Question re Independent lithium battery solar installation to run 47 litre Freezer.

[kryg]

Background;

I have a portable Australian made fibreglass model 47 EvaKool fridge Freezer, it has given me excellent, reliable service.

I’m upgrading to a larger 60 litre EvaKool Fridge/Freezer and installing it fixed, replacing the troublesome engine driven eutectic system that has caused me no end of expense and trouble.

My plan is to use the 60 litre as a Fridge only, using my AGM house bank. And the 47 litre as a freezer only. In doing so I want to install an independent charging and system from the house bank.

As running both EvaKool fridge/freezer is taking too much power from the house bank.

All my house bank and starter systems are 12 volts powered with new 860-amp AGM batteries and 720 watt solar panels.

For this reason, I want to dip my toe into lithium battery field with either a 12- Or 24-volt power installation – by install an independent of My AGM house bank to ether 12 OR 24 volt lithium battery solar panel and solar controller just to power the 47 litre EvaKool as a freezer.

This will become a 3rd independent battery bank only to power this freezer, The Freezer power draw is 2 amp/Hr. At 32c.

If someone has Lithium installation experience, I need some of your guidance input to these Questions

1. What is the best 12 or 24 volts just for this independent setup?

2. What size lithium battery and BMS is reliable brand should I buy?

3. Should I have an independent BMS to the Battery if so which one?

4. Should the battery have its own BMS as one unit?

5. What Lithium battery solar controller brand make and model should be used?

6. Recommended Solar panel wattage size. Note* I plan to charge the lithium battery only by solar.

Many thanks, in advanced, for your inputs.

[StuM]

Originally Posted by kryg

For this reason, I want to dip my toe into lithium battery field with either a 12- Or 24-volt power installation –
This will become a 3rd independent battery bank only to power this freezer, The Freezer power draw is 2 amp/Hr. At 32c.

1. What is the best 12 or 24 volts just for this independent setup?

Is the fridge 12V or 24V ?

6. Recommended Solar panel wattage size. Note* I plan to charge the lithium battery only by solar.

I presume you mean it uses 2 amp hrs per hour (Ah/h) - amp/Hr is meaningless.

If so:
Is that 2Ah @ 12V or at 24V ? That will make quite a difference to your panel wattage requirement - about 600 Wh/day v 1200 Wh/day
If 12V, you probably need around 150W of panels , if 24V, 300W.

[kryg]

Thanks StuM Yes your guess is correct. It is 2 amp per hour. 12 volt will be the freezer can be run on either 12 or 24 volts.



I was thinking wire gauge size. Thinking it through as I should have done? 12 volt system will mean the solar panel size will be less of a footprint. Thanks.

Originally Posted by StuM

Is the fridge 12V or 24V ?

I presume you mean it uses 2 amp hrs per hour (Ah/h) - amp/Hr is meaningless.

If so:
Is that 2Ah @ 12V or at 24V ? That will make quite a difference to your panel wattage requirement - about 600 Wh/day v 1200 Wh/day
If 12V, you probably need around 150W of panels , if 24V, 300W.

[RaymondR]

Just started to participate in the lithium experiment. Learned so far:

Design your lithium battery as individual cells with a separate Battery Management System. I went with two 12 Volt batteries with inbuilt BMS and kept them in storage for a while before getting around to installing them. The first thing that happened was that they both went flat and one of them would not recover.

After a fairly hopeless session of email back and forward I decided that neither the vendor nor the local manufacturer's representative was going to be any assistance, for better or worse I owned the batteries and consequently decided that I would disassemble the dead one and explore it's innards.

I found that at some time the battery had been water damaged which probably had damaged the BMS circuit board and that two of the eight cells were dead.

On further investigation I found that there was a leak from the potable water refill deck fitting, which is situated above the battery locker, and that because the pole posts on the battery are not sealed where they go through the top cover water had collected on top of the battery and slowly leaked into the case flooding the circuit board.

Had the installation been constituted from individual cells and a stand alone BMS I could have replaced only the two dead cells and the BMS and salvaged the six relatively new ones rather than throw them away.

My original intention had been to use two 12V lithium batteries in series to power the fridge with 24V however since having this expensive lesson I have decided to proceed with just 12V which appears to be working OK on the portable fridge I am using whilst I rebuild the inbuilt one.

I have also decided that even without bathing it in rain water the electronics in the BMS is probably the more delicate part of the lithium battery system and that being able to replace it without throwing away perfectly good cells permanently packaged in with the BMS could, in some circumstances, be a good design feature.

[kryg]

Hi Raymond,



Thanks for the interesting but expensive lessons you have shared.

The main issue is what BMS to use, as it seems that BMS black box is a mystery? As I understand it, not all BMS are adaptable to be programmed fit for purpose?

Originally Posted by RaymondR

Just started to participate in the lithium experiment. Learned so far:

Design your lithium battery as individual cells with a separate Battery Management System. I went with two 12 Volt batteries with inbuilt BMS and kept them in storage for a while before getting around to installing them. The first thing that happened was that they both went flat and one of them would not recover.

After a fairly hopeless session of email back and forward I decided that neither the vendor nor the local manufacturer's representative was going to be any assistance, for better or worse I owned the batteries and consequently decided that I would disassemble the dead one and explore it's innards.

I found that at some time the battery had been water damaged which probably had damaged the BMS circuit board and that two of the eight cells were dead.

On further investigation I found that there was a leak from the potable water refill deck fitting, which is situated above the battery locker, and that because the pole posts on the battery are not sealed where they go through the top cover water had collected on top of the battery and slowly leaked into the case flooding the circuit board.

Had the installation been constituted from individual cells and a stand alone BMS I could have replaced only the two dead cells and the BMS and salvaged the six relatively new ones rather than throw them away.

My original intention had been to use two 12V lithium batteries in series to power the fridge with 24V however since having this expensive lesson I have decided to proceed with just 12V which appears to be working OK on the portable fridge I am using whilst I rebuild the inbuilt one.

I have also decided that even without bathing it in rain water the electronics in the BMS is probably the more delicate part of the lithium battery system and that being able to replace it without throwing away perfectly good cells permanently packaged in with the BMS could, in some circumstances, be a good design feature.

[StuM]

Originally Posted by kryg

Thanks StuM Yes your guess is correct. It is 2 amp per hour. 12 volt will be the freezer can be run on either 12 or 24 volts.

Aaaah! No it is NOT 2 amps per hour. That's essentially meaningless.

Please read https://www.cruisersforum.com/forums...ml#post1933764
You probably mean 2 amp hours per hour.
And if it is 2 at 12V then a 150W panel should do it.

[kryg]

Hi StuM, Thanks, for the lesson link, interesting read one learns something every day. Attached is EVAKOOL power consumption table, which I used in my original Cruiser form text - As you will note from the attachment they use the following rated term at A/Hr. This does not mean they are wrong or right. I don't know, and I don't much care, as I do understand the meaning of their published table so do I dear say thousands of EVAKOOL owners would understand their product power consumption as a layman. I'm not nitpicking I'm trying to solve a real subject outside confusing terminologies. Still, for my reference, I cut and pasted your helpful lesson on the subject.

Originally Posted by StuM

Aaaah! No it is NOT 2 amps per hour. That's essentially meaningless.

Please read https://www.cruisersforum.com/forums...ml#post1933764
You probably mean 2 amp hours per hour.
And if it is 2 at 12V then a 150W panel should do it.

[StuM]

Originally Posted by kryg

Hi StuM, Thanks, for the lesson link, interesting read one learns something every day. Attached is EVAKOOL power consumption table, which I used in my original Cruiser form text - As you will note from the attachment they use the following rated term at A/Hr. This does not mean they are wrong or right.

It means they are wrong
A/Hr (amps per hour) is meaningless since amps are a measure of power i.e. a rate of consumption, not a unit of energy consumed.


Unfortunately, they are just one of many companies using documentation writers who are not technical people and who make similar errors. I'm sure that in many cases, it makes their actual engineering staff cringe if they read the user manuals.
The problem is that is more than one interpetation of such a table depending on how you interpret the incorrectly stated A/Hr and the actual electricity usage is very different for those interpretations.
If you take A/Hr to mean amp hours (Ah) then they are apparently talking about consumption per day (average usage...meaured over a 24 hour period).

If you take A/Hr to mean amp hours per hour (Ah/h) that is 24 times as much energy used per day.


Sure, in this situation, we should recognise that 1.0-1.5 Amp hours per day is obviously far to small a figure and they mean Ah per hour but in other situations and to many people, it would not be so apparent.

[StuM]

Actually, there is a more fundamental problem with that table. The manual says:
The refrigerator can be powered by a multi-voltage system utilizing either 12/24 Volts or 240 Volts .

Since the table states amps with no voltage, than means that the daily energy consumption could be:
For 2 A/Hr:

2A x 12V x 24h = 576Wh
2A x 24V x 24h = 1152Wh
2A x 240V x 24h =11520Wh
2Ah x 12V = 24Wh
2Ah x 24V = 48Wh
2Ah x 240 V = 480Wh


SO - what is the actual daily energy required

[donradcliffe]

Time to get the discussion back on the rails.

If the EVAKOOL uses 2 amps at 12v, it uses 2x24 = 48 amp hours per day at 12v. In terms of watts, that is 48x12 = 576 watt hours per day. Consider a 100 amp hour lithium drop in battery. Drop in should mean it has its own internal BMS to protect the cells from undercharging, overcharging, over current, and high/low temperature, but don't trust the Chinese. The battery theoretically will power the EVAKOOL for 100/48 = 2 days. In reality you can only get 80 useable amp hours out of a 100 amp hour battery, so it should be good for 80x24/48 = 40 hours with NO solar. Given the fact that you only have to store energy for the overnight hours, a 100 amp hour drop in LiFe battery should be overkill for your needs, and should last for several 1000 daily cycles.

Now lets talk about replacing the 576 watt hours each day with solar. Firstly, like the battery, a 200 watt solar panel doesn't ever put out 200 watts of power. Let's say that it really puts out 160 watts on a summer's day when the sun is overhead and nothing is shading the panel. Then you need 576/160 = 3.6 hours of good sunlight. During the summer months, you may get an average of 5 hours of good sunlight per day, so a 200 watt solar system should work MOST of the time.

Not being Australian, keeping the beer cold is not mission critical, so I might stop there. However, there will be cloudy days, and it would be better to have a way to tie the LiFe battery to your boat's other charging systems. The KISS way would be to have a switch that jumpered the LiFe battery to the AGM battery that you could close WHEN YOU ARE RUNNING THE ENGINE/GENSET/DOCK POWER. The downside to the jumper switch is that you need to open the switch when (1) the LiFe battery is fully charged and when (2) you have stopped the ENGINE/GENSET/DOCK POWER. To my knowledge, no one has come out with a smart automatic switch, which is a pity because I could make an Arduino based one in a week or two.

There are some other real world inefficiencies, but I have added some windage into the system for them.

[sailingchiro]

I just did this. Semi-successfully. This system only shares common ground with boat. It is completely independent of house ac and dc. While I can charge house bank from solar/refrigeration bank only in an emergency it is completely independent.
Battery size. Enough to run all refrigeration for 3-5 days without any sunlight. Mine are 400amp/hr at 24 volts. Getting ready to add 800 amp/hr 12 volts on house bank
Solar size: Enough to charge batteries to capacity in one 7 hour day of sunlight
Voltage: 12v, easier to find inverter but wire size is bigger, more current=more loss
24v, smaller wire, more efficient, harder to find inverter,
BMS= I used Daly but get large enough in current to run inverter such as 150-200 amps. If you try to run an inverter at 2000 watts 12 volts will need 166 amp BMS, 24 volts will need 83 amps.
The BMS will want you to run everything through it. I hooked my inverter directly to the batteries and have run into problems.
Controllers, I have three in order to expand solar but also to limit shading. I split my panels to have shading only affect one controller. I used Epever.
I have many breakers and switches, I can disconnect controllers, batteries, inverter. And the breakers are all appropriately sized for the wire that it controls. Controllers hate having solar voltage coming in and no battery voltage. It is a learning process but so far I am very happy. My old lead acid batteries are hard to charge and fast to lose power.

[hzcruiser]

I'm not sure why you want a complete second set of batteries, BMS, charge controller (CC) and then more solar panels just for the freezer?
This increases the complexity of your setup, especially if you also run the LFP system at 24V.
You'll likely end up with regular imbalances, as in a situation where one set of batts might have enough power left to run the consumer on the other side but you cannot get the power there!
I would keep everything at 12V, since that's what you already have, and have both batt banks, AGM and LFP, charged by your existing charge controller, then automatically disconnect the LFPs once they're full (via latching relays) and keep charging the AGM until they're full using their absorption profile. In other words, the CC stays at the AGM profile.