24v alternator to charge (2) 12v 8D banks

[rwells36]

I was asked this question by someone else and thought it relevant to our discussion. Although I am unsure of its relevance

705 is the grand total of all 12v units' fuse and circuit breakers.

[petter5]

Agree with you. Why purchase a lot of expensive stuff to make the system complicated and with a lot of loss in converters or extra alternators. A standard voltage sensing charging relay between the 12 volt battery circuit in each battery bank will do the job so you does not even have to think about the possibility to discharge the 'wrong' battery bank.

Originally Posted by soerencarlsen

yes you can charge your 12v batteries, hopefully you have noted that your 24v comes from 2 12v batteries as I have never seen a 24v batteri.
you just run a jumper lead from one of you 12v starter batteries to whatever you need. some sort of diode should be fitted so the current only flows one way.

[rwells36]

I priced the following:

Orion DC-DC Converter - Victron Energy (1) ORI241225020



Argo FET Battery Isolators - Victron Energy - (2) 100 amp 3 ARG100301020



Quattro - Victron Energy 24 5 (1) QUA245023110



BlueSolar (1) MPPT 150/35 - Victron Energy



Color Control GX - Victron Energy - (1) BPP000300100R

Total was about 4500.00 when, in reality the DC DC (24v 12v) converters hanging off the 24v alternators is all I really need with no further changes. Price was only about 600$ total for the converters. Still doesn't include solar though.

[dlymn]

this might be a part of the solution

24 volt to 12 volt DC/DC converters (fully regulated) 140 Watts and 240 Watts.

You still might need a charge controller.

[Scott Berg]

As far as solar is concerned just use whatever panels you have with 24v Boost MPPT controllers; they can take lower voltage panels and boost to the needed 28.8v/26.4v bulk/acceptance/float voltages you'll need for a 24v system. You really don't need a 12v bank on a 24v boat. You MAY need a 24v inverter but that's it; converters can handle all the low current 12v loads.. much simpler... just finished one last week.

[smac999]

Originally Posted by petter5

Agree with you. Why purchase a lot of expensive stuff to make the system complicated and with a lot of loss in converters or extra alternators. A standard voltage sensing charging relay between the 12 volt battery circuit in each battery bank will do the job so you does not even have to think about the possibility to discharge the 'wrong' battery bank.

if you try to charge the 12v battery from half of the 24v bank the 24v bank will explode....

if you put 200ah into the 12v house bank. you have also put 200ah into the upper 24v battery, which was already full.

because you can't have current going into the house bank unless it flows through the upper 24v battery. which it doesn't need or want.

[rwells36]

scac999 why do you think it will explode? Is that immediately or over time? I have a tap now to one half of my 24 v bank into my 12v. Been about 4 years (no explosions yet). It's switch controlled and my chart plotter voltage reading out tops off at 13+ volts rather nicely. This arrangement isn't so good on that 2nd 8D of my 24v bank through. It uses a good amount of water when servicing it.

[rwells36]

smac999 actually by using a DC converter or an isolator one can indeed utilize voltage from a 24v alternator safely and without ill effects. It's a very common practice.

[rwells36]

May be getting close to a design solution:

https://www.victronenergy.com/upload...nverter-EN.pdf

[chala]

Originally Posted by smac999

if you try to charge the 12v battery from half of the 24v bank the 24v bank will explode....

if you put 200ah into the 12v house bank. you have also put 200ah into the upper 24v battery, which was already full.

because you can't have current going into the house bank unless it flows through the upper 24v battery. which it doesn't need or want.

So if it doesn’t need or want it how would that make the full bank to explode?

Originally Posted by TeddyDiver

Insane to have 4 separated battery banks IMHO.

Why would that be insane?

[rwells36]

Compliments of Victron Energy...

[TeddyDiver]

Originally Posted by chala

Why would that be insane?

Like burning money when you don't have it enough. Single bank is more economic energy vice, lasts longer, easier to charge, manage, maintain and KISS.
Wan't to know more?
BR Teddy

[rwells36]

It's important to realize that I'm not constructing a boat from scratch. I am not ripping everything out. I am making some configurations that complement the EXISTING set up. KISS includes NOT replacing inverters and chargers.

[smac999]

what is the amp rating of the buck boost? the first diagram will give you more charging to the house battery by having 2 of them. assuming they are not rated sky high.

[smac999]

Originally Posted by chala

So if it doesn’t need or want it how would that make the full bank to explode?



?

because the current is forced through the full one in order to get to the low one.