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Old 24-03-2019, 15:25   #1
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Solar controller for Lithium and AGM MPPT?

Trying to figure out what controller to get that will handle Lithium house bats and AGM engine bats at the same time. I have 1000 watts of solar, so assume I need a 80+ amp controller? MPPT seems to really be the way to go.
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Old 24-03-2019, 16:36   #2
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Re: Solar controller for Lithium and AGM MPPT?

Since they should be on completely separate setpoints, should be on separate SCs.

Or one bank gets run through a DCDC charger.

I only buy charge sources with user-custom profile / setpoints.

That is all that's required for LFP compatibility.
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Old 25-03-2019, 04:04   #3
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Re: Solar controller for Lithium and AGM MPPT?

Good point, and the house and engine are separated. I was hoping the technology was here to do both with one.
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Old 25-03-2019, 06:39   #4
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Re: Solar controller for Lithium and AGM MPPT?

There are units that package two SCs in one case, but they are not less expensive than buying two good units like the Victrons separately.

And may or may not allow for user custom programming.
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Old 25-03-2019, 16:06   #5
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Re: Solar controller for Lithium and AGM MPPT?

If you had a VSD to switch charging current on from LFP to AGM, what would be the issue, is 13.6 or what ever the LFB is set up as, isn't it enough?.
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Old 26-03-2019, 05:49   #6
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Re: Solar controller for Lithium and AGM MPPT?

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Originally Posted by Oceanride007 View Post
If you had a VSD to switch charging current on from LFP to AGM, what would be the issue, is 13.6 or what ever the LFB is set up as, isn't it enough?.
Each quality battery's mfg publishes detailed charge profile specs.

For AGM ignore them only if you don't expect longevity, and north of 14.7V is very common.

For LFP it's the opposite, personally never go much over 13.8 in daily cycling except for short / fast / high currents without CV / Absorb staging.

With them, following vendor specs is what threatens maximizing longevity 8-)
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Old 26-03-2019, 19:26   #7
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Re: Solar controller for Lithium and AGM MPPT?

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Originally Posted by Fearnow View Post
Trying to figure out what controller to get that will handle Lithium house bats and AGM engine bats at the same time. I have 1000 watts of solar, so assume I need a 80+ amp controller? MPPT seems to really be the way to go.

If the AGM batts are for the engine only, they're likely starter batts, not deep cycle? Either way, unless you don't use your engines regularly for more than 3 or 4 months, they should get recharged by the alternator and you don't need to worry about some dual profile charger.
If you still want to do that, you could get a programmable one like the Victron and hook it up through the serial port to change the settings. But that's too much work for most people. A simple relay to top up the AGMs from the LFPs every now and then could be a simple option, too.
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Old 27-03-2019, 04:58   #8
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Re: Solar controller for Lithium and AGM MPPT?

Good point. I'll either run the engine for a while, or charge while at a dock.
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Old 27-03-2019, 05:27   #9
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Re: Solar controller for Lithium and AGM MPPT?

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A simple relay to top up the AGMs from the LFPs every now and then could be a simple option, too.
The voltage would be too low. If just a Starter batt who cares, but many use lead for a Reserve emergency bank and if that bank is expensive, it should be cared for according to mfg spec.

Dozens of ways are possible, and you are correct, a Starter can be directly charged by the alts, and should that energy be needed for LFP as well, then its voltage stepped down.
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