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n21roadie
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Multiple power supplies

Tue May 25, 2010 7:55 pm

I have a power supply for each mikrotik device at the AP's, was thinking I could power some, say 4 units from one large power supply but am worried about the obvious if the power supply fails, then by that example 4 units are down, So I am looking for dual power supplies if one section fails then the other takes over, Is there one available at a cost effective price.

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Re: Multiple power supplies

Tue May 25, 2010 9:36 pm

Colo and Wholesale Bandwidth Available! Sales at SanDiegoBroadband dot com
 
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Re: Multiple power supplies

Tue May 25, 2010 11:50 pm

Thanks , but the item has a bad review by previous customers ?
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Re: Multiple power supplies

Wed May 26, 2010 12:07 am

ive never used any of these, just figured that if servers are including them you could buy them separately. You could probably get a good one from a supermicro chassis (used) even.
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Re: Multiple power supplies

Wed May 26, 2010 3:49 am

If you use a charge controller and run off battery you could use one of these (see link below) to sense the primary supply, when it is no longer available it can toggle a relay which switches over to the secondary supply, when the it senses the primary it will switch back automatically. You have to have a battery system to provide power during the sense and switch over.
This also allows you to use whatever supply you wish.

hxxp://www.controlbyweb.com/webrelay/
 
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Re: Multiple power supplies

Wed May 26, 2010 10:38 am

Hi,

look at this http://www.restlesspowerbox.com
you can use RPB Compact for 4 Routers

If any questions contact me ks (at) cn24.net

Sonny
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Re: Multiple power supplies

Wed May 26, 2010 2:11 pm

Just stick two simple power supplies in paralel and connect PSU positive output via diode and you have redundant feature.
 
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Re: Multiple power supplies

Thu May 27, 2010 1:11 pm

Thanks for replies,

The restlesspowerbox features are impressive but I did not read the most important requirement that is redundant power supplies, If the power supply goes down you lose all the devices that were powered from that unit?,

The WebRelay looks promising,

Ideally I suppose I am looking for a:
(1) “hold-off” voltage from power supply 1 to changeover relay circuit, when power supply 1 is missing (i.e.: power supply one failure) the second power supply is used. ( This circuit will be powered from UPS so operation will take place)

(2) Current limit on output supply channels for each device rather than loop the voltage from device to device,(i.e.: power supply feeds 4 (+ 1) AP’s A,B,C.D,E standby AP - if say AP A fails and shorts out power supply, the current limit for channel 1 is activated and power remains on to the remaining AP’s B,C,D,E

(3) I was considering using any surplus Mikrotik device powered from supply 1, and when it loses power the Dude notifies of this event.


Just stick two simple power supplies in paralel and connect PSU positive output via diode and you have redundant feature.
Not sure about the stability of attaching a diode on the + of each power supply, I have seen diodes go short circuit as opposed to the popular open circuit fault condition? However thanks for the suggestion

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Re: Multiple power supplies

Thu May 27, 2010 2:14 pm

If you not exceed Absolute Maximum Ratings it's very stable. Regading ralay devices all this devices have bad MTBF rate. And I am not use it for any serious application.
 
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Re: Multiple power supplies

Thu May 27, 2010 8:49 pm

If you not exceed Absolute Maximum Ratings it's very stable. Regading ralay devices all this devices have bad MTBF rate. And I am not use it for any serious application.
This is good news, can i ask have you have tried this method and works for you, thanks


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Re: Multiple power supplies

Fri May 28, 2010 8:07 am

Since I cange all my 18V PSU to 24V I don't feel requirement for redundant power supply solution :))
 
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Re: Multiple power supplies

Fri May 28, 2010 12:55 pm

Since I cange all my 18V PSU to 24V I don't feel requirement for redundant power supply solution :))
You say changed power supply from 18v to 24v, Are you now running all of your devices from one single 24v power supply,
or have you a 24v power supply for each device,


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Re: Multiple power supplies

Mon May 02, 2011 6:58 pm

Just stick two simple power supplies in paralel and connect PSU positive output via diode and you have redundant feature.
Has anybody tried this power supply redundancy method?
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Re: Multiple power supplies

Mon May 02, 2011 10:57 pm

Hi why dont try a Restlesspowerbox?
You will love it, by its multiple features. And its from only 189 Euro.
You do not need second powesupply, because if the powersupply will fail the integrated batteries will power the router.
you will be informed about a failure by email and/or SMS (optional).
Give it a try!

sonny
http://www.citynetz24.de - http://www.retlesspowerbox.com
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Re: Multiple power supplies

Tue May 03, 2011 12:23 pm

Hi why dont try a Restlesspowerbox?
You will love it, by its multiple features. And its from only 189 Euro.
You do not need second powesupply, because if the powersupply will fail the integrated batteries will power the router.
you will be informed about a failure by email and/or SMS (optional).
Give it a try!

sonny
http://www.citynetz24.de - http://www.retlesspowerbox.com
How many POE ports does it have and can i attach my 113AH deep cycle battery to this unit for time extension when running on a battery
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Re: Multiple power supplies

Wed May 04, 2011 12:38 pm

http://www.amazon.com/Altronix-SMP5-Pow ... B0006ZF4CS

Hooks straight up to your battery and has a built in charge controller.

use 2x and figure out how to wire redundancy...

i think we have a few of these exact ones powering wireless camera gear thats been in service for over 6 years...

how often do you plan on servicing it? :)
 
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Re: Multiple power supplies

Thu May 05, 2011 2:47 am

How many POE ports does it have and can i attach my 113AH deep cycle battery to this unit for time extension when running on a battery
It has 4 POE ports. If you use 24V battery you can power the box with it.
If the battery is discharging you can Monitor this and get informed by Email.
How are you charging your battery?
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Re: Multiple power supplies

Thu May 05, 2011 8:56 am

Just stick two simple power supplies in paralel and connect PSU positive output via diode and you have redundant feature.
Has anybody tried this power supply redundancy method?
I spent 30 years in electronics before wireless networking and this method does work. In this application, the diodes are called "steering diodes". It allows power to flow from each power supply through a diode to a common positive point to feed the load. If one power supply short-circuits, the diodes prevent power from the remaining good supply from flowing backwards and shorting through the failed supply.

If the load side short-circuits, there isn't much you can do, it will drag down both power supplies.
 
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Re: Multiple power supplies

Thu May 05, 2011 12:11 pm

I spent 30 years in electronics before wireless networking and this method does work. In this application, the diodes are called "steering diodes". It allows power to flow from each power supply through a diode to a common positive point to feed the load. If one power supply short-circuits, the diodes prevent power from the remaining good supply from flowing backwards and shorting through the failed supply.

If the load side short-circuits, there isn't much you can do, it will drag down both power supplies.
My plan is to use a inline fuse for each connected device, so if 8 devices connected and say load no 2 goes short it blows the inline fuse. and prehaps a led light on the load side of the fuse so this will indicate which fuse is gone
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Re: Multiple power supplies

Thu May 05, 2011 2:17 pm

It has 4 POE ports. If you use 24V battery you can power the box with it.
If the battery is discharging you can Monitor this and get informed by Email.
How are you charging your battery?
At present i have this battery attached to a UPS in place of the 2 batteries which came with UPS
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Re: Multiple power supplies

Fri May 06, 2011 9:55 am

Why not try a AD-55 or AD-155?
Examples here: http://tandem.ck.ua/ups_mt-eng.php
 
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Re: Multiple power supplies

Fri May 06, 2011 10:55 am

Why not try a AD-55 or AD-155?
Examples here: http://tandem.ck.ua/ups_mt-eng.php
That is a single PSU there is no redundancy
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Re: Multiple power supplies

Fri May 06, 2011 11:09 am

Why not try a AD-55 or AD-155?
Examples here: http://tandem.ck.ua/ups_mt-eng.php
That is a single PSU there is no redundancy
For important sites, I put a separate (redundant) power supply.
He is completely galvanically isolated.
This is to ensure that at risk he was alive.
Connection manually.
http://tandem.ck.ua/img/electronics/ups ... 4V33AH.jpg
AD-55B + СКС-150-24
If necessary, the connection with the diodes, but I do not use.
Sorry for bad English.
 
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Re: Multiple power supplies

Fri May 06, 2011 5:34 pm

the diodes prevent power from the remaining good supply from flowing backwards and shorting through the failed supply.
This is exactly what happened to me!!

I had 2 48v 1amp power supplies connected in parallel, powering a rb 800.
The one power supply blew short after 2 years of operation and dropped the rb 800.

I have now subsequently put diodes in all my installations with parallel power supplies.
 
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Re: Multiple power supplies

Fri May 06, 2011 10:00 pm

This is exactly what happened to me!!

I had 2 48v 1amp power supplies connected in parallel, powering a rb 800.
The one power supply blew short after 2 years of operation and dropped the rb 800.

I have now subsequently put diodes in all my installations with parallel power supplies.
And with the diodes have you had any more problems since,
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Re: Multiple power supplies

Sun Aug 14, 2011 9:12 pm

Hi why dont try a Restlesspowerbox?
You will love it, by its multiple features. And its from only 189 Euro.
You do not need second powesupply, because if the powersupply will fail the integrated batteries will power the router.
you will be informed about a failure by email and/or SMS (optional).
Give it a try!

sonny
http://www.citynetz24.de - http://www.retlesspowerbox.com
Well, considering competition in ISP market, it is rather hard to keep the costs down, when shelling out almost 200Euros per one end for just power supply backup.
My suggestion would still be - Meanwell 24v/5a psu + 2x12Ah/12v batteries + simple voltage monitor script in routeros, to get you notified and ready to respond if the power doesn't return.
The total would be around 100Euros and a bit longer backup time.
 
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Re: Multiple power supplies

Sun Aug 14, 2011 11:30 pm

Well, considering competition in ISP market, it is rather hard to keep the costs down, when shelling out almost 200Euros per one end for just power supply backup.
My suggestion would still be - Meanwell 24v/5a psu + 2x12Ah/12v batteries + simple voltage monitor script in routeros, to get you notified and ready to respond if the power doesn't return.
The total would be around 100Euros and a bit longer backup time.
Yes - I use this power solution for some time and it's great
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Re: Multiple power supplies

Sat Dec 10, 2011 2:42 pm

Why not try a AD-55 or AD-155?
Examples here: http://tandem.ck.ua/ups_mt-eng.php
I came to this solution with these Meanwell power supplies few years ago. I don't know how you guys were successfully using it, but these power supplies aren't exactly compatible with lead-acid batteries used with them, especially AD-55B 24V model. These sealed maintenance free lead-acid batteries require constant-voltage/constant-current charging. The later one isn't that much important as CV, but it still counts. You have to charge them with at least 13,6V, which in case of two batteries would obviously be at least 27,2V. And according to battery manufacturers, 13,65-13,8V is the best voltage for float charging when this battery is used in cycle mode (which in this case it is). The problem arises that if you want to rise the voltage at battery terminals to 27,2-27,3V, you have to also increase the output rail voltage (that is the simple way), which then becomes ~28,1V which isn't what you want with most RouterBoards, since their specification tells you shouldn't apply more than 28V to them (and yes, I know about voltage drops in long PoE lines). This seems to apply less for 13.8V version of the PSU, there you could easily turn the pot to get the desired voltage at battery output terminals, since the voltage of output to the boards doesn't really matter in this case.

The charging current control is also working a little strangely in these power supplies. It is supposed to charge the battery at around 640mA current after serious discharge (the relay should click), but it only applies the 0,16A charging after AC power is restored, which is ok for float charging, but not for restoring the battery.

I could of course be wrong about something, so your input is always welcome.
 
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Re: Multiple power supplies

Sat Dec 10, 2011 3:14 pm

Why not try a AD-55 or AD-155?
Examples here: http://tandem.ck.ua/ups_mt-eng.php
I came to this solution with these Meanwell power supplies few years ago. I don't know how you guys were successfully using it, but these power supplies aren't exactly compatible with lead-acid batteries used with them, especially AD-55B 24V model. These sealed maintenance free lead-acid batteries require constant-voltage/constant-current charging. The later one isn't that much important as CV, but it still counts. You have to charge them with at least 13,6V, which in case of two batteries would obviously be at least 27,2V. And according to battery manufacturers, 13,65-13,8V is the best voltage for float charging when this battery is used in cycle mode (which in this case it is). The problem arises that if you want to rise the voltage at battery terminals to 27,2-27,3V, you have to also increase the output rail voltage (that is the simple way), which then becomes ~28,1V which isn't what you want with most RouterBoards, since their specification tells you shouldn't apply more than 28V to them (and yes, I know about voltage drops in long PoE lines). This seems to apply less for 13.8V version of the PSU, there you could easily turn the pot to get the desired voltage at battery output terminals, since the voltage of output to the boards doesn't really matter in this case.

The charging current control is also working a little strangely in these power supplies. It is supposed to charge the battery at around 640mA current after serious discharge (the relay should click), but it only applies the 0,16A charging after AC power is restored, which is ok for float charging, but not for restoring the battery.

I could of course be wrong about something, so your input is always welcome.
This a very interesting comment does it mean that to charge the batteries we are approaching the cut-off threshold (less POE cable loss) of routerboard ?
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Re: Multiple power supplies

Tue Dec 13, 2011 3:03 pm

The problem arises that if you want to rise the voltage at battery terminals to 27,2-27,3V, you have to also increase the output rail voltage (that is the simple way), which then becomes ~28,1V which isn't what you want with most RouterBoards, since their specification tells you shouldn't apply more than 28V to them (and yes, I know about voltage drops in long PoE lines).
If this is a problem, it solved by the installation of a diode.
The charging current control is also working a little strangely in these power supplies. It is supposed to charge the battery at around 640mA current after serious discharge (the relay should click), but it only applies the 0,16A charging after AC power is restored, which is ok for float charging, but not for restoring the battery.
The charging current is really nevsegda enough.
You can modify the AD-55 and increase the current up to 0,5 ... 0,6 A.
This, however, exclude the warranty on the AD-55.
 
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Re: Multiple power supplies

Tue Dec 13, 2011 4:23 pm

The charging current is really nevsegda enough.
You can modify the AD-55 and increase the current up to 0,5 ... 0,6 A.
This, however, exclude the warranty on the AD-55.
How is this done, componet change or preset adjustment?
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Re: Multiple power supplies

Tue Dec 13, 2011 7:02 pm

Yep, diodes are quite simple and effective solution to drop output voltage to desired level. I haven't taken any of these units apart to take a look inside, but according to the block diagram in product datasheet, that might be the only clever way of doing it, since the charging circuitry takes voltage from that same supply output and has no diversity. I have few of these power supplies that have expired warranty period, so I shall try to have them checked when I have time. My best guess would be, that something that triggers high current charging has to be modified. For example if I put 22ohm 5W resistor across battery terminals, the relay engages and the battery output starts to pump as much as 0.64A of current which is indeed perfect for recharging seriously drained battery. Unfortunately this doesn't happen with any batteries connected. Another approach is to raise the float charge current to any desired value and leave the battery to choose how much juice it needs.
 
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Re: Multiple power supplies

Tue Dec 13, 2011 7:39 pm

How is this done, componet change or preset adjustment?
We must not forget that the effective capacity reduced to 50 watts when charging the battery.
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Re: Multiple power supplies

Sat Jan 28, 2012 5:03 pm

Well, the pics are nice, but I don't believe your suggestion is correct. First of all, the circuit is drawn all wrong (no offense :) ).. This is quite simple power supply and even simpler charge current limiter. You should simply replace the 20R resistor R50 & R51 in series to, let's say one 3.3 ohm 2W resistor, and you get enough current to charge your battery. I don't think your solution is good, because bypassing the diode almost eliminates it's purpose. I know it doesn't do much while the supply functions as it should (normally - relay open) To my opinion, it's cleaner to replace the existing resistors with appropriate ones. The only thing in this circuit to limit charging current is that double resistor (R50+R51). Whatever is your way, it is the point you'd want to consider first.

I'm attaching the circuit diagram for you to get the idea better. In my setup 3.3R resistor allows about 680mA of current to pass into the battery after complete discharge, afterwards it keeps dropping until it reaches float charging current of about 40-80mA. The voltage at open battery terminals is set to 27.3V (normally being 13.65V per battery), and with fully connected battery is 27.1V. This is the behavior I would expect from normally working battery charger. With 3.3R resistor, voltage output terminals read 27.6-27.7V. If it seems too high for you, or if you'd like to raise the charging voltage, simply adding one or two diodes in series makes it fine.

One more thing. I suggest to check MeanWell PSC100 A/B power supplies. They have higher charging rating, a monitoring circuit with appropriate output pins for each condition, but are a little bit more expensive, doesn't have a cover and wire connection terminals. Anyway they don't have to be modified, which doesn't void warranty.
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Re: Multiple power supplies

Sat Feb 11, 2012 7:33 pm

Convenient and affordable solution for batteries up to 60 A * h.
P S C-60 - http://www.meanwell.com/search/psc-60/default.htm
This solves all problems.
 
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Re: Multiple power supplies

Wed Mar 21, 2012 1:05 am

Convenient and affordable solution for batteries up to 60 A * h.
P S C-60 - http://www.meanwell.com/search/psc-60/default.htm
This solves all problems.
Up to 60ah but my plan as i have them to hand is 2 X 113ah deep cycle batteries in series, now how would i re-charge them if they ran down,

Could a seperate smart battery charger do and when charged have a relay to switch over the 24volt battery supply back to AD-155's, not sure if you can a seperate battery charger connected to the batteries while the ad-155 is also running
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Re: Multiple power supplies

Sun Apr 29, 2012 6:59 pm

Just doing tests with battery duration using 2 X 12v and I noticed that once the dc voltage from the batteries fell below 21 volts, the relay which is 12v with a 15v zener in series de-energizes and disconnects battery supply to the output,

Now we have several limitations at present
Routerboard max input voltage of 28.x volts
Meanwell SMPS cuts out output DC when batteries fall below 21.x volts

Plan now is swap 15v zener (ZD41) to 12V which should give me additional 3volts battery and reduce the cut-off from 21v to 18v.
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Re: Multiple power supplies

Thu May 10, 2012 4:44 pm

Ok - Update I replaced 15v zener diode with 12v and this has reduced the dc cut off from 21 to 19volts, also replaced R50+R51 with 4R7 resistors 3watt,

How can I calculate cut-off time from 24volts to 19volts with 370mA current draw


....This is quite simple power supply and even simpler charge current limiter. You should simply replace the 20R resistor R50 & R51 in series to, let's say one 3.3 ohm 2W resistor, and you get enough current to charge your battery. I don't think your solution is good, because bypassing the diode almost eliminates it's purpose. I know it doesn't do much while the supply functions as it should (normally - relay open) To my opinion, it's cleaner to replace the existing resistors with appropriate ones. The only thing in this circuit to limit charging current is that double resistor (R50+R51). Whatever is your way, it is the point you'd want to consider first.

I'm attaching the circuit diagram for you to get the idea better. In my setup 3.3R resistor allows about 680mA of current to pass into the battery after complete discharge, afterwards it keeps dropping until it reaches float charging current of about 40-80mA. The voltage at open battery terminals is set to 27.3V (normally being 13.65V per battery), and with fully connected battery is 27.1V. This is the behavior I would expect from normally working battery charger. With 3.3R resistor, voltage output terminals read 27.6-27.7V. If it seems too high for you, or if you'd like to raise the charging voltage, simply adding one or two diodes in series makes it fine.
.......

I don't think it is possible to completely discharge the batteries as the internal relay disconnects the batteries when voltage drops below as mentioned 21volts now 19volts.
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Re: Multiple power supplies

Thu May 10, 2012 5:38 pm

That zener there is a very simple overdischarge protection. 19V would mean that you're discharging your batteries to 9.5V per battery which is exactly the lowest allowed voltage specified by most battery manufacturers. You are significantly shortening battery life operating it that way. On the other hand, it won't do much harm if it seldom happens. Either way wouldn't it be wiser to simply use higher capacity batteries?
 
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Re: Multiple power supplies

Thu May 10, 2012 6:05 pm

That zener there is a very simple overdischarge protection. 19V would mean that you're discharging your batteries to 9.5V per battery which is exactly the lowest allowed voltage specified by most battery manufacturers. You are significantly shortening battery life operating it that way. On the other hand, it won't do much harm if it seldom happens. Either way wouldn't it be wiser to simply use higher capacity batteries?
At present i use 2 X 12v 7Ah and asked before what is the maximum capacity that can be used. You say this is "significantly shortening battery life operating it that way" does this also apply to deep cycle batteries. AC power supply outages are rare and usually the result of a storm and because of isolated locations there can be a delay in restoring the ac supply as it would be listed as a low priority, so it would be important to have long battery life to cover such a event.
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Re: Multiple power supplies

Tue May 15, 2012 2:48 am

Convenient and affordable solution for batteries up to 60 A * h.
P S C-60 - http://www.meanwell.com/search/psc-60/default.htm
This solves all problems.
Up to 60ah but my plan as i have them to hand is 2 X 113ah deep cycle batteries in series, now how would i re-charge them if they ran down,

Could a seperate smart battery charger do and when charged have a relay to switch over the 24volt battery supply back to AD-155's, not sure if you can a seperate battery charger connected to the batteries while the ad-155 is also running
Check out these devices, they will be able to do it all. We use them for our sites and have never had any issues.
http://www.snaptec.com.au/dc-ups-systems.html
 
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Re: Multiple power supplies

Fri Jul 27, 2012 12:33 pm

Encountered an issue with my modified meanwell power supply , from diagram ZD41 was 15v now 9.2v, R50+R51 were 10ohm now 4.7ohm, without batteries connected the power supply is non-stop opening and closing the relay with green led blinking on/off but if I connect the batteries it starts as normal and when I disconnect AC the power supply takes the voltage from the batteries as it should. Any suggestions should I increase R50+51 or increase ZD41 or both but I had selected the lower zener voltage to reduce the cut-off voltage from 21volts to less than 18.
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Re: Multiple power supplies

Thu Aug 30, 2012 6:57 pm

I am looking for a smart 24volt battery charger that will auto charge batteries if required when AC power is restored, I have 2 X 12Volt 113ah deep cycle batteries to hand and would like to attach to the meanwell 155w 24volt power supplies but there is no way I assume that the meanwell can charge the batteries if they go low after a power outage.
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Re: Multiple power supplies

Fri Aug 31, 2012 1:00 pm

Convenient and affordable solution for batteries up to 60 A * h.
P S C-60 - http://www.meanwell.com/search/psc-60/default.htm
This solves all problems.
Up to 60ah but my plan as i have them to hand is 2 X 113ah deep cycle batteries in series, now how would i re-charge them if they ran down,

Could a seperate smart battery charger do and when charged have a relay to switch over the 24volt battery supply back to AD-155's, not sure if you can a seperate battery charger connected to the batteries while the ad-155 is also running
Check out these devices, they will be able to do it all. We use them for our sites and have never had any issues.
http://www.snaptec.com.au/dc-ups-systems.html
How much do they cost and how long have you been using them?
 
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Re: Multiple power supplies

Fri Sep 07, 2012 8:53 am

Convenient and affordable solution for batteries up to 60 A * h.
P S C-60 - http://www.meanwell.com/search/psc-60/default.htm
This solves all problems.
Up to 60ah but my plan as i have them to hand is 2 X 113ah deep cycle batteries in series, now how would i re-charge them if they ran down,

Could a seperate smart battery charger do and when charged have a relay to switch over the 24volt battery supply back to AD-155's, not sure if you can a seperate battery charger connected to the batteries while the ad-155 is also running
For these batteries AD-155 does not fit.
Very little in his current charge.
Pay attention to my last post here:
http://forum.mikrotik.com/viewtopic.php ... ps#p332691
 
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Re: Multiple power supplies

Sat Sep 15, 2012 10:36 pm

If steering diodes can be used to combine power supplies for failover then can the same apply to charging batteries,
could i use more diodes to charge batteries,

I have 2 X 113ah 12v deep cycle batteries and considering using 4 X meanwell AD155 24v power supplies on site and could I use diodes (or are they really needed?) to charge the 2 batteries which will supply 24volts to the 4 X power supplies @56ah?
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Re: Multiple power supplies

Mon Sep 17, 2012 6:34 pm

Not sure that you would need diodes as the chargers should already have as to prevent feedback from the batteries.
 
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Re: Multiple power supplies

Wed Jul 03, 2013 1:15 pm

Update;

My original goal was to have redundancy power option for a base station which has AP’s + Ptp’s + interconnect routers, and after calculating that 2 x 24V 10A using steering diodes may not have high enough current rating (because it is good practice to de-rate by 50% the max current the power supply is rated for?) results in 2 X 24V 5A,

I planned to use 4 X 24V 10A power supplies but still had concerns what batteries could I connect to these power supplies which usually would have 2 X 12Volt 7Ah batteries for each power supply, giving a total of 8 batteries and total of 56ah (8 x 7ah) on the batteries,

Another issue is the cut-out voltage where the power supply running on the batteries during a AC outage would cut out at 21volts (due to deep discharge that could damage some type of batteries?) this would give a swing of say 24 to 21 volts, just 3 volts when running on batteries ?

I had modified the power supplies and reduced the cut-off down to 18volts but was still unhappy as routers will operate at 12volts but the power supplies would cut off at 18v?

So I thought there must be a more simple solution and to hand I had deep cycle batteries and after some research come up with a very simple and very effective redundancy layout,

1 X 20Amp 24volt DC float charger, 2 X 12Volt 113Ah deep cycle batteries
This has been operating for over a year flawlessly supplying the 24volts DC requirement of this base station, the charger is just warm to touch but not hot and is set on load to 26.39volts,

I inserted a Digital 60V 100A Battery Balance Voltage Power Current Analyser Watt Meter, which displays actual load voltage, current, wattage and calculates amp hour, etc.

I am very impressed with this simple configuration and deep cycle batteries are suitable for deep discharge that would occur in a AC power outage and the float charger will recharge the batteries and also importantly trickle charge the batteries for normal day to day power load
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