Battery Charging Diode

[PaulRainbow]

Ok thanks. Makes total sense..

To add a little complexity into the equation I went to take a closer look at my small solar controller for the small panel. It's a Solara Fox350 and has two outputs. It says:

The FOX-350 is designed for charging 2 separate battery systems. A bistable relay provides the option of switching the charge current to the battery -the batteries are always fully isolated from each other.The relay switches the "+" string, the mass lines of the batteries should be connected with each other.(See connection plan on page 47).The 2-battery logic is only active, if 2 batteries are connected to it. Battery 1 is charged until the charging logic reaches step 3, in order to guarantee that battery 1 is fully charged.In principle, switching-over only becomes active once the battery voltage of battery 2 has fallen below13.8 V.

You could connect the solar controller to the engine and domestic bow batteries, so it charges both, and omit the VSR then fit a 3 output ArgoFET. Then the alternator and mains charger charge all 3 banks, large solar array charges the domestics, small solar does the engine and bow batteries.

I've been assuming you have a 3 outlet mains charger (you didn't say), but if that's not the case you can use your manual switching arrangement to charge more than one bank from mains, as you must have been doing f it's a single output charger.

 

[Tim Good]

You could connect the solar controller to the engine and domestic batteries, so it charges both, and omit the VSR then fit a 3 output ArgoFET. Then the alternator and mains charger charge all 3 banks, large solar array charges the domestics, small solar does the engine and bow batteries.

I've been assuming you have a 3 outlet mains charger (you didn't say), but if that's not the case you can use your manual switching arrangement to charge more than one bank from mains, as you must have been doing f it's a single output charger.

It’s an old but solid Heart Freedom 20.

I think it must have only one outlet as that’s the way it’s rigged now. To charge the bow and engine from the mains I have to use the large switch to bring them together.

 

[PaulRainbow]

It’s an old but solid Heart Freedom 20.

I think it must have only one outlet as that’s the way it’s rigged now. To charge the bow and engine from the mains I have to use the large switch to bring them together.

Moving goal posts

3 way ArgoFET connected to all banks with the alternator and mains charger connected to the input. So mains and alternator now charge all three banks with no user intervention.

Large solar array to the domestic bank, small panel to the engine and bow batteries. All batteries now charged by solar too.

All you need to buy is the ArgoFET and a bit of cabling. Off you go

 

[Tim Good]

Moving goal posts

3 way ArgoFET connected to all banks with the alternator and mains charger connected to the input. So mains and alternator now charge all three banks with no user intervention.

Large solar array to the domestic bank, small panel to the engine and bow batteries. All batteries now charged by solar too.

All you need to buy is the ArgoFET and a bit of cabling. Off you go

Ok great thanks... but won’t I have the same issue of my mains charger being setup at a voltage idea for the torjans? And how will it know when to go to float if it’s going through the FET and feeding three separate battery banks?

 

[PaulRainbow]

Ok great thanks... but won’t I have the same issue of my mains charger being setup at a voltage idea for the torjans? And how will it know when to go to float if it’s going through the FET and feeding three separate battery banks?

I thought you said you rarely used the mains charger, because solar kept up with demand ? Short time exposure to Trojan charging voltages isn't going to hurt the batteries, daily charging by solar, when the domestic bank is on load is another matter. The charge should still go into float but you'll need to double check it does. If it doesn't try connecting the sense wire on the ArgoFET

 

[RobbieW]

I thought you said you rarely used the mains charger, because solar kept up with demand ? Short time exposure to Trojan charging voltages isn't going to hurt the batteries, daily charging by solar, when the domestic bank is on load is another matter. The charge should still go into float but you'll need to double check it does. If it doesn't try connecting the sense wire on the ArgoFET

Scuse me chipping in here; this is, for me anyway, the crux of this and why I don't use anything automated to link batteries. My solar doesn't keep up so after 3-4 days I have a 1-200 amp deficit in the house bank, the engine batt will be fine. I'm also not a purist so when cruising I'll motor to get somewhere, 24-48 hrs if necessary. I don't want the engine battery held at house levels even though they're the same technology for the time it takes to charge the house bank. Sounds like I have a similar set up to @northcave with a Freedom 20, my alternator is controlled by a balmar 614 with sensing and temp from the house bank. The engine batt has a small b2b that I've made switchable, if I want to give it a blast I'll parallel the engine/ house batts

 

[PaulRainbow]

Scuse me chipping in here; this is, for me anyway, the crux of this and why I don't use anything automated to link batteries. My solar doesn't keep up so after 3-4 days I have a 1-200 amp deficit in the house bank, the engine batt will be fine. I'm also not a purist so when cruising I'll motor to get somewhere, 24-48 hrs if necessary. I don't want the engine battery held at house levels even though they're the same technology for the time it takes to charge the house bank. Sounds like I have a similar set up to @northcave with a Freedom 20, my alternator is controlled by a balmar 614 with sensing and temp from the house bank. The engine batt has a small b2b that I've made switchable, if I want to give it a blast I'll parallel the engine/ house batts

Lots of way to skin the battery charging cat and a lot will depend on individual systems and usage patterns, so no one size fits all. I've offered several possible solutions throughout this thread and they'd all work OK, or even some variations on some of them.

Holding the engine battery at house voltages isn't the issue some claim it to be, if the voltages are suitable for the batteries. My sealed engine battery has been in parallel with the engine batteries (via a VSR), charged by solar or mains for 4 years or so. The domestic bank were also SLA, so voltages suitable for both. I've just changed to Trojans and upped the chargers to 14.8v absorption and i'm not too keen on holding the engine battery at 14.8v all of the time the trojans are on absorption, either by mains or solar, so i've removed the VSR. I'm tempted to fit a B2B charger for the engine battery, but i may just monitor it and occasionally parallel the banks, as you do. The engine battery holds charge really well anyway. My alternator is standard automotive and i'm not bothered about that, the solar keeps the Trojans charged anyway.

If the OP had an external regulator that output high voltages then i might only fit a 2 output ArgoFET and leave the small solar panel to look after the engine battery, that would need to be monitored though, extended use an dull days could lead to a low DOD if not .

Another solution would be to go with B2Bs, as you have. Connect all charging sources to the Trojans, with charging voltages/regimes to suit and fit B2Bs between the domestic bank and engine battery and the domestic and bow battery, or one B2B to the engine battery and a VSR to the bow battery.

 

[Tim Good]

You could connect the solar controller to the engine and domestic batteries, so it charges both, and omit the VSR then fit a 3 output ArgoFET. Then the alternator and mains charger charge all 3 banks, large solar array charges the domestics, small solar does the engine and bow batteries.

I've been assuming you have a 3 outlet mains charger (you didn't say), but if that's not the case you can use your manual switching arrangement to charge more than one bank from mains, as you must have been doing f it's a single output charger.

Just going back to this comment Paul... Did you meant to say "You could connect the solar controller to the engine and bow batteries, so it charges both, and omit the VSR"

 

[PaulRainbow]

Just going back to this comment Paul... Did you meant to say "You could connect the solar controller to the engine and bow batteries, so it charges both, and omit the VSR"

Sorry, yes, i meant engine and bow batteries.

 

[Tim Good]

Sorry, yes, i meant engine and bow batteries.

Thanks. Ok I think I'll go for the simple solution and get a Argofet 200-3... then stick the small panel controller output onto the posts for the engine and bow and leave the mains charger on the main bank. Even I can sort that out

Thanks for all your help!!

 

[PaulRainbow]

Thanks. Ok I think I'll go for the simple solution and get a Argofet 200-3... then stick the small panel controller output onto the posts for the engine and bow and leave the mains charger on the main bank. Even I can sort that out

If you're happy with that, it's all good. You're obviously aware that the mains charger doesn't charge the engine and bow batteries and know how to deal with, if needs be.

Thanks for all your help!!

You're most welcome.