Decision Time - House Bank Is Toast

Harlen said:

Check out Firefly batteries. Cheaper than the most expensive Lithium and you get 95% of the rated capacity. And they are almost bullet proof and will last longer that AGMs though I don't know how they compare to Lithium.

I've had 5 of them in my trawler for the past three years and love them.

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ranger58sb said:

You mean average load is 48A per hour, yes?

If so, that low voltage shut-down after 168Ah consumption was at about the 3½-hour mark?

If so, and if I understand what you're describing, yes I'd guess batteries are toast -- or maybe one battery, or one cell in one battery (or something like that) is hosed and drawing down the rest of the bank. But maybe a load test would pinpoint some of that better.

Lifeline 8D AGMs (for example) are rated at 255Ah -- so 1530Ah for a bank of 6x. I've read it's not great to parallel more than 4x 12V batteries.

A 6x bank of their 6V L16s, 400Ah each, would give you 1200Ah total. (Or 8x for 1600?) Maybe worth a look?

(Other less expensive brands exist, of course.)

Either route, or some other route, oughta be able to get you through the night without needing to start the genset... even without many reserve issues, I'd think.

-Chris

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markpj23 said:

Had wrongly assumed that since they were LED that draw would be really low. Lesson learned...

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markpj23 said:

I've spent a few hours over the past few days trying to figure out where my power goes. While I'm not shocked at the results, I am surprised at how quickly things add up...

My 48A 'average' discharge rate while anchored out is exactly in line with my findings. Here are the loads I identified:

- 6.5A with all breakers OFF, both inverters ON. (This includes inverter overhead and all the 'sneaker' loads that are not tied to either a 120v or 12v breaker.)
- 9A engine room 12V exhaust blower
- 2A GPS system ON (anchor watch)
- 2A anchor light
- 1A AFT Stairwell LED lights
- 1.4A FWD stairwell LED lights
- 13A galley 120V refrigerator
- 13A engine room LED strip lights
- 5A engine room 120V circ fan
- 5A small refrigerator on FB
- 3A TV / Stereo system
- 2A Salon outlets (phone chargers, etc)

That all adds up to over 66A, take away 13A for the galley fridge cycling and we are right at 48A average draw.

Surprises: I had no idea that my engine room lights draw so much! I have 4 duplex fluorescent fixtures that draw 15A, and the LED strip lights (8) draw 13A by themselves. Guess I'll be going dark while at anchor from now on.

Now that I understand how I can reduce the load, I'm still left with a 1200 Ah house bank that quits after forking out ~165Ah. I guess all that's left is to determine if I have 1 (or more) bad batteries affecting the whole bank.

How do I setup a proper load test to determine if the batteries need replacement? Specifically, what do I use for a load if, as I'm told, the automotive battery testers are not the way to go?

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markpj23 said:

After our 2nd extended time away from the dock since purchase I feel safe in saying that our house bank is toast. There are 6 - 8d batteries less than 4 years old. Hard to believe they have such a short life but I have no clue as to how they have been treated. The right components seem to all be here: Balmar alternator controls, Xantrex inverter/chargers, BlueSeas ACRs and all seems to be functioning.

Assuming 200ah for each 8d, I should have 1200ah @50% discharge = 600ah or pretty close if I've got the math right. My Victron battery monitor showed a whopping 168ah consumed when the inverters shut down for low battery voltage (11.6 volts if I remember correctly).

My load averages 48 amps (measured by the Victron). We run a big residential refrigerator, plus a dorm sized fridge, plus some engine room blowers on 120v. Add to that my 12v loads for nav gear, etc and we are the definition of why trawlers love to travel from one dockside power connection to the next

I could go the cheaper and quick route and just swap out the 8d AGMs. I want to be able to get through the night w/o the generator and new AGMs would probably allow that. Not much reserve though.

Sure is tempting to go the LiFePO route and get at least twice that capacity, although still at nearly twice the cost for the UL listed Kilovaults. Throw in the external BMS, Wakespeed, etc and the cost difference is not trivial. Throw in the ABYC standards evolution and possible insurance issue and the decision gets 'complicated.'

Two questions for the group:
- Am I correct that my current batteries are shot or am I just expecting too much of them?
- Is the current cost & complexity of the LiFePO solution worth the additional capacity? (I know that's subjective....)

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markpj23 said:

.

Now that I understand how I can reduce the load, I'm still left with a 1200 Ah house bank that quits after forking out ~165Ah. I guess all that's left is to determine if I have 1 (or more) bad batteries affecting the whole bank.

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Simi 60 said:

If it helps at all we recently replaced our AGM batts
They were a 220 ah yum cha brand sold by a major victron reseller in Oz

We had 8 of them joined into a 24v bank so 840ah, 420 usable.
We cruise full time, no shore power ever unless out of the water for maintenance

We use between 180 and 200 ah between 6pm and 6am, no Genset usage to support that
If I understand correctly that equates to approx 400ah @ 12v/night

That bank lasted near 6 years before changing.
Noticed them failing 4 months prior, held them together until new LFP cells arrived from China

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catalinajack said:

Simi, your experience with your last set of AGMs is instructive and is a good example of real-world long-term heavy useage of a battery bank. Your AGM lasted 5 years and 8 months before it began to show signs that it was used up. Given that you overnight at anchor virtually every day/night of the year, let's say 350 overnights per year, that equates to about 2,000 cycles. Did I do the math correctly? If so, I'd say you got your money's worth.

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A battery cycle simply refers to one full drain of a battery's charge, from 100 to zero percent. This doesn't have to happen all at once. For example, if your laptop battery drains from 100 percent to 50 percent, then you charge it back up to 100 percent and let it drop to 50 percent again, that counts as one cycle.

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koliver said:

Did your measurement of the draw of your LED ER lighting include the draw of the inverter, with all other loads turned off? I could find only 4' LED that draw 1w per fixture. maybe yours are 8' and draw 2w each? or 8 x 1w + parasitic draw of the Inverter?

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fractalphreak said:

... The Victron will reset itself to 100% charged a long time (in terms of generator run time) before the batteries are actually topped up. There is a set # of amps of charge (that the batteries are accepting from your generator) where the monitor will assume you have reached all the charge that is practical...

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Simi 60 said:

Not sure if that's how cycle life works
Going on the below I would suggest we got probably 1 cycle every 4 days, but I'll be honest I never checked.
That makes it more like 500 cycles.


Saying that, for the $3000 I paid then I was happy enough with that
But now a similar sized AGM bank would cost nearer $7000 and I'd be rather pissed off if I had a repeat performance at that price.

Its why we went lifepo4 - double the usable amp hours for 2/3rd of the price

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