charging rates

FWIW:

The Trombetta DC solenoid with silver alloy contacts that I gave the link to above is rated at 225 amps continuous duty, and 600 amps inrush current.

But the important part for reliability with large RV battery banks being charged by high power engine alternators is the Trombetta solenoid's silver alloy contacts - that are immune to the normal corrosion of raw copper contacts.

It's this corrosion that causes the RV battery banks - gradually over time and at first unnoticed by RV'ers - to begin to not get charged as well as they should when driving. I noticed the charging voltage falloff because of my dual voltmeters right on the dash comparing engine DC voltage to coach DC voltage, but before that I was really getting frustrated arriving at campsites with the RV batteries still not charged much.

Here's more info on the DC contactor solenoid - the model is the 2nd line item on the specifications chart: http://www.trombetta.com/images/pdfs/dccontactors/bear/bear-family.pdf

My dual solenoids are rated at 200 amps continuous. Why? Because the OEM solenoid had burned contacts within a year and would not conduct.

I have seen the charge rate exceed the 70 amp rating on the field effect ammeter that I use. I have the dual charging paths protected with auto reset 50 amp circuit breakers. Why? Because I was blowing the OEM 60 amp fuse.

I have nice switches so that if I wish to limit or turn off the charging path all I need to do is flip the switch to cause the solenoids to disconnect. I can use it as a "poor man's" booster so long as I have the ignition turned on. Of course, when I move the key to the start position, the solenoids are no longer pulled into power the circuit.

Since I got the telcom jars I do not see significant charging of the house bank. As I said before I blame that on the computer that controls the alternator. I have seen as much as 8 amps going from the house bank to the engine while trundling down the road.

travelnutz wrote:
pianotuna,

Quote:

"The connection path is two #8 wires with solenoids. I do have the ability to turn them off. A third path is one way from house to engine via a Trik-L-Start module."

My very heavy duty charging system goes thru an 80 amp engine start solenoid under the hood that's available at most decent automotive stores or any store can order one for you. The #2 gauge copper cable current goes from the dual alternator positive current junction block directly to the 80 amp starter solenoid which is activated by slide switch control. The slide switch solenoid activation control under the hood right next to the solenoid. It's an emergency shut off if needed and disconnects my entire charging system going back. This under the hood switch gets its current from the truck's ignition thru an illuminated switch mounted in the cab on the bottom of the I/P on the lower left side. The solenoid can be activated (turned on or off) anytime by the in cab mounted control switch.

When either switch or the ignition is off, all batteries, truck and RV, are completely isolated even if the ignition is turned on. Total overall control is a must for me. Both switches and the ignition switch must be on to send charging current thru the two 80 amp marine fuses (one next to the solenoid and the other in the truck box at the 2 batteries there to the barrel switch on the RV and to the RV battery bank. Thus connecting all the batteries and the alternator together. The truck's ignition switch is the ultimate controller and will totally isolate the truck's starting batteries but still connect the 2 batteries in the bed with the 5 in the RV. Now have 7 big batteries when they are connected or 5 when not for the RV.

Truck starting/running battery/batteries dead? No Problem! Turn on the trucks ignition, your system switches on, use a cheap pre-made simple jumper wire with an alligator clip on both ends, jumper the solenoid activation terminal to connect the RV etc batteries to the truck engine starter circuit and turn the key and be on your way! Versatility designed in is where it's at! Charley Brown said it right, "Winning is such a beautiful word"!

Very simple and cheap to do if you take the time to think thru it. Cheaper than buying a manufactured isolator for your truck and have ultimate control and so easy to move to a new truck if wanted. Fit and works perfect on all 12 Volt systems and delivers real amperage of 80 amps to the RV batteries when needed for recharging quickly. Don't need an electrical engineering degree to do it either, just simple hand tools and a few hours.

A 12V activated DC 80 amp starter solenoid is only $26.99 today or a 250 amp constant with a 360 amp capacity short time capacity Perko marine barrel switch is $42.45 presently, so neither is expensive. Either will do the job of sending amps from batteries to start the vehicle's engine and especially if left connected for a couple minutes before turning the ignition key. An RV'er friend bought both last summer when we wired his truck to RV charging system.

#2 gauge or #4 gauge copper wire carries a whole lot more amps than an #8 gauge copper wire if you really want to recharge a battery bank of more than one battery in a short time. Using the vehicle chassis and the RV frame for the ground has a LOT of resistance and it's so much better and efficient to have both + and - large gauge copper wires/cables for the higher amps delivered charging circuit.

troubledwaters wrote:

Lwiddis wrote:
Why not install a solar system and use driving and generator for charging only when necessary? Solar for RVs isn't a fad or toy.

But for the same cost or less I could buy a generator that has multiple uses and is whole lot more easily moved from the RV to the house, hunting shack, cottage, or wherever.

You must love generators. 200 watts solar would work very well while on an RV adventure and the OP already has a built in generator.

troubledwaters wrote:
But for the same cost or less I could buy a generator that has multiple uses and is whole lot more easily moved from the RV to the house, hunting shack, cottage, or wherever.

X2. Right on.

I find that generator and alternator charging of our RV batteries puts charging under my control instead of Mother Nature's.

For the ultimate in flexibility for us hit-and-run RV campers, we can charge our RV batteries anytime, anywhere, 3 ways: Built-in generator, portable generator, and engine alternator.

However, we're part-time campers. Full-time folks camp in the same spot in the sun a lot more and since they're full-time, the cost of solar is just part of their living expenses that reduce messing with generators and their fuel.

Lwiddis wrote:
Why not install a solar system and use driving and generator for charging only when necessary? Solar for RVs isn't a fad or toy.

But for the same cost or less I could buy a generator that has multiple uses and is whole lot more easily moved from the RV to the house, hunting shack, cottage, or wherever.

Don,

My Itasca came with a momentary "boost" rocker switch on the dash. This activates a solenoid that interconnects the coach battery bank and engine start battery in parallel with each other. This switch permits "low battery rescue" in either direction -> While holding the rocker switch ON, the coach batteries can boost to help start the engine or the engine battery can boost to help start the built-in generator.

FWIW, here's the non-stock very heavy duty solenoid with silver coated contacts that I use for automatic interconnecting of the coach battery bank and engine start battery whenever the ignition is ON: https://www.amazon.com/Trombetta-Volt-Bear-Contactor-114-1211-020/dp/B007W2NBAU



Granted .... that solenoid is expensive .... but I got sick and tired of my coach batteries not getting properly charged when driving down the road. Now the two voltmeters I installed on the cab dash match up whenever we're traveling .... indicating that the 14.XX volts from the alternator is getting applied to the coach battery bank's terminals. The dash ammeter comfirms this, showing nice positive current flow into the coach batteries whenever we have been drycamping for awhile. I installed the ammeter shunt shunt such that a "positive" reading means current flow is into the coach batteries, and a "negative" reading means that current flow is out of the coach batteries. When this ammeter finally reads down around "zero", I know that my coach batteries are not accepting anymore current - thus they are fully charged.

Sometimes when drycamping, I start up the engine and idle it for around an hour and watch the ammeter until it reads under, say, 5 positive amps. I then finish up the coach battery bank charging with the little Honda portable powering the RV's stock 13.8 volt converter. The AGM coach batteries seem to like this routine.

pianotuna,

Quote:

"The connection path is two #8 wires with solenoids. I do have the ability to turn them off. A third path is one way from house to engine via a Trik-L-Start module."

My very heavy duty charging system goes thru an 80 amp engine start solenoid under the hood that's available at most decent automotive stores or any store can order one for you. The #2 gauge copper cable current goes from the dual alternator positive current junction block directly to the 80 amp starter solenoid which is activated by slide switch control. The slide switch solenoid activation control under the hood right next to the solenoid. It's an emergency shut off if needed and disconnects my entire charging system going back. This under the hood switch gets its current from the truck's ignition thru an illuminated switch mounted in the cab on the bottom of the I/P on the lower left side. The solenoid can be activated (turned on or off) anytime by the in cab mounted control switch.

When either switch or the ignition is off, all batteries, truck and RV, are completely isolated even if the ignition is turned on. Total overall control is a must for me. Both switches and the ignition switch must be on to send charging current thru the two 80 amp marine fuses (one next to the solenoid and the other in the truck box at the 2 batteries there to the barrel switch on the RV and to the RV battery bank. Thus connecting all the batteries and the alternator together. The truck's ignition switch is the ultimate controller and will totally isolate the truck's starting batteries but still connect the 2 batteries in the bed with the 5 in the RV. Now have 7 big batteries when they are connected or 5 when not for the RV.

Truck starting/running battery/batteries dead? No Problem! Turn on the trucks ignition, your system switches on, use a cheap pre-made simple jumper wire with an alligator clip on both ends, jumper the solenoid activation terminal to connect the RV etc batteries to the truck engine starter circuit and turn the key and be on your way! Versatility designed in is where it's at! Charley Brown said it right, "Winning is such a beautiful word"!

Very simple and cheap to do if you take the time to think thru it. Cheaper than buying a manufactured isolator for your truck and have ultimate control and so easy to move to a new truck if wanted. Fit and works perfect on all 12 Volt systems and delivers real amperage of 80 amps to the RV batteries when needed for recharging quickly. Don't need an electrical engineering degree to do it either, just simple hand tools and a few hours.

Hi Phil,

I'm basing the charging numbers on an ammeter that is between the engine and house bank. When I had all identical marine flooded jars I did see large current (up to over 70 amps) coming from the engine (if the house bank was hungry, or I placed a load (water heater) on the inverter). Now that I'm all AGM the house bank feeds the engine current. For example, if the solar panels are feeding 6 amps into the battery banks, there may be 8 amps going to the engine. I'm sure that the ecm limiting voltage to the alternator charging path is the issue.

A simple volt meter may not "tell the tale" on which way current is flowing.

The connection path is two #8 wires with solenoids. I do have the ability to turn them off. A third path is one way from house to engine via a Trik-L-Start module.

pnichols wrote:

pianotuna wrote:
I thought that might be because I had a flooded marine battery (from 2005) for the starter. I finally replaced that in 2017 in the spring with a AGM. I still get almost no charging for the house bank.

Don, perhaps your motorhome's engine alternator/engine battery/coach batteries interconnection system is different than my Itasca's.

I have two voltmeters and an ammeter mounted on the cab dash. One voltmeter shows the voltage on the engine's 12 volt system, the other voltmeter shows the voltage on the coach's 12 volt outlets, and the ammeter has it's shunt mounted in the main coach batteries' negative cable connected to the chassis frame.

The two voltmeters read within about 1/10 volt of each other all the time whenever the engine is running -> if and only if the interconnect solenoid (that activates from the ignition key) is activated AND has contacts in good conditon ... such that there is no resistance voltage drop across it's contacts (I've had to change it twice in 11 years).

As I drive down the road, both of the voltmeters track each other and slowly drop in voltage reading as the coach batteries charge up while driving. The ammeter drops down to near zero within a few hours of driving after camping - thus indicating that the coach batteries are no longer accepting charge current at whatever voltage the meters indicate.

This behavior leads me to believe that Winnebago has the engine battery and coach batteries wired in parallel with each other someway. Since the engine battery is liquid acid and the coach batteries are AGM, they're all getting charged together at the same voltage from the alternator, as indicated by the voltmeters. However as the coach batteries run down when drycamping, of course the engine battery doesn't run down - so the three batteries aren't in "hardwire/direct" parallel with each other ... BUT there is not a diode drop difference in the readings on the two voltmeters, so the engine and coach batteries are not isolated by simple diodes. Maybe there is some computer control of the engine battery charging that is separate, even though my two voltmeters show near identical voltage readings from the systems (engine 12V system and RV 12V system).

Whatever is going on it all plays together perfectly, even with mixed battery technologies. However the coach/engine batteries interconnect solenoid must have good contact surfaces for my situation. I wonder how many of these solenoids in RVs everywhere are activating all right, but introduce a voltage drop across there contacts after a few years with the RV owners not even aware of it. What this does is cause the coach batteries to never get charged adequately between campsites. The coach batteries are getting some charge, but not enough because of the reduced charging voltage on their terminals due to the voltage drop from the alternator created by the drop across the interconnect solenoid's contacts.

If you get 14.2+ on the actual house battery terminals for two hours between campsites I would not bother with the generator. If the drive is short or the voltage does not come up as expected then run the generator a couple hours during the drive.