DC to DC Charger, why? - Page 2

Grumpy · 02-14-2021, 01:55 PM

Quote:

Originally Posted by mini4mw

Interesting. I'll have to test mine out next time I pay her a visit in storage (gen) or have her at the house plugged in. I suppose if there is no secondary wires from charger/inverter direct to chassis battery there's no way to get power to it.

It is done through the emergency start circuit. That is the bi-directional relay referenced in the owner's manual.

It switches electronically through an isolator controller and closes the relay from what I understand so you won't see a specific charging circuit connecting the two battery banks. When we had our SENECA I think it was made by INTELETEK, but now it may be similar to what 75462 posted.

mini4mw · 02-14-2021, 02:57 PM

I'll have to get my volt meter out next time she's back at the house and I can plug in and see what power I can find. The aux switch is only 16GA from the drawing. Seems like it would be too small to handle any kind of load.

Grumpy · 02-14-2021, 03:05 PM

Quote:

Originally Posted by mini4mw

I'll have to get my volt meter out next time she's back at the house and I can plug in and see what power I can find. The aux switch is only 16GA from the drawing. Seems like it would be too small to handle any kind of load.

You will find battery cable between the auxiliary/emergency start relay and both battery banks that doesn't show on the schematics. Also the system is designed to only charge the chassis as needed. It is not a constant charge so there may be times you don't see a higher voltage with your meter.

mini4mw · 02-15-2021, 04:32 PM

I used the jayco form and asked about the charging and it 'should' charge the chassis battery when plugged into shore power or generator. They sent one similar to the wiring diagram bullitt attached and the attached pdf on the isolator. Now its just a matter of checking with a volt meter.

Bullitt6283 · 02-15-2021, 04:41 PM

To find out <for sure> what's going on, not only checking with a voltmeter, but also eyeballing what equipment is actually installed, is required.

I like the BIM shown on the pdf you attached. But for sure I know I don't have one. I would consider retrofitting one, but I already installed a Trik-L-Start.

.

Grumpy · 02-15-2021, 04:57 PM

Quote:

Originally Posted by Bullitt6283

To find out <for sure> what's going on, not only checking with a voltmeter, but also eyeballing what equipment is actually installed, is required.

I like the BIM shown on the pdf you attached. But for sure I know I don't have one.

It's a shame that Jayco documentation is so untrustworthy. I got a chuckle seeing that my owners manual says that I have a diesel generator and I may have to wait for the glow plugs to heat up.
.

Wonder what owner's manual they gave you since the one for a 2016 GREYHAWK on the web site doesn't reference charging the chassis with the converter.

Bullitt6283 · 02-15-2021, 05:17 PM

Quote:

Originally Posted by Grumpy

Wonder what owner's manual they gave you since the one for a 2016 GREYHAWK on the web site doesn't reference charging the chassis with the converter.

Jayco Link to the 2016 owners manual:
https://www.jayco.com/files/download...OM%20Color.pdf

See Page 81:

Grumpy · 02-15-2021, 05:39 PM

Quote:

Originally Posted by Bullitt6283

Jayco Link to the 2016 owners manual:
https://www.jayco.com/files/download...OM%20Color.pdf

See Page 81:

That is under transfer switch and not under batteries. The wording for 2018 and 2019 (page 84) has this wording which has been confirmed by JAYCO in the email to mini4mw. They do make upgrades as the years progress.

Battery Isolation Manager (If So Equipped)
Your motor home may be equipped with a Battery Isolation Manager that monitors the
battery voltage of both the chassis and house batteries over long periods of time. If it
senses a charging voltage it connects the two batteries together. If the charge system is
overburdened, it isolates both batteries. When batteries have reached a float charge state for
(1) hour, the batteries are isolated to prevent overcharging. It will reconnect if either battery
drops to approximately 80% charge and the other is being charged. If batteries are not being
charged they will be isolated to prevent an electrical draw in one system from depleting the
other battery.

jeepjeepster · 02-18-2021, 06:10 PM

If someone has answered this then just ignore my post, Ive not read all of the previous replies.

The main purpose of a DC to DC charger is to keep the voltage where the battery needs it to be to properly charge. A discharged battery naturally has a high resistance. By the time the load gets from the alternator, through the small wiring in the vehicle, through the 7 pin plug, and finally to the trailer battery, the voltage has dropped fairly low. More so if the trailer has some loads on it, such as a DC fridge, etc. Without the high volts, the battery will simply take forever to charge.

If you ran a big 4 AWG wire straight from the alternator to the trailer battery then you would be golden. Obviously that would be insanity.

kcmusa · 02-18-2021, 06:18 PM

Another use for a dc-dc charger would be someone that went to a 24v system to run a high power inverter but wants to use the 12v RV system for lights and such.
So they run 2 systems, 12 and 24v. Lots of solar forums talk about this.

craigav · 02-19-2021, 10:21 AM

Quote:

Originally Posted by Grumpy

Wonder what owner's manual they gave you since the one for a 2016 GREYHAWK on the web site doesn't reference charging the chassis with the converter.

While the thread here is about dc2dc charging, we have also discussed charging both the house and chassis batteries, and on mine, I am 100% sure that my chassis battery doesn't charge from either the converter or shore power. I have been jumping the relay under the hood which ties the house and chassis batteries together in parallel. I have plans now that I am retired to install the renogy dc2dc charger in mine as I already have purchased one and have a lithium house battery now.

I did notice in many versions of the class c owners manuals that mini4mw shared that indicates that both the house and chassis batteries will be charged... "(if so equipped)" even on the year model I have, well mine is not equipped with anything that allows the house or generator to charge the chassis battery.

I had two thoughts, one is to have a non-momentary switch for the aux start switch or go with what many of you have suggested and simply use a 120v trickle charger permanently wired in. In fact I have a trickle charger (maintainer) in my shop that is 5a and for marine use which is weather proof (perhaps water proof) that I had used on my boat which would work well.

I am still of the thought that a dc2dc charger is best to use for charging the RV house batteries when you have a bank of them, or you have lithium, primarily because they have the ability to limit the amps to something your wiring can handle and because the dc2dc chargers like I bought from renogy have profile settings for different battery types such as if you have a lead acid battery for the chassis (under the engine hood) and agm or lithium, etc., for the house battery. ~CA

mini4mw · 02-23-2021, 11:37 AM

I went out today for my somewhat monthly gen run and a 20 min drive.

I tested the chassis battery before starting anything up. 12.05V. I turned on the gen and when it kicked power on house power went from 13.4 (solar connected and charging) to 14.x. I let it run for 3-4 min and checked the chassis battery and it was at 12.7. I had forgot to turn on the master switch built into the unit and turned that on. I was also running an e-heater and I turned that off so there was no load on the gen. The radio came on automatically, which it always does (annoying). I checked again in 3-4 min, still 12.7 on chassis battery. Turned off radio and in another few minutes it was 12.15. So when I have the gen running it definitely charges the chassis battery. I never had the 450 motor running.

I am a little surprised 120v power came on with the built in master power switch off, but I suppose that makes sense since it is DC vs the gen cranking AC power.

The solenoid model number is 105751. Best description I can find is on the below site:
https://www.qualitymobilevideo.com/120-105751.html

Now just digging in a little further, b/c that's what I tend to do..
Attaching 2 pics. 1- solenoid under hood, 2 - chassis 12V wiring.
Note: I did not go looking for 2nd solenoid to charge from house to chassis battery.

Before the house master DC switch was turned on (built in from Jayco) the chassis battery was charging from gen as the voltage increased from multi-meter. If you look at the wiring diagram, there is, what appears to me, a straight connection from the converter (had power from gen) through a auto reset breaker to the coach battery.

The diagram doesn't show another solenoid from the house battery to the chassis battery, but I'm guessing its there somewhere. When I first go there, the chassis battery was 12.05. House battery voltage was 13.4, extra power from solar. If there was no solenoid based on the wiring doc, the house battery would have been charging the chassis battery and it would not have been so low. Once I started the gen, the chassis battery started charging. Some solenoid must have opened to allow that 'extra' power go from house to chassis.

Next time I'll look for the house battery solenoid ( I remember seeing something in shore cable compartment next to house battery slide) and test the house charging from alternator. I should have done it this time, just need to make a list..

craigav · 02-23-2021, 01:36 PM

If the converter was charging both the coach and chassis batteries the voltage would have been much closer to the same voltage on the coach and chassis batteries, unless the chassis battery was very low, and if so the voltages would still get closer to each other with a little time until they were equal voltage (or very close to equal voltage). I suspect the chassis battery voltage was just coming back up to its resting voltage and not actually charging from the converter.

BTW, do you have that diagram in a pdf that you can attach, my diagram doesn't show the converter as clearly as yours does. Thanks, Craig

Bullitt6283 · 02-23-2021, 02:35 PM

Something else is going on.

At your starting point, 12.05 chassis battery and 13.4 on the house battery, and the house battery was being charged by solar. Correct?
If there was something which was supposed to charge the chassis battery from the house side, it looks like it wasn't doing it.... Or at lease not until the house battery voltage is above 13.4.

The dash radio is powered by a pair of diodes, one coming from the house circuit and one from the chassis circuit. If one of the diodes is shorted, a bit of current may be flowing from the house circuit to the chassis circuit.

Interesting that when you turned off the radio the chassis battery voltage went down.
.

mini4mw · 02-23-2021, 03:17 PM

right, chassis battery 12.05 and house battery 13.4 being charged by solar when I got there. Fired up the gen and the chassis battery started charging from the converter (or at least that's the only explanation since chassis battery voltage increased over 10-15min with the gen running, 450 engine off). A few have referenced another battery isolator solenoid from the house battery to the chassis battery that only kicks in when shore power or gen power. Since my solar connects panels-> charger->battery, it doesn't hit any solenoid that would trigger it to connect to chassis battery. Its the only thing that would explain solar charging house battery high enough but chassis battery doesn't charge until gen was running. Well, maybe not the only thing, but its make logical sense..

craigav · 02-23-2021, 04:03 PM

However, if the chassis battery was charging, the voltage should have been in the mid to high 13's or low 14's. Another way to test is to have a helper press the "Aux Start" button while you are checking the chassis voltage (or perhaps you can set the meter where you can see it while pressing the button) and if the voltage comes up, then the converter wasn't charging the chassis battery. I say this with one caveat, earlier in this thread Grumpy stated that the chassis charge circuit only kicked in when the house batteries were sufficiently charged... (if so equipped) so if you have that option then that could be the case, but based on the voltages you shared, I don't think you have that option. I would check the voltage with and without the aux start button pushed and see what you get. ~CA

mini4mw · 03-18-2021, 06:02 PM

Brought the RV back to the house today to clean up and start another year.

I had the RV plugged in and monitored the power at the chassis battery. It was at 12.46. If I caught it at the right moment, the battery would go up to almost 13V. It would cycle up slowly, .1V a sec, reach 13 and then come right back down to 12.46. Sometimes it would hold an increase of just .2V and drop back down after less than a minute. It would not happen often and was hard to catch. At least a few minutes in between changes, but the battery is charging when plugged in.

If I hit the aux start button and monitored chassis battery it would go up 1V to 13.5 or so. I could also hear the solenoid click in the engine compartment when it was pressed.

If I ran the engine, the house battery would charge as expected.

I found the solenoid from the house battery to the chassis battery is in the same compartment as the house battery. Its attached all the way in the back of the battery drawer. I also found the lippert control for the leveling system is screwed into the roof of the same battery drawer. The solenoid for charging the chassis battery does have a fuse. Two pics attached. One from the side and the other under the chassis. Something to look at if the chassis is not charging when plugged in.

The Durakool chip attached to the solenoid is an auto temp sensor switch. Not 100% sure why the solenoid is so much bigger for the chassis battery than the one in the engine compartment other than it could have more amps going through it?

Grumpy · 03-18-2021, 06:34 PM

Quote:

Originally Posted by mini4mw

. Not 100% sure why the solenoid is so much bigger for the chassis battery than the one in the engine compartment other than it could have more amps going through it?

Isn't that the battery disconnect relay?

mini4mw · 03-19-2021, 11:18 AM

Grumpy, you are right. Here it is in the wiring diagram. I wonder what the 7amp fuse limits? I thought going back through the thread there was another solenoid from house to chassis that keeps the chassis from draining, but I guess it all works off the single solenoid under the hood.

As another note, the 50amp auto reset breaker is actually a 100amp on mine. Mounted on the opposite side of the battery disconnect. Those connections need to be cleaned up a little

RGD615 · 04-30-2021, 02:09 PM

Quote:

Originally Posted by mini4mw

Thanks Bullitt. I have 17 wiring PDFs from Jayco and I just triple checked and none had this detail. Based on this, I would think you could put a DC-DC charger after the 100a solenoid and utilize existing wiring?

Did you ever get your DC to DC charger installed? I am getting read install mine in my 2818 Greyhawk. Did you splice it into the wire on diagram between the solenoid and the mini breaker? This is a simple but confusing install. I want everything to work as it did before but only allow 20 amps to come from my alternator when the engine is running. Any advice would be welcomed. Richard

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