12v to 24v charging?!

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scopas asked Mar 17, '19

12v to 24v charging?!

Charging system on my boat.

My engine has a 24v Alternator that charges the house bank and a 12v Alternator that charges the start battery.

I want to get more charge into the 24v house bank per engine hour and am thinking how best to utilise the "spare" capacity of the 12v Alternator once it has re charged the start battery after its initial use.

Can I use a Orion DC / DC to charge the house bank? I'd like it to only do that once the engine start battery is up to charge.

My 24v house bank is AGM 360ah and the 24v Alternator is rated at 80amps. The 12v Alternator is rated at 60amps. Neither of them has a separate "charge controller / regulator".

Any ideas and help would be welcome.

battery charging Orion DC-DC Converters not smart

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Answer 1 · 2019-03-17T11:27:15Z

JohnC answered · Mar 17, 2019 at 11:27 AM

Hi. If your 24V alternator can actually produce 80A, then it's already oversized for your house bank. If you could measure the A you'd probably find it never gets there because the batts can't accept that much. They may for a few minutes, but can't sustain it. Once the ultimate charge V is achieved the alt will back off, and adding more charge capacity would be futile.

The Orion could do what you want, but it only has a single V adjustment (like the alternator). Just thinking aloud now, but perhaps you could set the Orion to a higher Absorb V, and switch it on/off to suit.

A BMV battery monitor would be useful in your situation, regardless of what you end up doing..

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Answer 2 · 2019-03-17T12:15:00Z

scopas answered · Mar 17, 2019 at 12:15 PM

Many thanks

I have a BMV battery monitor, indeed very useful.

Max amps I get is about 40 but I think that's more to do with the revs / alternator than charge acceptance of the batteries.

Thank you for your thoughts.

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Answer 3 · 2019-03-17T12:41:04Z

Paul B answered · Mar 17, 2019 at 12:41 PM

Look you may not want to hear this, but instead of investing in more alternator charging or a DC to Dc converter, look at 1 x 180A/H (2.5kw) Lithium Phosphate battery bank, this will replace the 360 A/H of LA you have in total but can only use max 50% or 180 A/H of the LA and then the last 20% takes for ever to charge.

So if the current bank is a few years old it maybe a good option to look at, you wont look back, plus the LP will last and last way way way past the time of the LA banks.

ALSO with LP dont go overboard with extra capacity, put in 180 A/H or 2.5 Kw and see how it goes, you can always add batteries to a existing LP bank even years after (as long as they are the same working voltages that is )

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scopas commented · Mar 17, 2019 at 01:50 PM

Hi Thanks - Yes I have been considering that but I have heard issues of large current draw on the Alternator and maybe my Alternator isn't up to the job? May need to add more cooling to the Alternator? Its a bit of a minefield. I was looking at the Lead Carbon batteries also as they seem to be a good compromise between LifePO4 and AGM?

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