Simplest way to charge a standalone LFP battery?

[Aphers]

In addition to my yacht's main house bank, I am going to buy a small (60-100Ah) drop-in type LFP battery. Primarily this will be used for the trolling motor on my dinghy.
I can buy a very cheap 'Ultramax' 60Ah battery- £245 including a charger. But it's only just big enough and I bet the BMS inside it would die pretty quickly. The trolling motor draws nearly 60Ah so the poot thing would be working hard.
There are better options available for a little more money (looking specifically at a Sterling product) but these don't include a charger.

So, to get to the point- I want a simple way of charging a standalone lithium battery. A 240v AC charger would actually be my preference, yes it's less efficient to do it this way on the yacht but I will also want to be able to charge it up at home etc. Convenience is more important than efficiency for this task.

 

[Diysolar123]

the simplest way is to just buy a lifepo4 battery charger for the voltage of the battery you are buying.
There are many options that can cost less based on your interest and skill by taking the DIY route but you cannot beat the "convenience" of just buying the charger made for the batteries. There is a good chance whoever you are buying the battery from will sell a charger,e.g., battleborn has a large selection of chargers.

 

[reg]

I'd suggest that you have a look at chargers made by the Dutch company Victron Energy. I just purchased a Victron charger myself and have now tried out the charger and the Victron app. I think that it's an excellent product. Info and links in this post: https://diysolarforum.com/threads/s...-lithium-werks-valence-for-dc-ac-power.20458/

My charger is IP65 "water resistant", but Victron also makes an IP67. It also makes LiFePO4 batteries and has a fair amount of focus on the marine market.

 

[Q-Dog]

My Noco Genius car battery charger has a Lithium setting, but since my home battery backup is 24 volts I haven't investigated what that means. I would ask the battery vendor if they have a preferred charger.

 

[Aphers]

I did contact Sterling, but their suggested charger is a 30A beast costing more than the battery.
I don't really need to be able to charge quickly, an overnight charge is fine.

 

[DerpsyDoodler]

I did contact Sterling, but their suggested charger is a 30A beast costing more than the battery.
I don't really need to be able to charge quickly, an overnight charge is fine.

Buy a $60 10amp variable power supply off amazon. refer to the top balancing resource. Just note that you won’t be top balancing. You can also buy a 35a aims charger off Amazon for about $230 ish.

 

[Aphers]

Buy a $60 10amp variable power supply off amazon. refer to the top balancing resource. Just note that you won’t be top balancing. You can also buy a 35a aims charger off Amazon for about $230 ish.

How do I get the variable power supply to not overcharge? Or do I just trust the BMS to handle that?

 

[DerpsyDoodler]

Frankly, I didn’t read your whole post until now. I read your “straight to the point”. in the context of “convenience is more important”, perhaps:

A converter/charger or a dc-dc charger might be more suitable, depending on how you plan to implement your use case.

 

[Aphers]

Bumping this topic as I still haven't got an answer that really works.

The battery I've chosen (although not yet purchased) is 0.5C max charge rate, i.e. 30A.
I'm trying to find a way of charging it that doesn't cost the earth- this is a sub £300 battery, I'm not spending the same again on the charger. I'd be perfectly happy with a 5-10A charge rate.

As a zero cost option, I guess I could just use my existing 40A MPPT and charge directly from my solar panels- of course I'd need to unplug a panel or two to prevent the current going above 30A. This isn't exactly an ideal solution, I'll want to be able to recharge overnight.

I don't suppose the load port of the MPPT would be any use for this?

For a low cost AC charger, anything wrong with this sort of thing? https://batteryempire.co.uk/12v-agm...zxc1HWugUbpr0pUHWrpO8jxpkbMFq9p4aAordEALw_wcB

 

[Just John]

Bumping this topic as I still haven't got an answer that really works.

The battery I've chosen (although not yet purchased) is 0.5C max charge rate, i.e. 30A.
I'm trying to find a way of charging it that doesn't cost the earth- this is a sub £300 battery, I'm not spending the same again on the charger. I'd be perfectly happy with a 5-10A charge rate.

As a zero cost option, I guess I could just use my existing 40A MPPT and charge directly from my solar panels- of course I'd need to unplug a panel or two to prevent the current going above 30A. This isn't exactly an ideal solution, I'll want to be able to recharge overnight.

I don't suppose the load port of the MPPT would be any use for this?

For a low cost AC charger, anything wrong with this sort of thing? https://batteryempire.co.uk/12v-agm...zxc1HWugUbpr0pUHWrpO8jxpkbMFq9p4aAordEALw_wcB

Use a cheap 10 amp power supply, set the voltage to 13.6v or 13.8v, connect, and wait until current drops below one amp.
As long as the cells are reasonably balanced, should get you 98%, cheap and easy.

 

[Diysolar123]

Bumping this topic as I still haven't got an answer that really works.

The battery I've chosen (although not yet purchased) is 0.5C max charge rate, i.e. 30A.
I'm trying to find a way of charging it that doesn't cost the earth- this is a sub £300 battery, I'm not spending the same again on the charger. I'd be perfectly happy with a 5-10A charge rate.

a rather safe battery charger is an isdt Q8 max...it is basically a high current DC to DC converter that is programmable.

 

[Just John]

a rather safe battery charger is an isdt Q8 max...it is basically a high current DC to DC converter that is programmable.

It's a nice charger, but not very useful for a sealed pre-built battery. Then there is the cheap part, since it requires another power supply to make it work.

 

[time2roll]

For a low cost AC charger, anything wrong with this sort of thing? https://batteryempire.co.uk/12v-agm...zxc1HWugUbpr0pUHWrpO8jxpkbMFq9p4aAordEALw_wcB

That charger is fine.

 

[Just John]

Bumping this topic as I still haven't got an answer that really works.

The battery I've chosen (although not yet purchased) is 0.5C max charge rate, i.e. 30A.
I'm trying to find a way of charging it that doesn't cost the earth- this is a sub £300 battery, I'm not spending the same again on the charger. I'd be perfectly happy with a 5-10A charge rate.

As a zero cost option, I guess I could just use my existing 40A MPPT and charge directly from my solar panels- of course I'd need to unplug a panel or two to prevent the current going above 30A. This isn't exactly an ideal solution, I'll want to be able to recharge overnight.

I don't suppose the load port of the MPPT would be any use for this?

For a low cost AC charger, anything wrong with this sort of thing? https://batteryempire.co.uk/12v-agm...zxc1HWugUbpr0pUHWrpO8jxpkbMFq9p4aAordEALw_wcB

I suggest something like this, works well.

DC Power Supply Variable 3 Digital LED Display Adjustable Regulated Switching Power Supply Digital (30V 10A) : Amazon.co.uk: DIY & Tools

Shop DC Power Supply Variable 3 Digital LED Display Adjustable Regulated Switching Power Supply Digital (30V 10A). Free delivery on eligible orders of £20 or more.

www.amazon.co.uk

 

[Aphers]

It's a nice charger, but not very useful for a sealed pre-built battery. Then there is the cheap part, since it requires another power supply to make it work.

Can't I just run it from my 12v batteries? Not so handy when but on a boat I suppose.

 

[Aphers]

I suggest something like this, works well.

DC Power Supply Variable 3 Digital LED Display Adjustable Regulated Switching Power Supply Digital (30V 10A) : Amazon.co.uk: DIY & Tools

Shop DC Power Supply Variable 3 Digital LED Display Adjustable Regulated Switching Power Supply Digital (30V 10A). Free delivery on eligible orders of £20 or more.

www.amazon.co.uk

I probably got unlucky but that's essentially what I bought for doing my top balance when I built my 270Ah 4S pack. I actually had a replacement sent out after the first one died. Unless I cranked the voltage way up it never put out more than about 3A, nowhere near the advertised 10A. It was also very glitchy about actual output voltage, sometimes shooting up mid charge for no apparent reason. Oh and of course there was always a huge difference between the voltage measured at the battery terminals and the voltage on the display.

It kind of put me off using it again ... but maybe mine were duds... third time lucky?

 

[Just John]

I probably got unlucky but that's essentially what I bought for doing my top balance when I built my 270Ah 4S pack. I actually had a replacement sent out after the first one died. Unless I cranked the voltage way up it never put out more than about 3A, nowhere near the advertised 10A. It was also very glitchy about actual output voltage, sometimes shooting up mid charge for no apparent reason. Oh and of course there was always a huge difference between the voltage measured at the battery terminals and the voltage on the display.

It kind of put me off using it again ... but maybe mine were duds... third time lucky?

Why not correct the problem with real connection wires? Cheap power supplies come with cheap cables, replace them with real ones and get 9 amps easy. Do you still have the supply?

Guy did exactly that. 9.82 amps
https://diysolarforum.com/threads/top-balancing-how-to.15839/post-298311

From 3.24 amps.
https://diysolarforum.com/threads/top-balancing-how-to.15839/post-298247

Just by replacing the cable.

This explains how to set the power supply properly. Your explanation of symptoms......

Top Balancing LiFePo4 Cells using a low cost benchtop power supply.

To get the paper, click on the orange at the top of this page. This is a tutorial with detailed steps on how I top-balance my LiFePO4 Cells using a low-cost benchtop power supply. To get the tutorial, click on the orange "Download" button...

diysolarforum.com

 

[Aphers]

Why not correct the problem with real connection wires? Cheap power supplies come with cheap cables, replace them with real ones and get 9 amps easy. Do you still have the supply?

I've still got both of them. The first one just stopped putting out any volts/amps, both according to its own display and my own meter.

The replacement did better, but I don't use it unattended because sometimes it decides to increase the voltage for no apparent reason. It can also be next to impossible to adjust the output voltage to the required setting. Doing my top balance was pretty tedious!

It's possible that the seller had a dodgy batch of PSUs I suppose. I'm sure it's not just the weedy leads, I was using a meter to measure voltage at the battery end, and pretty much ignoring the unit's own display.

 

[Just John]

I've still got both of them. The first one just stopped putting out any volts/amps, both according to its own display and my own meter.

The replacement did better, but I don't use it unattended because sometimes it decides to increase the voltage for no apparent reason. It can also be next to impossible to adjust the output voltage to the required setting. Doing my top balance was pretty tedious!

It's possible that the seller had a dodgy batch of PSUs I suppose. I'm sure it's not just the weedy leads, I was using a meter to measure voltage at the battery end, and pretty much ignoring the unit's own display.

Always set voltage disconnected from the battery.
Then connect the battery and turn up the current.
Replace your leads. Sounds like your supply is working properly.
Follow my suggestions. The battery appears as a dead short and draws the power supply to it's voltage level with only the wire resistance stopping it.

With perfect leads, power supply will max out and display battery voltage. Don't change it. You will never have perfect leads, but what you have are garbage.

 

[Aphers]

Always set voltage disconnected from the battery.
Then connect the battery and turn up the current.
Replace your leads. Sounds like your supply is working properly.
Follow my suggestions.

Other than replacing the leads, that's exactly what I was doing. I can try different leads.