DC-DC charger or ACR for sprinter build house batteries, and Lifeline vendor recommendations

[WithAlligators]

Hey folks, going to buy 6 660AH 2V lifelines for my Sprinter with 981W of PV up top. I'm pretty dialed in on the solar aspect of it, but looking for a good solution to charge the bank off the stock alternator. I had a Samlex ACR 160 in my last rig, and was happy with it. A 60A DC DC charger would put less strain on the alternator and allow me to upgrade to lithium if that ever becomes feasible. But the ACR will top off the starter when the sun is out, I don't know of any DC DC chargers that go of both ways.

DC DC charger pros:
Constant charge rate ( I think the batteries can't absorb more than 60A anyway, right?)
Lithium compatible
Less than 30% alternator capacity
Cons:
Won't top off starter
4 times as expensive as the Samlex ACR

ACR pros:
Cheap
Tops off starter
Cons:
Runs alternator at high load
Not good for lithium

What do you guys think?

Any suggestions for Lifeline vendors?

Cheers

 

[Joe917]

6 of those batteries are going to cost over $2000 and weigh over 400lbs giving a usable 330AH.
That is weight a Sprinter can't spare and money that would get you into lithium now.
With that much solar I doubt the need for any engine charging, we have 630watts and run solar almost exclusively. We have a battery to battery charger but it rarely gets used.

 

[DiploStrat]

What do I think? I am the charter member of the you-don't-need-a-B2B club. What I think can be found here: https://cookfb.files.wordpress.com/2016/09/battery-charge-slides.pdf

Read it and then decide for yourself.

 

[john61ct]

No B2B is two-way.

They are often not needed.

But sometimes they are.

The need is determined with actual measurements, try without first.

 

[john61ct]

Your Starter should not need topping up by solar.

Shift consumer loads run while engine is off to House.

How many hours per day are you planning to drive?

Your solar may well be sufficient.

Will you carry a little genny as well?

KISS as much as possible.

 

[DiploStrat]

If I understand your desired scenario, You can use a B2B and ACR.
B2B configured to be ’ign controlled, charges the house as expected. Solar connected to the house also.

Using a single sensing ACR connected to the house as primary battery, chassis ’batt as secondary. The ground/negative lead from ACR gets disconnected (relay for example) when ’ign is on.

The ACR will only close when the car is not running AND the house voltage is high enough to combine.

I actually run a variation of this - you need two relays, one of which is single throw/double pole.

 

[DiploStrat]

No B2B is two-way.

They are often not needed.

But sometimes they are.

The need is determined with actual measurements, try without first.

The CETEK D250S/SmartPass has a provision to maintain the starter battery.

You can also use an AMP-L-START. http://www.lslproducts.net/ALS_Overview_Page.html
(AM Solar has started using these with some of their LiFePO4 setups.)

The utility of maintaining your starter battery from your camper battery is debatable - can be very useful for those who live in cold climates and whose vehicles spend a few months in storage. YMMV.

 

[john61ct]

I was not referring to any built-in solar capability.

That is not an essential core part of B2B functionality, but an add-on not present on many other units.