absorption 28.2V for 4h
equalise 31.46v for 2h *all days ? this simulate that last part that make the batts up to 31.46v bur will it use what current to do it
Do you think that i can use the equalise function to simulate that last stage ?
Not quite. Firstly, that last constant current stage that the exide charger does is current limited (for PzS it's 5A/100Ah, for your gels perhaps something different), this is to ensure that the battery doesn't gas too much during that stage. None of the renewable energy charge controllers will let you specify a current limit for EQ. So if you just program the FM to EQ at that voltage you might overcharge and overgas because of too much current.
Secondly, I believe the FM's don't first do an absorb before doing an EQ, they just go straight from bulk and attempt to reach the EQ voltage so you would end up spending much more time above the gassing voltage than is spent during the IUI curve of the exide charger. Also not good.
Honestly, I don't understand why gel batts would use the IUI curve. As I thought I understood it, that final "I" phase was there to mix the electrolyte and ensure the batt reaches 100% SoC. So why you would want to do that with gelled electrolyte is beyond me. Perhaps I have the wrong end of the stick with this curve
I've also been trying to replicate the IUI curve with the midnite classic and have come to the conclusion that it's not necessary. It's just a convenient curve for forklift batts because you can charge fast and get nicely mixed electrolyte at the end of the charge. It's also easier to determine when end of charge is reached, because you can just watch the voltage, and when it stops rising you're done. But it's not the only way to charge a forklift batt, and I think it would be detrimental to the health of the batt to follow that curve every day in an RE system when the battery is not actually discharged much at all. Unnecessary stress and voltages when the batt could very well be quite full already (> 80%).
The trusty "Battery Technology Handbook" compares IUI charging with IU (bulk-absorb. In forklift land there's no time for float) charging and just says that if you choose to use IU charging then you need to do a periodic EQ to mix electrolyte because the mixing isn't as good as with IUI charging. It also says that an advantage of IU charging is that you can parallel charge a bunch of different batteries at the same time. So I take some solace that IU is a charing method used by industry and not just peculiar to the renewable energy world.
In my opinion, you could do a normal bulk-absorb-float daily and then do an EQ at a lower voltage monthly. The reason for doing a lower voltage EQ is to try and limit the current. You're at a disadvantage because you can't measure the SG, so won't know for sure how your charging works out. So you're going to have to rely on the current going into the batt to determine when to finish absorb and EQ. Clear as mud
