Make alternator charge house battery better

How it works.
Be sure to use the left column to switch functions.

http://www.metrotrekkers.org/utility/electrical.htm

Check amperage at alternator and at the coach battery. Can be done on each side of the diode based isolator.

Do yourself a favor. Check alternator voltage right at the alternator output stud with low batteries. How much difference is there between the two?

Thanks for the replies....I think I will pick up a DC amp clamp and see what kind of amp flow I am getting into the house battery from the alternator. Then clean up all connections and check again.

I do have a portable 120 watt solar setup and it provides all the power I need, as long as it is sunny! I would just like to be able to get more from the alternator for cloudy days.

TYPEWRITERS, PAY PHONES, BUGGY WHIPS, DIODE ISOLATORS, TUBES, HUNTLY BRINKLY, PERCOLATORS, DIODE ISOLATORS, FLOOR STARTER BUTTONS, ADDING MACHINES, THE MILK MAN...

One is more useless and "yesterday" than the other. Problem is figuring out which...

check this out

Install this little device and your diode isolator is bypassed when any charging source is provided. For example, connected to shoreline your engine battery will get charge. With the engine running your house batteries will get charged. There is no voltage drop because it has a relay inside.

As mentioned, you need to clean up all connections. Take them off to clean them but take some picture before ever removing one wire.

This device could be hooked right to the diode isolator. Just need to ground the one lead and connect the two battery wires. There are other wires to allow some external controls but you won't need them.

This is the way it's done:

If you have a 150-amp alternator you choose a 200+ amp rated smart solenoid. I would trust a Blue Seas brand for this. Secondly, you must construct a bypass circuit with switch that can be closed in case of component failure.

Smart solenoids do not need a control on/off wire run to the dash.

I would not advise doing such a modification on a vehicle that has it's alternator's voltage regularor as part of the main ECU computer.

You can also do an alternative:

Mount a 3/8" stud terminal block near the engine.
Remove power wire from alternator, change the ring terminal to fit the terminal block stud.
Connect 2nd wire that runs to house batteries. I use 4 gauge or larger.

Make up a new wire that runs between alternator and new terminal block stud
Also 4 gauge. Most RV's I see have too small of wire running to the house batteries.

Regardless I srill recommend a Blue Seas smart solenoid.

wolfe10 wrote:

RV daytrader wrote:
Would this charge house battery better? Run a new heavy alternator wire to house battery first and use existing wire that goes from chassis battery to isolator to converter to house battery to charge the chassis battery ? This is in my class C.

Sorry, do not understand. There is no (or at least should be no) converter involved.

I suspect the converter was mentioned only because the wire run is physically routed that way on daytrader's motorhome—apparently it has a junction of some sort in the middle to connect the output of the converter to the battery. It's not germane to the discussion in any electrical sense.

Engine alternators should provide about 14.5 volts for charging. If you have that at the engine battery but not at the house batteries, work on the connections. As Enblethen mentioned, you might lose half a volt in a diode isolator so worth changing that to a relay type. And you can lose half a volt or more in a poor connection. I fixed connection losses totalling a full volt and noticeably improved my charging but even a full day of driving doesn't fully charge half discharged batteries.

The thing is, alternators are not all that great at fully charging batteries. Cars are okay if driven more than a couple of hours a day, but with much less driving, the engine battery is not fully charged, especially in winter when a good deal of charge is used to start the engine. Alternators are set to 14.5 or a bit less to avoid damage to the engine battery when driven all day.

The advantage of a good solar battery controller is that it is designed to charge the battery in stages with different voltages - and to effectively stop charging when the battery is fully charged. We might be able to get faster alternator charging by using a good battery controller to charge the batteries. Of course it would need well over 14.5 volts. Perhaps a heavy duty DC to DC voltage converter could provide that.

The great advantage of solar power is that it prevents the batteries from discharging so much and charges for a much longer time.

I would not use a "Electronic Isolator" at all! They will fail, and they always have a 1-2 volt drop across the diode too, so neither battery will charge right.

You are much better off with a 100 amp relay to connect the house battery to the chassis battery bank. Better yet, install a #4 wire from the alternator output to the coach battery via a 100 amp relay.

The relay is Grainger.com part #6C017 and rated for forklift use, with silver alloy contacts, rated for 100 amps on and off 100,000 times before failure.

Then the alternator to stock wiring with #6 wire will charge the engine battery, and the new #4 wire will charge the coach batteries effectively!

Better yet, spend the $400 and install 300 watts of solar panels, and it will keep the coach batteries full most of the time, and the alternator will not need to do the work to recharge the coach batteries.

SunElec.com They sell panels for close to $1 per rated watt!

I built my own panel mounts out of 6" long 2" angle aluminum, with 3 holes 3/16" for #10 screws into the roof, and 5/16" hole for a 1/4- 20" bolt into the solar panel frame.

I ran the power from the panels to the controller with #10 UV rated romex, (home Depot). Though the refrigerator vent into the closet next to my refrigerator.

Good luck!

Fred.