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Suggestion - dc / dc converter 500 - 1000W

Hi. I have played around lead alum battery from John Bedini and i must say i am quite exited about all this. Fast charging ( 12V / 85Ah under 45 minutes ), you can discharge it to almost 0V etc. Anyhow, there is bunch info on this on the net. Really good battery, with "small" problem.

The standard voltage of fully charged battery is around 11.5 to 12,5 V so when i hook up some standard DC/AC converter i can not start it.

The battery has almost the same current as the lead acid battery ( maybe some 10 - 15 % drop ) but voltage is a bit lower. I test is with 500W motor and it works like it should. There is just this problem with voltage...

So i need to find a way how to connect this battery to some AC device. The devices that am planning to use with this setup are max 200W, so this battery setup should be enough for whole day run...

The battery is charged from solar panel and i will use 2x 12/125Ah.

Question:

- what should i use to step up the voltage, some dc/dc converter ?

- if so, how much would one 500W dc/dc converter cost ?

Any idea is more then welcome !

Reply to
gm
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I'd probably try hacking the undervoltage lockout on the inverter, but don't set it too low or you might start a fire.

Cheers

Phil Hobbs

Reply to
Phil Hobbs

Why not add an extra cell?

Reply to
Rob

I can not add extra cell because its sealed truck car battery.

12V / 135Ah

----------------------- I was thinking on hacking the DC/AC converter but i don't have enough knowledge to do that. Beside, there is no schematics on the converter. It's some Chinese stuff (1500W / 3000W peak ).

Reply to
gm

--------------- If i would go with dc/dc converter ( let's say some 500W ), how can i limit the battery current ? As far as i know, such converters have some max input current value and it's most always under 20A.

Reply to
gm

P = U * I So I = P / U

This means that at 12.5 volt a 500 Watt converter is going to draw 40A or more.

No way you are going to limit that to 20A, unless the converter has an output power of 500 Chinese Watts. Chinese Watts are a lot less power than SI Watts. That is how they spec the 1500W/3000W Peak things.

Reply to
Rob

Running one SMPS off another isn't necessarily easy, especially if the second one (your inverter) expects a super-low-resistance source, i.e. a big lead-acid battery.

They can interact in strange ways, including oscillating. At your power level, oscillating switchers would be seriously bad news, like maybe burning your house down or spraying you with boiling acid. (I'm not a high power SMPS guy myself, but believe me, they're no joke.)

Perhaps you could find a better quality used unit on eBay that has schematics available?

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net
Reply to
Phil Hobbs

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