Power is the issue, as always

[murankar]

I have tossed this idea around a while back when I built the firs charge case. The idea of going solar for the field is creeping back in my head. I got a deep cycle battery in my van for the field but no way to charge it if I need more power while at the field. I could run a charge circuit off my main battery. This to me would be a great short term fix to the long term problem.

My deep cycle can handle 10 amps discharge for 10 hours, which to me means 80 AH. I am still not sure how my charge cycles on the packs I would get when adding in the power usage of the PL6 and bump controller. I do know that it will take longer to charge packs since I wont have the full 40 amps the charger can do. I am on a 12v system right now which is fine for now. I dont think taking a deep cycle to 24v will net me the 40 possible amps and I dont think the batteries can handle that for to long if they could do it. So if I can get around 9.9 amps for the packs I can get almost 3C on the 3300 mah packs I have or 9 amps for the 3000 mah packs I have. I charge 1 stick pack for a cycle at a time.

I could also do an inverter at 2000 watts and I should be able to pull my max 3C charge rate for 2 packs. I know I would have losses in there due to the inverter, power supply and the charger.

I found a solar kit on amazon by renogy which is rated at 100W at 5 amps in perfect conditions. My deep cycle should be able to handle 8 amps for max charge. I think this kit would bundle nicely in the van and be able to serve as a dual purpose rig. Not only can I use it for the hobby but when I go camping also. I have no intention on charging while driving due to gas releases from the deep cycle. I real question is could a 100w panel keep me going at the field for the day? Basically leave the house with charged packs and then attempt for 9 total flights which means each stick would need 2 more cycles after getting to the field.

this solution if it works would be cheaper than a generator, cleaner and quieter than a generator. Plus I could use it for other things like camping.

[Stambo]

What sort of deep cycle is it if it can only handle 10 amps, give me some specs from the battery, I am sure it could handle more.
Most deep cycle batteries can output starting current if you ask them to as we use this as emergency start on some of the campers I have kitted out.
I have done automotive electrical for a living for many years, 12v is my thing.

[cml001]

Yeah.. I honestly say just get a 1000-2000 watt generator... U can pick one up pretty cheap at Harbor Freight... You could spend $600 & up on a Honda(if u got the $, it's the way to go!).. I personally went for the Hyundai 2000 watt for $500... Works like a charm! A bit heavier than a Honda.. Specs are a little better actually.. May be a tad louder, unless u have dog ears tho u won't notice. Several options.. And u don't have to break the bank to get one.. But it's the easiest way to go for field charging in my opinion... Otherwise its seems like a whole new hobby.

[murankar]

thats just it, the cost. Long term it could be a wash between new batteries or fuel and maintenance of the generator. Solar for my needs works out to be cheaper up front. My only hang up is how much solar juice do I need to keep me going. With Solar I can also cover the oh crap factor. I am looking at this to be many things not just charging packs at the field. My battery will always be in the van. I dont plan on moving it except to charge. So the weight is not much of an issue.

All though I do like the thought of using a generator.

[cml001]

It's the easiest way.. Never really looked into solar... Wouldn't think it could as efficient. Don't know.

[murankar]

Well there are trade offs. Like not being able to push a PL6 to a 1000 watts 24v at 40 amps. Then again I dont charge at 40 amps so its not much of an issue. Its cleaner over all, makes no noise (camp grounds) and dont have to lug fuel around which puts off odor in the van. I just find it more versatile for what I would like to do. It also appears to take up less room in the van. The panels can be attached to the luggage rack on the top of the van or secured for storage up there.

[pvolcko]

Charger and bump controller aren't going to pull much at all compared to the charging process itself. Negligible.

If you have a 80Ah deep cycle battery, keep in mind you don't generally want to discharge it more than 50% or else you will be cutting the life of that battery somewhat. So if you plan to never draw it down more than 40Ah, how many packs is that?

40Ah at 12V is 480Wh

3300mah 3S pack at 30% capacity will take about 2300mah or 26Wh
4500mah 6S pack at 30% capacity will take about 3100mah or 69Wh

Figure about 15% inefficiency in the charge so:

3S 3300mah pack will draw 30Wh
6S 4500mah pack will draw 79Wh

That's 16 charges on the 3S 3300mah pack and 6 charges on the 4500mah 6S pack. If you do 2 or 3C charge rate then it will be more inefficient (more heat generated in the charger and the packs) and the faster you pull current out of a deep cycle battery, the less effective Ah it has so that is an additional level of inefficiency.

If you add a 100W panel to the mix, it will help you keep that deep cycle charged (get a charge controller to go between the panel and the battery). It will probably keep up with a 3C charge on the 3S 3300mah pack by itself, but you will be stuck at around 1C on a 6S 4500mah pack. Using the deep cycle as a buffer you can probably get a full day of flying and 3C charging the 6S 4500mah and probably be fine, as long as you have good light hitting the panel.

[Stambo]

To add to what Paul said, if you add a good charge controller that can be switched on and off, you could also hook up your vehicle charging system as a backup. Or add a switchable VSR (Voltage sensing relay). Still works out cheaper than a generator, and much quieter.
Would your solar panel be permanently fixed to the van?
I would not be overly concerned with venting inside the vehicle, but if as you said the battery becomes a permanent fixture, an externally vented case would be a good idea. A computer case fan fed from ignition could also help there.

[murankar]

So the luggage rack is 45" X 64" of space. That allows for about 2" of overhang (1" on each long side). So doing a fixed mount could be ideal on-the-go roof. Now I could do a setup that allows for 1 or 2 extra panels on-the-go ground for future expansion. I was also thinking of using the van as a backup charger . The controller I found is 30 amps in. I believe the controller will control the output Amps. Right now I am just planning. I want ringer more numbers just don't know I can cover the 6s packs.

[murankar]

My field is very open for direct sun all day. I went to a field today that was supported on solar. Their panels looked to be 200w a piece. They have 2 panels along with 4 batteries. Their batteries are larger in capacity than mine. In the end they have both 12 and 24 volts. I was told they can support up-to 30 pilots all day.

[pvolcko]

There's a club around here that also uses solar for their club charging and power needs. They have a few panels on the roof of their pavilion along with a mobile trailer with another couple panels as auxilliary on event days. Seems to work for them, even in this less than ideal climate for solar (upstate NY, notorious for lots of cloud cover most years).