Battery bank 50% failure

[geoff3nebel]

I have 4x T105 6v 225Ah in series+parallel, they are charged by 80A alternator, 150w solar, a Rutland 913 wind gen and when connected to shore power a Sterling 30A smart charger. I haven’t been aboard for three weeks and the boat has been in a marina - not hooked up to shore power.
I have sonic anti-fouling on permanently.
When I went on board today and checked the batteries I found two had blown out their electrolyte, were bone dry and are bulging. The other two are fine and delivering power. All four were bought together seven years ago. I now have to replace all four. My question is: why did two fail so spectacularly and two carry on as normal?

[Cheechako]

Wow, that is strange, although at 7 years you done good! I've had near-new batteries fail inside with a short, but no bulging etc. Is it possible they are shorted, been charged often, and you just didn't notice the bulge for a time?

[denverd0n]

Sorry to hear about your battery bank, and I don't really want to hijack this thread, but I would be interested in a review on the sonic anti-fouling at some point (another thread, perhaps).

[Oldwheels]

Another vote on the Sonic review please.
7 years on a lead acid battery. Pretty good. Without a balance system then you did very good.

[sailorboy1]

One of the failed set got an internal short and cooked that series set. 7 years on a set of T105s is excellent! I only ever have gotten 4.

[Dave Lochner]

There is a correct way and an incorrect way to wire 4 6v batteries in series/parralell. When done incorrectly 1 pair of batteries will be used heavily and the other not as much, this can lead to premature failure of one set of the batteries.

The correct wiring has the positive and negative leads coming off separate batteries, such that the current draw must go through all 4 batteries. Somewhere on MarineHowTo.com there is a good diagram.

If you have the Hitachi 80 amp alternator on a Yanmar, it is not a particularly good alternator for keeping the batteries charged. Again on the MarineHowTo.com site there is an article on that issue. Your batteries may not have been as charged as you think they were.

The 30 amp charger is undersized for 400+ amp hour bank. Chargers should be rated at a minimum of 10% of bank capacity plus some extra. A 50 amp charger would be a better choice.

Finally, at 7 years, the batteries were nearing their end of life.

[guyrj33]

At 7 years that's a good life span for the batteries, you've been doing something right.
The best way of wiring series parallel battery sets is based on equal length cable runs from the positive tap to the negative tap.
With the 4 battery setup you have positive and negative connections would be on diagonal corners from each other.

[geoff3nebel]

Good points. I accept that the lead cables were taken from the pair nearest the domestic take off busbar.
Point taken about the 30A charger...
I’ll look at the MarineHowTo.com site for its comments about the Hitachi 80a alternator - I replaced it with a WPS12272N 80A alternator on the recommendation of the Yanmar agent in Les Sables d’Olonne this summer after the Hitachi unit failed. I hope he didn’t sell me a pup - it cost more.

[Pete7]

Originally Posted by Dave Lochner

If you have the Hitachi 80 amp alternator on a Yanmar ........ Finally, at 7 years, the batteries were nearing their end of life.

Yet the wind, solar, shore power and alternator kept those batteries going for 7 years. Sounds he was doing everything right and I wouldn't change anything if the loads haven't changed.

Pete

[GreenWave]

Originally Posted by Pete7

Yet the wind, solar, shore power and alternator kept those batteries going for 7 years. Sounds he was doing everything right and I wouldn't change anything if the loads haven't changed.

Pete

I was with you Pete until OP said he changed the alternator this summer. So what was working for 6.5 years was probably good and then a new variable was introduced.