Coach Battery Hook Up

[Maineah]

Can't vouch for the Sunrader because I have more important things to do than surf the web but the vast majority of MH's used the solenoid isolator because they are simple, effective and cheap they also required no rewiring of the charging system. Both are battery isolators the terminology is not important. If the Sunrader once had a solid state isolator it was butchered to the point that it is no longer useful. If the alternator wiring goes to the center terminal of what is left of the isolator it cannot charge the truck battery and most likely would not charge the coach battery either because there is no exciter wiring. Whoever wired the isolator was clueless as to how they work.

[zero]

Can't vouch for the Sunrader because I have more important things to do than surf the web but the vast majority of MH's used the solenoid isolator because they are simple, effective and cheap they also required no rewiring of the charging system. Both are battery isolators the terminology is not important. If the Sunrader once had a solid state isolator it was butchered to the point that it is no longer useful. If the alternator wiring goes to the center terminal of what is left of the isolator it cannot charge the truck battery and most likely would not charge the coach battery either because there is no exciter wiring. Whoever wired the isolator was clueless as to how they work.

You don't have to ''surf the Web" for a Sunrader diagram. I already posted it ON this thread.

I'm not sure about what "most" RVs have for battery separation. I have not seen most of them. I can say for sure that I have seen many that left the factory new with rectifier-based isolators and not relays. All the Toyota Chinooks came that way. So did my 1988 Minicruiser. So did many Sunraders. On the other hand many Dolphins and Winnies came with relays. Winnebago went one step further and used "smart" relays on many.

I personally prefer a relay. No voltage drop inherent. That beings said - if an RV came OEM with a rectifier-based isolator - it's simplest to replace with the same.

3 post version is usually marked A, 1 and 2. A is often in the middle. 4 poster is needed for certain alternators like Nippodensos with internal regs or Delco CS series. And there are two different versions of 4 posters (E or R post). Other alternators with internal regs eg. Delco SIs do fine with 3 posters.

If someone hooks up a 3 post isolator with no 4th exciter post - with a NippoDenso internally regulated alternator - it will indeed still charge. I've seen a few hooked up that way although I assume it causes problems with incorrect voltage sensing and both batteries would be undercharged by something like 7/10ths of a volt. I never hooked up the wrong isolator on purpose to test so I'm only guessing.

In regard to relays and getting the right ones? I know that my local NAPA stocks many intermittent-use relays and does not stock continuous-use relays. Same for Advance Auto. They can get a "full-time" relay overnight IF you can make the counter-person understand what one is. Not the sort of place I'd be looking for generic continuous-duty relays. Not unless I already knew the part #.

I posted the links to examples of isolators and relays because Linda mentioned it would be advantageous.

[Derek up North]

I don't want to go back and read all 4 pages of this thread, but it seems that the wiring has been modified so creatively that it's possible that the old 'coach' battery is now the only one hooked to anything and is powering both the coach and motor!

[zero]

Could be. One problem is that 30 amp circuit breaker and small gauge wire that cannot carry all the alternator output. If, in essence - the alternator is jumpered through that isolator and hooked only to the "house" battery - as soon as that alternator reaches half it's capacity - it would trip the breaker. If that breaker has NOT been tripping - then the alternator output wire is being routed to some location we are not seeing in the photo.

[Maineah]

NAPA relays take your choice http://www.napaonline.com/Catalog/CatalogItemDetail.aspx/Auxiliary-Battery-Relay/_/R-ECHST664_0311519544

http://www.napaonline.com/Catalog/CatalogItemDetail.aspx/Auxiliary-Battery-Relay/_/R-ECHAR158_0193339013

http://www.napaonline.com/Catalog/CatalogItemDetail.aspx/Auxiliary-Battery-Relay/_/R-ECHAR7027_0461647117

Internally regulated Nippondenso alternators are type 2 alternators they are not the only type 2 type 2's requiring an exciter wire on a solid state isolator with out it,it will not charge.

The alternator does not output 60 amps unless there is a demand for it the truck is capable of a 60 amp load the coach is not.

[Maineah]

I don't want to go back and read all 4 pages of this thread, but it seems that the wiring has been modified so creatively that it's possible that the old 'coach' battery is now the only one hooked to anything and is powering both the coach and motor!

If it is wired the way I think it is it can only receive a charge and can't go the other way but it could explain the dead truck battery. There is no doubt that it is wired incorrectly it needs two more wires and one more terminal to work.

[zero]

I never said NAPA does not sell the relays. I said the NAPA and Advance Auto stores in my areas (central NY and northern MI) do not stock them.

And yeah . . about the exciter post need for several makes of alternators and not just the Nippo. Thus my previous mention of the Delco CS needing it.

A typical "60 amp alternator" that came OEM on mid-80s Toyotas is capable of making near 80 amps for short periods of time. If there is such demand - anywhere - front battery or rear battery - the power will try to travel the wire. If too small, either it overheats, or a fuse/breaker blows or trips. Or a fusible link melts. Or an isolator fries. My coach batteries and accessories in the rear of my Minicruiser are certainly able to get 60 amps @ 14 volts from the alternator. That via the #2 AWG cable connecting the front to the back. This is why Toyota only uses an 80 amp fusible link in the alternator charge wire and no small fuses or breakers.

[Maineah]

Good for you using a #2 wire most people including myself don't need or want to go to the effort and expense when a #8 keeps their batteries charged as does the little charger at something around 3-6 amps. The NAPA store in Fryeburg serves about 3500 people in 3 towns they have at least one in stock if they don't they will have it the next day so yes you can buy them at NAPA no need to special order. Yep a Toyota alternator indeed is fused at 80 amps never seen one blown yet. So what did you use for your #2 wire? A 60 amp breaker? A # 8 and a 35 amp breaker is fine to charge the coach battery for normal loads and normal people throw in a 2000 watt inverter electric fridge a microwave and a few other heavy loads then you might need 60 amps. It's all about the money the RV market was and still is very competitive so if some thing works why "fix" it.

[kgibson4]

If this will help, here's a picture of the isolator in our '87 Odyssey. The wire from the alternator (black) is connected to post A. The coach battery is connected to post 1 through the breaker on the left. The truck battery is connected to post 2 through an after-market ammeter which most Toyhomes probably don't have.

Coach battery to Post 1

Alternator to Post A

Truck battery to Post 2

Nothing to Post E

This set up has worked great for us.

[zero]

If this will help, here's a picture of the isolator in our '87 Odyssey. The wire from the alternator (black) is connected to post A. The coach battery is connected to post 1 through the breaker on the left. The truck battery is connected to post 2 through an after-market ammeter which most Toyhomes probably don't have.

Coach battery to Post 1

Alternator to Post A

Truck battery to Post 2

Nothing to Post E

This set up has worked great for us.

I've seen several hooked up like that (with the NippoDenso internal reg alternators). Not supposed to be proper but seems to work well enough for many people.

Just a guess -but I assume it supposed to be taboo because of this. The OEM NippoDenso alternator decides the charge rate by sensing battery voltage at terminal A on that isolator. That voltage on terminal A will always be lower then what actually gets to both batteries (terminals 1 and 2) due to the inherent drop in the rectifiers. So the alternator cuts back charge rate too soon since it never gets to know what actual battery voltage is. Many other alternators have a separate battery voltage sensing lead that hooks directly to the battery and eliminates that problem. We're talking 7/10ths of a volt difference here. So it will work regardless but just not charge the batteries up as high as most alternators will do. Normally the batteries would be charged at 14.2 volts (approx.). So with the 3 post isolator like in the photo - they get charged at 13.5 volts instead. Not something that is easily noticed. Again . . just a somewhat educated guess. I never had to think very hard about it before. My 88 Minicruiser also came with just a 3 post isolator and worked well enough for the previous owner.

[kgibson4]

So with the 3 post isolator like in the photo - they get charged at 13.5 volts instead. Not something that is easily noticed. Again . . just a somewhat educated guess. I never had to think very hard about it before.

So just to verify, I put the multi-meter on it. With the stock alternator and this isolator it was charging at a rate of 14.24 volts. Good enough for me.

[zero]

So just to verify, I put the multi-meter on it. With the stock alternator and this isolator it was charging at a rate of 14.24 volts. Good enough for me.

14.2 volts at the alternator post or at a battery post? Like I said - I was, and still am guessing as to how it works out. All isolators have a voltage-drop between the input and the output. If the alternator senses battery voltage at the input - it will be fooled into thinking the battery voltage is higher then it really is.

[kgibson4]

14.2 volts at the alternator post or at a battery post? Like I said - I was, and still am guessing as to how it works out. All isolators have a voltage-drop between the input and the output. If the alternator senses battery voltage at the input - it will be fooled into thinking the battery voltage is higher then it really is.

At the battery post.

[zero]

At the battery post.

I believe it, and like I said before. I've seen several Toyota RVs that seem to work just fine with that setup. My question I guess is . . why? The companies that sell the 4 post isolators claim the extra "E" post is needed so the internally regulated Denso alternator works properly (when installed on Toyota RVs). Yet there are plenty around that appear to be wired with the 3 post units (A, #1, and #2 posts) and well. If your's reads 14.2 volts at the battery post - and the alternator is "sensing" at the "A" post of the isolator - that should mean the voltage at the "A" post is .7 of a volt higher, i.e. 14.9 volts. In theory , that is not supposed to happen since the regulator is set lower then that. I guess all that matters is it works. The rest can make a person's head hurt. By the way, I've got a voltmeter on my Toyota. It's not exactly rock-steady when it comes to voltage. It runs back and forth between 13.8 and 14.3 volts. That's fine with me. My Dodge Grand Caravan does exactly the same. Anything above 12.9 volts is going to maintain the batteries.

[kgibson4]

jdemaris,

Thanks for your input and expertise. I just hope that tofubiscuit can get her wiring restored to original and that it works as well as ours does.

[Maineah]

Not all Nipondennso required a 4 post the earlier ones did not it was some where in the early to mid 80's that the regulators were changed it's pretty much a given if it's a 22RE it will need it. If there is any doubt just buy the 4 post and don't use the "E" lug if it's not needed. Frankly I don't like the ideal of messing with the factory wiring if you don't have to or the ideal of losing charging voltage to make heat it's not for nothing the isolators have big fins on them. Typical break over voltage for a diode is about .7 volts that is where the heat comes from it is pure loss.

[kgibson4]

It's kind of hard to get a good picture with the coil in the way, sorry. Here's the best i could do without disassembling anything. I know, I know, just being lazy.

I suspect tofubiscuit's isolator has/had a similar label, but it would be on the side facing the firewall. Her's, of course, being a little different in that it is a 3-post and ours is a 4-post.

[Derek up North]

Nothing wrong with that picture. Thanks for taking the time to post another.

[tofubiscuit]

Ok, took a few days away to go to my paying job. Read through all the posts and decided to get the engine battery recharged and drive it back to my mechanic and have us go through the posts together and fix it. Toyota won't start. Here is what happened - exact same thing happened this morning with 2 different batteries (one of which I know is good, I had it tested yesterday): put the engine battery back in and hook it up. I go into the cab. The overhead cab light comes on. I get excited, thinking yeah, power. I put the key in the ignition. The door to the cab is open and the "you left your keys is the engine" sound is made. I start turning the key. All the dash lights come on. Turn the key all the way and nothing. Not even a click the the starter gears are engaging. I turn it off and re-turn the key to start it. Not even the dash lights come on the second time. The overhead cab light won't even come on. So when the battery is first hooked up there is power flowing, but as soon as I start turning the key it is no longer sending power. I thought maybe issue with the ignition switch, but would that short it out so even cab lights won't come on. Everything about the rv has run perfectly for the past few months. I even went away for a week and it ran fine. Been living in it in my driveway for the past month. Everything fine. Usually drive it to town once a week to let the engine run. Didn't drive it to town for the two weeks prior to battery going dead. Started the engine battery a few times during those two weeks but didn't drive it. So I am not even sure the two problems are related. Only found out about the weird hookup because I decided to open the fuse box in the coach to look at it and saw the note. Just threw this out there to see if there are any ideas. I'd rather drive it to the mechanic than have it towed if possible. Calling my mechanic later when I know someone is near the phone.

[zero]

Ok, took a few days away to go to my paying job. Read through all the posts and decided to get the engine battery recharged and drive it back to my mechanic and have us go through the posts together and fix it. Toyota won't start. Here is what happened - exact same thing happened this morning with 2 different batteries (one of which I know is good, I had it tested yesterday): put the engine battery back in and hook it up. I go into the cab. The overhead cab light comes on. I get excited, thinking yeah, power. I put the key in the ignition. The door to the cab is open and the "you left your keys is the engine" sound is made. I start turning the key. All the dash lights come on. Turn the key all the way and nothing. Not even a click the the starter gears are engaging. I turn it off and re-turn the key to start it. Not even the dash lights come on the second time. The overhead cab light won't even come on. So when the battery is first hooked up there is power flowing, but as soon as I start turning the key it is no longer sending power. I thought maybe issue with the ignition switch, but would that short it out so even cab lights won't come on. Everything about the rv has run perfectly for the past few months. I even went away for a week and it ran fine. Been living in it in my driveway for the past month. Everything fine. Usually drive it to town once a week to let the engine run. Didn't drive it to town for the two weeks prior to battery going dead. Started the engine battery a few times during those two weeks but didn't drive it. So I am not even sure the two problems are related. Only found out about the weird hookup because I decided to open the fuse box in the coach to look at it and saw the note. Just threw this out there to see if there are any ideas. I'd rather drive it to the mechanic than have it towed if possible. Calling my mechanic later when I know someone is near the phone.

Seems obvious you've got a bad connect in the battery feed. What you describe is a common problem in GMs from the 80s. Not sure about the Toyota without looking at mine. #1 you need to verify your battery connections are good including the posts and the ground wire to chassis connections. #2 if all that is OK, you need to follow the main positive battery cable and find out where it gets joined to the rest of the electrical system. On many GMs this happens on the big post on the starter motor. If that nut on the starter gets loose - you get the exact symptoms you've described. Not sure where the Toyota does it. I'll go out and look at mine later. One way to verify a bad connection is to just turn on your head-lights. If they first shine bright - but go dead when you try to crank the engine - you know.

[zero]

I just looked at my 1988 Toyota. Unlike a GM, Toyota has a separate positive power cable that runs from the battery post - to the fuse and relay box nearby on the fenderwell.

[zero]

IF you turn your headlights on and they first work, then go out when you try to crank the engine - you've either got a bad battery post connection or a bad ground to chassis connection. Here's the diagram showing how the starter and the headlights (and most else) are on two separate power feeds.

[kgibson4]

I agree this sounds like a poor connection somewhere. When changing a battery it's always a good idea to clean the insides of the cable terminals, where they mount to the battery posts, with a wire brush. The connections need to be reasonably tight, too.

Hope I'm not giving you info that is too basic, here.

[tofubiscuit]

Never worry about getting too basic with me! Headlights won't work at all. As soon as the battery is hooked up there is enough power for lights. But as soon as I start turning the key all power is lost and won't come back. It looks like it is about to stop raining, so I'm going to go out and start tracing the wires from battery to see if something is loose. Terminal are clean, and the battery is good. It seems like when I get electrical issues I get them in buckets! As soon as I get the truck starting again then I get to start working on the bizarre coach battery system. Good news is that I am really learning my way around under the hood.

[tofubiscuit]

Also, thanks for all the photos and diagrams everyone. I have discovered that I am definitely a visual learner, so the pictures mean a lot.

[Maineah]

Have a good look at you ground cable it is bolted to the body some where near the battery and then goes to the engine make sure they are clean an secure. I believe an 88 had a body fuse in the fuse box it is a large one much bigger than the others that will not come out if you pull on it I'm thinking it's an 80 amp and maybe a 100 either way that is where the power for the truck comes from they are bolted in make sure the bolts that are on the fuse are tight.

[zero]

I believe an 88 had a body fuse in the fuse box it is a large one much bigger than the others that will not come out if you pull on it I'm thinking it's an 80 amp and maybe a 100 either way that is where the power for the truck comes from they are bolted in make sure the bolts that are on the fuse are tight.

That large fuse is only for power to things other than the starter motor. Power to the starter-motor is direct from the battery with NO fuse in between. Thus if the truck refuses to crank - it's likely a negative battery post or a ground-to-chassis problem.

[Maineah]

The key switch kind of needs to have power to send to the starter from the body fuse some where he is losing a connection under load and it's not coming back.

[zero]

The key switch kind of needs to have power to send to the starter from the body fuse some where he is losing a connection under load and it's not coming back.

Could be. I haven't traced the starter-solenoid circuit. Power to the the starter itself is directly connected to the positive battery post; It sounds to me that he has enough power getting through a dirty/corroded connection to carry 10 -15 amps to the headlights. But as soon as the starter engages and pulls 200 amps - the shared connection overheats and craps out. Then all goes dead. Likely via a high-amp connector that both the starter itself (not the solenoid) and the rest of the system are both reliant on. That would be either a positive battery terminal, a negative battery terminal, or a negative wire-to-chassis ground connector.

Just guessing sitting here. If I was there I could easily diagnose it in 5 minutes with a carbon-pile portable load-tester. Just clamp on to suspect points in the circuits - crank up the amp draw - and see if voltage can be maintained.

[zero]

This is the sort of carbon-pile I use for load-testing circuits. It cuts out all the guess work. My AC Delco cost me over $150 when I bought it 30 years ago. Harbor Freight now sells knock-offs for $49.

[tofubiscuit]

Thanks all. Followed all the wiring from battery through engine and made sure all where secure and made sure all fuses were in solid. It did the trick as she started right up. Drove around town and had no problems. Going to go stay in a few state parks for a few days - found some with relatively cheap electrical hook-up, and a friend loaned me a portable Honda generator just in case. This is supposed to be my vacation time, trying to salvage what I can for my son. When get back in a few days will start tackling the messed up coach wiring. Until then I'll hook up to be safe.

[Maineah]

Great at least your safe for now. One thing I would like to add it's some thing that is often over looked. If the battery cable ends have been replaced (they will have two small bolts that clamp the heavy wires down) remove the clamp and clean the connections underneath they can act just like a dirty cable.