I'm considering getting rid of my battery isolator and using my boost solenoid to charge my coach batteries when I'm driving. I already use my boost solenoid to charge my cranking battery when I'm plugged in. The only time I'd want the boost solenoid open is when I'm boondocking. I think the entire system would be simpler and more efficient without the isolator. I'll talk to Foretravel before I do this. I already spoke to Leece Neville and they thought it would work better without the isolator. Has anyone on here done that? How did it work out?
Scott
I would not do that. You might be stuck one day. I put in a patch relay charger and never worry any longer and I added extra cable to tie the batteries to the starter directly. Charges fine on the alternator thru the Isolator.
I would keep your starting batteries separate. The reason for combing them is to give a boost when the starting batteries are low. It is not good practise to charge two battery banks simultaneously if they are of different types. Also if your house batteries are discharged the alternator will be running at capacity for a long pierod. Not good for it.
Keith
The Cole-Hersee 24213 is a continuous duty solenoid (non-latching). The control circuit requires .7 amps all the time it is on and gets pretty warm in less than an hour just sitting there. The above posts make a pretty good case for not leaving it on to charge both sets of batteries.
A .7 amp draw will also flatten the batteries that supply the control circuit in short time it if they are not being charged.
Pierce
My old 1988 Winnebago used the boost switch solenoid instead of a diode isolator. The switch had three positions, isolated, connected when the engine is running, and (momentary) boost. It worked very well for the twenty+ years I opened the rig.
Thanks Tom, I know you understood my question, as did the guy at Leece Neville. I use the boost solenoid constantly whenever I'm plugged in so I can keep the cranking battery charged. It doesn't matter if it draws .7 amp because I'll open the solenoid when I'm boondocking of course. This means the cranking battery will be separate from the coach batteries. The coach batteries are exactly the same as a cranking battery. I always OPEN the boost solenoid before cranking the engine, because it's not capable of handling 1000+ amps that the 2 stroke Detroit Diesel would require for a cold start with straight 40 weight motor oil. I only close the boost solenoid for charging, never for cranking the Detroit. Once or twice I closed the boost solenoid to crank the genset in very cold weather when I needed all three batteries to heat it up and crank it at the same time, but that's very rare and hopefully will never happen again. There's only one alternator so it has to charge both sets of batteries anyway, whether it's charging through the isolator or the boost solenoid. The isolator creates a confusing alternator wiring arrangement that shouldn't be needed if I remember to use the boost solenoid to charge the batteries, which I will. The isolator is basically diodes and it tends to lower the voltage slightly due to some resistance, which creates some heat and reduces battery efficiency, this is according to Leece Neville, but I already suspected this was the case based on my experience as a data center engineer. We had rectifiers and inverters everywhere and we were lucky to get 80% efficiency out of some of them. The rest of the energy was wasted as heat that we had to remove with the air conditioning. Anyway, thanks for the replies. I'll check with Foretravel to see if they have any issues before I remove the isolator.
...also I suspect Leece Neville will tell me to change to a different voltage regulator. They seem to have a different voltage regulator for every type of application. I'll call them again before I remove the isolator to see which regulator I need.
Scott: Your use of the boost solenoid to isolate the batteries is perfect, and by doing what you are doing, you can take out the diode isolator. You understand exactly how 2 sets of batteries interact with the coach and how to keep everything straight. Very impressive.
The diode isolator is for the average RV owner, who doesn't fully understand the RV 2 battery setup (and doesn't want to), but just wants to use the RV without worrying about accidently wearing down the all the batteries and then be unable start the coach or the genny in the morning. This happened to my son, before I straightened out what someone did when a replacement alternator was installed. Alot of techs who consider themselves "alternator experts" can really mess up a RV 2 battery isolator system. This guy installed a jumper wire across the isolator, directly connecting the chassis battery to the alternator. The coach ran fine, but this removed the diode isolation, and all batteries discharged together.
I understand exactly how the system works after owning a few Foretravels and some boats and selling thousands of batteries and alternators in the years I was in the auto parts business. I can't imagine wanting to do without the convenience of the system the way it is set up from the factory. Kind of like the fridge issue or the gas vs diesel issue I guess. No right answer for everyone. There are things that drain the house batteries going down the road and we always arrive with the batteries topped off. I'm not smarter than the isolator or the Allison. Just one opinion.
My Dad had a saying "To each his own" and this certainly applies to RV owners.
I also embrace the battery isolator, in fact when I upgraded the alternator to the Delco 28si I also replaced the stock 160 amp isolator with a Surepower 240 amp unit. The 28si alternator has a remote sense option which compensates for the diode voltage drop that Scott mentions. In my case, when my sons use the coach, let's just say, without the standard isolator, I would be getting a phone call...
How's that 28si Delco alternator working out? Can you comment on build quality vs the Prestolite?
Personally, I stick with the Prestolite / Leece-Neville because I am only 35 miles from factory tech support.
How is this for an alternative solution? On our Detroit, none of the V belt grooves on the crank pulley are used and there is a big flat plate directly above with threaded holes ready to mount most anything. So, get rid of the isolator, add a single wire alternator for the engine batteries alone above with a short V belt down to the crank pulley. Start batteries are only a couple of feet away. A garden variety Bosch alternator would be a good candidate as you don't even have to loosen the belt to replace the whole brush assembly, just a flat screwdriver to take two screws off. Could leave the boost solenoid in place in case of main alternator failure and then the 10Kw generator would not have to be used to keep the house batteries charged while driving or vice versa.
Pierce
Yup. The only additional convenience I added was a Trik-L-Start to keep the starting Optimas topped off while parked and plugged in. Less than $50 for a lot of piece of mind. I think they were standard on some Winnebagos. Ultra Trik-L-Start 5 Amp Starting Battery Charger/Maintainer (http://www.rvupgradestore.com/Ultra-Trik-L-Start-p/tls-oem.htm)
It must be working rather well, in that my Optimas are now 11 years old and still start the ISL without ever using the boost switch.
wonder how I would get from my positive battery terminal in the front left compartment to the right rear engine start batteries positive terminal? i have a 130 watt solar panel wired into the refer also?
bob
Pierce, Good idea but Scott (and myself) have a rear radiator. That spot is already taken by the fan.
The Trik-L-Start is usually wired across the diode isolator.
I have a battery tender instead, plugged into the engine block heater outlet under the bed and wired to the starting batteries a couple of feet away. I too find my starting batteries are always up to the task, be they 10 years old now.
I did it about 4 years ago and everything works fine. It gives you more control but now you have the responsibility to manage the switch at the appropriate times. I, of course, turned down the voltage on the alternator as it now only directly feeds the chassis batteries.
Here's the reasons I went this route:
1. I made all 3 batteries (in front of rear drivers wheel) house batteries - put in AGM's and got rid of the box. I added 2 pickup size batteries (more CCA than an 8D) behind the passenger side rear wheels for the chassis. With a bigger house bank (50% larger) the potential of overloading the alternator goes up.
2. I added a side radiator with a bank of electric fans that pulls 75 amps when they run. This only happens when going up a grade in the summer - which is also the least desirable time to put that load on the alternator. I wired the fans to the house battery and turn the boost switch off when the fans run. Coming down the hill, after the engine is cooler, the boost goes back on to recharge.
3. Most of my trips are weekend boondocking. We all know that with the isolator it's a must to run the generator if your batteries are down so you don't burn up the alternator. Now I can leave camp with by batteries run down and not have to run the generator. I start the engine with the boost on - then shut it off. I see no value in returning home (or FH campground) with my batteries full when the first thing I'm going to do is plug in.
Observation: The convenience of a isolator is only fully realized when the alternator is large enough to handle a discharged house bank. Having to consider whether or not you need to run the generator before you leave is not convenient. An even better option to a larger alternator would be to just have a thermal protection device built into it - seems to be commonplace on many other electrical devices. Why not alternators? Maybe they are out there?
Mine is mounted under the bed, right next to the isolator. Like it says, easy 3-wire connection. One on each side of the isolator and one to ground. Then "forgetaboutit".
Since relays seem to be my favorite subject this week, this sounds like a job for one. When you turn on (manually or by temperature) your new fans, you could energize a Normally-closed relay to turn OFF the boost switch. It would automatinally return to ON once your fans were turned off and the power removed from the relay coil. Minimal current draw to hold the relay open.
I did a lot of research on alternators and went with the 28si, it is a direct replacement for the Leece Neville. If you search the internet there is a wealth of information, and several sources. From what I read, the 28si has superior cooling over the Leece Neville external fan design, and it has the remote sense feature. The remote sense terminal will compensate for the voltage drop of the alternator wiring to the isolator and the isolator diodes. My dash voltmeter reads about 1 volt higher after installing this alternator.
I went with the DB Electrical 180 amp version and have been very satisfied. I don't have a lot of miles on it so far, but the performance is impressive. At idle I have measured 100+ amps output.
http://www.dbelectrical.com/p-7840-100-new-aftermarket-alternator-to-replace-delco-28si-8600307.aspx (http://www.dbelectrical.com/p-7840-100-new-aftermarket-alternator-to-replace-delco-28si-8600307.aspx)
I would recommend upgrading the isolator to one that has the ignition excite post. The 28si needs external excite to function. Here is the isolator I used:
Sure Power 24023aIB Battery Isolator (http://www.ase-supply.com/Sure_Power_24023aIB_Battery_Isolator_p/sp-24023a-ib.htm)
I have had the Delco 160 amp 28SI on my U295 for 1 1/2 years with no problems. It was a direct replacement for the Leece Neville. I found the Leece was full of the film covering from the sound insulation in the engine bay.Gam
Duh. The three posts on the isolater are both battery positives and a ground aren't they?
Is that correct?
Middle terminal will be where alternator output is connected. One side on isolater will be positive to house batteries. Other side will be positive to chassis batteries. Grounding is normally through the metal frame of the vehicle.
Looking at the isolator, left post is coach batt, right is engine batt, center is alternator. Some have a ground post. See photo and schematic.
Pierce
As it happens I did this yesterday... unhooked the idolater and wired in an Andina ACR. (basically a voltage sensing relay) I left all the stock components in place, moved the alternator cable to the chassis battery post on the isolator and put the ACR across the two battery terminals. Simple, works well and reversible in about 3 minutes with a crescent wrench.
This Foretravel article should give a good explanation how our alternators differ from big rig alternators and why they are sometimes miswired :
"Foretravel Alternator Foretravel Motorcoaches use a Leece-Neville brand alternator that is externally excited. These alternators are not the same as what the big semi rigs use that run up and down the nation's highways. This is commonly confused in truck repair shops. Foretravel motorcoaches and a lot of other brands use what is known in the industry as a battery isolator, this allows the alternator to maintain two battery banks at a set voltage. You also have to excite the alternator externally. Meaning that when the engine is not running there is no voltage present on the large positive outpost terminal. The alternator has two large terminals one positive and one negative on the back side of it along with two small terminals. The two small terminals tell the voltage regulator what to do. One terminal is labeled DUVAC and the second is labeled IGN. The DUVAC terminal is what monitors the output voltage, the sense wire is located on the engine battery side of the isolator (2000 year model FT's and later models, earlier models sensed from the remote start panel). The ignition terminal is what tells the alternator to start charging. The ignition circuit is powered up when the key is turned on. When checking voltage directly at the alternator it will read higher than what is at the batteries, this has to happen due to voltage drop through the isolator and wiring to the batteries. Example; when reading output voltage at the alternator with fully charged batteries your readings could be 15 volts dc (+/-) thus allowing for a normal 1volt dc drop in voltage through the isolator, this in turn will allow for a maximum voltage at the batteries to be 14.1 vdc (batteries). The only way ignition terminal voltage will affect charge output voltage would be if no voltage present, it takes minimal voltage to start the alternator charging (7-7.5 vdc). Foretravel Motorcoach technical.assistance@foretravel.com"
A side note: Be careful when you replace these two smaller terminals. If you mix them up, the alternator just cranks away, feeding the batteries at high level. They'll get toasty, really quickly. I know.