What is the best way to prevent the batteries get killed?

[paulcheung]

I was plan to setup a small system in a small shop, but the plan was changed, wife no longer want the solar at her shop. I already bought some of the parts. So I plan to use at one of my fish pond. The pond use one water pump used to run 24/7. but as the electricity get more expensive in Jamaica I have to shut it down a period of time during the night. The pump is 125 watts. I also have one air pump that is about 5 watts that I run 24/7 to keep the water bubble run on a different circuit.

The system is plan to run as long as possible each day, but by calculation it won't run 24/7.

2 240watts solar panels
1 Xantrex Pro Watt SW1000 1000watts pure sine 12volts to 120volts inverter.
1 Tracer 4210 40amps mppt 12/24 volts charge controller.
2 225 Amps 6 volt deep cycle battery

location Mandeville Jamaica. (plenty cloud pass in the day even no rain)

The inverter LVCO is hard coded preset at 10.5 volt. which will kill the battery in a very short time. the original plan for use this inverter with human intervention so should be fine, but now it is to run at the night so no human intervention is available.

What can I do to prevent to batteries get kill by over discharge? at a reasonable price? the pump can be shut off few hours at night without problem. I am thinking may be I should use a longer and smaller pair of battery wire to have a volt drop about 0.5 volt so the inverter sense the volt for 10.5 volt and the battery actually have 11volt? The load is light so it won't have the large fluctuating voltage that make the situation worse.

Thanks

[Sunking]

2 225 Amps 6 volt deep cycle battery

Listen to your wife.

Just based on the batteries without knowing what kind they are I have to assume golf cart batteries. If you discharge them 50% DOD per day you will only get about 2 years out of them if you ar elucky and can keep them cool and dry. Good luck with that in Jamaca Mon.

FWIW with a 125 watt pump to discharge to 50% is about 6 hours run time.

[paulcheung]

Listen to your wife.

Just based on the batteries without knowing what kind they are I have to assume golf cart batteries. If you discharge them 50% DOD per day you will only get about 2 years out of them if you ar elucky and can keep them cool and dry. Good luck with that in Jamaca Mon.

FWIW with a 125 watt pump to discharge to 50% is about 6 hours run time.

Is there any other reason that the battery only be able to last 6 hour run time on 50%DOD? because it is 225amps @20 hour rating which it will draw 10.5amps. anyway the parts are bought already and the battery is relatively cheap @12,000 each so if I can get two years out of them I will be satisfied. when I can determine the length of the running time I think I will put a timer there to shut down the pump at x amount hour so it won't discharge to 100%DOD. the battery is more likely US Power 6volt 225amps golf cart battery.

Thank you Dereck.

[inetdog]

What can I do to prevent to batteries get kill by over discharge? at a reasonable price? the pump can be shut off few hours at night without problem. I am thinking may be I should use a longer and smaller pair of battery wire to have a volt drop about 0.5 volt so the inverter sense the volt for 10.5 volt and the battery actually have 11volt? The load is light so it won't have the large fluctuating voltage that make the situation worse.

Thanks

Absolute cheapest solution is a mechanical timer (like spring wound) that you set for a number of hours based on how well charged the batteries got during the day.

Your idea of increasing the voltage drop is actually sort of possible. But watch out that the inverter does not try to turn back on again automatically when it sees the open circuit voltage go up. If it requires a manual reset or the reset voltage is high enough you will be OK.

[paulcheung]

Well that cheap inverter doesn't turn back on automatically anyway. I might do that or I will use one of the count down timer and set the time for either 4 hour or 8 hours, I also try to get a 12 volt DC pump to use instead using the inverter, so it will cut out some of the energy expense the inverter carry.

Thanks.