Solving Ambulance Camper electrical issues plus induction cooking vs propane.

iggi

Ian
EDIT/UPDATE

Updated the thread title as my initial idea of running a fully separate 12V system was a dumb one.
Thanks to help here and off line I found the real issue (faulty power connect switch) and the thread rapidly turned into sorting out the best battery bank and discussing electrical cooking systems vs propane based.
Leaving all comments as they may help someone else.

-------

Hey ya'll,

My head is spinning with options and I'm hoping someone can steer me straight here.

I've got a 2009 Crestline Ambulance.
I'd like to add a battery that's dedicated to running the fridge, furnace, fan, water pump and a set of lights.
I want to retain the original electrical as I like the various doo-dads but it's not optimal for constant use due to the parasitic draw from the relays and such.

Easy enough to add an extra battery and even to connect my solar to it.. but am unsure of the best way to tie it into the current charging system (alternator plus shore power charger/inverter)

Currently it's got 2x 12 volt starting batteries and 2x 12 volt deep cycle that connect to the panel and inverter.

Below is my rough drawing of the system as I understand it.

Specific questions:

  1. Is this as simple as adding a battery balancer between the two deep cycle packs?
  2. Or is going to an Automatic Charging Relay the better method? Could I replace the current Diode Battery Isolator with a single ACR that would run all three sets of batteries
  3. Any specific part recommendations? I was browsing the Blue Sea site but am as confused as before. As I have 320 amps of Alt capacity would I need an ACR capable of that? Confused as the current diode isolator is rated for 240amps.
  4. The battery relay gets hot as hell. I believe this is the one that's activate from the front ambulance connect switch. Seems like it is the source of the drain. Is there a higher quality relay you'd recommend?

    Screen Shot 2019-09-04 at 11.56.22 AM.png
Thanks in advance!
 
Last edited:

dreadlocks

Well-known member
I would work on getting the deep cycle bank workable, and if you need more capacity then make it a 4 battery bank and go w/6v GC batteries.

Those high amp relays pull a TON of friggin power, thats definitely a drain on you.. You can get a 220A Victron Battery protect, its a solid state relay and draws almost nothing in comparison.. The Amps is determined by your loads, not by your charge source.. two batteries will never consume 320A of power to charge up, mebe 40-50A max.. whats your biggest load?
 

luthj

Engineer In Residence
The best approach to these ambos, is to go through the whole system, and redesign the core of it. Peripheral consumers, and the fuse panels can usually be left alone. The battery isolation and charging setups are generally designed around lots of engine run time. High current always on relays, diode isolators which create big voltage drops, etc.

I would start from scratch with true deep cycle batteries (GC2 size is a great option). Get a split charge relay for alternator charging. If your shore power charger is good quality/voltage, connect that up.
 

iggi

Ian
Thanks,

Not counting the inverter.. 40-50 amps max.
Thanks for the suggestion on the Victron.

I already know that I'm short of capacity with the current two battery bank.
Even though the current deep cycles are only three months I was considering replacing with 4-6 golf cart batteries but was just given one these (telco battery) and it'll fit very nicely in a bit of dead space. So, I'm between free and good use of space I'm trying to make it work. :)

Ian



I would work on getting the deep cycle bank workable, and if you need more capacity then make it a 4 battery bank and go w/6v GC batteries.

Those high amp relays pull a TON of friggin power, thats definitely a drain on you.. You can get a 220A Victron Battery protect, its a solid state relay and draws almost nothing in comparison.. The Amps is determined by your loads, not by your charge source.. two batteries will never consume 320A of power to charge up, mebe 40-50A max.. whats your biggest load?
 

iggi

Ian
That's likely the best way.. but I don't have the time and I don't see the ROI.
Happy enough with the current system. It's great for short use, just not for 12 volt items that have to run either constantly or for long hours per day.

Ian


The best approach to these ambos, is to go through the whole system, and redesign the core of it. Peripheral consumers, and the fuse panels can usually be left alone. The battery isolation and charging setups are generally designed around lots of engine run time. High current always on relays, diode isolators which create big voltage drops, etc.

I would start from scratch with true deep cycle batteries (GC2 size is a great option). Get a split charge relay for alternator charging. If your shore power charger is good quality/voltage, connect that up.
 

dreadlocks

Well-known member
yeah those high amp relays are assuming engine is running like luthj said, thats the only way they are usable.. if they are engaged w/out engine running its unacceptable load.. your probably looking at 5-10A continuous just to keep that relay active... whereas a solid state relay like battery protect is 1.5mA (0.0015A) to keep it active.

How big is the inverter? are you wanting to be able to power inverter completely off engine?

A little bit of rework and upgrades on electrical system would be worth it IMO, do it right and you have potential for so much more capacity and output than non ambulances could dream of.
 

luthj

Engineer In Residence
You don't need to replace everything, but you need to create a accurate diagram of everything that's currently in use, and what kind of power it consumes (this includes wire gauges for all the main runs). Otherwise you are going to end up throwing parts and money at it. It may be that you just need to swap a couple of batteries, change the isolator, and call it good. But until you know what you have and how it works, its just a guessing game.

90%+ of the wiring will likely stay the same, but the few bits that need changed will have a big impact I bet.

Depending on your needs an budget, you could easily build an electrical system with enough capacity to run an induction cooktop, lights, laptops, etc, without any issue.
 

iggi

Ian
Got it, I misunderstood your initial suggestion as being I should rip it all out.
Thanks!

You don't need to replace everything, but you need to create a accurate diagram of everything that's currently in use, and what kind of power it consumes (this includes wire gauges for all the main runs). Otherwise you are going to end up throwing parts and money at it. It may be that you just need to swap a couple of batteries, change the isolator, and call it good. But until you know what you have and how it works, its just a guessing game.

90%+ of the wiring will likely stay the same, but the few bits that need changed will have a big impact I bet.

Depending on your needs an budget, you could easily build an electrical system with enough capacity to run an induction cooktop, lights, laptops, etc, without any issue.
 

iggi

Ian
Hi,

Yes, the inverter is 3000 watts peak and wil run straight from batteries or from shore power.
Already wired up with three 120 volts plugs in the box. It's pretty slick.

The relay runs all the time the box 12 volt system is turned on. I was scratching my head where the loss was occuring until I put my hand in the panel and felt the heat coming off the relay. Winner winner chicken dinner. Plus I suspect all the illuminated switches are running incandesent bulbs and not LED. Just haven't checked yet.

yeah those high amp relays are assuming engine is running like luthj said, thats the only way they are usable.. if they are engaged w/out engine running its unacceptable load.. your probably looking at 5-10A continuous just to keep that relay active... whereas a solid state relay like battery protect is 1.5mA (0.0015A) to keep it active.

How big is the inverter? are you wanting to be able to power inverter completely off engine?

A little bit of rework and upgrades on electrical system would be worth it IMO, do it right and you have potential for so much more capacity and output than non ambulances could dream of.
 

iggi

Ian
more thinking and more questions:

Wouldn't a DC to DC battery charger be the simple way to charge the additional battery bank without requiring any changes to the rest of the electrical system?
Something like this Renogy one?

Screen Shot 2019-09-06 at 3.03.13 PM.png

@Bikersmurf When you replaced the original diode isolator with the ACR, did you also eliminate the original power disconnect switch in favour of the one on the ACR?

@luthj You got me thinking about the induction cooktop. I'd ruled them out earlier but perhaps I was too hasty. Would have a lot of advantages over lpg. Do I have this calculation roughly correct. 1800 watts is 15 amps draw. I'd expect the inverter to be roughly 85% efficient. So, the inverter would need roughy 18-20 amps to run the cooktop at full power?

Just for general interest I've attached the schematics and info plate that are all still attached to the power closet. Plus a pic of the power cutoff switch that runs hot hot.

IMG_0755.jpgIMG_0756.jpgIMG_0757.jpgIMG_0759.jpg
 

luthj

Engineer In Residence
My induction cooktop numbers are below. It all depends on what you are cooking, but it varies from 5AH (at 12v) for some water for coffee or tea. All the way to 60Ah for cooking some pasta, and pan frying some meat/veggies. My toaster oven modified with insulation does pizzas for about 20-25AH.

To bring 1.5 quarts of water to boil (large cast iron pan) and medium boil for ~10 minutes used 0.175kWhrs if I remember correctly. Note that I had the pan covered as this reduces heat loss substantially.

Pan frying a chicken breast used about the same power (again covered pan). If you can keep the pan insulated the power necessary to maintain 350F+ is not that large.

At 15% inverter losses that is 0.2kWhrs. At 12.0V that is 17AH.
 

iggi

Ian
Thanks @luthj Appreciate your input!

My induction cooktop numbers are below. It all depends on what you are cooking, but it varies from 5AH (at 12v) for some water for coffee or tea. All the way to 60Ah for cooking some pasta, and pan frying some meat/veggies. My toaster oven modified with insulation does pizzas for about 20-25AH.
 

Bikersmurf

Expedition Leader
more thinking and more questions:

Wouldn't a DC to DC battery charger be the simple way to charge the additional battery bank without requiring any changes to the rest of the electrical system?
Something like this Renogy one?

View attachment 537003

@Bikersmurf When you replaced the original diode isolator with the ACR, did you also eliminate the original power disconnect switch in favour of the one on the ACR?

@luthj You got me thinking about the induction cooktop. I'd ruled them out earlier but perhaps I was too hasty. Would have a lot of advantages over lpg. Do I have this calculation roughly correct. 1800 watts is 15 amps draw. I'd expect the inverter to be roughly 85% efficient. So, the inverter would need roughy 18-20 amps to run the cooktop at full power?

Just for general interest I've attached the schematics and info plate that are all still attached to the power closet. Plus a pic of the power cutoff switch that runs hot hot.

View attachment 537013View attachment 537014View attachment 537015View attachment 537016

Still have the power disconnect. The inverter is wired directly to the batteries. The disconnect solenoids draw too much power to want them powered up when not needed.
 

iggi

Ian
After a few hours buried in the power cabinet, reviewing wiring diagrams and reading specs... I've got a much better understanding of how the electrical system works. It's quite beautifully designed.
My core problem seems to be a faulty power connect switch. It gets so hot that you can barely touch it.
Put a jumper with a 30amp fuse to skip past it and the heat/excess draw issues seem to be gone.

Now in hindsight I can see my ignorance had me chasing the wrong things around.
I'll have to run a full test in the next couple days but I'm confident that running a separate battery bank and such for the fridge/furnace is completely unnecessary.

As both @luthj and @dreadlocks noted, with just a few component changes I'll have a great system.

Plans moving forward:

1. Replace the Albright SW180 power connect switch (that even when working properly always consumes power) with a Blue Sea 7700 Remote Battery switch that's rated up to 500amps and has zero draw in either the on or off position.
2. Replace the diode isolator with a proper ACR (probably the Blue Sea 7620)
3. I'll either add two more FLA deep cycle batteries to my pack (4 total) or replace them with four of the AGM telco batteries. I was trying to be a cheap ass by combining my existing FLA deep cycle batteries with the AGM Telco batteries but the work in isolating them seemed to be more effort than it was worth, plus I discovered that the Xantrax charger can either be set to charge flooded lead acid batteries correctly, or AGM batteries correctly but not both at the same time.

Still unknown... There is a dedicated battery combine switch that runs two solenoids that connect the starter batteries to the house batteries to provide a ass ton of starting power. I don't know if those solenoids draw any power in the off position. If they do then I'll replace them with the ACR.

Other than those solenoids I don't see anything else that could cause much parasitic loss. (unless there's another faulty switch somewhere, etc)
 

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