New Batteries: Gel or AGM?

[nigelmercier]

I've decided it's time that I invested in a new "Domestic" battery bank, the old batteries are well past their useful life. The existing bank is around 400AH, and I don't think this is enough for our current usage, so I'd like to increase it to around 600AH.

Has anyone done recent research into the best technology for a domestic bank? I've read Nigel Calder's excellent Mechanical and Electrical Manual, but the last reprint was in 2005, and I believe that AGM batteries have improved since then.

 

[[2574]]

This subject leads to madness......

I've recently been through the whole gambit including the alternator and regulation thereof. I ended up with Lifeline 2 x 8D's giving me 510AH + "flash" start battery. You'll be advised to go to traditional, spiral and AGM in equal amounts with good arguments to back up each proposition. You'll hear about fast charge acceptance rates from AGM's but them not being good in hot weather (can't replace the electrolylte) etc etc etc........

Why did I end up with Lifelines? Size was important - the configuration fitted my battery box and I was also very attracted to the non-gassing aspects of sealed AGM's producing no explosive gas whatsoever. The batteries can also be installed on their side, end or even upside down. So I figured that if ever we get knocked over then there's no battery acid to worry about either. I think that battery regulation is very important with AGM's - if you cook the batteries you've knackered them - you can't just add some distilled water! So I went for an advanced alternator regulator (not a voltage booster a la Adverc et al) that had an AGM configuration and would float the batteries at 13.4v. Ditto the Victron 70A charger. Many regulators/chargers float at 13.7v. So sensitivity to overcharging was another thing quoted against AGM's and I suppose if you've got a setup which is not well regulated this would be a negative.

I have been very pleased with the installation - in as much as one can be pleased with a battery bank! it has done what it said on the tin. I'm now off down the other route to madness which is Solar PV and windcharging ~ finding a regulator that will float at 13.4v is proving quite challenging!

rob

 

[npf1]

Robinh - re suitable solar regulator, have a look at the Xantrex C range as they have adjustable bulk and float voltage levels (well ... I know the the C40 does and I think the other are the same, just lower capacity)

 

[HoratioHB]

Posted this elsewhere - when I get back to Trinidad I am going to 'invest' in 4 deep cycle 6v golf cart batteries. I currently have 4 12v sealed lead acid batteries which are starting to perform poorly after only 6 months on board (not helped by a duff shore charger - I eventually discovered). These golf cart batteries are much cheaper than 'marine' ones and designed for a regular charge/discharge cycle. So on two fronts they should be good - easy and cheap to replace if necessary but by all accounts more likely to last longer anyway!!

 

[ccscott49]

I would go with AGM, thats what I did after going the wet lead acid, sealed lead acid route, I find them bvery good so far, but as Robih says, the float voltage is critical, they do not like being over charged.

 

[pyrojames]

That is my plan also. With a cost at less than half per AH compared to Gel/AGM, and a robustness to mistreatment, I can see little reason not to go down this route.

 

[jeremyshaw]

Another argument in favour of golf cart batteries is that the format can help you get more power per area.

I replaced my bank with US Trojan T105s and for 1cm extra floor space got the capacity up from 640 to 1050amh - they were taller. Also, being 6 volt batteries (you pair them up to make 12) they are individually substantially lighter, so easier to handle and install. The whole lot cost me less than I'd paid in Levkas for sealed lead acids 3-4 years before. (It helps that the dollar is so cheap now).

I personally stick to lead acid because I figure that at some point my batteries are going to get abused by someone. But the other technologies have their points too and a lot comes down to where you are going to use them, how you are going to use them and how you are going to charge them.

 

[[2574]]

Thanks for the tip!

rob

 

[Anonymous]

I would have gone for Trojan golf cart batteries but they too high for my battery area and would have taken a lot of modifications, so I bought Lucas semi-traction flooded lead acid batteries so I can add water. I fitted ours in January 2005 and all indications are that they are performing as new after 3.5 seasons use and year round liveaboard use (float charged). For liveaboard cruisers, I think that on the whole good branded batteries are best whether you go for flooded, gel or AGM.

My yacht had very expensive Sonnenschein GEL batteries only two years old (of which only one year in full service) when I bought her. The batteries failed catastrophically after a few months. Due, almost certainly, to overcharging. I suspect by the engine alternator, which is not controllable.

Aside: Please note that neither Adverc nor Sterling can necessarily cut back your charge. They can only boost the charge voltage, not reduce it from the preset regulator setting. You can get round it by adding a couple of diodes but my point is that many people seem to be mislead into thinking that because they have a Sterling or an Adverc they necessarily have full three or four step charging. They might, but then again, they might not, it needs checking.

 

[pvb]

Provided the bank is big enough (and 600Ah is), I'm a firm believer in sealed maintenance-free lead acid batteries. They're clean, safe, fit-and-forget. I've had a domestic bank of 6x115Ah Delco batteries for about 10 years, and they've been no trouble at all, with charging by alternator with an Adverc controller. They started to lose capacity last season, so I've just replaced them with 6x113Ah Merlin Powerpack batteries (from Merlin PowerStore). These are very similar in design to the Delcos, with lead-calcium plates to resist overcharging, and are constructed to withstand fairly harsh cycling. Best of all, they're only about £80 each - about a third the price of decent AGM batteries.