<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Steve reminded me of something, probably because it is not very common. If you are recharging at 1C or greater rates, the Absorb cycle will need to be longer if you want to return all energy to the battery. Example: For a 300AH battery, 1C would be 300 Amps or over 16kW for a 48V bank. <div class=""><br class=""></div><div class="">Since it\u2019s not economical to build a PV system that can fully charge from 100% DoD in just 1 hour of full sun, it\u2019s not too likely you will use 1C charge rates. If you are generator charging, this may be true, in fact I recommend charging at 1C (or max the brand will allow) to reduce generator run time.<div class=""><div class=""><div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; text-decoration: none;"><br class=""></div><div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; text-decoration: none;">Larry Crutcher</div><div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; text-decoration: none;"><br class=""></div><div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><br class=""></div><br class="Apple-interchange-newline">
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<div><br class=""><div class="">On Dec 1, 2021, at 2:09 PM, Steve Higgins <<a href="mailto:steve@surrette.com" class="">steve@surrette.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class="">I have found this to be true as well, especially when multiple LFP battery blocks are in parallel . I like to see the charge rate around the C2 to C8 Rate... the lower the charge rate the longer the absorb. On the LFP's we advise around 20-60 mins absorb time again depending on the amount of current availability, and quantity of parallel connections. <br class=""><br class="">With the MX60 you can adjust the float voltage to the 3.65vpc, and set the timer for the rest of the solar day to ensure the batteries are getting balanced... <div class=""><br class=""><div class=""><br class=""></div><div class=""><div class=""><div dir="ltr" data-smartmail="gmail_signature" class=""><div style="float:left;padding:1px 10px 0 0" class=""><a href="http://www.rollsbattery.com/" target="_blank" class=""></a><a href="http://www.rollsbattery.com/" target="_blank" class=""></a><a href="http://www.rollsbattery.com/" target="_blank" class=""></a><a href="http://www.rollsbattery.com/" target="_blank" class=""></a><a href="http://www.rollsbattery.com/" target="_blank" class=""></a><a href="http://www.rollsbattery.com/" target="_blank" class=""></a><a href="http://www.rollsbattery.com/" target="_blank" class=""></a><a href="http://www.rollsbattery.com/" target="_blank" class=""></a><a href="http://www.rollsbattery.com/" target="_blank" class=""></a><a href="http://www.rollsbattery.com/" target="_blank" class=""></a><a href="http://www.rollsbattery.com/" target="_blank" class=""></a><a href="http://www.rollsbattery.com/" target="_blank" class=""></a><a href="http://www.rollsbattery.com/" target="_blank" class=""></a><a href="http://www.rollsbattery.com/" target="_blank" class=""></a><a href="http://www.rollsbattery.com/" target="_blank" class=""></a><a href="http://www.rollsbattery.com/" target="_blank" class=""><img src="https://imgur.com/hENEoQQ.png" alt="" style="padding:3px 0px 0px 10px;float:left;margin-right:10px;width:98px;height:115px" class=""></a><div style="font-style:normal;font-variant:normal;font-weight:bold;font-stretch:normal;font-size:14px;line-height:20px;font-family:Arial,Helvetica,sans-serif;margin:0px" class=""><font color="#bb1a1d" class="">Steve Higgins \u22c5
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<div class="">
<br class="">
Thanks Larry.<br class="">
<br class="">
The information to stop when absorb voltage was reached is like, 10
or more years old and so I<br class="">
don't know if that voltage reach and stop charging algorithm is
still used by any BMS's.<br class="">
<br class="">
This is probably why we had to add a logic input to tell the
controller to stop charging from the BMS.<br class="">
<br class="">
After the 0.3 hours at Absorb for balancing (which makes perfect
sense for a BMS), does the MX/FM then<br class="">
go to float at 3.65V per cell after that ?<br class="">
<br class="">
Does your systems just restart a new bulk/absorb cycle the next
morning or do you also do a Re-Bulk if<br class="">
or when battery voltage falls below a certain point ?<br class="">
<br class="">
Also, listening (reading) chat here on what might be needed that may
not have been addressed by<br class="">
Li battery, BMS and/or charge controller manufacturers.<br class="">
<br class="">
<br class="">
Thanks,<br class="">
boB<br class="">
<br class="">
<br class="">
<br class="">
<br class="">
<br class="">
<div class="">On 12/1/2021 12:03 PM, larrycrutcher
wrote:<br class="">
</div>
<blockquote type="cite" class="">
<div class="">If you stop charging a Li-ion battery when the CV
(absorb voltage) is reached, you may reduce or stop the needed
cell balancing time. We have had customers develop unbalanced
series cells from continuous undercharging. Because of internal
cell resistance, one cell will always reach saturation before
others in the group. This can happen at less than 1mv
difference. The more unbalanced a group of series cells are, the
sooner one cells voltage will spike causing over voltage events
at a lower terminal voltage. </div>
<div class=""><br class="">
</div>
<div class="">Our Li batteries (Elite Power Solutions-GBS and
LiFeBlue) can be held at 3.65Vpc continuously, no problems. We
have customers using both MX and FM controllers for 8 years now.
Our recommended setting for the Absorb timer is 0.3 hours. This
allows for cell balancing and for the capacity meter to
recalibrate. Some chargers will stay at CV for several hours. No
problems doing this either as long as cell voltage is lower than
3.8V (LFP chem.).</div>
<div class="">
<div style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none;" class=""><br class="">
</div>
<div style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none;" class="">Larry
Crutcher</div>
<div style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none;" class="">Starlight
Solar Power Systems</div>
<div style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none;" class=""><br class="">
</div>
<br class="">
</div>
<div class=""><br class="">
<div class="">On Dec 1, 2021, at 9:38 AM, <a href="mailto:bob@midnitesolar.com" target="_blank" class="">bob@midnitesolar.com</a>
wrote:</div>
<br class="">
<div class="">
<div class=""> <br class="">
<br class="">
Depends on the requirement for the BMS.<br class="">
<br class="">
Usually, but not 100% always, the requirement is to get the
voltage up to "absorb" and then stop charging.<br class="">
<br class="">
Just set the min and max times very low, like 1 minute and
that should satisfy that one.<br class="">
<br class="">
I do not remember if the MX60 had a Re-Bulk setting but I
think it did ?<br class="">
<br class="">
The MX did not have a logic input for turning it on and off
of course. OB had a communications<br class="">
device that converted their communications protocol to
Modbus or Ethernet I think it was which<br class="">
may (or may not) be able to make it work.<br class="">
<br class="">
Could always buy something newer and keep the MX60 as a
spare. <br class="">
<br class="">
boB<br class="">
<br class="">
<br class="">
<br class="">
<div class="">On 12/1/2021 9:10 AM, frenergy
wrote:<br class="">
</div>
<blockquote type="cite" class=""><p class="">boB,</p><p class=""> Interesting...Sounds like this is
not a candidate for L-ion batteries.</p><p class="">Bill<br class="">
</p>
<div class="">On 11/30/2021 10:47 PM, <a href="mailto:bob@midnitesolar.com" target="_blank" class="">bob@midnitesolar.com</a> wrote:<br class="">
</div>
<blockquote type="cite" class="">
<br class="">
Hi Bill....<br class="">
<br class="">
As I remember, the min is of course... Minimum time in
Absorb.<br class="">
<br class="">
Max is maximum time in absorb but depended on how long
it took to get from Bulk MPPT to that Absorb voltage.<br class="">
<br class="">
So if it took 3 hours to get to Absorb that morning and
you had t set for Max 2 hours, it would Absorb for 2
hours.<br class="">
<br class="">
If it only took 1 and 1/2 hours to reach Absorb voltage,
the MX60 would Absorb for 1 and 1/2 hours.<br class="">
<br class="">
It worked "OK" but these days I would probably just set
it for min of some 2 or 3 hours and then a max could be
the same<br class="">
time or longer for FLA batteries.<br class="">
<br class="">
boB<br class="">
<br class="">
<br class="">
<br class="">
<div class="">On 11/30/2021 7:16 PM,
frenergy wrote:<br class="">
</div>
<blockquote type="cite" class=""><p class="">Yes, the old one, not the FM. This oldie
had an interesting way to set the absorption time.
You would set the "min" time (in minutes) and you
would set the "max" time (in hours, you have to set
it to 1,2,3 or 4 hours).</p><p class=""> I need to know if I set the
"min" to 10 minutes and the "max" time to one hour
or two or three or four, how long will it stay in
absorb?</p><p class=""> I called Outback and Megan
there didn't know how this old fart works,
apparently tech support isn't supporting <strike class="">us</strike> their old relics.<br class="">
</p><p class="">Bill</p>
<pre cols="72" class="">Feather River Solar Electric
Bill Battagin, Owner
4291 Nelson St.
Taylorsville, CA 95983
530.284.7849
CA Lic 874049
solar powered since 1982
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