fusing both batt w charging relay what issues to expect?

I have seen failures of parallel charge relays that PREVENTS FOREVER amperes from flowing by switch from priority HOUSE BATTERIES to chassis batteries. The engine start battery is drained and unless you take the time to manually connect cables together you is screwed. Jumping is rather a pain in the A$S on a crowded two lane highway, the middle of an intersection or straddling railroad tracks. The cure is to replace the relay. Then make the engine starting battery (chassis) the priority battery. Nothing in the way between the alternator and engine starting battery.

Wire a commercial fishing trawler where the main engines are isolated from the battery and before you know it you'll have a stout Danforth anchor chained to your ankles.

You said you ran 2awg cables, plural, under the van. That makes me think instead of attaching the lifeline - terminal to nearby frame as many would do, you ran a black cable all the way to engine battery, physically in parallel wth the red cable?

If so, I approve as frame grounds seem to become problematic all too soon.

Your blue seas relay is a fine unit, my only issue with it is that when either battery sees charging current, from any source, it will combine the battery banks. Sounds fine and dandy, but if the solar is holding the lifeline above the voltage setpoint of the Blue seas ACR. then the engine battery will be sucking up some of the solar wattage, rather than all of it feeding the depleted lifeline house battery. The engine battery might not require being held at these higher voltages and could be overcharged. it depends on whether you also slightly cycle the engine starting battery, which do not really like being cycled.

Your stated loads are quite small. Your system is quite overbuilt if your loads are not going to increase rather dramatically, or if you go days on end with no solar input.

As far as the 51 amps minimum, that is when the battery is regularly depleted to the 50% or below range. Lifeline batteries basically have no upper amperage limit, they can handle whatever, as long as the voltage does not get too high( 14.4v at 77F). A 8d lifeline at 50% state of charge can likely accept well over 200 amps for at least 20 minutes before the voltage at the battery terminals rises to 14.4v, so do not fear overamping this battery. Overvolting might be a brief possibility with the alternator's voltage regulator but really i do not know what fords do in this regard.


IF you were trying to max out the alternator contribution to depleted lifeline, you could either move the 2awg cable from engine battery to + alternator output stud, and the - to an alternator mounting bracket. This has the advantage of being able to eliminate one of the fuses. Fuses are supposed to be close to the battery terminal, and the original alternator charge cable to engine battery is likely already fused, so you do not need one in between alternator and ACR, but you do need one between ACR and Lifeline if you choose to move the cables.

If you choose to NOT run the 2awg cables to alternator, then the original alternator to engine battery charging circuit now will have to pass the charging current for the lifeline, and it was not intended to do this. It is likely much tinner than 2awg. So you can add another cable between alternator (+) output stud and the engine battery to remove this bottle neck.

If you have grounded the lifeline to the engine battery, the original engine to engine battery ground is going to also carry the lifeline carging current, and it too is likely undersized for the extra 50 amp load, and will cause a resistive electrical bottle neck, slowing down charging. You can do the same, either add another parallel cable, or replace the original cable with a thicker one, or both if you really want to go crazy.

But with the loads you have stated I think the extra maximizing of charge current steps are not needed. With the ACR being bidirectional, the solar will be recharging the engine battery, so self jumpstarting is extremely unlikely to ever be required. If it is, do as recommended previously. Press the manual connect, wait a minute or longer for the lifeline to feed/charge the depleted engine battery, and it is very unlikely the 140 amp fuse would blow when starting the engine.

Lifeline has a very good manual on what their batteries would like to maximize their performance and longevity.

http://lifelinebatteries.com/wp-content/uploads/2015/12/6-0101-Rev-E-Lifeline-Technical-Manual.pdf

Rolls surrette also have a very well written manual that can help a Newb to lead acid battery living understand what batteries require to perform well and last a long time.

http://rollsbattery.com/public/docs/user_manual/Rolls_Battery_Manual.pdf

If you were to say, add a microwave and a 2KW inverter to power it and nuke 3 meals a day, then you would want to maximize alternator contribution and perhaps even run engine and microwave at same time, but the ARB fridge, and some USB ports are not going to put much of a dent in the 8d lifeline.

Read the Lifeline and rolls manuals more than once, slowly.

MEXICOWANDERER wrote:
The priority battery should be direct and the aux battery charged by the relay.

sorry blue I thought there was a main and aux, there is not. If either is being charged above 13v then the batteries combine.

NOTES: Stud terminals A and B are interchangeable. Either battery bank can be connected to A or B.
If the ACR is to be used for cross connect, fuses between ACR terminals A and B and each battery
positive are not required according to ABYC guidelines. If the ACR is not used for cross connect,
install fuses to prevent a hazard if there is damage to the wires connecting the batteries to the ACR.
The fuses should be placed as close as possible to the batteries so that most of the wire is protected.

blueh20 wrote:
mexicowanderer, this acr has a 10sec. rating of 2000 amps, cranking 1 minute of 750amps.
I think the priority battery that the original owner set this up to be is the house battery, to keep the arb fridge going on cloudy days.

"NEVER put any component in the way of having the prime starter battery getting charged."

I am not sure whats in the way of the prime battery getting charged, the house battery doesnt draw off the start batt if the house batt drops under 13v.

blue you need to ignore his comment, they are based on isolator's, this is not an isolator, there is no main/aux on these like i told you, whatever side hits 13v first connects the relay, similar to what mex is saying with the ford relay.

seems as though I am making a mountain out of a mole hill, have to take some (lots)time and re read all this info, thanks folks for sharing. I really appreciate it.

mexicowanderer, this acr has a 10sec. rating of 2000 amps, cranking 1 minute of 750amps.
I think the priority battery that the original owner set this up to be is the house battery, to keep the arb fridge going on cloudy days.

"NEVER put any component in the way of having the prime starter battery getting charged."

I am not sure whats in the way of the prime battery getting charged, the house battery doesnt draw off the start batt if the house batt drops under 13v.

read what i wrote, it only benefits you, your relay is rated 500A continuous.

your loads are practically nothing, there is no concern for your alternator, again, most rv's have this same design built in, people have you concerned over an alternator for no reason

Not only can I turn the relay off I also put a disconnect switch right at my house battery which is 10" from the relay and two feet from the battery..
So maybe I ought to just leave the two systems separated all the time so as to not stress out my alternator/regulator and that way I can figure out if the solar is up to the task of keeping house appliances going on its own, I only have:

led lights=1amp draw
dual usb charger= says "fast charge 4.8amp"
arb fridge=says 1.5 amps per hour(which is average rating)
adding flojet water pump=says 7.5 amps at full pressure, which will have very slight intermittent use.

and then only use the ACR if I ever get a dead starter battery? if this is the case it doesnt seem worth it to have those 2/0 battery cables all stretched through the frame and worrying about it shorting out or destroying the alt..thoughts

The priority battery should be direct and the aux battery charged by the relay.

Relays have ratings. The 200 amp models can see 300 amps for cranking purposes.

But a parallel Ford starter relay is max rated for eight hundred amperes and they take the strain off the charge relay.

NEVER put any component in the way of having the prime starter battery getting charged.

like i said it bi direction, either side can charge either side

if the car is running, the alternator is charging, when the starter battery gets over 13v it connects the house battery, then the alternator charges the house battery

if the car is off, the solar/generator/shore power charges the house battery, when it gets to 13v to connects the starter battery and charges that battery


your making a big deal out of the relay for no reason, you should be in auto mode 99% of the time.

let it do its job and forget about it, there is a led on the relay itself that shows what mode it is in, if you care

leave it alone in my opinion it only benefits you.

this is no different then a isolator which is standard in rv's, with the added benefit this unit will charge the starter battery, isolator's don't

your alternator will be fine, if you still don't want it, i'll be more then happy to pay for shipping to my house for it :-)