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A quick question about battery power
A quick question about battery power
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Old 22nd March 2006, 06:38 PM   #1
Thunau is offline Thunau  United States
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Default A quick question about battery power

I have two big-a$$ boat 12V batteries that were installed in my basement as a backup power source for a pump. I since fixed the source of the original water breach and have no need for the pump or the backup system.
So, I had an idea to use two good quality 4 channel car amplifiers for my active 3 way speakers and run them from two separate 12V, 100W switching PS, with the boat batteries providing the extra amps if/when needed. The question is, is it safe to paralell the batteries with the switchers? If not, is there a circuit that would make the connection a sound one?
"Most people just say what they know, the wise ones know just what to say."
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Old 22nd March 2006, 07:37 PM   #2
Netlist is offline Netlist  Belgium
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I'm not a wise man but I can move your thread to PSU design

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Old 23rd March 2006, 01:53 AM   #3
anatech is offline anatech  Canada
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A quick question about battery power
Hi Jan,
I'm sure you will get some answers. Not knowing completely, I'd suggest asking this question of a boat electrical technician. I am sure they have installed systems like these in boats before.

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Old 23rd March 2006, 04:35 AM   #4
chipco3434 is offline chipco3434  United States
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I don't think that I would parallel them. Ultimately one battery will be discharging into the other battery. Keep the amps and the batteries seperated and by a "two bank" charger for them.

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Old 23rd March 2006, 07:36 AM   #5
Wombat2 is offline Wombat2  Australia
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If identical batteries you can parallel no probs and double your amp/hours. Make sure (with hydrometer) that all cells are close in SG otherwise you will accelerate any breakdown.
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Old 23rd March 2006, 08:16 AM   #6
Flodstroem is offline Flodstroem  Norway
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Default 12V 100W SMPS ?

Hi Thunau

The question is, is it safe to paralell the batteries with the switchers? If not, is there a circuit that would make the connection a sound one?
If batteries is of same type, status and brand you could easily parallel them for 12V double capacity.

But, parallel battery with SMPS, is not easy because of this:

Battery need at least 14-14,4 V when charging. When battery is full charged (by a suited battery-charger) the battery voltage will be approx. 13-13.2 V (=2.2V/cell). If connect battery to SMPS current could flow IN TO the SMPS and make some damage though the SMPS only have 12V outputs.

If you connect battery to SMPS when battery is <13.2V, say 12V, well your battery will newer be charged by the SMPS because it need at least 13.2 V to keep it maintenance charged.

Maybe you could trim outputs on SMPS to reach 13.2-13.8V then it could be an option. But the SMPS has no control on charging status for battery. Battery could be over charged if SMPS outputs reaches more than 13.8V. Also dont forget those batteries are not sealed (I guess) and can explode if a spark is made at one of the poles (thats why good chargers start a delayed charging, only AFTER battery had been safely connected to it) Those batteries do have oxygen and hydrogen inside the shell (= explosion risk to count on).

My suggestion is that you drive the amps only by your batteries OR only with your SMPS connected to a large capacitor bank for your purpose. Dont use your charger when you play your amps or else they could pic up high switching frequencies (only guessing) and burn your amps or loudspeakers though most modern chargers of today is built like a SMPS without the DC-filtering (=output normally consist only of pulsed DC at high frequency).

Just my thoughts

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