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Topic: Battery isolator charge vehicle battery on shore power
Posted By: jjrbus on 02/10/23 12:06pm

I have a new to me 02 Roadtrek on a Chevy chassis.
There is what looks to be a newer 4 post isolator,
I see no name brand or specs on it.
I have been RV'ing long time and never had an isolator before
and assumed they charged the vehicle battery when on shore power.

I am plugged in for a couple weeks
and everything is functioning properly.
My house battery is showing 13+ volts at the isolator terminal
and the vehicle battery is reading 12.25 volts at the isolator terminal.

Should this be charging the vehicle battery on shore power??

* This post was edited 02/11/23 11:22pm by an administrator/moderator *

Posted By: Grit dog on 02/10/23 01:48pm

I don’t know much about Cs but I wouldn’t think it typical
to charge the start battery off the RV converter.
Is it a voltage sensing isolator?
That latches and charges house battery when it sees charging voltage
from the vehicle. (IE vehicle running). Seems more plausible.

* This post was edited 02/11/23 11:27pm by an administrator/moderator *

Posted By: wolfe10 on 02/10/23 01:56pm

Most battery isolators charge both battery banks from the alternator when the engine is running.

Pretty easy to put your digital voltmeter on it and see whether it charges when the engine is running and/or when on shore power.

Yes, there are some battery combiners that will charge both banks anytime voltage is about a set level (indicating some charging source is on).

And, with any 19 year old vehicle, I would not ASSUME!

Brett Wolfe
Ex: 2003 Alpine 38'FDDS
Ex: 1997 Safari 35'
Ex: 1993 Foretravel U240

Diesel RV Club:http://www.dieselrvclub.org/

Posted By: wa8yxm on 02/10/23 03:44pm

Ok now the isolator is either a diode block (3 large posts one small and cooling fins) or a Solenoid (2 large posts two small ones)

First case: Diode iosolator: A diode is like a check valve on a water line. Current flows one way (The arrow points towards NEGATIVE or in this case the batteries) and the short charger cannot push power into the chassis battery.> Thankfully these are kind of rare.. though I have used them.

For the Solenoid... That's not the part that controls itself.. There is some means of controlling the solenoid.. Some are controlled by the alternator (If it's outputting the solenoid pulls in and charges) Most today are controlled by a computer... If it's the ECC (Engine Control Computer) than no.. there is no reverse charge

If it's an Intelletec Battery Control system or other type of B.I.R.D. (Bidirectional Isolator Relay Device) then yes.

How to tell the difference.

After a period of NOT PLUGGED IN (even 30 minutes to an hour will do)

Method 1: Turn on lights..then plug in and if say 1-5 minutes the lights brighten (I mean VEHICLE lights by the way) It's Bi-Directional

Method 2: (Better) Hook up digital voltmeter to a "Vehicle" test point.. You may have a fuse block under the dash or the battery itself.. NOTE voltage (Should be around 12.5 or 12.6) Now plug in and come back and see if it has gone up.. NOTE you may have to wait a short time (like 30min to an hour).. If it's now 13+ you have a Bi-Directional Isolator.


Method 3... IF the 12 volt accessory outlet in the dash is a "Chassis" device (often is) and hot with ignition off... There are plug in voltage indicators Some are digital Some are Multiple light...

Again if shore power charges the chassis. they will show an INCREASE if you plug in 30 minutes after shutting engine off.

I will save you some search time on that last option

https://www.amazon.com/Zeltauto-Cigarette-Lighter-Digital-Voltmeter/dp/B00VL9JZ0K/ref=asc_df_B00VL9JZ0K/?tag=hyprod-20&linkCode=df0&hvadid=312064685033&hvpos=&hvnetw=g&hvrand=15882270661183137423&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9017021&hvtargid=pla-568712381669&psc=1

Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times


Posted By: Bobbo on 02/10/23 05:41pm

When I had a Winnebago Class C motorhome, the chassis battery did not charge when plugged into the pedestal. After killing one chassis battery, I installed a Trik-L-Start to remedy that. I never had another problem with it. While that particular product appears to no longer be available, something similar should be.

Bobbo and Lin
2017 F-150 XLT 4x4 SuperCab w/Max Tow Package 3.5l EcoBoost V6
2017 Airstream Flying Cloud 23FB

Posted By: theoldwizard1 on 02/10/23 05:42pm

First. Battery "isolators" are old school. With modern vehicle charging systems, you will never be able to achieve 100% SOC on your house battery bank no matter what size wire you use.

Get rid of your isolator and replace it with a DC-DC charger. No, this will not charge you vehicle battery. Go buy an inexpensive battery tender or carry jumper cables that can go from your house battery bank to your vehicle starting battery or buy one of those hand held battery boosters.

Posted By: jjrbus on 02/10/23 07:00pm

Thanks for the responses, greatly appreciated.

Upon checking this is a diode type unit and does not and is not suppose to charge the vehicle battery from shore power. I assumed it did and even though sitting for a while it has never failed to start, luck I guess.

My 94 Toyota had the old fashioned Cole Herse isolator, looked like a Ford stater solenoid. I added a switch to connect the house side to the vehicle battery and turned it on when on shore power. Can I add a simple switch and wires
to this isolator to connect batteries when on shore power?

Posted By: wolfe10 on 02/11/23 06:01am

jjrbus wrote:

My 94 Toyota had the old fashioned Cole Herse isolator, looked like a Ford stater solenoid. I added a switch to connect the house side to the vehicle battery and turned it on when on shore power. Can I add a simple switch and wires to this isolator to connect batteries when on shore power?


Yes, you can add a solenoid-- common on most rigs and referred to as a battery boost or battery combine solenoid.

Be sure you get a CONSTANT DUTY solenoid rated at least 25% more than the max amp load it will be seeing.

Posted By: pianotuna on 02/11/23 07:39am

Hi,

I added an addition solenoid rated at 200 amps continuous. For the starter battery I added a Trik-L-Start. Today I'd chose a dc to DC charger.

Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

Posted By: jjrbus on 02/11/23 07:22pm

I do not understand why I would add a solenoid? Wouldn't I add a wire between the 2 battery terminals on the isolator with an inline 12 volt
switch??

Posted By: pianotuna on 02/11/23 09:23pm

jjrbus wrote:

I do not understand why I would add a solenoid? Wouldn't I add a wire between the 2 battery terminals on the isolator with an inline 12 volt
switch??


Diode based isolators tend to introduce voltage drop. Solenoid's do not, if the wire is sufficiently large.

A dc to DC charger may be best.

Posted By: jjrbus on 02/12/23 05:28am

I can run wires and do pretty impressive terminals and it has been a long time since I let the smoke out of anything. But I am not understanding why an added solenoid is needed and where to put it?

In my class A with a bit of instruction I added a battery selector switch, which worked well for the years I had it. In my Toyota a simple battery switch bypassing the solenoid served my purpose. My concern here is the van electronics, will adding a switch damage anything?

I did replace the OE converter with a Progressive Dynamics 9245 if that makes any difference.

Posted By: wolfe10 on 02/12/23 06:51am

Yes, of course you can just run a large-gauge wire from battery bank #1 to battery bank #2 with a switch in it. Can be at the batteries or any place you have large-gauge wires from both banks in close proximity. And, this is the KISS way of doing it. Wire size and switch amp rating should be high so if one battery is deeply discharged, you won't over heat the "connection" with high-amp transfer.

But, it is not automatic and that is what most people value over KISS.

Posted By: Gjac on 02/12/23 07:05am

jjrbus wrote:

I do not understand why I would add a solenoid? Wouldn't I add a wire between the 2 battery terminals on the isolator with an inline 12 volt
switch??
This is one way that is simple, another way that you probably have built into your chassis already, is to turn your key to ACC and that should combine both batteries. While plugged into shore power check both batteries to see if you get 13 plus volts.

Posted By: Grit dog on 02/12/23 08:55am

pianotuna wrote:

Hi,

I added an addition solenoid rated at 200 amps continuous. For the starter battery I added a Trik-L-Start. Today I'd chose a dc to DC charger.


You’re completely backwards on this. And misleading the OP. You’d never add a DCDC charger fed off of the converter, charging the start battery when shore power is plugged in…

2016 Ram 2500, MotorOps.ca EFIlive tuned, 5” turbo back, 6" lift on 37s
2017 Heartland Torque T29 - Sold.
Couple of Arctic Fox TCs - Sold

Posted By: Grit dog on 02/12/23 09:02am

jjrbus wrote:

I do not understand why I would add a solenoid? Wouldn't I add a wire between the 2 battery terminals on the isolator with an inline 12 volt
switch??

You still need to understand what the existing isolator is doing and if it’s working. Although it’s 99% likely its supposed to isolate the house bank when the vehicle is not running.
You haven’t posted enough info to show that you understand what’s wired how, currently.
Once you figure that out, you can work to achieve charging the start battery off of the converter in the most efficient way.
IMO adding more aftermarket switches that no one will understand except you as long as you actually remember is silly. But he’s a simple solenoid switched to whatever you want it to be switched to is an option and not a bad option. It’s also not dummy proof like an ACR.

Take the advice here carefully as there’s some bad intel in other posts.

Posted By: pianotuna on 02/12/23 01:08pm

wolfe10,

The wire size depends on what is wanted,

I added a voltage sensitive relay @13.5 volts (suggested by BFL13) from the house bank to the generator battery and deliberately used #20 wire to limit the amperage. It trickle charges the SiO2 that I used for the generator while in storage, and will power the remote electric start from Pinella's when the RV is in use. Since the battery is never "deep discharged" there is no risk of the wire becoming a fuse.

Posted By: jjrbus on 02/12/23 03:24pm

Again thanks for the input always greatly appreciated. Using the s
olenoid for an automatic disconnect did not sink in. Now I need to sort through normally open/closed solenoids. I do have a battery switch from another project so may use that.

Posted By: MrWizard on 02/13/23 06:16am

Diode based isolation is a one way device, it lets the alternator Charge the camper while the engine on, but keeps the camper from draining engine battery while camping, it does not charge the engine battery from the converter, too do that automatically requires a battery combiner system, its a two way charging control for charging house and engine batteries, from engine or generator/shore power, yet keeps them separated if there is no charging source available, the last thing most people want is to be boon docking someplace and have dead engine batteries ,

I can explain it to you.
But I Can Not understand it for you !
....

Connected using T-Mobile Home internet and Visible Phone service
1997 F53 Bounder 36s


Posted By: jjrbus on 02/13/23 07:34am

Am I looking at this right?? If I add a solenoid where do I get the 12 volt power from to activate the solenoid when on shore power?

[image]

Posted By: MrWizard on 02/13/23 06:35pm

Yes this is correct for what you are describing use a toggle switch, you can run a wire from the positive aux battery terminal (at the battery or at the solenoid) to the switch then from the switch back to the control terminal on the solenoid,
Most Motorhomes, come with an Aux/Emergency start button , which activates a momentary duty solenoid/relay , to connect the two battery systems for a built in jump start.
It Might be possible to replace that one with the new continues duty solenoid, then add the extra switch to turn it on , that would eliminate attaching more wires at the Diode isolator,

* This post was edited 02/13/23 06:51pm by MrWizard *

Posted By: MrWizard on 02/13/23 07:06pm

Gjac wrote:

jjrbus wrote:

I do not understand why I would add a solenoid? Wouldn't I add a wire between the 2 battery terminals on the isolator with an inline 12 volt
switch??
This is one way that is simple, another way that you probably have built into your chassis already, is to turn your key to ACC and that should combine both batteries. While plugged into shore power check both batteries to see if you get 13 plus volts.

Turning the key to acc is not going to change the way the Diode Isolator functions,
Turning key would only work if activating a combiner relay/solenoid
Is used instead of diode isolator

Posted By: jjrbus on 02/14/23 06:58am

I checked and I do not have a Aux/combiner switch. Seems I have some choices add a solar charger, small 120 volt trickle charger, switch, solenoid. Is there a simple easy way to make this automatic??

Posted By: Bobbo on 02/14/23 07:18am

Permanently mount a small 120v trickle charger and wire it to the RV's power center. When the RV is plugged in, the trickle charger will be working.

Posted By: jjrbus on 02/14/23 07:29pm

I have replaced the OE converter with a Progressive Dynamics 9245 so I have a modern charger. Been looking at Roadtrek and options. A simple battery switch would be my preferred route but I do not see a convenient place to mount the switch. I have a switch and some heavy wire so that would be the lest expensive route. I do like the KISS way of doing things. Keep it simple spiritually.

A continuous duty solenoid with a switch routed near the driver will be a bit more costly and time consuming and is the preferred route at the moment. Still open to ideas and suggestions. Likely be a couple weeks before I get to this.

Posted By: pianotuna on 02/14/23 07:56pm

jjrbus,

The best solution is a dc to DC charger. This will be automatic.

Second best is a solenoid that doesn't switch on until the voltage is 13.5 or higher.

I did opt for manual control of my twin 200 amp solenoids. But that was before dc to DC chargers were available at a cost that did not include your first born son.

Posted By: time2roll on 02/14/23 08:07pm

On 13.3 Off 12.8 140 amp relay $30 Amazon

2001 F150 SuperCrew
2006 Keystone Springdale 249FWBHLS
675w Solar pictures back up

Posted By: MrWizard on 02/15/23 01:50pm

You want the start battery to stay charged while parked at one spot, the easiest way, is install a disconnect on the start battery, no extra wire, no switches in the dash, no drain on the battery,
Cost About $10 at the Auto parts store
Not Automatic

Posted By: jjrbus on 02/15/23 08:31pm

The idea is to keep the battery charged when sitting next to the house. Traveling it has never been a problem.

Posted By: pianotuna on 02/15/23 09:59pm

jjrbus wrote:

The idea is to keep the battery charged when sitting next to the house. Traveling it has never been a problem.


That is why I added some solar with a trik-l-start on my class C.

For my car I added a timer and a 2 amp charger. I know the parasitic loss was about 3 amp-hours per day--so I charge it for 2 hours per day.

Posted By: Grit dog on 02/16/23 08:11am

pianotuna wrote:

jjrbus,

The best solution is a dc to DC charger. This will be automatic.

Second best is a solenoid that doesn't switch on until the voltage is 13.5 or higher.

I did opt for manual control of my twin 200 amp solenoids. But that was before dc to DC chargers were available at a cost that did not include your first born son.


You’re confused.
OP is taking aboot charging the start battery from shore power…. lol[emoticon]

* This post was edited 02/16/23 11:06am by Grit dog *

Posted By: Bobbo on 02/16/23 08:25pm

Grit dog wrote:

pianotuna wrote:

jjrbus,

The best solution is a dc to DC charger. This will be automatic.

Second best is a solenoid that doesn't switch on until the voltage is 13.5 or higher.

I did opt for manual control of my twin 200 amp solenoids. But that was before dc to DC chargers were available at a cost that did not include your first born son.


You’re confused.
OP is taking aboot charging the start battery from shore power…. lol[emoticon]

Or charge the house battery from shore power and the start battery from the house battery. That is what the old Trik-L-Start did.

Posted By: Grit dog on 02/16/23 09:54pm

^So does a new Trik L Start. It’s a mini DCDC charger.
It’s another way to skin the cat but it’s a poor way except maybe in the case of long term storage with solar maintainer already wired into the house setup.
Makes no sense to continuously draw from and cycle the house batteries, shortening their life, to charge the start battery.
Nvm the loss of efficiency with DCDC charging.
AND like usual folks aren’t answering the OPs question. He wants to charge start batt while on shore power WITH the perfectly good converter he already has. And he’s on the right track.
One could make a case diffenrt batteries different charging needs and batteries fighting each other figuratively. However on shore power with a high powered smart charger (converter) it’s going to keep the house at full SOC easily and any equalization between the 2 systems will happen pretty quick after combining them.

If not doing the above just plug in a 120v battery maintainer and keep ‘em separate.
Don’t complicate things.

Posted By: jjrbus on 02/17/23 05:51am

Thanks for all the input always greatly appreciated. I charged the vehicle battery in my class A with a selector switch. My Toyota I installed a solenoid bypass switch. The A I had for 10 years with no issue and the Toyota for 7 years with no issue.

I like the idea of the dual smart charger, if it fails is something else I will have to learn to troubleshoot. I do have a Progressive Dynamics smart charger so no ancient tech ruining batteries. I do not see a convenient place for a simple battery switch so will add a continuous duty solenoid and a switch by the driver.

Posted By: pianotuna on 02/17/23 07:41am

jjrbus,

Thanks for letting us know your decision.

Posted By: Grit dog on 02/17/23 09:08am

jjrbus wrote:

Thanks for all the input always greatly appreciated. I charged the vehicle battery in my class A with a selector switch. My Toyota I installed a solenoid bypass switch. The A I had for 10 years with no issue and the Toyota for 7 years with no issue.

I like the idea of the dual smart charger, if it fails is something else I will have to learn to troubleshoot. I do have a Progressive Dynamics smart charger so no ancient tech ruining batteries. I do not see a convenient place for a simple battery switch so will add a continuous duty solenoid and a switch by the driver.


That’s cheaper than an ACR. But serves the same function.

Posted By: Bobbo on 02/17/23 10:57am

Grit dog wrote:

^So does a new Trik L Start. It’s a mini DCDC charger.
It’s another way to skin the cat but it’s a poor way except maybe in the case of long term storage with solar maintainer already wired into the house setup.
Makes no sense to continuously draw from and cycle the house batteries, shortening their life, to charge the start battery.

I don't know about your DCDC charger, but the old Trik-L-Start didn't pull any power from the house battery unless it was at, at least, 13.2v. In other words, it didn't pull from the "battery," it pulled from the converter/charger charging the battery.

Grit dog wrote:

If not doing the above just plug in a 120v battery maintainer and keep ‘em separate.

Hence my original suggestion. Permanently install a 120v trickle charger and hardwire it to the breaker panel in the RV. Automatic and permanent.

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