Help with Ambulance electrical system

[jhoyt]

I'm looking for some advice on my ambulance electrical system.

My system is set up almost exactly like the attached diagram from the KKK-1822 specs. The only differences are I don't have an inverter, but I do have a charger. Also, the module disconnect switch is actually a module power solenoid.

I have one battery under the hood, and another two in the battery compartment in the patient module. They are all ganged together to make one large power source, as in the diagram. I'd like to have a separate deep cycle battery bank to run a fridge, lights, usb ports and a water pump. Ideally I'd be able to break of the module batteries for this purpose, but I'm not sure if only having one battery for starting is a good idea for my 7.3 L Powerstoke.

So now I'm thinking of adding another battery bank for the deep cycle purposes. I was thinking of changing the module power solenoid to a BlueSea automatic charging relay, and wiring in the new batteries just after that. I'm not exactly sure which model of ACR to get.

Later I'll add solar and wire the charge controller after the ACR as well. The idea would be to run all the module stuff off the deep cycles and those batteries would charge along with the starting batteries off the alternator or shore power, and off the solar power the rest of the time.

Am I correct in assuming I need the three existing batteries for starting purposes? Is placing the ACR in place of the solenoid the way to do it? Is there a better way to do it? Any other problems with or improvemnets on this plan?

Thanks in advance for any assistance!

Jon

 

[iggi]

Unlikely you need three 12 volt batteries to start a 7.3. Most ambulances are running two starting batteries and two deep cycle for the module. If you are adding an extra bank of batteries strictly for the fridge and such then the BatteryLink should suffice. https://www.bluesea.com/products/7611/BatteryLink_Automatic_Charging_Relay_-_12V_24V_DC_120A If you want more control of how you are charging your deep cycle batteries and are possibly considering lithium then a DC to DC charger might be a better choice. https://www.victronenergy.com/blog/2019/10/10/new-product-orion-tr-smart-dc-dc-charger/

 

[jhoyt]

Unlikely you need three 12 volt batteries to start a 7.3. Most ambulances are running two starting batteries and two deep cycle for the module. If you are adding an extra bank of batteries strictly for the fridge and such then the BatteryLink should suffice. https://www.bluesea.com/products/7611/BatteryLink_Automatic_Charging_Relay_-_12V_24V_DC_120A If you want more control of how you are charging your deep cycle batteries and are possibly considering lithium then a DC to DC charger might be a better choice. https://www.victronenergy.com/blog/2019/10/10/new-product-orion-tr-smart-dc-dc-charger/

Iggi,

Thanks for the help!

Two batteries for starting and two for the module was what I'd planned on, but there's only one under the hood. I could break up the pair in the module, I suppose, but I thought I read somewhere that breaking them up was a bad idea? I figured it would be easier to add separate deep cycles and leave the 'extra' starting battery where it is, since I'll be buying them either way.

I'm afraid lithiums are way beyond my budget.

Jon

 

[Bikersmurf]

I’ve got a ‘97 With a 7.3.

If your module has space I’d recommend swapping your two batteries in if for two 6V golf cart batteries. They are about 10” tall.

I’d then install a srock battery box on the passenger side frame rail for a second starting battery. Originally E350s came with one there so it shouldn’t be hard to setup.

Then isolate the two 6V + 6V paralleled GCBs using a Blue Sea ACR. I used a 120 amp ACR, but to do it over I’d buy the 500 amp instead. I’d planned on running the alternator directly to the house (module) batteries, but the existing alternator wiring didn’t like it setup that way.

The 120 amp ACR will handle my alternator’s full output for 5 minutes, so it’ll be fine wired to the house batteries. However, if I ever want to run full load (2000 watts) on the inverter for more than 5 minutes I’ll need to add a battery switch to bypass the ACR to avoid cooking it.

GCBs are way better deep cycle batteries than any 12V marine deep cycle. I’ve got details and pictures in my thread of my 6V Interstate GFB upgrade.

 

[jhoyt]

Thanks for the reply, Bikersmurf. My battery compartment has plenty of room for golf cart batteries. In fact, it looks like if I took out the sliding tray, I could fit 4 batteries in there. I could leave the starting batteries alone and add some for the module. They'd be a little hard to access, but then so is a box on the frame rail. Anything wrong with that idea?

I'll read your thread to find out more about golf cart batteries. I'm trying to keep this low cost, but quality power management is important.

 

[Bikersmurf]

The second starting battery on the frame rail isn’t too bad to access. It helps that it’s OEM and planned out, not just thrown in there.

6V are about $120 usd each. There not terrible. I paid about $90 for a pair that were like new. A TRUECHARGE microprocessor controlled will keep them healthy for a long time. A friend has got 6+ years out of his and they’re still going strong.

 

[jhoyt]

Where did you find them for $90 a pair?

 

[luthj]

Sams club and some Batteries+ sell the Duracell brand GC2 6V batteries. These are actually made by Deka, and are a fantastic value, at about 90-110$ each. They will easily outlast any "dual purpose" or similar battery by 2-5x.

 

[Bikersmurf]

Where did you find them for $90 a pair?

Private sale of 'used' batteries... a tree came down onto their trailer and totaled it. They had only been out three times since they converted to the Interstate GC2 batteries. Costco south of the 49th have Interstate Batteries for a decent price... North of the 49th only Kirkland (which some claim are Interstate) but I don't know about that theory.

 

[Deshet]

One battery for the 7.3 can be tough especially in cold weather. (they will start up on 1 battery although it isn't recommended)
Switch to synthetic oil for easier starting.
I would install a switch that allows you to start off the house batteries when needed.
You can also use a marine battery isolator switch to charge all batteries while driving.
The engine will make more power then the solar panels can generate while going do the road, especially if you have two alternators.

If you have space check out 8d house batteries Interstate sells blemished 8d's for $100 they usually last up to 10 years on houseboats or the larger motor coaches. They are very big and heavy but are proven and cheap. It is really hard to beat the capacity of 2 8d batteries without spending a fortune.

 

[luthj]

What voltage is the alternator(s)? Deep cycled Lead acid doesn't charge fast (or much at all) when voltages are below 14V. So the long absorb phase is best finished by the solar alone.

 

[Deshet]

Yo

What voltage is the alternator(s)? Deep cycled Lead acid doesn't charge fast (or much at all) when voltages are below 14V. So the long absorb phase is best finished by the solar alone.

You properly mean what is the amperage of the alternators versus the voltage. The system is a 12volt system.

Keep in mind that the vast majority of batteries used across the world have been lead-acid up until recent years. Better battery technology exists but the costs aren't very competitive unless someone has a specific need. Honestly, I have seen a lot of AGM batteries fail early.

 

[luthj]

No, I mean the specific measured voltage of the alternator (I assumed 12v nominal). There is a huge difference in the life of a lead acid battery when its not fully charged after being deep cycled (a true 100% charge takes 8+ hours at the correct voltage). A deeply cycled battery will not charge fully at 13.8V, but at 14.2-14.4V it will charge fully. The higher in that range it is, the faster the absorb cycle takes. You can cut hours off the absorb time by going from 14.0 to 14.4V.

On long drives disconnecting the alternator from the house bank (assuming its not at least 14.1V output) will allow the solar controller to finish the absorb cycle at the better higher voltage. If the bank is pretty deeply discharged, doing the initial bulk charge from the alternator (assuming well sized cables) can speed the whole process along.

 

[iggi]

In my limited experience it seems the ambulances are typically setup to charge aggressively. Here's a pic of the electrical certification plate from mine.

 

[Deshet]

everything on the ambulance is built for extreme duty and then some.
Your best bet is to figure out your required loads and duration and then the battery bank that makes the most sense.
If you go with Lead Acid, quality can usually be determined by weight. The heavier a lead-acid is in the same group size the better the quality. An 8D is extremely heavy (120 pounds) but it will outperform two 6v golf batteries. Most will be well served by 2 deep cycle 6v golf cart batteries or 1 deep cycle 8D. My GEM car has 6 AGM batteries and the charge controller required modification to keep the AGM batteries charged properly. I believe that alternators designed for lead-acid may have issues charging AGMs proper.

My c4500 ambulance came with 3 group 31 batteries and 2 alternators and it will run the rooftop RV style AC unit with the engine running or engine off without shore power. I have not tested it long enough parked to kill the batteries but I was surprised that everything worked so well. It will also run the mini-refrigerator. The government agency special ordered it with a Rooftop AC.

As a side note if you have an alternator go bad in your ambulance have it rebuilt because the over the counter replacements usually have much lower amperage ratings.