Multiple Charging Sources for a 12v Battery Bank

Despite all of the details you've provided, the question you've asked is just too vague. You probably can connect a trickle charge circuit for your system. Without a schematic of the circuitry you have and what you intend to connect, one cannot say what will be the consequence of adding this load. The consequences can be as dire as circuit breakers blowing or fires started to the trivial modest reduction of maximum battery operation time.

I don't know either, but maybe something like this would help with a part of the puzzle.

http://www.northerntool.com/shop/tools/product_200326706_200326706

The 19 volt power pack could work as a trickle charger provided you have a current limiting resistor in series with its output. Connecting it directly would most likely burn it out in a very short time.

Given a 10 volt deep discharge level to limit the 19 volt power packs output to less than 4.5 amps would require a 2 ohm resistor in series with the output capable of supporting about 41 watts of energy loss. However at the normal 14 volt floating charge level a 2 ohm resistor would give a roughly 2.5 amp floating charge current with a 12.5 watt power loss in the resistor.

If it was me I would use a common 50 - 100 watt wire wound type of resistor so that it had plenty of thermal reserve and did not run too hot when running at the power packs peak amp load.

Thats my theory on how I would set it up anyway.

My thanks to all who have commented,

redfred - Before starting this thread I drew a diagram of the existing system, together with a second diagram showing everything together with the new additions. Unfortunately I cannot see how to post these 2 diagrams so they are not much help!

The object of these changes is not to provide an additional trickle charge just to give an extra few minutes of battery power in the event of a Brown Out. What I wish to do is add the desulphator to the system. This is powered by the battery bank & will cause a 12 -20amp drain per day. Without the PSU providing a trickle charge I would need to use the 30amp charger daily for an hour or so to replenish the loss.

If I was away from home for a couple of days or so I would lose 50amphours of power. This would be approximately one third of my available amps (not wishing to discharge the batteries over 50%). The batteries are now 2yrs+ old & will cost over $500 to replace. The replacement is not neccessary yet, but I'm hopeful that the desulfator will provide an extra 12months or so useful life

kramarat - Thanks for the link, I'm hoping to achieve what that device does with a $45 desulfator and the PSU trickle charger

tcmtech - Very Helpful, thanks! From what you have said I take it that when a brownout occurs I switch off the PSU. When the Power Co. restores power after a 12hr brownout my battery bank is usually down to around 11.5v. I recharge as usual with the 30amp charger. When the batteries are fully charged I turn off the 30amp charger & turn on the PSU. I will still fit the 2 ohm resistor as even with this fitted there is excess power above what the desulfator will drain, which should keep the batteries in the best condition possible.

kebang

Unfortunately I cannot see how to post these 2 diagrams so they are not much help!

try japanese style . . .

& bullsh­¡t (it doesnot work so ...)

this over technology disables simple things so it's like back in wwii >>
copy-paste NEXT to Notepad replace chr(183) with chr(32)
(and you've received a "proportional font" throug 21-st century internet)

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^{Unfortunately I cannot see how to post these 2 diagrams so they are not much help! +}

Shure you can always describe your circuit textually as terminal A connected to ...
(((( >;i muhahhahahaa))))

My first question is "How long do you want your batteries to last?" As charging to "full" will shorten their life considerably, my guess is around 50% for quality batteries.

What type of Lead acid batteries are they, car batteries or leisure for example?

A trickle charge must be adjusted so that the batteries either remain at exactly the same finished voltage, or very slowly reduce their voltage. Having a trickle charge that increases battery voltage, no matter how slowly, will severely shorten battery life if above say 13.6 volts.....

My suggestion is to only charge to 13.4 volts max which will give a very long life to the batteries and about 70% capacity......and NO GASSING, which can be very dangerous if not properly catered for. Many have lost their eyes when a battery is gassing and something, clothing for example causes a spark....

Do also remember that every battery is an individual entity and really needs different charging rules and values, that is not possible of course, so treat them all gently.

Andy - Unfortunately they are Sealed Wet Lead Car Batteries. (No Maintainance & minimal escaped hydrogen), albeit the best quality available. 2yrs ago there was no source of deep cycle batteries in Bohol. (I can now order 220ah 6v golf cart batteries locally, so when this bank finally dies I will replace them with 2 golf cart batteries).

At this moment when I charge them I take them to around 13.6 volts. Over the period of a week this will drop to around 12.7 volts, when I do a top up charge.

I'll reduce the charge voltage to 13.4v from now on. Before proceeding with the 'PSU trickle charge' idea I'll fit the desulfator & monitor the situation. Only if they are discharging to quickly will I start experimenting with the PSU, with various sized resistors until I find a level which will hold around 13v

Thanks for the advice

kebang

You seem to be doing a good job allround, 13.6 volts is not too bad really.

As they are car batteries, they can supply sudden huge numbers of amps, called "Cranking (starting) amps. Make sure that everything is fused and protected in case of the dreaded "short"!!

Try not to let them stay too long under 12.6 volts, recharge as soon as you can. In this aspect leisure batteries are more forgiving than car batteries.

Taking a car battery below 10 volts, even for a short time will reduce its life span, whereas a leisure battery will hardly notice it.....

Andy - I realised that the car batteries were a poor substitute whe I purchased them, but there wasn't much I could do about it. What I did do was buy the best available & double the number that I estimated I would need for a 12hr brownout out.

The result has been favorable. Over 2 years & 30+ brownouts later the batteries have never dropped below 11.5v & consequently they have recharged satisfactorily. They always remain cold to touch, which I think is a good sign.

The only thing the battery bank is connected to is the inverter, which is protected by its own fuses. Is that sufficient or do you reccomend placing a large fuse inline on the battery lead?

kebang

If you have long leads to the inverter, an extra fuse near the battery might be a good idea. Use a sealed type of fuse suitable for use where explosive gases may be found, in spite of the fact that I believe you said they were sealed lead acid batteries.

Staying cool at all times is VERY good, I completely forgot to mention that point.....

Sounds as though you have a good balanced system, working well at the correct voltages/currents, well done.

You really didn't need us!!!!

Andy - I did! Without the advice I've received here I would probably connected the psu 'as is' and either burnt it out or cooked the batteries!

kebang