New Battery Bank (is this wired correctly?)

[epiic]

I purchased 7 Firefly Oasis (carbon foam) batteries for my house bank. This is 770AH Total @ 12V.

Can anyone confirm that I wired these correctly in parallel before it goes live?

I have the 7th battery in the other aft cabin. That is where these leads are coming from at the back.

[epiic]

Also, should I put "tef gel" anti-seize on the bolt threads or leave it alone?

[redsky49]

The six batteries shown are wired properly for parallel operation.

I would check if cable chafe would be a problem in a couple locations.

Tef-Gel wouldn't hurt, but should only be applied to the male threads - top 1/4" - to avoid getting on contact surfaces.

You may have unbalanced charging/discharge, particularly with the seventh battery. Think this through. I would have stopped at six battteries.

Wood is not a good surface material for batteries.

Provide adequate ventilation (may not be required for Firefly - don't know).

Secure batteries.

Install remaining cabling/instrumentation.

[epiic]

I never thought it mattered that I had a odd number of batteries since the system does not know how many batteries I have since they are wired up in parallel.

Not sure why wood is a problem. What would you recommend that I line the box with?

[epiic]

I did some searching on Google and was not able to find anything regarding odd numbered battery banks wired in parallel.

[did-g]

Originally Posted by epiic

I did some searching on Google and was not able to find anything regarding odd numbered battery banks wired in parallel.

It's not the number of batteries, it's the wires length between your main bank and the 7th battery, wires haven't a zero resistance and one bank is going to empty in the other, I would measure the voltage at the main bank then at the 7th battery terminals and double check with firefly if it's ok.

Moreover it's look like your wiring between the main and the 7th battery is going to be wrong the + and the - shouldn't go from the 7th to the panel. One wire should come from the main bank and the other from the 7th like you did with the main bank.

You have a nice pack with a lot of power, I would put a fuse on the output lead but if you keep the 7th in // it's going to be worse, a fuse has resistance too.

I don't like the + and - crossing and the way wires could rag on wood, be sure your lid can't hurt the wires too, caps on batteries terminals would be nice too.

Wood isn't great if your batteries leak acid.

Second about securing and double checking for ventilation.

[redsky49]

ABYC calls for fusing (OCPD) within 7" of battery. 72" is permitted if cable is sheathed. Check the ABYC requirements for general guidelines.

At the least, epoxy coat the battery box. Better would be to 'glass it.

My concern is that the number of batteries in your system will lead to uneven performance. This would be especially true for the remote seventh battery. I would consider some better way to balance the resistance/voltage drop across the bank. Or perhaps rotate the batteries occasionally - inner batteries to the outside?

Odd number of batteries is not the issue, but the quantity is starting to be an issue.

This is not a comprehensive review, just a few suggestions.

Good luck with your installation. Let us know how the batteries perform for you.

[epiic]

Great tips guys. Thanks!

I got some advice from an expert.

Quote: "In order to balance them, make sure that are hooked up either diagonally or in a spoke manner, where each battery hooks with it's own wire to a central post, like spokes from a hub."

[Sandero]

What's the issue with a wood enclosure for sealed batteries? Chafe is an issue if things are moving. It everything is secured and can't move chafe is unlikely. Secure the batts well. You should cover the terminals to protect them from shorts. Spray posts and connectors with DeOxit or similar. Can't tell what the wire gauge is.... but the install is neat.

I would provide blocking on the sides (wedged in so that the batts cannot slide... And two bars running over top the batteries so they can't drop if the boat rolls. You can attach metal angles to the box and run a piece of notched hardwood or starboard between screwed to the angles. The red and black will fit in the notches.

Now the problem is all the connections to the batteries:

bilge pump(s)
starter... is there a separate bank?
battery monitor sense wires
alternator wires
windlass wires
alt charging sources wires
battery switch
other loads which connect directly to the batteries

You may want several heavy duty busses and need ANL type fuses for loads
fuses.

This looks like a neat and excellent start...

[savoir]

It looks like the battery bank connects to the boat via battery #7 which is out of sight at the top of the picture. The wiring as is will work but the first three batteries will be seriously overloaded under that system. The link to the boat should be changed to equalize the load otherwise the batteries at the bottom of the picture won't be doing any work.

[Frankly]

I have a main house bank (also used for starting) with 4 (6V GC) midships and 2 more in the fwd bilge. The fwd bank is tapped directly for the windlass and bow thruster, the main bank feeds everything else. Fwd and main just connected in parallel with #2 AWG (150 amp fuse on each end). Running this way for 11 years and have never had any problems.

Temporary imbalances will exist (bow thruster pulls 200 amps from the fwd and 100 amps from the main bank), but where voltage imbalances exist in a parallel connection current will flow to equalize the voltage.

Get your fusing worked out, put some epoxy on the inside of the box, and put a little split loom where the positive and negative leads cross (belt and suspenders). Go cruising, I think it will work fine.

[bobfromcanada]

Personally, I'd physically rotate three of those batteries 180 degrees (the ones on the right or the ones on the left). Then it would be possible to route those cables so that there are no crossovers of the positive and negative buses. Electrically it will be the same, but you don't have to worry about a short.

[Wulf]

x2. Bob beat me to it.

Originally Posted by bobfromcanada

Personally, I'd physically rotate three of those batteries 180 degrees (the ones on the right or the ones on the left). Then it would be possible to route those cables so that there are no crossovers of the positive and negative buses. Electrically it will be the same, but you don't have to worry about a short.

[svmobert]

Will try to address several of the points made in a single reply..

1.) There is no inherent issue with odd number of batteries in Parallel, it only matters in Series wiring.
2.) In Parallel wiring you can daisy chain or use a star configuration. With 2-4 batteries, Daisy chaining is "ok", but with 3+ batteries you will find that the middle batteries receive a bit less charge compared to the end batteries. This is what star wiring will solve.
3.) If you are daisy chaining between batteries, you take + from the battery at one end of the bank, and - from the battery at the other end of the bank for your loads. (In your photo, based on the two wires leaving and presumably connecting to the 7th battery, your current wiring breaks the proper daisy chain)
Note: The way it's wired in the photo, where the 7th battery is sort of fronting the other 6, your charging and loads will stress the 7th battery significantly (and also your charge level will be measured on the 7th battery. This will leave the other 6 batteries undercharged over time.
4.) If you are using star wiring, the ideal scenario is that the cables from the central bus bars to the batteries are all the same length. This ensures that the wire resistance is the same for each battery, and means that charging, discharging, voltages will all be essentially equal across all the batteries. Star wiring also makes it relatively easy to remove a bad battery from the bank if needed. since your 7th battery is in a different cabin, maintaining the same cable length for it as for the other 6 batteries *might* be difficult. A little difference isn't that big of a deal though.
5.) The Firefly Oasis batteries are VRLA (roughly equivalent to AGM) so gassing and wood enclosures it not really an issue. Just make sure that the cables are protected from chafe where they meet the wood sides, etc.

All that said, let's address your specific situation..

The 6 batteries pictures ARE wired correctly for a daisy-chain parallel bank. However with the addition of the 7th battery, as you described, the bank is incorrectly wired.

This is no ordinary AGM battery. The Firefly Oasis is essentially an AGM battery with Lithium Battery benefits - They can be charged very quickly, not harmed by sitting partially discharged, can handle PSOC (Partial State Of Charge) conditions for long periods of time without being damaged, and can be deeply discharged (down to 10-20%) without long term damage. What this means is that 6 batteries provide >600ah of USABLE capacity. A 660ah lead-acid, agm, or gel bank would only provide about 300ah of Usable capacity.

My personal recommendation is to dump the 7th battery from the bank, in part because it's probably not necessary, and because it complicates the wiring and charging of the battery bank. If you want to use the 7th battery, I'd consider making it an isolated electronics battery, for SSB radio or other sensitive electronics. Put all your normal house loads, chargers, inverters, etc on the main bank, connect the 7th battery to the bank via an Echo-charger unit or DC-DC converter so that the 7th battery gets charged by the house bank as needed, and then connect your sensitive loads to the isolated battery.

Hopefully that all helps. And by the way, I'm jealous of your Firefly's... Those are on my list if my cruising budget allows, but for now I have a 4x150ah AGM bank that works fine.

[redsky49]

SVMobert covers my concerns. Maybe time for a central busbar for the six batteries, equal length cables, etc.

Never heard it referred to as 'star' wiring, but I catch his drift. (Note the nautical reference???)

It goes without saying, I have no personal experience with Firefly batteries. Talk also with their tech support.