Electric pump advice

Brian Miller

Be vewy vewy qwiet, I'm hunting Cutthwoat Twout
#31
A buddy of mine has an electric pump, though I don't know the brand or model. To save wear and tear on the pump, he initially inflates each bladder in his raft with the valve in the open position so it doesn't have to work as hard. The valve is closed after each bladder is fairly full and then each chamber is "topped off" with a hand pump.
There is a separate Halkey Roberts valve depressor that goes on the end of my LVM HR valve adapter.
 

Brian Miller

Be vewy vewy qwiet, I'm hunting Cutthwoat Twout
#32
You guys got my curiosity up. I went out to the shop and did some live testing on my LVM that's about 15 years old. Here's what I found:

Start current (initial surge) is too fast for my digital meter but it quickly drops to the running current with no air load which was 21.15A. When I put my hand over the air outlet and try to stop the flow completely the current drops down to 17.51A. I thought it would go up. I think there must be a relief valve for the air in the pump to prevent overheating when the air flow is obstructed (or the tubes are full). I can hear the pump speed increase when I do this which is what I'd expect a relief valve would do.

The voltage at the battery at the end of the original 10 ft power cable for these 3 situations was: 12.5 for motor off (no electrical load) - 11.6 running without an air load - and 11.6 when I try to stop the air flow with my hand. i.e. no change. I was using 2, fully charged 12 V deep cycles in parallel.

If it takes 10 minutes (I'll use 15 minutes worse case) to fill both of my 14 ft by 25 inch diameter tubes then I will have used up 4.375 ampere-hours of my battery capacity (17.51A times .25 hrs). I'd say most car batteries are at least 75 ampere hours capacity. Probably more like 200. So, if your battery is fully charged - as it probably is after driving to the river - then filling even 2 or 3 rafts should not really affect your ability to start your car at the end of the day. This agrees with Preston's conclusion above.

Heat generated by the motor is I (17.51A) times the voltage drop (11.6V) = 203.1 watts. That seems enough to heat that small motor up but it's designed with vents so air flows around the motor internally when its running. Also, at 17 to 20 amps the switch is possibly more likely to fail at higher operating temperatures. Running it in the shade on a hot day is probably a good idea. And if it gets noticeably hot (not just warm) to the touch, although mine never really has, I'd shut it off and let it cool down a while. It also confirms the advice to not run the vehicle engine while using the pump. The higher voltage (maybe 14 VDC) would add a lot to the amount of heat generated by the pump motor (now 245 watts). If it gets warm at 11.6 V I'm pretty sure that would overheat it under most conditions.

The curious thing is that if these measurements are correct the pump generates less heat (uses less current) when it's pumping air into the tubes than it does running with no resistance against the pump. I think they designed it that way with the relief valve spilling more air around the motor windings as the airflow into the raft decreases but maybe someone with more knowledge about DC motor air pumps can educate us on what's going on there.
It used to be that the charging system on automobiles put out about 14VDC (and change) to charge the battery. I recall my LVM docs say not to use the pump with the car motor running to avoid an overvoltage situation to the pump.
 

Alex MacDonald

that's His Lordship, to you.....
#34
Does anybody make a pump with a standard two-prong electrical plug setup? I'm asking because I have the Tacoma package with the outlet in the back of the truck bed, and I'm dying to use it for something:clown:
 
#36
Does anybody make a pump with a standard two-prong electrical plug setup? I'm asking because I have the Tacoma package with the outlet in the back of the truck bed, and I'm dying to use it for something:clown:
You could easily buy a 2 prong plug yourself and it would work. BUT, the pump uses 25 amps on startup and I'm sure the wires on your truck are at the most 12 guage and maybe only 14 guage...check the fuse for that outlet and it's probably only a 15 amp fuse. For a length over 12-15 feet you need 10 guage wire. I ran my own for my ranger pickup; about 18 feet and 10 guage wire. The problem is with 12-14 guage is that it will show 12 volts but it can't carry sufficient amperage. It will work for awile but will end up heating the motor up.
 

mk4

New Member
#37
If it takes 10 minutes (I'll use 15 minutes worse case) to fill both of my 14 ft by 25 inch diameter tubes then I will have used up 4.375 ampere-hours of my battery capacity (17.51A times .25 hrs). I'd say most car batteries are at least 75 ampere hours capacity. Probably more like 200.
Most automobile starting batteries don't have 75 AH. They only deliver a good amount of CA's, since that's what they're designed for. We're probably looking at 50 AH in a new top of the line battery. For a generic off of the shelf battery that's a year or so old, 30 AH is reasonable estimation.

The general rule of thumb is to never run down your battery to less than 50%. That means in a real world situation with an automobile starting battery, you're looking looking at roughly 15 AH before your battery won't be able to provide enough amps to start your car.

That's why I run an AGM group 27 as my main battery. More power.
 

Freestone

Not to be confused with freestoneangler
#38
Does anybody make a pump with a standard two-prong electrical plug setup? I'm asking because I have the Tacoma package with the outlet in the back of the truck bed, and I'm dying to use it for something:clown:
Alex, yes and they are really cheap and work well. I have had mine for years and it still works great. It is not powerful enough for a closed-valve fill but that's no big deal. I just found a used one at the Goodwill for $3.99 and bought if for a spare. I have an expensive Metro one too but I always just take this little one as it is so much easier to use and is really small. If you want to meet up when I come up to town tonight, I'll show it to you.
 

Alex MacDonald

that's His Lordship, to you.....
#39
Sounds great, Sue; I'll pm you.
Now didn't THAT sound tacky!! how about "I'll send you a PM"? You guys see what 35 years of political correctness will do to you???
 

Freestone

Not to be confused with freestoneangler
#40
LOL! Here is a link to the pump. It looks like a toy and I never expected it to last so long but it is still going strong years later. I open the valve to fill my tubes and it doesn't take to long to fill even my 13' cat tubes. There will be a noticeable pitch change when the motor can't fill it any further (about 95% full) so I immediately remove the pump, close the valve and top off by hand. And for $8.75, it is a bargain! I know I have gotten my money's worth out of mine.

http://www.amazon.com/Interdynamics-RFT-1-12-Volt-Raft-Inflator/dp/B000CO7QGA
 

mk4

New Member
#41
I have a MV-50 12V air compressor. A lot of offroaders use these as they are cheap and awesome for the price ($35). Their output for the price is great and they're long lasting too. Airs up all four of my 35's in about 10 mins. I haven't tried in on a boat, but I plan to.

Anyone else use these?
 

LCnSac

John or "LC"
#42
I have a Rule 12V on order from Amazon at about $73 so we'll see. For the smaller boats you can do some inflation at home--enough to cut time but to fit in the back of an SUV or throw on top for short trips. I use a 120V pump I got for around $10 at Walmart and it inflates my Renegade in about two minutes. It does need topping off with a hand pump.
 

Salmo_g

Well-Known Member
#44
I'd been using the foot pump that came with my Water Master until last month when I picked up a cheap electric pump at Cabela's for $15. Altho that was a sale price, I expect the quality is low, but a friend has one that has been in service for 2 or 3 years on his pontoon boat.

Sg
 

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