LiFePO4 charging question

[reubenray]

I pulled my battery and at home I checked it with my multi-meter. It showed my battery at 13.35 instead of the 13.2 that my Bluetooth connection showed. I need to figure out how to draw the battery down some. I was in a rush to pull it out due to cold weather coming in this week.

 

[Scott'n'Wendy]

Is this a shunt?

Looks like a Renogy brand shunt. Or a brand trying to look like Renogy?

 

[triplethreat]

I pulled my battery and at home I checked it with my multi-meter. It showed my battery at 13.35 instead of the 13.2 that my Bluetooth connection showed. I need to figure out how to draw the battery down some. I was in a rush to pull it out due to cold weather coming in this week.

Now that you've got it home and a hopefully decent multi-meter, try to get the battery voltage down to right at 13.13 or very close to it. That should put you right at about 60% on the SOC.......depending on how accurate your meter is. Do you have anything like an old automotive headlight laying around....or a blower fan, an old windshield wiper motor? That would work to pull some amps out of the battery.....just not real quickly.

 

[reubenray]

I have an old cb radio that is 12v. Will this work.

 

[LanerC]

You're welcome. Are three going to be enough....they are 7W each. I put 4 in mine, but I have a fairly large box with a 302AH battery inside that is also in a compression jig to keep the cells together.

After I thought about it, I ordered 3 more. It sounds like they dont get real hot so Im thinking of putting them in-between the 4 lithium 100ah batteries and on the ends. The batteries are not in a box, just strapped down. Do you think that should be alright?

 

[reubenray]

Now that you've got it home and a hopefully decent multi-meter, try to get the battery voltage down to right at 13.13 or very close to it. That should put you right at about 60% on the SOC.......depending on how accurate your meter is. Do you have anything like an old automotive headlight laying around....or a blower fan, an old windshield wiper motor? That would work to pull some amps out of the battery.....just not real quickly.

My multi-meter is a very basic one. I will look for a better one.

 

[coglesby]

My multi-meter is a very basic one. I will look for a better one on Amazon.

I recommend you get a clamp ammeter with voltage measurement capability. That way you can measure current if you need to as well.

 

[triplethreat]

I recommend you get a clamp ammeter with voltage measurement capability. That way you can measure current if you need to as well.

And to add a bit to that, there are many, many clamp on type ammeters out there, but you need to makes sure that they are made to work for Direct Current (DC). The ones that do have the DC functionality will also most likely also have Alternating Current (AC) functionality too. A straight AC ammeter will NOT read DC

 

[dryfly]

There would be nothing wrong with using the lights except that in most of the newer ones, they are all LED lights that pull very little current. I'm guessing that if I turned every single light on in the trailer it would still not quite be as much current draw as the one 12VDC heater.

Yeah I agree. All my lights are LED. I'll measure the current and see what they draw. A 12vdc heater would be the way to go. I can't think of anything else that would make a good load unless an inverter was available for AC devices.

 

[triplethreat]

I have an old cb radio that is 12v. Will this work.

Anything that uses 12VDC will help, but it's then a matter of how much or probably how little amount of current it will consume. I honestly don't know current values of an old CB radio, but I would imagine that they don't pull a lot of current. Of course, that is just a guess on my part.

 

[coglesby]

And to add a bit to that, there are many, many clamp on type ammeters out there, but you need to makes sure that they are made to work for Direct Current (DC). The ones that do have the DC functionality will also most likely also have Alternating Current (AC) functionality too. A straight AC ammeter will NOT read DC

Here’s the one I have. The func button changes between AC and DC.

Amazon.com

 

[Hoopy Frood]

Here’s the one I have. The func button changes between AC and DC.

Amazon.com

Odd that it doesn't mention DC current.

 

[triplethreat]

Here’s the one I have. The func button changes between AC and DC.

Amazon.com

I see NO DC current function on that one. AC and DC voltage, but not DC current. In fact, in the description it specifically states it DOES NOT measure DC current.

 

[coglesby]

Odd that it doesn't mention DC current.

Thanks for correcting me. Here is the right one.

Amazon.com

 

[reubenray]

Thanks for correcting me. Here is the right one.

Amazon.com

I am glad I waited on ordering something. My current multi-meter measures only DC voltage, not current.

 

[coglesby]

Comes in handy to see how much current is going into your battery when charging

 

[Hoopy Frood]

Comes in handy to see how much current is going into your battery when charging

Or when you want to see how much drain you have when the Battery Disconnect Switch is OFF.

 

[JPS350]

A dedicated battery monitor shunt at your battery bank is even better. It tells you state of charge and remaining amp hours as well as current and voltage.

The Victron ones are nice, but expensive. I have one on my off grid cabin solar bank because ...the cabin deserves it. For the camper, I have one of these. It works well too, once you translate the instruction manual to an English that you and I can understand.

https://www.amazon.com/gp/product/B088RG27LS/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

 

[coglesby]

A dedicated battery monitor shunt at your battery bank is even better. It tells you state of charge and remaining amp hours as well as current and voltage.

The Victron ones are nice, but expensive. I have one on my off grid cabin solar bank because ...the cabin deserves it. For the camper, I have one of these. It works well too, once you translate the instruction manual to an English that you and I can understand.

https://www.amazon.com/gp/product/B088RG27LS/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

Different but not so sure it’s better. It’s nice to be able to monitor constantly but you only get total current. I want to know what each component is drawing.

 

[JPS350]

Different but not so sure it’s better. It’s nice to be able to monitor constantly but you only get total current. I want to know what each component is drawing.

Better for monitoring your system in use. You need a multimeter anyway. That's what you pull out when things don't work.