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Old 18-01-2022, 12:21   #1
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Firefly battery bank restoration charge question

As mentioned on another recent thread here (I did not want to hijack that thread) , I am interested in doing a restoration charge on my firefly bank. Just looking for best practices and tips or tricks to do this properly

Have a bank of 2 G31 . They are fully charged now (<.5a current at 14.4v while on charge)

To discharge, should I
1) separate the batteries and discharge/recharge each individually, or do it as a bank?
2) best way to discharge, and can you over-discharge?
* I was thinking of putting a car's headlight across the battery terminals to discharge pretty fast. I was thinking of running the refrigerator, but that has a cutoff to save the batteries. Everything is LED on the boat, so no real high draw devices on board.
* When should I disconnect the load? Can I leave it on too long ( say days) or should I keep an eye on it and take them off at about 10.5v or so?

Any tips/tricks that a non-professional DIY can do without the need to buy expensive equipment?
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Old 18-01-2022, 14:04   #2
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Re: Firefly battery bank restoration charge question

I am sure you looked at the "manual"

To perform the restoration charge: charge the G31 to 14.4V or the 4V/450AH to 4.8V and continue to charge until the current drops to 0.5 A on the G31 or 3A on a 4V/450AH. Fully discharge the battery to 10.5V (G31) or 3.5V (4V/450AH), and then repeat the same charge cycle.

Personally I would not and have not done this unless you have a lost capacity reason. Far as how you discharge them I guess it probably doesn't matter. But it would seem the best way would be to discharge at about the C20 rate and do a capacity test while doing it.

Post what you find in the other long term user thread please.
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Old 18-01-2022, 15:02   #3
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Re: Firefly battery bank restoration charge question

Yes I posted a good length anecdotal reply to the other post about my experience.

There has been some noticeable performance hit to the batteries, as I flat out don't take care of them, even in the slightest. Already surviving 2x as long as FLA batteries!

Only doing this because I think it is time to try.

As I never did it before, just looking to get ideas on best practices on HOW to do it. I have a copy of the manual imprinted in my brain.. Just worried mostly about the mechanics of draining the battery the best way without doing any further damage!
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Old 18-01-2022, 15:39   #4
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Re: Firefly battery bank restoration charge question

I have been abusing my bank or 5 G31s for three years or so. Much of this has been 4-5 month trips without shore power and minimal engine use on a sailboat. It is rare for me to hit 100% SOC, but when I do the batteries “seem” to perform a bit better for a while. Interesting throughout this is that my battery monitor, Balmar SG200, still always shows 100% state of health. Do you have some similar monitor? And if so does it show any change in SOH over your use?
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Old 18-01-2022, 15:43   #5
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Re: Firefly battery bank restoration charge question

I have the old, original Smartgauge. The reading always seems to be 'reasonable'. I dont have the skills or tools to test the accuracy .

It used to stay at 100% for a while, now it seems to drop off to 99 much faster, and capacity seems to be a bit down... hence my question of properly discharging to do a restoration charge

Unsure if you saw and participated in the thread (I put my experience in)
https://www.cruisersforum.com/forums...up-258811.html
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Old 19-01-2022, 01:28   #6
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Re: Firefly battery bank restoration charge question

A 60w car headlight would be about 5a. Which should be about 23h to discharge a single perfect condition firefly down to 10.5v That is the perfect rate to test at.

The issue is it may last 5 hours, 10h, 20h. Desending on battery condition. So you can’t just leave it and come back 20h later. It may be at 1v and totally f*cked.

The best is to have a cutoff device. A victron 65a battery protect smart is a cheap cutoff. You can just set to 10.5v and the light will shut off at 10.5v for a perfect discharge. However you won’t know how long it went or how good the battery was if not watching. Which is important to know. Unless you also put an ah counter in as well.

Lots of fireflies I have tested only lasted about 4h instead of 20. Because they are all failing.
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Old 19-01-2022, 05:46   #7
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Re: Firefly battery bank restoration charge question

Quote:
Originally Posted by smac999 View Post

Lots of fireflies I have tested only lasted about 4h instead of 20. Because they are all failing.
I hate to ask as this thread drift at only post 6. But how were those failed batteries used? Were they on boats that mostly lived at dock with shore power and the battery charger on, or were off grid boats?
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Old 19-01-2022, 05:53   #8
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Re: Firefly battery bank restoration charge question

[QUOTE=phantomracer;3557375]... hence my question of properly discharging to do a restoration charge
/QUOTE]

I still feel you should try to use something close to the 20 hour rate (around 10-12amps for 2 batteries). This sounds more than you normally use. Don't get too focused on being perfect as in real use it matters little if your batteries are 100% capacity or only 95%. I would think you need to plan to do 3 times. Twice for the recovery procedure and once again to test capacity.

I look forward to learning how it comes out and changes from initial discharge to final capacity.
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Old 19-01-2022, 07:57   #9
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Re: Firefly battery bank restoration charge question

Quote:
Originally Posted by sailorboy1 View Post
hence my question of properly discharging to do a restoration charge


I still feel you should try to use something close to the 20 hour rate (around 10-12amps for 2 batteries). This sounds more than you normally use. Don't get too focused on being perfect as in real use it matters little if your batteries are 100% capacity or only 95%. I would think you need to plan to do 3 times. Twice for the recovery procedure and once again to test capacity.

I look forward to learning how it comes out and changes from initial discharge to final capacity.
I think I can scrounge up 3-4 headlights to drain it faster. I think the high beam is about 8-9amp, so maybe use 3. I will do my best to keep an eye on it during the draining. and keep an eye on how long everything takes.

Instead of headlights , could i use something like this ? Electronic-Programmable-Resistance-Protection Or would there be a better (similar price point) option. I am not opposed to spending a bit of money to get better results and/or be safter, I just don't want to throw crazy money at it.

Trying to do a good job, I just don't want to make things worse. The batteries are still more than acceptable. Be nice to get them like new, or as close as possible. They have already far exceeded the performance of the FLA batteries I had

I use a power supply to do the charging (10a) , which seems to do a good job.
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Old 19-01-2022, 22:00   #10
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Re: Firefly battery bank restoration charge question

I did the same firefly restoration discharge using 50watt 12V halogen bulbs. Super cheap online. I put 10 in parallel. Worked great.

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Old 20-01-2022, 02:22   #11
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Re: Firefly battery bank restoration charge question

I had a failed Firefly and second one which was badly damaged by being in parallel with the failed battery.

It was recommended to me to do a restoration charge. The most important parts of the procedure as I recall it was:

to discharge fairly deeply 20-30 remaining capacity , does not matter how fast.

to recharge with a very high c-rate (but below the max charge rate per the spec sheet)

to hold the voltage up to around 14.9 (at 25c) for an extended period of time.

You should phone the vendor perhaps on some advice for this?

BritC
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Old 20-01-2022, 06:55   #12
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Re: Firefly battery bank restoration charge question

well the above definitely is not per the manual
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Old 20-01-2022, 08:52   #13
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Re: Firefly battery bank restoration charge question

Thoughts on my plan..

I will try and record the times it takes for each step

separate out the batteries (2 G31)
Doing 1 battery at a time:
  • fully charge batteries
  • discharge to 10.5v using 1 halogen car headlight battery (5-6amp)
  • Charge using the 10a bench power supply I have. (yes I know, 10a, but it is what I have)
  • charge CC til I get to 14.4v
  • switch to CV til I get under .5a
  • repeat to test for any improvement
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Old 20-01-2022, 12:30   #14
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Re: Firefly battery bank restoration charge question

Quote:
Originally Posted by phantomracer View Post
Thoughts on my plan..

I will try and record the times it takes for each step

separate out the batteries (2 G31)
Doing 1 battery at a time:
  • fully charge batteries
  • discharge to 10.5v using 1 halogen car headlight battery (5-6amp)
  • Charge using the 10a bench power supply I have. (yes I know, 10a, but it is what I have)
  • charge CC til I get to 14.4v
  • switch to CV til I get under .5a
  • repeat to test for any improvement
If you can not do the fast charge of at least 0.2C (23 amps) I think you are just wasting you time and damaging your batteries for no reason. The manual says to do rapid charge of 0.4C, but if you ask they will say 0.2C is probably enough.
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Old 20-01-2022, 12:57   #15
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Re: Firefly battery bank restoration charge question

Quote:
Originally Posted by sailorboy1 View Post
If you can not do the fast charge of at least 0.2C (23 amps) I think you are just wasting you time and damaging your batteries for no reason. The manual says to do rapid charge of 0.4C, but if you ask they will say 0.2C is probably enough.
I will see if I can get a more powerful charger.. It is really only needed til it gets to 14.4v on bulk.. then the amps should drop.. But I will try and either buy or borrow a more powerful charger
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