T-Pain Is On A Boat: [Electric Boats] Re: Recommendations for a 48volt to 12 volt dc to dc converter?

Monday, June 1, 2009

[Electric Boats] Re: Recommendations for a 48volt to 12 volt dc to dc converter?

Paul Smith,

Mark Stafford cheering you on. Especially with the Costco cheapos, tapping part of a larger battery pack works well, and may arguably be the most efficient. The key is battery longevity. Costco cheapos may lack refinement, but they are probably flooded lead-acid, right? FLA batteries can be strung up in endless series for high voltage charging/discharging, and each individual cell in each battery won't commit suicide. SLA batteries are not so lucky. Since they are sealed, you can't (not safely) add distilled water to replace the water lost from the boiled cells.

Why boiled cells? A weaker battery amongst stronger batteries in a series charges slower, and the strongest battery gobbles electrons quicker. Unless a BMS (battery management system) detects the fat kid, he will eat until he explodes.

The coolest new lithium batteries all use a BMS, or really a CMS (cell mngt sys) that keeps individual cells happy.

I hope to sea your Electric Lion sometime. If prices come way down, maybe you'll have a LIon Lion.

Mark Stafford
H55 project Berkeley

--- In electricboats@yahoogroups.com, "Paul C. Smith" <paul136mc@...> wrote:
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> Hi , what I'm doing on the LION is probably a bit un-kosher to battery-care fanatics. I have a 24v motor and 12 v house needs (at present pretty limited). I have 2 sets of 4 batteries set up for 24v output form either port (good glass matts) and starboard (Costco cheapos - a lot of amphours for the buck and a 3 year replacement warranty). I can charge either 24v bank or both from two 80 watt solar panels in series. The port bank is the main propulsion, and i'm tapping the starboard costco batteies in the middle for 12v house use. Simple to set up and use, and it all charges off the 24v array and controller. Remains to be seen how it'll work over long term, battery life etc.
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> Best Regards,
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> Paul <paul136mc@...>
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> Paul C. Smith 707 874 2112
> PO Box 120
> Camp meeker, CA 95419
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> ________________________________
> From: aweekdaysailor <aweekdaysailor@...>
> To: electricboats@yahoogroups.com
> Sent: Saturday, May 30, 2009 5:43:12 PM
> Subject: [Electric Boats] Re: Recommendations for a 48volt to 12 volt dc to dc converter?
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> After several failed experiments (my loss your gain) I am using 2 of Thunderstruck' s inexpensive 10amp controllers in parallel. I see no RF interference issues (you have to have faith and connect your 12V and 48V negatives - I was expecting ghostbuster- like fireworks... ).
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> Ideally - figure out your max amp draw then build for 150% of that - so on my boat 20amps is about max (water pressure, lights, sumps) - I should ideally have 3 ganged together for N+1 redundency. They are so cheap (~$25) as to be nearly disposable so carry a spare. The other cool thing to think about is running a +48V "backbone" and converting locally where the power is needed. I built up a breadboard with a +48 bar, and a dual-bus +-12V and then connected the -12V and -48V.
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> The downside to these units is they can't charge a 12V battery as they put out exactly 12V.
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> I have lost a couple in playing around - one where I probably reversed the polarity the other where I am somewhat suspicious that back-emf from a fan got to it. In both cases they got real hot and a cap popped.
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> Anyway, been running with these for a couple of months now and no troubles.
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> -Keith
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> --- In electricboats@ yahoogroups. com, "lmfelder" <lamarfelder@ ...> wrote:
> >
> > I have a columbia 36 that I have converted to electric and I want to add a 48 to 12 volt dc to dc converter -- does anyone have any recommendations as to brand or where to get etc? I had been using one bank to power my motor and one bank for house but I would rather increase my range and just pull house of of the 48 volt bank.
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> > Thanks
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