Dual alternator, Lithium battery/AC setup (no generator needed) - Page 3 - Ford Transit USA Forum
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post #21 of 81 (permalink) Old 04-27-2019, 07:33:PM
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Keep up how, like instantaneously while driving?

I’m curious why you went with 9,200 BTU/hr A/C when the 11,000 Power Saver requires less current. Coleman really needs to manufacture a Power Saver versión of 9,200 BTU/hr air conditioner. At 2/3 the size of a 13,500 Power Saver, they could get power requirement for a 9,000 BTU/hr A/C down to 700 ~750 Watts. I’d jump on that if it were available.
Yes. While driving. I haven't tested yet but (I don't trust my battery meter) according to my meter the AC unit draws around 80-90 amps from the batteries but alternator charge shows as 30 amps.

......
I am doing a conversion and have installed a mach 8 as well. Was hoping ro run it via a 2800 watt magnum pure sine inverter powered by a combination of the high output alternater/transit batteries (engine idling) powering a 120 amp sterling batt to batt charger and 3 or 4 grp 31 AGMs (3-400 AH AGM).

How have you connected your transit power to your house power and do you have the high output alternator/dual starting batts?

The 30A from the transit seems way low. If that is all I will get my scheme wont work.... I am counting on upwards of 100 A from the transit.

FWIW, I measured the mach 8 pulling 11.4A AC on high (10.7 on low) while plugged into an extension cord. Converting to DC A going into the inverter by multiplying by 11 yeilds 125A DC expected on high cool (118Avon low cool). Not the 90A you reported.

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post #22 of 81 (permalink) Old 04-27-2019, 11:03:PM
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I am doing a conversion and have installed a mach 8 as well. Was hoping ro run it via a 2800 watt magnum pure sine inverter powered by a combination of the high output alternater/transit batteries (engine idling) powering a 120 amp sterling batt to batt charger and 3 or 4 grp 31 AGMs (3-400 AH AGM).

How have you connected your transit power to your house power and do you have the high output alternator/dual starting batts?

The 30A from the transit seems way low. If that is all I will get my scheme wont work.... I am counting on upwards of 100 A from the transit.

FWIW, I measured the mach 8 pulling 11.4A AC on high (10.7 on low) while plugged into an extension cord. Converting to DC A going into the inverter by multiplying by 11 yeilds 125A DC expected on high cool (118Avon low cool). Not the 90A you reported.
I know the numbers don't seem correct. I had a conversion shop wire everything and they used a smart charger that is supposed to protect the alternator from burning out. I need to go through the wiring and verify that the shunt is correctly wired. but the van is in another shop getting the water heater heat exchanger hooked to the engine coolant lines. I'm old enough to hire a younger man to do that work. I might be that the Victron meter is set up incorrectly.
I can't try to fix everything at once. I have to have our family fun (road trips) in between.

I'm not saying that I'm charging and discharging at the same time. I haven't taken any readings with engine on and AC running. What I'm saying is that the AC uses more power from the batteries than the vehicle supplies.

Last edited by Campervan Man; 04-28-2019 at 07:09:PM. Reason: address Sportcoupe
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post #23 of 81 (permalink) Old 04-28-2019, 07:52:AM
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Yes. While driving. I haven't tested yet but (I don't trust my battery meter) according to my meter the AC unit draws around 80-90 amps from the batteries but alternator charge shows as 30 amps.
You can't discharge and charge a battery at the same time. What may be happening is the alternator is supplying the 80-90 amps direct to the air con. You haven't measured what the van is using running. The "extra" from the alternator is charging the battery at 30 amps.

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post #24 of 81 (permalink) Old 04-28-2019, 10:31:AM
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You can't discharge and charge a battery at the same time. What may be happening is the alternator is supplying the 80-90 amps direct to the air con. You haven't measured what the van is using running. The "extra" from the alternator is charging the battery at 30 amps.

I interpret it a little differently. If wired from vehicle alternator/battery to house battery, and then house battery feeds inverter which then powers the roof A/C, it sounds to me like he’s measuring 30 Amps going from vehicle to house battery, but 80~90 Amps from house battery to inverter. The difference of 50~60 Amps is being made up by the house batteries.

The 80~90 Amps sounds plausible if day isn’t too hot and inverter is efficient. The problem is that 30 Amps from vehicle to house isn’t even close. You’d want to design for at least 100 Amps in order to run A/C continuously without draining house batteries. This is where the 2020 dual 250 Amp alternator option should make it easier and cheaper. I hope.
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post #25 of 81 (permalink) Old 04-28-2019, 10:40:AM
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I interpret it a little differently. If wired from vehicle alternator/battery to house battery, and then house battery feeds inverter which then powers the roof A/C, it sounds to me like he’s measuring 30 Amps going from vehicle to house battery, but 80~90 Amps from house battery to inverter. The difference of 50~60 Amps is being made up by the house batteries.

The 80~90 Amps sounds plausible if day isn’t too hot and inverter is efficient. The problem is that 30 Amps from vehicle to house isn’t even close. You’d want to design for at least 100 Amps in order to run A/C continuously without draining house batteries. This is where the 2020 dual 250 Amp alternator option should make it easier and cheaper. I hope.
Without seeing exactly how it's all wired I can only speculate. It is impossible to both charge and discharge a battery at the same time.

If house battery is indeed under load and supplying 50-60 amps (and not charging), it will have a measurable voltage drop from being under load. What is the voltage of the house battery while the a/c is on and driving?

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post #26 of 81 (permalink) Old 04-28-2019, 10:54:AM
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Yes. While driving. I haven't tested yet but (I don't trust my battery meter) according to my meter the AC unit draws around 80-90 amps from the batteries but alternator charge shows as 30 amps.

Mach 8 Plus - Cub

Cool/Heat Capacity: 9,200
Electrical Rating: 115 VAC, 60HZ
Cooling Amps-High: 11.7
Running Watts Standard: 1270
EXTERIOR SHROUD
Height: 8.25” Width: 28.40” Length: 41.10”


Mach 3 P.S. (PowerSaver)
Cool/Heat Capacity: 13,500
Electric Heat Element Capacity: 5,600
Electrical Rating: 115 VAC, 60HZ
Cooling Amps-High: 10
Running Watts Standard: 1075
Exterior Shroud
Height 13.8 Width 26.1 Length 38.0


Low profile was more important than power requirements (call me vain).
I completely understand wanting an air conditioner that adds as little height as practical, particularly on these tall vans. The extra 5-1/2 inches could affect where the van can go, which also affects function.

For what it’s worth, Airxcel announced last year that they were adding two new Power Saver air conditioners. So far I haven’t seen any specs or mention of them, even on their own site.

One is a Medium Profile 15,000 BTU/hr unit (too large for most vans) and the other an 11,000 BTU/hr unit based on Low Profile Mach 10.

The Mach 10 has the same smaller footprint as the Medium Profile, but is 2 inches lower at 11.8 inches.

As mentioned before, I’d like to see an even smaller Power Saver in the 8,000 ~ 9,000 BTU/hr capacity range. There should be a market for such an A/C not only for vans, but also for motorhomes to add a second A/C in bedroom and run off same 30-Amp service and 4,000 Watt Onan.
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post #27 of 81 (permalink) Old 04-28-2019, 11:42:AM
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This is why a second alternator would be so perfect. I could run the air conditioner whenever needed and when the batteries are drained just idle for a few hours, which I can't do with a diesel engine.
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post #28 of 81 (permalink) Old 04-29-2019, 10:47:AM
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I know the numbers don't seem correct. I had a conversion shop wire everything and they used a smart charger that is supposed to protect the alternator from burning out. I need to go through the wiring and verify that the shunt is correctly wired. but the van is in another shop getting the water heater heat exchanger hooked to the engine coolant lines. I'm old enough to hire a younger man to do that work. I might be that the Victron meter is set up incorrectly.
I can't try to fix everything at once. I have to have our family fun (road trips) in between.

I'm not saying that I'm charging and discharging at the same time. I haven't taken any readings with engine on and AC running. What I'm saying is that the AC uses more power from the batteries than the vehicle supplies.

Could you tell us what batt-to-batt charger you are using?

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post #29 of 81 (permalink) Old 04-29-2019, 11:03:AM
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Yes. While driving. I haven't tested yet but (I don't trust my battery meter) according to my meter the AC unit draws around 80-90 amps from the batteries but alternator charge shows as 30 amps.
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I'm not saying that I'm charging and discharging at the same time. I haven't taken any readings with engine on and AC running. What I'm saying is that the AC uses more power from the batteries than the vehicle supplies.
By your first post I assumed the engine was on because you stated "while driving" and "alternator charge". Your second post stated engine not running.

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post #30 of 81 (permalink) Old 04-29-2019, 11:28:AM
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He was just answering my question on whether he wanted alternator to keep up while driving.
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