System design question Philippines - more panels vs bigger batteries

Hi Everyone,
I’m now in the late stages of finalizing a system design for an off-grid PV system for my retirement home in the rural Philippines. The public power grid here is notoriously unreliable with at least one of more brown-outs every week, some lasting 24+ hours. To boot, grid power is very expensive.

However, while the cost of PV panels have fallen a lot, the cost of batteries, esp LifePo, remain quite expensive. Therefore, before soliciting supplier bids for a system, I would appreciate the advice of more experienced solar experts, on whether it makes sense to buy more PV panels as a way to reduce the size and cost of a battery bank.

My thoughts are that with enough PV panels, even on a cloudy day, the system could generate sufficient power to serve most of our essential household needs, or at least extend the capacity of our batteries.

Not sure how the charger controller would handle the ‘excess’ power being generated by panels on a sunny day though…

Would be grateful for any guidance.


Hi @chewface

The issue is that you will have stormy periods (as I know there are many of in the Philippines) where there simply isn’t sun, and all the panels in the world won’t help you with that. Either way you will need a backup generator, I trust you are considering that in the mix, or perhaps you already have one?

You’ll need a proper system design by an off grid expert designer to size your system correctly. It will save you enormously in the long run. There are already a number of threads on this forum regarding systems in the Philippines that aren’t working well due to lack of design. Assuming there is no one with the expertise locally, perhaps there are off-grid experts elsewhere in the Philippines that could work with someone locally?

You can find similar threads regarding off-grid systems in the Philippines here, perhaps some of these posters could help.

I hope that helps.


@chewface oversizing solar is quite common these day and isn’t generally an issue when using DC-coupled MPPT solar charge controllers. When the batteries are full on a sunny day the MPPT charge controllers just reduce the power output to a minimum amount. When oversizing solar, just be careful you don’t put too much current into the batteries during charging. LiFePO4 batteries have a maximum charge rate.

Also, as @Marty suggested you should get someone experienced with off-grid solar to help or you could end up wasting a lot of time and money.


Hi, We are here in PH as well. Our primary system has, right now 4 60amp charge controllers with 32 360 watt panels for a 10kw inverter. We have perfect Azimuth Alignment and have the panels adjustable for 3 seasons. We are going to add lifepo4 batteries soon, 4 sets of 16 280ah, we have been planning the design for 20-30 hours without any sun. We are also adding another 9 360 watt panels and another charge controller to boost the system a bit more. Right now, when the inverter actually works we make enough power on a cloudy day to maintain the battery charge, but when the rain is really bad, we don’t make enough. You need an inverter that uses separate charge controllers so you can use additional panels without overloading. Make sure the charge controllers can talk to each other and have settings for LifePO4 batteries so they will work correctly, our do and maintain perfect charge just clipping the excess. I have an Ames 10kw split phase inverter, (we have Meralco split phase utility system) but it has given trouble from day 1, no one can figure out what’s wrong with it and Ames is useless and hasn’t honored the warranty, don’t buy one!. We have found someone who can do the electrical repairs to the inverters boards, but ours still won’t carry a normal load. Be very careful here, many of the “Experts” don’t even know enough to crimp the connectors on the solar panels let alone design and match components. No one I’ve talked to here knows what azimuth, true south (Northern Hemisphere) proper angle for the latitude, correct wire sizing, nor anything else commonly accepted as basic knowledge is. My suggestion is ask here about everything, Svarky and Marty have helped me tremendously so listen to them. If you have the single phase 230 volt system as many rural areas here have, don’t use a split phase inverter as they cost more and won’t do anything for you unless you want 110 volt as well. Most electricians here don’t understand proper ground and neutral installation and watch out for splicing, they love to do that here and many inverters don’t like it. Good luck! Watch your workers closely to eliminate shortcuts, if you’re not from here, most of them won’t listen to you and as soon as you turn your back will shortcut things and splice and tape things. That’s about it. the dog

1 Like

Hi Richard;
Thanks very much for your candid and informative reply to my question. As an imminent new solar system user/owner, I’m pleased (and relieved) to make contact with a fellow (ex-pat) solar system owner with actual experience here in the Phils, willing to share their knowledge.

A couple of clarifications would be really helpful:

  • you mention that you are about to install Lifepo batteries? Assume 4 x 12V batteries in series? This config would provide 1120 AH total capacity right? What brand are you considering/buying? Through a local Phils supplier? Any warranty?
  • What BMS will you be using to manage the Lifepo batteries?

The next questions are for Marty and Svarky…
Would appreciate your expert opinions on the Growatt SPF 5000TL HVM-WPV combination solar charge controller-inverters? The specs and low prices on these products seem ideal for home system owners like myself. My thoughts are to install 2 parallel 5-6Kw PV arrays, each array connected to a separate Growatt charge controller/inverter. Each Growatt unit would be connected in parallel to sync the phase of their AC output. The Growatt units would be connected to a single Lifepo battery bank using a common copper bus.
While I understand the Growatt products are relatively new on the market and thus not field proven over a long period of time, their low price and combination of features make it economically feasible to buy 3 units and use one as a ‘back-up spare’ .

As “The Dog” has shared, proven solar expertise is hard to find in the Phils and near impossible in the rural provinces. Therefore, the simplicity and all-in-one functionality of the Growatt units are very attractive for non-expert home owners like myself. However before making the plunge your advice and guidance would be very much appreciated.


Hi, Sorry I didn’t reply, I must have missed the notification. I like Growatt inverters, I’ve had good luck so far with them. I just replaced my 10kw Aims inverter that never worked right with a 12kw Growatt. If you’re doing things yourself here, the Growatt with the built in charge controller is easy. Mine has a built in controller but I wanted more solar power so I left the charge controllers I already had connected directly to the batteries and didn’t connect anything to the solar panel connections on the inverter. I set it to battery priority and it works great. I like that I can check anything and reset everything with the buttons the have on the front panel as well as being able to use the Shine Link to see everything on the internet. ( I haven’t gotten this one to work but the other older one is great) The Growatts can be connected and will talk to each other so one battery bank is easy. I haven’t decided on the batteries yet, Growatt has 2 types on that has a 10 year warranty and one a 5 year. They are a bit more expensive than building your own, but are simple and will communicate with both inverters. I found a company in China that I bought my inverter from, the girl there is super helpful and actually got the inverter shipped a month before it was scheduled. She says she has batteries the same as Growatt’s for less money.

Oh, Also! The Growatt batteries are available in 48 volt and I believe the other company’s are as well. I like the panels I bought they are from Future Green Energy Tech. in China, 360 watts each, the last price update I got was $100 each not including shipping and import. But that was a while ago. Where abouts are you in PH? From what I’ve been able to find here ALL the individual LifePo cells are USED! I haven’t found any NEW complete batteries yet either and the costs are multiple times higher than buying new direct. I plan on buying everything else direct from China. If you want their contact info let me know.

Hi Richard;
Great to hear back from you and thanks for sharing details of your system. In the interim since my previous post, I have taken the plunge and bought 25 pcs of the Trina 450w Tallmax panels. The prices were much higher, @ approx USD150/panel than what you paid, but it’s probably not unreasonable given the higher power output of these newer panels and compounded by the recent inflationary pressures on almost everything. This price is also FOB Manila, so includes the shipping cost from China.

Did more internet deep dives on the Growatt hybrid charger/inverters and learned that the Growatt design is allegedly ‘pirated’ from an almost identical model developed by MPP Solar, a Taiwan company. The feature-set and design of the MPP Solar unit is basically identical to the Growatt ‘clone’ and the pricing very similar, so I am opting to go with the MPP Solar product, given the good user feedback and my own positive experience with their responsive and knowledgeable customer support team. I’ve imported several other pieces of equipment from China previously and found that getting competent after-sales support (in english) is often a serious problem.

I have briefly looked at the Growatt 48V Lifepo batteries. However, I’m not sure which battery cells, which are the most important part of any battery, they use. Also gotta be careful with the product warranties on batterypacks… 48V batteries weigh more than 300 lbs (150Kg!) so shipping cost alone for warranty exchange would be very high, esp to/from China. If you live outside metro Manila, the cost of intercity trucking can also be exorbitant (as I have learned the hard way, living in Solano, Nueva Vizcaya). In fact the cost of (and hassle of arranging) trucking can represent as much as 50% of the product purchase cost, depending on your final location! (Where do you live in the Phils?)

Also be careful of the ‘fine print’ on the warranties. Some battery manufacturers provide only remote diagnostic support to help isolate the problem in a batterypack and will ship the replacement part(s) but its up to the customer to open up the pack and replace the defective part(s)! Not easy if you have little or no hands-on experience in building batterypacks.

These factors have motivated me to seriously look at locally available china-made batterypacks, such as the “Blue Carbon”. According to the suppliers, these packs use prismatic cells from BYD, which is well known and long established in the lithium battery market for electric vehicles. Despite the cells being ‘used’, they are tested and rated by BYD, to provide >2000 cycles at 1C discharge and >4000 cycles at 0.4C discharge rate. Also depending on the local seller, some offer local warranty service/exchanges. The local price of a 48V 200AH pack is approx USD1200. What price is a comparable Growatt model? I would appreciate if you could share your China contact info with me so I can do some due diligence on my own.

I’m about to purchase one BC pack to test it and will share my findings with you after I’ve gained some real world experience with it.

For anybody else reading this thread, I would welcome your thoughts, suggestions, advice on the MPP Solar hybrid inverters and the ‘used’ BYD batteries.

FYI I will be installing the system myself so it’s definitely gonna be a steep DIY learning curve!

Take care and let’s stay in touch.

1 Like

Hi, That’s a good price for those, WOW! What’s the warranty? We are in Santa Rosa, Laguna, just south of Metro Manila so we don’t have to deal much with local shipping and ferries, etc. That’s a good price for those batteries, I was expecting to pay about double that. Growatt has more than 2 types, the ones I was looking at, one type has a 10 year warranty but can only link to 800ah, about 3 times your cost, the others have a 5 year warranty but can link to make 1200ah, about double your cost. I need at least 1100ah to be safe at my maximum use overnight. Let me know how the first one works out. I’ve had good luck so far with the Growatt inverters, I use the split phase US style. I have an 8kw grid tie and a 12kw off grid. Both are working very well except I haven’t been able to get the new one to go online to the Shineserver. This latest Growatt inverter I bought from Grace Zhang, Xiamen Sweet Power Tech on Alibaba, she also has batteries she says are the same as the Growatt at a better price. I also have Amy Wan at Shenzhen Luyuan Technology Co, who has batteries as well, I am looking at cells from her. She is always on DIY Solar message board in The US and is highly recommended there, she is on Alibaba as well. I also use Future Green Technology for my panels, they also have other things as well, combiner boxes, inverters. The director there is Mr Shaw, he has helped a lot,, they have a new salesperson I don’t know well yet, but he is very nice and helpful. There is no communication problem at all with any of them, and they all get back to me right away.

1 Like

I just looked at some of those batteries on Lazada. I looked there before and never found any like these. There’s one place selling them in Batangas with a 5 year warranty for 62000P. That’s close enough for me to go over there and pick them up, the shipping is so expensive. Also I designed a simple adjustable mount system and found an easy way to find true south.