AC-DC Charger for Renogy 12V 100Ah Smart Lithium Iron Phosphate Battery - RBT100LFP12S

roguesolar

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Oct 26, 2021
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The Renogy Manual states to charge these batteries at 14.4vdc, (which Renogy does not sell). Renogy Technical Support was more specific, saying find a charger with this algorithm:

Equalization voltage: no equalization
Boost/bulk voltage: 14.4V
Float voltage: no float stage
Boost return voltage: 13.2V
Under voltage warning: 12V
Under voltage recover: 12.2V
Low voltage disconnect: 11.0V
Low voltage reconnect: 12.6V

Does anyone know of a AC-DC charger that will support this charge algorithm? I have two of these in parallel and would like a charger that would support between 30 and 60a (most any amperage will be helpful) for installation in a Camper Van. This will be for power when adequate solar isn't available..
 

sunshine_eggo

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The Renogy Manual states to charge these batteries at 14.4vdc, (which Renogy does not sell). Renogy Technical Support was more specific, saying find a charger with this algorithm:

Equalization voltage: no equalization
Boost/bulk voltage: 14.4V
Float voltage: no float stage
Boost return voltage: 13.2V
Under voltage warning: 12V
Under voltage recover: 12.2V
Low voltage disconnect: 11.0V
Low voltage reconnect: 12.6V

Does anyone know of a AC-DC charger that will support this charge algorithm? I have two of these in parallel and would like a charger that would support between 30 and 60a (most any amperage will be helpful) for installation in a Camper Van. This will be for power when adequate solar isn't available..

If powering via solar, and you want to power your loads with solar rather than allow the battery to cycle several times a day while solar is available, specify a float of 13.6V. The float voltage establishes the floor below which the SCC wont allow the battery to drop. If you're just charging them up, and there is no load once full, no float.

Progressive Dynamics (PD) and Powermax PM3 models make suitable AC-DC charger options in those amperage ranges. PD requires you purchase a cheap plug in device that establishes the desired charge profile. They have lithium ones. The PM3 is pot adjustable and defaults to 14.6V charge, 13.8V absorption and 13.2V float.
 

fratermus

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Progressive Dynamics (PD) and Powermax PM3 models make suitable AC-DC charger options

Since OP has solar and is able to supplement with shore power sometimes, what is your take on a smaller, simpler converter that just puts out steady moderate voltage (maybe 13.2v - 13.4v)?

My first-draft thinking:

  • solar is present and can charge to higher voltages if/when desired. No need to pay for a staged smart charger.
  • converter would hold the floor steady and give solar a leg up in challenging conditions
  • if OP is going to be on the shore power for more than a few hours a lower-current converter could charge the bank at gentler rates, hold gentler SoC, and be less expensive
  • in the absence of meaningful solar harvest the bank could sit at these lower voltages for long periods without overcharging


The Renogy Manual states to charge these batteries at 14.4vdc, (which Renogy does not sell).

Rogue, if you are partial to Renogy gear and it's not time sensitive, they have an AC LiFePO4 charger for preorder. The preorder language is still there in some places and gone in others, so it may have just become available in the last few days. Dunno.
 

roguesolar

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Since OP has solar and is able to supplement with shore power sometimes, what is your take on a smaller, simpler converter that just puts out steady moderate voltage (maybe 13.2v - 13.4v)?

My first-draft thinking:

  • solar is present and can charge to higher voltages if/when desired. No need to pay fo.r a staged smart charger.
  • converter would hold the floor steady and give solar a leg up in challenging conditions
  • if OP is going to be on the shore power for more than a few hours a lower-current converter could charge the bank at gentler rates, hold gentler SoC, and be less expensive
  • in the absence of meaningful solar harvest the bank could sit at these lower voltages for long periods without overcharging




Rogue, if you are partial to Renogy gear and it's not time sensitive, they have an AC LiFePO4 charger for preorder. The preorder language is still there in some places and gone in others, so it may have just become available in the last few days. Dunno.
That charger is rated at 14.6vdc which would violate Renogy's Lifepo4 Battery user manuals. I'm still looking for a third party lifepo4 charger rated at 14.4. The Victron IP67 (25a) might work, but as I read it's manual, it is not clear if I can program it to limit the voltage to 14.4vdc. I may need to find a good Victron product expert to answer the question. One caution I see is Victron doesn't support Renogy batteries. :-(
 
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fratermus

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I'm still looking for a third party lifepo4 charger rated at 14.4.

[more experienced posters please fact check me on this]

We may have more downward flexibility with charging voltage. Off-Grid Garage did some tests that suggest at moderate charging rates (C/5, or 20A for 100Ah battery) both of the following will reach ~100% State of Charge:
  • 13.6v (3.4v per cell) with a few hours absorption at that voltage. Being on shore power probably makes these extra hours No Big Deal.
  • 14.0v (3.5v per cell) with zero absorption (charge-and-stop)
This may widen the pool of chargers you can select from.

Anecdote: my solar charges the bank at a similar rate and my observations line up with his testing. I want a little less than 100% SoC, so lately depending on solar conditions at my campsites I either charge 13.6v with a couple hours absorption, or 13.8v charge-and-stop.

As a bonus lower charging voltages tend to help with cell balance. The most recent 13.8v charge-and-stop I looked at (floating at 13.4v):
Screenshot_2021-11-10-12-46-16-618_com.jiabaida.bms.jpg


TL;DR: [on grid power] a charging source between 13.6v and 14.4v will get the job done.
 

roguesolar

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This is very interesting! Both the Off-Grid Garage and your BMS allowed cell level monitoring (giving a real good view of the internal battery). Since my batteries are still in the box and I have not purchased either their BT-2 or Smart Battery Monitoring screen, I can't see inside. I wonder how much visibility Renogy will give into the battery. I also wonder how much the Renogy BMS will interfere with such a pure simple charge? This is certainly worth a test! Hmmmm..... do I purchase the load tester and see if I can duplicate the Off-Grid Garage test on the Renogy? Since Will Prowse never finished the test of this battery .... maybe he will read this and do the test for all of us. :)
 

fratermus

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I wonder how much visibility Renogy will give into the battery

Pages 13-17 of the smart battery monitor's manual give an overview of what data is available. Voltage, current in/out, estimated state of charge, etc. Any warnings and active protections, which could be quite useful to see what's stopping the party. Also easier to install than a shunt: click it into the socket instead of rewiring stuff. BTW, when I looked at the product page on the Renogy site it said it was on sale right now.

At first glance it looks like the BT dongle watches the controller rather than the battery proper. If so, the monitor looks more useful than the BT dongle for watching the battery. I don't have any Renogy gear on hand so this is just looking at the docs rather than personal experience.

I also wonder how much the Renogy BMS will interfere with such a pure simple charge?

Minimally, I'd think. The BMS is more like a guardrail that keeps us from going off the cliff. If we stay well-centered in the lane (moderate charging, discharging, and temperature) we won't experience much contact with the guardrail. Flawed analogy but perhaps a useful one.

The folks on the DIY side and folks like Will who do teardowns have direct access to the components and can do a lot of testing we can leverage for free. As long as my ready-made battery meets my needs I'm not going to do any heroic testing on it. I live off-grid so if I took my battery offline for testing I'd be sitting in the dark. :)
 
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