Solar, Alternator/Starting Battery and Lithium Solution

theoldwizard1 wrote:

time2roll wrote:
MPPT is ok but max input is 25v so limits you to 12v panels.

I don't see this as much of a problem. Higher solar voltage are typically only used when the wire runs from the panels to the controller are long.

24V panels provide lower cost/watt and smaller footprint/watt. Wiring is smaller/cheaper.

With serial connected panels shaded power is higher than parallel panels due to bypass diodes. And a combiner is eliminated along with the larger combiner to controller wiring.

MPPT controller is required for 12V batteries, higher controller input voltage and the panels are larger - typically 60 or more cells vs 36 for 12V panels.

time2roll wrote:
MPPT is ok but max input is 25v so limits you to 12v panels.

I don't see this as much of a problem. Higher solar voltage are typically only used when the wire runs from the panels to the controller are long.

time2roll wrote:
I prefer manually programmable charging profile.

Concur !

time2roll wrote:
Does not say if it boosts the alternator voltage. May have missed that.

It does not say it specifically, but it certainly IMPLIES it !

First, unless you have a pretty old RV/tow vehicle, every vehicle built in the US has had "smart charging" for the past 10-15 years, so when installing this unit it is important to follow those instructions !

With the smart alternator setting, the charger "turns on" when the voltage is above 12.0V (cut off at 11.5V). You aren't going to be doing any Bulk or Constant charging at that low of and input voltage !

My MH alternator charging is around 20 amps after things settle down from about 35 amps from starting the engine and wait a bit.

However, with my big solar set, and it set to 14.x, it soon overwhelms the alternator voltage which ends up below the solar voltage by a bit, so the alternator contribution to the total amps is more like 10 amps--- not the 20 amps it would be without the solar.

In any case, the alternator charging isn't hurting anything and at best, does add some amps. If it is not sunny, there is no solar, so then the alternator charging is what you have going down the road.

The unit apparently expects both battery banks to be the same type and not mixed FLA and Li. Normally the alternator will quickly charge the FLA engine battery and drop to 13.4V, what does the unit do for charging the Li at 14.4V with minimum solar due to clouds and nighttime.

My engine battery has very little usage when boondocking so I'd have no reason for solar to charge it with this unit.

In my quick review of the manual I wanted more information but perhaps I need to read again.

Fifty amp limit to charge batteries is not a heck of a lot. It's an attempt in the right direction but 200 amp-hours delivered in a 4-hour drive doesn't tweak my beakie. Especially if that includes solar input. A gross limit in other words. A net limit, alternator only, plus the ability of a 40 or 50 amp panel addition would be a lot better IMHO.

MPPT is ok but max input is 25v so limits you to 12v panels.
I prefer manually programmable charging profile.
Does not say if it boosts the alternator voltage. May have missed that.

Looks ok. Renogy is good stuff.

My only possible negative is that you can get by easily without the charging from the tow vehicle. Solar runs on the road.

Renogy's reputation is pretty good.