Lithium battery alternator charging.

Mike,

Get a dc to DC charger. That will limit demand on the alternator and provide the ideal charging voltage too!

Consider SiO2 batteries. Those are where I'm going to.

Depends on what you are driving. Yes lithium will accept more amps. If your connection to the battery is long it may have enough resistance to self regulate. A MH with a short fat connection could well put your alternator at max power. A DC-DC charger such as Renogy will limit the power. This will also isolate the house system so if you have a BIRD you may need to consider the limitations.

The Victron test was done on a bench not an RV.

pianotuna wrote:
Get a DC to DC charger. That will limit demand on the alternator and provide the ideal charging voltage too!

TRUE !

Modern vehicle charging systems do a very poor job of recharging flooded lead acid or AGM batteries. If you have a good sized "house bank" (four 6V golf cart batteries) and they are down to about 50% SOC, they will likely not get back to 100% ater 8-10 hours of driving !

A DC to DC charger will fix this problem also.

time2roll wrote:
A DC-DC charger such as Renogy will limit the power.

More importantly, a DC-DC charger will make sure that the PROPER voltage is delivered to your house battery bank. This is the KEY to getting a full charge while driving,

Not sure how I would incorporate a dc-dc charge into a stock sprinter charging system. Anyone seen any documentation on this would be done?

My house batteries are located in the engine compartment so should not be a long run. I have not looked closely yet on the wiring.

Place the dc to DC charger between the battery positive and the charge cable. Done!

You most likely don't NEED to add a DC-DC charger to your system, but you may want to. The Victron video proves a point, but is not representative of a real world situation.

A good option would be to install your lithium battery and see how the system responds then decide if you need or want a DC-DC charger. As pianotuna points out, they are easy to install.

Also the engine compartment is not a great spot for either the batteries or charger. Is this a commercial RV or a conversion?

The Victron video does not include one item that is in place on most RV's--a fuse in the charging circuit which would fail before the alternator let out the magic blue smoke.

When I had 875 amp-hours of capacity in my E-450, I had to replace the 60 charging path fuse. I replaced it with an automatic circuit breaker. No alternators were placed on the pyre.

We just installed a Renogy 40a dc to dc charger in our truck camper. Ran ~25 feet of 2 gauge cable (along with several 175a Anderson-type connectors) from the our Ram 3500's battery (used a 60a Zcase fuse) to the charger mounted inside the truck camper. Used the truck's frame for most of the neg run. With 2 GC2's discharged to 12.2v, get 40a of charge current with a 43a load on the alternator (.3v drop from alternator to charger). Pretty pleased with how this Renogy performs. For the heck of it we also turned on the 45a converter in our truck camper at the same time and managed almost 75a of total charge current.

There's always lots of discussion about the potential dangers of overloading an alternator by direct-charging house batteries. Interesting to note that Larry at Lifeblue Batteries (and Starlight Solar??) said he's installed hundreds of alternator/house battery charging systems through the years using only a battery isolator. In all these installs he said he's never witnessed or had anyone report an alternator failure. Who knows, maybe this whole overloading an alternator thing is akin to many discussions about payload. Yes, with any given scenario the sky can fall, but how often does it?

otrfun wrote:


There's always lots of discussion about the potential dangers of overloading an alternator by direct-charging house batteries. Interesting to note that Larry at Lifeblue Batteries (and Starlight Solar??) said he's installed hundreds of alternator/house battery charging systems through the years using only a battery isolator. In all these installs he said he's never witnessed or had anyone report an alternator failure. Who knows, maybe this whole overloading an alternator thing is akin to many discussions about payload. Yes, with any given scenario the sky can fall, but how often does it?

Nice overkill on the wiring. Well done.

Typically the wire for charging is only #8. Typically, the alternator "sees" the starter battery and tappers the out put quite quickly. Typically there is a 60 amp fuse in the charging circuit. (at least for Ford).

So the alternator is unlikely to fail.

What *is* a concern is the alternator feeding too much voltage to the LI and that might cause the bms to shut down. And that's why the dc to DC charge needs to be in place.