I know that charging sealed / AGM / gel cell lead acid batteries requires a special charger so they don’t get overcharged, overheated, boiled out, and destroyed.

Is it safe to use this special type of charger with a standard deep cycle flooded / wet cell marine or automotive battery?


1 Answer 1


No issues!

I designed SMPS battery chargers for a living and the only exceptions are some gel and AGM batteries which may need 100-200 mV more to get to 100 % SOC. Using a standard one which charges to 14.4 will undercharge said gel or AGM.

As for the opposite, using a 14.6 V charger for a normal battery, you are ever so slightly overcharging it. If it’s not sealed, I would just refill any lost water with destilled water. If however sealed, you will loose water over time if you charge it repeatedly.

Measure the termination voltage with a multimeter to be sure if in doubt.

  • \$\begingroup\$ I guess you meant it considering the charger is a smart charger or a 3-stage one. But if the charger is a “maintainer” or floating type, probably it provides 13.6~13.8V. In this case, battery would be less voltage sensitive to its constructive type than to an eventual ambient Temperature derating. If you have seen otherwise, please share your view. \$\endgroup\$
    – EJE
    Commented Jan 21, 2022 at 1:39
  • 1
    \$\begingroup\$ @EJE You loose water in several stages when charging lead-acid. At the end of the absorption phase, normally 14.4 V, water is lost so you want to avoid staying there longer than necessary. Float at 13.8 is very high, you would continuously loose water. 13.6 is a compromise between SOC and water lost. High end UPSes tend to go lower, about 13.4 V to increase battery lifetime at the expense of limited SOC. \$\endgroup\$
    – winny
    Commented Jan 21, 2022 at 8:05
  • \$\begingroup\$ Thanks for the info, +1 for it. If you could provide any references about that for further reading, it would be great, as Battery University does not pass such trade off. \$\endgroup\$
    – EJE
    Commented Jan 21, 2022 at 21:36
  • \$\begingroup\$ @EJE Sorry, only personal experience from working in the battery charging industry and talking to battery chemists. \$\endgroup\$
    – winny
    Commented Jan 21, 2022 at 22:16
  • \$\begingroup\$ That’s ok, don’t worry. Meanwhile I answered another post, and knowing your background and knowledge on the subject, I would appreciate to hear your comments to improve it. Here is the link, if you have the opportunity. electronics.stackexchange.com/a/605293/248404 \$\endgroup\$
    – EJE
    Commented Jan 22, 2022 at 2:00

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