charging trolling motor battery w/solar

[nicaland]

I have a 110AH deep cycle flooded cell battery for a trolling motor that I would like to charge with my 200W solar panels by directly hooking it up to the DC leads running to my inverter from my house bank which are readily accessible with some really heavy battery cables. I have 220AH of group 27 deep cycle flooded acid house batteries, and one group 24 flooded cell engine starting battery, both banks receiving charge from the panels and/or a 30A progressive dynamic converter/charger section via my generator or engine alternator, as a result of connecting both banks with a Blue Seas ACR. The trolling motor battery should never be drawn down to more than around 12.2V before charging. My panel output is around 10A.

Can anyone see any issues with this plan? I'm suspect that connecting the trolling battery which will usually be at a voltage below my house bank, and would result in initially bringing down my house bank voltage, and at that point could skew the bank's voltage down a tad, which could affect the charging regimen a bit coming from any source available, but can't see why that would be much of an issue.

Alternatively I could use my stand alone 2A-10A 120V auto charger hooked directly up to the trolling battery, which I assume would really be the better way to go when I'm on Shorepower, generator output, or engine alternator, but would think that using it in conjunction with my 2000W inverter's 120V output would incur a substantial DC voltage efficiency loss that I would rather avoid when using only the panels for charging.

I hope this makes sense! Opinions anyone?

[booster]

Originally Posted by nicaland

I have a 110AH deep cycle flooded cell battery for a trolling motor that I would like to charge with my 200W solar panels by directly hooking it up to the DC leads running to my inverter from my house bank which are readily accessible with some really heavy battery cables. I have 220AH of group 27 deep cycle flooded acid house batteries, and one group 24 flooded cell engine starting battery, both banks receiving charge from the panels and/or a 30A progressive dynamic converter/charger section via my generator or engine alternator, as a result of connecting both banks with a Blue Seas ACR. The trolling motor battery should never be drawn down to more than around 12.2V before charging. My panel output is around 10A.

Can anyone see any issues with this plan? I'm suspect that connecting the trolling battery which will usually be at a voltage below my house bank, and would result in initially bringing down my house bank voltage, and at that point could skew the bank's voltage down a tad, which could affect the charging regimen a bit coming from any source available, but can't see why that would be much of an issue.

Alternatively I could use my stand alone 2A-10A 120V auto charger hooked directly up to the trolling battery, which I assume would really be the better way to go when I'm on Shorepower, generator output, or engine alternator, but would think that using it in conjunction with my 2000W inverter's 120V output would incur a substantial DC voltage efficiency loss that I would rather avoid when using only the panels for charging.

I hope this makes sense! Opinions anyone?

You mention the draw down until the battery voltages match and that is probably the biggest downside.


How well the solar charges could depend on how the controller sees what is going on. If you have unit that has multstage charging and programmed battery bank size, the profile may get altered. With the bank getting bigger it probably won't be a big deal, though. If the solar is already into float when you plug in the trolling battery, you need to make sure the solar goes back into bulk stage so you get better/faster charging.

[nicaland]

Thanks for the quick reply Booster. I was pretty sure that there wouldn't be a significant issue in doing this but wanted to confirm, and I most definitely respect your input!

[InterBlog]

I can't provide an answer to the specific question asked, but, during my general research, I've seen an abundance of been-there-done-that advice recommending indirect charging of peripherals rather than direct.

In other words, rather than direct solar charging of your external battery (whatever it is to be used for - trolling motor or something else), charge something else that can then, in turn, invert and charge your item. Otherwise you are going to find yourself too tied up logistically to your solar panels because direct solar feed is simply too slow. There are energy losses associated with inverting, yes. But depending on the scenario, it can be more time-efficient.

Mind you, everything we use off-grid with the exception of our chassis battery is lithium, so I am speaking from that context. And we don't charge anything as large as a trolling battery either, so I can't speak with any authority on that scenario. We do frequent (sometimes daily) recharges of multiple drone batteries (big time juice gobblers, all of them) and large power tool batteries (including a six and a half pound, 7.5 AH Ego).

If an indirect consideration would not be feasible in the OP's scenario, someone please comment with specifics and I will count myself as having learned something new today.