2003 adventurer 35U dc-dc charger install

[Nollsemic]

I’m in need to upgrade my coach batteries so it’s got me thinking about going lithium where I’ll be adding panels this summer. My question is do I remove the isolator and tap into the 12 v cable coming from the front to hook up my dc-dc charger? Or should I just run a new cable to the alternator.

[powercat_ras]

There is already cabling between the chassis and the chassis side of the battery isolation contactor in the Chassis Electrical Box that can handle at least 100 amps. This is where I connected the input side of a Renogy 40 amp output DC-DC charger in my Vista.

It is recommended to locate the dc-dc charger close to the coach batteries being charged. Most if not all are not water proof and need to be installed in a dry location.

You'll want to reconfigure the battery isolation contactor so it can't connect the chassis side to the coach side when the IGN switch is in the RUN position.

The BIM control module Winnebago used in 2015 had three control inputs, one input had ignition RUN on it, another had Battery Boost switch on it, and one had AC Generator RUN on it. It had logic to not connect if there was 12VDC on the AC generator input and the IGN input so that the AC charger powered by the generator and the Alternator would never be trying to charge the coach batteries at the same time. I believe this was to prevent a higher voltage from the chassis side trying to back feed into a converter-charger trying to put out a lower one. I was able to double feed the GEN input with a dual diode so that when there 12 V on the IGN it also fed the GEN input too.

Doing this, with IGN off the BIM control module can still connect with IGN off to charge the Chassis battery from the Coach side as before.

The premium versions of the 2015 Vista (that they started calling Vista LX in 2016) used the Precison Circuits Battery Isolation Manager, 00-10021-000. They might have already been using that unit in 2003.

[Nollsemic]

Thanks Randy as soon as it stops snowing I’ll take another look in there

[powercat_ras]

Attached is an image of what's behind the circuit breaker panel in a 2015 Vista 27N Chassis Electrical Box, there are the 2 contactors for the chassis and coach disconnect switches and in the center the Coach-Chassis Battery Isolator, with it's control module on it's contactor.

You could even connect the output of the DC-DC there, too if the chassis electrical box is located fairly close to the coach batteries.

[creativepart]

I removed the BIM and when I installed the DC2DC charger I wired it directly to the chassis battery. I wanted to have easy access to that wiring and while the chassis side of the disconnect solenoids would work fine it is not the definition of easy access for future needs.

I also used the Victron Dc2Dc charger because it can auto sense ignition without running additional wiring.

[Nollsemic]

Thanks also for the info, I was looking to purchase the victors for that same reason.

[Morich]

Small heads up before looking for the BIM as your age group has a "mode solenoid" rather than BIM. Does much the same but looks/operates quite different.
Electro- mech instead of more solid state. Lots of changes made from 2003 - now!
Sheet one , this drawing:
https://www.winnebago.com/Files/File...ire_141254.pdf

[Nollsemic]

Thanks Richard, I followed the link you posted and see the battery mode solenoid also the the battery disconnect relay next to it. I’ll have to do a little more research on just what each unit is used for and where to add the charger.

[Morich]

It works much the same as a Battery isolator (BIM) but uses a solenoid. There is a wire labeled LR that comes from the dash area to power/operate the solenoid at two different times. One is when we push the dash switch, labeled Aux, boost, or sometimes other things as a way to jump start a weak chassis battery.
That LR is also hot when the ignition key is on as a way to connect both coach and chassis batteries together to get the coach charged as we drive.
It's an area that comes up frequently here as the solenoid takes a beating and tends to corrode and stop making contact!
Basic idea is that there are often two wires f5rom the dash, LR for hot lead and FMfor ground on the four post solenoid. Some RV use three post solenoids and just use the mounting screw as ground but both operate the same.
Two big lugs have coach battery cable on one side and chassis battery on the other big lug and they get tied together when the solenoid is operated.
BIM has close to the same but we can't see and feel it move!! Push the dash switch and we can often hear the big old solenoid thump. That doesn't mean the contacts made but we can hear it tried?

When you get into it further, you may want some more info on how Winnebago does things and there is a good bit of info here or following the link below and left on first page of drawings.
https://www.winnebago.com/Files/File...agram/Help.pdf

[Nollsemic]

Got a bit of reading for the weekend, thanks for the info

[Nollsemic]

So am I overthinking this?
Should the dc-dc charger go between the battery mode solenoid and the lifepo4?

[Morich]

I better back off and let the folks who have done this conversion answer as I have not done the DC-DC thing!