Alternator for 24 volt starting AND 24v Inverter Lithium bank

[EvRv]

I have a big alternator on my bus. Over the road air was removed. What do I need to use the alternator to charge the bus start batteries, Dc normal bus devices like lights, dash, etc. and to use it with 2 Trace sw4024 inverters and a 24v 400Ah LifePO4 battery bank? Wouldn't an alternator be more efficient than running the diesel generator a 12.5 kw Onan?

 

[John Frum]

I have a big alternator on my bus.

How big?

Over the road air was removed.

You mean air conditioning?

What do I need to use the alternator to charge the bus start batteries,

A dc clamp meter should help you answer this question.

Dc normal bus devices like lights, dash, etc. and to use it with 2 Trace sw4024 inverters and a 24v 400Ah LifePO4 battery bank?

You are mixing the chassis loads with the house loads.
The dc clamp meter mentioned above should help answer those questions.
The trace 4000 watt inverter is probably the biggest load by far and will need a battery.

 

[EvRv]

How big?

You mean air conditioning?

A dc clamp meter should help you answer this question.

You are mixing the chassis loads with the house loads.
The dc clamp meter mentioned above should help answer those questions.
The trace 4000 watt inverter is probably the biggest load by far and will need a battery.

The alternator is on a Prevost Detroit Diesel series 60. It is 24v 270 amp. I do have also a Vanner volt master 100 amp equalizer and a voltage regulator. What I am trying to find out is what type of transfer switch are people on here using when running a single Altenator. Prevost had a big monstrous whole bay ac installed when shells were used to transport 50 or so passengers. These are called over the road air. They are often removed when the seats are removed and the shell is sold for converting. That frees up Altenator capacity. I am an industrial electrician. I know how to use many types of meters. I just don't have a block diagram or blueprint for a bus to RV conversion showing an actual system on a bus that I could copy. I bought some items with the shell but not all. I could compare if I could just find someone willing to give a diagram of their system. I could just plug in the pieces of the puzzle I have.

 

[Sirtate]

I assume your house batteries are running 24v also.
Are you looking for something to isolate the starting batts when the engine shuts down, and tie everything together when the engine is running?

In its simplest form an isolator switch with an appropriate amperage rating would do it. (assuming the house batts are grounded to the chassis)
You would have to manually "turn the switch" whenever you feel you need to tie/untie the two sides.
There are relays that will do the same thing automatically when the 'Ignition' switch is engaged...

When travelling down the road the 6500w the alternator can provide will be most efficiently taken from the DD60.
Of course the generator would be the best fit when parked.

As mentioned earlier, a house battery bank is needed, Make sure it has sufficient capacity to run that 4000w inverter...

 

[EvRv]

I assume your house batteries are running 24v also.
Are you looking for something to isolate the starting batts when the engine shuts down, and tie everything together when the engine is running?

In its simplest form an isolator switch with an appropriate amperage rating would do it. (assuming the house batts are grounded to the chassis)
You would have to manually "turn the switch" whenever you feel you need to tie/untie the two sides.
There are relays that will do the same thing automatically when the 'Ignition' switch is engaged...

When travelling down the road the 6500w the alternator can provide will be most efficiently taken from the DD60.
Of course the generator would be the best fit when parked.

As mentioned earlier, a house battery bank is needed, Make sure it has sufficient capacity to run that 4000w inverter...

When I bought bus it had eight 8D 24 volt batteries and two 4400 watt trace inverters. The batteries aged out before I could get any use out of them. Didn't know at the time thought they were new. So I plan to get two 24v 200Ah LifePO4 batteries for 400Ah at 24v and run the inverters stacked on the bank. I do have a 12.5 kw generator. It is installed and working along with shore power. Right now I just have a breaker panel with the two 120 legs that has 3 breakers for the roof ac units and 3 breakers for receptacles. But wouldn't it be more economical to get an isolator and use the Alternator to charge the house and chassis batteries while driving. I'm not clear on that. Especially since I need to run at least 1 roof ac and a dorm size fridge going down the road. Is there actually a device that controls a generator, inverters, an Altenator and possibly an mppt solar charge controller. Just understanding how the mppt could integrate with 5he inverters would be helpful too.

 

[EvRv]

I assume your house batteries are running 24v also.
Are you looking for something to isolate the starting batts when the engine shuts down, and tie everything together when the engine is running?

In its simplest form an isolator switch with an appropriate amperage rating would do it. (assuming the house batts are grounded to the chassis)
You would have to manually "turn the switch" whenever you feel you need to tie/untie the two sides.
There are relays that will do the same thing automatically when the 'Ignition' switch is engaged...

When travelling down the road the 6500w the alternator can provide will be most efficiently taken from the DD60.
Of course the generator would be the best fit when parked.

As mentioned earlier, a house battery bank is needed, Make sure it has sufficient capacity to run that 4000w inverter...

I plan to get two 24v 200Ah LifePO4 batteries. Should I run split phase with 1 bank I have two 4400 watt inverters. Can't I get by for starters with two batteries in 1 parallel bank? That would be 9600 Wh available to each inverter so if only one inverter has loads it would have access to all the power. Otherwise they would just share the benefits of going Lithium.

 

[John Frum]

Just in case anyone is curious.

https://vanner.com/manuals/70-60.pdf

Neat bit of equipment.
Yours is only the second or possibly third time I come across anything like this.
I'm not sure how nicely that will play with LFP batteries.
What is the maximum load in amps running off the 12 volt subsystem?

 

[Sirtate]

I plan to get two 24v 200Ah LifePO4 batteries. Should I run split phase with 1 bank I have two 4400 watt inverters. Can't I get by for starters with two batteries in 1 parallel bank? That would be 9600 Wh available to each inverter so if only one inverter has loads it would have access to all the power. Otherwise they would just share the benefits of going Lithium.

You would need the house batts to be wired in parallel to keep 24v, if that is what the starter batts provide.

Wire your inverters to the house batts.
You would then wire the positive posts of the starting batts to the positive posts of your house batts, with an isolator switch along the run, so you can isolate the two banks.

This will allow you to run all of your house loads through your inverters, like your A/C units, and keep the house batts charging from the alternator.
But you would need to isolate the starter batts, or else you may not be able to start the engine when parked.(!)

When you are parked, you would drain the house batts, and once the DD60 is running, you could then tie the two banks together to charge the house batts.
Lithium batts don't take kindly to the high currents required to turn a starter motor, so they shouldn't be tied together until the engine is running.
As well, Alternators don't take well to the high currents that Lithium batteries can draw for long periods without some sort of buffer, like a lead acid bank, so your set-up is effective for both those issues. (as long as the starting batts are 24v)

 

[BenQ]

Alternator -> 24v 8D starter -> relay isolator (on/off with engine) —> 24v lithium batteries -> inverters - house loads

 

[daveola]

Alternators don't take well to the high currents that Lithium batteries can draw for long periods without some sort of buffer, like a lead acid bank.

What about when it's the other way around - the alternator (say 300A) is much larger than the max charge current for the lithiums (such as 100A for EG4-LLs)?

And does having the alternator charging the house batteries (lithium) and the vehicle batteries (SLA) help protect the lithiums in that case?

 

[BenQ]

What about when it's the other way around - the alternator (say 300A) is much larger than the max charge current for the lithiums (such as 100A for EG4-LLs)?

And does having the alternator charging the house batteries (lithium) and the vehicle batteries (SLA) help protect the lithiums in that case?

Yeah the alternator should not be attached straight to the lithium batteries.

I am of the opinion that keeping a couple of the 8D batteries between the alternator and the lithium batteries will reduce the amps enough (8Ds have a lot of resistance) to make it work. You could put some 8Ds in place of the lithium batteries in my scenario and out a clamp meter on the cable to see what kind of amps you get off the alternator going through the starter battery then the relay then a set of 8Ds.

 

[daveola]

Yeah the alternator should not be attached straight to the lithium batteries.

I am of the opinion that keeping a couple of the 8D batteries between the alternator and the lithium batteries will reduce the amps enough (8Ds have a lot of resistance) to make it work. You could put some 8Ds in place of the lithium batteries in my scenario and out a clamp meter on the cable to see what kind of amps you get off the alternator going through the starter battery then the relay then a set of 8Ds.

I'm a bit confused - are you suggesting that I have the alternator attached to the SLA 8Ds in parallel with the Lithiums? That wouldn't really stop the current flowing into the Lithium batteries, I don't think. And I can't put them in series...

 

[BenQ]

I'm a bit confused - are you suggesting that I have the alternator attached to the SLA 8Ds in parallel with the Lithiums? That wouldn't really stop the current flowing into the Lithium batteries, I don't think. And I can't put them in series...

Yes, connect them in parallel with fuses and Vanner volt master 100 amp equalizer in-between.

Do this experiment with a DC clamp meter capable of measuring up to 300 amps.

1. Connect the Alternator (270 amps) -> 24v 8D starter battery (measure how many amps are going into the starter battery write it down)

2. Connect a relay isolator (on/off with engine) between the starter battery and a 24v 8D house battery bank (measure how many amps are going into the house battery and write it down)

3. Connect the Vanner volt master 100 amp equalizer to the 24v 8D house battery bank (measure how many amps are going into the Vanner and write it down)

At this point there should be sufficient load on the alternator to reduce the amount of charging amps to safely add a bank of 24v LiFePo4 batteries in parallel with a 100amp fuse in between.

If for some strange reason you’ve got all this shit hooked up to that beast of an alternator and you’re still measuring more than 100 amps going into your 8D house batteries then throw one of your tracer inverters on the 8D house batteries and run that fridge and A/C unit.

At this point your alternator will be overloaded lol and you will definitely be able to safely add a bank of 24v LiFePo4 batteries in parallel with a 100amp fuse in between.

 

[BenQ]

With this battery and a 200 amp fuse, you should be just fine! Redodo 24V 200Ah LiFePO4 Battery with 200A BMS Lithium Battery, Max. 5120Wh Energy Capacity, 4000-15000 Deep Cycles & 10-Year Lifetime, Solar System Back-up Power, RV, Trolling Motor etc. https://a.co/d/3QGmETT

 

[Sirtate]

I'm a bit confused - are you suggesting that I have the alternator attached to the SLA 8Ds in parallel with the Lithiums? That wouldn't really stop the current flowing into the Lithium batteries, I don't think. And I can't put them in series...

It really isn't the amperage, it's how the Lithiums draw their amps.

They start drawing very quickly and maintain that draw until they approach fully charged.
While this could be within spec of the alternator, they draw high amperage for longer than the alternator can handle, causing it to overheat.

The FLA in between, even in parallel, moderates this. (something to do with the AC/DC cyclic current produced by the alternator)

this Victron video talks about this, but understand that they are trying to sell you battery chargers...

Careful - Alternator Charging Lithium - Victron Energy

Charging lithium batteries from an alternator, be that in a boat or vehicle, presents some challenges when compared to the straightforward nature of charging lead based batteries. The video in this blog highlights these lithium challenges and shows you what can happen when things go wrong –...

www.victronenergy.com