how to not destroy an alternator when charging LI batteries.

[pianotuna]

Hi all,

https://youtu.be/jgoIocPgOug

The video offers solutions.

[StirCrazy]

3 tons wrote:
Kinda makes me wonder, whatever happened to the minority idea (now defunct?? ..R.I.P.) that Lithium batteries (LFP’s) don’t charge any faster than FWC’s??

3 tons

:B

[3_tons]

time2roll wrote:
My trailer charges about the same with LA or LFP. No fuse issues, no alternator issues.

I choose not to charge my 200a/h LFP from the alternator because I prefer (say, once fully charged…) not to have it maintained at 100% SOC…I suppose a switch would remedy this, but as a desert camper I’m mostly able to keep within a decent SOC range (based on usage) with just harvest alone…

3 tons

[time2roll]

My trailer charges about the same with LA or LFP. No fuse issues, no alternator issues.

[otrfun]

. .

[3_tons]

Kinda makes me wonder, whatever happened to the minority idea (now defunct?? ..R.I.P.) that Lithium batteries (LFP’s) don’t charge any faster than FWC’s??

3 tons

[pianotuna]

Because of the low resistance an LiFePo4 may appear to the alternator as a dead battery. So the alternator might tend to run flat out.

However, the charging wire is often rather skimpy. That probably limits the current.

Perhaps one of the folks who has Li could use a clamp on meter and measure what is going on?

I do know that at 875 amp-hours of lead acid, I was blowing a 60 amp fuse on the charging path to the house bank.

I moved to dual 50 amp automatic circuit breakers, adding a 2nd charging path as well as manual control of the isolation solenoids. I have a meter that reads to 70 amps--and then displays dashes. I saw dashes.

[MDKMDK]

dougrainer wrote:
Are there reports of burnt up Alternators from RV'ers installing Lithium Batteries and the Chassis charging system is not designed for Lithium? Doug

Only on the Victron video.

[MDKMDK]

Huntindog wrote:

pianotuna wrote:
Hi all,

https://youtu.be/jgoIocPgOug

The video offers solutions.

This guy isn't all that bright,
When an altenator is installed on a automobile, it is driven by the crankshaft pulley which is much larger. Usually a 4 to one ratio. So even at idle, it would be turning over 2000 rpm

Victron sells several "alternator protection devices" and so, have a dog in the fight. If the alternator doesn't start smoking, you won't buy their stuff to protect yours.
They also supply very little specific information about the alternator's specs, even where it came from, had it been used before, and so on. Then they connect it to a lithum battery with the same "shrouded in mystery" BMS specs. Many people choose to believe it because they've had good luck with other Victron hardware, that's understandable, and everyone always raves about it, especially on the sailing/yachting forums. I've never used any of it, and I haven't had any major problems as a result of not spending my money on their stuff.
Honestly, does anyone know anyone that burned up their alternator charging a lithium battery bank? Or burned up their own? I don't, nor can I find any internet posts that support the notion. (cue the deluge of "I know someone..." replies)

[Huntindog]

pianotuna wrote:
Hi all,

https://youtu.be/jgoIocPgOug

The video offers solutions.

This guy isn't all that bright,
When an altenator is installed on a automobile, it is driven by the crankshaft pulley which is much larger. Usually a 4 to one ratio. So even at idle, it would be turning over 2000 rpm

[MDKMDK]

dougrainer wrote:
Are there reports of burnt up Alternators from RV'ers installing Lithium Batteries and the Chassis charging system is not designed for Lithium? Doug

Old thread, good question. I have googled this, and asked for anyone with a real world experience burning up their alternator with lithium batteries to describe the event, and to date the response is usually "crickets".

[MDKMDK]

FWC wrote:
In many cases there will be no issue with the alternator. I have had various LiFePO4 setups over the past 10 year, and never had an issue with overloading the alternator. The wiring, breakers and ACR between the alternator and batteries provides plenty of resistance to limit the current to the battery bank.

In specific cases with higher voltage alternators and very large gauge wiring, there could be an issue, but it is easy enough to try a direct connection and see how much current flows before adding a DC-DC charger.

CharlesinGA wrote:
Do it right and install a DC to DC charger between the vehicle charging system and the Lithium batteries, and your problems are solved. that is what they are designed for. Lithium connected directly to a alternator charging system will fry the alternator.

The video linked to in the first post is a very good one and while one way (usually on boats) of controlling the charge, the DC/DC works well without messing with hugely expensive alternators custom fitted to a vehicle. New vehicles have computer controlled alternators and none of this plays well with lithium in the house battery box.

Charles

I've put over 6,000 trouble free miles on a standard MB Bosch 220A smart (internal fan, internal regulator) alternator charging 2 X 100Ah Relion RB100-LT batteries, with no additional hardware to do anything in between the charging source and the lithium targets. In varied ambient temperatures and at varied engine RPMs, at varied SoC, including some idling.

[deltabravo]

time2roll wrote:
Most any RV situation the amps will be limited by the wire connecting the alternator and battery.

Yep, unless you do an upgrade like this

[FWC]

In many cases there will be no issue with the alternator. I have had various LiFePO4 setups over the past 10 year, and never had an issue with overloading the alternator. The wiring, breakers and ACR between the alternator and batteries provides plenty of resistance to limit the current to the battery bank.

In specific cases with higher voltage alternators and very large gauge wiring, there could be an issue, but it is easy enough to try a direct connection and see how much current flows before adding a DC-DC charger.

CharlesinGA wrote:
Do it right and install a DC to DC charger between the vehicle charging system and the Lithium batteries, and your problems are solved. that is what they are designed for. Lithium connected directly to a alternator charging system will fry the alternator.

The video linked to in the first post is a very good one and while one way (usually on boats) of controlling the charge, the DC/DC works well without messing with hugely expensive alternators custom fitted to a vehicle. New vehicles have computer controlled alternators and none of this plays well with lithium in the house battery box.

Charles

[steveh27]

My alternator goes through 2 40 amp breakers and then to the battery isolator before going to the batteries so it should be OK.