The key word is 'optimum', Colin. Anyone can charge a battery with anything, but there is an argument that to get the best performance from an AGM you need to be putting in a high current.
http://forums.catalina.sailboatowner...d.php?t=124973 explains it far better than I do.
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31-01-12, 09:21 #41
Last edited by demonboy; 31-01-12 at 09:30.
31-01-12, 10:10 #42Guest
Location : London
- Join Date
- Jan 2004
And, since the internal resistance is extremely low, there is almost no heating of the battery even under heavy charge and discharge currents. The Concorde (and most AGM) batteries have no charge or discharge current limits.
31-01-12, 11:29 #43New User
Location : Sydney
- Join Date
- Dec 2011
If you are going to charge or trickle charge a 12V gel battery, it requires no more than 13.8 volts at full charge, and 13.2 volts at “maintenance/trickle” charge. Make sure that your charger either analyses, or can be set on, the lower voltage. Standard charging at 14.8 volts (or more) will cause the gel to dry and reduce life and cranking capacity. Charging at no more than 2 amps is also suggested.
04-02-12, 14:05 #44Registered User
Location : Brighton
- Join Date
- Aug 2008
An advantage of AGMs is that they will take high charge rates but it's not essential. Those sort of charge rates will only occur if you have taken the state of charge lower than you should anyway.
Having said that you don't want to charge too slowly, I would suggest having at least 20% (i.e. 20A per 100Ah) available.
Anyway that's incidental. FWIW I would have made the same choice as you have. I wondered if you'd got off the fence yet!
06-02-12, 07:49 #45
Yes, I'm off the fence and sitting firmly in one camp now, Troubadour! Still waiting for the delivery of said batteries, mind, so I'm not a 6 volter just yet but the important step forward is me changing my mind about wets.
12-04-12, 23:04 #46New User
- Join Date
- Mar 2007
Can anyone comment on the suitability of wet cell lead acid batteries when they are located underneath sleeping accommodation? I don't have any issue with maintenance regime, but what about danger from gas emissions? My last set of AGM's (4 * 100amp hr) lasted only 2 years, so assuming there is no health issues, I will revert to wet cell type. Also need to replace bow thruster / windlass battery bank (currently 5 yr old Optima RedTop) but I wonder if wet cell batteries will cope with the pounding as they are situated in the bow.
12-04-12, 23:47 #47Narrowboating From Stretford!!
12-04-12, 23:53 #48
I've got three flooded batteries under my berth. Only caused a problem when the old shore power charger went berserk and boiled everything dry."Beer is proof that god loves us and wants us to be happy" B. Franklin
13-04-12, 08:29 #49
Not all AGMs are the same - check they are made for deep cycle use.
13-04-12, 22:12 #50
I've just replaced my batteries and purchased 4 Trojan T105s and one Optima Red top 4.2.
Everyone will have different usage patterns and life requirements vs. cost. All I can say is that I'm happy to maintain batteries and the cost was acceptable. I downloaded a spreadsheet that allows comparison of battery types. After entering my own power usage data it appeared to support purchase of AGMs. However, when I updated the actual UK purchase costs for AGM & T105s the picture changed completely.
So I decided to stick with flooded lead acid deep cycle batteries on a cost basis despite other disadvantages. However, I was worried about the lack of ventilation in the battery compartment. The original batteries were in an unvented locker underneath the berth in the aft cabin. I haven't had any problems but was surprised that the builder didn't think it was dangerous. I suspect that the charging regime is conservative but still noticed discolouration of the locker lid.
I'm currently installing a brushless vent fan with ducting to the stern.
So my opinion is that flooded batteries underneath a berth will work. However, if you want to charge more rapidly a ventilation system rapidly becomes a neccessity to keep Hydrogen concentration well below 4%. I'm aiming for <0.5% at point when gassing will be greatest.