Replacing batteries on my solar system

[Bozzydogg02]

My batteries have recently failed testing after being taken back under warranty, and now I have to pay to get them shipped back to me, which is pretty pointless as they’re not holding charge so I’m in the market for a new battery bank.

I had 5 110 ah ‘solarflex’ sealed 12v batteries and one ‘probatt’ 110 ah 12 sealed batteries, connected to 5 100 watt eco-worthy solar panels linked in series with a photonic universe mppt 50 amp 150v solar control charger. The batteries were connected together with 35mm hi-flex cable.

The system powers our tiny home (in the back of a sorn luton van) the electrics consist of a dual USB port, 2 led lights and a water pump all connected to a fuse board and a 2000/4000 watt inverter used to charge laptops regularly (once a day), occasionally charge a small vacuum cleaner, drill battery and sometimes power a fan or mini projector.

First where have I gone wrong? I figure there could be something wrong with my set up? Is my inverter too big? I guess that the batteries are just not the right thing for the job?

Second what batteries should I try next?

Bearing in mind I’m hoping to add a cool box/fridge, another USB port and a diesel heater to our set up this year. Also I have a 400w wind turbine and controller I am yet to add to the system.

I don’t really want to go with lithium due to safety and cost.

I’ve looked at agm (which the ones I had were sold as but I’m not sure about) I would definitely try this route if I could get some advice off someone who has them and uses them in a similar way to me on exactly which ones to get.

Traction batteries seem to be ticking all the boxes from what I read on the internet but again would really welcome advice from anybody using them.

I hope I haven’t waffled on too much and can get some advice on this!
Thanks!
Lewis

 

[Hedges]

Lead-acid has to be fully and properly charged on a regular basis, and not over-discharged or left at low SoC.
Having an inverter (or loads) shut off at suitably low SoC may be the biggest problem.
They can give 300 to a few thousand cycles depending on DoD.
I use SunXtender AGM for grid-backup, discharging to 70% DoD, but expect this to be infrequent.

LiFePO4 looks good for several thousand deep cycles, probably is appropriate for mobile application cycled daily. Also half the weight for same gross capacity, 1/3 to 1/4 weight for same usable capacity.
Need to be kept warm enough (above freezing) when charging.

Inverter to charge laptops? How about using electronics that runs directly off 12V?

For mobile application, you might want to keep inverter off most of the time. Some can be in standby, testing periodically to see if any loads connected. Higher end models consume less power.

 

[Bozzydogg02]

Thanks for replying!

I thought with the amount of solar panels and the decent controller they would of been getting fully charged on a regular basis, if this is not the case would reducing the amount of batteries help as I don’t think I need 660ah (330ah usable) but having say 4 give them a better likelihood of getting fully charged?
Yes my inverter shuts off at 10.8 volts but that’s only happened a handful of times during the winter. (Until this time where they were so drained that it wouldn’t even turn on).
Mine must of given up right around the 300 cycle mark then as I had them operating for about 14 months being used for about 10-11 months.

I have had a look for sun xtender online and can’t find a uk supplier, is there any?

LifePO4 seems great, although on the expensive side and also seems like opening a whole new can of worms to find which exactly would be best, do I go for a few cells? do I need a lot less than I had? And I don’t know if I can guarantee above freezing temperatures in the back of a van during winter, which would be the worst time for them to pack in.

Using electronics that run directly off 12v? Not something I’ve thought of before, would I just wire a normal plug socket to the batteries minus the earth? Would this save power significantly vs the inverter?

Thanks again