Hi from Wales, UK. Looking for some help with a battery array for a proof of concept in my shed.

[wholetthesmokeout]

Hi everyone, sorry if this seems like a silly question, but I'm going round in circles trying to wrap my head around it...

I have managed to rescue a UPS (and a 240v battery array made up of 20 x 12v 9ah batteries in series) from the scrap pile and I'd like to set up a proof of concept with it to run a single socket and lighting ring in my shed. Now based on my first thoughts, I didn't think this was going to be too complicated having put 2 very basic solar systems in my last two vans...

I've already got the 63a RCD and MCBs for the wiring from the output of the inverter side sorted

I know these systems aren't great to be charged and discharged regularly as it will destroy the batteries that are currently installed...but for a proof of concept and the fact the batteries are probably on their last legs anyway, I'm prepared for them to be ruined.

My question is this... the two units, the inverter and battery pack are connected with a custom cable between them and as I'm not planning on hooking up the inverter part to the mains 240vac for charging, I need to work out the best way to charge the battery array inside the unit that holds the batteries.

I know that I need a charge controller to charge them, but I am not sure how best to connect to the batteries to charge them as efficiently as possible or if there is a specific type of charge controller that would be better than another. I have used MPPT controllers in the past. I've read lots about charging a few batteries (3 or 4) in series and parallel to charge them, but nothing that comes close to charging 20 batteries at once.

If the proof of concept works, I'd look to swap out the flooded batteries and swap them with some better suited batteries to handle the charge cycles...

Any pointers on how best to approach the charging from solar for such a set up would be very much appreciated.

Thanks and sorry about the huge post and I hope I included enough info.

All the best, from Wales, UK.

N.

 

[Leeds]

a 240v battery array made up of 20 x 12v 9ah batteries in series

Having a 240vdc system will be difficult to charge, maintain and use.

If I had that specific pile of batteries lying around I'd either put them in a 20p configuration to make a 12V 180AH battery or I'd put them in a 2s10p configuration to make a 24V 90AH battery.

There are plenty of charge controllers that work for 12 or 24 volts. The 12v system would of course be the easiest to maintain as they would always be in balance, the 24 volt system would require you to check the voltage of both halves of the back every now and then to ensure they're balanced.

 

[wholetthesmokeout]

Having a 240vdc system will be difficult to charge, maintain and use.

If I had that specific pile of batteries lying around I'd either put them in a 20p configuration to make a 12V 180AH battery or I'd put them in a 2s10p configuration to make a 24V 90AH battery.

There are plenty of charge controllers that work for 12 or 24 volts. The 12v system would of course be the easiest to maintain as they would always be in balance, the 24 volt system would require you to check the voltage of both halves of the back every now and then to ensure they're balanced.

Thanks for taking the time to answer. I have come up with a plan... I'm trying to keep the UPS and battery packs in one piece.

That said though because I can get hold of some spare batteries, I'm going to make a smaller 48v set up with a smaller inverter to charge the bigger battery packs. I can then use that inverter on another project further down the line.

Thanks again for taking the time ?

 

[Substrate]

Using used UPS agm batteries, all in a non-consistent state is asking for disaster at the outset.

Far better would be to use a single commonly available Leisure-Battery.

In either case, to ensure you are starting out on the right foot - and here I go again with the sales pitch - FIRST get hold of a Tecmate / Optimate 6 Ampmatic diagnositic charger.

Those should be extremely easy to find on that side of the pond. This way you can quickly cull through all those various batteries, and be able to match up the best of them. Some are likely total trash. The Optimate will quickly inform you of this. Other chargers won't. Worth the quid.

And of course, it will keep your vehicle battery in fine shape.

If you don't do this, then all the help in the world will be based solely on speculation, and your project is more of a goof than anything substantial.

 

[wholetthesmokeout]

Using used UPS agm batteries, all in a non-consistent state is asking for disaster at the outset.

Far better would be to use a single commonly available Leisure-Battery.

In either case, to ensure you are starting out on the right foot - and here I go again with the sales pitch - FIRST get hold of a Tecmate / Optimate 6 Ampmatic diagnositic charger.

Those should be extremely easy to find on that side of the pond. This way you can quickly cull through all those various batteries, and be able to match up the best of them. Some are likely total trash. The Optimate will quickly inform you of this. Other chargers won't. Worth the quid.

And of course, it will keep your vehicle battery in fine shape.

If you don't do this, then all the help in the world will be based solely on speculation, and your project is more of a goof than anything substantial.

Thanks, I hear what you're saying... I have already done the leg work and checked the status of each battery using a similar tester.

If I can charge the battery box via the ups then it also has a BMS which mitigates the batteries being all over the place.

This isn't going in a vehicle so won't affect any other battery... but for what I want to test, it is an almost free source of a 6000w supply of juice. I'm aware this isn't the best use of agm batteries and thought I'd mentioned that in my post.

It was more a question of how to charge the battery box using solar.

I know now how I'm going to achieve that. I will have a 48v system powering a smaller inverter that will plug directly into the mains input of the ups. This will enable all of the features of the BMS etc to properly charge and maintain the batteries (for their limited life expectancy). It will also naturally kick in the power on function of the ups so when it no longer has mains input (when there's not enough daylight), it will automatically provide the power via the battery box.

I know this sounds a bit like a bodge job, but for the sake of testing, it's not costing my anything other than a 63a RCD and a couple of MCBs to try it before spending huge amounts on a better battery system and inverter.

Thanks again for your input, much appreciated that you took the time to reply.