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Backup Battery for SLE 5700

 

Hi,
?
I'm looking to see if anyone here has a preferred or a "go-to" type of battery that you use for your repeaters. I'm installing an SLR 5700 in a temperature-controlled room. How long do I need the repeater to run on batteries? That really depends on the price of each battery and how many I can afford to buy. I have been very satisfied with Echo-Worthy products on Amazon for other ham radio activities but not sure if they're the right choice for a repeater and also if they fit the SLR 5700 internal battery charger.?
?
Also, when you have batteries connected to a repeater for backup power, do you put any other components in between the battery and the repeater? Perhaps for overcharge or over-discharge protection:?
?
All suggestions and recommendations would be appreciated.?
?
Best,
Sepehr N6IRN
 

Generically...
Victron supply/charge controller -> LiFePo (of adequate capacity) -> Low-voltage disconnect -> system 12v power bus

LiTime or WattCycle batteries - reasonable cost
 

get the battery back up cable from motorola and wire it directly into the battery.. just don't reverse the polarity...?

From: "Sepehr - N6IRN via groups.io" <n6irn@...>
To: [email protected]
Sent: Saturday, March 22, 2025 10:34:09 PM
Subject: [repeater-builder] Backup Battery for SLE 5700

Hi,
?
I'm looking to see if anyone here has a preferred or a "go-to" type of battery that you use for your repeaters. I'm installing an SLR 5700 in a temperature-controlled room. How long do I need the repeater to run on batteries? That really depends on the price of each battery and how many I can afford to buy. I have been very satisfied with Echo-Worthy products on Amazon for other ham radio activities but not sure if they're the right choice for a repeater and also if they fit the SLR 5700 internal battery charger.?
?
Also, when you have batteries connected to a repeater for backup power, do you put any other components in between the battery and the repeater? Perhaps for overcharge or over-discharge protection:?
?
All suggestions and recommendations would be appreciated.?
?
Best,
Sepehr N6IRN
 

I've got about half a dozen SLR customer repeaters and all of them are equipped with battery backup. I use inexpensive 100Ah marine grade sealed lead-acid battery, and an external Victron 13Amp fully automatic 3-stage charger, with the internal charger from the SLR disabled. It would take way too long for the limited internal charger alone to get the battery anywhere near fully charged in a reasonable amount of time, hence the external charger addition.

Given the SLR takes about 10amps at full (55W) tx power, battery can last anywhere between 12-24 hours, depending on repeater activity. Most sites also have generator backup, so battery usually only has to carry over until it kicks in, but at times also saved the day when the generator would for some reason not start.

One idea to extend battery operating time was to have a relay coil connected to the AC mains, and a normally open contact connected to one of the GPIO pins on the rear of the SLR and set it to switch to channel 2, then program ch1 as regular full power service, and ch2 for 25w or whatever lower power the system can get away with, and extend battery life with less current demand. But so far have not implemented that yet, but it should be a perfectly viable option.
 

Yes, I know that lead-acid batteries typically aren't favored, but I've had wonderful service out of them.
?
I run two SLR5700s on our school district VHF repeater system at full power.? Also being transportation director for the school district, I had access to purchase school bus batteries at roughly $100-$120 each.? I have run each repeater to its own battery, depend only on the SLR's internal charger, and generally replace the batteries every four to five years.
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As for how long they last, I do not have accurate specs on their amp hour capacity, but several years ago when we did not have the permanent setup yet, I had to use an extension cord run across the room to plug the repeaters into the only plug in the room.? One day I needed the extension cord for a different purpose, so I said "It'll be OK to run on battery a couple hours while I borrow the cord."? Almost a week later, I walked into the radio room and noticed that there was no extension cord laying on the floor.? I had forgotten that I borrowed the cord, and we had run almost a week of operations on battery alone.
?
Nathan
K5NDW

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