Modifying small UPS

mwill

Active Member
Joined
Mar 12, 2010
Messages
91
That's great amongstthevotingfodder. When you have time could you give us some pointers on chargers, or have you already done that? And, please can you enlighten me to what an SLA is? Many thanks.:)
 

itareanlnotani

Executive Member
Joined
Sep 14, 2008
Messages
6,760
A simplified overview for you:

Basically there are two types of Lead Acid batteries (along with 3 sub categories);

The two main types are Starting (cranking), and Deep Cycle (marine/golf cart).

Starting
The starting battery (SLI starting lights ignition) is designed to deliver quick bursts of energy (such as starting engines) and therefore has a greater plate count. The plates are thinner and have somewhat different material composition. The deep cycle battery has less instant energy, but greater long-term energy delivery. Starting batteries are the ones we use in cars. They're not suitable for UPS's..

Deep Cycle
Deep cycle batteries have thicker plates and can survive a number of discharge cycles. Starting batteries should not be used for deep cycle applications because the thinner plates are more prone to warping and pitting when discharged. The so-called Dual Purpose Battery is a compromise between the two types of batteries, though it is better to be more specific if possible.

For storage purposes, you want deep cycle.

Wet Cell (flooded), Gel Cell, and Absorbed Glass Mat (AGM) are various versions of lead acid battery.

Wet
The Wet cell comes in two styles; Serviceable and Maintenance free.
Both are filled with electrolyte and are basically the same. Wet cell batteries need to be topped up with distilled water, and are less safe than the sealed ones. They're not sealed, and are "wet" batteries.

Sealed Lead Acid
Gel Cell and the AGM batteries use a gel instead of liquid inside, and are typically sealed. common names are "sealed regulated valve", "dry cell", "non spillable", and "Valve Regulated Lead Acid" batteries. In most cases AGM batteries will give greater life span and greater cycle life than a wet cell battery. These are all referred to as SLA (Sealed Lead Acid)

AGM: The Absorbed Glass Matt construction allows the electrolyte to be suspended in close proximity with the plates active material. In theory, this enhances both the discharge and recharge efficiency. Common manufacturer applications include high performance engine starting, power sports, deep cycle, solar and storage battery.
Typical lifespan of an AGM @ 40% DoD is about 300 cycles.


GEL: The Gel Cell is similar to the AGM style because the electrolyte is suspended, but different because technically the AGM battery is still considered to be a wet cell. The electrolyte in a Gel Cell has a silica additive that causes it to set up or stiffen. The recharge voltage on this type of cell is lower than the other styles of lead acid battery. This is probably the most sensitive cell in terms of adverse reactions to over-voltage charging. Gel Batteries are best used in VERY DEEP cycle application and may last a bit longer in hot weather applications. If the incorrect battery charger is used on a Gel Cell battery poor performance and premature failure is certain.

Lead Crystal is a newish variant of AGM/Gel battery that offers better cycle time, but isn't very good under load (high voltage droop).
Its proably the best choice right now if you want to go Lead Acid.

The charger you use needs to be appropriate for the battery type in use, otherwise its going to fail faster.
Charging Lead Acid is more of an art than a science. Lead Acid also has fairly crap capacity / weight ratios, and cost ratios.


My opinion is that Lithium (LiFePO or its sulphur variants) will wipe out Lead Acid in a fairly short period, as the pricing for Lithium is cost effective - its already dropped to similar levels as Lead Acid pricewise, and it gives far more capacity.
I forecast that in 3-5 years Lead Acid will be uncompetitive to Lithium.

Lithium doesn't need tweaked charging tech - its basically charge till you get to a specific voltage, then stop. It also can supply high currents without voltage droop. Lastly, it's also far safer.


Back to now though, stick to the same chemistry type you currently have in the UPS, as the charge circuit (should be) optimized for that Lead Acid battery type.
 

BigEars

Senior Member
Joined
Feb 22, 2015
Messages
533
Thank You Isheed_cn

You post will help a lot of people with rechargeable basics :D;)
 
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Nips

Senior Member
Joined
Jan 23, 2006
Messages
804
Great Info. Thanks. Glad I asked the question before getting the soldering iron out.
 

mwill

Active Member
Joined
Mar 12, 2010
Messages
91
Thanks Isheed_cn for that great post.

I have continued looking around and have found that Kariba Batteries here in PE not only sell batteries but chargers and inverters too, when they can get them. The guy there is very big on Lead Acid batteries and recommends the ACDelco deep cycle 105Ah selling at R1612. He also has a Hawkins 6amp smart charger for R992. That's the best option I have at the moment, then I need a pure sine wave inverter, 600, 800 or 1000watts. I can get a 600W one in PE for R2009 (in stock). You see some of the sine waves guys are getting when they put an oscilloscope on the inverter, quite bad looking..so you still don't know what you're getting. I suppose, follow the old maxim, only buy from a reputable dealer.
 

Arthur

Honorary Master
Joined
Aug 7, 2003
Messages
26,879
Another brilliant post by lsheed_cn. Thanks - always useful.

The surest way to wreck your system is to use the wrong charger for your battery type.

My solar pv system has silver calcium batts, which require a slightly higher voltage when charging. But they're better for higher ambient temps, which I have here in the Little Karoo.

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thehuman

Expert Member
Joined
Nov 2, 2004
Messages
4,240
Running 2 of those bateries . Need to get the victron programing cable to up voltage slightly
 
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