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ICC
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# Posted: 25 Jul 2023 01:53pm
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My 9 year old golf cart GC-2 batteries have worked hard enough and provided good service up until a few months go. They will soon be off to the metal scrapper for the lead salvage value.
I replaced them with an SOK 24 volt 100 amp-hour LiFePO4 battery. 55 lbs. They use 8 grade A LFP 100 amp cells in a steel box with handles. They make there own BMS and both their cells and BMS have an excellent quality record. The BMS has low and high temperature cutoffs and a low voltage disconnect. An external low voltage disconnect might be advised; one that can be programmed with your own low voltage choice like a Victron would be nice. The case is easy to open with 14 screws. The wiring inside is very tidy. Cells and the BMS are serviceable (change 'em if necessary).
$1011 incl shipping from SOK.
I have charged it at home and it will power the cabin as soon as I get back up there. The picture shows it on a bench with my 20 year old Iota 24 volt 25 amp charger. Iota has a new IQ module special for LFP batteries. Just plug it in and it's ready for LFP. The battery has Bluetooth and an app to use.
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gcrank1
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# Posted: 25 Jul 2023 06:55pm
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Wow, 55#, aint that sweet 
Keep us posted on how it goes
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Nobadays
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# Posted: 25 Jul 2023 08:16pm
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Nice!
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ICC
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# Posted: 3 Oct 2023 05:01pm
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The SOK has been performing well. Charges quickly from the solar and it is very nice to have the BMS app on my phone.
Interesting note. About the time I ordered this battery SOK made a slight change to the BMS. THe old version BMS had a user selectable time out when it would go to sleep. With no charge or discharge currents the BMS would go to sleep to save power. Application of a charge or a load current would wake it up. Interval is user adjusted from 0 to 9999 minutes.
The version I got had an improvement that allowed the BMS to be placed in storage mode. No current drain at all. It would be revived by only a charge current. That made it safer for shipping as well as totally removing any parasitic drains. I liked that as I leave it with everything disconnected. Not even the solar hooked up to avoid lightning issues.
The BMS has a low temperature cutoff so it will not charge when below freezing. Excellent.
I thought of a potential problem and wrote to SOK customer care. I asked what would happen, if, the temperature was below freezing and the battery/BMS was left in storage mode. Would the BMS come out of storage mode if the required wakeup charge was applied and then allow some discharge which would in turn warm the battery. OR would the battery need to be brought to above freezing as the wood burning stove warmed the cabin interior, before that battery could be used at all; discharge or charge?
Min from SOK replied within a day. I was told they had encountered that potential [problem and had a BMS with revised firmware. All I had to do was supply a shipping address and they would send me a new BMS with the firmware changes. It arrived by FedEx in about a week.
I installed it today. It was an easy swap and works. That is another reason I was happy I bought the SOK. Many other brands are not serviceable as they are sealed cases.
Here's the battery on its side with the top removed. The new BMS is installed in the lid and the old one on the case.
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ICC
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# Posted: 3 Oct 2023 05:16pm - Edited by: ICC
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One other issue....
How to awaken the BMS from storage mode? Only a charge will wake it. There is no grid to plug into and I don't want to leave a generator up there over winter or have to truck it up. Plus sometimes in winter I can't drive up the last 1/4 mile hill because of drifted snow. Then I snoeshoe the last bit.
So I made a wakeup charger.
1. A DROK DC-DC buck-boost converter
2. An 11.1 volt Li-ion battery pack with a USB charger
3. Some wire, connectors and a switch
4. A small box
The 11.1 volts from the small battery pack is fed into the DROK converter. The DROK boosts the voltage to whatever you want (up to 30 volts). 28.8+ is a good charging voltage. The DROK can supply 2 amps easily and that is plenty to wakeup the BMS.
The output voltage is variable from less than 1 volt to 30 volts. The current is also adjustable up to about 4 amps. Even though the input voltage could be as low as 5.5 volts it performs with better reliability when the input voltage is at least 8 volts. I wanted something simple that could be recharged without any bulky charger or the need to remove cells and use a separate charger.
Once the BMS is awake and the battery warmed the solar can charge the battery.
Much better than lugging a fuel-burning generator when all I need is a wakeup.
I'll post another picture once I assemble everything in the box. (the white 4-pin connector on the battery is for the charger)
Might be useful to someone else....
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gcrank1
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# Posted: 3 Oct 2023 06:44pm
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Looks like you chose wisely 
A lot of good features for actually less money than I spent on 2x 12v LFP bats (I went with 12v because the rest of my 'stuff' was 12v).
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scott100
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# Posted: 3 Oct 2023 08:59pm
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Looks like a nice unit. The serviceability is a real plus.
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Steve_S
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# Posted: 4 Oct 2023 04:57am
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SOK has been well tested, torn down & reviewed by many. They evolved & refined their products pretty quick and they are doing really good stuff now. I'm sure you'll be quite happy with your choice.
Here is the SOK US Site so everyone interested can review their goodies.
NOTE: Certifications Information:
UL1973 & IEC62619 for Battery cells.
https://www.us.sokbattery.com/
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ICC
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# Posted: 4 Oct 2023 10:12pm - Edited by: ICC
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I assembled my little BMS "waker-upper" in a box.
The 3 cell battery power source is in the left end of the box. I used a DC barrel connector plug set instead of an on-off switch. Insert the plug and that completes the circuit. The box lid cannot be closed with the plug inserted, so the battery will be disconnected to close the lid.
So, connect the magic box to the andersen plugs from the battery. Insert the barrel plug to activate the dc-dc converter. Press the right-most green button the turn on the converter. Within 2 seconds the BMS wakes up. Remove the barrel plug to shut it down.
Please excuse the reflections of the ceiling panel lights
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ICC
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# Posted: 4 Oct 2023 10:13pm
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2 more images
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