sorry, another battery question

[Newport41]

So we need to replace our 2 8D batteries. We've decided on wet cells and we had planned on buying two new deep cycle high end 8D's. The guy at the local battery shop has more or less sold me on the idea of buying 4 t-105's from trojan. They're 225Ahr 6volt batteries for $130 a piece. This would end up being much cheaper than buying two surrette 8D's. Any input on pros and cons of one set up vs. the other? I know that the four 6 volt batteries will be the better deal but will they hold up for offshore cruising. I'm looking to creat a 400Ahr house bank figuring daily consumption at less than 100Ahr and we'll be able to offset that largely with a wind generator and two 75w solar pannels. Also, any experience with Trojan batteries in general? Thanks in advance.

[sailingdog]

I think you'll find that the four T105 batteries will hold up at least as well as the two 8Ds. While the wiring is a bit more complicated, as you have two have them setup in two parallel sets of two in series, it can be much more convenient to position them, load them and work with them, as the T105 is much lighter than an 8D battery is.

Most golf carts are used in what is a relatively abusive manner for batteries...and these are designed to work in such conditions and keep working. I've used them on most of the boats I've owned, and have a house bank of T105's on my current boat...and I believe that they're also Trojans.

[btrayfors]

I've used, written, and researched golf-cart batteries for years. I have 8 T-105's on my boat, and four at my house!

The T-105's are very well known to the cruising community, and are a good choice for relatively economical, dependable, cruising batteries. They have recently gone way up in price, however. They used to sell for $70 each, but now are $115 and more. Part of this increase is due to manufacturing costs, but part seems to be due to the fact that Trojans have a good reputation and they can get the higher price.

You might wish to invest in a set of WaterMiser caps (about $6-7 each) to install on your T-105's. They will greatly reduce the need for watering. HydroCaps will do the same thing, but they're a bit more expensive and have to be removed during battery equalizing.

Most people get 3-5 years service from these batteries. Surettes/Rolls batteries are industrial grade and will give approximately twice the length of service but are, of course, much more expensive.

The secret to long-life is full charging and relatively shallow discharging, say, not more than 50% discharge on average. Less is better. Float voltage for T-105s is 13.5VDC, while absorption voltage is 13.8-14.1. Be sure your batteries are well charged and maintained in a charged condition as much as possible.

Hope this helps a bit.

Bill
S/V Born Free

[camaraderie]

Ditto on Bill's comments. He be da man on batteries (if not politics !).
Only thing I would suggest is getting an even bigger bank of T105's if you have the space as discharging to say 70% even further enhances battery life and gives you room for error in your use assumptions. Make sure you get a good discharge and 14.3V+ charge into them once every couple of weeks at least while cruising as passive stuff like wind/solar often does not do this well.

[KeelHaulin]

I have found a good source for some really nice AGM batteries. Cell phone towers require battery bank back-up using large banks of 12V UPS batteries. These batteries are generally sitting idle for 3 years or so and after that point it is required (by the FCC I think) that they be replaced with new units. These AGM batteries are huge; ~130 Ah, and weigh about 100 lbs. A guy who has a business replacing these batteries sells them to the local HAM radio club members for 20 bucks each! I have two installed in my boat currently (also a Newport 41), and plan to upgrade to 4 soon. Although they are a little tall; they fit perfectly in place of the two flooded MegaTron Marine batteries that were on my boat.

If you can find a local company that replaces these batteries it would be great to recycle them into your boat instead of going to the lead recycler with such little net "use" on them.

The 225 Ah rating is for 6v, which means that two batteries in series will give 225Ah at 12v; or 112Ah for each battery @ 12v supply. You probably know this already; just pointing it out for other thread readers...

[georgebanker]

http://store.solar-electric.com/batwatmiscap.html @$3.88.

[svsirius]

The other option from the Trojans is looking at Rolls/Surette's industrial line. Those have heavier plates etc and can give more capacity for a given space. They are general sold as 2v cells that make up a bank. Useful life can be in the 7-10 yr range. The Trojans have a good repution for value but Evans Stargazer recently had problems with a new bank.. posted on the SSCA board. So if you go that route check the batteries before you leave the store.

[sailingdog]

The only problem with the Rolls/Surrette industrial line is that instead of two batteries in series you need to have six per 12V bank, which makes the wiring both more complicated and more expensive. Also, believe the T105's are cheaper per WH.

[Newport41]

Thanks for the input. I think we're going to go with six t-105's. That will give us a 675Ahr 12v house bank. All for only $780 CDN. I figure that should be good for a boat with minimal electronics, well insultated refridgeration, and LED lights.