Batteries: AGM vs LiFePO4

[tentcamper]

Agm, everything I have read is copatable with a flooded cell charger.

I would not plan on changing the converter or solar controller, unless you don't like the one you have.

[Bailey'sMom]

Still researching ....

So if I do opt for LiFePO4 battery then I think I have to swap out my charge controller.

How easy or hard is this to do? Would it be simply unscrew it from the front of the cabinet and then attach wires to the same place on the new controller?



Is it a simple DYI project?

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I have attached an image of my current charge controller which is a Mark 1512. Also images of specs for this model.

That way some who understands these things can tell me if I am correct in needing a different charge controller.

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Specialty Concepts MARK/15-12 Charge Controller
MARK 15-12 Charge Controller
Specialty Concepts
MARK 15 Photovoltaic Charge Controller

The Specialty Concepts, Inc. MARK 15 is a cost effective, flush mount, battery charge controller with digital system monitoring. The MARK 15 is available for 12 or 24-volt systems with charging current up to 15 amps, and provides efficient charging while protecting the batteries from damage due to overcharging. This controller is designed for use in mobile or stationary photovoltaic energy systems, with complete system monitoring of battery voltage, solar charging current, and charge set-point calibration. Chargemode status lights, battery condition LED bar-graph, a blocking diode, battery fuse and array fuse are standard.

FEATURES CHARGE REGULATION
• 15 amp charge current, 12 or 24 volt Easily handles over-currents
• Switching shunt, LFCS pulse charging method
• Field adjustable set-points

DESIGN FEATURES
• 100% solid-state
• Designed for rugged mobile use
• Over-current protection - battery fuse, array fuse
• Reverse leakage protection - blocking diode
• Reverse polarity protection
• Lightning protection
• Input noise suppression
• Low power consumption
• 12 awg terminal block

MONITORING
• Digital monitoring of:
a) System battery voltage
b) Solar charge current
c) Charge set-point calibration
• "SOLAR CHARGING" light
• "BATTERY CHARGED" light
• LED bar-graph BATTERY CONDITION indicator
• BAR or DOT display
• Power saver display mode MOUNTING
• Flush mount
• Knock-out box available for wall mounting (4x7 BOX accessory)

Notes:
(1) Low-voltage load disconnect option
(2) Temperature compensation option
(3) Non-inductive.
(4) LVD relay energized, typical value.
(5) Carry only, Non-switching
(6) The Charge Termination / Resumption span is fixed. The Resumption set-point changes as the Termination set-point is adjusted.
(7) The Load Disconnect / Reconnect span is fixed. The Reconnect set-point changes as the Disconnect set-point is adjusted.

[rickst29]

This looks like a very primitive 1-stage "Constant Current" Controller. When Voltage is in range, it delivers whatever current is both available form the Panel and accepted by the battery(s). When battery Voltage rises to the "Charge Termination" Value, then it shuts off (completely), delivering nothing until the battery(s) fall low enough to hit the "charge resumption" value. Then they start charging again.
- - - -
This would need to be thrown away and replaced if you acquired LiFePO4 batteries. And it would need to be thrown away and replaced if you replaced the 80W Solar Panel with a bigger array. (Bigger arrays are more capable of charging batteries, but they are also more capable of damaging batteries, if connected through a "Controller" as bad as this one.)

Hardest Job: Replacing the 120V "Converter" with a Lithium-tunable model.
Second Hardest: Upgrading Solar Panels.
Third Hardest: Replacing Batteries.
Easiest: Replacing the Solar Controller.

[BrucePerens]

The old solar controller will still work as a battery monitor if you disconnect the solar panels from it. Don't throw it out.

Modern MPPT chargers are cheap. Figuring out where to add panels and how to connect them will take some calculation. Where is the present one mounted?

[Bailey'sMom]

Originally Posted by rickst29

Hardest Job: Replacing the 120V "Converter" with a Lithium-tunable model.
Second Hardest: Upgrading Solar Panels.
Third Hardest: Replacing Batteries.
Easiest: Replacing the Solar Controller.

If all I do is replace the batteries with same size flooded batteries, then you are still recommending that I replace the Mark1512 solar controller, correct?

If I replace the solar controller is it a simple swap out existing with new one, same wires, etc? No new wires, just try to fit in the same location?

It is located just below the sink on the front of that cabinet. See attached pic for approximate location. (Not a pic of my actual trailer)

[BrucePerens]

Do not replace the solar controller until you get more panels. First, see if one panel and the present controller are enough for your normal use with larger flooded batteries.

You might not need to have your money burn a hole in your pocket :-)

[Bailey'sMom]

Originally Posted by BrucePerens

Do not replace the solar controller until you get more panels. First, see if one panel and the present controller are enough for your normal use with larger flooded batteries.

You might not need to have your money burn a hole in your pocket :-)

Glad to hear. I have plenty of other projects to spend my money on, like a new roof on the house and a couple of Solatube’s to add light in the house.

[rickst29]

My components will be:
One AIMS 1 100Ah battery, list price $850 at the Inverter Store https://theinverterstore.com/product...100ah-lifepo4/. (But it costs me about $950 for me, because I pay NV Sales Tax on this item). It replaces 2*SLA 100Ah, and provides about the same usable capacity.

- Edit 5/719 - I just changed that and bought a single '150Ah' battery, direct from China: https://www.aliexpress.com/item/12V-...006197898.html. If it shows up and works as advertised, it's 50% more battery for quite a bit less money.

- Edit 7/19719 - If I were buying a USA-built product today, I would choose one or two of the Trojan "Trillium". The battery protection and status display are greatly 'enhanced', in comparison to other Products (including Battle Born). Among other features, a "battery protector" battery shutoff is built in, handling both out-of-range voltage and out-of-range temperature issues.

(For me, SLA was always hard to charge above about 85% on the road, and needed to red-line at 50% SOC. That allowed only 35% available AND useable capacity per battery. With LiFePO4, I can probably use more than 75% of the nominal capacity - that's more power available from just one battery.)

A PD 4655L "MBA WildKat" 55A converter section replacement, with 'Wizard' pendant. Surprisingly, I think that I should use the pendant to control charging - and *NOT* flick the switch for "Lithium". PD Sales and Support representatives agree. http://www.bestconverter.com/PD-4655...l#.XMtM_6RlDb0

[BrucePerens]

Don't even think of connecting that without a battery protector.

[rickst29]

Originally Posted by BrucePerens

Don't even think of connecting that without a battery protector.

Bruce, I *was* thinking of that, because the "disconnect" logic of the internal BMS seems very comparable to the alternative of an external "battery protector". (Both alternatives include a circuit breaker, of course. But the Circuit Breaker will primarily protect the connecting wire from overload, because the battery itself is capable of 100A charge and discharge rates.)

Do you know of battery protectors which can offer tighter shutdown voltage limits, AND work without requiring connection to the (unexposed) BMS? (Some which I looked at, such as Victron, depend on a separate BMS to make all the decisions, and use an explicit connector monitor disconnect/reconnect signal wires.)

For me, and other interested TM persons: Can you explain with a bit more detail? I don't understand your warning. Thanks in advance!