Upgrading Alternator to charge house batteries faster

68camaro

Any River...Any Place
Hi, I have a Ford E-350 camper cutaway with stock 130 amp alternator and 2 - 6V 220ah AGM batteries plus separator. If my engine battery goes dead I have switch I can hold and use the house batteries to jump start the engine battery.

I would like to be able to charge the house batteries much more quickly with the vehicle turned on but stationary, at idle in "Park". Of the three options below, would any or all work and what would be easiest solution? Would a high idle kit be necessary.

How do you account for batteries limiting charging capacity and getting them to take charges quicker?

I think my options are:

1. Second Alternator - I know ER and Provan Tiger use dual alternators to do this, but how is this setup, are both Alternators going to the house batteries or just one? Would second 130Amp work or higher end more Amp with better control charger built-in?

2. Upgrade to 200-300 amp single alternator - again would amps received by house batteries be limited, if so can this be mitigated?

3. B2B Charger - how realistic and easy, would I lose ability to start engine battery with house battery.

Thanks
 

Alloy

Well-known member
Like Verkstad mentioned there is little you can do to speed up the charging of AGM. In fact you can shorten the life by bulk charging at too high of a rate.

The charge time (bulk - absorption - float) for deep cycle FLA (flooded lead acid) that once discharged below 90% is a minimum of 4 hours and most often 6-8 hours.

A 4th option is Lithium with a B2B.

You can set up crossover / combiner switches between the banks but a set of jumper cables is just as good.
 
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john61ct

Adventurer
AGM that can accept 0.8C in the early stages will get up to 70-80% very quickly, within an hour.

But for decent longevity they need another 6+ hours to get to 100% Full as current declines.

If not "most cycles", then at least once a week.

All depends how long you stay away from mains power.

Or get a good solar setup, use FF in the morning then finish with solar.

Oasis Firefly are unique in their resistance to damage from PSOC abuse.

But really, LFP is the solution, can refill in an hour or two.
 

SoCal Tom

Explorer
You also have to look carefully at the upgraded alternators. Often they produce less power at idle than stock.
 

DiploStrat

Expedition Leader
Some comments:

-- As noted, most of your issues have to do with the nature of lead acid batteries. The charge rate is largely a function of the difference between the charging voltage and the battery voltage. AGM batteries have lower internal resistance, but the voltage still rises rapidly and, as it does, the charge rate drops. Doesn't matter how big your charger is.

-- "But for decent longevity they need another 6+ hours to get to 100% Full as current declines." This is very, very true. Ignore it at your peril. See next point.

-- "Spend the money on solar. " But spend it on the right solar. I am ashamed to confess that when I bought my new truck I paid no attention to the solar controller. I assumed that, like my previous truck, the solar controller was set to provide a L O N G absorb stage. It wasn't (and is not adjustable) and my AGMs have suffered.

My rule of thumb for an overland vehicle is that you get your bulk charge from the alternator and your absorb from the solar controller. This is an over simplification, of course, but it is still close.

If you need a faster bulk charge, you are looking at lithium.

In the interim, until I can replace my solar controller, I am using my shore charger which is set with one hour of absorb for every 100Ah of battery. The batteries are responding, albeit slowly.

Finally, can't speak to Earthroamer, but most Provan Tigers use a Blue Sea ACR and 1/0 AWG cables. They do not rewire the factory alternators.
 

IdaSHO

IDACAMPER
For what its worth, the most I ever see going into the house bank with our setup is 20-22 amps

That's a 220AH of wet deep cycles
Stock alternator on 2011 6.2 Ford
Alt-Relay-House bank all in #2 conductor(s) with tinned lugs,
total run being about 15 feet.

Again, the most I see is 20 or so amps.
I've tested it a few times, with batteries at 40-50% SOC, solar disconnected, and engine running.
Nowhere near the max rating of the stock alternator (150A)

After a half hour or so, it levels off to considerably less.
 

DiploStrat

Expedition Leader
Interesting.

With a Chevrolet, which has frisky voltages, as high as 15.5v @ 32F/0C, I would see 50 to 75A.

This was 2x 2.0AWG with a run of 25 feet. This was a 600Ah battery bank, about 125Ah down. But, as noted, after 30 minutes the rate dropped to under 50A.

This is one reason that most battery to battery charges are only 20 - 50A. You can't use that much more for very long.
 

john61ct

Adventurer
But for good longevity with true deep cycling AGM, 0.4C or even higher is recommended.

Not always practical, e.g. for that 600 Ah bank would be 240A

but as close to that C rate as possible.

This despite the bank not accepting it for long, the fact that the current **is** higher than CAR spec for the vast majority of the 6-8hr charge cycle is what the makers have found to be healthy.

Obviously, off grid, solar won't give you that, but using high current FF sources for 1-2 hours in the morning, get up to 80-85% SoC before insolation kicks in, then using solar for the rest

really is the ideal combination.

Or, just replace your bank more often, if that seems too much trouble.

Of course if you're getting back to shore power once or twice a week, or driving for 8+ hours that often, that changes everything.
 

DiploStrat

Expedition Leader
Lifeline/Concorde is nuts, they call for up to 6C!!! Not 0.6C, but six times the capacity of the bank. The mind boggles. :eek:

So, size really does matter. My shore power charger tops out at about 100A.
 

IdaSHO

IDACAMPER
Ive got a 75A shore charger, but never need it.

Combine charging while driving and a good solar array, and we rarely need more power.
If we need more, I simply idle the truck when parked to pad our reserves,
or keep us in the green if we need to flip on a high draw device/appliance.

Reason #684 I love our gasser (over the old diesel)
Idling is clean, with essentially zero odor.
 

john61ct

Adventurer
Lifeline/Concorde is nuts, they call for up to 6C!!!
I've spoken with Justin and Dave Godber on this extensively. Their official "minimum" (if possible, for good longevity) is 0.2C

It was Dave V there whose published paper rocked the biz a couple decades ago. Enersys / Odyssey's reco "min" is 0.4C

I've never heard of 6C wrt lead in **any** context, that is just crazy talk!

link?
 

billiebob

Well-known member
Dual alternators, a standard feature on E350 Ambulances, and isolated, dedicated services for the truck and the house.
 

DiploStrat

Expedition Leader
I misspoke slightly. Can't copy and paste, but on page 19 of the Lifeline tech manual it quotes a max inrush of 5, not 6, C. As it turns out, most of us are more likely to have a problem on the minimum, rather than the maximum, at least once the banks pass about 400 Ah.

Seems we chat with the same folks!
 

DiploStrat

Expedition Leader
Ive got a 75A shore charger, but never need it.

Combine charging while driving and a good solar array, and we rarely need more power.
If we need more, I simply idle the truck when parked to pad our reserves,
or keep us in the green if we need to flip on a high draw device/appliance.

Reason #684 I love our gasser (over the old diesel)
Idling is clean, with essentially zero odor.
As you will note from some of the comments above, you may have a greater need for that 75A than you realize.

Idling is very useful when you want to run the microwave and the battery is low, but it will not appreciably charge the bank. And the key thing is that you want those long hours of absorb charge, after you hit "full" charge, and most of us never idle the engine for four+ hours. This is where a good solar set up is a lifesaver. (And a bad one; one that does not allow a long absorb stage, can hurt you.)

The key point is to avoid chronic undercharge.
 
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