Upgrading Alternator to charge house batteries faster

[IdaSHO]

And just how "critical" is terribly relative. Hard, perfect numbers on paper are one thing.

Real life is another. Real life shows that the VAST majority of users WILL NOT perfectly maintain their batteries.

That's a fact. So Ill take my $300 in batteries every 6 years and keep driving.
Simple numbers show that I spend roughly $4 per month on batteries.

To bring things back to earth and into perspective....
Most on this forum will spend more than that PER DAY on their morning coffee.

 

[68camaro]

Spend the money on solar.

My rig spends majority of time under tree canopy so solar wouldn't be worth the money for me, I did looked into it though.

 

[Madoxen]

OMG. How long is a piece of string?

It is twice the length from middle to end ;-)

 

[john61ct]

It is twice the length from middle to end ;-)

And much shorter for some than for others!

 

[burleyman]

This youtube video goes back to the thread title and the original post. It provides a good study for just buying and installing a high-output alternator in a vehicle without any other changes as to wiring or reasons for use with the existing system, especially in the case for lithiums vs. other chemistries. It could make for an interesting discussion.

https://www.youtube.com/results?search_query=how+embarassment+led+us+to+370+amps

 

[BobInTheAspens]

Optima says that there is no limit to how fast you can charge their batteries, assuming that the voltage is OK. They say 13.6v to 15.0v. That means that even with a fairly small battery, the limitation will always be your alternator and wiring.

My 2008 4runner has a 130 amp stock alternator. At idle, will charge my 2nd battery (a 50 AmpHour Optima) at 75 amps for a few minutes, and then drop to 60, 50, 40, as it gets charged. If your vehicle won't charge at that rate at idle, check your charge voltage. Most vehicles are set to a much too low voltage.

Buy a Xantrex LinkLite. It monitors charge and discharge amps at the battery very accurately, and will give you the percent level of charge in the battery quite accurately. At about $200 it is very worthwhile. Otherwise, you are just guessing.

The wire that carries the charge from the alternator to the battery will never overheat. The reason is that as amps go up, voltage goes down, and the battery will accept less charge. That is a fail-safe situation as far as safety goes. Of course, you want to make the wire fat enough to not reduce your charge rate too much.

 

[john61ct]

Optima says that there is no limit to how fast you can charge their batteries, assuming that the voltage is OK. They say 13.6v to 15.0v. That means that even with a fairly small battery, the limitation will always be your alternator and wiring.

100% false.

Even if theirs is the highest CAR lead battery on the planet, the trailing amps bottleneck is always there with lead.

Say you do an A / B test both with a 75Ah battery depleted all the way, i.e. to 50% SoC.

Even if that battery can in theory pull 500A in that state, it will only do so for a few minutes, then increased ESIR as SoC climbs will start to drastically reduce the current rate.

This is true no matter the voltage setpoint.

A on an alternator capable of putting out 50A continuously

B at 200A

B might get to the CC-CV transition point after only 50min, while A takes 90min.

But A may be at 80% SoC when it does so, while B only 70%.

And as current acceptance drops to say 20A over the next 3-4 hours, they both end up at similar say 92 vs 95% Full

those last few SoC% still takes another 2-3 hours

At 1A flow, that is still 0.013C even if at 98% might still have an hour to go

100% Full does not happen until current drops well below half an amp.

B might reach that say 30min earlier than A, but still over 6 hours.

Every lead bank **must** get to that 100% point very regularly for decent longevity, ideally "most cycles", certainly at least once a week.

Firefly Oasis being the sole exception, but that's a separate thread.

And since Optima really is just a decent Starter since bought out by JCI,

no longer actually built good enough to use for deep cycling

all this is a moot issue anyway.