15" Powerload split shaft string trimmer with or without 2.5 battery?

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I've decided to buy the ST1521S 15" Powerload split-shaft string trimmer; now I need to decide if I need to get the 2.5ah battery with it or get it without the battery.  I currently have a 7.5 battery that still has at least a 25% (maybe a little more) after I mow with it, and a 2.5ah battery that came with my blower. 
If I want to buy string trimmer by itself, I think I can use the 7.5 Ah battery with the mower and blower and still have a little battery life to spare, and then use the 2.5 Ah battery I already have with trimmer; I was told by Ego that I should about 40-45 minutes of use with the 2.5 battery on the string trimmer, which should be more than enough for my yard. 
However, the string trimmer with the battery is only $60 more than the trimmer alone ($229 vs. $169), and a stand-alone 2.5 battery by itself is $145 at Home Depot!  Does anyone know if a never-used battery will stay good for several years, and if so, for how long?  I'm wondering if it makes sense to just buy trimmer/battery combo and just store the battery for a few years until I need, but I don't want to wait until then and find out I just have a dead battery.  
Finally, can the plastic guard at the bottom of the trimmer be removed and the trimmer still work?  I'm wanting to use my trimmer to edge, but I think the guard might get in the way of my sight line.  
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dk cromwell

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Posted 1 year ago

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David HD, Champion

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For EGO tools, it's always more "economical" to purchase the whole kit (tool, charger and battery).  This way, you will always have an extra battery as a "backup" in case one of your other batteries malfunctioned.  Thus, I would buy the whole kit for $60 more ... :-)

You mentioned about storing the extra battery for a couple of years.  Keep in mind that all EGO batteries have a 3 Year Limited Warranty from the date of purchase - not the manufactured date listed on the battery.  And if you decided to store it for 2 plus years, then make sure to do the following to ensure long-life of your battery!

For Lithium-Ion battery pack storage longer than 30 days:
  1. Store the Lithium-Ion battery pack where the temperature is below 80°F (26°C) and free of moisture.
  2. Store Lithium-Ion battery packs in a 30%-50% charged condition.
  3. Every six months of storage, fully charge the Lithium-Ion battery pack.
  4. EGO battery pack is equipped with an advanced self-maintenance function. It can maintain 30% of its charge capacity automatically after it is stored over one month.
Lastly, you were thinking of "removing" the plastic guard to enhance your edging capability.  I don't see why this would not work, but you would increase your chances of getting debris hitting your body during trimming and edging.  I am "horrible" when it comes to using the trimmer for edging, so I invested in the Power Head & Edger Attachment for this job.  Good luck with your purchase and let us know which route you decided on ... :-)

(Edited)
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dk cromwell

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Thanks David!  If I were to keep a new battery in the conditions you describe above, any idea how long it should last, keeping a full or close to full capacity?
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David HD, Champion

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According to Battery University, Li-ion batteries are rated between 300 - 500 charge cycles.  So if you take the average, then you should be around 350 charge cycles.  If you plan to charge your battery every 6 months, then it could last you 175 years without ever using it (not sure if the battery will last that long).  That said; I have a feeling you will be using this battery more often than you originally planned.  Below is a link to a similar question from a year ago, a good read if you have extra time:

How I came up with 175 years (rough math, not scientific by any means):
  • 2 charges per year
  • 350 charge cycles / 2 charges = 175 years

https://community.egopowerplus.com/ego/topics/curious-on-battery-life?topic-reply-list%5Bsettings%5D...

Keep in mind, EGO battery pack is equipped with an advanced self-maintenance function to extend the battery life. Depending on the battery charge, it will automatically perform a self-discharge operation after one month of storage. After this self-maintenance, the battery pack will enter sleep mode and maintain 30% of its charge capacity.

If stored for a month or longer, fully recharge the battery before the next use. It is not necessary to run down the battery pack charge before recharging. The Li-on battery can be charged at any time and will not develop a “memory” when charged after only a partial discharge. Use the power indicator to determine when the battery pack needs to be recharged.

(Edited)