Alternator - Adding 2nd Alternator Advice

[Brent Harte]

I have a 2001 Beaver Monterey SeaCliff  with Cat Engine,  I would appreciate any info on adding a 2nd alternator,  Eg:  Type, Wiring, Sources, Shops to Install.  I live in AZ.  Also GOOD IDEA, or BAD IDEA.

[Steve Huber Co-Admin]

Brent,
Why do you want to add a 2nd alternator? What problem are you trying to solve?
Steve

[Brent Harte]

Trying to leave the chassis + house battery and factory electric system, (including inverter) FACTORY ORIGINAL.  Adding lithium + additional split phase inverter to run 50 amp panel.  Would use additional alternator to charge lithium.

[Steve Huber Co-Admin]

Brent,
I'm confused (as usual). If you are leaving the house/chassis batteries & inverter/charger intact and adding the lithiums along with an added inverter/charger, what purpose do the original house batteries serve? Also do you plan to run both inverter/chargers off shore power?
IMHO seems like you could buy a lot of wet cells or agms for the $ you will probably spend on your intended setup.
Steve

[Fred Brooks]

   Brent,
Another option would be to add a 50amp DC to DC charger to keep the existing alternator and charge the new lithium from the chassis batteries. No hassle trying to mount a second alternator. Fred

[Anand Shah]

I’m in the middle of doing this myself now, barely can wrap my head around my own electrical system so I can’t claim expertise.  But the simplest answer is to add a DC-DC charger.   The 2nd alternator, depending on the size of the lithium bank will still heat up dramatically without a current limiting device— because lithium batteries do not limit current input - charging LFP cells with 1C current will also reduce their life span in terms of cycles - they tend to be most optimal with a 0.4C charge rate or lower.

I’m disabling the stock Big Boy, leaving it as is, and using a DC-DC and AMP-L-START to deal with the bidirectional.  With an ignition signal, the DC-DC charges the lithiums and the AMP-L-START is disabled.  When on shore or genset and no ignition, the AMP-L-START charges the chassis and the DC-DC is off.

Anand

[Anand Shah]

You could also turn off your inverter’s charger if not suited for Lithium and put a lithium specific charger that charges your lithium bank from 120V when on shore or genset.

Anand

[Brent Harte]

Hi Steve,

So my current inverter powers a few 120 plugs and microwave,  the inverter supplies no power to the 50amp panel that powers the AC, Refrig, Remaining 120 plugs.  So I thought I would install 48 volt lithium batteries under our bed, with fire barrier, and a split phase Victron with built in transfer switch in the closet next to the 50amp breaker panel.  This system would power AC etc, while the original Inverter + original batteries would continue to power Microwave and plugs. 

Brent

[Bill Lampkin]

Have you run the numbers on A/C? each A/C wil have a running amps of about (best case) 12 amps at 120v ac. 12a at 120vac =120a at 12v dc (you should increase this by 25% to account for efficiency losses). A 400 amp hour lithium battery then will power one AC for only 2 hrs if you limit discharge to 50% to maximize battery life. You're better off running the generator to power those hi amperage loads, thats why Beaver split the electrical panels in the first place. If you have better numbers than mine, we'd like to see them. Good luck.

[Steve Huber Co-Admin]

Thx Brent, that explains your approach. However I agree with Bill that unless you've found some super high output batteries, they won't support the ACs for very long. Again, to me the payoff doesn't seem to justify the $ outlay.
Steve