Two Victron AGM 110 Ah (BAT412101085) batteries correctly connected in parallel, a Victron 25 amp “Blue” charger (BPC2405310640R) and a Sunwind 10 amp solar smart charger.
The boat season in Sweden is short and not hot and I’ve only used the batteries for three (two month seasons).
Without going into details yet, if we assume because of my adequate knowledge, that I haven’t shortened the battery life through misuse, I now (4Th season) don’t get more than 30ah before the voltage drops to 12.0 volts with a 0.025C (5.5a) average load and then recovers to a 12.5 OCV. Being realistic I believe I should get at least get twice that or more. I also find it interesting that the voltage drops so much considering such a light load
Should I be disappointed with the present performance of these batteries?
You have to keep them charged when not in use, loss of capacity occurs by sulphation if they are not kept fully charged. I ran Victron AGMs for 4 years without issue but when the boat wss out of use they were kept full.
Greetings from Sweden. Partly cloudy and a nice wind for sailing. Thank you for the answers. Here’s my short list.
The batteries are 3.5 calendar years old and I checked the voltage when I bought them. 12.85 volts
Always charged when not in use every 2-3 months. The batteries basically go to float directly. (I leave them in sub freezing temperatures on the boat but always try to charge when above freezing. But that shouldn’t be a problem..??..)
Never run under 12.5 (with a load) generally the solar charger handles the daytime requirements. But doesn’t overcharge the battery. See below. (When away from the boat I position the solar cell so there’s only 2-3 hours of sun on it per day. It’s always on float when I arrive)
Never overcharged. I’m vigilant that the solar and Victron charger go to float within a reasonable time. I’ve had experiences of battery chargers being fooled when having a load running while charging and consequentely staying in absorption state.
Never in a hot state. I have a Bluetooth temp logger taped to the sides of the batteries.
Basically the quick drain and the big difference in OCV versus load voltage at 0.25C "basically idling " seems point to sulfation. Hard to understand when they’re supposed to last 7-10 years
Have I missed anything? I figure if other people have problems with AGM as one of you stated, maybe it’s better to just buy cheaper standard cell batteries and change them every year or so, skip all the fretting, and enjoy being on the water instead . (I’ve enjoyed the learning process, but this result wasn’t worth the hassle.)
I think I treat these batteries better than I treat my pets, and believe me, they’re spoiled
Have you loaded tested the batteries individually? Maybe one is bad, and the other is good, so one is doing all the work.
My experience with other AGM is good - about 8 to 10 years, and they get charged constantly, even in -20C to -30C weather, with correct temperature compensation from the charger. The battery won’t freeze at those temperatures as long as it is at least 50% charged (depends on the battery). I use a small battery maintainer that gives them 250mA - 1A as needed when they are in storage.
I’m planning on checking the batteries individually after this season. I suppose I could do it it now on the boat. Not that hard. Just a lot of bending over haha. Boat life is great, huh? Seems odd though that one should fail. I bought them at the same tine. Victron is supposed to have good products.
The conditions to reach this are very specific. Float service is one of them, and temperatures.
I do know some AGMs and flooded battery banks that have reached 8 but they were literally babied and had a detailed maintenance routine.
Agreed. One could be a little bit higher voltage and doing all the work. It could also be cabling or oxidation/corrosion at the battery terminals. Do you have the loads/charging cables diagonal for optimal current? e.g. take off power at Battery 1+, Battery 2-
I have diagonally cabled and babied them. I’ll try separating and charging each one individually. Is it a good idea to periodically swap the outgoing diagonal cables so bat1 and bat2 swap poles? I’ll try separating and charging each one individually. Can they get unbalanced? I figured even if one happened to somehow get a slightly higher charge it should even out under load. Or not?
No oxidation at poles. And I checked the voltage at the poles as well and it is the same as further along the line so there’s no loss at the pole connections.
With 2 usually it’s even.
But making sure they are propey charge is important.
That they are charged immediately after being discharged.
Being charged the right amount, not too short and not too long. Making sure they reach the target voltage for the tyoe of service they are in (cycling in your case)
I prefer flooded lead acid over AGMs. But with lithiums now i will not go back to them, as you say too kuch work and fussing. Agms often dry out and sensitive to being warm. But also sulphate. 2.5 to 3.5 years is the normal life span i have seen from AGMs with most people.
Lead acid batteries are very unforgiving.
One last notation. I didn’t mention this before but maybe it’s important. When the voltage reaches @12.5v with @ 4 amp load the voltage drops from 12.5v to 11.5v. within 30 minutes. If I disconnect it goes up to @12.6. When I charge I can only put in @ 40 amps total. The battery bank as I said earlier is 2x110ah. Does sulfation behave that way.
Ok. Thanks for all the info everyone. I feel I’ve done everything correctly. Left to do is a controlled bench test after the sailing season is over and then choose which manufacturer to choose besides Victron when im forced to buy new batteries years earlier than expected. Victron claims 700 charge cycle if not charged below 50%. I got less than 50. Planning on returning some other products of theirs that I just bought.
. (I’ve enjoyed the learning process, but this result wasn’t worth the hassle.)