Charging Lifepo4 Battery Bank

PennBruce

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Mar 15, 2022
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I am an inexperienced newcomer in the planning stage for upgrading my flooded wet cell house battery bank to Lifepo4's. The new bank will be four 12v 100ah Chins.

I noted on this forum that the 12v 100ah Chins are now being shipped with pouch cells. I will be relocating the house bank to the rear cabin.

Should I be concerned about using pouch cell batteries in a living space?​
Are there advantages/disadvantages to using two 200ah instead as the Chins 200ah are still prismatic cells?​
The standard charge current for the Chins 12v 100ah battery is 20a. Does this mean that my solar controller and my DC/DC charger must be limited to 20a?

The configuration will be four 100w panels for solar charging the house bank and a DC/DC charger charging the house bank from the flooded wet cell starter bank.

Thanks,

Bruce
 

Bud Martin

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Aug 27, 2020
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3,491
I am an inexperienced newcomer in the planning stage for upgrading my flooded wet cell house battery bank to Lifepo4's. The new bank will be four 12v 100ah Chins.

I noted on this forum that the 12v 100ah Chins are now being shipped with pouch cells. I will be relocating the house bank to the rear cabin.

Should I be concerned about using pouch cell batteries in a living space?​
Are there advantages/disadvantages to using two 200ah instead as the Chins 200ah are still prismatic cells?​
The standard charge current for the Chins 12v 100ah battery is 20a. Does this mean that my solar controller and my DC/DC charger must be limited to 20a?

The configuration will be four 100w panels for solar charging the house bank and a DC/DC charger charging the house bank from the flooded wet cell starter bank.

Thanks,

Bruce
So BMS used in Chin can only handle 20A of charging current, then you should set the charge current limit to 20A, higher may not be good for the BMS.
What is the max discharge current of Chins 12V 100Ah? How big are the loads going to be?
 

l00semarble

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Jan 1, 2022
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If the batteries allow 20a charge current that means 4 in parallel can take 80a charge current. Your 400w of solar is not going to even approach that. Even if you actually made 400w which you never will that is 400w/14v = 28 amps of charging. In practice you will see far less than that.

The bigger concern is how will you get enough charging if you are using just solar and alternator. I use a rule of thumb that a sailboat can get about 1/3 of the solar wattage in a-hr per day with high quality PV modules so 400w would give you about 133 a-hr per day. This may be enough to keep up with refrigeration but not really enough to be energy independent in most cases. If you draw your bank down to 80% depth of discharge than you need .8*400 = 320 a-hr to recharge. Without any consumption that would take nearly 3 straight days with solar.

Obviously you will need to get some charging from alternator (or genset+charger). Many DC-DC chargers like the popular Victron unit are fairly small. Victrons will only do 30 amps so you would only recover 30 a-hr per hour of alternator run time.
 

MisterSandals

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Is there a reason (price?) why you are shopping for 4 small batteries instead of fewer larger batteries?
Do the Chins state you can put 4 in parallel?

Same for solar…why 4 little panels?

Look for big cheap panels on Craigslist (or similar). Or if you reveal your city/zip code, maybe someone can point you to deals in your area.
 

PennBruce

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Mar 15, 2022
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This is a motor vessel and the solar is primary for when I am on anchor. The yield will hopefully be better than 1/3. However, I should be considering larger panels.

......I use a rule of thumb that a sailboat can get about 1/3 of the solar wattage in a-hr per day with high quality PV modules so 400w would give you about 133 a-hr per day....

Am I correct to think that when I am underway I'll be charging both from solar and the charger?

Obviously you will need to get some charging from alternator (or genset+charger). Many DC-DC chargers like the popular Victron unit are fairly small. Victrons will only do 30 amps so you would only recover 30 a-hr per hour of alternator run time.

Thanks,

Bruce
 

PennBruce

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Mar 15, 2022
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Two 100ah batteries are slightly less expensive then one 200ah. The smaller batteries are an easier fit although I can also fit two 200ah. The Chins can put 4 in series or parallel.

Is there a reason (price?) why you are shopping for 4 small batteries instead of fewer larger batteries?
Do the Chins state you can put 4 in parallel?

Thanks,

Bruce
 

l00semarble

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This is a motor vessel and the solar is primary for when I am on anchor. The yield will hopefully be better than 1/3. However, I should be considering larger panels.


Am I correct to think that when I am underway I'll be charging both from solar and the charger?
We are making guesses due to incomplete details. What you are basing better than 1/3 of wattage on? Actually producing 1/3 of wattage in a-hr into 12v is fairly optimistic over time in many areas and this assumes you are using excellent monocrystalline panels with the best SunPower brand cells with up to 23% efficiency. Based on your choice of batteries I am guessing you have also gone to Amazon/China for value oriented solar modules so I would guess you are going to see far less than 1/3 of wattage unless you are in the tropics and you can keep your array completely unshaded and aimed at correct azimuth and elevation (basically impossible on a boat.)

When underway (or at anchor) you can only use your charger if you have a generator making 120v AC power.

Unless by charger you actually mean alternator. If this is what you meant than yes you will have the benefit of solar and alternator when motoring. But you will be limited by the rating of the DC-DC chargers which is likely to be smaller than the rating of the alternator.
 

offgridcrazy

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So BMS used in Chin can only handle 20A of charging current, then you should set the charge current limit to 20A, higher may not be good for the BMS.
What is the max discharge current of Chins 12V 100Ah? How big are the loads going to be?
I'd suggest to look at the data sheet again. On the Chins website for the 12v 100amp hour battery it says the standard charging current is 20 amp. But the max continual charging current is 50 amp. I'm new to lithium so I'm not saying your incorrect, just double check that. I'm very interested myself. I'm just about to upgrade my flooded lead acid bank and get lithium. I'm not accustomed to that standard charge current, I've only seen and used the max continual charge current in the past with lead acid.
 

Bud Martin

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There is no data sheet provided by OP, so I'm going with what OP had provided.
 

offgridcrazy

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There is no data sheet provided by OP, so I'm going with what OP had provided.
Ya ok. Well again I'm new to lithium. Here is what's on the Chins site for the 100 amp 12v. I would recommend asking others on here what the difference is between the standard charge rate and max continual charge rate. And all which to calculate by. Good luck, of you get an answer I'd be grateful to know also since I plan to buy some lithium batteries in the next month.
 

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Bud Martin

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I DIY my own battery packs, 4 packs so far, and I am not looking for answer, OP is asking questions without providing the details.
 

Substrate

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The standard charge rate is the recommended one for best overall efficiency vs time. It is a guide, not an absolute.

You can exceed this amperage, as the bms allows (up to a point) when you need to. If you *always* charge at the maximum rate, your cycle lifetime will be a bit shorter.

Likewise, if you charge well under the C/20 rate, and you are attempting to charge the battery to full every cycle, the extended time spent charging is prolonged, and your lifetime will again be a bit shorter. Sometimes we just can't help it in weak solar conditions.

It all has to do with secondary reactions, but that is beyond this thread.
 

CB-OTB

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This is a motor vessel and the solar is primary for when I am on anchor. The yield will hopefully be better than 1/3. However, I should be considering larger panels.
do you mind sharing what vessel you are mounting the solar panels on? I want to mount some panels on my Sundancer, but finding a spot to mount them where they don’t get in the way of the fun is challenging.
 
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