View Full Version : Hydraulic System functionality question when in -15 below F weather

02-20-2015, 06:42 AM
I need to try and get my rig ready to go south in a week and the temps around here are in the 0 to -15 F range at the moment. My 6Volt deep cell batteries are nice and toasty warm in the S&B house. The problem is that the hydraulics do not want to move on AC power only. They momentarily pump and then kick-off as if a current overload has been sensed by a breaker and then it pumps again after a few seconds momentarily again.
Is their a temperature below which I cannot move the hydraulics without externally warming the tank and pump?
Does the AC power source (I am connected to my S&B house AC with a 30amp connection) and 12VDC converter not supply enough power to run the hydraulics without the battery reserve capacity attached to the cct in the cold?

I am so bloody sick of this dang cold winter. :mad: Only 2 more winters till retirement

02-20-2015, 08:21 AM
If there's a 4-5 second delay after each attempt to start, you may just have a weak 12V DC mini-circuit breaker (pictured below). In cold weather, the pump may draw more power because of viscosity changes in the fluid at low temps. Running off the Power Converter with batteries removed may also be contributing.

I'd suggest getting a new 50 amp 12V DC auto-reset circuit breaker. They're about $10 at most auto parts stores and probably every marine parts store. Get one with a matching form factor so it fits on the buss bar.

If the problem persists with batteries installed, take 15 minutes to replace the breaker - shore power disconnected and battery cutoff OFF. If everything's ok with batteries installed, you'll have a spare that'll come in handy one day.

The buss bar shown below is located near the batteries. Your breaker layout may be different, but you're looking for one of the thick wires. The thick wire on top that has a thick wire on the bottom terminal is to the Power Converter. The other is to the pump.

02-20-2015, 08:21 AM
Hydraulic and lubricating fluids have practical limits that dictate the acceptable operating temperature range of the assets in which they are used. When assets are used in extremely cold conditions, they lose stability and can experience conditional failures. Hydraulics work in all weather. Even extreme cold. However they must be treated with arctic blended fluids prior to the cold weather. Extremely low temperature causes fluids to congeal, which means that it cannot flow through mechanical systems efficiently. This fluid immobility can starve a pump, which causes potentially harmful vaporous cavitation in the system. Since you probably didn't treat your fluid then the next best thing would be to try to heat up the fluid. Best way would be to heat it from the tank reservoir. You could try hooking up the batteries and maybe that will give you enough power but I suspect it will not be enough due to the extreme cold weather. Good luck!

02-20-2015, 08:22 AM
I won't say this is the definitive answer but I think you're right that the converter/charger is struggling to supply enough amps to the pump when it can barely turn.
Warming the tank and pump is the right idea but the fluid in the lines and the "closed" side of the hydraulic cylinders is still going to be subzero. You have the possibility of creating a leak or worse by trying to force fluid through them.
You could hang some heavy plastic around the rig as skirting and set up a salamander type heater to warm the underside. Run the furnace to raise the temp on the inside too. You'll increase your chances of success and reduce your chances of damage.
I'm sure this isn't what you wanted to hear but even 10wt oil gets pretty thick in those temps.

02-20-2015, 08:25 AM
I've operated my hydraulics pump at -2 (F) without problem.

02-20-2015, 10:12 AM
Without batteries?
I've operated my hydraulics pump at -2 (F) without problem.

02-20-2015, 10:41 AM
Try it with the batteries hooked up. Bet it will solve the problem.

02-20-2015, 11:40 AM
Put the batteries in. The pump motor is drawing more current than the converter can supply. The fluid is automatic transmission fluid. It will flow at low temperatures.

02-20-2015, 12:02 PM
Try putting an electric heater in the compartment with the hydraulic pump and fluid.Let it warm up real good and give it a try.

02-21-2015, 04:15 PM
Thank you for the suggestions. I will top up the charge in my batteries and try the hydraulics with them installed

02-22-2015, 04:10 PM
We were in the process of moving our stuff from our old trailer to the new one and while moving batteries I had flipped off the battery disconnect switch. Forgot to flip back and tried the slides and omly one partially worked. Thought we had a problem then I remembered to turn the battery disconnect back on and the slides worked perfectly. Doug

02-23-2015, 10:36 AM
I don't know what the amperage draw is on your hydraulic motor but I would guess it's more than your converter can handle without battery assistance. I would suggest installing the batteries first and trying it. Long as the batteries have a charge they won't freeze so the cold isn't going to hurt them. If you let the batteries go dead they will freeze so make sure you maintain a charge on them.

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02-23-2015, 06:09 PM
Although the ATF may work when cold I don't see a reason to not change the oil to multi-weight oil with a 0w rating. The hydraulics on a RV work so intermittently there are many choices of hydraulic fluids and engine oils that would be fine.
I would put 0w-10 synthetic engine oil in the hyd system and not ever worry about it again.