charging geny 12V battery from 24V service bank?

vas

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evening all,

replaced three batteries as the two starter ones died after only 4yrs with the nasty trick I did of picking 12V from the groundmost one to start and run the generator.
So third battery is the geny starter one.

Now I have:

4X6V Trojan T105RE for service
2X12V 140Ah for starting the engines
1X12V 100Ah (or 80 forgot already...) for the generator

Victron Centaur 24/60A charging both main banks if and when I turn it on.
Victron MPPT 100/15 charging the service bank from 2X300W solar panels
port alternator charging service
stbrd alternator charging starter

gen battery not charged atm as MASE hasn't got an alternator and the generator panel is lacking the subsystem doing so (mix and match by the looks of it by previous owner)

Options as discussed in other threads are:

use a Victron smartcharger 12V15A permanently connected on the geny output so whenever the geny runs, battery is charged.
get a dedicated DC->DC circuit and charge it from the service bank

my concern is that the way I'll be operating the geny is unlikely to get the battery ever fully charged, one hour every couple of days when onboard for the watermaker the odd eve half hour A/C to cool the cabins, not much.
second concern is that I occasionally use the Victron to charge dingy battery or "revive" friend's batteries and that sort of thing.

So as far as charging patterns are concerned, I feel that I could use a system that by midday (that I typically have fully charged service batteries) some of that extra juice goes to a 24->12 dropper/charger - bulk - float sort of thing which will auto power off after a couple of hours (or so)
Makes sense? I think it does.

I'll be building a PCB for the generator controller which will do all sorts of things for the newly rebuilt yanmar 2GM monitoring (even managed to squeeze a EGT sensor as well as the leftover sea water pressure sensor :D ) so I was thinking of integrating a simple 2stage charging circuit in it for that. Voltage sensing would enable the waking up and charging only the days needed and making sure this battery will last double as much.

I note that Victron hasn't got 24->12V charger, only droppers, I've seen some 90+ such devices but not at all keen. I've also seen some v.simple 10euro assembled kits 6-60V in 12.whatnot (adjustable) V charging out.

any views on that?

cheers

V.

PS. as you may note I'm running out of important things to do, so trying to keep myself busy with simpler things :p
 
Just buy a small dedicated charger from an auto shop , Bosch for example.
Connect to the isolated geny bat .
When the genys on or shore power ie any 220 V turn it on like your main boat charger .
 
Just buy a small dedicated charger from an auto shop , Bosch for example.
Connect to the isolated geny bat .
When the genys on or shore power ie any 220 V turn it on like your main boat charger .

well, PF, that's the main problem.
I'm never on shore power because I don't need it and as I said in another thread, last year I only used the Victron main bat.charger once for an hour or so.
I have everything running of the solar panels on the h/t
OTOH, I do have a 1000Wquasi sine inverter on all the time, but it would be daft to have a dedicated 12V charger on all the time hence my thinking.

cheers

V.
 
evening all,

replaced three batteries as the two starter ones died after only 4yrs with the nasty trick I did of picking 12V from the groundmost one to start and run the generator.
So third battery is the geny starter one.

Now I have:

4X6V Trojan T105RE for service
2X12V 140Ah for starting the engines
1X12V 100Ah (or 80 forgot already...) for the generator

Victron Centaur 24/60A charging both main banks if and when I turn it on.
Victron MPPT 100/15 charging the service bank from 2X300W solar panels
port alternator charging service
stbrd alternator charging starter

gen battery not charged atm as MASE hasn't got an alternator and the generator panel is lacking the subsystem doing so (mix and match by the looks of it by previous owner)

Options as discussed in other threads are:

use a Victron smartcharger 12V15A permanently connected on the geny output so whenever the geny runs, battery is charged.
get a dedicated DC->DC circuit and charge it from the service bank

my concern is that the way I'll be operating the geny is unlikely to get the battery ever fully charged, one hour every couple of days when onboard for the watermaker the odd eve half hour A/C to cool the cabins, not much.
second concern is that I occasionally use the Victron to charge dingy battery or "revive" friend's batteries and that sort of thing.

So as far as charging patterns are concerned, I feel that I could use a system that by midday (that I typically have fully charged service batteries) some of that extra juice goes to a 24->12 dropper/charger - bulk - float sort of thing which will auto power off after a couple of hours (or so)
Makes sense? I think it does.

I'll be building a PCB for the generator controller which will do all sorts of things for the newly rebuilt yanmar 2GM monitoring (even managed to squeeze a EGT sensor as well as the leftover sea water pressure sensor :D ) so I was thinking of integrating a simple 2stage charging circuit in it for that. Voltage sensing would enable the waking up and charging only the days needed and making sure this battery will last double as much.

I note that Victron hasn't got 24->12V charger, only droppers, I've seen some 90+ such devices but not at all keen. I've also seen some v.simple 10euro assembled kits 6-60V in 12.whatnot (adjustable) V charging out.

any views on that?

cheers

V.

PS. as you may note I'm running out of important things to do, so trying to keep myself busy with simpler things :p

This is what I fitted - alfatronix Ici24-12 works well!
 
So as far as charging patterns are concerned, I feel that I could use a system that by midday (that I typically have fully charged service batteries) some of that extra juice goes to a 24->12 dropper/charger - bulk - float sort of thing which will auto power off after a couple of hours (or so)
Makes sense? I think it does.

if you are going to build a 24 > 12V dropper (whatever and however that is) then maybe as a suggestion look at the RC battery charger portfolio's. Their battery chargers can be quite sophisticated and easily a match on a smaller scale than anything I have seen offered to the marine market. You wont be charging at C, but you will be keeping the battery topped up and conditioned. Best of all for what they can do the price is ludicrously low.
 
thanks guys,

This is what I fitted - alfatronix Ici24-12 works well!

Asm, they are meant to be a great company but 130odd cheap they aint!

if you are going to build a 24 > 12V dropper (whatever and however that is) then maybe as a suggestion look at the RC battery charger portfolio's. Their battery chargers can be quite sophisticated and easily a match on a smaller scale than anything I have seen offered to the marine market. You wont be charging at C, but you will be keeping the battery topped up and conditioned. Best of all for what they can do the price is ludicrously low.

Bruce, when you say RC bat charger portfolios, you have something specific in mind? Most of the RC devices are running LiOn or whatnot fancy batteries, I'm talking lead acid ones here!

Or if you dont want the hassle of building a "dropper" this Overlander charger will also accept 24V

G.T.Power V6 Intelligent DC Charger

https://www.overlander.co.uk/chargers/chargers/dc-chargers/v6-g-t-power-intelligent-charger.html


EDIT

The only downside to these is each charge has to be manually started, they are not auto charge.

well, if I end up getting something like that I might as well use my Victron smart charger with a 24h timer to run off the inverter every noon for 2 or 3h.

Would be interested to have a look at any 2 stage charging layouts and maybe integrate them in my teensy PCB board.
Else I could get a 10euro board (with LCD display I kid you not!) like this:
https://www.ebay.co.uk/itm/Lead-Aci...Switch-12V-24V-48V-Supply-Module/173896275060

Ideally something like the above but with some multistage logic would be a vast improvement on a vanilla alternator that would set me back close to 100euro...

cheers

V.
 
The Victron 24/12v voltage convertor can act as a batt charger ( charge current will drop when voltage goes up) Last year I’ve installed one on the FB, for topping up the tender battery
 
The Victron 24/12v voltage convertor can act as a batt charger ( charge current will drop when voltage goes up) Last year I’ve installed one on the FB, for topping up the tender battery

Bart, that's what I thought but I do have a Victron 24->12 dropper for radio and NMEA2000 bus which only does 12.5V. I was told that victron used to have some such droppers/chargers but not anymore?
Going to their site, I can only find mine btw. Any pointers would be helpful.

Vas, out of interest, what do you use the inverter for?

Cheers
Andy

throughout the year with the boat on it's mooring for all my power tools (angle grinders, power drills, rechargeable tools, orbital sander, etc) when on the way for laptops and espresso (gas cooking).
the floating pontoon I'm moored stern to here has no water/el. so I need to use some temp cabling setup by the neighbours, not much point.
for example will do tomorrow if I manage to steal a couple of hours from work work and test in silence my stab hydraulics as I changed and moved a few pipes around as well as replaced the pump with a smaller one and not too sure I've not got air in the circuit...

V.
 
Would be interested to have a look at any 2 stage charging layouts and maybe integrate them in my teensy PCB board.
Else I could get a 10euro board (with LCD display I kid you not!) like this:
https://www.ebay.co.uk/itm/Lead-Aci...Switch-12V-24V-48V-Supply-Module/173896275060

.

:D :encouragement: I feel like I have been setup, which I suppose is par for the course when trying to think of ideas outside of the box when you have already been there. If you can solve it for ten euros then I have no idea why you are looking for alternatives, but hey if it's permission and blessings; you have them in spades :D
That's a neat little board, I may just buy one myself :encouragement:
 
:D :encouragement: I feel like I have been setup, which I suppose is par for the course when trying to think of ideas outside of the box when you have already been there. If you can solve it for ten euros then I have no idea why you are looking for alternatives, but hey if it's permission and blessings; you have them in spades :D
That's a neat little board, I may just buy one myself :encouragement:

It’s a brave man who offers advice about electronics to Vas:(. A bit like me trying to explain gravity to Einstein:)
 
:D Never dream of offering advice to the sage. Just suggesting possible alternatives. Somehow you always come away with your own boot wedged in your mouth, every time ;) :D
 
Vas, on the Victron Orion -Tr “isolated” 100/250/400 watt, the output voltage is adjustable, see online manual.

thanks Bart, I do have an Orion (but iirc and older one non -tr and "non-isolated") which I use, didn't realise that some of them are adjustable. Will check prices here and decide on this or the kit from China :D

:D :encouragement: I feel like I have been setup, which I suppose is par for the course when trying to think of ideas outside of the box when you have already been there. If you can solve it for ten euros then I have no idea why you are looking for alternatives, but hey if it's permission and blessings; you have them in spades :D
That's a neat little board, I may just buy one myself :encouragement:

Bruce, want to check it a bit more as I think you just regulate the V it outputs and the threshold it goes back to stage two which I don't remember what it is. Mind, no idea what sort of charging my IVECO alternators do, probably something similar...

It’s a brave man who offers advice about electronics to Vas:(. A bit like me trying to explain gravity to Einstein:)

you two, got to understand I've no formal training/qualifications in electronics/electrics. Just lots of fooling around doing things, hence me asking :D

cheers

V.
 
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