Changing Batteries

Seeking advice for a project or do you want to share the outcome of one? Various technical tips and questions.
Post Reply
User avatar
Joined:Tue Feb 26, 2013 2:28 pm
Location:Italy, Rome
Changing Batteries

Post by source » Fri Apr 12, 2013 10:57 am

In the last period the engine battery of my Dufour 34 seemed to work not so good. It is the original one (a Varta Hobby 60 AH) and it is six years old, so it seems it's time is arrived :D

Last wednesday I changed it with a new Exide Premium 74 AH that should work fine for the engine.


Next step (I think maximum next year) will be to replace the 2 service batteries (both original too). In this case I would like to try two AGM instead of the classical ones, but I have read that the single engine alternator could give problem when charging different technologies of batteries.

What's your opinion? Is it true and so it is better to buy other batteries of the same kind (in this case I will buy other two Exide Premium 74 AH) that are less expensive but (it seems) less performing that AGM ones?
No man is an island

Joined:Wed Jan 12, 2011 12:17 am
Location:Finland, Parainen, archipelago

Post by Mikko » Fri Apr 12, 2013 10:18 pm

We have replace all 4 battery's with AGM, 4th is extra domestic bank.
Old ones, same as your's, had vapour acid liquid during charge to inside of battery compartment box. That was messy to clean... Batterybelts had started to melt and need to replace all
As we love to stay natural harbours, these new AGM gave us many days more to stay isolate of sivilisation.

We also mounted, batterymonitor BEP
Now we don't have anymore stress of guessing battery charge level :D

In shorepower charger you need to change settings if you have liquid acid, AGM or GEL.
There is own different setting for those types.
325 GL # 49 - Aurélia
Sailing, the most expensive way to travel for free of charge

Joined:Mon Jan 14, 2008 11:19 am
Location:Sweden, Soedertaelje

New Batteries

Post by Lars » Sat Sep 05, 2015 3:19 pm

Exide EP650 dual AGM fits in D34. Same size as original
I replaced my old to EP650.
Has been built for 650WH over 20 hours and also to bes used for Charge start or anchor lift
AGM for only start current is not designed for continous low current use
Learned that max load Voltage is 14,4V---not to go higher with AGM--no boost above that.
Floating 13,8V
Solarcell regulator changed to Mastervolt SCM20

I use 2 solar cells 60 + 65W and for back up a fuel cell--for rain days when solar cells produce less

My D34 battery charger Cristec--is now set to no boast and at led antimon---to not over voltage the AGM.

The Engine generator has 60A capacity and sensor cable 14,2V approx
My Dufour 34 is no 42 from 2003--the first one in Sweden
Last edited by Lars on Sun Sep 06, 2015 10:11 am, edited 5 times in total.

Joined:Mon Mar 10, 2008 4:47 am
Location:USA, WA, Seattle

Post by TimOnders » Sat Sep 05, 2015 7:14 pm

The D34 uses Group 34M sized batteries (not sure what the European equivalent size code is). When ours was built in 2003, they were using Hoppecke AGM batteries (standard in BMW & Mercedes at the time). I'm surprised they moved to flooded cell.

AGMs are definitely a plus, but you may need to upgrade your charging systems. If you have an earlier D34 (prior to the introduction of the Volvo D1-series engines), the alternator is kind of small for an AGM bank. It's also worthwhile to invest in a charge controller, like the Sterling products, to properly charge the batteries. Batteries are expensive, and proper care can help them last much longer.

We've expanded the capacity in our D34 quite a bit. We've added two more batteries to the original three for a 350Ah house bank, and added one more for the engine battery. They are all Odyssey AGMs since I used to be able to get a good price on those.

Switching to some of the newer AGM technologies does require some safety considerations though. Along with higher charge acceptance rates (they charge faster if you can supply the current), they also have higher peak discharge current. So, fuses need to have sufficient disconnect capacity to properly protect the wiring. The main fuse style used in our D34 has a 100kA interrupt rating (IR), so that's not a problem. We did add a high IR fuse between the two parts of the house bank as well.

User avatar
Joined:Sat Sep 05, 2009 11:08 pm
Location:Spain, Barcelona

Post by Pauli » Sat Dec 26, 2015 11:12 pm

TimOnders wrote: We've expanded the capacity in our D34 quite a bit. We've added two more batteries to the original three for a 350Ah house bank, and added one more for the engine battery. They are all Odyssey AGMs since I used to be able to get a good price on those.
Hi, Tim...

Your post is very interesting. But I'd like to know where you have placed the new batteries, because in the place where are fitted the standard ones, there isn't room to put a pair of batteries more


angus spence
Joined:Sun Nov 11, 2012 8:05 pm
Location:Scotland, Glasgow

D34 extra batteries

Post by angus spence » Sun Dec 27, 2015 8:18 pm

I have fitted extra batteries in my 2 cabin D34P. Is yours the 2 or 3 cabin version. I fitted them in the deep cockpit locker up against the central bulkhead (well secured in individual battery boxes). This is very close to the existing batteries, so not long cable runs which is good.

I fitted 2 extra, so now have 4 x 75Ah for house and one for engine start. This capacity is very useful when doing a long day sail then anchoring overnight, so no shore power. It seems a lot of Ah but I do not like to discharge more than 50%, to preserve battery life.

I am sure Tim will let us know what he did soon.



Re: D34 extra batteries

Post by jcjglt » Sun Dec 27, 2015 9:57 pm

On board my 375GL the two 100AH maintenance free original batteries died after only two years of use. I replaced them by two 150AH-C10 (165AH-C20) gel batteries stored in the same place but turned by 90 degrees. The 100AH batteries length was parallel to the length of the boat. Now the 150AH length is parallel to the boat width.
Why did I replace them by two only paralleled batteries ? With paralleled batteries, when one of them is dying you have to replace all of them at the same time even if they still look good, if you don't do it the weakest one will quickly deteriorate the other batteries and a new one will soon become bad. With four paralleled batteries you double the risk to have to change all batteries compared to a situation with only two batteries.
I think two paralleled batteries is the best situation, you just need to put the biggest size possible.

Joined:Mon Mar 10, 2008 4:47 am
Location:USA, WA, Seattle

Post by TimOnders » Sun Dec 27, 2015 10:37 pm

Our D34 is the two-cabin layout with the large lazarette on the starboard side (we call it "the hold"). We built a battery box in the forward port side of that space (against the midships bulkhead) which contains three batteries in addition to the original three.

The engine start battery is in the forwardmost position of the new battery box, and the associated wiring runs through the forward bulkhead into the engine space.

The other two batteries in the new box connect using through-bulkhead terminals to join the original three batteries to make a five-cell house bank. There is extra fusing in the connecting wiring given the capacity of the two extra cells (modern batteries have very high short-circuit currents, and can be very dangerous).

I need to make a couple additional changes to the wiring to balance the house bank better, but it has worked pretty well so far. We now have house bank capacity to run heat, refrigeration, nav lights and navigation equipment for more than 24 hours without charging.

The added weight does sit the stern a little lower, but it doesn't seem to significantly impact her sailing characteristics. The balance remains quite excellent. She does sail better on port tack than starboard, but I think she did that even before adding the extra weight. We've never figured out why.



Post by jcjglt » Mon Dec 28, 2015 12:59 am

I recommend this web page about the interconnection of multiple batteries :

Joined:Mon Jan 28, 2019 12:57 pm

Re: Changing Batteries

Post by LarsCidh » Sat Oct 05, 2019 4:06 pm

Today startbatteri ep650 dual agn
Usher battery ev1600 litium 125ah
Mastervolt solarcell charge set Both for AGM
Landcharger Quick 3 Time 25A set for agm
Batteriet excide-tudor

Post Reply