Using engine battery to recharge camper battery while driving

[MontereyDave]

A mechanic tested my camper battery with and without my engine running and told me that my camper battery is not even connected to my engine battery. I guess the only way to recharge my camper battery currently is to plug in to an electrical outlet.

I searched for DIYs but couldn't find one. How difficult would it be to connect my camper battery to the engine battery so that it will recharge while I'm driving down the road? And, perhaps include an on/off switch in the wire so I can protect my engine battery from running down when I park to camp?

[Maineah]

It's probably best to find another mechanic that understands camper systems. It was at some point connected through a battery isolator of some sort and probably still is. If it is not charging the coach battery there is an issue with the isolator. It's not overly complex but if you are not comfortable with wiring it maybe be better to find a friend that is. You'll need some tools, if this is some thing you might want to tackle let us know and we'll try to walk you through it.

[MontereyDave]

It's probably best to find another mechanic that understands camper systems. It was at some point connected through a battery isolator of some sort and probably still is. If it is not charging the coach battery there is an issue with the isolator. It's not overly complex but if you are not comfortable with wiring it maybe be better to find a friend that is. You'll need some tools, if this is some thing you might want to tackle let us know and we'll try to walk you through it.

Thank you, Maineah. At least now I know what to ask the mechanic to repair/replace. I'll take it to a place that specializes in RVs and I'll ask him to check out the isolator.

[Derek up North]

Very simple to change. 3 (or 4) wires to connect at most.

[waiter]

Connecting your coach battery to your truck battery is easy, just turn on your ignition. :-)

I've been considering installing a bypass switch on my dash. This would allow me to connect the two batteries together thru a 15 or 20 amp fuse or breaker. This switch isn't to be used for starting, but to be used for keeping the truck battery charged while plugged into shore power for long periods of time (weeks/months)

John Mc

88 Dolphin 4 Auto

[stamar]

Take a picture of where the battery is for us

There's going to be one ground, one connection to the front battery and isolator, one connection to the 12 volt system and one connection to the charger.

The isolator is under the hood. Cylinder with three prongs somewhere on the firewall.

All of them came with this but its possible to remove.

[stamar]

Connecting your coach battery to your truck battery is easy, just turn on your ignition. :-)

I've been considering installing a bypass switch on my dash. This would allow me to connect the two batteries together thru a 15 or 20 amp fuse or breaker. This switch isn't to be used for starting, but to be used for keeping the truck battery charged while plugged into shore power for long periods of time (weeks/months)

John Mc

88 Dolphin 4 Auto

Disconnect the cord from one side of the isolator and connect it to the other side. Either side actually.

Does not need another 15 amp fuse its already between the charger and the deep cell.

[zero]

A mechanic tested my camper battery with and without my engine running and told me that my camper battery is not even connected to my engine battery. I guess the only way to recharge my camper battery currently is to plug in to an electrical outlet.

I searched for DIYs but couldn't find one. How difficult would it be to connect my camper battery to the engine battery so that it will recharge while I'm driving down the road? And, perhaps include an on/off switch in the wire so I can protect my engine battery from running down when I park to camp?

The most reliable way to do it that I've found is to use a relay. The relay gets energized by your igniton circuit when the key igntion switch is "on." So when you start the vehicle - your cranking battery and your RV batterie are tied together in parallel and charge. When the key is "off" they are totally separated. You just have to make sure you use a relay that can handle what ever amperage your alternator is capable of - and also use wire size adequate to do the same. My rig has the starting battery up front and two RV batteries in back 16 feet distant from the alternator. I have a relay capable of carrying 100 amps and use # 2 copper for the 16 feet run. It's good for 80 amps of charging. You can get by with much smaller wire if the RV battery is closer to the alternator and/or the amp-output of the alternator is less. You can buy a good HD 100 amp rated relay for $20. To energize it only draws 2 amps and is no problem hooking it into the igntion circuit. Just make sure you find a "full time" relay and not an "intermittent duty" relay.

A cheaper and simpler way to do it with an isolation diode. I don't like them but work well enough for small systems. My 1978 Toyota Chinook came standard with an isolation diode instead of a relay.

[Vanman]

I prefer the relay kind by Tekonsha, the cheaper ones I would stay away from:

http://www.pplmotorh...y-switch-rv.htm .or

http://www.amazon.co...attery isolator

I downloaded a PDF from them that says a 25-30 Amp ckt breaker should be installed rite off the red battery lead on the wire to the isolator which most RV makers don't do. ANY lead off the hot side of the battery should go straight to a current protector, fuse or ckt breaker. Most RV coach builders provide one on the feed side of the isolator to the coach battery. Our Dolphin had 2, one off the isolator and another on the side of the battery box, but none on the wire that connects to the battery then runs all over to engine bay over to the isolator.

While your doing this think about how all vehicle manufacturers provide insulation on all hot side wires, connections, terminals. Look at your isolator from the coach builder. OPPS, none.

Small pieces of plastic tubing slit along the side will slide easily over these exposed "hot spots" and might well save a bad thing happening later down the road. Cheap and easy to do.

vanman

[Maineah]

There are two types of isolators all though they do the same thing they do not work the same. Know what you are dealing with before you start tinkering or you may let the smoke out of some thing. Waiter is doing some thing entirely different from the normal charging system, he knows what he is doing.

[waiter]

Dave - not sure your question got answered.

Your Toyhouse should have an "Isolator". It may look like this, on the firewall of your truck. As others mentioned, this is a high amperage relay, (kind of looks like an old ford starter relay) thats used to "isolate" the coach and truck battery.

When you start your truck, the relay energizes and the coach battery is electrically connected to the truck battery, and the coach battery should charge.

If your coach battery isn't charging from the truck, then it could be a number of things. I strongly recommend you purchase a el-cheepo volt meter and learn some very basic methods to use it.

Troubleshooting this problem should take about 15 minutes if your capable of using the voltmeter.

Using the voltmeter, check the voltage on both sides of the isolater, with and without the truck running. This will tell you if the isolator is energizing, and also if the circuitbreaker feeding the isolator is OK.

Typically, the voltages will read 12-13 volts on both sides of the isolator with the truck off. The voltage your reading is the actual battery voltage for the truck, and the coach, so they may be different.

When you start the truck, the isolator should energize, connecting the coach battery to the truck, at this point, you should read 14.0 to 14.5 volts, and both posts on the isolator should read exactly the same (14.0 to 14.5)

This photo is of my original "Converter". This supplies 12 volts when plugged into shore power (the lower part) and the acts as the distribution/fuse panel for 12 volts (upper right)

John Mc

88 Dolphin 4 Auto

[zero]

I prefer the relay kind by Tekonsha, the cheaper ones I would stay away from:

The relay that Tekonsha sells is rated at 80 amps continuous and draws less then 1 amp. It's bascially the same full-time low-draw relay that most places sell for dual-battery use IF a low charge rate is used.

That's the relay I call "cheap" in my referernce frame. The more pricey one at $50 is rated 200 amps and is water-proof. All depends on what kind of charging system is being used and how fast you want your RV batteries to charge. If you have a couple of HD deep-cycle batteries that have run appliances for an entire day or night before a recharge - they can call for a lot. In my rig - I use an AC refrigerator powered by an inverter and the RV batteries , I like this setup much better then the 3-way fridge it used to have. My batteries only will run the AC fridge for four days with no recharge.

Many modern alternators can charge at 80-100 amps at engine idle speed. You hook that to a 30 amp breaker that breaker will keep tripping and overheating until it gets ruined. My Toyota has a 140 amp alternator that can charge 90 amps at at engine idle speed and if I revv it up - it can send 140 amps to the back RV batteries. I've got #2 copper going all the way back with a 150 amp fuse on each end. Tis along with the HD 200 amp full-time rated relay.

Obviously if you only have a 50 amp max alternator that charges 25 amps at engine idle - using the heavy stuff is not necessary.

[zero]

I prefer the relay kind by Tekonsha, the cheaper ones I would stay away from:

If anyone is a bargain hunter - those relays that Tekonsha sells can be bought for $12 apiece from several suplus outfits. 80 amp full-time rated and 150 amp surge.

Here's another place showing the many versions . .

[Maineah]

Most Toy homes are wired with a # 8 wire going to the coach battery you can't get much over 30 amps down it with a hammer. But in a stock system that's sufficient. I think we all have lost track of the OP's original problem he does not know how to fix his problem hence he is taking it to a repair shop, haven't seen one yet with out a system of some sort. I do not know what he does for a living but if it has any thing to do with spelling or book work I'm out. The relay site is a good one but if he has a solid state isolator it won't do him much good. If he is stating from scratch or needs a new solenoid that's a good choice.

[Vanman]

If you are going to get a relay type I would stay away from the cheaper copies of the Teckonsha, at the price of the above link I would be surprised if it was one. You can get heavier duty relays, but, as Maineah noted, for the wiring and alternator of a stock Toy not really necessary.

vanman

[zero]

If you are going to get a relay type I would stay away from the cheaper copies of the Teckonsha, at the price of the above link I would be surprised if it was one. You can get heavier duty relays, but, as Maineah noted, for the wiring and alternator of a stock Toy not really necessary.

vanman

I'm not sure what you mean by "cheaper." Less in cost or less in quality? Tekonsha as the original electrical parts company does not even exist anymore. They were bought out 10 years ago. The relays the company (with the Tekonsha name) sells are the same quality as I sometimes buy for half the price. Places like Surplus-Sales buys over-runs from large companies and often it's top grade merchandise. The reputable relay sellers give full specs as to amp carrying ability, material the contactors are made of, and how many duty cycles they are designed to last. The sellers are rarely the companies that actually make the relays.

As to the guy's original question about his motorhome and no charging for his RV battery? All depends on what he has or doesn't have. RVs often get modified bv owners over time. I don't know what his rig had when new and have no idea what it has now. That being said - there are two usual ways to do it. Use a relay or use an isolation diode. Isolators are often low amp capacity. My Toyota Chinook came OEM with a 30 amps max to the aux battery rated isolator and it was removed a long, long time ago. I've also found that most isolators trim the charge peak voltage down a bit to the RV battery. Often 2/10ths to 1/2 of a volt less then what is coming out the alternator's reg- which is something that does not happen with relays. Automotive alternators designed to charge cranking batteries . . . when working perfectly . . .do not charge deep cycle batteries at an optimum level and many isolators make it even worse.

Back again to the original poster - without more info - it' possible he just has a wire unhooked or a fuse blown somewhere. Without more info - much is a guess.

[stamar]

i bet someone mentioned this but what we have is not really an isolator but a relay.

I had an 89 dodge campervan with a real isolator. they cost at least 70 and up.

Once the car has started the two batteries aren't isolated at all but they are connected to each other. this can create a potential no start situation and happened to me with my 79 dolphin and its dead coach battery. and brought about the death of its cab battery. I had to replace it before i sold it.

it might be called an isolator and a relay but its not really an isolator. unfortunately it doesn't exactly have its own name its really a 2nd battery isolated relay or something.

edit modern toyhomes could have a real isolator circuit, the ones that came with the generator and all. im talking about the 88 and older ones they all have the pictured cylinder relay switch.

toyhomes also have a common problem of making the front battery explode when jump started because the rear battery is not isolated from the front once its running.

[zero]

i bet someone mentioned this but what we have is not really an isolator but a relay.

I had an 89 dodge campervan with a real isolator. they cost at least 70 and up.

Once the car has started the two batteries aren't isolated at all but they are connected to each other. this can create a potential no start situation and happened to me with my 79 dolphin and its dead coach battery. and brought about the death of its cab battery. I had to replace it before i sold it.

it might be called an isolator and a relay but its not really an isolator. unfortunately it doesn't exactly have its own name its really a 2nd battery isolated relay or something.

edit modern toyhomes could have a real isolator circuit, the ones that came with the generator and all. im talking about the 88 and older ones they all have the pictured cylinder relay switch.

toyhomes also have a common problem of making the front battery explode when jump started because the rear battery is not isolated from the front once its running.

No system is 100% perfect for every situation. An isolation relay can be easily wired so is automatically energized via the ignition circuit whenever the key is on .; . . and also have a manual cut-out switch. All mine are like that. So yes - with a relay - you can have the batteries absolutely isolated with the engine running or not running. It's a very reliable way to do it. I don't like the rectifier type isolators since all I've tested have a voltage drop across them and I don't like that loss. I use my cut-out switch because . . . if the RV batteries are very run down - I don't want them instantly connected to my cranking batteries until the engine is started and the cranking batteries are fully recharged. Especially in my diesel RVs that use 80 amps to heat glow plugs for 20 seconds before the starter even cranks.

A unitized solid-state isolator with rectifiers inside always diverts alternator charge power onto the two circuits (cranking circuit and the RV "house" circuit). You can never turn it :"off." unless you unhook the wires. If one battery has gone bad, it can rob near all the charge current from the alternator and the other good battery gets very little. Whatever battery has the least voltage will get the most charge current.

There is a third device called a "battery to battery" charger. Often used in marine use. It's expensive but offers another alternative. In fact, you can get one that takes normal "cranking battery"type charge profile from the first battery - change it into a deep-cycle battery profile and then send that to the RV battery.

[Maineah]

The last item is called a combiner. They are smart relays that sense battery voltage on both batteries. Generally they work this way, the engine starts the combiner does not connect to the coach battery until the truck battery has reached 13.2 volts for a period of time, it will then connect and charge the coach battery. Once the engine is turn off the batteries will remain connected until the coach battery drops to 12.7 (fully charged battery) equalizing both batteries then disconnect. This process will work in reverse if you plug in the MH the charger (connected to the coach battery) brings up the coach battery to 13.2 volts then will connect to the truck battery and charge it also. Blue Sea sells them but their web site maybe confusing and they are expensive because they are used on multiple battery banks another one is Cole Hersee http://www.ase-supply.com/category_s/32.htm . The smaller one (48525 85 amp) is fine unless you have upgraded your wiring and are using a bigger alternator. I have one in service that has been working flawlessly for 6 years.

[zero]

The last item is called a combiner. T

There ARE units actually called "battery to battery chargers. Here is one description. This is from the manual for the "Digital Solutions" Pro-mariner, Digital Mobil Charger, four stage, battery to battery charger, model # 05504 (for 12 volt battery to 12 volt battery). It can allow to have an RV alternator charge the cranking battery with a different charge-profile then the RV deep-cycle battery.

Digital Mobile Charge Overview :

The best way to charge a battery is using a 4 step battery charging curve, which cannot be

achieved from a standard alternator. Additionally a standard alternator cannot output a large

enough charge to power an auxiliary battery bank.

First and foremost, On Board Solutions’ Digital Mobile Charge ensures at all times that the power

required to run the primary system of the vehicle or boat engine is not affected. The engine start

battery is constantly monitored and receives top charging priority. The surplus power created by

fooling the alternator is amplified into a higher voltage by the Digital Mobile Charge and is used to

charge a secondary battery bank using a totally isolated digitally controlled 4 step charging curve.

The engine start battery cannot discharge through this system, even in the event of a unit failure.

In summary, the Digital Mobile Charge provides your extra battery system a charge that is

approximately 5 times faster than could be achieved in using the vehicles alternator. This provides

in-transit charging of extra battery banks and increases the life of the batteries by de-sulphating

them. The Digital Mobile Charge provides the same utility as an advanced regulator, a zero loss

battery isolator, and a 4 step battery charger.

[Maineah]

That's a pretty complex unit a bit over the top for a little MH great for a large boat. The $500+ cost puts me off a bit too. A modern converter/charger in the RV basically does the same thing as far as charging, we have the benefit of being able to plug it into a generator or power point not so with a boat out to sea.

[Derek up North]

That certainly throws the K.I.S.S. principal out the window.

[zero]

That's a pretty complex unit a bit over the top for a little MH great for a large boat. The $500+ cost puts me off a bit too. A modern converter/charger in the RV basically does the same thing as far as charging, we have the benefit of being able to plug it into a generator or power point not so with a boat out to sea.

Yes, as I stated at the outset - such a thing exists but is very pricey. A simple $15 isolation relay works well enough and is much simpler and cheaper. True that an automotive alternator cannot properly charge a deep cycle battery -but what it CAN do is good enough for most uses. When you use a rectifier isolator or a relay isolator - the fact remains that the deep cycle battery will only get 95% charged. Not a huge issue. When not traveling or camping - just plug it into a small charger designed for it. I only posted the battery-to-battery charger to illustrate its existence. I'd never bother with in any of my RVs. I've got RV batteries near 10 years old so obviously my camping trips using the alternator to charge them on the road hasn't hurt anything. I am NOT a fan of rectifier-base isolators either. There is always a voltage drop across them. You get NO drop with a relay.

[Maineah]

Yes, as I stated at the outset - such a thing exists but is very pricey. A simple $15 isolation relay works well enough and is much simpler and cheaper. True that an automotive alternator cannot properly charge a deep cycle battery -but what it CAN do is good enough for most uses. When you use a rectifier isolator or a relay isolator - the fact remains that the deep cycle battery will only get 95% charged. Not a huge issue. When not traveling or camping - just plug it into a small charger designed for it. I only posted the battery-to-battery charger to illustrate its existence. I'd never bother with in any of my RVs. I've got RV batteries near 10 years old so obviously my camping trips using the alternator to charge them on the road hasn't hurt anything. I am NOT a fan of rectifier-base isolators either. There is always a voltage drop across them. You get NO drop with a relay.

I too am not a fan of diode based isolators they require a rewire are more complex do not all ways fail safe (dead truck battery) and require a .7 volt break over voltage just to make them conduct it's not for nothing they have cooling fins. In most cases the bone stock system will take care of all your needs most people do not camp away from power for very long any way. It is better to use a few power saving tricks then to add a lot of parts.

[zero]

I too am not a fan of diode based isolators they require a rewire are more complex do not all ways fail safe (dead truck battery) and require a .7 volt break over voltage just to make them conduct it's not for nothing they have cooling fins. In most cases the bone stock system will take care of all your needs most people do not camp away from power for very long any way. It is better to use a few power saving tricks then to add a lot of parts.

Nothing complicated or expensive about wiring in an isolation realy. I've got three self-powered RVs and two pickup trucks that I put slide-on campers on now and then. All five have isolation relays. Obviously the RVs are wired and ready to use. My pickup trucks have relays connected to the IGN circuit via a 5 amp fuse. When either truck is not carrying a camper, the fuse is pulled. When I do need to use a truck with a camper - I stick the fuse in, stick an RV battery in the camper - hook up the ground and power lead - and I'm all set. Drive anywhwere and my cranking batteries (two) and my RV batteries (one or two) all get charged just fine.

The only "complication" as I see it - is when you need high amps in back and it's a long distance from the alternator. In all my rigs the distance is 14 to 17 feet and I want at least 50 amps available from the alternator to the RV batteries. A 17 foot run at 50 amps needs #2 AWG copper wire and 60 amp fuses on each end. So, $3 per foot for #2 copper which comes to $51, $15 for a relay, a $5 on-off cut-out switch and $25 for a good pair of 60 amp fuses or breakers. Not a huge expense for a system that is simple and relatively trouble free. I've never had any trouble so in my case - 100% trouble free. First one I set up this way was 20 years ago and I'm still using it. No semi-conductors to fail or cause voltage drops. One moving part inside the relay but they last a very long time.

For somebody with a low-amp system - or only a short distance between the alternator and RV battery, it is very easy and cheap to do.

The main reason why I want high amps available is so the alternator can serve as my AC generator (in a way). Sending 50 amps back to my RV batteries supplements the reserve battery power and enables a 2000 or 3000 watt inverter to work very well - for making AC power for high amp appliances. Actual charge time of the RV batteries is not important to me since all our camping is "stop and go." We camp at night and drive during the day. We rarely just sit and camp in one place for a long time.

[Maineah]

The relay type isolators are as simple as it gets it is nothing more then an electric on/off switch. The diode type requires you to cut the alternator output wire add an output wire add a exciter wire find a place as close to the alternator as possible add two more connections for the batteries and fuse the whole lot. My 120 volt needs are about nil I use propane for cooking, cooling, and heating my water every light is an LED and my exhaust fan draws about 2 amps and I have an accumulator on the water system. I have gone 7 days with two 80 batteries (160 total) with a full battery charge. Most people drive during the day and that alone gives you more alternator output for coach batteries adding a larger gauge wire may well be enough with out having to replace the alternator to gain your charging needs. I will say my trips are not short so I have plenty of time to charge the batteries. My whole drill at this point is to avoid using a generator and I see a portable 100 watt solar panel in the future.

[Maineah]

Here is the system I built for mine using a combiner. The system is in the coach in a cabinet the battery wiring runs are the same loss no matter if it's in the front or the rear but it does however get every thing out of the weather it is fused at the truck end at 40 amps. The breakers are manual reset I want to know why it tripped instead of having it reset just to do it all over again. I like the combiner for many reason over just a dumb relay it ensures the truck battery is fully charged before allowing the coach battery to charge for one. The other little board is a timer the combiner has a by pass that can be activated to assist the truck battery should it be low I used a timer to make it automatic reset.

[MontereyDave]

Take a picture of where the battery is for us

There's going to be one ground, one connection to the front battery and isolator, one connection to the 12 volt system and one connection to the charger.

The isolator is under the hood. Cyclyinder with three prongs somewhere on the firewall.

All of them came with this but its possible to remove.

HUGE THANKSgiving wish to you all for sharing your expertise!!! Your pics were helpful; here are some pics below of what I'm dealing with. My goal is to have enough electical charge in the coach battery to be able to watch a small flat screen TV for a few hours. The most alarming discovery is the blue wire with a fuse going into the coach battery because it is frayed and brittle and looks like it's about to break free from its connection at the battery. Inside the coach battery box there is also a white wire hanging down from above that has been cut and is not connected to anything.

If you guys happen to see an easy fix I can handle, that's great. Otherwise if the solution is more complicated, then I will print this thread and carry it to an experienced professional at a battery specialist store or an RV shop where I'm sure your advice will be VERY helpful.

[waiter]

Shouldn't be any problem running t5he TV. You need to get a Voltmeter and learn to take some basic measurements.

You may be onto the problem, but without knowing exactly where wires come from (i.e. that white wire thats hanging down), it would be very dangerous to guess.

Clean up splices, replace burnt wires, trace that white wire and see where it connects to.

John Mc

88 Dolphin 4 Auto

[zero]

My goal is to have enough electical charge in the coach battery to be able to watch a small flat screen TV for a few hours. The most alarming discovery is the blue wire with a fuse going into the coach battery because it is frayed and brittle and looks like it's about to break free from its connection at the battery. Inside the coach battery box there is also a white wire hanging down from above that has been cut and is not connected to anything.

I could tell you more if you traced out some of the wiring and drew a diagram of where you think things are going. Winnebago often used isolation relays to charge coach batteries. The pictures you posted seem to show an isolation relay on your firewall. In your photos, white wire "C" is the energizer wire. That should have 12 volts positive whenever the ignition key is "on." When energized, it connects the two big terminals A and B (with dark wires). When the igntion key is "off" one of those black wires should read 12 volts positive and one should read nothing. When the key is "on" both should read 12 volts positive. One will go to the coach battery and one will go to the alternator charging source (might be tapped from the cranking battery).

This I assume is a 20 or 30 amp circuit breaker and one end is hooked to either A or B on that relay.

Here is a generic isolation relay wire diagram that Dolphin and Winnebago use in many Toyotas.

In regard to a TV and power usage. A 19" LCD TV only uses around 48 watts. A 19" LCD TV with a built in DVD player only uses around 65 watts. Even a small portable power pack like Duracell sells will run a 19" TV and DVD combo easily for three hours. A full size RV battery will do so MUCH longer. A typical 115 amp-hour RV batttery can run a 19" TV and DVD combo for 19 hours before it's stone dead. Can run the same for 9 hours safely (50% discharge).

My point being that a TV is not a big power user. You could buy (as a back-up) a Duracell Power Pack 600 for $175 if you shop around. Only weighs 31 lbs. It has a built in battery, 600 watt AC inverter, 12 volt power supply, light, radio, jumper cables, USB charge port, etc. You could charge it at home on AC. Stick it in the back of your motorhome and watch a 3 hour movie with a standard AC 19" LCD TV and DVD plugge into it. Then when done, take the power pack up front and recharge off your cigarette lighter or 12 volt power port. This of course is not a fix, but IS a great alternative.

If you get around to trying to check your isolation relay - keep in mind it is the "self grounding" type. That means the metal case gets the negative power from the battery by contact with the metal on the firewall - i.e. no ground wire. Some model relays are not "self grounding" and require a separate ground lead to operate. I mention that because even if the white wire is getting power - the relay still will not work unless it is making good contact with the metal it is bolted to.

[Maineah]

The relay should close with a pretty good "clunk" just turn the key on no need to start it. That does not necessarily mean it's good but at least you'll know it's powered up. If it proves to be ok remove all the connections and clean them up.Your rear battery wiring is shaky the one with all the splices yes John sure is right that's got to go. It most likely goes to the fuse panel ground (green) it goes green to red to white to green again use a #8 wire. The wire with the fuse in it is an after thought some thing some one has added see if you can find out where it goes and if there is nothing on the other end remove it. The black wire appears to go to a series of circuit breakers that are jumpered together with 12 volt+ wiring going else where looks like stock coach wiring. Old wiring is a pain so many people over the years may have tinkered with it. The front wiring looks OK just rusty. You should have no problem powering up your TV with a 150 watt inverter or maybe as suggested a jumper pack, by chance is there a lighter socket near by? perhaps an inverter with a lighter plug. After you get that all done then it's time to think about a retrofitted modern converter/charger! Remember you are restoring and classic antique!

[MontereyDave]

Thanks again, guys. I appreciate the great advice.

[5Toyota]

if that is a dolphin mine has two fuses off the rv battery one serves the tank panel the other i would have to look up the org wiring diagrams that i have from national rv show this and a wire from the circuit breaker too rv batt hot. the ground shows and has two white wires on battery ground

[Vanman]

All the ones I have seen on the Toys I have looked at have the isolator mounted cap end up, but what jdemaris and Maineha show are different. This is the PDF I got from Tekonsha, when I called the 800 # for more info she said that's the data for that relay. What gives ???

TEKONSHA Battery Switch .pdf

[zero]

All the ones I have seen on the Toys I have looked at have the isolator mounted cap end up, but what jdemaris and Maineha show are different. This is the PDF I got from Tekonsha, when I called the 800 # for more info she said that's the data for that relay. What gives ???

The relay doesn't care which way it faces gravity. The issue is the small water drain hole. Not all relays have the hole in the same place and some have none at all. If it has a drain - it needs to be on the bottom. If the drain is on top it will just gather moisture instead of letting it out.