fusing both batt w charging relay what issues to expect?

Perhaps not doornail dead as one put it but dead enough to blow a fuse. I have more experience on the diesel side. Your getting some excellent info. so ill just step back and watch.

How is your house battery grounded?

Since you are asking it to take power from engine battery to recharge, then all the current for house battery, engine battery and likely all the stock vehicle loads is now on the original alternator to engine battery cable, which was not intended to carry all this current.

You might consider either upgrading this OEM cable, or adding another thick parallel circuit from alternator + to engine battery, fused of course.

I prefer taking juice for house battery right from alternator (+) output stud rather than from engine battery.

If you are relying on the frame ground, well the original engine to battery ground is also going to have to carry the extra current of a depleted lifeline battrey, a large depleted lifeline AGM, which can suck up EVERYthing your alternator can make, especially the voltage regulator, which controls alternator output, is seeking 14.2v+. I recommend if you are using a frame ground, to add another ground from frame to an alternator bracket mounting bolt, and take extra steps to insure these remain low resistance and tight.

I would recommend not idling parked to recharge, as underhood airflow is quite limited when not moving, and a hot alternator is not a happy alternator, and it will get quite hot feeding a depleted lifeline 8d.

Also keep in mind your ford's voltage regulation is not always going to be asking for 14.2 to 14.4v, as lifeline wants when anything but 100% charged.

Lifeline wants your 8d battery to get no less than 51 amps when depleted to 50%, and you should not expect your alternator to meet this at idle, or perhaps at speed if your headlamps and blower motor are on.

Deeply cycled AGMS will get tickled to death by too light of charging currents, a bunch of low and slow solar, even to full every day, pisses them off. Your solar will barely do 20 amps in ideal conditions.

Its an expensive battery, you might want to ensure that it gets that 51+ amps from 50% SOC when you have grid power available and that you can hold it at 14.2 to 14.4v until amps taper to 1.275amps.

If you cannot properly feed that lifeline AGM, then do not expect it to live up to its venerable reputation.

A voltmeter on your dashboard revealing the Lifeline voltage. is wise, even though it will likely be dissappointing and ignorance is bliss until it is time to buy a new battery.

I have a hall effect sensor ammeter whose display is on my dashboard so i can see what my battery is accepting from the alternator when driving. Wonderful tool. The more amps the battery is accepting the lower its state of charge.

As a practical matter, I think you'd be pretty unlikely to blow one of the fuses under most circumstances. It's rare that the starting battery would be completely doornail dead, and the current that flows is determined by the charge acceptance rate of the battery at whatever voltage ends up there...which will be lower than the resting voltage of the house battery, both due to voltage drop in the wiring between the two and due to the voltage of the house battery drooping under load.

In the more typical case where the chassis battery has some charge but not enough to turn the engine over, it's still going to provide a reasonable amount of current to the starter when both are combined.

mchero, thats what I was told, if the starter battery is dead, turn the charging relay to the other position and let it send juice to the starter battery for 15 minutes or so, but assume before I new the starter battery was dead I would blow one of my 150 amp fuses. so larger fuses are needed,,,,correct?

What purpose do you plan for the ml-acr?

The ML-Series ACR automatically combines batteries during charging, and isolates batteries when there is no charging sensed on either battery bank.

Will solar charging cause the backward wiring to combine the batts?
Or do you plan to manually combine?

Also, lets say your starting battery is FLAT DEAD. Don't connect the house battery and immediately try and start the engine. Give the house battery a couple minutes to get some juice to the starting battery.

ok great info,, protecting wiring and to stop a catastrophe in case of an accident is why I put the fuses into the system, I will check on the 2/0 cable rating and buy new fuses, thanks

Fuses are generally used to protect wiring so you want a fuse that is appropriate for ampacity of the wire you are using. It has nothing to do with the alternator.

are you saying I should put in like 350amp fuses, someone mentioned I should only fuse it for 10% over the alternator output,but he didnt have all the info of my setup, he may have been speaking "in general". Im a newbie to this 12v stuff so I appreciate any help you can give.. I went to that link you sent and and it only went up to "00", I didnt see a rating for 2/0 wire,

blueh20 wrote:


I assume though if the house battery ever did try to start the vehicle with those fuses in place that the cranking amps would blow both fuses immediately, is this correct????

if so is their anyway to have the house battery start the vehicle while still having some kind of " frame shorting" protection ?


thanks for your input.

Basically, you're right. I believe one or the other 150 amp fuses would blow. You will need bigger fuses to provide starting current.

2/0 wire is rated for 190 amps CONTINUOUS DUTY at 90 degrees centigrade. Fortunately, a starter is not continuous duty, and it can carry larger current for a shorter period of time. The MAXIMUM FUSE for 2/0 wire is 400 amps, so I would put those on each end. See:

http://bdfuses.com/fusesnwires.php

If you blow the 400 amp fuse when you use it for starting, you will need to run a 3/0 or 4/0 wire in place of the 2/0 in order to run larger fuses.