The big question: more batteries or panels first?

[Tamacat]

We're retired and on a tight budget, so this month and next, we get two more 100 watt panels, or another itty bitty 50 ah battery (as much as I'd like to get a 100 ah, no mix and match). Where we're at, we're getting about 4 amps steadily between 10 am and 2 pm over the day, enough to charge up a portable power station, and keep the fridge running for the day. At 4pm, the fridge goes on the power station and we let the LifePo4 charge up for the night. Otherwise we wake up to horror (thank goodness for the Renogy rover's jump start trick!) Should we get the second 50 ah battery or the 200 watts of panel first? Will 400 watts (more like 8 amps) overwhelm the one 50 ah battery?
Thank you for all your help!

 

[Zwy]

I'd vote more battery. This way you have power on cloudy days to get you thru.

I practice what I preach, less panels, more battery. https://diysolarforum.com/threads/get-a-big-battery.70751/#post-896140

 

[n2aws]

We're retired and on a tight budget, so this month and next, we get two more 100 watt panels, or another itty bitty 50 ah battery (as much as I'd like to get a 100 ah, no mix and match). Where we're at, we're getting about 4 amps steadily between 10 am and 2 pm over the day, enough to charge up a portable power station, and keep the fridge running for the day. At 4pm, the fridge goes on the power station and we let the LifePo4 charge up for the night. Otherwise we wake up to horror (thank goodness for the Renogy rover's jump start trick!) Should we get the second 50 ah battery or the 200 watts of panel first? Will 400 watts (more like 8 amps) overwhelm the one 50 ah battery?
Thank you for all your help!

With the existing solar panels, does your battery recharge to full daily?

If yes, I'd probably go. for more battery.
If no, I'd probably go for more PV.

As for the 8 amps overwhelming one battery, you'd want to read your battery specs. most batteries can charge up to .5C, at 8amps, you'd be under .25C. But the spec sheet will answer this question more completely than I could.

When you say the renogy rover jump start trick, what is that? I can't say I've heard of it.

 

[Brett V]

I faced the same question recently, went with more batteries.

The theory is: There are many more opportunities for used/surplus panels to be sourced domestically than battery cells. With war and deteriorating relations with China looming, the probability of the supply chain going to hell in the coming years is high.

 

[42OhmsPA]

Both... Save your money with 100w panels and buy used grid tie panels for much less per watt. Why can't you add 100ah battery? If you're running in parallel you can use different capacities.

 

[MisterSandals]

we get two more 100 watt panels

Is there a reason you are looking at 100W panels and not big cheap ones locally?

Solar Panels - electronics - by owner - sale - craigslist

Pristine condition (unused) 255W MC-4 connectors 1 year warranty Free local delivery

inlandempire.craigslist.org

or

280W SUNTECH SOLAR PANEL - USED - electronics - by dealer - sale - craigslist

Used. This a very clean Solar Panel AND it's still cranking out great power! QUANTITY AVAILABLE = 2 77" x 39" This panel will work great with our 60 Amp MPPT Solar Charge Controller that we have on...

inlandempire.craigslist.org

 

[Tamacat]

With the existing solar panels, does your battery recharge to full daily?

Absolutely, many times over, because the fridge and power station charging (which makes me wonder if I'm abusing the battery or something).

If yes, I'd probably go. for more battery.
If no, I'd probably go for more PV.

Yes then! (Since the battery hook up is easier for me, and in December, the mechanic can climb up there and do his thing.)

As for the 8 amps overwhelming one battery, you'd want to read your battery specs. most batteries can charge up to .5C, at 8amps, you'd be under .25C. But the spec sheet will answer this question more completely than I could.

I'm hoping in summer we'll get a bit more, but right now, I'm just reading the Renogy screen.

When you say the renogy rover jump start trick, what is that? I can't say I've heard of it.

Oh this is freaking awesome (scuse my 80s 90s enthusiasm, I'm an old lady). My biggest worry when we looked at solar was the whole driving miles from camping to restart a dead lithium battery. So the first night we had the solar set up, we woke up at five thirty the next morning to find the battery dead. Deceased. Nailed to the perch. Panic ensued. Searched for hours (cloud cover), figuring we'd go to Interstate Battery and ask them to charge it at 8 am, and finally cobbled together the answer to the ACr notice code. I think it's ACr, the thing has slipped my mind. That code means it's flicking power at the battery to try and wake it up. It's happened twice now and the battery comes right back.i just have to make sure it's at 12.7v before we loose sun for the night. Just leave the battery alone, no draw on it, unplug everything or just turn off the inverter, and let the sun do the work. Brilliant. I feel bad for all the people that had to freak out because the instructions tell you nothing, it's word of mouth and has to be passed along. All the Renogy Rover's do it. Not aware of the others.

 

[Tamacat]

Both... Save your money with 100w panels and buy used grid tie panels for much less per watt. Why can't you add 100ah battery? If you're running in parallel you can use different capacities.

A. I don't buy used to mix with new, because old always drags new down. These panels are 59$ a pop.
B. We live in a van and I'm not willing to play silly buggers with the smaller battery dragging the big battery down as a personal preference. I have my suspicions (conspiracy theory?) about RVs catching on fire.

 

[Tamacat]

Is there a reason you are looking at 100W panels and not big cheap ones locally?

Solar Panels - electronics - by owner - sale - craigslist

Pristine condition (unused) 255W MC-4 connectors 1 year warranty Free local delivery

inlandempire.craigslist.org

or

280W SUNTECH SOLAR PANEL - USED - electronics - by dealer - sale - craigslist

Used. This a very clean Solar Panel AND it's still cranking out great power! QUANTITY AVAILABLE = 2 77" x 39" This panel will work great with our 60 Amp MPPT Solar Charge Controller that we have on...

inlandempire.craigslist.org

The company we got the kit from has a two for 125$ set, they'll fit in right next to the other two on the van roof, and we're super happy with these after a week and a half, cloudy days, they do great. Plus, we planned on these, and the holes are in, plugged with silicon caulk for now, ready to literally plug and play.

 

[Tamacat]

I faced the same question recently, went with more batteries.

The theory is: There are many more opportunities for used/surplus panels to be sourced domestically than battery cells. With war and deteriorating relations with China looming, the probability of the supply chain going to hell in the coming years is high.

Yeah, this going to hell thing. We ended up converting our van just in time to ride the COVID wave. Too bad the price of plywood went up to 70$ a sheet, and slowed us down, but we made it.

 

[chrisgraham]

We're retired and on a tight budget, so this month and next, we get two more 100 watt panels, or another itty bitty 50 ah battery (as much as I'd like to get a 100 ah, no mix and match). Where we're at, we're getting about 4 amps steadily between 10 am and 2 pm over the day, enough to charge up a portable power station, and keep the fridge running for the day. At 4pm, the fridge goes on the power station and we let the LifePo4 charge up for the night. Otherwise we wake up to horror (thank goodness for the Renogy rover's jump start trick!) Should we get the second 50 ah battery or the 200 watts of panel first? Will 400 watts (more like 8 amps) overwhelm the one 50 ah battery?
Thank you for all your help!

In general, 400 watts of panels can potentially generate up to 20-25 Ah of energy on a sunny day, which is higher than the 50 Ah battery's capacity. To prevent overcharging, you should ensure your charge controller is properly set up to regulate the charging process and protect the battery.

 

[MisterSandals]

In general, 400 watts of panels can potentially generate up to 20-25 Ah of energy on a sunny day, which is higher than the 50 Ah battery's capacity.

Huh? 20-25Ah higher than 50Ah?

400W / 14V charging = 28.6A
50Ah battery / 28.6A charging = 1.75h to recharge from empty

28.6A charging x 5h solar = 143Ah

 

[Q-Dog]

I lean towards adding more battery now because I don't like to wake up to dead batteries. But if your existing battery rarely gets fully charged in one day, then add panels first.

 

[Tamacat]

In general, 400 watts of panels can potentially generate up to 20-25 Ah of energy on a sunny day, which is higher than the 50 Ah battery's capacity. To prevent overcharging, you should ensure your charge controller is properly set up to regulate the charging process and protect the battery.

We're adding the battery first. Since it comes in kits of 200 to one 50 ah, 400 to 2 x 50 ah should work? Then later, we switch up to more ah, more panels, more controller amp as we go? Thank you for settling that in my mind! ?