Alternator temperatures

[mermike]

I recently replaced my 2 Firefly Oasis 100 AH batteries with a pair of Battleborn 100 A batteries. They are both a Group 31 size, so they literally dropped right in.

The Firefly batteries are 2 years old and were only providing about 50 AH of useful capacity, despite several attempts at reconditioning. I’m a bit disappointed, needless to say.

I have a Balmar MC-614 voltage regulator with a Balmar temperature probe bolted to the Ample Power 105 A alternator terminal. I also have a second temperature probe bolted to the same terminal and connected to my Victron Venus GX. This allows me to record and chart alternator temperatures while under way.

When I installed the Battleborns, I also changed the programming on the MC-614. I modified the battery profile to LFP, and set A1c to 10 to provide 30 minutes of absorption per battery, per the Battleborn recommendations. I left BEL (belt manager) at 5, which is where it was set for the Fireflys.

We headed off to the San Juans, where the winds were light as expected. The Yamnar was turning 2400 RPM. The Venus was reporting the alternator temperature as 175°. On a whim, I decided to check the alternator with my new toy, a Flir C5 thermal imaging camera. Here’s what I found:

Maximum temperature in the image is 245°F. Yikes. I reduced RPM and continued motoring. The Venus was still reporting 175° so I continued at around 1200 RPM and the alternator cooled down. Once at anchor, I programmed BEL to 6 and reduced AL1 (Alternator Temperature) from 90°C to 70°C. This was the result during subsequent motoring:

I didn’t quite align the bullseye, but the hottest point is no longer the alternator. The alternator was still putting out 60 amps, which is more than adequate.

It would be easy to jump to a conclusion and say that my new toy saved me from buying a new alternator. However, I’d like to know when alternator temperature is measured, where is it measured from? Balmar’s probe was mounted per the instructions, and the A1c default is 100°C. Is there an assumption that the probe will be cooler that the internals? Is an internal temperature of 245° at the hottest point destructive?

Mike

 

[dlochner]

The temp probe measures the temperature at the connection point, which may vary based on the alternator. The Balmar alternator I have has a dedicated mounting point on the side of the case.

 

[Rich Stidger]

@dlochner is correct. The temp probe will only measure at the connection point. Internal temperatures are higher, and depending upon the thermal resistance between the Balmar connection point and the rectifying diode junctions, the junction temperatures can be much higher.

IIRC, anything over 245-250 F will destroy semiconductor junctions. I would shoot for a case temp of no more than 175 F.

 

[mermike]

Thanks for the replies. While I understand where temp is measured, I don't understand the specifics of the effects of temperature. Rich's comment addresses that question. If Balmar measures temperature at the terminal and uses a default of 100 C, then I would assume that a higher internal temperature is normal. When I measured 175F at the terminal, the internal temperature was 70F higher. Destructively high, or far too close to it, at least.

 

[tfox2069]

"The Firefly batteries are 2 years old and were only providing about 50 AH of useful capacity, despite several attempts at reconditioning. I’m a bit disappointed, needless to say. "

Another dissatisfied customer. I share your disappointment on the Fireflies. I have one that is still "good" that I'll give away to anyone wanting it in the Annapolis, MD area. You pick up. The other two are toast, like yours. I've moved back to conventional AGMs.

 

[heritage]

I see your point about the case temperature reading might not be a good indicator of potential damaging higher internal temperature. I also have a Balmar mc-614 with the temperature sensor attached to the alternator case. Looking at your IR pictures, it appears that the hottest spot is from the windings and not so hot in the rear of the alternator where the diodes are located. So, I'm guessing that the windings can withstand the high temps that you are seeing.

 

[mermike]

Heritage, that's the question in a nutshell, but better stated. I'll check with Balmar tech support and see what they say, although it's not their alternator.

 

[Hayden Watson]

I have the same alternator but have 560Ah of LFP so will have much longer run times at full charge. I installed two 0.5ohm 100W resistors in series with the field wire and that reduced the output to 60A. At this level I could not find any place on it that showed more than 190ºF with my infrared thermometer, but your Flir would do a better job.
I need to improve my circulation in the engine compartment because I recently added sound-damping which is making the engine compartment much warmer. I am planning to re-route the blower so that it pulls air directly from the front of the alternator right off the fan blades. I am also looking for someplace I can take the alternator to get it rebuilt with new bearings and brushes. It has served me well for over 25 years and I want it to keep going as long as possible.

 

[heritage]

Heritage, that's the question in a nutshell, but better stated. I'll check with Balmar tech support and see what they say, although it's not their alternator.

Let us know what Balmer's response is. Make sure you include the flir image in an email to them.

 

[Maine Sail]

Temp sensor should be measuring as close to the stator as possible. A large hose clamp can hold it right to the stator core..

The Hitach alt on the left totally melted down however it has an internal reg so there is not much you can do to protect it . Pay attention to the B+plastic isolator @ 9:00 and the B- isolators 5:30 & 6:30. They are not melted despite the stator being completely cooked. For the Ample on the right you can see a brand new stator (left) and one cooked (right) by charging an LFP bank without adequate temp protection.

 

[Maine Sail]

Temp sensor should be measuring as close to the stator as possible. A large hose clamp can hold it right to the stator core..

Be careful reducing RPM to deal with heat. It can often have the opposite effect Because high RPM equates to a higher fan speed.

 

[Hayden Watson]

Temp sensor should be measuring as close to the stator as possible. A large hose clamp can hold it right to the stator core..

Thanks Rod. I was planning to install the thermistor to my alternator by using a metal P-clip to hold it and place that over the washer on the Bat+ output terminal on alternator. I figured that this should be connected to a heavy copper conductor coming straight from the core of the alternator. Would clamping it to the side of the case be more accurate that my idea? I was planning to do this install in the next week or two so your comment is very timely.

 

[Maine Sail]

Thanks Rod. I was planning to install the thermistor to my alternator by using a metal P-clip to hold it and place that over the washer on the Bat+ output terminal on alternator. I figured that this should be connected to a heavy copper conductor coming straight from the core of the alternator. Would clamping it to the side of the case be more accurate that my idea? I was planning to do this install in the next week or two so your comment is very timely.

B+ is only connected to the + side of the rectifier there is no connection to the stator.While the rectifier gets hot measuring stator temp is what will protect your alt

 

[Hayden Watson]

B+ is only connected to the + side of the rectifier there is no connection to the stator.While the rectifier gets hot measuring stator temp is what will protect your alt

Thanks Rod. I will change my plan. just to be clear, you are saying that I should use a hose clamp large enough to fully encircle the alternator body (approx 9"ø) to clamp the thermistor to the side of the case, correct? Is there any location that is better than others or just where I can get it into good contact?

 

[Hayden Watson]

B+ is only connected to the + side of the rectifier there is no connection to the stator. While the rectifier gets hot measuring stator temp is what will protect your alt

Hi Rod.
In the past you have said that on my Ample Power 105 I should limit the case temperature to100ºC. I have a friend who just got a Flir camera so I can now check the internal temperature as in addition to the case mounted thermistor. I have seen videos that show the internal temperature much higher than the case temperature. Any recommendations as to what internal temperature would be safe for the Ample Power alternator?

 

[mermike]

My Balmar was set to 90°C. I shot a picture of my Ample 105 with my Flir C5 which showed over 240°F in the center section. I reduced the setting to 60°C, which reduced the center temperature to around 170°F. I continuously record the temperature with my Victron Venus and it doesn't exceed 150°F at the binding post.

 

[Hayden Watson]

I have been doing some research on the temperatures that the windings insulation can tolerate as well as the solder. The typical 60/40 electrolic solder melts at 180ºC / 360ºF.
Windings wire comes in four classes.

• Class A - 100ºC with a hot spot max of 105ºC (212ºF / 221ºF)
• Class B - 120ºC with a hot spot max of 130ºC (248ºF / 266ºF)
• Class F - 145ºC with a hot spot max of 155ºC (293ºF / 331ºF)
• Class H - 165ºC with a hot spot max of 180ºC (329ºF / 356ºF)

The article that I read indicates that the most common winding class is class F. I would assume given that the Ample Power alternators were advertised as "hot rated" that they probably have class F or H. Given that, when I look at the running alternator with the Flir, as long as the hottest spot inside is not more than 140ºC / 285ºF, it should be fine.
I plan to use that info to help determine the best case temperature to set the regulator to.

 

[Hello Below]

as long as the hottest spot inside is not more than 140ºC / 185ºF, it should be fine.

You mean 140ºC / 285ºF

 

[Hayden Watson]

You mean 140ºC / 285ºF

D'oh! corrected.
My plan is to use the Flir to see the max core temperatures and let that help me to determine the external case temperature that I set as my max which the digital thermostat will use to cut the field current so that the alternator can cool down.

 

[MikeHoncho]

TICs (thermal imaging cameras) are notorious for being way off on the temps represented by the cross hairs. Follow up your concerns with a quality infrared heat gun and follow the directions on accuracy and distance from the target. I’m not saying yours is wrong (Flir is a good one) but confirm your concerns. I would never jump to a final conclusion with one but I would further investigate with more accurate equipment.