How to not blow up your Alternator when charging Lithium

Comments · 385

• PH

  @philippschneidenbach · 2 years ago · pinned

  Ok, so the actual perception is: 3000 alternator rpm if created from a 1000rpm engine with general overdrive of ratio 3 gives healthy 40ish degrees and 78.9 Amps off of a 70a Citroen Alternator. Good.<br>Real verdict of this video without the voice is that a fully loaded alternator should not be operated below 1000 engine rpm (=do not 100% load in idle, which is not hard to understand) but is very fine when driving (lets say approx. 2000 engine rpm).<br>Regarding Lithium everybody should know that a lead acid battery as a buffer to avoid load off voltages and then DCDC off to a Lithium with current limiting to a current value/number below (80%) the alternator limit is a good ballpark.

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• OP

  @Opel_Zafira_Bass · 1 year ago

  Ive been charging 3lto lithium banks for a solid 3 months so far for a daily without any problems or whatsoever but still very interesting!

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• 79

  @7903inside · 11 months ago

  You can add thermo switch, which could turn off alternator induction, when it temp reach 110C°, as example, and restore, when it cold down to 90C°

  5

• LA

  @LawpickingLocksmith · 2 years ago

  Knowing the internal resistance of both the alternator and the battery is key to planing the setup. If the battery has a lower impedance, a buckboost combo can protect both. Best of all is an on dash selector where the operator can choose to limit to 80% of the capacity. Careful usage planning ahead of time will give you optimum longevity. &nbsp;Best to use 2 batteries for ultimate redundancy. For cold weather use a battery heating will lift life expectancy.

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• GE

  @geraudcoste5743 · 2 years ago

  As many I guess, this video worried me a bit thinking I&apos;ll blow my 2 x 115A 18 year old alternators mounted on 2 Volvo Penta D4 engines. But then I kept on looking because I didn&apos;t like the more complex DC/DC chargers known to be heat producers with quite small amp output. And I found some very interresting stuff about this video such as the fact the test was made with a Citroen alternator. So I ended up thinking, what the heck, if my alternators blow, it&apos;ll just be time to change them anyway. I did the test with the following setup: 2 alternators feeding 2 Victron Argofet battery isolators with 3 outputs feeding my 3 battery banks: 1 bowthruster/winch Optima 5.5 battery - 2 port engine 5.5 Optima battery - 3 starboard engine &amp; house battery (this one is a mix of 75Ah Optima 5.5 + 400 Ah LiFePO4). I&apos;ve monitored carefully the current draw (meter + Victron App) and I&apos;ve never seen more than a 120 Ah draw, even with the lithium fully discharged. I also checked the heat on the alternators and everything was normal. Actually, most of the time the charging curent is around 80Ah which should be ok for 2 x 115A alternators. This is my first year with this setup and so far it works like a charme. No anomaly seen and the Daly BMS as well as the Victron App have never reported any error. I will follow up this comment if a noticeable problem arises of course. <br>Geraud in the Med area of France

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• RA

  @Rapido410Randonneur · 7 months ago

  As I have a vintage motorhome that only has a 55amp alternator, I have added a remote switch to my combined DC-DC/MPPT charger so that although the DC-DC is set to 30 amps, I can switch it off when the engine is idling and back on when driving down the road. I used a simple remote relay (Aliexpress) that cost almost nothing and it&apos;s been great.

• GA

  @gaidin58 · 2 years ago

  2 things: 1, you did not simulate the engine compartment of the vehicle which typically has a radiator fan located very close to the alternator and blows air on the alternator helping with cooling. 2, as far as sudden shut down of the lithium charging which could damage the alternator, most vehicle engine scenarios include a lead acid battery in the charging loop which will absorb the output of the alternator when the lithium suddenly stops accepting a charge because the BMS shuts down charging.

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• NĀ

  @Nāmarūpa1 · 2 years ago (edited)

  Takeaways for me personally: 1/ I need to track alternator temperature and 2/ I need to drive the field current (FR) appropriately, probably following charge state (BLK, ABS, FLT, OFF)

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• FO

  @fourfortyroadrunner6701 · 2 years ago

  Your comment about the 1500RPM test &nbsp;&quot;the engine running at idle&quot; is &nbsp;incorrect. &nbsp; Typical &nbsp;engine crank &nbsp;to alternator ratios &nbsp;vary from at least 2:1, &nbsp;more typically 3:1 &nbsp;to &nbsp;4:1. &nbsp;I have not documented &nbsp;modern &nbsp;stuff &nbsp;very much, it is possible that some engines are &nbsp;a higher ratio yet. &nbsp;In my day, &nbsp;my 440 Plymouth was 4:1, &nbsp;meaning, that if the engine was spinning 6K RPM, the alternator &nbsp;was &nbsp;screaming at 24,000 RPM. &nbsp;I did &nbsp;fail a &nbsp;couple of them.

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• CA

  @caminhoesemusicas4234 · 2 years ago

  Maravilhoso <br>Meu sonho ter um aparelho desses

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• GO

  @Goodkiwibloke · 2 years ago

  In an internal combustion engine situation, the alternator typically runs at 3 times crank speed. So 1500 crankshaft rpm = 4500 alternator rpm = way out of danger zone. <br><br>Your test rig seemed to run alternator rpm = motor rpm = overheat problem

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• SE

  @sethklemba · 1 year ago

  I charge my 4 cell lifepo4 battery &nbsp;off my car using a toolkit rc m8 charger. It balances the cells and regulates the current for whats best for battery while charging. I use that as my bms with fusing for the bus bar output.