It's coming into the season when using the snow plow is pretty much an eventuality. I've noticed in the past that the hydraulic pump puts a pretty heavy draw on the electrical system. Would adding a fairly large capacitor bank to the system help or is having a third battery and/or a HO(220 amp) alternator the only practical way to go? I have the cap bank already, a battery would run around $100 and the HO alternator is close to $300...

The cap bank is six caps 2700 MFD, 400 vdc. I can easily change the configuration so they are series, parallel, or some combination. I think having all six in parallel would be the best way to go, but any input or discussion is, as always, welcome.

 

Boy I'm confuzed..... Is this something people routinely do to improve plow operation, cause I sure don't see how it would help except for one very brief power surge when you first activate the electrical load. After that the capacitors wouldn't recharge until the voltage was brought back up to your idle condition.

On the other hand, another battery sems to me would provide much more usable current much longer, and much heavier current, and then recharge during the extended period when the load is not active.

Granted, the capacitors could charge and discharge much faster than the battery - probably on the order of milliseconds, but raising, lowering or adjusting a plow would last a lot longer than that.


Having said this, I want to make it clear that I'm just speculating......

 

Hey be careful ,or we'll never hear from you again.

 

What you need is more power generation, not power storage.

A capacitor bank will hold power, but will discharge quickly. Get a better alternator is you need more power, or put a smaller pulley on your existing alternator to spin it faster.

 

Caps won't help you out, not much energy storage at 12V. They are only useful for short duration power needs, like a bass hit for a stereo amp. You need a higher output alternator, then MAYBE a 3rd battery.

 

<small>A=ampere, V=volt, C=coulomb, J=joule, m=meter, N=newton, s=second, W=watt</small>


2700 μF x 6 = 0.0162 F


0.0162 F = A*s/14.7


0.238 = A*s


so assuming 1 second, that's only 0.238 Amps or ~35 watts of power. Someone feel free to check my math, but it doesn't look like those capacitors will store enough power to be helpful for you.

 

Yep a capacitor won't help you in this situation... think of it this way:

warning: obsecure analogy approaching

Your car battery is like a swimming pool, and your alternator is like a garden hose constantly filling it up. The plow is like a fire hose drawing water from the pool, but only in short bursts. As long as the garden hose can keep the pool full between bursts, you should be ok. If you find that your battery is getting drained down, then you need a bigger alternator (larger garden hose) or another battery (another pool) to draw from.

As others have said, a capacitor is basically an extra tiny battery that can empty instantly upon demand. Good for instantaneous demand spikes but not useful for long draw demands like a plow or winch.

 

Run the hydraulic pump off a PTO?

There are some capacitors that can allow higher discharge times/current output. I can't remember what they're called but there are some unique power supplies that run off them. The theory is the same above garden hose/fire hose example. In the case of the power supply, the water hose can be pretty small in relation to the bursting fire hose. As long as the volume of water expelled by the fire hose is less than the volume able to be supplied by the water hose you're good. Where the capacitors come in is they can take higher charge current (and store it efficiently = faster rebound time) than a battery.

You would need to balance the wattage of draw of the plow pump (over the longest/hardest "cycle time" - say, lifting the plow in a snow pile) with the combined wattage of the alternator output, battery output, and the capacitor output. Then the supply current (from the alternator) over a period of time has to equal the amount of power taken out of the battery and capacitor. In this case, the alternator is your water hose and the battery, capacitor, and alternator (combined) are your fire hose. If your cycles are too frequent to where the alternator can't re-charge the battery and capacitor, or your current draw is more than you expect, then you will always have a weak link. You would have to bring up your alternator capacity to compensate.

If you can run the hydraulics off of the engine at all that would be the best route - direct power off the engine, no power conversions from mechanical to electrical and back to mechanical (through the hydraulics). You just go from mechanical to hydraulic (the direction of flow might just be directed by an electrohydraulic valve = very little current, or even a mechanical valve = no current needed).

 

well, i still think a second battery might help and here is why... when plowing, you probably plow a parking lot, which drains the battery a bit, then drive to another parking lot and repeat...

If a second battery gets you through a single parking lot (while running strobes and extra lights etc...), then you can recharge on your way to the next one, you might be able to get away without a bigger alternator.

If you are plowing a very large lot, like a mall, without down time, then a bigger alternator is your best solution (or a PTO as was mentioned in the previous post).

 

Batteries are only for starting the engine and electrical loads when the alternator isn't spinning. When the engine is running, the battery charges and becomes another load just like all the others. Adding another battery only increases the load on the running alternator(s). The solution is a bigger alternator.

 

Not true. The batteries source current as well when the alternator cannot provide enough and the voltage gets pulled down to the level of the battery. However, I do agree that a higher output alternator is needed. A better solution though would be a PTO hydraulic pump.

 

I would argue the opposite. The battery is there for power whenever you need it, the alternator keeps it charged. A winch can pull up to around 450 amps at full load... good luck finding an alternator that can keep up with that.

 

From an engineering point of view, a properly designed electrical system will not draw from the battery when the alternator is operating, except in the case of unanticipated transients or surges. A snow plow is not unanticipated, and hence it's power requirements should be designed into the spinning reserve capacity of the alternator. Of course we all know that the battery will "take up the slack" if system voltage is depressed to a point where the alternator is no longer keeping up. But doing so on a routine basis means the alternator is effectively undersized for that application and probably not long for the world. Beefing up the alternator is the "correct" solution from an electrical perspective. With a larger alternator you wouldn't even need to add a second battery (in a system that probably wasn't designed for one anyway).

 

There is a device called a charge regulator, charge controller, or voltage regulator, something to that affect (like pop and soda). The purpose is to prevent the battery from over charging. Thus, the batteries are not a constant load. Only while charging.

In small home-brew wind power systems they require the use of a "dummy load" or "dump load". What happens is batteries can only take so much voltage before they begin to break down. All batteries - starter batteries, deep cycle batteries (all wet cells), AGM's, SLA's, and the worst ones are the Lithiums. There could simply be a charge controller that turns off the flow in to the batteries, but in doing so it unloads the wind turbine. Without a load on the wind turbine it can over-speed and fly apart. Hence, the dummy load - when the batteries are no longer a sufficient load (max charge) the dummy load puts a draw on the turbine as a "brake".

Your truck doesn't have to worry about the alternator over-speeding as it is run off the engine. However, the same charge controlling still applies. Therefore the batteries are not a constant load. When you draw from the system a lot they are - directly because of the load you are running off the batteries, not because of the batteries themselves (if they are "good" batteries).

Deep cycle batteries are also a lot better at constant use than starter batteries are. Starters are meant for just that - starting an engine. They supply a "burst" of electricity, kind of like a capacitor, if you will. A deep cycle can take repeated discharge/charge cycles. Starters aren't meant for this - they are float charged once the engine is running and store enough current to start the engine the next time. They aren't meant to run loads.

Some people that run high power radios use battery banks (big stereo amps, high power two way radios, etc) to supply more current. Depending on the time between "runs" a high output alternator might be necessary. Or multiples.

If you run a PTO pump you don't have to worry about all the electrical crap.

 

I contradicted your first statement and your second agrees with me, but in a disagreeing manner. No need to explain the "engineering point of view" to me when it comes to electrical systems.