Numerous 12v SLA batteries. How would you keep them all charged?

[Ed.Kloonk]

I have 6 7Ah SLA batteries and also a couple of car batteries. I have a few of different battery chargers, mainly the CTEK 10A and 5A. I only need to use one of the batteries very infrequently tho.

I am currently rotating the batteries and the chargers, attaining mixed results mainly due to my forgetfulness. Would prefer a more set and leave solution for all of them. 

Is parallel charging random batteries really such a dirty word? 

Your thoughts..

[tautech]

I am currently rotating the batteries and the chargers, attaining mixed results mainly due to my forgetfulness. Would prefer a more set and leave solution for all of them. 

For the SLA's get the correct charger as 5A or 10A will damage them !

Get some reminder system like marked on the kitchen calendar to freshen them up on day 1 of the month.
Place them somewhere where you walk past them everyday and use a charger with a power ON light or charged light so you can see their state at a glance.
SLA's can withstand a longer shelf idle time than car LA's which you should consider freshening every 4 weeks max.

[Ed.Kloonk]

Good to know.

[tautech]

For your 7AH SLA's something like this would be fine:
https://www.jaycar.co.nz/12v-1a-sla-battery-charger/p/MB3619 (NZ pricing)

Typically you want to keep the charge rate under 1/10C which for them is 700mA.
Before I got a suitable charger we used to place a auto bulb in series with one of the charging leads and when the dim glow extinguished it meant they were close to charged when the current draw falls away. It works at a pince but the proper charger is always better and offers longer battery life.

Done a lot of spotlighting with SLA's and learnt in particular the first signs of dimming light is when to switch to another battery as SLA's don't like being drained flat.

[Electro Detective]

Perhaps get some cheap 24 hour timers in on the action 

'cheap' that work = I haven't had a lot of luck with those generic gear grinders or the digital types

i.e. keep the receipts so you can return any dud ones

[Ed.Kloonk]

Perhaps get some cheap 24 hour timers in on the action 

'cheap' that work = I haven't had a lot of luck with those generic gear grinders or the digital types

i.e. keep the receipts so you can return any dud ones

I've noticed this with timers too. The plastic override switch seems.. plastic-y.
The whole feel of the timer in the hands doesn't instil very much confidence. We've got a Kambrook timer from the '80s, underneath a fishtank or something. Still going strong. AFAIK.

[Ed.Kloonk]

For your 7AH SLA's something like this would be fine:
https://www.jaycar.co.nz/12v-1a-sla-battery-charger/p/MB3619 (NZ pricing)

Typically you want to keep the charge rate under 1/10C which for them is 700mA.
Before I got a suitable charger we used to place a auto bulb in series with one of the charging leads and when the dim glow extinguished it meant they were close to charged when the current draw falls away. It works at a pince but the proper charger is always better and offers longer battery life.

Done a lot of spotlighting with SLA's and learnt in particular the first signs of dimming light is when to switch to another battery as SLA's don't like being drained flat.

That's a good idea.

[john61ct]

As long as Float V is set as per mfg spec should be fine to leave hooked up.

But better to do a full Absorb cycle once every 2-3 weeks, then isolate.

Parallel 3 at a time is NP.

[f4eru]

I recommend using a specific SLA maintenance charger.
I have this one :
https://www.pulsetech.net/pro-12-redipulse-12-station-battery-maintenance-unit-gsa-dod.html

https://www.pulsetech.net/store/12v-24v-battery-chargers/12v-maintenance-chargers/pro-12-rp-redipulse-12-station-battery-maintenance-system.html

[nctnico]

I recommend using a specific SLA maintenance charger.
I have this one :
https://www.pulsetech.net/pro-12-redipulse-12-station-battery-maintenance-unit-gsa-dod.html

https://www.pulsetech.net/store/12v-24v-battery-chargers/12v-maintenance-chargers/pro-12-rp-redipulse-12-station-battery-maintenance-system.html

This is the best solution. Lead batteries may seem rugged but they aren't at all. It takes great care to keep them in perfect condition.

[john61ct]

FLA are certainly more rugged and forgiving, last a lot longer than sealed everything else being equal.

There is no chemistry that can just sit ignored for decades.

[nctnico]

FLA are certainly more rugged and forgiving, last a lot longer than sealed everything else being equal.

But you can still screw these up by bad charging and discharging. An old customer of mine refurbishes FLA batteries. They exist due to the many bad chargers out there.

[john61ct]

Yes true for any battery chemistry.

But among lead compared to AGM or GEL, FLA has a wider range of V&A that's acceptable,

can't be damaged by holding Absorb too long, or charging at "too high current", so long as you keep water level topped up.

and not getting to 100% Full as per endAmps spec so frequently, does not reduce lifetime as much.

Firefly being an exception to the latter among AGM, as long as you follow tgeir capacity restore protocol.

I've seen Rolls / Surrette banks go 15+ years and still over 75% SoH!

[james_s]

Perhaps get some cheap 24 hour timers in on the action 

'cheap' that work = I haven't had a lot of luck with those generic gear grinders or the digital types

i.e. keep the receipts so you can return any dud ones

I've noticed this with timers too. The plastic override switch seems.. plastic-y.
The whole feel of the timer in the hands doesn't instil very much confidence. We've got a Kambrook timer from the '80s, underneath a fishtank or something. Still going strong. AFAIK.

That's disappointing. I have several Intermatic lamp timers from the 80s and 90s that are still going strong. Had a few of them crap out but I don't think I've ever had one last less than a decade.

Figures that everything has been cost reduced to the point of being junk though.

[NiHaoMike]

A small solar panel and charge controller will work nicely.

[Ed.Kloonk]

A small solar panel and charge controller will work nicely.

Yes, yes it would. (he said sheepishly)

I have these items laying in my junk bins. 

[Ed.Kloonk]

I recommend using a specific SLA maintenance charger.
I have this one :
https://www.pulsetech.net/pro-12-redipulse-12-station-battery-maintenance-unit-gsa-dod.html

https://www.pulsetech.net/store/12v-24v-battery-chargers/12v-maintenance-chargers/pro-12-rp-redipulse-12-station-battery-maintenance-system.html

I'll tell Santa that is what I want. In the meantime, I'll take NiHaoMike's suggestion and run with it by stringing several solar chargers together. Calling this one The Frankencharger.

[Red Squirrel]

Pretty much any 13.5v supply would work.  You can leave it on indefinitly, or have it on a timer to run for like an hour every day.  I would be tempted to put them all in parallel but probably best to keep them separate.  So one psu for each.

In fact if you find yourself in a need to keep a bunch of batteries on maintenance all the time you could even build a rig that uses relays to switch between each battery and have a bunch of leads.   Could do 6v ones too with a separate psu. 

Can't hurt to do equalize once in a while but ideally you don't want to go too far with that on sealed batteries.

[vasonline]

I have a small solar 18V panel (10-20W) with a PWM controller (EPSolar) connected to some spare AGM batteries.

Greetings,
Steven.