FMTV A1 - Relay that Identifies Engine is Running

[charlesrg]

I'm trying to connect a battery to battery charger to my M1083A1, the device has an ACC/Enable port. I'm trying to identify a place I could connect it so it would only enable when the truck engine is running so it would use the alternator and not discharge the batteries.

Does anybody knows if the FMTV has a D+ signal or another place power is only available when the engine is running ?

The goal is to charge LiFePo4 batteries from the engine alternator, and not discharge the start batteries when the truck engine is not running.

 

[GeneralDisorder]

I'm trying to connect a battery to battery charger to my M1083A1, the device has an ACC/Enable port. I'm trying to identify a place I could connect it so it would only enable when the truck engine is running so it would use the alternator and not discharge the batteries.

Does anybody knows if the FMTV has a D+ signal or another place power is only available when the engine is running ?

The goal is to charge LiFePo4 batteries from the engine alternator, and not discharge the start batteries when the truck engine is not running.

The Victron Orion smart DC/DC chargers have engine shutdown detection that doesn't require any additional wiring. It watches for the rising and falling voltages. They also have remote on/off switch capability - you could use the VR "E" terminal signal from the NC contact of K11 - that is the "Excite" terminal that starts the voltage regulator and is only present after oil pressure de-energizes the K11 relay (or if you shift the transmission out of neutral).

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[Ronmar]

Yea there is no discrete contact closure, K11 would give you 24V. You could use that drive a second relay as well,as enable the alternator to get a dry contact closure. You could also get a voltage sense module to monitor system voltage. When it goes over 13.8V it could provide the control signal like the Victron does.

What is your current alternator and service battery configuration?

 

[charlesrg]

Yea there is no discrete contact closure, K11 would give you 24V. You could use that drive a second relay as well,as enable the alternator to get a dry contact closure. You could also get a voltage sense module to monitor system voltage. When it goes over 13.8V it could provide the control signal like the Victron does.

What is your current alternator and service battery configuration?

I’m using the standard 100amps alternator 24V side to charge a 24V LiFePO4(bank. The charger does up to 800 watts and I can set the max voltage and turn it on/off via RS485, it also has the yellow cable that would turn it on only when voltage is present.

So it sounds like I need to invert K11 so when it opens I can energize the charger. Am I getting it right ?

 

[GeneralDisorder]

800 watts is near 30 amps. I wouldn't pull that much from the 100A alternator..... You do realize it's probably only putting out half it's rating at idle right? It's barely acceptable for the battery load. For SURE you need to drop to two batteries and even then..... pulling 30 amps off it at idle when it's full load output is probably closer to 50 amps sounds like a bad idea. You add the rest of the 24v loads and all the lighting..... nope.

You need the 260 amp, or something else with 200+ amp output that can push 100+ amps at idle.

The Victron's are 400 watts each. 17 amps. Can be paralleled. I'm going to run three of them for my house bank.... on my 300 amp alternator.

K11 NC contacts provide 24v when the oil pressure switch closes. Unless I'm not understanding it sounds like you just need to connect the E terminal on the VR (K11 NC) to the yellow wire. It's just a turn-on signal so it shouldn't be pulling any significant amps.

Also - that appears to be some AliExpress chinese garbage. I wouldn't allow that anywhere near my truck, expensive brushless alternator, or expensive LiFePo4 battery bank. Sell that junk to some other sucker.

 

[Ronmar]

How many truck batteries are you running? If you have 4, all the output of the 100A alt is spoken for. they really screwed up putting 4 large batts with this dual volt 100A alt(basically two 50A alts in series). The lighting load is half of your available 12v output and any 12v load significantly reduces the overall output of the alt…

if that controller is OK with any voltage as a sense input you might be able to get away with using the 24v K11 output directly. Depends on the specs of that device…

 

[GeneralDisorder]

if that controller is OK with any voltage as a sense input you might be able to get away with using the 24v K11 output directly. Depends on the specs of that device…

Yeah depends on the device - if it's anything like the Victrons - they only require > 3v for the remote on/off. So obviously very small current AND their schematic examples show it connected through a switch directly to the input voltage..... But that Chinese junk - yeah could want more current or not accept the charging voltage or something else weird..... . Could cause way too many problems to trust it IMO.

 

[charlesrg]

How many truck batteries are you running? If you have 4, all the output of the 100A alt is spoken for. they really screwed up putting 4 large batts with this dual volt 100A alt(basically two 50A alts in series). The lighting load is half of your available 12v output and any 12v load significantly reduces the overall output of the alt…

if that controller is OK with any voltage as a sense input you might be able to get away with using the 24v K11 output directly. Depends on the specs of that device…

The ACC (yellow wire) on the device will turn on charging if voltage is 10-40VDC, bellow that it will remain off. It's just for turning on. The real load goes under the other terminals.

Yeah depends on the device - if it's anything like the Victrons - they only require > 3v for the remote on/off. So obviously very small current AND their schematic examples show it connected through a switch directly to the input voltage..... But that Chinese junk - yeah could want more current or not accept the charging voltage or something else weird..... . Could cause way too many problems to trust it IMO.

Besides the ACC wire I can also set an under voltage protection, so I can ensure I don't discharge the batteries. And I can also set the output current.
This are all programmable and I can set it while running. I can put a controller that will ramp up the load and I can put a thermistor on the Alternator to ensure it does not overheat.

I was under the impression that I could get 30 amps from the alternator at idle with the truck batteries charged. Might need to get a new alternator or mod to run on 24V only with a off the shelf alternator.

 

[charlesrg]

The Victron's are 400 watts each. 17 amps. Can be paralleled. I'm going to run three of them for my house bank.... on my 300 amp alternator.

I looked at Victron, and I didn't like the enclosure not being water resistant , the lack of control features and the small current output. I should get 27Amps of one device and the goal is to add 2 for about 50Amps total. They will be installed inside the battery box. The price is also more attractive than the Victrons.

I looked at the Victron Buck Boost as well, but the device even had a fan to keep it cool, did not look like a device that could be exposed to the elements.

 

[Ronmar]

The ACC (yellow wire) on the device will turn on charging if voltage is 10-40VDC, bellow that it will remain off. It's just for turning on. The real load goes under the other terminals.

I was under the impression that I could get 30 amps from the alternator at idle with the truck batteries charged. Might need to get a new alternator or mod to run on 24V only with a off the shelf alternator.

10-40V… then the signal off of K11 pin 87A should work fine as engine sense.

yes you can use surplus alt power when the service batteries are fully charged, but thats the problem, knowing the batts are full, and if you are still running four of the 6T batts, that can take quite a while to accomplish. Using an engine start signal as the trigger for the secondary charge controller does not take this into account, and you could be piling onto an already full alternator…

 

[hike]

I assume the LiFePo4 are for a habitat? What is your use case? Is your alternator the only charging source you are planning to use?

 

[charlesrg]

I assume the LiFePo4 are for a habitat? What is your use case? Is your alternator the only charging source you are planning to use?

The alternator is the secondary charger, in case there is not enough sunlight.

 

[charlesrg]

10-40V… then the signal off of K11 pin 87A should work fine as engine sense.

Thank you, will work on this.

yes you can use surplus alt power when the service batteries are fully charged, but thats the problem, knowing the batts are full, and if you are still running four of the 6T batts, that can take quite a while to accomplish. Using an engine start signal as the trigger for the secondary charge controller does not take this into account, and you could be piling onto an already full alternator…

Looks like I should setup my Battery to Battery charger Low Voltage setting to 27.6Volts (Lead Acid Float voltage) this way the vehicle batteries are charged and then will be time to move power to the LiFePo4.

 

[Keith Knight]

Ok so I’m definitely stepping into some deep crap by posting this but it’s all about getting real world information out there.
My vehicle is a 2003 1079A1 I’m running 2 of these charging my house batteries while the engine is running. Also have Gen 2 air conditioner.
I also have 1,300 watts of solar while driving in favorable conditions which is also on Victron that can charge the truck batteries. I’ve driven over 14,000 miles in the last year in all weather conditions and have had no trouble. I worry about my alternator failing but haven’t seen any signs to really worry me. Open for comments.

 

[GeneralDisorder]

I looked at Victron, and I didn't like the enclosure not being water resistant , the lack of control features and the small current output. I should get 27Amps of one device and the goal is to add 2 for about 50Amps total. They will be installed inside the battery box. The price is also more attractive than the Victrons.

I looked at the Victron Buck Boost as well, but the device even had a fan to keep it cool, did not look like a device that could be exposed to the elements.

That "thing" you pictured though - it's all over AliExpress and some listings say 600 watts, some say 800 watts, and some say 1200 watts..... I would be afraid it wouldn't perform to the ratings or cause other problems like spontaneous conflagration.

Also - why not just put the Victron inside the habitat? I don't see the need to put it inside the battery box.

 

[Ronmar]

Looks like I should setup my Battery to Battery charger Low Voltage setting to 27.6Volts (Lead Acid Float voltage) this way the vehicle batteries are charged and then will be time to move power to the LiFePo4.

unfortunately alternators don’t work like that... they are a constant voltage power supply and dont know nothing about battery float voltage. Being a constant voltage supply, all they know is to make rated voltage until the load is so great they are unable to maintain that. I have actually load tested my 100A alt. At idle with a 100A pile across 24v at the battery i measured 13.8/27.6. At half throttle(1600-1800RPM) with the load still applied I get 13.9/28VDC… I have no 12v load on the alt. It is connected to the middle of my pair of group31’s but I derive all the truck 12v with a 24-12 converter.

using that voltage as a trigger will not insure the service batteries are done taking all the alts output…

 

[Ronmar]

Ok so I’m definitely stepping into some deep crap by posting this but it’s all about getting real world information out there. View attachment 913078
My vehicle is a 2003 1079A1 I’m running 2 of these charging my house batteries while the engine is running. Also have Gen 2 air conditioner.
I also have 1,300 watts of solar while driving in favorable conditions which is also on Victron that can charge the truck batteries. I’ve driven over 14,000 miles in the last year in all weather conditions and have had no trouble. I worry about my alternator failing but haven’t seen any signs to really worry me. Open for comments.

Dammit Keith! The solar is probably keeping the batts in a good place, so your alt has nothing better to do as soon as you start up, so the added load is probably not a big deal.

 

[charlesrg]

Ok so I’m definitely stepping into some deep crap by posting this but it’s all about getting real world information out there. View attachment 913078
My vehicle is a 2003 1079A1 I’m running 2 of these charging my house batteries while the engine is running. Also have Gen 2 air conditioner.
I also have 1,300 watts of solar while driving in favorable conditions which is also on Victron that can charge the truck batteries. I’ve driven over 14,000 miles in the last year in all weather conditions and have had no trouble. I worry about my alternator failing but haven’t seen any signs to really worry me. Open for comments.

Thank you. Real world experience is worth a lot of opinions.

 

[GeneralDisorder]

Thank you. Real world experience is worth a lot of opinions.

It's "experience" but without data. He has 1300 watts of solar that's continually charging his batteries. He hasn't presented any data on how often or how much charging the Victron's are even doing - how many amps have they pulled from the alternator?

Notwithstanding the amazing statistical sampling of ONE truck with no actual usage data - the numbers don't lie - the 100a alt is not up to this challenge. That's why the military entirely got rid of the 100a alternators even without any LiFePo4 batteries and chargers. They sucked for the application. Hell even all the HMMWV's have 200a alts now and those only have two 6TL batteries.

 

[charlesrg]

It's "experience" but without data. He has 1300 watts of solar that's continually charging his batteries. He hasn't presented any data on how often or how much charging the Victron's are even doing - how many amps have they pulled from the alternator?

Notwithstanding the amazing statistical sampling of ONE truck with no actual usage data - the numbers don't lie - the 100a alt is not up to this challenge. That's why the military entirely got rid of the 100a alternators even without any LiFePo4 batteries and chargers. They sucked for the application. Hell even all the HMMWV's have 200a alts now and those only have two 6TL batteries.

Are you running on the 260A alternator or aftermarket retrofit ?