# Gold Miner In Need Of Help

Registered Users Posts: 3
First post so be easy on me. I am a gold miner here in Arizona where water is in short supply. I run a recirculating system where I recover gold. I use a Johnson 4000GPH pump that has a amp draw of 15.5 amps. Currently I will be using four 12 volt Deep Cycle battery's made by Trojan as these were given to me from a newly wrecked golf cart that Insurance Adjuster totaled.

Typically I will be in the field for 10 hours before heading back home, but I would like to go on extended weekend trips. I understand that winter months and summers months are going to effect the efficiency charging time and harvest. The run time of the sluice / pump could be as much as 8 hours per day. Its important that the pump delivers the needed GPH due to keeping the water flow an 1 inch deep in the sluice box and order to recover the gold.

I know this is going to be a loaded question. If I rotate the batteries while the system is in use and run the batteries to 50% of their their capacity how big of a solar system would I need to keep the pump running on 1 battery while charging the other batteries? Also how long could I expect to run my pump using a 100AH battery down to 50%? or can I go below 50%?

• Banned Posts: 17,615 ✭✭✭
Re: Gold Miner In Need Of Help

Welcome to the forum.

The pump draws 15.5 Amps at what Voltage?
Using basic math (no losses) if that's at 120 VAC then the draw from 12 VDC is 155 Amps. A set of golf cart batteries is around 220 Amp hours - the load will 'flatten' them instantly.

If you take these batteries below the 50% level two things happen: one is the lifespan is shortened, regardless of how/when they are recharged, and the other is the current for a given load goes up exponentially as the Voltage drops. That means the fall-off in real capacity increases rapidly, so the amount of actual power you have goes down faster the further you discharge. It is not linear.

Frankly the chances of four GC2's doing anything towards running a 4,000 GPH pump are near nil. They probably won't even start it. You need a generator or even better a gasoline driven pump.
• Solar Expert Posts: 3,208 ✭✭✭✭
Re: Gold Miner In Need Of Help

Did Google " Johnson 4000GPH pump ". The result is for a Bilge Pump. If that IS the pump in question, then the load is at 12VDC (probably - did not see any spec on the pump in a quick skim of results), would expect that this pump is intended for very intermittent run-cycles.

You will probably be best served in looking for a heavy duty pump, intended for continuous use.

There is probably a reason that many/most dredging/sluicing operations use gasoline engines, with all that comes with the use of that fuel.

Realize that this is not directly responding to the questions. FWIW. GOOD LUCK! Vic
Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
• Solar Expert Posts: 3,123 ✭✭✭✭
Re: Gold Miner In Need Of Help

There is no reason to rotate the batteries, unless the charging panels are going to be located far away from the pump site. Solar chargers work just fine connected to a battery which is also under load at the time.
But if the panels deliver less current than the load draws, then the batteries will still discharge, just more slowly.
SMA SB 3000, old BP panels.
• Registered Users Posts: 3
Re: Gold Miner In Need Of Help

Well I suppose I forgot to put DC. I did mention, "12 volt Deep Cycle battery's made by Trojan as these were given to me from a newly wrecked golf cart" My bad. Yes the batteries are 12VDC and yes the pump is a Johnson 4000GPH pump of which is an outstanding pump. The entire purpose is to be quiet as I hate hearing a generator or a trash pump, been there done that...

The Johnson 4000GPH pumps are and have been in use by gold miners for years with no issues of running them 24/7 if needed.

Lets assume I just use (1) 12VDC battery as seen below and the pump draws 12VDC @ 15A. This is provided that the pump is not necked down by a ball valve and running wide open. How many watts of solar panels do I need to run the pump and maintain the battery? Info. is on the battery.
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• Banned Posts: 17,615 ✭✭✭
Re: Gold Miner In Need Of Help

In that case you're in good shape!
Drawing 16 Amps from 225 Amp hours is only 7%, and only 3.5% with four of he batteries set up as parallel strings of two. It should not go below 50% SOC in an 8 hour day.

What you want to do is size any solar panels to be able to recharge it/run the pump as this will be happening concurrently. In other words the pump won't be shut down while you try to recharge the batteries.

So there we have a need for 15.5 Amps from the panels just to negate the pump demand. Then you need at least another 12 Amps for a single set of those batteries @ 5% charge rate minimum. 10% is better. Remember that the output from panels will not be 100% of their rating throughout the day, and your hours of good sun (panel production) will be less than the 8 working hours you want to run the pump.

We're at 27.5 Amps here for one set of batteries. This looks like a case of "max out a MidNite Kid 30 Amp MPPT controller with 468 Watts of PV" or there about. Can you manage a \$300 controller and a couple of 240 Watt panels?

If you want to use both battery sets at once you'd want a bigger charge controller and a lot more PV as you'd be after near 40 Amps (or more) and would require 616+ Watts.

Alternatives would be charge one set while draining the other:
22.5 Amps peak current for the set that's charging and 350-ish Watts to provide it.

As you can see there's room for flexibility in the design, and your budget and logistical considerations would have bearing on this.
Re: Gold Miner In Need Of Help

OK, we can give some estimates now...
• 4* 12 volt @ 100 AH batteries = 12 volts @ 400 AH storage.
• 15 Amp @ 12 volt pump
• 400 AH / 15 amps = 26.7 Hours
Now--The 100 AH capacity is at a C20 discharge rate (100 AH battery /20 hours = 5 amps for 20 hours for from 100% to 0% state of charge). Now ~27 hour discharge rate is "close enough" for our needs (battery will appear to have slightly more than 100 AH capacity when discharged at less than a 20 hour rate).

Normally, for an off grid application, I would be suggesting that you discharge ~25% per day (2 days of stored power, 50% maximum discharge for longer battery life). You could discharge to 50% every day--But you may have problems getting back to 100% charge because there are not enough hours in the day of sun (it would be close in the desert--you may have enough hours of sun per day--just barely--Basically 10% rate of charge, ~5 hours to recharge the battery and another 4+ hours of "absorb" or holding voltage at ~14.8 volts to get from ~85% State of charge to 100% state of charge).

Now, to keep a battery bank "happy", we recommend around 5% to 13% rate of charge, and for a daily/heavy cycling, you will really need a 10% to 13% rate of charge:
• 400 AH * 14.8 volts charging * 1/0.77 panel+controller eff * 0.05 rate of charge = 384 Watt array minimum
• 400 AH * 14.8 volts charging * 1/0.77 panel+controller eff * 0.10 rate of charge = 769 Watt array nominal
• 400 AH * 14.8 volts charging * 1/0.77 panel+controller eff * 0.13 rate of charge = 999 Watt array "cost effective maximum"
Next, based on how much you want to use the pump and hours of sun per day, using PV Watts for Flagstaff AZ, fixed array mounted at 35 degrees from horizontal (you can move the rack a few times a year to get a bit better power):
```Month    Solar Radiation (kWh/m 2/day)
1      5.19
2      5.92
3      6.27
4      6.44
5      6.56
6      6.61
7      5.95
8      5.54
9      6.59
10      6.19
11      5.47
12      5.07
Year      5.98
```

So, say a minimum of 5 hours of sun per day and assuming that you charge during the day and use power at night (all power is supplied by the battery bank, and all day time sun goes into charging) and you use 25% of the battery storage per day:
• 26.7 hours storage * 0.25 discharge per day = 6.675 hours per day usage
• You want to use 8 hours per day (still will probably be fine on your 100 AH)
• 15 amps * 14.8 volts charging * 8 hours of use * 1/0.77 panel+controller eff *1/0.80 battery charging eff * 1/5.0 hours of sun = 437 Watt array minimum
Now that is for 8 hours of pumping per "night". your application is probably going to be pumping during much of the daylight hours... That is going to help you a lot--The motor is going to draw a lot of its power directly from the solar array (no 80% battery efficiency issue), and the battery bank will not be discharged as deeply. However, 15 amps that was going to keep the battery bank "happy" during charging is now not available--So, ideally, you will want to account for that "loss" of charging energy:
• 15 amps * 14.8 volts charging * 1/0.77 panel+controller efficiency= 288 Watts from array direct to battery bank
• 384 Watt array minimum + 288 Watts to power pump = 672 Watt array minimum with day time pump load
• 769 Watt array nominal + 288 Watts to power pump = 1,057 Watt array nominal with day time pump load
• 999 Watt array nominal + 288 Watts to power pump = 1,287 Watt array cost effective maximum with day time pump load
So, I could see justifying a solar array of 672 to 1,287 Watts, with 1,057+ Watts being a "healthy sized array"--Plus, since you are using the pump during daylight hours, you could probably run camp lighting, radio, laptop computer, etc. at night with the "spare energy (remember, you only need ~437 Watts of the array to supply the actual pump load during "average" sun conditions in winter).

Obviously, there will be some times that you need to use a genset if you have more than 1-2 days of very dark/cloudy weather (or shut down/reduce your operation until sun returns). 400 AH battery bank with a ~45 amp 12 volt Iota charger + a Honda eu2000i (1,600 watt) genset or Yamaha equivalent inverter-generator would be fuel efficient and quiet backup power supply (when needed).

You will also need a hydrometer (this one from Midnite is well liked, rinse with distilled water after usage), a Battery Monitor (Victron another good brand), and a DC Current Clamp DMM, would all be handy.

Another off the wall suggestion--If you only pump during daylight hours, you can pump direct from solar with a Linear Current Booster:

http://www.solar-electric.com/dankoff-solar-pumps-controller-dsp200.html

Assuming:
• 15 amps * 12 volts * 1/0.77 panel derating * 1/0.80 LCB eff = 292 Watt array minimum
Since you will be pumping at other than the middle of the day, you can make the array larger to give you more hours a day of 15 amp @ 12 volt output. Using PV Watts for December, and the hourly data option, a 1,000 Watt array would look like:
1974, 12, 21, 08:00, 0
1974, 12, 21, 09:00, 139
1974, 12, 21, 10:00, 264
1974, 12, 21, 11:00, 450
1974, 12, 21, 12:00, 471
1974, 12, 21, 13:00, 449
1974, 12, 21, 14:00, 188
1974, 12, 21, 15:00, 188
1974, 12, 21, 16:00, 148
1974, 12, 21, 17:00, 4
1974, 12, 21, 18:00, 0

15amps * 12 volts = 180 watts

So, roughly, a 1,000 watt array on the shortest day of the year + LCB would (and 62% estimated efficiency) would give you 9:30 to 3:00pm pumping without any batteries (or solar charge controllers, etc.)... A possible option (batteries make the system very expensive, have to replace every ~3-5 years, etc.).

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Registered Users Posts: 3
Re: Gold Miner In Need Of Help

Personally I would prefer to have two batteries in parallel running the pump and two batteries being charged. Have the batteries in cart and its just the matter of switching the pump leads and charger leads to the other set of batteries.

Would this decrease the panels or size?

This is the trommel I built so I already have one gas engine in place, but looking at replacing it as well.
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• Banned Posts: 17,615 ✭✭✭
Re: Gold Miner In Need Of Help
Coues Deer wrote: »
Personally I would prefer to have two batteries in parallel running the pump and two batteries being charged. Have the batteries in cart and its just the matter of switching the pump leads and charger leads to the other set of batteries.

Would this decrease the panels or size?

Charge one set while using the other is fine. You only need enough panels to charge the one set of batteries. As outlined previously about 350-400 Watts. A couple of inexpensive 200-ish Watt GT panels and a MidNite Kid controller and you're good. Biggest downside is the batteries sit discharged overnight and you have to remember to switch the charge/pump wires. If you can find a DPDT switch that will handle 25 Amps you could just flip between 'A' and 'B'.
• Solar Expert Posts: 10,300 ✭✭✭✭
Re: Gold Miner In Need Of Help

i would be inclined to go with using all 4 batteries without separating them. a 15a load for 8hrs is 120ah of a 220ah battery bank and is more than 50% dod. there would be less strain on the batteries with all 4 as the capacity increases with a lowering of the load current. with pvs lower in price these days and batteries higher in price it makes sense to not have tp replace the batteries sooner and the extra \$ spent on pvs gives a bit more reassurance that during off times due to weather or season that you may still deliver a usable charge to the batteries. you should monitor the charge to and from the batteries regardless as stuff happens and solar is not foolproof to just set and forget.
• Banned Posts: 17,615 ✭✭✭
Re: Gold Miner In Need Of Help

I agree with Niel, unless the number/size/expense of panels is an issue. If the OP tries to run the pump & charge both sets at the same time with too little PV all that will happen is slowing down the rate at which the batteries die.
• Solar Expert Posts: 252 ✭✭
Re: Gold Miner In Need Of Help

I don't know, I read this stuff and the math works, but in real life....... You will still run your genset A LOT. I have 960W array running a couple of lights and a T.V. with a large battery bank. I still run the genny to charge about everyday. Granted it's only for an hour or so on sunny days, but even up here in the interior with long sunny summer days I couldn't get by without me Genny.. There are far more cloudy days in life than we think there are...

If you stuck my Yamaha behind a rock 20 yds away from your trommel I doubt one could hear the thing.
• Banned Posts: 17,615 ✭✭✭
Re: Gold Miner In Need Of Help
I don't know, I read this stuff and the math works, but in real life....... You will still run your genset A LOT. I have 960W array running a couple of lights and a T.V. with a large battery bank. I still run the genny to charge about everyday. Granted it's only for an hour or so on sunny days, but even up here in the interior with long sunny summer days I couldn't get by without me Genny.. There are far more cloudy days in life than we think there are...

If you stuck my Yamaha behind a rock 20 yds away from your trommel I doubt one could hear the thing.

Arizona is a lot different from Alaska.

But yes the inverter-generators are remarkably quiet and efficient power sources.

BTW your 960 Watt array is a good 400 Watts shy of what your 880 Amp hour 12 Volt bank should have.
• Solar Expert Posts: 252 ✭✭
Re: Gold Miner In Need Of Help
Arizona is a lot different from Alaska.

But yes the inverter-generators are remarkably quiet and efficient power sources.

BTW your 960 Watt array is a good 400 Watts shy of what your 880 Amp hour 12 Volt bank should have.

Yes I get that, I plan to add another 1KW to the array next summer...................... God Willing and The Creek Don't Rise.