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Old 22-01-2013, 12:44   #1351

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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

dockhead, in theory a four-cell lithium battery is a SIXTEEN volt battery, being used as a 12-volt battery by intetionally undercharging the cells. So if you charge it to 14 volts, in theory you can use it at 14 volts, and make Icom happy because most of their gear is rated 13.8-14.4 volts, to be used with alternators not batteries.

Icom is quirky that way. Some antiques like Drake actually were designed to operate on ten volts, so a 12-volt battery kept them perfectly happy. Icom? Different design criteria. And some of the Icom radios (their IC-706 very successfulham radio) actually use nominally rated 15-volt parts across the power input. Since those parts are only rated within 10%...Icom has had failures from normal voltages. You'd want to check on your radio before determining the voltage you hook up to it, and in any case, make Real Damn Sure that a higher battery charging power physically cannot be connected while the radio is also connected to the battery, or you risk a fried SSB.

So there's a downside to having a "special" separate reserve battery on the SSB. I'd use an AGM so it can play nicely with the other kids, relying on ship's power to charge that and run the radio in normal use.
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Old 22-01-2013, 12:56   #1352
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Originally Posted by hellosailor View Post
ebaugh-
One big problem with your circuit. If both switches are engaged...oopsie. That's an application where a double-throw-center-off switch should be used, or something similiar, so it is physically impossible to close both contacts at once.
I can't see the problem ?

Can you elaborate on "...oopsie." ?
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Old 22-01-2013, 13:03   #1353

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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

If both switches are depressed at once, both diodes are bypassed. So "oopsie" no telling what happens next. Not knowing what loads may develop, that could range from no problem at all, to an unwanted dead battery, to an overheat. And of course a dead battery could permanently damage a cell.

Easier to just use a switch that ensures there is no "both" possible.
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Old 22-01-2013, 13:05   #1354
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Originally Posted by hellosailor View Post
ebaugh-
One big problem with your circuit. If both switches are engaged...oopsie. That's an application where a double-throw-center-off switch should be used, or something similiar, so it is physically impossible to close both contacts at once.
If I understand the proposed design, the whole idea is to have both contacts engaged (switched ON) in normal operation. Diodes are added to be able to supply loads when HVC is present OR to recover from LVC, respectively.

The only thing I don't quite like in this design is having two pairs of contacts carrying full load. Contacts oxidise...
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Old 22-01-2013, 13:12   #1355
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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No, I was talking about a LiFePo motorcycle batt.

The one you pointed to has more capacity than I thought I needed, but it's cheap! I guess it would work well. Does it have built in BMS? I guess I can call them. And how do I get it to the UK? I could take it in my baggage, but I guess it's hazmat and verboten?
As it is a packaged 12 volt battery using (4) cells, I would think it has BMS built in. It has a 1C or less recommended discharge, and since the cells by themselves have a 3C rating, I would think it was the components of the BMS that had them de-rate it. But like you said, just ask. As to shipping, they shipped to me by UPS, I don't think this type of lithium battery has shipping restrictions, but I'm not sure. The regulars on this thread will know, plus Balqon would also know.
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Old 22-01-2013, 13:39   #1356
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Hello Sailor,

My LiFePO4 batteries stay around 13.3 volts for 95% of their discharge curve. Lithium of the chemistry we aren't discussing here has a single cell voltage of 3.7 vs 3.2 of LiFePO4. Even though nominal is stated at 3.2, mine are 3.325, and I also use in other apps the 3.7 volt lithium and they seem to stay at about 3.77, so 4 of these in series just a bit over 15 volts, but like I said, 13.3 for the LiFePO4. I've had solid state HF radios since the Atlas 210, and I'm certain all operate just fine from 12 volts of a tired LA battery, to 14.8 volts of the automotive charging voltage on the top end, so the 13.3 volts of the battery I recommended is just fine. I only mentioned that if his house bank was 12 volt LA (which it isn't, he uses a 24 volt system), he wouldn't be able to charge his dedicated radio battery via the house bank. His choice of a dedicated battery at the radio is mandated for the ships I have sailed on.

This 3.7 volt lithium cell is 4.19 volts right off the charger, but has more pronounced knees at both ends of the discharge curve than the LiFePO4.
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Old 22-01-2013, 13:41   #1357
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Quote:
Originally Posted by mrm View Post

If I understand the proposed design, the whole idea is to have both contacts engaged (switched ON) in normal operation. Diodes are added to be able to supply loads when HVC is present OR to recover from LVC, respectively.

The only thing I don't quite like in this design is having two pairs of contacts carrying full load. Contacts oxidise...
This is correct. They would both normally be latched 24x7x365. This may help with the oxidation, but it is another .2A current draw for the second coil.
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Old 22-01-2013, 14:56   #1358
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

As I stated earlier, my plan is to gently cycle my 260Ah bank along the flat part of the LiFePO4 charge curve, normally between 13.25 and 13.85V.

However, today I manually gave it a rare complete charge, for three reasons:

1. I wanted to completely reduce any "rust" (oxidation products) that may have formed on the electrodes during my cells' 2+ years on the shelf.
2. I wanted to see how well the individual cell voltages stayed together since they were all bottom balanced in parallel at 3.088V.
3. I wanted to measure my battery's true capacity at what will be my typical discharge rate.

I set my Morningstar TS-45 solar charge controller to a setpoint of 14.75V, but was surprised to measure the actual holding voltage at 14.85. I guess Morningstar isn't particularly concerned about voltage accuracy---glad I did not spend an extra $100 on a remote display that would have been a whole tenth of a volt off!

Once at 14.85V it entered an absorption phase, where the voltage was held constant and the charge current was allowed to taper off naturally. In about two hours, it fell from 18A to 5.2A---my target cutoff current of C/50.

I then electrically isolated the battery so that I could measure the cell voltages once they stabilized around 3.45V/cell, after about 30 minutes. The readings were 3.449, 3.456, 3.424, and 3.456V. So two of the cells were identical, three of them were within 7mV of each other, and the fourth was within 32mV. I am pleased with these results. Also quite pleased to observe no cell bloating

I have now shut off my charge controller at the breaker, and over the next several days will gradually fully discharge the battery, meanwhile measuring the amp-hours. Hopefully I will see a good inflated result like others have reported, well over 300Ah in my case.

I will also be occasionally measuring voltage sag / discharge current on various loads to see if the bank's internal resistance has improved from around the 8 millohms I last measured.

Doug
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Old 22-01-2013, 15:11   #1359
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Doug,

Since your cells are between Maine Sail's 400 a-hr and my little 100 a-hr, I'll be curious of the results. Since you said discharge will take several days, I'm betting your assumption of over 300 a-hr is a sure thing. These aren't your dad's weak kneed LAs. lol
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Old 22-01-2013, 15:47   #1360
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

CURIOSITY so maybe a naive question. I'm just reading the guff on the GSL MPPT60-2L Solar regulator for Lithium that i've bought for our install.

This regulator will handle inputs from 16volt to 95volts, it regulates this varying voltage to the Lithiums requirements.

Why then do we not install one regulator similar to this that we feed any and all source's of charge into? Removing issues of those sources having to match Lithium req's. ie use our existng LA charging sources.

Is it a sensing problem for say an alternator's regulator?
If so wouldn't the Lithium reg give that regulator a full battery signal?

Apologies if deemed a stupid question. Cheers
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Old 22-01-2013, 15:52   #1361
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I ran my first full charge in the last 90-100 partial cycles yesterday to 3.6V. 48 100Ah cells, 12P/4S. Normal charge is 3.4-3.45V. At 100A charge, low cell was 3.44V and high 3.6V, reduced the current to 30A, the 3.6V cell slowly declined to 3.53V. I do have balancers that kick in at 3.55V so that, plus I think there is some redistribution of charge between my 12 paralleled cells going on. The same high cell 30-40 minutes later got back to 3.6V and I stopped the test. The other cells were 3.53 to 3.55V. Under a small load, 10 minutes later, cells 3 at 3.51 or 3.52 and the same high cell at 3.54V. I did not watch after, but discharging below 3.4 they have always been the same +-.01V. Conclusion, no need to rebalance. I don't know anyone else using lots of paralleled cells, but in this configuration, there may be a greater need to watch the high cell under higher charge rates if you are targeting 100% charge.

Prior to this test, that high cell had been the low one...reason being one of the cell boards was faulty adding an additional load to that cell. I replaced the board, and added charge to that cell to even things out. I think I may have overdone it a bit, it was the high cell after the board replacement, but not by quite this margin.
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Old 22-01-2013, 16:00   #1362
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Quote:
Originally Posted by Lagoon4us View Post
CURIOSITY so maybe a naive question. I'm just reading the guff on the GSL MPPT60-2L Solar regulator for Lithium that i've bought for our install.

This regulator will handle inputs from 16volt to 95volts, it regulates this varying voltage to the Lithiums requirements.

Why then do we not install one regulator similar to this that we feed any and all source's of charge into? Removing issues of those sources having to match Lithium req's. ie use our existng LA charging sources.

Is it a sensing problem for say an alternator's regulator?
If so wouldn't the Lithium reg give that regulator a full battery signal?

Apologies if deemed a stupid question. Cheers
You could if you could find one at a reasonable price that would handle the needed currents 100-200A at 12V. The solar ones won't generally do that. I think you might also need at least a small battery buffer on any alternator. It also costs about 10% or so loss of charge capability in the transition.
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Old 22-01-2013, 17:19   #1363
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

We use Plasmatronics PWM controllers to drive solid state relays, all the charging sources go through the relays. The relays are mounted on tunnel heat sink with a 50 deg C thermostat switch to drive a fan to cool the heatsink/relays if needed. We developed a simple timer circuit from a commonly available kit to interrupt the power supply to the solid state relays stopping any charging, this includes one on the 240vac side of the mains charger. The junsi cell logger drives the timer circuit via it’s alarm port.
Basically, a single charge controller with a secondary back up, cheap, easy DIY and if you add a shunt kit to The plasmatronics unit it a battery monitor as well with a long recorded history as well, 30 days for the PL series and 120 days for the Dingo series.
Mine has operated for 2 yrs now, the cells stay perfectly balanced, went the sun is shining 130 amps pour into the battery till it's full, couldn't be easier. If you want add a low cell voltage warning device, link a smoke alarm across the Junsi cell logger alarm port wires, you simply can't ignore one of those things going off :lol:
people want to make major complicated systems with lots to go wrong, keep it simple.

T1 Terry
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Old 22-01-2013, 18:19   #1364
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

An interesting comment from 'MOTOR BOAT' Mag:-

For you Internet fans worried about marine lithium-ion batteries blowing up after reading about batteries exploding in computers and cell phones, the batteries used in boats typically use lithium-iron phosphate, which makes them much more stable as a power source. “Accidents like those are not possible in iron-phosphate chemistry,” says Bakken. “You can punch a hole in one of our batteries and there will be no catastrophic failure. We’ve done it with a drill.”
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Old 22-01-2013, 19:05   #1365
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Originally Posted by T1 Terry View Post
We use Plasmatronics PWM controllers to drive solid state relays, all the charging sources go through the relays. The relays are mounted on tunnel heat sink with a 50 deg C thermostat switch to drive a fan to cool the heatsink/relays if needed. We developed a simple timer circuit from a commonly available kit to interrupt the power supply to the solid state relays stopping any charging, this includes one on the 240vac side of the mains charger. The junsi cell logger drives the timer circuit via it’s alarm port.
Basically, a single charge controller with a secondary back up, cheap, easy DIY and if you add a shunt kit to The plasmatronics unit it a battery monitor as well with a long recorded history as well, 30 days for the PL series and 120 days for the Dingo series.
Mine has operated for 2 yrs now, the cells stay perfectly balanced, went the sun is shining 130 amps pour into the battery till it's full, couldn't be easier. If you want add a low cell voltage warning device, link a smoke alarm across the Junsi cell logger alarm port wires, you simply can't ignore one of those things going off :lol:
people want to make major complicated systems with lots to go wrong, keep it simple.

T1 Terry
Ok is it logical/feasible/useful to fit the Junsie's so that if an 'over voltage' situation came up it disconnects the charge circuit bus via a switching relay thus allowing current to be still drawn and have the smoke alarm go off it's tits (till reset)?

Then if 'under voltage' situation is detected an alarm sounds (smoke alarm again) activating a timer say 5 minutes culminating in supply being cut also using a switching relay? Giving you fair warning to act....

What i'm getting at is we are often ashore and need some form of safe control whilst not onboard.
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