You are correct with that statement on 8 to 25a but should look only toward the lower limits, eg 8 to 12 Amps. 85ah bat will take approx. 10.5 hrs to charge at 8 amps. I personally wouldn't charge that size battery of any make or composition higher than 8amps.
Be very careful with AGM (Glass Matt0 and GEL batteries. If you charge with conventional chargers at high amps you WILL destroy the battery. Gel batteries will harden gel around plates and destroy it. AGM have there own set of issues.
The end note is if you do have a smart charger you will be fine, it will take a few hour to charge but it will do it safely and effectively, if you don't have one, I would avoid charging the said batteries mentioned above. The other important note is the output voltage. Different types of batteries require different voltage. Some charge between 13.8v - 14.2 standard lead acid and some require 14.8v.
Hope this help in your decision.
Quote:
Originally Posted by naskies
The conventional wisdom that I've been repeatedly told is to use a charger of around 10-30% the battery capacity to preserve battery life. For example, for an 85 Ah you'd want a charger between 8 and 25 A.
I don't know how true or not this is. Aside from low-charge states being bad for deep cycle batteries in general, I don't know if there's something particularly bad about charging slowly.
**Some deep cycles (remember you get LEAD acid, gel, AGM) require bigger hits to get them up to 90 of full voltage then the charge backs them down for lower amps for the last 10 or so percent.
If you do get a new charger down the track, it might be handy to keep an eye out for one with "power supply mode" that provides a constant 13.8V.
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