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Gel Cell Charger Deals — Parallax Forums

Gel Cell Charger Deals

ercoerco Posts: 20,256
edited 2013-04-24 02:09 in General Discussion
Lead acid ain't sexy. Not high-tech. Low power to weight. But... pretty safe (they don't explode like some Lithium batteries have), cheap and plentiful. Used in many alarm systems, and some robots. We've all got 'em, I've used 'em. Even as I transition to lithium, my numerous old gel cells are useful for testing and more. Here are some cheap chargers I've seen (and ordered) lately:

12V/$4 http://www.goldmine-elec-products.com/prodinfo.asp?number=G19029 "smart" charger uses an external relay to disconnect power cube when fully charged sale ends April 16

12V/$5.51 free ship http://www.ebay.com/itm/181060264290 appears to be a float charger, based on description at http://www.aliexpress.com/item/12V-Volt-Rechargeable-Sealed-Lead-Acid-Battery-Charger-free-shipping/624988081.html

6V/$5.51 free ship http://www.ebay.com/itm/181062310876 better description at http://www.aliexpress.com/item/6V-6-Volt-Sealed-Lead-Acid-Rechargeable-Battery-Charger/545730265.html

Here's a good deal on a new 6V, 4.5Ah battery w/free ship for $9.10. Lead acids are heavy, often garnering high shipping prices. http://www.ebay.com/itm/6V-4-5AH-Sealed-Lead-Acid-SLA-Battery-for-Home-Alarm-Security-Systems-/140944681270?ssPageName=ADME:X:RTQ:US:1123

That seller has lots of other battery deals, worth a peek.

Comments

  • CuriousOneCuriousOne Posts: 931
    edited 2013-04-14 22:08
    recently, price of quality gell cells increased so much, that it now is almost equal to lithium prices
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2013-04-15 03:59
    There is indeed something happening in the market for lead batteries in general. Some say it is driven by China's vast demand for automobiles.

    I started out with 6 volt and 12 volt gel cells and related chargers, but kept finding the 6 volt cells were a bit too low for voltage regulators and the 12 volt cells were a bit too high.

    Then I discovered I could locally buy 8 volt gel cells with 9AH rating and I could simply trickle charge them with a 500ma 9 volt DC wall wart. Life had never been the same.
  • Peter KG6LSEPeter KG6LSE Posts: 1,383
    edited 2013-04-15 09:25
    the problem is that those are NOT Gel cells but rather just AGMs ................No One uses real gels any more sans a few nitch apps ..


    tonight If Iam not dead from my cold . Illl pop open a 7 AH 12V AGM and show yall then insides .

    the issue here is not in a name but how Real GCs have far different charging requirements then a Flooded and a AGM ..... the latter 2 have far more in common ...

    http://bdchargers.com/batterytypes.php


    AGM batteries can do anything that flooded and GEL batteries can do, just better.
    90 % of the black case small batts you buy are AGMs now ......

    the seller on the 6V 4.5 AH states its a AGM .....

    * Absorbed Glass Mat (AGM)
    * Maintenance Free battery
    * Non Spilled
    * High Performance
    * Best Battery Life
    * Safety in all Positions



    Peter...
  • Kenny GardnerKenny Gardner Posts: 169
    edited 2013-04-15 11:14
    erco wrote: »
    Here's a good deal on a new 6V, 4.5Ah battery w/free ship for $9.10. Lead acids are heavy, often garnering high shipping prices. http://www.ebay.com/itm/6V-4-5AH-Sealed-Lead-Acid-SLA-Battery-for-Home-Alarm-Security-Systems-/140944681270?ssPageName=ADME:X:RTQ:US:1123

    That seller has lots of other battery deals, worth a peek.

    I wonder if those would work for a Hero 1 ?

    Kenny
  • ercoerco Posts: 20,256
    edited 2013-04-15 17:43
    Kenny Gardner wrote: »
    I wonder if those would work for a Hero 1 ?

    Kenny

    Sure should. Hero 1 used 4x 6V batteries, IIRC.
    Another option is to use a 12V 7Ah battery (same battery volume) and wire in a zener diode to provide 6V for the logic, per http://hero.dsavage.net/robots/Hero_FAQ.html#2.5.1
  • ercoerco Posts: 20,256
    edited 2013-04-20 20:07
    I ordered the 12V charger which just arrived. It works quite well and actually feels like a quality unit. It's a 1A high-frequency switching circuit for charge (red LED) which switches to float charge (green LED) ~50 mA. Big beefy wires & big heavy duty alligator clips. My 12V SLAs are happy and topped up. Scooooooooooooooooore!

    So naturally I just ordered a 6V charger too.
  • prof_brainoprof_braino Posts: 4,313
    edited 2013-04-22 19:02
    Peter KG6LSE wrote: »
    the problem is that those are NOT Gel cells but rather just AGMs ...

    http://bdchargers.com/batterytypes.php

    Thanks for that link, thats what I needed to know.

    But what is the problem with AGM? From the article they appear to be the best general choice?
  • Peter KG6LSEPeter KG6LSE Posts: 1,383
    edited 2013-04-22 21:27
    AGMs are in all the ways I can think of better then gel cells ,
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2013-04-23 01:14
    Peter KG6LSE wrote: »
    AGMs are in all the ways I can think of better then gel cells ,

    Not in terms of expenses.. they are more costly.
  • RobotWorkshopRobotWorkshop Posts: 2,307
    edited 2013-04-23 07:55
    erco wrote: »
    Sure should. Hero 1 used 4x 6V batteries, IIRC.
    Another option is to use a 12V 7Ah battery (same battery volume) and wire in a zener diode to provide 6V for the logic, per http://hero.dsavage.net/robots/Hero_FAQ.html#2.5.1

    I wouldn't recommend that option. You can easily user a 12V 7AH for the motor drive and just keep a pair of 6V batteries for the logic. That is a nice upgrade since it gives more capacity for the motors. If you have to use a 12V battery for the logic then a better option would be one of the small 3-pin 6V switching regulators.

    If you are charging the batteries directly then make sure the robot is switched off and the original charger is unplugged.
  • Peter KG6LSEPeter KG6LSE Posts: 1,383
    edited 2013-04-23 21:51
    MK whom makes then clearly states they ( gells ) are a higher initial cost ..

    Attachment not found.
    most of the smaller then 50 AH batts you see are AGMs ,/ No one cares about super duper deep cycle life In stuff We make here ...

    ll bet the most common Pba batt we use is the 7 AH 12V class . Perhaps the 5AH class too . this is a Very small batt as far as the batt world goes ...
    Most Gels START at 30 AH ,,,, your medusa or home bot is not gonna use a 30 AH batt.....
    What you see on the shelf at rad shack and what you have in the spiral cell car batt and in in most every UPS is a AGM batt .
    Only people I know that willfully use a True GEL is in power chairs... ( 33AH or so class )
    and in some Low draw telecom backups .



    Attachment not found.
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2013-04-24 02:09
    It seems odd that one one is interested in 8VDC lead acid. This is a better overall fit for microcontroller projects.
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