have you asked Balmar? I’ve found their technical assistance people to be VERY helpful when I’ve had issues with my Balmar systems.

[FPNC]

QUOTE: solar panels were pumping in ~40A. Net current draw from the batteries was between +30A and -10A during this window.... doesn't look like alternator ever produced anything, all power was coming from the solar panels. :QUOTE

Alternator regulators do not appreciate a second charge source. It can make the alternator detect an overcharge situation and it will shut down charging. Never run two charge sources at the same time.

Something to watch for: When you separate the battery banks and charging you can also inadvertently create a 'loop' in your 12 volt system that allows +12 volts from the 2 different sources to feed to the panel and other devices. Say one loop comes from the cranking battery and one loop from the house bank/alternator. If they meet at the same device the lower voltage +12 volt circuit can become a semi-ground and allow current to flow the wrong direction. While a light bulb does not care, other sensitive instruments do.

You have an external regulator. Make sure the excite wire to the Balmar alternator internal regulator is not connected.

Check that all your grounds are common and have excellent connections. The Balmar alternator needs to be grounded well.

Make sure the Balmar regulator and alternator are wired correctly. Don't trust the previous installer to have done it correctly. If you are burning the stator while the field has no power and alternator does not have output, you have a major wiring issue. Probably a ground.

[rslifkin]

Originally Posted by FPNC

Alternator regulators do not appreciate a second charge source. It can make the alternator detect an overcharge situation and it will shut down charging. Never run two charge sources at the same time.
.

Sorry, but this is absolutely wrong. The alternator will still regulate as designed with another charge source. It'll target a given voltage and if another source pushes the voltage above the set point the alternator just won't provide any power. It won't hurt the alternator.

FWIW, my boat runs with 2 alternators and solar all feeding the house bank simultaneously with no issues.

[goboatingnow]

Originally Posted by FPNC

.....

Alternator regulators do not appreciate a second charge source. It can make the alternator detect an overcharge situation and it will shut down charging. Never run two charge sources at the same time.

sorry just plain wrong , parallel charges sources simply supply current as a ratio of their respective output impedance ( as they are all imperfect voltage sources ) if the battery is at or below the alternator setpoint voltage the alternator will supply "some " current , if the setpoint rises above the alternator set point voltage the alternator will not supply current.

Something to watch for: When you separate the battery banks and charging you can also inadvertently create a 'loop' in your 12 volt system that allows +12 volts from the 2 different sources to feed to the panel and other devices. Say one loop comes from the cranking battery and one loop from the house bank/alternator. If they meet at the same device the lower voltage +12 volt circuit can become a semi-ground and allow current to flow the wrong direction. While a light bulb does not care, other sensitive instruments do.

what that's nonsense sorry , all charge sources inherently have a diode in their output circuit so that the battery cannot discharge into a charge source output

a commoned charge source only sees the battery voltage it cant be above or below the battery terminal voltage

[AMCarter3]

Have you called and talked to Balmar? I know they've been bought out, but also heard their tech support is still available.

[Boatwright]

100 deg C is way to high. At that temp the lacquer that coats the windings in your alternator starts to soften and over time will result in an internal short and alternator failure. The Sterling regulator system in our boat trips at 70 deg C.

One also needs to be careful when charging batteries that are down on voltage. If the engine is running at low RPM, the regulator system will increase the field voltage as needed to produce the asked for current. A good way to visualize this is trying to drive your stick-shift car in 4th gear at 20mph. At low RPM the cooling fan(s) in an alternator are not moving enough air. Also, an hot day and/or an hot engine space can make things worse.

We make a point of not turning on our high-output alternator system until we have run the engine for ~ 10 minutes. This brings the battery voltage up, and reduces the field current to a safer level.

As a routine, we never run in high-output mode at less than 1,500 engine RPM. Last week, the second mate started the engine with the high-output switch on (forgot to check). With the engine at idle as we prepared to leave our mooring, the alternator temp sensor tripped a few minutes later at 70 deg C. Notably, at that temp the alternator smelled hot and unhappy.

FYI: For those of us stuck in the Fahrenheit past: 100 deg C = 212 deg F; 70 deg C = 158 deg F. 158 deg is too hot to touch and according to the alternator folks a redline for alternator durability. In practice, we like to see the temp kept at 60 deg C or lower. Normally at 1,500 RPM it runs between 55 and 58 deg. -- cool and happy.

[Tyrosi]

I had a similar issue with my Balmar AT-165 and MC-614 regulator charging a similar sized LFP bank. I also had my alternator detuned to 70%. Your float V setting seems high to me. As I recall, I use 13.9/13.8/13.3. In my situation, the rectifier burned up but I did not see any flames.

The tech support guys at Balmar are great and I agree with others that you should give them a call. They walked my through some diagnostics and told me to lower the max alternator temp setting to below 90… I think they have an updated technical bulletin about this.

My alternator was professionally installed. When I went to remove he alternator I noticed that the screw holding the temp sensor to the alternator was loose. I suspect that this loose connection resulted in the temp sensor providing an incorrect reading to the regulator. Also, after I removed the alternator I noticed that several of the long case screws were backed out 1/4 inch and loose. Perhaps these loose screws contributed or caused the problem? When I took the alternator to a repair shop the technician told me that he thought the rectifier was not made properly… one of the soldered connections looked faulty to him.

I think there’s a reason why Balmar replaced the AT series with the XT series. The AT series didn’t handle the heat as well as the XT does. I will replace my AT with an XT when I get a chance. In the mean time, I installed an on/off switch for the regulator and very rarely turn it on since my solar panels do a good job of keeping the batteries charged during the day and the LFP bank can easily provide enough power through the night.

I hope this helps. Good luck.

[Tyrosi]

Here’s what the Balmar tech told me after our rectifier fried on our AT-165:
Monitor the alternator temperature and adjust the belt load manager to keep the temperature below 90C. Also, if possible, direct fresh air to the rear of the alternator.
The alternator pulls air from front and back and exits from middle.