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AGM charging

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poprock View Drop Down
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    Posted: 16 May 2017 at 8:59am
Hi, After ditching my Seamaster pretend deep cycle as recommended by members, but not being flush enough or confident in my skills level to use Lithium (other than for depression), I have changed to Sunstone 80AH AGM. A charging question about them. If I charge immediately after a run the seven in series batteries will charge very slowly, hovering at 12.7 to 12.9 for two to three hours. The BRB is disconnected, breaking the 84v circuit and each battery is monitored and charged separately. Rather than leave it overnight and risk overheating, I disconnected all chargers. Upon re-connection, all batteries reached 13v within ten minutes from cold. I know that lead acid should not be allowed to stand uncharged, but because of the heat generated from discharge and then re-charging immediately, what is the best procedure for AGM? I have researched several websites, the best being Battery University, and all seem to advocate similar charging procedures. Anyone like to add their 20c worth?
" A little foolishness now and then is relished by the wisest men "
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Johny View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Johny Quote  Post ReplyReply Direct Link To This Post Posted: 16 May 2017 at 12:05pm
A few questions.
You don't mention charge rate.
Are the chargers "smart" - in terms of reaching full charge then settling to a float voltage.
In either case a main consideration is not to overheat AGMs. Typical maximum temperatures are around 45 to 50 degrees C. This gets a bit difficult in hot weather.
What temperature are they "immediately after a run"?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote poprock Quote  Post ReplyReply Direct Link To This Post Posted: 16 May 2017 at 3:41pm
I'll get back 2 u shortly.
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poprock View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote poprock Quote  Post ReplyReply Direct Link To This Post Posted: 17 May 2017 at 8:43am
Hi Johny; Followed your suggestion of measuring temperature after a run. The two AGM easily accessed were 24C at 18C ambient. But the figure near the pack negative battery post was 111c(eBay thermometer). There was a loose connection at a fuse between the negative pack post and the lead to the controller. This was causing an ICE-type flat spot under acceleration. I will follow up your other suggestions but this one may well have prevented a serious issue. Thank you.

Edited by poprock - 17 May 2017 at 8:51am
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Johny View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Johny Quote  Post ReplyReply Direct Link To This Post Posted: 17 May 2017 at 8:53am
Originally posted by poprock poprock wrote:

This was causing an ICE-type flat spot under acceleration. I will follow up your other suggestions but this one may well have prevented a serious issue. Thank you.
Wow what an unintended bonus. I must admit I do a quick tour of my pack with work's infrascope about once a year or so but my current drain is way less than yours. The 6c rise sounds pretty good and certainly means you could usually charge immediately after a run - just not in really hot weather.
A lot depends on your chargers though...

PS: Not Jeff, John - but I answer to just about anything.

Edited by Johny - 17 May 2017 at 8:53am
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