building up battery bank

[m1cdq]

Im setting up a battery bank for emergency use mainly for ham radio use

Im in the UK   I've enclosed a basic diagram to show what i have so far

Ive 3 banks of batteries

bank 1 are 33ah

bank 2 are 40ah

bank 3 are 55ah

They are being float charged at moment via a 25amp dc supply at 13.8 v

I intend to keep them  charged by using the grid electric but later I plan to add solar panels for emergency charging as well as my generator

The output of my bank are all connected together via fuses  and CP3-4 and then to my 12 supply rail in my shack via another 25 amp circuit breaker

The Reason Im setting this up is due to the recent flood over here and power went of in some areas

I can add to the bank over time As im getting the batteries free. as they are comming from mobility scooters.The batteries are used but they are taken out of service either after 9 months or 12 months as they are done under contract. and new one replaced

the batteries are wired for 12v output.  what size panels would i need to be looking at

to keep them charged for standby use at moment  the ampmeter  is just showing a little over 1/2amp charge going to batteries. but what would i be looking at to charger them for a 20% dishcharge

bank 1 total 132 AH

bank 2 total 160 AH

bank 3 toatl 220 AH

so i presume ive a total of 512AH

I know the true figure will be lower as they are used

all batteries are Sealed Lead acid Batteries

any ideas or pointers

[PaulJ]

   Your 25A power supply should do the job provided it's current limited - a 500Ah battery discharged 20% will try to draw an initial current way higher than that. If you're running it off a generator, tweak the voltage up to 14 - 14.1V for the first couple of hours if you can, it will speed up the charging process (check the battery manufacturers specs to confirm this, SLA's are very sensitive to overvoltage damage).

   Without knowing your climate and likely power usage, it's impossible to know how much solar you need. In my sunny part of the world I could probably get away with a 40W  panel most of the time for standby use, a small generator is probably the cheapest solution for a reliable backup.

   Paul.

[m1cdq]

I plan to build another power supply just for the batteries

the idea is  mains to power supply 12 to a change over relay  so when main goes off the relay will  change over to solar  to keep them topped up  but when charging juice is needed  i will connect the power supply to  genny  as the genny has enough 240vAC to run power supply  but the genny dose not have enough 12v dc to charge batteries

Im on the east coast of england  we not get that many sunny days but mainly cloudy days

[PaulJ]

   Well, that would work but it's not a very efficient use of your solar input.

   Why not hook the solar up permanently with a suitable regulator, and use the grid / generator as backup for cloudy periods or heavy usage?

   Paul.

[AbyssUnderground]

This would be a good idea since Ham Radio's don't even use that much power, maybe an amp or so on receive, which is what most people do most of. Transmitting, OK you might go up to 5-10A, maybe more depending on your output power, but then as a Ham you should be running as little power as possible to reach your recipient. :-)