Are My 8D's Dead?

[Juliet 15]

I installed a new smart charger in Nov, then left the boat for 2 weeks with the charger breaker in the OFF position (inadvertently). When I came back my two 8D 12v batteries were dead.

I've been charging them since, but for a week now the charger has yet to go below 13 amps charge (stayed at its max 30 amps for the entire first day).

Am I correct in assuming the charger is trying in vain to charge "un-chargeable" batteries? IOW, is my never-ending charge rate indicative that the batteries are toast?

They were new 3 yrs ago.

 

[BruceK]

Did you leave them with loads connected? If not, and they could not survive 2 weeks of no charging with no loads, they were already toast.
Can you hydrometer test them, are they open cell with screw caps? If so, how was the electrolyte level? Did it need topping up?
Are they still serving loads while you charge them? Might those loads be about 13A, equaling the 13A going in?
I suggest hydrometer or load test them, with no charge and no load. Depending on the answers to questions above, they might well be toast. Or not.

 

[Juliet 15]

Thanks; good points. I haven't checked the fluid levels yet. The only items on there are a hydronic heater (fans and recirc pumps), and a couple priming pumps. I first started thinking I'd killed them when the heater/fans would audibly slow by about 40% if I activated the priming pump (small Facet wobble pump). It seemed like the charger was actually powering things vice the battery.

That's when I looked at the charger and realized it was still charging. It stayed around 14 to 17 amps, eventually reaching 13 amps and stabilizing.

I'll check the electrolyte and make sure it's topped up to where it should be.

 

[DavidM]

If your charger continues to put out 13 amps then that means that you likely have a sulfate buildup on the bottom due to letting them discharge fully. The sulfate buidup is causing the continuing charger current. So your batteries are probably toast.

So now is the time to replace those horribly heavy 8Ds with 4 golf cart batteries. They will fit in the same space and give you as much or more amp hour capacity.

David

 

[Pete Meisinger]

Methinks your batteries are toasted. The modern consensus seems to be to get rid of those heavy back breakers, I agree !

pete

 

[oscar]

Check water level and SG of the electrolyte. If it's close try an equalization. Take the loads OFF when you're resuscitating batteries!

If toast buy a few 300Ah LiFe's.......

 

[BruceK]

Juliet, separate the condition of the batts from the issue of what if anything replaces them. The anti 8D crowd is drifting the discussion.
Check the instructions whether your new charger has the capacity to bring back sick batts which are saveable, some do(or claim to). If it has an "equalize" function try it, top up first if indicated.

 

[Juliet 15]

Thanks all, good input. I went out last night and checked. BruceK was correct, my heater pulls 13 amps. - I checked the spec gravity and all 6 cells were in the red. - The charger is a brand new ProNautics 30 amp smart charger with an equalization function, so I turned everything off and hit that. - I'll run up there today and see what, if anything, that did. - Unfortunately, the other battery on this system is also a 12v wet battery, so I'm not sure I can only replace 1 with an AGM, Lithium, or other battery. The charger can do any type, but I believe they all have to be the same type.- Lastly, these are under-floor batteries; there's no height room for a taller battery. My understanding is that Li-Ion batteries and AGMs are taller...

 

[tiltrider1]

I am curious, are we taking about 2 8D’s as the house bank and there is a separate start battery?

I find two 8D’s to be a small house bank. I also find a 30 amp charger to be a very small house charger. While I’d admit my house bank is larger than average at 1400 amps, I find 800-1000 amp house banks the norm on boats of 50-60 feet. I also find Inverter/chargers that charge at 100 amps to be most common. My back up charger is 40 amps. This I find barely adequate to run house systems while at the dock. In my case my 40 amp charger runs at 60% just to keep up with house loads. That leaves a meager 15 amps left to charge a battery bank.

This may not be relevant to our OP’s situation or there might be a bigger issue here, like over worked and repeatedly deep discharged batteries that could be easily killed in 3 years.

 

[Russell Clifton]

I agree with Tiltrider1. That is a small house bank, less than 500 amps. We have 4 8D for a total of 960 amps with a inverter that has a 100 amp charger. This past week I let the system get down to 11.8 volts and it took many hours of bulk charging at 14.7 volts and 100 amps to get it back to a full charge.

 

[Juliet 15]

So, great questions, of course. I was being brief cuz my real issue was whether I was seeing a dead and unrecoverable battery or not.


I have a Hat 58 LRC, with 2 battery systems - the original 32vdc, and a 2nd 12vdc.


The house has one separate 32vdc bank and another, separate 12vdc bank. The 8D's I'm talking about are NOT house bank batteries.


I have 2 15kw gensets. Each has its own 12vdc 8D battery. Those 2 batteries are charged by this new charger. However, for some reason, the bridge electronics and the hydronic heater are both run off the port genset 12vdc 8D start battery. The new ProNautics charger I installed charges both genset 8D start batteries.


So, while they're not house batteries, they are used for more than just starting gensets. Interestingly, the boat ALSO has a small (3rd) genset, a 4.4kw Entec. It's sole purpose in life is to (you guessed it) recharge the genset and the main engine batteries. Since it uses the same genset 8Ds to start, it has a crank handle that allows it to be manually started.


This things is set up for long trips and has a lot of redundancies.

 

[Juliet 15]

For clarity:
I have one house bank of 32vdc batteries with a Heart 32v inverter/charger.
I have separate house bank of 12vdc batteries with a Magnum 12vdc inverter/charger.
I also have a 3rd, non-house bank of 8D batteries, used to start the 3 generators (2 x 15kw, 1 x 4kw). This third bank also incidentally runs the heater and the bridge electronics. It has its own ProNautics charger. One of these batteries appears to be no good - red specific gravity and can't hold a charge.

 

[tiltrider1]

With the added information I am thinking bad batteries. 30 amp is certainly enough for two 8D start batteries that also run electronics. I’m curious, have you checked fluid level and when you did, had the fluid level dropped enough to expose the lead plates?

 

[BruceK]

Juliet,I`m not a fan of running anything off a genset start batt other than the genset. One function of genset(s) is backup, which I would not compromise. When I bought my boat someone was running a fridge off the genset start batt, I soon changed that.
You must have experienced a genset batt charge issue to add a charger serving just those 2 batts. Apart from other modest solar, I have small regulated solar panel serving just the genset batt. I figured it only got charged when the genset ran, which might not be often enough.
As your batts are taking and giving 13A, after initially drawing the max 30A, are you sure they are cactus? An inexpensive hydrometer will test them for specific gravity which tells you if you have sulfuric acid in solution, or sulfur attached to the plates and water lacking acid. If it`s the latter, some chargers may "equalize" it off the plates back into solution but if not, it`s new batts time.
I`m no electrician or mechanic.I think about things, sometimes don`t get it right, but a lot of it is just commonsense. My modest solar install is DIY but has stood the test of time.

 

[OldDan1943]

It has been my observation, there is always a small draw off the house batteries.
If inverter is on, even in standby, you are drawing from the house batteries. Open the inverter breaker.
Then tack on the 12vt fridge. Empty it, open the fridge/freezer and tape the doors open.
Then, the bilge pumps. W/O a bilge pump counter, you will never know if your bilge pumps cycle when you are away from the boat.
Then the small 12vt compartment fans.
Finally, any lights you leave on, even the LEDs
You could do everything 'right' but there is shade on the solar panels ...

 

[ranger58sb]

My understanding is that Li-Ion batteries and AGMs are taller...

Can't speak to LFPs, but that's not necessarily the case with AGMs. An 8D, or Group 31 or whatever AGM will conform colsely to BCIGroup sizes.

The house has one separate 32vdc bank and another, separate 12vdc bank. The 8D's I'm talking about are NOT house bank batteries.

I have 2 15kw gensets. Each has its own 12vdc 8D battery. Those 2 batteries are charged by this new charger.

So, while they're not house batteries, they are used for more than just starting gensets. Interestingly, the boat ALSO has a small (3rd) genset, a 4.4kw Entec. It's sole purpose in life is to (you guessed it) recharge the genset and the main engine batteries. Since it uses the same genset 8Ds to start, it has a crank handle that allows it to be manually started.

It shouldn't take an 8D to start a 15 kW genset. I'd imagine a single Group 31 with decent CCAs/MCAs would start one... of if necessary, a pair would do it. If you look at CCA/MCA specs on both battery and genset engine, you can work that out. (I would guess a single Odyssey 31M-PC2150 AGMs would work, given they trot out higher cranking amps than many (most?) other brands of G31s.)

-Chris

 

[Russell Clifton]

When checking a bank of batteries with a hydrometer, is it best practice to disconnect the batteries from each other, or can they be left together? Thanks

 

[Bob Cofer]

When checking a bank of batteries with a hydrometer, is it best practice to disconnect the batteries from each other, or can they be left together? Thanks

They can be left connected.

 

[ctjstr]

One way to be sure is to use a carbon pile style load tester. You can get a pretty cheap one from habor freight.
Not that its the only way to do it, but I typically charge each battery fully and test them separately Disconnect them if you want, and just put a charger on them. Battery should charge up over 12v a few minutes after disconnecting the charger. if it shows good voltage, put the tester on it. They artificially load the battery and you'll know by the readout on the tester whether its any good. Sometimes they just drop way down. You know the battery is toast. Sometimes they drop down to about 9-10 volts under load, which isn't great, but you can work with it.
Just a hint or two. if you haven't used the tester in a while, it will steam for a bit, which can be startling if you aren't expecting it. Also, don't leave them on for more than a few seconds.

 

[Rthomas]

It could also be that the charger is defective. Test on a known good battery. I had 8ds and replaced them with golf cart batteries. Not enough cranking amps for my liking. Replaced those with two sets of 2 group 31 wired parallel. 205 AH each set compared with 225 on each 8D. Losing 10% capacity not a big deal because I have a generator. The two batteries together are slightly smaller than 1 8D. Each is less than 1/2 the weight. I buy the lead acid ones for $100 each. That is important because batteries lose capacity with age, cycles, and temp. At 4 years they will have 40 to 60% of original capacity.. I routinely change them out at the 4 year mark.

 

[Scottwb96]

I see you're in the same area (sort-of) I am in Seattle. I just switched out 8 6V Crown Deep Cycles CR-235 (lead acid) in favor of a bank of AGM's. They were always maintained on a Magnum charger. I am selling them cheap if you're interested. DEFINITELY a lot easier to move around then the 8D's...

 

[oscar]

It has been my observation, there is always a small draw off the house batteries.
If inverter is on, even in standby, you are drawing from the house batteries.

Actually, on my Moho with the Magnum 3000W inverter with remote you're talking 2-3A

 

[BruceK]

It could also be that the charger is defective. Test on a known good battery. I had 8ds and replaced them with golf cart...

Maybe read post 1. The new charger was accidentally left turned off for 2/52. Turned on, it churned out amps.

 

[Xsbank]

Golf carts aren’t supposed to crank anything.

4 years? That’s pretty poor even for fla. Your battery place sends you birthday and Christmas cards, I bet.

The answer to the original question is ‘yes.’

 

[Harlen]

If you have to replace the batteries, check out the Firefly battery. It is a new design that is mostly immune to deep charging. You can also use 90% of their rated capacity. I have them on my boat and like them very much. They cost more but last longer.

Firefly International Energy