What do you use?

[arizau]

In the recent past I've seen mention of 2 or more people who use 12V solar panel chargers to supplement their run time while operating recirc pumps/electric drywashers, etc. in the field. I'm locked in on the batteries I have but they limit me to about 3 hours of run time for my bilge pump. I'm interested in what you use and about how much extension of run time you gain by using one.

 

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[Capt Nemo]

I run with a pair of the Coleman 55W solar kits. Each kit is 3x 18W panels, stand, and charge controller. It also comes with a 200-300W inverter and accessory adapters, but I don't use that. I now have 4 of the kits as I wanted at least 200W for the Alaska trip.

Recently added a Thunderbolt 500W charge controller, and found that the load switch doesn't work. It is nice as it shows charging current, battery voltage, and load current.

The Thunderbolt solar kit looks nicer than the Coleman, and has twice the rating with 4x 25W panels. For me, the panels were just too large to fit the cargo box. I still might buy one to try out.

 

[slink]

I just use a large heavy deep cycle battery.(when I run bilge pump) I have a couple of renogy 100w panels and a couple sets of the harbor freight panels. I never take solar with me because I have no need to field charge. I can offer opinions on the differences between the renogy panels vs the harbor freight panels I own though. The renogy panels were cheaper per watt perform better on overcast days. Also its 1 panel @ 100w so the panel is a little larger but lighter than the harbor freight 3 pc 45w sets I have. I don't have any knowledge of the newer harbor freight sets mine are older. 1 advantage To the multi panel kits if something happens and a panel gets broke your not shut down remove broken panel and let the remaining panels do what they do. The renogy panel gets broke you are done charging. No doubt beach and desert prospectors can make better use of solar than those of us on the creeks covered by trees.

 

[Capt Nemo]

I've also gone from the big boat anchor to a smaller and lighter weight AGM battery. The smaller size and Amp/hour recharges quicker than a big battery. I can get a 20-25 bucket run before the battery is down to 12.2V, that's about as much as my recirc tank can handle with the sand spill from the buckets. 20 min later, the battery is back to 14V, and I have everything cleaned and ready to go again. You'll love it when you have soft sand to trudge through.

 

[arizau]

I use LFP (LiFePo4) batteries. Mine weigh around 2+ lbs. and will fit in coat pocket. The larger of the 2 is 9.6ah and my pump draws a little less than 5amp so about 2 hours run time...bummer since my dry washer can run about 5 hours on that battery. There is no amp drop with LFP until they are fully discharged so pumps and motors run full speed all of the time until then.

As an after thought: I wonder if the pump will operate if a rheostat or motor controller is used to reduce the current draw. Maybe that could be a way to adjust the water flow rather than using a valve and gain me some extra run time (?).

 

[Capt Nemo]

Lower RPM's increase the torque which increases Amperage. At motor start torque is high, and so is current. That's why you need motor rated fuses instead of fast blow. A 5A motor can draw 15A at start, but as it gets up to speed, the current will drop back to 5A.

 

[slink]

You are stuck once you are used to traveling that light ……

 

[IMAUDIGGER]

Also restricting the outflow a little causes a centrifugal pump to slip or cavitate, which lessens the demand on the motor...at least that's what Keene Engineering says about their dredge pumps. Less water but also less demand on the power source. Kind of counter intuitive, you would think the power demand would increase as you restrict the outflow.


Not sure if you would get more run time doing that with an electric bilge pump. Might be worth experimenting with. I'd also look for a brushless motor if anybody makes something like that. They seem to waste less energy.

 

[arizau]

Thanks but I don't think that will work with a bilge pump since they are not positive flow like I think a centrifugal pump is. The GPH goes down significantly the higher the lift or "head" with a bilge pump. At just 3 ft of lift a 1500 GPH rated pump reduces to about 1200 GPH and at 6.7' it reduces to 680 GPH!

 

[arizau]

Lower RPM's increase the torque which increases Amperage. At motor start torque is high, and so is current. That's why you need motor rated fuses instead of fast blow. A 5A motor can draw 15A at start, but as it gets up to speed, the current will drop back to 5A.

From what I have read, a motor controller will pretty much eliminate the startup spike since the rpms gradually ramp up from zero or that is how I understand it.

Found this too. https://www.instructables.com/lesson/Controlling-Motor-Speed/

 

[arizau]

Back to solar chargers. I found this chart and about halfway down it gets to equivalent watts to amps for 12v dc. https://www.inchcalculator.com/watts-to-amps-calculator/. The way I understand it is if a solar panel is working at 100% efficiency then a panel rated at 60 watts will supply 5 amps which is about what my pump draws. Anything less than peak efficiency (poor sunlight condition, etc.) or by using a lower rated panel will proportionally supplement the run time when the panel is connected in parallel to the battery. That kind of answers my question but I am still unsure if the way I understand it is correct. Most of the portable units I have seen online have protections built in to protect the panel and the battery as well as for personal safety...those are what I am concerned with.

 

[slink]

Another factor comes into play when speaking of solar efficiency. The charge controller its self will cause some loss. PWM charge controllers are very affordable and come included with many solar sets but are less efficient than the expensive MPPT controllers. A PWM would certainly be a better choice for a field use system just due to cost. MPPT is worth the extra money if its your home or a camper but not a good choice for field use. ALWAYS use a charge controller NEVER hook a solar set up directly to a battery.

 

[Capt Nemo]

The only time you can get away with direct hook-up is with panels under 5 W.