On my fourth alternator....??

In the past, I was using a second battery in Grand Cherokee WG. These are known to have not the most reliable charging system. To avoid overloading the alternator I've calculated the proper wire size to limit the charging current with a fully empty 2nd battery to 20A.

This would be a lot easier to achieve with a LiFePo4 battery. So just calculate the required voltage drop, then the wire size at the desired max current and you'll be good to go. The disadvantage is the lack of control over the charging current. As the 2nd battery gets charged the charging current will drop significantly. To work around this I used a step-up converter that supported CC/CV settings. In Aliexpress two 10A step-up CC/CV converters were like $20 with shipping included.

I run lithoum house batteries and agm starter
My trial and error has taught me this...
No lithium Iron is drop in on a boat, and almost none can be used as a starting battery, those that can are super expensive.
Fuses are a must
3 choices:
Victron DC-DC charger is the best
Renogy 20A & 40A chargers are cheap but not moisture proof
Xantrex echo charger is good if 18A is enough for you, this option is rarely mentioned but a good one.
Most outboards especially older ones only output like 35-65 Amps so a 40A or 60A charger is too much in my case.
Put down a rubber mat to help absorb shock. Lifepo4 batteries have boards inside that don't do well with being hit for 8 hours at a time.

Even though my 160A alternator seems fine (so far) to charge the lithium battery at 40A, I'd like know how much hotter than normal it gets. I had considered using a non-contact thermometer to measure surface temp after charging at full load, but I think mounting a thermocouple and reading real-time might be better.

My multimeter came with this style

but I'll try one of these

Should screw mount to the surface to optimise heat transfer. Anybody else tried such a method?

This video has some good info on the subject:

Maxter said:

This video has some good info on the subject:

Click to expand...

Thanks for posting; trying to learn all I can on this stuff.

Maxter said:

This video has some good info on the subject:

Click to expand...

Sadly, Clark has little clue what he is talking about in regards to the ABYC. Manufacturers do not run the show nor do they write the standards.

The #1 failure of Alt’s we have seen with LFP is Heat damage, then diodes..(ex marine alternator manufacturer) Alts like those tiny Hitachi’s try to self protect by reducing charge voltage as they heat up. This often result in almost no charging at all However, if you are routinely cycling to 80 or 90% DoD then they can cook pretty easily.

The worst thing you can do to a stock alt is to improve upon the crappy factory wiring. It is loaded with voltage drop which is also helping to protect a stock alt.

Best way to protect against heat damage is an external regulator such as Balmar or Wakespeed. Balmar also makes an excellent “Alternator Protection Module” which deals with Load dumps.

An ARGOFET an APM and an external regulator and you can charge LFP with your alt with zero issues. You can also use an APM and DC to DC but charging will be slow..

Sabre36 said:

The worst thing you can do to a stock alt is to improve upon the crappy factory wiring. It is loaded with voltage drop which is also helping to protect a stock alt. Best way to protect against heat damage is an external regulator such as Balmar or Wakespeed. Balmar also makes an excellent “Alternator Protection Module” which deals with Load dumps”. An ARGOFET, APM and an external regulator and you can charge LFP with your alt with zero issues.

Click to expand...

This has been my position for why those that claim they don't need DC-DC chargers because they've never blown up a stock alternator.

That 0.8-1.0V drop causes the alternator to throttle back its output before it cooks.

sunshine_eggo said:

This has been my position for why those that claim they don't need DC-DC chargers because they've never blown up a stock alternator.

That 0.8-1.0V drop causes the alternator to throttle back its output before it cooks.

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We Unfortunately folks get frustrated their 80A Hitachi is only putting 12-15A into the LFP bank so they upgrade the alt B+ & B- wires and cook goes the alt. We had a recycle bin in our shop full of cooked stators.
We first started seeing heat damage when AGM’s hit the scene. then when FDC & AGM banks kept getting bigger and bigger Heat damage continued. Then LFP Hit big for us back in 2011, all custom built packs or Genasun back then and luckily we already knew how to deal with it..

My Bosch AL170X never seems to go above 40°C supplying `75A to a 4s2P 460Ahr bank. (Too big for my needs)
200A Argofet splitter. Planning on a small adjustable buck to periodically give start LA a bit of a nudge.
MC618 set to 55% (bottom setting as only 1 V belt)
Factory cooling cowl on back of alt to saloon air.
Porsche 944 factory cowl can be rotated to exit outside. (with a bit of fg mod to cowl)
Good thing is I have a 12v fan I can mount to force air in if necessary.

roly1 said:

My Bosch AL170X never seems to go above 40°C supplying `75A to a 4s2P 460Ahr bank. (Too big for my needs)
200A Argofet splitter. Planning on a small adjustable buck to periodically give start LA a bit of a nudge.
MC618 set to 55% (bottom setting as only 1 V belt)
Factory cooling cowl on back of alt to saloon air.
Porsche 944 factory cowl can be rotated to exit outside. (with a bit of fg mod to cowl)
Good thing is I have a 12v fan I can mount to force air in if necessary.

Click to expand...

With BLM cutting field potential that much I would not expect that alt to over heat. the Al170x is typically a 115- 120A alt depending on who did the reman and what stator they used. You’re running it at approx 65% of its potential so yes it will like that and lead a long life.

It’s stock original out of a 944. I thought the AL170x was a Bosch number.(guessed!) I just gave it a birthday, replace ir/brush set with brush set and terminals and bearings.Easy. Thanks for heads up.