Lithium's and protecting the alternator

[Richpatty]

I do not know anyone personally who has had this happen…. And a few folks including Charlie (@Chuggs) and others who have said that the gauge and length of cable should prevent more than 100 amps from being pulled, so yes, this may be a case of over engineering. If the alternator was overtaxed, especially during engine idle, it could overheat and fail.
Which is why I was looking to see if anyone else had feelings around this. I am not overly concerned, but wanted to get more opinions from folks.

it may be not be an issue due to the light amount of travel we have been able to do in the past few years….

 

[Joe Hogan]

Are there any reports of an alternator failing? Would an alternator "fail" just because the demand for amps is higher than its output? I hear they are quite robust. I think I'd just let things go and if it fails then correct for next time around but my guess is it is not going to fail. Maybe over-engineering the situation? Maybe also someone that sells LifePO4 batteries for RVers can shed some light on this topic?

Granted I am not a seller of these systems, we have managed LiIon and LiFePo systems for many years. Both home and vehicle battery and solar setups. Experience is a steep learning curve with relatively new applications of existing tech. That said, my $0.02.

Battleborn promotes their product as a drop in replacement for traditional wet cell batteries. Assume they manage the charging through the BMS installed in each of the batteries because there has not been much posted about charging issues.

An automotive alternator designed duty cycle and available output at a given RPM are important considerations. A large LiFePo battery bank at a low state of charge can easily demand 100% duty cycle at max available output for hours from an alternator useless there is a limiting device, DIM or BIRD in the RV case.
Depending on the available cooling to the alternator, an 'uncontrolled' load demanding 100% for extended periods can easily "smoke" an alternator not designed for the load.

Just a brief summary of alternator operation in an automobile application Alternator Output Ratings: What Do Those Numbers Really Mean?

 

[Kevin D Pem]

Joe thanks for that, everyone that is asking for answers on this topic should be thankful for your link.

Problem is it takes much research to put the information to practice.

Here is some more info not covered on that link.
Theory tells us the number of Flux a wire cuts through determine the voltage the action provides. An automobile generator is designed with two objects. Price and weight. The way both objectives are met is by limiting material and the use of high frequency design. High frequency design and minimum weight lowers duty cycle, and this is the problem when introducing a technology like lithium.

As the article states the high rpm rating is rather high, and the lithium battery will take all the power it can get. Just because the engine is a low rpm unit doesn't mean the alternator is not geared to spin faster.

To answer @Neal , I chimed in, I only argued the case for the benefit of the forum. I have extensive experience building poor boy generators starting in 2004. To use an automobile alternator to charge deep cycle batteries is deadly to the equipment. On one occasion a unit I built turned the copper field coils blue. Seldom will the built in regulator in my units last two months. That is the reason I built my own alternator regulator unit. It is one of the reasons I went to a 24v house bank(twice the watts,for the amps).

Typically the alternator on a bus is more robust than that in automobiles, and that adds to the price of replacement, but does not eliminate the problems with charging lithium banks.

Three stage charger/alternators as those used in the marine industry can be an option, but I have no long term history. But after 6 or more poor boy where the major failure was the alternator, I leave a warning!!! "Charge lithium with caution "!

 

[Richpatty]

Thanks all. Looks like i may put in a cutoff switch (like mentioned in the first post) in my battery compartment. This will prevent charging of the lithiums from the alternator, but with solar, it may not matter as much.

Unless a better solution ones along…

 

[Richpatty]

I found this device which may help my paranoia.

Alternator Protection Module: APM-12 - Balmar

The Balmar APM provides best-in-class surge protection using the latest technology developed for the automotive industry. It can protect alternators from damaging effects: • Battery switch disconnects • Lithium battery BMS disconnects • Surges from solenoids, combiners, starters and other...

balmar.net

It protects the alternator from surges such as one my see from the Li-Bim shutting down (as it does every 20 minutes or so)

I was thinking I might be able to have Freightliner install it? Not sure I can do it... Hard to get into a rear radiator engine.

Thoughts?

 

[Neal]

Maybe ask FCCC if they already have something we don't know about? They may have already put some protection in place.

 

[Richpatty]

Funny you should say that. I called FL support Friday and asked about alternator failures and lithium batteries and he was not aware of any issues. So maybe this is a non issue. Or there just isn’t enough folks with lithiums to pop up on their radar.

He also did not mention any type of protection that may already be in place.

 

[Richpatty]

I did hear from someone who provided this info about using a device like above:

“Again so long as your starter batteries are still connected they will absorb most of the spike. Lead batteries will act like one of these devices even if fully charged because the spike is much higher voltage which causes the batteries to accept the current, you are basically over charging them for a split second.

It can't hurt to add one of these devices, but its debatable if it helps, I can find little objective measurement of a voltage spike from a alternator when starter batteries are still connected because it seems to a be a non issue, the ISO 16750-2 that this device is conformant to relates to removing *all* batteries from the system.

With a lead acid battery inline this is no different than any other heavy load on the alternator such as hydraulic motors or grid heaters, these can pull hundreds of amps and are shutoff abruptly on a regular basis causing a load dump.

I really do need to put a scope on mine and use the boost solenoid to simulate a load dump just to actually see what sort of spike makes it through the starter batteries, I suspect it will be minimal. The AC impedance of a fully charged lead acid starter battery is around 10 milliohms. This would mean even a 24v spike would be around 1200 amps into the battery at 60v you're looking at near 5000 amps. The starter battery is a great TVS device.”

So this may be a non-issue…. Figured I would pass it on.