Dual Alternators, Dual Battery Banks, Switching Between Them

[ExpoMike]

Hi all,

So my M1010 (Desert Turtle) project is in the planning phase and I am working on figuring out some of the electrical. For those who do not know, the M1010 has a dual alternator system to provide 24 volts for the starting system and a couple systems that are related to the ambulance box (A/C and heater). I am eliminating those box systems and will change the starter over to a 12 volt version. Everything else on the truck is 12 volts.

The previous own did what in the M1010 world is called "plan B" alternator conversion (this is from the Steel Solders site), which uses two 12 volt, self exciting alternators, one to charge the front engine battery, one to charge the rear engine battery. Each battery gets 12 volt charging but the batteries are wired in series to give 24 volts for those few system. I converted my past M1010 to be 100% 12 volt and just requires the starter change and putting the engine batteries in parallel. Each of these alternators are 160 amps and are medium duty truck sized (J180 mount - http://www.prestolite.com/pgs_produ...id=35066&item_series_id=94&refresh=1322425227 ) So that is the back story.

Here is where I am at. Once I finish converting everything to 12 volt here is my plan. I am going to wire one alt to charge/run the engine/truck cab systems. The other alt will be wired to run only the house battery system (the box). Basically this keeps the two system independent of each other. Since I want the ability to have redundancy, I want to be able to join either system to either alternator in the event of an alternator failure in the field. This does not need to be an automatic system and can be a manual "switch" to connect either systems together.

Does anyone know of a switching unit that would allow me to tie either systems to either alternator in a failure situation but keep these two systems isolated during normal use?

Here's a picture of the rig, for reference and the only shot I have of the engine that shows the two alts.

Thanks

 

[luthj]

Personally I would wire both alternators in parallel, and put both batteries in parallel (one connected with a charging relay if you need them isolated for redundancy). Any low power 24V items are best served with a 12-24V DC-DC converter.

Is alternator charging your primary charging source for a house battery bank? if so, a better option would be to configure one of the alternators with a external regulator, and use a full digital control (programmable) regulator. This alternator would be dedicated for charging the house/Aux battery. A manual combine switch could be used to start/run the engine from the aux system as needed.

 

[ExpoMike]

Actually I might have answered my own question. It seems this Blue Sea switch basically will do what I am after. I would need to removed the belt and disconnect the wire to the alternator for the failed unit and then switch this to combine the two banks.

e-Series Dual Circuit Plus™ Battery Switch - Blue Sea Systems

350 Amps continuous rating for inboard gasoline or diesel engines.

www.bluesea.com

Anyone see a flaw in this?

 

[luthj]

That switch is one option. Note that if one of your alternators or batteries nukes (like a dead short), a switch like that won't work, as you would want to isolate the damaged system, and still use the vehicle electrics.

 

[ExpoMike]

Personally I would wire both alternators in parallel, and put both batteries in parallel (one connected with a charging relay if you need them isolated for redundancy). Any low power 24V items are best served with a 12-24V DC-DC converter.

Is alternator charging your primary charging source for a house battery bank? if so, a better option would be to configure one of the alternators with a external regulator, and use a full digital control (programmable) regulator. This alternator would be dedicated for charging the house/Aux battery. A manual combine switch could be used to start/run the engine from the aux system as needed.

There will be NO 24 volt systems left in the vehicle.

I would be running a full charging management system for the house batteries (looking at a RedArc Manager 30 and running a LiPo4 battery bank, with solar). Direct charging will be to the engine batteries which will be FLA or AGM type.

 

[luthj]

With lithium's high charge acceptance rate, you would come out ahead cost wise to use an external regulator configured for the lithium as a dedicated charger. You could easily get 90A at idle from that setup. You would need to stack several DC-DC chargers to get that level of charging.

I would then have one of the starter batteries wired as a backup with a charging/isolation relay. If the primary is dead, you can connect the backup for starting.

 

[rayra]

I think the combiner setup makes sense but I'd want the ability to decouple or isolate any alternator or battery from the setup if there's a failure. Couple more rotary switches would make that easy. Detecting the problem in a timely fashion to prevent other damage would be the real issue. I don't have an easy answer for that.

 

[ExpoMike]

I think the combiner setup makes sense but I'd want the ability to decouple or isolate any alternator or battery from the setup if there's a failure. Couple more rotary switches would make that easy. Detecting the problem in a timely fashion to prevent other damage would be the real issue. I don't have an easy answer for that.

I am not looking so much as a catastrophic failure but things like the alt regulator going out, belt breakage, bad bearing. Something that would keep the bank from charging. I can manually remove the charge cable from the alt, remove the belt and flip this switch and have the two systems running off one alt at that point. Really didn't want too many switches in the system as each one is a point of failure.

 

[shade]

I am not looking so much as a catastrophic failure but things like the alt regulator going out, belt breakage, bad bearing. Something that would keep the bank from charging. I can manually remove the charge cable from the alt, remove the belt and flip this switch and have the two systems running off one alt at that point. Really didn't want too many switches in the system as each one is a point of failure.

While they do introduce a point of failure, those switches can usually be bypassed by moving cables to a shared lug, and that's not too difficult to do in the field. The number of times you're likely to even need to cycle the switch is so low that I wouldn't worry about it.

 

[Bayou Boy]

While they do introduce a point of failure, those switches can usually be bypassed by moving cables to a shared lug, and that's not too difficult to do in the field. The number of times you're likely to even need to cycle the switch is so low that I wouldn't worry about it.

Exactly. I had one of the bad batch of Blue Sea switches in my boat. I was on the trolling motor when the radio cut off. Went to turn off the battery switch to investigate and the knob fell off in my hand. Rewired everything to one lug bypassing the broken switch and finished out my day. Blue Sea had recalled those and I hadn't got the memo so they sent me a redesigned replacement.

 

[Bones61]

I have four batteries in my M1010. Local police had converted it to 12volts. No switch to isolate them. Two batteries are under the compartments in the back. There is a switch behind the drivers seat that is a switch but is not hooked up. It might have been part of the military use. I have a roof top AC and a 12/120 converter