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diy solar

Newbie. SCC compatiblity with LiFePO4

roan

New Member
Joined
Aug 6, 2021
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Hi all,

(Forgive the long and winding ramble!)

I've inherited a non-completed Solar Install. My Dad was making a bus to rv conversion, and it got held up. 6 years later, the guy who was going to set up the electrics has shut shop... but Dad has all of these parts. All that was missing was the batteries, but it was assumed (at the time) AGM would be used. The time has come to finish the install and I've done the wiring, mounted the panels and components, etc, etc. But, still without any batts (I've been using 12v Lead Acid to test the system).

So, I've been lurking here, watching Will's vids for a few weeks now, coming up to speed with everything lipo, and was getting really excited about DIY'ing a 280ah 12v lipo and was reading up about float and bulk charging...which caused me to re-read the SCC manual (which also has a DC-DC converter) to see what it said.

The problem/question:
The SCC (and the DC to DC part) allows me to set Bulk and Float settings. No problems there...
But I read in the forums here that lipo hate Float... I assume that's correct...?
But this thing is a multi-stage charger and can only set the two settings. I can't set any absorption time, etc, etc.
I found an updated copy of the manual for the controller and it says:

"The solar controller may only be used in PV systems for charging Lead-Acid type batteries. This includes: SLA, VRLA, Lead-Calcium, AGM and GEL."

(My hard copy of the manual doesn't have this, but it's *old*).

It also says it does "Multi Stage Charging with Timer Protection".

The device in question is a Voltech SCM030, it's a 50V 30A MPPT and DC-DC charger for 12v batts only.

PS: I've set the the DC-DC part to be wired to the 24v bus (aka car) system (the DC-DC part has cut in and cut out voltages, which I can set to sense alternator 'ON'). I know Will is non-fanatical about this type of setup....but hey ;-)

I was wondering if I can or can't use lipo on this SCC? I was under the impression that lipo could be used as drop in replacements?
If I can use it, I presume the default Bulk charge setting of 14.2 could be changed to 14.6. What about the float level?

Here's the manual for it (Voltech SCM030):

(also the same manual is attached to this post)

Any help or advice would be welcome.
Thanks all, especially for your patience!
 

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As an update... I was just watching Will's interview with Battleborn CEO (it's chock full of great info, thanks guys!) and at around the 13 minute mark or so, the CEO mentions how a float between 13.4 and 13.8 is fine, and that most Lead Acid systems float at 13.6 which is perfect...


BUT... someone a if someone with a bit better knowledge than my ability to watch videos would be really helpful!

Thanks!
 
device in question is a Voltech SCM030
That looks suitable to an extent. The bulk and float values are programmable which is useful. What is not clear is how long the unit stays in bulk mode with constant voltage before falling to float. Over 25 deg C the float voltage is decreased by -20mV/deg C, perhaps not a great concern. Its also not clear what condition causes the charger to re-enter the bulk stage if there is load on the battery.
You should be able to confirm the absorption, constant voltage phase period, if it exists, with a simple test using the LA batteries.

The Battleborn battery is designed as a drop in replacement thus the selling points are that most existing chargers can be used. With a hobby built battery using large format cells a less stressful charge regime will be beneficial.

Using a bulk voltage of 13.8 or 14 volts will charge the battery to around 98% capacity and higher with some absorption time.
Any float voltage over 13.4 volts will keep the battery at full capacity. I suggest starting with 14.0 volts bulk and 13.5 volts float

Once you have the system built and running, tests with different bulk and float voltage settings should allow you to fine tune the system performance.

Mike
 
Many thanks Mike, especially for how to attack the problem of making sure the system will be sound!
 
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