goldneagle
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50 AMP output at 12 volts should be enough to recharge a 4 battery bank. 60 AMP alternators already do it on most of out trucks.I will be watching this thread.... 12V supply would work a lot easier for my M931/MK48 project's gauges.
Not really, since the batteries are in series each see 60A on a 2 battery 24V system. In a 4 battery 50A 12V system each would see 12.5A which isn't very much to replenish batteries, not in a short period of time anyway, we are talking MANY, MANY hours.50 AMP output at 12 volts should be enough to recharge a 4 battery bank. 60 AMP alternators already do it on most of out trucks.
Thanks for the correction. So I guess I will have to set up all the batteries in 24 Volt groups and use a battery equalizer or inverter to get 12 volts out for the camper.Not really, since the batteries are in series each see 60A on a 2 battery 24V system. In a 4 battery 50A 12V system each would see 12.5A which isn't very much to replenish batteries, not in a short period of time anyway, we are talking MANY, MANY hours.
I do appreciate your contribution to the conversation. I am still in the early stage of my build. I may have jumped the gun on getting the 400 AMP alternator. I was assuming it would only put as much resistance to the engine as demand rose. So if i was not pulling 400 amps it would not put the same demand on the engine as when it put out only 200 AMPS. Did the manufacturer have any documents as to demand in HP vs. AMP output?I am only trying to contribute to the conversation, but after speaking to the manufacturer I decided that a 60 amp is more than sufficient for my customers RV and my own power needs. As for the loss in hp, 30 hp is a lot! The guys here that are adding turbos to their Cummins 250 are only getting 20-30 hp out of that modification. Every hp counts in performance and fuel economy. Small changes to our trucks like a air operated fan, milled out front hubs or bobbing a axle of will bring a noticeable difference in the way our trucks perform.
You know what happens when you assume.. But in this case, you are assuming right. The resistance will be lower when drawing small loads and rise as demand rises. The 30+ HP draw is at max load.I was assuming it would only put as much resistance to the engine as demand rose. So if i was not pulling 400 amps it would not put the same demand on the engine as when it put out only 200 AMPS.
If I remember the spec's on it, it is supposed to put out over 200 AMP at idle speed. I think it was part of the requirement from the military that it could produce over 200 at idle so they could run the equipment in the HMMWV .You know what happens when you assume.. But in this case, you are assuming right. The resistance will be lower when drawing small loads and rise as demand rises. The 30+ HP draw is at max load.
Before we get crazy here with this alternator project, let me ask a question. What size alternator do i need to feed 4 batteries for starting and cab electronics and 6 deep cycle batteries for the Camper portion?Several things I have learned from heavy duty vehicle electrical equipment (on first responder hardware in this case, but physics doesn't change just because it's painted green).
1. If there's a one-way drive pulley on it, it's because the rotor of the alternator is so massive that full throttle up shifts result in the alternator shredding the drive belt as it slows down from ~13000 RPM to ~5000 RPM in the 500 milliseconds that the upshift takes. With the one way clutch, the alternator rotor can spin down independently of the engine and everybody is happy.
2. Cooling fan orientation and one-way clutch orientation must be changed to reverse-rotate an alternator. There might (but probably isn't) also be a need to change brush holder orientation.
3. The big problem with high amperage alternator is torque required at maximum charge at idle. Most belt drives can deliver enough power to run the alternator at maximum output above 5K rotor RPM, but turning that monster at 200A output at 2-3K rotor RPM is a killer, because the RPM is low, so the torque demand is higher than the belt can manage. That's why there are dual belts, wide multigroove belts, etc for these alternators. You'll note there are probably multiple alternator mounting brackets to lock the thing in place too - you need all of them - it will try to move around on you in a high load at idle situation. It will also try to destroy the bearings on any other belt powered accessory on the tension side of the belt between it and the crankshaft pulley.
4. 400A @ 28V is a lot of current and a lot of power. You WILL have to run big fat welding cable to the big loading points and you WILL need to put a fusible link in the output from the high power bus to the vehicle's existing bus, which is only rated for 60A or so. Cooling and ventilation will be an issue - both for the alternator and for electrical components (including batteries) that are absorbing that kind of power.
All of that said, it's a benign upgrade. Other than additional cooling fan load, it won't draw measurably more crankshaft HP than the existing alternator unless you're drawing that power to put it into a load somewhere. I would probably use a manual disconnect switch on the feed line running to the battery bank and maybe also a continuous-duty contactor as well wired into something that detects that the vehicle is probably moving, like a circuit running between the parking brake indicator light and the service brake light circuit (with appropriate diodes along the way) so that it tried to dump alternator power into the big battery bank only when the vehicle was actually moving.
Speed and load are not the same. If you draw 5 amps, it will pull less engine hp than 25 amps will. If you want to put it on your truck you are good. I don't however think you'll ever need that much power though.If I remember the spec's on it, it is supposed to put out over 200 AMP at idle speed. I think it was part of the requirement from the military that it could produce over 200 at idle so they could run the equipment in the HMMWV .
I wish I knew how much I need. I will have 4 starting batteries and up to 6 deep cycle batteries for the Camper. Any idea what size alternator would be right for that application? I can always sell the 400 AMP unit, and even makes some money on it, and buy a smaller one (once I know what size to get)Speed and load are not the same. If you draw 5 amps, it will pull less engine hp than 25 amps will. If you want to put it on your truck you are good. I don't however think you'll ever need that much power though.
The question can't be answered as it was asked - you left out the most important variable: time. Most batteries are happiest being charged at a c/10 rate (check the manual - your battery may vary). So if you have, say, 40 amp-hours of batteries and they're 50% discharged, the optimum charge would be a 4 amp rate for 5 hours plus the topping/equalizing charge (or just float at ~2.3V /cell if they're wet cells and you're not going to do it for days on end). A lot of the time, however, you don't want to wait for the optimum rate charge to complete, so you go to something like c/5 or c/2 to get the time down until the impressed voltage comes up to the regulated value, then the effective charge rate drops off as the battery approaches full charge. That's pretty much what you get when you do a constant-voltage charge like most vehicles do, and they get away with it because starting batteries are seldom more than 20% discharged. It does, however, cost battery life and charging efficiency to charge at faster than a c/10 rate.Before we get crazy here with this alternator project, let me ask a question. What size alternator do i need to feed 4 batteries for starting and cab electronics and 6 deep cycle batteries for the Camper portion?