Re-doing VanDOOM's 12v charging system. Suggestions?

[Shocker]

Hey guys, I have pulled out the huge Leece Neville alternator, sanded the brushes and the rotor and now it works. But I am still most likely going to swap over to a 3g alternator for ease of replacement and lower cost. I have the correct bracket for the 460 so I am good there.

What is concerning me is all the 2 guage feeds that run here and there for the ambulance stuff. There is the batter connector that comes from somewhere down below, the alternator main that disappears somewhere down below and 2 more large feeds that go the same route. I followed them down and where they go and I have the sort of mapped, but I want to redo it. Here is my plan for just those large feeds:

I know it is a simple thing, but does this seem correct? It is pretty much the same as now but I know where it all is. I will add fuseable links in the main feeds etc as well. I just want a redone 12v block for the mains so I know what's what. I will eventually will be adding a second battery, but I want to square this away first.

All ideas/advice is welcome!

 

[Shocker]

Nobody?

 

[DiploStrat]

???

I'm not sure I totally understand your question, but, in simplest terms, were I rewiring things ...

-- Run the biggest, shortest cable you can find (2/0 sounds good) from your alternator(s) to your starter battery(s). My current oracle on these things is Chris Gibson: http://www.smartgauge.co.uk/alt_how.html

-- Run from your starter battery to all of your truck loads, unless you are certain that some of those loads should be connected directly to the alternator. (I don't know of any reason why any should, but I don't do this for a living.)

-- Run a similarly large cable(s) from each starter battery to an automatic charging relay to your camper battery bank. Use the appropriate one of these: http://www.bluesea.com/products/category/Automatic_Charging_Relays

-- Connect a solar kit to your camper battery bank.

-- Connect all of your camper loads to the camper battery bank.

In other words, alternator>battery>12v loads, NOT alternator>12v loads>battery.

Hope this is useful.

 

[Shocker]

It is helpful! That was my biggest concern was to go to the distribution block and out from there or direct to the alternator and then to the loads.

Essentially the main 12v wiring seems to go to a switch in the cab that controls the main switch panel that feeds the various ambulance loads.

I plan on adding solar eventually as well as a secondary battery.

Thanks for the links as well, I will take a look at them tonight. I am not an electrical guru, but all of it seems simple enough. That is until you burn the rig to the ground!

 

[DiploStrat]

Pay your Money, Take your Choice (or Chance)!

... I am not an electrical guru, but all of it seems simple enough.

Conventional wisdom is that you want the battery between your loads and the alternator so that the battery can meet any instantaneous demands and buffer the alternator against those demands.

None of this is hard, but it IS complex. I have spent the better part of a year plowing through this stuff for my own truck. Send me an e-mail and I will send you a small paper that I wrote to get my head around the problems/parameters. Haven't written the second paper; the answer, yet, but basically:

-- Voltage matters - modern AGM batteries want 14.4v @ 70F. Open lead acid batteries want even more. And all of them want more than 15v when the temps drop below freezing. A modern truck will do this easily, an older truck won't. A 12v battery is "fully charged" at about 12.7v. The charge voltage must be a lot higher than that or the charge rate will be too low.

-- Size matters - low voltage systems need huge cables to pass enough current. If the cable is too small it will not pass enough current and, just as bad, the alternator will not see your second battery.

-- Current matters - AGM batteries want at least 25A of charge for every 100Ah of battery. They prefer at least 100A per 100Ah and Lifeline batteries can take up to 500A for every 100Ah of battery. That means you probably want at least 200A of alternator and about 100w of solar for every 100Ah of battery. Remember, you need to replace between 110Ah and 150Ah for every 100Ah you use.

-- Time matters - while it is easy to think of wiring like piping water, in fact, you are producing a chemical reaction in the battery and this takes lots of time. (One reason why a solar kit or overnight shore power is so important.

-- Memory matters - no, a lead acid battery does not have a "memory" like a Ni-Cad, BUT, if it is not fully recharged often, then it will start to lose capacity.

As you will gather from many threads in this forum, scholars differ on how to do all of this. Each of these will work in the real world, provided you understand the advantages and disadvantages:

-- Manual switch - If big enough and if you don't forget.

-- Relay or solenoid - If big enough, well controlled, and coupled to big cables.

-- Battery to Battery Charger - If big enough or doubled. Good if your truck voltage is too low.

-- Alternator to Battery Charger - Good answer if your truck voltage is 13.5v and you use big cables.

-- Voltage compensating diode isolator - Needs to be big enough not to blow and needs big cables.

-- Dedicated second alternator and regulator - Probably the best answer if large enough. Appears that this is what Roadtrek may be doing on their E-Trek.

If you use a system that does not combine your batteries, then you will probably want some form of trickle charger so that the camper battery can charge your truck battery when you are parked.

Again, each of these CAN work (better or worse) and none of them will work if poorly implemented.

Offered in the belief that this is correct and helpful.

 

[4x4junkie]

Agree with all the above. 2/0 wire may seem like overkill to your house bank, but definitely it is not (the smallest voltage drop, say 0.5V can easily cut in half the charge current to your battery). You want the voltage drop to be less than 0.2V at the full rated current of your alt, ideally.

You'll really like the 3G alt upgrade if you're still running a 2G. I did that very swap on mine and it's night & day difference in charging ability (before the voltage would drop down at idle just running the headlights and heater blower together, now it holds steady).

 

[Shocker]

Alright! Thanks for all the great advice!

I am working on finding a proper alternator to replace the big ambulance one. I was leaning towards the 3G which everyone says is great, but now I am thinking of using a more modern Leece Neville 200amp. Still working out the details for the mounting. If not, 3G it is.

All the main feeds are 2/0 I think. I need to double check but I think they are big enough.

So would you guys just eliminate the distribution block idea? Here is a diagram I found that matches the way VanDOOM's charging system is and I modded it with the house line. I pretty much think I can eliminate one of the 2 feeds. What do you guys think of this one?

 

[DiploStrat]

So would you guys just eliminate the distribution block idea?

Not eliminate it, simply place it AFTER the starter battery, not between the alternator and the battery.

 

[Shocker]

Roger that. I am not sure I need it with the single connect for the house. Maybe one for misc 12v sources in the future though.

 

[Shocker]

I think I got it figured out. At least for the main charging system. I will post it up in the build thread.