6V Golf Cart Bank. How big can I go?

[CptMorgan]

I have a lucky situation. I have some extra area around the house bank, and I could use some extra weight on that side of the boat.

Boat has 12 x GC2 (6V -235 ah golf carts) = 3 banks of 24v. All batteries are due for replacement.

Anyone running 16 x GC2s (4 banks of 24v)?

I know of a large Tolly with this same setup, and they seem happy. The extra reserve capacity would be nice. I'm committed to the GC2 footprint and height.

Thanks,
-Morgan

 

[rslifkin]

I don't see why you couldn't go with 16 of them. If you could manage to get more height, there are also a couple of taller (and higher capacity) batteries of the same footprint.

 

[HTurner]

Your only limitations are space and weight. Of course you have to consider the abilities of your charger.

 

[CptMorgan]

Great. Got lots of space, weight and charging. Not much spare height though for taller L16 or similar.

 

[rslifkin]

Great. Got lots of space, weight and charging. Not much spare height though for taller L16 or similar.

L16s are a good bit taller, but depending on how much height you've got, there's an intermediate height (can't remember the designation for it). It's not quite as common, but they're available. Usually in the 340ah range (compared to 400+ for L16s).

 

[luna]

I'm in Van. and am about your size.

I run 2 house/inverter banks, all 6V. GC2's

One, 12 Batts. @ 12V. for Refers, Audio/visual, and a few wall receptacles.

The other, 8 Batts. @ 24V for Espar. water pump, Micro. and most wall receptacles.

Total 20 GC2s.

This seems to work well on the South Coast of BC.

 

[Bacchus]

FYI - large banks require consideration of AIC fusing that is different than just normal A overloading. Are you protected with the proper fusing?

https://marinehowto.com/battery-banks-over-current-protection/

 

[CptMorgan]

Good info Don. I have ANL fuses on the banks now. I'm going to simply to MRB fuses on the posts.

 

[luna]

Rather than add to the battery posts 4 MRBFs, an acceptable solution is to simply install sheathing (an approved plastic loom) over the Positive parallel conductors from the Battery to the Battery Bus, provided that they are less than 72" long. While you are at it, I would do the inter Battery Series conductors as well.

Either way, MBRFs or sheathing, circuit protection is still required for the positive conductors that connect the Battery Bus to the loads. MBRF's could prove useful there.

 

[Bacchus]

I believe only acceptable AIC protection for large bank is Cl T fuse. MRBF acceptable but only available in lower A ratings.
See the AIC section of the linked CMS article on large batty bank fusing

 

[tiltrider1]

I believe only acceptable AIC protection for large bank is Cl T fuse. MRBF acceptable but only available in lower A ratings.
See the AIC section of the linked CMS article on large batty bank fusing

This is very key. As you make the bank bigger you increase the amount of energy that could be released instantly. You must also keep up with the correct safety equipment to prevent a possible disaster.

I run 8 x L-16 batteries, that is 1600 amps at 12 volts. A bank of this size requires me to have a 150a charger with only 1% voltage drop. That’s some big wire. Wire that size can carry a lot of energy. Enough energy that it could literally weld its self across a fuse and destroy the boat. To prevent this you need to use the correct fuse and fuse holder. Using a smaller incorrect fuse sounds safer but in fact could be deadly.

Using smaller wire might prevent you from being able to change your bank to capacity.

No problem going big, just don’t take any short cuts.

 

[DDW]

Increasing the AH capacity of the bank doesn't necessarily require larger fuses. They are sized to the servicing wire. If it doesn't change, then the fuses needn't either. In fact it may be distinctly incorrect to upsize the batteries and fuses, leaving the wire the same.

 

[Bacchus]

Increasing the AH capacity of the bank doesn't necessarily require larger fuses. They are sized to the servicing wire. If it doesn't change, then the fuses needn't either. In fact it may be distinctly incorrect to upsize the batteries and fuses, leaving the wire the same.

Its nit that you need a larger fuse just the correct type (T) that csn handle a dead short. Others will weld themselves as others mentioned and defeat the purpose of a fuse. Exsctly the.opposite of what some.might expect. The wrong type doesnt protect is some cases.

 

[tiltrider1]

Its nit that you need a larger fuse just the correct type (T) that csn handle a dead short. Others will weld themselves as others mentioned and defeat the purpose of a fuse. Exsctly the.opposite of what some.might expect. The wrong type doesnt protect is some cases.

This is very important. Thinking that you have solved the problem by using a 100 amp fuse could in-fact be what actually causes your boat to catch on fire. With these big banks you have enough energy to instantly weld a connection right across the fuse. At that point there is nothing to stop the batteries from unloading all their energy which wouLd most likely end up in a fire.

T fusses have a destruction rating usually arouNd 200,000 amps. This is why they are required on bigger battery banks.

Do not confuse destruction rating with amp rating. My bank runs a fuse that has a 200,000 amp destruction rating but is rated to blow at 250 amps.

 

[ranger58sb]

I have a lucky situation. I have some extra area around the house bank, and I could use some extra weight on that side of the boat.

Boat has 12 x GC2 (6V -235 ah golf carts) = 3 banks of 24v. All batteries are due for replacement.

Anyone running 16 x GC2s (4 banks of 24v)?

I think the word BANKS might be worth some study, here.

You say "the house bank" and then describe three separate banks, functions not described.

If one of your three banks is for house functions, it might be that increasing that bank size -- versus adding another bank -- is what could get you what you're after.

That'd leave you with two banks of 4x for unknown functions, and one bank of 8x for house.

???

-Chris

 

[luna]

I agree with tiltrider1 that this is very important. But thats about as far as my agreement goes.

The Blue Seas, Marinco or whoever's Class T fuse installed on your boat is more than likely built by Littlefuse and if so it will be stamped with their product number, JLLN xxxA-P.

These fuses do not have any "destruction rating" although if they did, one would expect that this rating would be the rating at which the fuse blows, thereby being destroyed and only fit for the recycling bin.

What they do have, in Littlefuse speak is an Amperage Interruption Rating (AIR) which ABYC calls an Amperage Interrupt Capacity (AIC).
This AIR indicates the amount of current that will not jump the gap created in the fuse element when the fuse blows at it rated time and current capacity (eg. 250 A).

It is true that these JNNL fuses possess an AIR of 200,000 Amps, but that condition cannot occur on your boat as this rating is for 300V of AC current. Were are you going to get that from?

Their AIR for DC current is 20,000 amps @ for all intents and purposes 125V. At 29V or less the AIR is likely double, but as the low voltage market is not big enough Littlefuse has not published any useful low voltage rating.

I also agree with Bacchus in that the marinehowto article referenced would make a good study as it gets complicated with large banks and distribution networks.

Finally, to answer Bacchus question, yes the supply conductors from all of my battery banks (save the 4 starts) are protected by appropriately sized JLLN fuses. One for each of 3 inverter/chargers, 2 for the alternators and one at the thruster. All other branch circuits are suitable protected with CBs or fuses.

 

[CharlieJ]

Ampere Interrupt Capacity (AIC) is an important, much misunderstood and oftentimes neglected variable in selecting an overcurrent protection device; i.e., a fuse or circuit breaker. In battery systems it is important to know the available short circuit current (ASCC) that a battery can produce and then match the OCPD to be able to survive an ASCC event.

The ABYC is very clear on how to specify the AIC of OCPDs depending on the battery or battery bank ASCC. If the battery manufacture does not provide an ASCC than the main OCPD must have an AIC of at least 20kADC at a minimum of 125VDC. In other words a Class T fuse. Note that there are circuit breakers available with an AIC of 50kADC.

Here are some representative AIC values for Lifeline Batteries, provided by their Tech Support:
GPL 31XT: 3,386A
GPL 4DL: 5,800A
GPL 8DL: 6,935A

So a bank of 4 x GPL31XT in parallel would have an ASCC of 13,544A.

 

[Ka_sea_ta]

There is a second consideration with large capacity battery banks, that is your charging source. I was talking to the alternator repair guy after having to have my Balmar 220 amp alternator rebuilt. He said that he has to be repair these alternators that charge large capacity banks because they aren't designed to continuously operate at max charge output. They over heat and burn the windings, bearings and diodes are all subject to damage. So if you do not have a thermal limiting feedback on your regulator you risk destroying your alternator from long periods of high current output. I do have a smart regulator with a thermistor on the alternator but during a long constant current stage of charging the alt still gets hot. Just something else to think about.

 

[DDW]

I'd assume if using MRBF fuses you'd have one on each bank - otherwise why use them at all? These have an interrupt rating that exceeding what is required of four 4DL in series. Class T fuse is overkill, not that that is a bad thing.

 

[CharlieJ]

These have an interrupt rating that exceeding what is required of four 4DL in series.

48VDC systems are pretty rare right now in the marine market. That said an MRBF on the last battery in the 48VDC string with 10kA AIC would certainly meet the requirement.

 

[luna]

Charlie.

From what I read, @ 58V DC (max.allowable) the AIC of an MRBF is 2kA, not 10. At 32V the AIC is 5kA. Neither rating exceeds the ASCC of a string of more that 2 - 4DL's, based on your 5.8kA noted above.

 

[CharlieJ]

@luna #21: My mistake. You are correct; the MRBF would not be adequate as the only fuse in a string of 4 x GPL 4DL batteries in series. The only available option would be a Class T.

 

[jungpeter]

Hi CaptMorgan,

Not to gang up on you, but one more item worth consideration (correct interconnection of multiple batteries) in your endeavor is discussed in this URL: SmartGauge Electronics - Interconnecting multiple batteries to form one larger bank

Regards,

Pete

 

[Simi 60]

Our batteries can produce huge amounts of amps

Nothing on our boat could pull 300 amps, even several things combined wouldn't pull 300 amps so see no reason to have fuses bigger than max load.

The whole idea of a fuse is to have that fail before other things melt.
It's a fuse, a weakest link.

Our 3 X 24v @ 280ah batteries have a 200amp mrbf on each

 

[Bacchus]

Our batteries can produce huge amounts of amps

Nothing on our boat could pull 300 amps, even several things combined wouldn't pull 300 amps so see no reason to have fuses bigger than max load.

The whole idea of a fuse is to have that fail before other things melt.
It's a fuse, a weakest link.

Our 3 X 24v @ 280ah batteries have a 200amp mrbf on each

Simi
Do you know what the short curcuit A rating is for those battys?

Even a modest 100AH batty can have a short circuit rating of 5000A.

 

[Simi 60]

Simi
Do you know what the short curcuit A rating is for those battys?

Even a modest 100AH batty can have a short circuit rating of 5000A.

For sure, but how does it get out if a low rated fuse, or in our case, 200amp mrbf to 500amp ANL to 500amp breaker blows?

I certainly don't want something bad going on and having a monster high amperage fuse there allowing the bad to escalate.

To me that seems a bit like putting a bolt in a fuse holder

 

[bluebyu]

You may consider interstate batteries. Their"T105's" are made by Trojan.

 

[CharlieJ]

If there is more energy in the battery than the OCPD is rated for, in a dead short, the fuse will blow and may completely blow apart. Or the plasma that forms when the fuse blows may not extinguish fast enough to prevent additonal damage. In the case of a circuit breaker under the same scenario, the arc suppression system may not be able to mitigate the arc that forms and the contacts could weld together. That is why AIC is so important especially with high energy batteries like AGM and LFP.

 

[DDW]

Charlie.

From what I read, @ 58V DC (max.allowable) the AIC of an MRBF is 2kA, not 10. At 32V the AIC is 5kA. Neither rating exceeds the ASCC of a string of more that 2 - 4DL's, based on your 5.8kA noted above.

But at 12V, 10,000A. 24V is not 32V. In a narrow range, AIC is about linear with voltage. Also, a short circuited 4CT isn't anywhere near 6 volts (1.79 mOhm resistance), so closer to zero. At 2000A draw you'll be at 14V for four according to Lifeline specs, and there will be substantial additional drop in the wires. The MRBF will have no problem interrupting that.

A 4S string of 4CT produce no more current than a single one, 3621A at short according to Lifeline. This is within the MRBF spec at 32V, well within it at 24V, and very well within it in any conceivable short scenario.

 

[Bacchus]

For sure, but how does it get out if a low rated fuse, or in our case, 200amp mrbf to 500amp ANL to 500amp breaker blows?



I certainly don't want something bad going on and having a monster high amperage fuse there allowing the bad to escalate.



To me that seems a bit like putting a bolt in a fuse holder

I'm no expert here but have been reading & trying to understand AIC / AIR.
The important point I have gathered is that very high amp flows... as in short circuits not just a high A use system.... cause many fuses to weld themselves together rather than simply open due to overload.
The larger the size of a batty bank the higher the AIC / AIR needs to be regardless of the fuse rating for a simple overload. They are two different and somewhat unrelated conditions.
I dont know if I'm correct but I think of the fuse as analogous to a switch...
Under " normal" conditions ( within the rated A capacity of the Sw) you can open the Sw and the circuit is protected. If the current flow is higher than the rating for the Sw there is a risk the Hi Amps will arc and weld the contacts together instead of openning the circuit.
The risk protected by the AIC rating of a fuse has nothing to do with simple overload protection rating and everything to do with dead short conditions (when normal overload protection of the wrong fuse type is no longer effective and fails as a shorted fuse vs an open circuit)

My understanding us a 100 A NRBF fuse will fail/open under a load of say 150A but if a batty bank is shorted and 20,000 A present the fuse may weld shut instead of opening and protecting the circuit. Likely a rare occurrence but that's my understanding of the whole topic / area if ABYC dealing with AIC. A type T fuse will still open and protect in the extreme cases where even NRBF exceed their ratings.

BTW I do not disagree with your use of MRBFs at each batty vs trying to protect a combined multi parallel bank. In fact, im thinking of using a similar approach w 4 GP3as in parallel. In that case V as long as each batty short circuit current is below thev10,000A AIR of the MRBFs they b should be protected.