Too cheap to buy a Large DC ammeter

Geo-TH,In

Well-known Member
I figured out a way to estimate the current my dump trailer hydraulics uses. The + cable going from the battery to the pump is about 2 ft long, appears to be 6g copper. I decided to use the 2 ft cable as a shunt. Under load I measured 240 mv drop across the 2 ft cable. To my surprise I also measured 240 mv when dump bed was empty and it's on it way down.

I used my old 12v manual charger with ammeter. I connected the negative to the negative of the battery and the + of the charger to the end of the 2 ft cable that attaches to the solenoid. The charger pushed 6 amps through the 2 ft cable and 6 amps produced a 10 mv drop in the 2 ft cable. If I did the math correctly, that means 24x6 = (about) 144 amps will produce a 240 mv drop in the cable. The reason I say about is I have no way of knowing the accuracy of my ammeter on the charger or the accuracy of the voltmeter.

Now I know the ball park current my dump trailer uses, 144 amps. It takes 70 seconds to raise the bed and 50 seconds to lower it, 120 seconds, 2 minutes.

I'm lucky to get 30 months out of a marine battery. I've replaced 2 of them so far. I'm seriously thinking the marine battery isn't the right battery to use in a dump trailer that draws that much current for two minutes at a time. If the marine battery better, then why don't we use marine batteries in cars that have a cranking current close to 144 amps?

BYW, I removed two 5 year old batteries, one from my car and one from my truck and am using them in the dump trailer. The other day I made 6 dumps without charging the battery and they worked flawlessly without a struggle.

Worst case, I'll damage two old batteries.
geo
 
Dunno where you are going with this, so now you "know" the Amp draw, what are you going to do about it???
 
I'm thinking 144 amps is way more than a marine battery can handle based on their short life, 30 months.

Marine batteries are designed for small currents over a very long period of time, like powering a trolling motor.

The first battery that came in my dump trailer could do 10 dumps, 20 minutes before the battery was drained.

So I'll use two car batteries in my dump trailer. Be interesting to see how long they last considering they are already 5 years old.
 
David, I'm still cheap. Besides the $10 ones use a shunt. I wasn't sure how man amps I was going to find and what size to order. So I figured the 2 ft cable can act as a shunt. I didn't have to install anything or wait on the slow boat from China where most of the cheapies on ebay come from. And I was only concerned about getting an estimated ball park amps.

I was surprised it was that many amps it draws. More surprised the amps were the same lifting a load 3 ton load or lowering an empty bed.
geo
 

Something is flawed the amperage to lift a 3 ton load will be higher than lowering it with no load. Using it 10 times a day with no way to recover the charge more than likely will bring any common automotive/marine battery to its knees.

You need more battery/storage are at least two battery's that's a lot of work with very little time to recover... It is the price you pay for electric over hydraulics.
 
Well that doesn't sound right. It should show more lifting the load or you are getting something from nothing?????
 
hobo,
That's what I thought too. It doesn't seem logical that the lifting amps is
the same as the lowering amps. Bring your large DC meter over and see for
yourself. I wish I could find an old carbon load tester someone wants to get
rid of. I would love to have the 500 or 1000 amp dc meter. BUT I'M TOO CHEAP
TO BUY ONE.

Been researching marine batteries. I convinced the marine battery isn't the
best match for a dump trailer. Marine batteries reserve capacity are at 25 amp
drain, not 144 amps. Not to mention, the last two marine batteries have only
lasted me 30 months and battery was only good for 10 dumps. My old car
batteries are 5 years old and still healthy.

Be interesting to see how long my old batteries will last. I use my dump
trailer a lot moving dirt and mulch.

International hydraulics claim their pump will draw 250 amps under max load.

BTW, I've learned a neat way to load 3 ton mulch on my 10k dump trailer, make
it easier to dump, easy to keep the tarp from flopping in the wind, and
extremely well balanced behind the truck with proper tongue weight. I center
the pile of mulch over the axles. The mulch pile will just touch the front and
back of the trailer. The big pile keeps the tarp tight on trailer. Empty,
dump trailer is 1.5 ton. So total, I'm pulling 7.5k on a 10k trailer.
 
I agree, it was a surprise to me too. Bring your meter over and see for yourself. I know, it defies all logic
 
Here's my latest experiment with cheap battery power. Walmart started carrying a brand called "Value Power" in a few of the most common sized and priced them about 1/2 of regular car batteries. I bought two pretty large ones, group 65, for around $48 each. I'm going to use them for my winch, paralleled if necessary. Also for my 24 Volt military vehicle, in series. And additionally for general move-around utility jump use. They are distributed by Johnson Controls but only warranted for one year as opposed to multiple years for regular-priced batteries. Since I haven't used them to failure yet only time will tell but so far they seem pretty good.

<img src = http://s19.postimg.org/8s210l41f/Batt_Group65.jpg>
 
your setup must be different from mine. Mine runs the pump to dump but only opens a solenoid controlled valve to lower. The solenoid only takes a small amount of current to operate.
 
250 amps under max load

Yes I can see that... That's during the hole event also. I went with two battery's on the set up I have. I pull off the truck battery and have stalled the engine with one battery the voltage dropped so low. I only run into that picking up the front of a 3/4 are 1 ton truck with a big engine.

I could justify it cuzz if it won't jump off a car it gets towed :wink:
No doubt 2 bats have extended the pump motors life also.
 
I like Rural king 60 month 650 cca battery with one year free replacement. Someone suggested I usr my old truck battery and put new battery in truck. The I discovered my car battery was a few months older. Ended up using old batteries in trailer. Glad I did. Two car batteries was cheaper than a marine battery than only has a 12 month warranty.
 

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