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Mark Trask
08-20-2015, 05:55 PM
Hi Members,

Do any of you have a dual battery set up in your coach or ambulance? I have a second battery well and any issues that I have had with my 1965 Superior have been electrical in nature. I am thinking of installing a 2nd battery in parallel. Thoughts or suggestions? The generator should charge both, right?
I would love to hear from you.


Mark Trask

Philip Scanio
08-20-2015, 07:43 PM
Mark,
Our last limousine (1999 Lincoln LCW 65 5 door) was built with two batteries. It had a switch on the dash that you could push to use the secondary battery if primary would not start the car. The secondary was a 12 volt motorcycle battery. The only problem we had is that if the secondary was dead it would draw down the primary. The Lincoln dealer could not find the problem but I took it back to LCW and they had the problem solved in 15 minutes.The car had the heavy duty livery package alternator so charging was not a problem, In 1969 I worked at a funeral home that had a 1968 Olds Vista Cruiser ambulance. We had a problem with the engine dying when we engaged the Federal siren with the lightbar operating. I remember that they installed a second battery and we no longer had that problem.

Todd Merrifield
08-20-2015, 07:47 PM
If you're having problems, a second battery in parallel won't necessarily solve the problem. You want an isolator or dual battery switch if you run two batteries. Two batteries in parallel will just be drained like one would, it might just take a little longer.

An isolator allows one alternator to charge two batteries while the engine is running, but it keeps them separate from each other. This is typically done to keep things like scene lights and rotating beacons from draining the starting battery when they are left on at a scene without the engine running. The starter and other critical circuits that are used when driving a vehicle are wired to one battery, while the lights, radios, and other things are wired to a second battery, sometimes a deep-cycle battery that can be run down to nothing and recharged.

The isolator will typically handle all this with no additional input from the driver, it will either be a huge diode or pair of diodes with a big heat sink, or more elaborate ones will monitor the voltage and condition of both batteries and charge them as needed.

A more period correct option for older ambulances is a battery switch. It is usually a three position switch that allows the alternator/generator to charge one or both batteries when the engine is running. It is similar to an isolator, but requires the operator to decide what battery or batteries need to be charged and set the switch accordingly.

John ED Renstrom
08-20-2015, 10:44 PM
most all the ambulances used the duel battery set up. vary few if any combos or Hearses did. what issues are you having?

Mark Trask
08-21-2015, 11:35 AM
Thanks Gentleman,

I always know that I can come to you for a wealth of information. I appreciate the responses. As Phillip mentioned, I am having the same issue of the engine dying when I run the Federal siren.

I secured what I believe to be a period correct Cole Hersee Battery switch.
I offers 4 positions: Battery 1, Battery 2, Both and Off. It is larger than I expected and may have been for marine use. I would like to use it in the 65.

Thanks for the information on the isolator Todd, this sounds like a good option.
If I understand you correctly, you would use the isolator in lieu of the switch.
Not both, right?

The car has a new battery and a new generator, but does not seem able to hold a charge for a long period of time. There appears to be a constant drain on the batter. I will need to isolate that issue before adding the additional battery and switch.

Thanks again you guys.

John ED Renstrom
08-21-2015, 11:53 AM
as with most electrical problems,it would be best to find the drain before adding more power. the Q is a power hog on start up they really pull a lot of amps. with that running, size does matter. you will want a large capacity battery. as it seams everything now days they are as marginal as they can get. as you did not mention the brand of your car it would be a yes or know on the rotation switch. they were a big one. most of the MM used the electric solenoid with only a rocker inside. Superior's loved that big knob. with the problem your experiencing the isolator would not help. but with it you could be sure that you had a fully charged battery on stand by

Todd Merrifield
08-21-2015, 12:23 PM
Thanks Gentleman,

Thanks for the information on the isolator Todd, this sounds like a good option.
If I understand you correctly, you would use the isolator in lieu of the switch.
Not both, right?



Yes, one or the other, they do the same thing. One is automatic and one is manual. The Cole-Hersee was designed for boats, but it was what they used back in the day. The isolator is a smaller and more elegant solution, but probably not period correct.

There is a slight difference between the two methods. The manual switch like you secured is also designed to put one battery in place of another, as if you were physically swapping in a new battery. Both batteries would be wired to everything, then you choose which one(s) you want to charge with the alternator via the switch. You could either wire it that way, or the same way you wire an isolator, like I described above. The isolator is not really designed to work that way, it is more for running two circuits and keeping them separate from each other, while still being able to charge both from one alternator/generator.

Peter Grave
08-21-2015, 02:55 PM
The Cole Hersee Battery switch is what most squads in this area used when these rigs were operated 30 years ago. They give you the ability as stated to use one or both batteries and to shut the system down when parked. As far as the draw (batteries going dead when parked) goes a quick check for a draw is with everything shut down pull a battery cable off retouch it to the battery if you get a spark chances are there is a draw. This can be checked more by putting a test light in series with the battery terminal if it lights there is a draw. You then begin disconnecting things till the light goes out the last thing disconnected is the problem. A note to all who have one of the Cole Hersee Battery switchs is NEVER shut the batteries off with the motor running you can fry the alternator in so doing.

Tim Prieur
08-21-2015, 06:57 PM
When driving the car is it best to run with both batteries in the on position, or just one? thanks

Peter Grave
08-21-2015, 07:56 PM
There are two therories on this #1 drive with both batteries in it keeps them both charged and gives maximum staying power for lights sirens etc. #2 drive with only one battery in switch between each daily. This way if something draws the on line battery down suddenly the second one will be available fully charged you just switch to #2. This is assuming you don't have different electrical items hooked to different batteries (Only one central power point). One final thing if you are going to jump another vehicle with your rig have both batteries in gives a bigger boost through cables.

John ED Renstrom
08-21-2015, 11:04 PM
the Ida in two batteries is twice as many amps. if you running a amp hog like a Q you need the amps. the manual switch or the pair of electric switches lets you select a battery or cut off all power to them. most still ran a trickle around for the clock. the isolator as described lets you charge a battery not in the cars system. such as a camper battery or the safety battery on your trailer brakes. one would still have to have a manual switch to use it in the start circuit. as for how to run them with a duel battery you will get as many stories as the the car gets drivers. I do know if the batteries are not equal one will take the full charge and boil it dry. me I always clicked both one and went about my business.

to me if you double anything you double your expense. I would sell that Q to some one that just thinks they need one and get a real siren that will run just fine off one battery

Todd Merrifield
08-21-2015, 11:28 PM
A well maintained vintage ambulance shouldn't NEED a dual battery system these days. It was a different story back when they were in use, running the siren for long periods of time, along with lights and whatever equipment that was on board that either ran off the battery or an inverter that ran off the battery/alternator. These days the biggest draw is running the siren for a couple seconds here or there, or letting the lights run. A second battery is nice to run your lights off of during a show, especially if they are a bunch of par-46 bulbs, but beyond that, the car should start and run just like any other vintage car does, on one battery. If it doesn't, something is wrong, and a second battery is just a band-aid on a bigger problem.

Mike Boyer
09-10-2015, 10:43 AM
On the Horton I removed the second battery and everything still works fine, all the lights, lightbar, siren everything .....like Todd said back in the day you needed the second battery . I have to have the truck running when I have everything on but how many times do you have everything on for a long time ? I installed a 1000 amp battery and I'm good to go.

no sense spending money you don't need to