# AGM batteries anyone used these?



## major (Apr 4, 2008)

Coley said:


> Just happened to find this while looking for batteries for my Yugo.
> 
> eBay item number:161387065210



Look like UPS batteries. Not deep cycle. Likely a poor choice for EV.

At 18 cents/Wh nominal Pb-Acid where you'd be lucky to see half the nominal rated energy in an EV application, Lithium cost is about the same (for the cells). True, you'd need installation cost including charger, BMS, etc. I'd at least stick with what you know works, or look to upgrade to Li.


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## Coley (Jul 26, 2007)

I have been using some these in used condition and done well with them.

281567754730 ebay #.

So I thought these should be about the same.

381131875447 ebay #

Time will tell


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## major (Apr 4, 2008)

Coley said:


> I have been using some these in used condition and done well with them.
> 
> 281567754730 ebay #.
> 
> ...


Those are not AGM batteries. They are gel type. And I did not see where either stated "deep cycle" or mentioned cycle life, so it is likely to assume they are not intended for deep cycle use and would therefore result in short life. 

But whatever works for you


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## Sunking (Aug 10, 2009)

Gels are not good except in Emergency lighting.


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## Coley (Jul 26, 2007)

Gels are so much better than regular deep cycle LA batteries that there is no comparison.

I get 55 mph for my 8HP Yugo that lasts longer overall than regular deep cucle batteries.

The price difference is the killer.

I have a friend that is handicapped and he saves his one year old mobility batteries for me.

I ran some that were 3 and 4 years old and still going strong up until last year. They also charged up faster .

Looking at these for a new set of 6.
381131827420

They compare well with what I was using, but at a much better price + free shipping.

I will post how they work out.


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## major (Apr 4, 2008)

Coley said:


> Gels are so much better than regular deep cycle LA batteries that there is no comparison.


Why don't golf carts or industrial battery powered vehicles use them (gels)? Answer: Because they are not better. But if they work for you, great. 

I like the fact that you have converted an older small car with a low voltage Pb-Acid set and use it as much as your EVAlbum page indicates. Even sometimes recycling or re-purposing used batteries. Proves that a short range EV can be practical. And that you don't need to spend a fortune to convert one.


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## Sunking (Aug 10, 2009)

major said:


> Why don't golf carts or industrial battery powered vehicles use them (gels)? Answer: Because they are not better. But if they work for you, great.


Nor does Renewable Energy systems use them either them for 3 very good reasons. 

1. Gels must be charged slowly and at lower voltages. They will not tolerate any over charging, or charged too fast. The electrolyte is gelled and if charged too fast or over charged dries the gel out forming cracks and voids in the electrolyte. The damage is permanent causing loss of capacity and cycle life. 

2. Gels have higher internal resistance than their FLA and AGM brothers. That means more voltage sag under load, slower charging rates, excessive Peukert losses, and prone to thermal runaway. 

Very low cycle life making them only suitable for Emergency Backup like Emergency Egress lighting where they can be slow charged and rarely used. 

3. Cost effectiveness is poor costing twice that of FLA and 1/3 the cycle life making them long term so 6 to 10 times higher than FLA.

If you have an application that cannot tolerate spills using Pb the right battery choice is AGM, not Gel. AGM have very low internal resistance meaning they can be charged and discharged very fast with decent cycle life and cost less than Gel long term.


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## miev 1 (Jan 22, 2015)

Sunking said:


> 2. Gels have higher internal resistance than their FLA and AGM brothers. That means more voltage sag under load, slower charging rates, excessive Peukert losses, and prone to thermal runaway.
> 
> Very low cycle life making them only suitable for Emergency Backup like Emergency Egress lighting where they can be slow charged and rarely used.
> 
> 3.


Have used lead acid emergency light batteries in a quad I rigged for my daughter. What about the newer Li ones - or are they slow charging and <cycle recharge count?


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## Coley (Jul 26, 2007)

I have a couple of handicapped friends that use GELs in their chairs and they hold up well.

They charge as well as regular deep cycle batteries and last longer.

They also come back up on their own after a hard use session.

Winter storage is no problem, as they hold a good charge all winter.


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## PStechPaul (May 1, 2012)

I used a 17 A-h gel-cell battery in my EV tractor experiment and I think it has a 1999 date code. I had left it untouched for over a year as a starter battery in a gas tractor and it still held decent charge. I haven't used it heavily, but it still holds a charge after 15 years. That's pretty good. And I bought it used for about $10 at a HamFest.

I also have four 12 A-h gel cells (SLA) that I got on eBay for about $50, and they seem to be holding up well after a couple years, but only lightly used. They should be OK for a tractor or limited use small EV. That works out to $87/kW-h. I also have a Walmart 12V 100 A-h deep cycle marine battery that was about $80, which is about $67/kW-h. The cheapest LiFePO4 I have found is about $300/kW-h. But if they have twice the real capacity of SLA and last 5 times longer in full size road vehicles, then that becomes a real lifetime cost of $30.


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