It will at least rule out the chance of them being the cause of a problem.

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84 300D, 82 Volvo 244Gl Diesel

Battery isolators, bad.

They do fail open, but even when they're working, they reduce the charge voltage through them by 1.2v, which makes for a short-lived battery.

Better to replace it with a heavy-duty continuous-duty relay or battery combiner (www.xantrex.com look for Pathmaker) which has no diode losses, it's what I install on boats and RVs.

__________________

Gone to the dark side

- Jeff

Well I got it figured out . . .

I 1st hooked up the battery cable direct to the alt, bypassing the isolator, no difference . . .

Next I switched the Positive cable from one terminal to another positive terminal (there are two labeled) no difference.

Next I hooked a jumper cable from the positive terminal which is fed from the battery isolator, which is keyed on by the ignition switch . . . I then got 14.50 volts!

So I made up a little jumper wire, and now it seems to work . . . I took it for a 17 mile ride . . . it did go up in voltage but not much, around 12.10v, and dropped to about 11.96v at idle on the gauge in the dash. . . even though when I got back the alt was only putting out 14.36v??? But it did not register at the battery, could take awhile to charge the battery . . . although the aux battery voltage while running went up from 12.56v to 13.87v!

Another strange thing I noticed was after I got it going, but before I took it on the test ride, I probed the left positive stud (where I have jumped the wire to the ICM) and it had 14.65v . . . do you think I should put the positive wire over onto that post?

Here are some pics

Can you believe that they sold me a alt with a screw broken off?


This is how I had it hooked up yesterday . . .


Hooked up like this now . . .


Jeff, I'll look into the relay / combiner for it . . . thanx for the heads up!

Batteries are all series 31 925 CCA replaced in Nov 06

Edit to add: The "ICM" could also be "IGN" for ignition . . . now that I see the picture blown up . . . also, in my defense . . . I looked at it after it was installed and not much room to stick my head in . . . cameras are great!

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82 240D Manual 277K and still rolling!
02 Volvo S60 AWD For Sale

Jeff, is this what you meant? (Pathmaker is kinda $$$)



Or this?


Found it here: http://www.texasindustrialelectric.com/relays.asp

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82 240D Manual 277K and still rolling!
02 Volvo S60 AWD For Sale

Yes, pathmaker is $$, but it is a voltage-based connect/disconnect that will not leave a boat "dead in the water".

The relays you have pictured are what I've used in coaches for a "cheap" version. Hook the main/starting batteries up directly to the alternator, then the wheelchair-lift or auxiliary batteries up through the relay. Energize the relay's coil with ignition-switched power, so that the wheelchair lift can only draw power from the main system (batteries and alternator) when the ignition is on, even better is to use an oil-pressure switch to turn on the relay so the engine has to be RUNNING. I can send you an oil pressure switch for this, or if the bus has an oil-pressure triggered hourmeter, hook the relay up there.

__________________

Gone to the dark side

- Jeff

We are hoping to go cheap . . .

Which of the above relays would work better?

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82 240D Manual 277K and still rolling!
02 Volvo S60 AWD For Sale

I picked up a relay similar to your top one on Ebay for about $25 to do what you are doing on my Fuso truck/camper battery. I wired it thru the cigarette lighter which was only hot when the ignition was on. I like the idea of a oil pressure switch better.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I like the look of the package on the top one Shawn, but don't know if there's any difference other than that and a little current capacity.

__________________

Gone to the dark side

- Jeff

OK, this morning our driver went out on his route, started out at 11.5v . . . (was left at 12.06v on Sat) I told the driver that it would go up as he drove . . . about 30 mi late bus died, no juice!

I went and picked up his students and added them to mine, I was only about 15 min later than normal!

I pulled 2 working batteries from our spare bus, and went up and swapped them out, disconected the isolator and hooked all the batteries to the alternator, now it is putting 14 volts across the battery and dash mounted gauge.

So . . . does this make sense? (as this is what I told my Administrator!) that the isolator was not allowing full voltage to the bus batteries, but it went to the aux (lift) battery, (they were reading 13.87v while running) which caused the alt to be over worked (running all the time) and it eventually failed. When I took it off it turned hard, not really grinding, but with like 10 times the resistance of the new one!

When I checked the old alt, I was only getting battery voltage at the alt . . . so with it running the isolator was "turned on" and allowing a reading at the alt, after I shut off the ignition the voltage would slowly over 45 sec decrease to zero at the alt. The Isolator was VERY hot after my 17 mi run on Saturday! I also noticed that the alt terminal on the isolator was "loose" as in the stud was not firmly seated in the housing . . .

__________________
82 240D Manual 277K and still rolling!
02 Volvo S60 AWD For Sale

13.87 seems like normal voltage to me so I don't see how the alternator was being overworked.
It does sound like there was a problem with the isolator. Do the batteries really need to be isolated? I doubt there'd be many occasions where you'd use the lift without the bus running, thereby discharging the starting batteries. I'd likely just leave the isolator out of the system.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

The 13.87v was only on the Aux battery side of the isolator, the Bus batteries side of the isolator was only showing battery voltage of 12.06v with the engine running.

According to law when the driver is out of the drivers seat (except while doing a pretrip inspection) the keys must be removed from the ignition, so in order to operate the lift the engine must be shut off.

Imagine a special ed bus picking up it's last student, and the bus is running . . . driver is loading "Little Suzie" on the lift, and "Little Joey" decided he wants to be a bus driver today, and drives off with the driver on the ground, and "Little Suzie" half way up the lift!

But the question is do they really need to be seperated? Well there probably is enough juice in the three batteries combined they have 2850CCA (provinding you can just add the 3 - 950CCA each) Will the lift draw them down that much? Probably not. Since we at this time have no wheelchair students it is not a big deal, but we need to be compliant, or able to pick up a wheelchair student if they should inroll in our district. Better safe than sorry. . .

With the relay though it seems that in our scenerio (sp?) that if we had the lift battery seperate from the bus batteries, and we used the lift, then went to start the bus, as soon as we turned on the ignition (if that is what I used to activate the relay) wouldn't the bus batteries be getting drained of at least some power while we needed it the most to start the bus? Would there be a over all gain of seperating the batteries while discharging one, but then hooking them together to start the bus?

Lets say that if the lift took out (used) 250 amps (I'm just making up those numbers) and the Aux battery has 950 CCA, it is now only good for 700CCA left, right? (before being re-charged) Is it now going to try to get some of those amps from the bus batteries once the relay is activated?

I think this could be illiminated by using a oil presure switch like mentioned before . . . providing it supplies 12v.

__________________
82 240D Manual 277K and still rolling!
02 Volvo S60 AWD For Sale

With 13.87 volts on the aux battery side of the isolator, and 12.06 on the bus side , it sounds like something is not wired correctly, it sounds like the bus electrical load is running off the bus batteries, but the alternator is charging the aux batteries.

To me, the 13.86 volts indicates the alternator is charging, its output is just being sent to the wrong batteries, meaning you are draining the bus batteries while charging the aux batteries.

Can you eliminate the aux batteries and isolator for troubleshooting purposes and run only the bus batteries and the alternator connected?

You are correct, the starting battery would start to charge the aux. battery when connected, but it wouldn't take a high-current transfer/charge, probably only around 20amps at 12.4vdc resting voltage of the bus battery (source). Not enough to matter.

The relay will do the job, you need to ground one side of the coil, the other side can be either: ignition switched +12v or ignition switched +12v after passing through above mentioned oil pressure switch.

It sounds like the isolator went bad, then the bus battery, after enough dead-battery cycles the battery is unrecoverable. The alternator losing a bearing might be just a coincidence, send it out for a rebuild and you have a good spare.

It is possible that the driver could have started the bus by jumping across the isolator from the aux battery to the starting battery, if the aux battery was charging properly.

Temporarily bolt all 3 (alt, starting batt, and aux batt) cables to a good terminal on the isolator to tie them together, they will charge together and run the lift together, should be fine for one lift per start. If you're driving short distances between starts, better to get the relay or a new isolator first.

__________________

Gone to the dark side

- Jeff

This is what I did, ussually he drives for 1.5 hours . . . as right now at this very moment we do not have any students in wheelchairs

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82 240D Manual 277K and still rolling!
02 Volvo S60 AWD For Sale

Perfect. Let us know if there are further problems.

You should now see ~13.5v - 14v at each battery with the engine running at high-idle.

__________________

Gone to the dark side

- Jeff