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Old 06-28-2020, 08:29 AM   #1
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Thinking of switching to Lithium House Batteries

I currently have a 2008 Allegro Bus42 QRP with six 6V batteries supplying the House. I have solar and a residential fridge. I am not happy with the performance of the lead acid batteries, or adding water each month.

Costco has Lithium Ion Batteries on sale. So, going from six 6V golf cart batteries (NAPA 8144N - rated at 75A for 120 mins - 230Ah). How many of these 12V Lithium Batteries would be required to match or exceed my current "rated" capacity?

The sizes match up nicely. Here is the link to the Costco Batteries....if you are going to steal my deal...please leave me a couple! Lol....

https://www.costco.com/lion-energy-s...100535965.html
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Old 06-28-2020, 08:37 AM   #2
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If each 12v pair of your batteries has 230 aH rating. Then you currently have 690 aH of storage, or did when the batteries were new. So, 6 of the LiPo batteries with 105 aH would be 630 aH of storage.

Your current Battery bank weighs 456 lbs and the new battery bank would weigh 138 lbs.
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Old 06-28-2020, 09:16 AM   #3
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But the flooded battery’s should only be utilized to 50% so that’s only 345 ah the lithium can be used to 10% so you need less ah for the same run time.

Am I Wrong?
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Old 06-28-2020, 09:59 AM   #4
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Quote:
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But the flooded battery’s should only be utilized to 50% so that’s only 345 ah the lithium can be used to 10% so you need less ah for the same run time.

Am I Wrong?
Thanks...I was thinking that all things being equal (which they are not) - you don't need as much with the Lithium.
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Old 06-28-2020, 10:02 AM   #5
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But the flooded battery’s should only be utilized to 50% so that’s only 345 ah the lithium can be used to 10% so you need less ah for the same run time.

Am I Wrong?
Sort of.

You can draw flooded batteries down to 10%, carefully not to go lower, and shorten their life by about 1/2. That would be if you did it every time you used them.

Doing it occasionally shortens their life about a day each time.

Its the same with lithium batteries but they have 1000s of more cycles in them then flooded batteries.
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Old 06-28-2020, 10:03 AM   #6
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You also may have to change your inverter/charger. Check your manual and see if you can charge the lithium batteries with your current setup
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Old 06-28-2020, 11:04 AM   #7
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Quote:
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But the flooded battery’s should only be utilized to 50% so that’s only 345 ah the lithium can be used to 10% so you need less ah for the same run time.

Am I Wrong?
You are correct. I was answering the question in it's most basic form. I'll bet the OP would be happy with 4 LiPo batteries instead of 6.

Also, I was doing research on Victron AGM batteries yesterday. We don't normally think of them for batteries.

They have some 220 Amp Hour AGM batteries designed to provide over 1000 cycles when taken to 30% depth of discharge. And they say even 500 cycles when 100% discharged. They also don't lose charge when stored as much as normal and they supposedly don't need recharged as fully to prevent sulfation.

They are not the standard "Group" form factor - they are 20" long but they could easily replace 2-group 31 batteries. They weigh as much as two of his 6v batteries do.

In the OP's case two of these would cost $1,000 and provide 440 aH of storage and be usable down to 30% or lower state of charge.

Here's a link.

https://www.solar-electric.com/victr...e-battery.html
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Old 06-28-2020, 11:04 AM   #8
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Quote:
Costco has Lithium Ion Batteries on sale. So, going from six 6V golf cart batteries (NAPA 8144N - rated at 75A for 120 mins - 230Ah). How many of these 12V Lithium Batteries would be required to match or exceed my current "rated" capacity?

For the reasons twinboat stated, I'd go for roughly the same AH capacity with the lithium, which gives you an effective increase in capacity. If you would rather save some $$, go with somewhat less AH and bank on the deeper discharge of the lithiums to provide the reserve you may occasionally want to use.





You didn't say why you were unhappy with the 6v flooded lead-acids, so I'm hedging here. If unhappy because of insufficient AH, you want more capacity. If unhappy because they kept needing water, maybe switching to AGM lead acid would be sufficient. However, if your flooded cell batteries needed water all the time, something was wrong and that alone would cause poor capacity as well as extra work. One weak battery or bad connection in a set of six is enough to do that. Maybe you could be made happy again with 6 new 6v GC2 for a lot less money.
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Old 06-28-2020, 12:58 PM   #9
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your AC charger needs a profile for lithium
your alternator may need something new in between to limit current
LFP batteries will take all the current you can deliver until they are full, unlike FLA where the resistance to current rises as they approach full
you cannot just drop in LFP batteries w/o looking at all the charging sources

one thing i noticed with my old FLA battery, is that i couldn't run the inverter unless the battery was nearly full, as the 150A of current would pull the voltage down - even tho the math said you could

LFP batteries have an extremely flat discharge curve, so i can now draw 150A even when they are @40%
also, they don't have to be charged back up to 100% every day
something most people don't factor in

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Old 06-28-2020, 01:14 PM   #10
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Some LFP can drop in I believe the Costco ones he is looking at have a BMS to let standard charges work but I would recommend doing your due diligence to verify that.

Also while not the best most LFP will charge using a AGM profile just fine just not to 100%.
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Old 06-28-2020, 01:25 PM   #11
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LI are not plug and play... you must change your charger and solar settings plus limit the voltage from your engine alternator. They also need the temperature kept within reason, not too cold or hot.

Last year I bought 880AH of 1 year old AGM for $460 to replace the L6 lead acid. I should get 10 years out of them which should be the last set of batteries I’ll need.
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Old 06-28-2020, 04:21 PM   #12
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Had someone try that. They wouldn't charge up over 60 percent no matter the setting they chose on their Magnum. Back to AGMs for them.
Quote:
Originally Posted by Biljol View Post
Some LFP can drop in I believe the Costco ones he is looking at have a BMS to let standard charges work but I would recommend doing your due diligence to verify that.

Also while not the best most LFP will charge using a AGM profile just fine just not to 100%.
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Old 06-28-2020, 11:43 PM   #13
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The simple answer to this is to disable the charging function of the inverter charger and add a LFP charger that you run off of a 110 outlet when plugged in or the genset is running.

This may not charge as fast but may be a less expensive option than a new inverter/charger.
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Old 06-29-2020, 06:52 AM   #14
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as mentioned above LFP batteries do not like freezing
not sure in the internal BMS on those batteries handles it or not

the BMS is really a safety device to make sure the cells stay within their operating voltages, not something that should be used to overcome poor charging profiles

i.e. you would typically set the low-voltage cutoff on your inverter to be above the LVD in the BMS
the LVD on the BMS would typically be 10V (2.5V/cell)
the HVD on the BMS would be 14.6V (3.65V/cell)
in a LFP battery, it will disconnect charging/loads when either condition is met

operating LFP batteries between 90% & 10% will greatly extend the lifetime number of cycles

another consideration is knowing the SOC
SOC for FLA is reasonably accurate monitoring the battery voltage
with LFP because with the extremely flat discharge curve, measuring the voltage isn't accurate, you really need to have a shunt and measure current in/out
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