how to not destroy an alternator when charging LI batteries.

[pianotuna]

Hi all,

https://youtu.be/jgoIocPgOug

The video offers solutions.

[CharlesinGA]

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

[MEXICOWANDERER]

The dummies today use Ford alternator fans on all early GM AND ford small case ALTS. I'm glad to be retired. Today, use the wrong part # reg and the ECU faults limp home.

[2112]

Seeing that alternator smoke reminded me, about 40 years ago I cobbled a Delco 10si alternator to a chainsaw engine to power 6 automotive high beam headlights to night fish at the Texas City Dike. That alternator lasted about 15 minutes before it smoked.

[MEXICOWANDERER]

Look at the wiring in newer vehicles and it is a full 3 AWG larger than those ten years older. A 120 amp genuine not a toy breaker is less than .2 volt at full load. BMS are dedicated to lithium technology.

Nippensenso ND is said to be hot on the trail of Silicon Carbide rectifiers controlled by a processor unit. For use on electric cargo trucks used on regenerative braking which is a huge stumbling block because of engine exhaust brake elimination.

Any voltage loss in excess of a half volt at full alternator output is considered by me to be a design failure. I have had to use full 4/0 charging cable on several motorhomes with rear engines and front mounted batteries. My bus has 4/0, the gen shed uses 330MCM cables which are almost twice the diameter of 4/0. I used split 3/4" garden hose to pass the cables within the frame rails of pusher motor homes. There are button end cable ties with the once inch diameter button to secure stuff to the channel of a frame rail that has a hole.

[FWC]

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

Exactly! This is yet another instance of an edge case being way overblown on internet forums. The setup in the video is not representative of a real world vehicular application.

It is true that a lithium battery can draw more current than an alternator can supply (it is also true for lead acid) but in most situations it is not a problem due to the resistance of the wires, breakers, relays and BMS.

[navigator2346]

Seems the easy way is to separate the Li and lead acid banks. Have the alternator charge the lead acid bank then use a dc to dc charger to charge the Li bank

[Bert_the_Welder]

Whilst I freely admit to knowing sweet FA about electrical, I do question the validity of taking a devise usually used in a moving vehicle and having plenty of cool, fresh air to draw in and plopping it on a crowded work bench. That seems poor methodology to me.

[time2roll]

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

[MEXICOWANDERER]

The more **** you stuff into an electronic control unit the more there is to go wrong. Tiny 30 and 40 horsepower sailboat motors use cutouts to stop charging if the engine doesn't have enough power to fight a current. They also use a 30 second ramp enabler to prevent cold start alternator drag down. Useless for automotive.
New motorhome electrical design is so stupid on some pushers they control voltage regulators with a remote sensing connection instead of minimizing charge cabling voltage drop.

Just as a chuckle my 2 remote rectifiers have 6 rectifiers each. They are stud type PLATING rectifiers 1,200 amp 1,675 PIV. They use a 1? wrench and have 2/0 braided leads. A 1?" hole was drilled for the stud
They weigh 2 pounds each. The heat sinks are ³/16" anodized copper. Even back then the copper cost me a hundred dollars as did the anodizing.

[sjholt]

Those tests on the PM of the none Belmar alternator are bogus because in most motorhomes the rpm of the alternator is 3 times the crank speed so at 800rpm crank speed(idle) the alternator would be doing 2400 rpm thus cooling a lot more. and when I drive down the road at 1900 rpm the alternator is doing 5700 rpm and could be putting out 165 amps. It might burn up at that amount of amps,but hasn't yet because it never reaches that.JMHO

[MEXICOWANDERER]

Anyone that charges batteries in a cruising sailboat needs to invest in better ventilation. I've been aboard dozens and dozens of sloops schooners and ketches down here that raise temperatures to above 100F in salons, and galleys when charging batteries.

MOST sailboat engines feature a 2 to 1 or higher pulley to pulley ratio between the engine and alternator. Few engines run optimally at dead idle. Speed is carefully adjusted to hit the "sweet spot" which eliminates jungle drums roughness, noise and vibration.

Floor and rug drying 120vac fans can inject enough air into an engine compartment to lower air temperature as much as fifty degrees. Not theoretically. I used to haul mine as part of my tool load.

The main problem with new fashioned alternators is they have internal fans. Adapt a proper external fan and suddenly temperatures drop dramatically.

Remote rectifier bridges not only remove junction and heat sink heat but open up the slip ring end of the alternator to cooling air.

So the test with the Bosch alternator included playing with a stacked deck. The motor they used was a 1720 RPM with very little pulley advantage. See what happens at 3,000 alternator rotor RPM. The new class of rectified WYE stators allows extremely high amperage at extremely low RPM. FAR FAR FAR slower than what an automotive application can operate at. 3.5 to 1 pulley ratio is very common.

But don't get me wrong. Heat is a terrible enemy of any alternator. My Niehoff and my 50SI 24 volt units are fed cooler air. And both have anodized copper fin stacks for external rectification.

Also..........

A single group 31 battery can accept over 100 amps. A series parallel stack of 4 cheap golf car batteries will eat 120+ amps for longer than I care to state.

So the LITHIUM hook in the BALMAR ad is misleading. The entire concept is invalid.

As a designer, meaning rotor, stator and rectifier concepts makes me eligible to judge this stuff.

If a cruising sailboat alternator has to have its charging potential curtailed to prevent burning up, then it's suffering from a FATAL FLAW. Read garbage, quackery and incompetent system design.

[theoldwizard1]

The Balmar alternators and regulators are very popular with the sailing community, but they are $$$$ !!!

The video below discusses charging lithium batteries, but everything they talk about applies to lead-acid and AGM house batteries, just change some of the settings on the charge controller.

Charge LITHIUM Batteries While Driving - System Setup

[dougrainer]

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