PV system upgrade advice

[angelakelly]

Hi!

This is my second posting, and like many other new people coming in, I have a system that isn't ideal. It was a snap purchase based on the fact that my usual routine of going into a coffee shop in the mornings and recharging got nixed. It currently works for my needs, but based on my first posting, I don't think I've enough juice coming in to fully charge my batteries. So, I was wondering if I could get some advice on where I'll get the most bang for my buck in terms of adding or replacing components.

Current system
2 x (Wallmart) Everstart 24DC batteries, wired in parallel. !01Ah @1A (which is probably about 85Ah@20hr rate)
2.x 100w Dokio folding mono panels (In real-world usage, I tend to pull in about 50W per panel, depending on time of day, angle, etc)
2 x 10A PWM charge controllers (came with the panels)

System used in a camper-van conversion while traveling.

Useage:
The only thing I really run on these is my laptop, and to charge up devices as needed. I do have a 1500W modified sine wave inverter, but never use it as everything I have is purely 12v. I got an adapter for my laptop to run it directly off the car battery.

Laptop usage time 7-9 hours per night.
Amps 1.5-2 depending on whether I'm playing my game or not.
Wh used per day, about 110 (average)
Ah used per day, about 10-12 (average)

Currently, I replace the night's usage the next day. I've yet to go two days between charges, and I've got enough extra laptop batteries that if I have a bad solar day, I can get through a night.

What I would like to be able to do though, is to go 2-3 nights, or ideally 3-5 nights between charging, as it would be nice to have the option of staying in the pacific NW for the winter.

Questions:

1. Given that I will keep these batteries until they croak, should they be wired in parallel or series? From what I am reading, it sounds like series is better to make sure each cell is evenly charged. CCs can do 12v or 24v systems

2. I'm pretty sure the system is undercharged. At 170Ah (85ah x 2) I would want to be able to put in 17A. Currently, I top out at 7-12. If we take wallyworld at their word and go with the stated 101Ah, that's 202ah for the system, so I'd want about 20A. To get this balanced, should I get a third 100w panel, or an mppt controller to squeeze out some extra amps?

Any other advice?

As always, thanks!
Angela

[chrisski]

For your laptop charger, can it take 48 VDC, 24 VDC and 12 VDC? If it says 48 VDC, then series would work, if not, you’d be stuck at 24 VDC. I might have read something wrong, but the system is 12 volts but you have two batteries, 24 VDC each in parallel, so voltages aren’t matching. If you are thinking of going up to 48 VDC, your charge controller would need to be able to detect and charge that also.

For the battery, is it a deep cycle battery? When I think Wal Mart and Everstart, I think car batteries which are good for short jolts of large amps, and not really good for continued usage. THe Deep Cycle lead Acid Batteries are supposed to be good to a 50% Depth of Discharge, but car batteries usually measured in cold cranking amps, I don’t know. There’s formulas to use a 20 hour rating on a battery to see what it can produce at one hour, but taking a car battery, and going the other way, I don’t know if it works.

[angelakelly]

I'm sorry about the confusion. 24DC is the model number of the batteries. The 24 refers to the size and the DC refers to deep cycle. However, these aren't true deep cycle, they're hybrid marine batteries. Each is 12v and currently wired in parallel. As far as the laptop charger, I thought about it after I'd posted. I"m not sure it could hook to a 24V source, so I might not be able to go 24 without somehow adapting.

[Bala]

I have done a lot of camping without solar and have just set up solar on my 4WD and caravan. I like to park foe a week without startin gthe car so recharge form the engine alternator is not an option. I carry a small generator and am usually away from camp for the day so run the generator to recharge when I am away. I now have solar but generally need to park in the sun which is not ideal, although all my panels can be made portable so I can park in the shade in I wish.

It is about your lifestyle wishes.

"What I would like to be able to do though, is to go 2-3 nights, or ideally 3-5 nights between charging, as it would be nice to have the option of staying in the pacific NW for the winter."

The above line from your post is the question you need to find an answer to. You have been able to comprehend information easily so have a look in the offgrid section at the stickys on stand alone system design.

Things to consider;

Days between charge is termed Days of Autonomy. So you can design for 5 days but then you have used a lot more so need to put a lot more back. As it is mobile van you need to either drive to recharge from the engine alternator, have enough panels or a generator. The more days of autonomy the bigger the battery bank needs to be, so more cost, size and weight.

Only you know how you want to live so really you are the best person to design your system.

Lithium may be an option to look at but much more expensive.