AGM batteries

[Impavidus]

Just returned from 3 weeks cruising the south west cost of UK. We have 3x95 amp hr AGM domestic batteries wired in parallel. Originally Fed from one end off the bank. The battery life in the last 6 months has deteriorated. We changed the feed cables so the negative is fed from one end of the bank and the positive from the other as suggested and posted in other posts in this forum.

However, while away we found the battery life after extended sailing during the day was very poor.

After some investigation, we found the first battery in the bank of 3 was not holding its charge. We swapped it with the bow thruster battery which is less important and less used to improve our domestic capacity. This worked fine but the now bow thruster battery needs replacing after just 17 months now we are back.

The Excide AGM 920 has failed. The retail price of this battery is £200+. I will be getting a replacement, either writing to Excide, calling Clipper marine, or going to eBay. The warranty is two years on Excide but I hear they are very reluctant to replace. They tend to pay you for the united used period???

I just wondered if anyone else has problems with AGM Batteries failing prematurely? Are they really worth the extra cost? We have have always got 5-6 years out of good quality lead acid batteries. I can get  a replacement AGM for less than £100 on  eBay. Is this just bad luck or are Glass Matt not all they are cracked up to be?

The other 4 AGM batteries on the boat which are AGM seem to be ok

Your thoughts?


We have a NASA BM2 battery monitor and we keep an eye on battery power.


Ant.

[blue-max]

I had AGM batteries on my last boat - amazing they were still good after 12 years and recovered their charge from 9 volts. Tried to  get agm for current boat in Turkey but very difficult to  find. Were offered excide EP1500  but turned out these were 18 months old so  declined offer. Same story  with Bosch - 15 months old so  no choice but to  go  for standard service batteries

[tiger79]

I reckon reasonable quality AGM batteries are worth having.  They accept charge more readily than regular flooded batteries, don't leak, and are fairly long-lived.

[Impavidus]

Hi peeps
We have got to the bottom of the problem. One battery is not holding its charge.

It was the first battery in the bank. We have removed it and added two 100ah AGM's to the 2x Exide EK092's in the bank (in addition to feeding the power/discharge cables from opposite ends of the bank) giving us just under 400ah of domestic on the bank. Well within our projected 24 hour consumption at less than 50% discharge. Which the original back should have given us, there is now 40% OVER CAPACITY!!   

The new NASA BM2 battery monitor and 200amp shunt gives us a good system to monitor the batteries.

We have now also added a "Battery Extra":
http://www.ebay.co.uk/itm/252120721226?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
and two 100 watt Monocrystalline solar panels:
http://www.ebay.co.uk/itm/282081265472?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
With a charge regulator.


Meanwhile last weekend in overcast conditions the panels were producing 4-6 ah. In bright sunlight they were producing 10-11 ah.

Cost was C.£220.00 UKS  + £129.00 for the BM2 which we fitted some months ago.

Clipper marine said they have not had any issues with the AGM's fitted to other new 37 cruisers when I contacted them........... So perhaps we were just unlucky? We have written to Excide asking them to replace the defective battery under the 3 year warrantee............ Lets see what they say?

One thing is for sure, when building a domestic battery bank you really do need to look at how the system is fed and charged. Just wiring the batteries in parallel as Bavaria do on their new boats will not give you the best performance. (see other posts on this forum)


Disappointingly having paid extra for additional battery power in the form of AGM's and expecting to be able to have a night on the hook without turning the fridge off, running the engine for an hour or so, or being able to sail for 8-10 hours with the nav gear on without having to run the engine... We have had to add extra power, kit, and do a lot of research to get Impavidus up to our expectations.

I am planning to do an article on domestic battery power, Solar power, chargers, batteries, Auto Pulse Battery Desulfator's and battery monitors.

Hopefully I can pass on some good tips to the forum...........Watch this space. 

Ant.

[tiger79]

One thing is for sure, when building a domestic battery bank you really do need to look at how the system is fed and charged. Just wiring the batteries in parallel as Bavaria do on their new boats will not give you the best performance. (see other posts on this forum)

For 3 batteries, Bavaria's parallel wiring is fine.  We're talking about very small voltage differences due to terminal connections - these voltage differences are infinitesimal.  If you have a bank of 6/8/10 batteries, it maybe makes sense to take the main positive and negatives from opposite ends of the bank, but the actual benefit is incredibly small.  It's one of those things which someone proposes and then it suddenly becomes folk lore as the thing to do.

[Impavidus]

Humm. I still cannot get the logic of why the first battery in the bank is not holding a charge and the others are ok...? I have had it at home for a week and I have charged and discharged it down to 11.5v the recharge cycle has had the "battery extra" switched on to de-sulphur the battery. After 10 cycles its still not able to give 4.3AH for more than an hour before dropping to 11.5 v
I guess its just faulty? Bad QA? It will make a good gate stop though

Ant.

[tiger79]

Humm. I still cannot get the logic of why the first battery in the bank is not holding a charge and the others are ok...? I have had it at home for a week and I have charged and discharged it down to 11.5v the recharge cycle has had the "battery extra" switched on to de-sulphur the battery. After 10 cycles its still not able to give 4.3AH for more than an hour before dropping to 11.5 v
I guess its just faulty? Bad QA? It will make a good gate stop though

Ant.

It's probably worth a tenner at a scrap metal place.