Help, not reaching 100% change

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Help, not reaching 100% change

Postby TsaTsa2CV » Tue Oct 20, 2015 11:18 pm

Hi everyone,
After 5 years of trouble free running our 5.55kWh, 24V Latronics 4024, Raylite 1680Ah with a couple of Apollo 80HV charge controllers we hit our first hurdle. Normally, for 3/4 of the year batteries reach float and 100% charge by 11am most days .We seldom discharge more than 10%. However, over the last few days I noticed that the charge controllers are in float, but indicating batteries only 95% of charge at 10am on a sunny day.
I checked the battery setup on MASTER: Absorb=29.6V for 02:00h, Float=27.6V and on SLAVE: Absorb=29.5V for 02:00h, Float=27.7V. By the end of the day the indication was that we had only 97% charge in the batteries.

Does anyone have any idea what could be going on? Batteries all test OK and they had an easy life to date with no deep discharges and the occasional equalization charge.
I would appreciate any suggestion to restore the charge regime to normal 100%!

Thank you in advance
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Re: Help, not reaching 100% change

Postby Gordon-Loomberah » Wed Oct 21, 2015 8:31 am

What NET end absorb amps do you have now, and also at this time last year, at the end of your 2 hours absorbing? If the batteries are in reasonably good condition it should be under 20A.
Does your SOC indicator self-calibrate, or do you have to enter some sort of efficiency parameter?
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Re: Help, not reaching 100% change

Postby TsaTsa2CV » Wed Oct 21, 2015 4:51 pm

Thanks for your replay Godrdon,
On checking the system this morning (overcast day and finally 3mm of rain) that the SOC was 89% and the master was in float, the slave in absorb. Normally the other way around with the slave first to float and the master bringing the SOC to 100%. I think the gremlins must have been at work as nobody ever touches the system but me! I rang the importers and we went through the setup noting that the system was no longer in a master-slave relationship, for whatever reason?
After powering down the system we went through the setup of master - slave again and time will tell if it's back to normal, fingers crossed.
I don't know if the SOC indicator self-calibrates, it indicates as 96% , whatever this tells me?

Cheers and I'll fill you in if it's not back to the way it worked for the last 5 years!

Daniel
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Re: Help, not reaching 100% change

Postby Gordon-Loomberah » Wed Oct 21, 2015 6:13 pm

If your load is fairly low, either one of the charge controllers should be able to bring you to float. Are the different voltage settings you have compensation for inconsistencies in the charge controllers' internal volt meters? If you have them set as master and slave, perhaps the settings in the slave don't matter?

Anyway, I'd still be interested to know what your net end absorb charging current is. If it is still decreasing at 2 hours, it might be worth extending it a bit.
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Re: Help, not reaching 100% change

Postby TsaTsa2CV » Thu Oct 22, 2015 9:52 pm

Well, I'm happy to report that the system is running again as master and slave and reaching 100% charge. I have lowered the absorb voltage a little to 29.4V at least for the hotter season. We consume around 7-9kWh/day running Sanden heatpump every day (using less than 2kWh/day for two people) :idea: . Maybe up to 15kWh when the aircon is running all day on hot days.
I'll check the end absorb current when we return from down town Melbourne and let you know.
With the slightly different voltage settings on the slave I tried to stop it going into float too soon in marginal overcast weather. It seamed to work.

Thanks again
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Re: Help, not reaching 100% change

Postby jimbo » Tue Oct 27, 2015 3:46 pm

I have the same batteries. I would say 2 hour absorb is not long enough as mine regularly need 3-3.5 hours if they have discharged down to 88=90% SOC. Today they absorbed for 2 hours but probably only used 3kw over night. My batteries switch t float when absorb amps drop to around 8 amps.

Also Raylite recommend a maximum absorb voltage of 29.4 with temp compensation as well as equalisation every 20 days (i stretch that out)
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Re: Help, not reaching 100% change

Postby TsaTsa2CV » Wed Oct 28, 2015 9:16 am

Thanks Jimbo, all looks good again reaching full charge. I've set absorb voltage to 29.4 and extended it to 3h and yes, we have temp compensation set up.
I check batteries at the end of each month topping up electrolite maybe 3-4 times a year and record SG.
It is interesting that the same cells record a higher SG of 1300! The rest are always 1280/1290 and voltage range between 2.47V and 2.54V.
I do a equalization charge about every 30 days.
We hope to get a good long life out of them before replacing them with lithium iron batteries or whatever they will have made available by that time. This year the genset did less than 10h and mainly for pumping up water to optimistically make space for elusive rain. Starting to get concerned now and sick of blue sky!
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Re: Help, not reaching 100% change

Postby jimbo » Wed Oct 28, 2015 9:21 am

Mine are 9 years old now and have always had a high sg similar to yours. They are starting to sag more under higher loads but still power the house fine. I bought the house when they were 7 years old and they had been over charged the whole time.
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Re: Help, not reaching 100% change

Postby davidg » Wed Oct 28, 2015 1:41 pm

jimbo wrote:I bought the house when they were 7 years old and they had been over charged the whole time.

Better than one lot I had to replace for a customer that spent a large proportion of roughly 8 years being chronically under-charged for long periods. Not the customers fault, unfortunately training and or a manual on how to look after them properly was not provided as part of the original installation. I suspect if they had been looked after within the battery spec/design requirements they likely may have been in service today.
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Re: Help, not reaching 100% change

Postby TsaTsa2CV » Fri Nov 13, 2015 9:53 pm

Hi Gordon,
I finally got around to check the end absorb charging curren. It is 7 amps. I guess it indicates that the batteries are still in good nick! All is working well again reaching float every day. All we now need is rain, lots of it :P
I understand that to do an equalization charge too often shortens the life of the batteries. 20 days appears very shortl. What is the sweet spot?
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