How to burn out your alternator while direct charging LiFePo4

[Ticklebelly]

Victron has put out some info on how you can burn out your alternator by direct charging LiFePo4 at low engine RPM.    Apparently, at low engine RPM, the fixed fan on the alternator does not provide sufficient cooling if the alternator is putting out a high charging current.    The characteristics of LiFePo4  demand X current from the alternator whether engine RPM are high or low and it is common knowledge that LiFePo4 will demand just about anything made available to it.   The comparatively high internal resistance of LA technology does not cause the same high current demand.   The fix suggested by Victron is to fit a low capacity alternator (low current output keeps the internals cool), fit a temp probe to the alternator that works to limit current output if internal temp rises too much, or fit a DC to DC charger.

Just a Heads Up for those who want to do a drop in on the other side of something like a VSR.   If doing a new install, a dual input DC to DC charger is likely to be the simple way to go.   Even if you do not intend to include Solar initially, the cost difference is almost nil and the expansion capability is always there.

[Wayne49]

Never directly hook up batteries with different chemistries to your vehicle's system.

I got burned (a lot of smoke, anyway) by doing that with mixing Gel and FLA.

[Scott7022]

If you're spending the bucks on a lithium system then Mechman is the link for alternators. I've had them build me a couple. Sold them working with the vehicle. Never had a failure. Also AM/Solar has a 240 amp hour connection from alternator charger (never used it but AM has a good rep) for lithium. Its a system not a drop in.

[Roadtripp]

I see Victron Energy is coming out with new DC-DC chargers. The Orion TR series. 
https://www.victronenergy.com/blog/2019/...c-charger/
One advantage of these is ease of installation and it can be moved from from one vehicle to another. As I drive far under the average it’s not worth the expense of adding a second alternator or changing my alternator. Most of my charging will be accomplished by solar.

[Scott7022]

I am confused a little. If you drive under the average, combined with the article you posted about not blowing up your alternator you'd want to make the most of your little drive time. We all want to use the free energy from the sun. A 30 amp DC/DC charger will separate your chemistries and protect your stock alternator. Good choices all around.

Speaking personally if I spent two large on lithium (200 amp/hr (example 2 BB 31's) not an endorsement but just an example. I'd have 180 useable amps, pulled down hard or 120 lightly used. Let's use 120. The Victron needs to pull from your engine battery for a little over four hours. To replenish the start stress and the house battery in a perfect "I am getting 30 amps world." Four hours is a long drive. If you hardly drive getting a 240 amp/hr charge means by the time you do a quick milk run into Quartzite from yarc camp you're full.

I am not trying to be a jerk here. Just trying to understand your design goals. Lithium is expensive in the long run it ends up cheaper but the real benefits of the chemistry is charging speed and power delivery, amps out without Peukerts effect. Weight of the components and sealed design. Spending cash and not taking advantage of the entire thing is like buying a Ferrari and leaving it in second.

I get the solar angle and everyone wants the free energy from the sun. But a back up for bad weather is something I just wanted to add to the thought process. Idling is a killer for engines. The lack of moving airflow and low idle speed to make the alternator work works against you. Hence why ambulances have a high idle switch.

Again not trying to be a jerk just adding stuff to think about. Choices choices.

[Roadtripp]

Sorry for the late response. Thanks for pointing out some trade-offs and considerations. These dc to dc chargers can be placed in parallel. I might add a second 400 watt dc to dc charger if I like the performance of the first. Or even a third unit. As I can afford it. I can’t do the major engine modification and expense adding a second alternator at present.  But later I may decide I want a high amperage alternator or second alternator. This is a quick and easy way to start using the Lithium batteries. 
 I guess I’m also wary of high amperage. That’s when things can go wrong. Everything needs to be ship shape and Skookum. My ragtag pirate fleet is not that lol. Not yet anyway. Later I hope to get it sorted out. 
   I can understand if folks want a fast charge and high performance. I’m hoping to count on the bright desert sun and lots of solar panels for the majority of my charge. Also with this dc to dc charger I can leave my existing solar energy system with lead acid batteries for now, which is working fine, and add Lithium batteries as auxiliary batteries without changing much now. Just a few minutes connecting the dc to dc charger between the two. 
 Another thing to remember is Lithium ion doesn’t need to be brought to full charge like LA batteries so this opens up a lot of flexibility. I don’t need to worry about how long I run the engine, how far I drive, how powerful the alternator is. I do need to live with the limited power available. That’s a trade-off I need to make for now. But I do get to start playing with my Lithium batteries. That’s if I understand how these things work properly. Maybe I’m overlooking something. It wouldn’t be the first time. 
 I usually park far away from Quartzsite so my I’m hoping my drives will be just right combined with solar.

[sternwake]

A big depleted bank of lead acid agms can also overheat alternators.

One potential solution, is a dedicated cold air feed tube to alternator so it is inhaling ambient air . Not .underhood.air. at 65mph i cant get my maxed out alternator to exceed 140f. But if.i.stop.at.redlight half the amps.and temp skyrockets to 200+f.

I think.i could.max.out.my.alternator.for hours safely at highway speeds. but mere.minutes at idle.

[TWIH]

So could a battery cutoff switch then be used to separate the lifepo from the idling alternator? I could see the advantage of that if you are needing to warm up the van for a few minutes before driving, say in cold weather. Then turn the switch as you head out.

No doubt that lifepo complicates things in a drop-in system where the other components were not designed for it, much less even depleted agm’s... probably not a sound decision for electrical component health.

[Roadtripp]

This Victron video shows them bench testing alternators charging Lithium batteries. 

[Gr8ful]

This Victron video shows them bench testing alternators charging Lithium batteries. 


Good video, Thanks! My ambo has 1 250 amp altenator & a master switch which I left on a few days once. It started but was putting out 150 amps, the most I've seen. No house batteries just the 2 starting ones. When you depress the parking brake with it running it goes into high idle RPM.