Hurricane Season Preparation

[2Big2B]

Looking for advice for building a small 24v ,single or double solar panel, emergency power supply.

Hurricane season is on the horizon, and I think we are overdue for a bad hurricane here in the Virginia Beach, VA area.

In preparation I am putting together something I can use if we lose power for a week or two.

I already own a 1500w 24v, as well as a 600w 24v pure sine wave inverter. Both are Samlex that I found amazing deals on; $200 for the Simex 1500w 24v, and $70 or the Simex 600w 24v inverter. Too good to pass up.

I already own 3 sets of 24v 100ah LiFePo4 battery packs.

I also own several spare Anderson 175 2awg and 4awg pole connector cables from other projects.

If you are wondering why 24v, well both of my two power wheelchairs use those DIY 24v 100ah battery packs I built, AND because of all of the fusing protections are already built into the power wheelchairs they make a great platform. Very convenient. All I need to do is slap on a set of 175ah Anderson pole connectors, one tucked away under the seat of the wheelchair, to connect a 24v Simex inverter. Portable. Simple. I have already tested the 600w inverter and it works great! The 1500w inverter arrives later today...

Not sure what to do with the Simex 600w 24v inverter yet, now that I have the 1500w inverter, but it will attach it to one of the power wheelchairs anyway, as a spare to keep in the bedroom I guess.

So now I can go awhile during a power failure until I go through battery exhaustion, about 7kwh between potentially all three packs I guess. But if things get really weird I would like to be able to recharge them one at a time in rotation to extend beyond that fixed 7kwh capacity.

To do that I need the cheapest, small but efficient solar panel(s?) and 24v charge controller combination. That should be simple, no?

My biggest constraint is access to the sun. I live in a ground floor apartment with a very small South facing patio and access to the back lawn if I can carry a panel out there. It is a stretch, the panel(s) need to be managable - not too large or heavy.

I ought to be able to set up something.

I have watched several DIY 12v projects, but what I cannot seem to run down is what exactly I need to shop for, using my 24v. I don't want to spend a lot on it, and as it is a temporary emergency power station, I will never need to upgrade beyond one or two (at most) used(?) solar panels.


Can someone help me out with what solar panel(s) and 24v charge controller can I hook up in a pinch?

Used, Alibaba, or some obscure deal on ebay that I might find for a source is how I usually shop for stuff like this, as long as I know exactly what I want..

 

[DIYrich]

24v solar charge controller. With 300ah of batteries, probably want at least 60 amp charge controller. Something like the Victron mppt 100/50.

Or this:

FOR SALE - Outback FM60 Charge Controller (NW Ontario, can ship from Minnesota)

Selling my Outback FM60. Approximately 6 years old. Nothing wrong with it, I've just changed my system and need something different. Please message me on here to discuss price/shipping if interested. I'm in Ontario, Canada but can get to Minnesota easily to ship from there if makes more sense...

diysolarforum.com

Get panels to match input limits of the charge controller. Assume a 400 watt panel produces 310 watts, that is 13 amps. You would want 4 panels.

 

[2Big2B]

24v solar charge controller. With 300ah of batteries, probably want at least 60 amp charge controller. Something like the Victron mppt 100/50.

Get panels to match input limits of the charge controller. Assume a 400 watt panel produces 310 watts, that is 13 amps. You would want 4 panels.

Thank you.

But I only want to charge one 24v 100ah battery pack at a time. With that said, can I scale down to say, the Victron mppt 75/50? Seeing that those are usually in high demand, my instinct tells me that is what I need, but I don't really know the math.

I want to run a very modest setup to maybe run my mini fridge (probably off of the 600w inverter if it has enough juice, or the 1500W, which should work fine) .

What is my minimum cost combination I could quickly string up after a hurricane power outage?
What amperage and voltage panels should I be shopping for?

 

[DIYrich]

But I only want to charge one 24v 100ah battery pack at a time. With that said, can I scale down to say, the Victron mppt 75/50? Seeing that those are usually in high demand, my instinct tells me that is what I need, but I don't really know the math.

If you only want to charge one battery at a time, then 30 amp to 50 amp, depending upon the max charge rate of the battery, and how many panels you want to have.

What amperage and voltage panels should I be shopping for?

Pick out your charger first, and then panels that are compatible with the charger.

 

[Brucey]

Can you hang a panel vertically off your south facing patio? Under the railing?

 

[wme]

Most controllers are 12/24v auto set. Just go with your budget and read reviews. There are some very good tier 2 controllers available.

 

[Q-Dog]

Victron 100/20 is a little beast and perfect charge rate for a single 100ah battery. At 24 volts it is slightly overpaneled with 600 watts, and it just works. 100 watt panels are easy to carry and should be easy to find almost anywhere ... I have a bunch that I picked up for $50 each a few years ago, on ebay and an amazon closeout. Most panels that size are shipped free.

Best deals I found were from December to January which won't help you now.

 

[Brucey]

I've been having good luck with these ecoflow bifacials, the single sided are $55 each including shipping.

https://www.amazon.com/gp/aw/d/B0C9HMKCCR

 

[2Big2B]

Victron 100/20 is a little beast and perfect charge rate for a single 100ah battery. At 24 volts it is slightly overpaneled with 600 watts, and it just works. 100 watt panels are easy to carry and should be easy to find almost anywhere ... I have a bunch that I picked up for $50 each a few years ago, on ebay and an amazon closeout. Most panels that size are shipped free.

Best deals I found were from December to January which won't help you now.

Thank you. That's a good start. A bit pricey though. I would like to keep close to about a $200 budget for this contingent use only project.

I am wondering if I could go cheaper on the controller.
But, I am struggling with the math for charging my 24v 100ah pack and how it relates to selecting a controller.

I think that a 100/20 charge controller probably means a 100v max @ 20ah limit. I have read repeatadly about not sending overvoltage to the controller, so that there has to be a pairing with the panels. I am fuzzy about choosing and wiring up a pair of ECO-WORTHY 2pcs 100 Watt Solar Panels 12 Volt Monocrystalline Solar Panels, as has been suggested, as an example. Series or parallel? 12v or 24v?

Or better, is there a single panel solution, and if so does it matter if it is 12v assuming the controller would output the required lifepo4 charge voltage of 25v - 29.2v ?



With my perceived notion that the 75/50 is very popular, probably for its cost, wouldn't that work? Or is there a clone version on Alibaba that I should be price shopping for?

 

[2Big2B]

I've been having good luck with these ecoflow bifacials, the single sided are $55 each including shipping.

https://www.amazon.com/gp/aw/d/B0C9HMKCCR

I see they are two 12v panels. Do I hook them up in parallel or series ft or a 24v system, or foes it even matter with a Victron 100/20 , as a controller that Q-Dog suggested?

 

[Brucey]

So the 75/50 wouldn't work?

The blue solar 75/15 for $50 is hard to beat for value.

 

[Brucey]

I see they are two 12v panels. Do I hook them up in parallel or series ft or a 24v system, or foes it even matter with a Victron 100/20 , as a controller that Q-Dog suggested?

Yes you'll want to series them otherwise you won't have enough voltage to start charging (Victron SCCs generally require 5V more than charge voltage, so for a 28V battery you'd need 33V minimum).

 

[Brucey]

The blue solar 75/15 for $50 is hard to beat for value.

I would def go with 100/20 if your budget can stretch, also allows for future 48V expansion in the future.

 

[2Big2B]

I would def go with 100/20 if your budget can stretch, also allows for future 48V expansion in the future.

I do prefer robust equipment, hence my getting those Samlex inverters, even though I could have gone after the cheaper higher watt Chinese crap.

But we have a different mindset about what I need. I will not expand beyond only the bare minimum I would need to recharge a battery pack in the aftermath of a major hurricane and resulting long duration power outage. So, I cannot justify the expense on something I will never need to do. On the otherhand, if a 100/50 controller is inheritly more robust against failure, as are the Simlex inverters, I could justify stretching the budget. What do you think?

 

[Brucey]

I do prefer robust equipment, hence my getting those Simlex inverters, even though I could have gone after the cheaper higher watt Chinese crap.

But we have a different mindset about what I need. I will not expand beyond only the bare minimum I would need to recharge a battery pack in the aftermath of a major hurricane and resulting long duration power outage. So, I cannot justify the expense on something I will never need to do. On the otherhand, if a 100/50 controller is inheritly more robust against failure, as are the Simlex inverters, I could justify stretching the budget. What do you think?

Reliability is the same, big or small units. If it's truly a budget crunch the 75/15 will be fine.

 

[2Big2B]

Yes you'll want to series them otherwise you won't have enough voltage to start charging (Victron SCCs generally require 5V more than charge voltage, so for a 28V battery you'd need 33V minimum).

View attachment 217370
View attachment 217371

Thank you. This is sort of what I have been searching for. Oddly I don't seem to find alot of examples or discussion about a simple 24v application like mine. RV application examples all seem to all be 12v. 24v apparently is a marine application thing it appears. Better than 12v, safer than 48v when troubleshooting ankle deep in the bilge... I probably should investigate some marine diy forum somewhere...

I would prefer a single panel if doable?

And I am still confused about how a pair of 12v in series panels can produce 33v - or is that magic that the charge controller takes care of?

Sorry for these noob questions...

 

[Brucey]

12V panel doesn't mean it's got a 12V VOC. Best to forget about 12 and 24V panels and focus on the Voc and Vmp ratings. Voc can never exceed the SCC voltage rating, and needs to be temp compensated for cold mornings where V rises. Not an issue for you with 75V max.

The problem with the 200W panels is you won't get enough voltage out of one of them for a 24V config.

 

[2Big2B]

Reliability is the same, big or small units. If it's truly a budget crunch the 75/15 will be fine.

Thank you Brucey. That gives me something to start price shopping. If the cost difference is insignificant I with "super size my order"!

I wondered if the larger controller has bigger capacitors, making them inheritly more robust.

Speaking of capacitors, I wonder what condition the caps are in of the used Simlex 1500 inverter I just ordered, arriving today. My impression is that it may have been heavily used in an industrial setting. I know from repairing vintage Fender tube amplifyers that those caps typically leak and need to be replaced. i wonder if that applies to this inverter...

 

[2Big2B]

12V panel doesn't mean it's got a 12V VOC. Best to forget about 12 and 24V panels and focus on the Voc and Vmp ratings. Voc can never exceed the SCC voltage rating, and needs to be temp compensated for cold mornings where V rises. Not an issue for you with 75V max.

The problem with the 200W panels is you won't get enough voltage out of one of them for a 24V config.

Thank you again!

So, there is no affordable way around it: I need at least two panels? If so, what are the minimum requirements for small footprint panels? Could they be found even cheaper?

I need to better educate myself about Voc and Vmp ratings. It is still very foreign to me.

 

[Q-Dog]

Victron naming: the first number is the max VOC of the panels and the second number is the max charging amperage. 75/15 can take no more than 75 VOC and will charge no more than 15 amps. 100/20 can take max VOC of 100 and will charge up to 20 amps max. VOC of the average 100 watt panel is about 22, so you could run 3 of those in series on the 75/15, and 4 of those in series on the 100/20. You never want panel VOC to go over max VOC of the charge controller.

You want to charge your batteries at the SLOWEST rate you can tolerate, not at the max rate the battery can tolerate. 15 to 20 amps is a comfortable charge rate for a 100ah battery. You can limit the charge rate of a Victon SCC, but you can't make it charge more than the built in rate, so a 15 amp SCC will not go over 15 amps, ever. Slower charging is better for the batteries, BUT, in an emergency situation you may want to charge at a higher rate. As long as you don't regularly charge at the maximum rate you aren't hurting the batteries very much.

 

[HarryN]

I like these bogart engineering solar charge controllers.

I am building a small power system under my work bench in the garage - started out as something else, but is evolving into the same thing.

We don't have hurricanes, but we do have fire season every year.

Small test fixture

Sometimes it is easier to show people things in photos than to describe them. So I made a little test fixture from left over parts, nothing fancy. In this case, some people asked about methods of dealing with pre-charging the capacitors on the input stage of inverters, and I had suggested that...

diysolarforum.com

 

[HarryN]

This charge controller might do what you are after.

It can take in the power from a nominal 12 volt panel. ( ~ Vmp 18 volts)

Charge 24 volt LiFe batteries.

GVB-8 (BOOST) – Sunforge LLC

sunforgellc.com

GVB-8-Li-28.4V

You can call them to double check.

They are very small and I have used some of the other models.

Mount it on a heat spreader, such as an angle aluminum or something metallic on your wheel chair if possible. If you mount it on a piece of wood, it is difficult to remove the small amount of heat generated when running from full power mode.

 

[2Big2B]

Victron naming: the first number is the max VOC of the panels and the second number is the max charging amperage. 75/15 can take no more than 75 VOC and will charge no more than 15 amps. 100/20 can take max VOC of 100 and will charge up to 20 amps max. VOC of the average 100 watt panel is about 22, so you could run 3 of those in series on the 75/15, and 4 of those in series on the 100/20. You never want panel VOC to go over max VOC of the charge controller.

You want to charge your batteries at the SLOWEST rate you can tolerate, not at the max rate the battery can tolerate. 15 to 20 amps is a comfortable charge rate for a 100ah battery. You can limit the charge rate of a Victon SCC, but you can't make it charge more than the built in rate, so a 15 amp SCC will not go over 15 amps, ever. Slower charging is better for the batteries, BUT, in an emergency situation you may want to charge at a higher rate. As long as you don't regularly charge at the maximum rate you aren't hurting the batteries very much.

As far as my LiFePo4 wheelchair battery packs, I typically keep them topped off with my 10amp LiFePo4 charger, never running them down below more than about 80%. I use a shunt @ control pad display as my fuel guage and trips around the neighborhood never dips much below that.

I am not sure if keeping them at a high SOC is bad for them, but it is just a simple thing to do, leaving it on the charger to shut down to rest @ 26.8v.

So I am happy to charge at 10amps. Of course more is better in an emergency scenario. Still, I wonder if there wouldn't be a lot of cloud cover after a hurricane leaves the area. Is that another consideration?

Also, as I start to explore solar panels, that Amazon deal for "ECO-WORTHY 2pcs 100 Watt Solar Panels" is intriguing. I also see a 3 piece deal on them. I also see some deals on "100W Watt 12V Monocrystalline Solar Panel 12BB Cell" @ about $50 each. They look to have a small footprint an two or three of them in series might do the trick. I need to research them.

 

[Bob142]

Does free + shipping fit your budget for a charge controller? I'm giving away an HQST 30A MPPT SCC. See link below.

Bob's Gear Giveaway

Over the years I’ve accumulated a bunch of smaller scale solar/backup power gear I’m no longer using due to a variety of reasons (system upgrades, abandoned plans, stuff happens etc.) Rather than have this equipment continue to collect dust, I thought I’d do some basic functional tests (maybe...

diysolarforum.com

 

[Brucey]

Does free + shipping fit your budget for a charge controller? I'm giving away an HQST 30A MPPT SCC. See link below.

Bob's Gear Giveaway

Over the years I’ve accumulated a bunch of smaller scale solar/backup power gear I’m no longer using due to a variety of reasons (system upgrades, abandoned plans, stuff happens etc.) Rather than have this equipment continue to collect dust, I thought I’d do some basic functional tests (maybe...

diysolarforum.com

Bob is the man I can confirm, just got my freebies!