Battery Advice

[Brian]

So I wanted to play with a small solar system with no planned load. Other than car camping next summer a couple weekends. So I was planning a 50ah battery, 20a solar charger, a 600w inverter, one or two 100w panels. So I find the epever 20a but bought the 30a. Next I bought a pair of HQST 100w panels, then I buy 1000w pure sine wave inverter. Shopping for batteries to put it all together and bought 4 valance U27-12XP and busted the budget. Being in Minnesota I'm concerned the 2 100w panels will not maintain, much less charge these batteries. So to keep these batteries happy over the winter plus should I buy a charger plugged into a outlet in the basement. Or buy 2 more 100w panels (total of 4ea 12v 100w HQST panels)? Or something else?

 

[eddie1261]

All I would change is to get a 100ah battery. Preferably lithium. WELL worth the money and less expensive when you factor in how long it will last you.

 

[offgriddle]

I'm doing what your doing right down to the epever. My next move is to add two more 100 watt panels since the two that I have now don't give me the charging power and speed that I am looking for. Also, wiring the panels in series/parallel for 24vdc output is helpful and your epever should be able to automatically configure for that, but check the manual just in case. Note: even with 24 vdc input, the charge controller will still output 12 volts if that's what it sees for a load.

 

[ImpatientMaker]

I was going to build a small "car camping" generator, especially after the power outages in California, but then I go all "tool time" and keep trying to make it bigger. Plus I just learned about building my own LiFePo4 batteries from used ones. So much to learn! Gotta find that balance.

 

[Brian]

All I would change is to get a 100ah battery. Preferably lithium. WELL worth the money and less expensive when you factor in how long it will last you.

Sorry I didn't explain well enough. I bought 4ea 138ah batteries. 552ah total. And what to use to keep them charged.

 

[Brian]

I'm doing what your doing right down to the epever. My next move is to add two more 100 watt panels since the two that I have now don't give me the charging power and speed that I am looking for. Also, wiring the panels in series/parallel for 24vdc output is helpful and your epever should be able to automatically configure for that, but check the manual just in case. Note: even with 24 vdc input, the charge controller will still output 12 volts if that's what it sees for a load.

Do you think 4 100w panels will be enough?

 

[offgriddle]

Do you think 4 100w panels will be enough?

Ok let's see, my 100 watt panels put out 5.7 amps in full sun at 12 VDC. So, if I had four of them, that would be roughly 20ish amps per hour that four panels could generate at the panel. Now, depending on how much you lose in the wire going from the panels to your charge controller, (just for grins let's call it 18 amps reaching the charge controller), that would mean that it would take just under three hours to fill your 50 amp hour battery up. If it's cloudy, of course the charge time will be way longer. Try it and see. Peace.

 

[morth]

400 watts of solar might fully charge 1 of those from empty in a day, but it needs to be really sunny and long. Winter will be an issue. I just went from a SOC of 3% to 50% on a single U27-12XP with 200 watts of solar, full sun and 4 hours, then the clouds rolled in. It averaged about 12ah per hour when the sun was shining full blast. Based on that, a fully depleted battery will take around 9 hours of full sun to charge on solar alone. I've been thinking about getting another 200 watts to make sure I can recharge fully in 1 good day. My Valence batteries are used, and are down to about 112 ah of storage. 1 battery ran my 17 cubic foot freezer/fridge and a laptop for 16 hours. I still had 3% left so I may have been able to stretch it a bit more but didn't feel like hammering the battery much more on that test. I verified it can go through the night, but it will be empty in the morning. I had planned on running 2 batteries in parallel to ensure at least another day of run time without recharging and can still do that if needed, but the more I thought about the various loads I need to run and where they are in the house, I'm starting to think that having another inverter would make more sense to use with the other battery so things that are not in the kitchen area can be powered without running extension cords all over the place. Plus, moving just one battery is a lot easier. Portability is something to consider in emergency situations. During an ice storm we had in Raleigh a while back, a tree took out the location where a whole house generator would have been installed. That would have really sucked if I had one installed at the time. From that point on, I always consider the ability to run with structural damage or having to leave the house. I can throw a couple panels, inverter and batteries in the truck and still have room for family stuff and food/water. I can easily run a small fridge, a microwave and charge cell phones with 200 watts of solar and 1 battery over an extended period of time. At this point, my planned use is more of an emergency scenario rather than running loads daily so I will not be charging the batteries all the time.

How were you planning on arranging the batteries? 2s2p? That would give you 24v and 274ah. All 4 in parallel gets you to 12 v and 552ah. If you run either of those configs down too much, 400 watts of solar will not be able to fully recharge it in a day. If your planned DOD is 50% or less, things look much better. I got a 60 amp RV charger (the U27-12XP can charge at a max of 70 amps) to make up for short falls. I can run a generator for a couple hours and be topped off while running other heavy loads that the batteries/inverter can't deal with.

Lots to think about. Much depends on how you intend to use the system.

 

[brassmonkey001]

I've got 530W of panels and I've had a (not fully) discharged U27-72XP on bulk charge for 19 hours so far (no load) . The weather hasn't been great to be fair but I'm hoping it should be fully charged today!

 

[morth]

I've got 530W of panels and I've had a (not fully) discharged U27-72XP on bulk charge for 19 hours so far (no load) . The weather hasn't been great to be fair but I'm hoping it should be fully charged today!

Yeah, it's amazing to watch the charge current drop like a stone when the clouds roll in. 12 amps one minute, 1 amp the next....

 

[brassmonkey001]

22 hours and 36 minutes of bulk charging before it switched to absorption! I think it's finally full now!