Re: SM Batteries

Dean Gillies

Hi Kent,
Correcting the problem ... the key things are:
1. Use the correct Abs voltage.
2. Use a low tail cutoff current.

it was difficult to find clear charge information from Crown. The attached Crown document indicates that the absorption voltage should be 29.0V. To my mind this still seems low, but it is 0.5V larger than you have been using in the past so will definitely help. 

You should use a tail current (INTO THE BATTERY) of 0.5A or less.  In this regard, it's important that your charging systems correctly recognise the current flowing into the battery only.
You need to ensure that the switch to float happens at the correct time.
You can check this by forcing the voltage back to 29V and manually checking the current into the batteries. It should fall below the tail current very quickly if the batteries are fully charged.
If you find that the batteries continue to take more charge, then reduce the tail current setting. Ideally, you want the tail current setting to be as low as possible but still reliably switch to float when batteries are full.
In the past I often used my generator for a short time in the morning to boost my lead batteries while they will accept a large charge, before letting solar take over for the slow end of the charge cycle.
maybe you can share your MPPT settings?

I've always thought of it as a double-edged sword.  It's intended to remove sulphate deposits from plates and mix up the acid. However this process also destroys your battery a little each time. I also don't like the possibility to create shorts with all the material that's removed from the plates. It has to go somewhere, but where does it end up ??  
I personally don't like it, and have used Gel and AGM's for so long that I have no practical experience so I don't know the answer to your question! Maybe others with experience of employing it can answer that.
How much should you equalise, how often etc??




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